libs/uvl: update inline documentation
[project/luci.git] / libs / uvl / luasrc / uvl.lua
index 35e903f..dd8058f 100644 (file)
@@ -8,486 +8,828 @@ Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
-        http://www.apache.org/licenses/LICENSE-2.0
+               http://www.apache.org/licenses/LICENSE-2.0
 
 $Id$
 
 ]]--
 
-module( "luci.uvl", package.seeall )
 
-require("luci.fs")
-require("luci.util")
-require("luci.model.uci")
-require("luci.uvl.datatypes")
---require("luci.uvl.validation")
-require("luci.uvl.dependencies")
+--- UVL - UCI Validation Layer
+-- @class      module
+-- @cstyle     instance
 
-TYPE_SECTION  = 0x01
-TYPE_VARIABLE = 0x02
-TYPE_ENUM     = 0x03
+local fs = require "luci.fs"
+local uci = require "luci.model.uci"
+local util = require "luci.util"
+local table = require "table"
+local string = require "string"
 
+local require, pcall, ipairs, pairs = require, pcall, ipairs, pairs
+local type, error, tonumber, tostring = type, error, tonumber, tostring
+local unpack, loadfile = unpack, loadfile
 
-local default_schemedir = "/etc/scheme"
+module "luci.uvl"
 
-local function _assert( condition, fmt, ... )
-       if not condition then
-               return assert( nil, string.format( fmt, ... ) )
-       else
-               return condition
-       end
-end
+local ERR = require "luci.uvl.errors"
+local datatypes = require "luci.uvl.datatypes"
+local validation = require "luci.uvl.validation"
+local dependencies = require "luci.uvl.dependencies"
+
+local TYPE_SCHEME   = 0x00
+local TYPE_CONFIG   = 0x01
+local TYPE_SECTION  = 0x02
+local TYPE_OPTION   = 0x03
+local TYPE_ENUM     = 0x04
+
+--- Boolean; default true;
+-- treat sections found in config but not in scheme as error
+STRICT_UNKNOWN_SECTIONS    = true
+
+--- Boolean; default true;
+-- treat options found in config but not in scheme as error
+STRICT_UNKNOWN_OPTIONS     = true
+
+--- Boolean; default true;
+-- treat failed external validators as error
+STRICT_EXTERNAL_VALIDATORS = true
+
+--- Boolean; default true;
+-- treat list values stored as options like errors
+STRICT_LIST_TYPE           = true
+
+
+local default_schemedir = "/lib/uci/schema"
+local default_savedir = "/tmp/.uvl"
 
-UVL = luci.util.class()
 
-function UVL.__init__( self, schemedir )
+--- Object constructor
+-- @class                      function
+-- @name                       UVL
+-- @param schemedir    Path to the scheme directory (optional)
+-- @param configdir    Override config directory (optional)
+-- @return                     Instance object
+UVL = util.class()
 
+function UVL.__init__( self, schemedir, configdir )
        self.schemedir  = schemedir or default_schemedir
+       self.configdir  = configdir
        self.packages   = { }
        self.beenthere  = { }
-       self.uci                = luci.model.uci
-       self.datatypes  = luci.uvl.datatypes
+       self.depseen    = { }
+       self.uci                = uci
+       self.err                = ERR
+       self.dep                = dependencies
+       self.datatypes  = datatypes
 end
 
 
-function UVL._scheme_section( self, uci, c, s )
-       if self.packages[c] and uci[s] then
-               return self.packages[c].sections[uci[s][".type"]]
+--- Parse given scheme and return the scheme tree.
+-- @param scheme       Name of the scheme to parse
+-- @return                     Table containing the parsed scheme or nil on error
+-- @return                     String containing the reason for errors (if any)
+function UVL.get_scheme( self, scheme )
+       if not self.packages[scheme] then
+               local ok, err = self:read_scheme( scheme )
+               if not ok then
+                       return nil, err
+               end
        end
+       return self.packages[scheme], nil
 end
 
-function UVL._scheme_option( self, uci, c, s, o )
-       if self.packages[c] and uci[s] and uci[s][o] then
-               return self.packages[c].variables[uci[s][".type"]][o]
-       elseif self.packages[c] and self.packages[c].variables[s] then
-               return self.packages[c].variables[s][o]
+--- Validate given configuration, section or option.
+-- @param config       Name of the configuration to validate
+-- @param section      Name of the section to validate (optional)
+-- @param option       Name of the option to validate (optional)
+-- @return                     Boolean indicating whether the given config validates
+-- @return                     String containing the reason for errors (if any)
+function UVL.validate( self, config, section, option )
+       if config and section and option then
+               return self:validate_option( config, section, option )
+       elseif config and section then
+               return self:validate_section( config, section )
+       elseif config then
+               return self:validate_config( config )
        end
 end
 
-function UVL._keys( self, tbl )
-       local keys = { }
-       if tbl then
-               for k, _ in luci.util.kspairs(tbl) do
-                       table.insert( keys, k )
+--- Validate given configuration.
+-- @param cfg  Name of the configuration to validate
+-- @return                     Boolean indicating whether the given config validates
+-- @return                     String containing the reason for errors (if any)
+function UVL.validate_config( self, cfg, uci )
+
+       if not self.packages[cfg] then
+               local ok, err = self:read_scheme(cfg)
+               if not ok then
+                       return false, err
                end
        end
-       return keys
-end
 
+       local co = config( self, uci or cfg, uci and cfg )
+       local sc = { }
 
---- Validate given configuration.
--- @param config       Name of the configuration to validate
--- @param scheme       Scheme to validate against (optional)
--- @return                     Boolean indicating weather the given config validates
--- @return                     String containing the reason for errors (if any)
-function UVL.validate( self, config )
+       self.beenthere = { }
+       self.depseen   = { }
 
-       self.uci.set_confdir( self.uci.confdir_default )
-       self.uci.load( config )
-
-       local co = self.uci.get_all( config )
+       if not co:config() then
+               return false, co:errors()
+       end
 
        local function _uci_foreach( type, func )
-               for k, v in pairs(co) do
-                       if co[k]['.type'] == type then
-                               func( k, v )
+               for k, v in pairs(co:config()) do
+                       if v['.type'] == type then
+                               sc[type] = sc[type] + 1
+                               local ok, err = func( k, v )
+                               if not ok then co:error(err) end
                        end
                end
        end
 
-       luci.util.dumptable(co)
-
-
-
-       for k, v in pairs( self.packages[config].sections ) do
+       for k, v in pairs( self.packages[cfg].sections ) do
+               sc[k] = 0
                _uci_foreach( k,
                        function(s)
-                               local ok, err = self:validate_section( config, s, co )
-
-                               if not ok then
-                                       return ok, err
-                               end
+                               return self:_validate_section( co:section(s) )
                        end
                )
        end
 
-       return true, nil
-end
-
---- Validate given section of given configuration.
--- @param config       Name of the configuration to validate
--- @param section      Key of the section to validate
--- @param scheme       Scheme to validate against
--- @return                     Boolean indicating weather the given config validates
--- @return                     String containing the reason for errors (if any)
-function UVL.validate_section( self, config, section, co, nodeps )
-
-       if not co then
-               self.uci.set_confdir( self.uci.confdir_default )
-               self.uci.load( config )
-               co = uci.get_all( config )
+       if STRICT_UNKNOWN_SECTIONS then
+               for k, v in pairs(co:config()) do
+                       local so = co:section(k)
+                       if not self.beenthere[so:cid()] then
+                               co:error(ERR.SECT_UNKNOWN(so))
+                       end
+               end
        end
 
-       local cs     = co[section]
-       local scheme = self:_scheme_section( co, config, section )
-
-       if cs then
-               --luci.util.dumptable(cs)
+       for _, k in ipairs(util.keys(sc)) do
+               local so = co:section(k)
+               if so:scheme('required') and sc[k] == 0 then
+                       co:error(ERR.SECT_REQUIRED(so))
+               elseif so:scheme('unique') and sc[k] > 1 then
+                       co:error(ERR.SECT_UNIQUE(so))
+               end
+       end
 
+       return co:ok(), co:errors()
+end
 
-               for k, v in pairs(self.packages[config].variables[cs[".type"]]) do
-                       if k:sub(1,1) ~= "." then
-                               local ok, err = self:validate_option( config, section, k, co, false, cs[".type"] )
+--- Validate given config section.
+-- @param config       Name of the configuration to validate
+-- @param section      Name of the section to validate
+-- @return                     Boolean indicating whether the given config validates
+-- @return                     String containing the reason for errors (if any)
+function UVL.validate_section( self, cfg, section, uci )
 
-                               if not ok then
-                                       print("ERR", err)
-                                       return ok, err
-                               end
-                       end
+       if not self.packages[cfg] then
+               local ok, err = self:read_scheme( cfg )
+               if not ok then
+                       return false, err
                end
+       end
 
-               --local dep_ok = nodeps or luci.uvl.dependencies.check_dependency( self, co, config, section )
-               --print( "DEP: ", dep_ok )
+       local co = config( self, uci or cfg, uci and cfg )
+       local so = co:section( section )
 
-               --print( "Validate section: ", config .. '.' .. section, nodeps and '(without depencies)' or '' )
+       self.beenthere = { }
+       self.depseen   = { }
 
-               local ok, err = luci.uvl.dependencies.check_dependency(
-                       self, co, config, section, nil, true, cs[".type"]
-               )
+       if not co:config() then
+               return false, co:errors()
+       end
 
-               if ok then
-                       --print("Validated section!\n\n")
-                       return true
-               else
-                       print("ERR", "All possible dependencies failed. (Last error was: " .. err .. ")")
-                       return false, "All possible dependencies failed"
-               end
+       if so:config() then
+               return self:_validate_section( so )
        else
-               print( "Error, scheme section '" .. section .. "' not found in data" )
+               return false, ERR.SECT_NOTFOUND(so)
        end
-
-       return true, nil
 end
 
---- Validate given option within section of given configuration.
+--- Validate given config option.
 -- @param config       Name of the configuration to validate
--- @param section      Key of the section to validate
+-- @param section      Name of the section to validate
 -- @param option       Name of the option to validate
--- @param scheme       Scheme to validate against
--- @return                     Boolean indicating weather the given config validates
+-- @return                     Boolean indicating whether the given config validates
 -- @return                     String containing the reason for errors (if any)
-function UVL.validate_option( self, config, section, option, co, nodeps, section2 )
+function UVL.validate_option( self, cfg, section, option, uci )
 
-       if not co then
-               self.uci.set_confdir( self.uci.confdir_default )
-               self.uci.load( config )
-               co = uci.get_all( config )
+       if not self.packages[cfg] then
+               local ok, err = self:read_scheme( cfg )
+               if not ok then
+                       return false, err
+               end
        end
 
-       local cs = co[section]
-       local sv = self:_scheme_option( co, config, section, option ) or
-               self:_scheme_option( co, config, section2, option )
+       local co = config( self, uci or cfg, uci and cfg )
+       local so = co:section( section )
+       local oo = so:option( option )
 
-       --print("VOPT", config, section, option )
-
-       if not sv then
-               return false, "Requested option '" ..
-                       config .. '.' .. ( section or section2 ) .. '.' .. option ..
-                       "' not found in scheme"
+       if not co:config() then
+               return false, co:errors()
        end
 
-       if sv.required and not cs[option] then
-               return false, "Mandatory variable '" ..
-                       config .. '.' .. section .. '.' .. option ..
-                       "' doesn't have a value"
+       if so:config() and oo:config() then
+               return self:_validate_option( oo )
+       else
+               return false, ERR.OPT_NOTFOUND(oo)
        end
+end
+
+
+function UVL._validate_section( self, section )
 
-       if sv.type == "enum" and cs[option] then
-               if not sv.values or not sv.values[cs[option]] then
-                       return false, "Value '" .. ( cs[option] or '<nil>' ) .. "' of given option '" ..
-                               config .. "." .. section .. "." .. option ..
-                               "' is not defined in enum { " ..
-                               table.concat(self:_keys(sv.values),", ") .. " }"
+       self.beenthere[section:cid()] = true
+
+       if section:config() then
+               if section:scheme('named') == true and
+                  section:config('.anonymous') == true
+               then
+                       return false, ERR.SECT_NAMED(section)
                end
-       end
 
-       if sv.datatype and cs[option] then
-               if self.datatypes[sv.datatype] then
-                       if not self.datatypes[sv.datatype]( cs[option] ) then
-                               return false, "Value '" .. ( cs[option] or '<nil>' ) .. "' of given option '" ..
-                                       config .. "." .. ( section or section2 ) .. "." .. option ..
-                                       "' doesn't validate as datatype '" .. sv.datatype .. "'"
+               for _, v in ipairs(section:variables()) do
+                       local ok, err = self:_validate_option( v )
+                       if not ok and (
+                               v:scheme('required') or v:scheme('type') == "enum" or (
+                                       not err:is(ERR.ERR_DEP_NOTEQUAL) and
+                                       not err:is(ERR.ERR_DEP_NOVALUE)
+                               )
+                       ) then
+                               section:error(err)
                        end
-               else
-                       return false, "Unknown datatype '" .. sv.datatype .. "' encountered"
                end
+
+               local ok, err = dependencies.check( self, section )
+               if not ok then
+                       section:error(err)
+               end
+       else
+               return false, ERR.SECT_NOTFOUND(section)
        end
 
-       if not nodeps then
-               return luci.uvl.dependencies.check_dependency(
-                       self, co, config, section, option, nil, section2
-               )
+       if STRICT_UNKNOWN_OPTIONS and not section:scheme('dynamic') then
+               for k, v in pairs(section:config()) do
+                       local oo = section:option(k)
+                       if k:sub(1,1) ~= "." and not self.beenthere[oo:cid()] then
+                               section:error(ERR.OPT_UNKNOWN(oo))
+                       end
+               end
        end
 
-       return true, nil
+       return section:ok(), section:errors()
 end
 
---- Find all parts of given scheme and construct validation tree
--- @param scheme       Name of the scheme to parse
--- @return                     Parsed scheme
-function UVL.read_scheme( self, scheme )
-       local schemes = { }
+function UVL._validate_option( self, option, nodeps )
 
-       for i, file in ipairs( luci.fs.glob(self.schemedir .. '/*/' .. scheme) ) do
-               _assert( luci.fs.access(file), "Can't access file '%s'", file )
+       self.beenthere[option:cid()] = true
 
-               self.uci.set_confdir( luci.fs.dirname(file) )
-               self.uci.load( luci.fs.basename(file) )
+       if not option:scheme() and not option:parent():scheme('dynamic') then
+               if STRICT_UNKNOWN_OPTIONS then
+                       return false, option:error(ERR.OPT_UNKNOWN(option))
+               else
+                       return true
+               end
 
-               table.insert( schemes, self.uci.get_all( luci.fs.basename(file) ) )
-       end
+       elseif option:scheme() then
+               if not nodeps then
+                       local ok, err = dependencies.check( self, option )
+                       if not ok then
+                               if not err:is_all(
+                                       ERR.ERR_OPT_REQUIRED,
+                                       ERR.ERR_DEP_NOTEQUAL,
+                                       ERR.ERR_DEP_NOVALUE
+                               ) then
+                                       option:error(err)
+                                       return false, option:errors()
+                               else
+                                       return true
+                               end
+                       end
+               end
 
-       return self:_read_scheme_parts( scheme, schemes )
-end
+               if option:scheme('required') and not option:value() then
+                       return false, option:error(ERR.OPT_REQUIRED(option))
+
+               elseif option:value() then
+                       local val = option:value()
+
+                       if option:scheme('type') == "reference" or
+                          option:scheme('type') == "enum"
+                       then
+                               local scheme_values = option:scheme('values') or { }
+                               local config_values = ( type(val) == "table" and val or { val } )
+                               for _, v in ipairs(config_values) do
+                                       if not scheme_values[v] then
+                                               return false, option:error( ERR.OPT_BADVALUE(
+                                                       option, { v, util.serialize_data(
+                                                               util.keys(scheme_values)
+                                                       ) }
+                                               ) )
+                                       end
+                               end
+                       elseif option:scheme('type') == "list" then
+                               if type(val) ~= "table" and STRICT_LIST_TYPE then
+                                       return false, option:error(ERR.OPT_NOTLIST(option))
+                               end
+                       end
 
--- Process all given parts and construct validation tree
-function UVL._read_scheme_parts( self, scheme, schemes )
+                       if option:scheme('datatype') then
+                               local dt = option:scheme('datatype')
 
-       -- helper function to construct identifiers for given elements
-       local function _id( c, t )
-               if c == TYPE_SECTION then
-                       return string.format(
-                               "section '%s.%s'",
-                                       scheme, t.name or '?' )
-               elseif c == TYPE_VARIABLE then
-                       return string.format(
-                               "variable '%s.%s.%s'",
-                                       scheme, t.section or '?.?', t.name or '?' )
-               elseif c == TYPE_ENUM then
-                       return string.format(
-                               "enum '%s.%s.%s'",
-                                       scheme, t.variable or '?.?.?', t.value or '?' )
+                               if self.datatypes[dt] then
+                                       val = ( type(val) == "table" and val or { val } )
+                                       for i, v in ipairs(val) do
+                                               if not self.datatypes[dt]( v ) then
+                                                       return false, option:error(
+                                                               ERR.OPT_INVVALUE(option, { v, dt })
+                                                       )
+                                               end
+                                       end
+                               else
+                                       return false, option:error(ERR.OPT_DATATYPE(option, dt))
+                               end
+                       end
+
+                       val = ( type(val) == "table" and val or { val } )
+                       for _, v in ipairs(val) do
+                               if option:scheme('minlength') then
+                                       if #v < option:scheme('minlength') then
+                                               return false, option:error(ERR.OPT_RANGE(option))
+                                       end
+                               end
+
+                               if option:scheme('maxlength') then
+                                       if #v > option:scheme('maxlength') then
+                                               return false, option:error(ERR.OPT_RANGE(option))
+                                       end
+                               end
+
+                               local w = tonumber(v)
+
+                               if option:scheme('minimum') then
+                                       if not w or w < option:scheme('minimum') then
+                                               return false, option:error(ERR.OPT_RANGE(option))
+                                       end
+                               end
+
+                               if option:scheme('maximum') then
+                                       if not w or w > option:scheme('maximum') then
+                                               return false, option:error(ERR.OPT_RANGE(option))
+                                       end
+                               end
+                       end
                end
-       end
 
-       -- helper function to check for required fields
-       local function _req( c, t, r )
-               for i, v in ipairs(r) do
-                       _assert( t[v], "Missing required field '%s' in %s", v, _id(c, t) )
+               local ok, err = validation.check( self, option )
+               if not ok and STRICT_EXTERNAL_VALIDATORS then
+                       return false, option:error(err)
                end
        end
 
-       -- helper function to validate references
-       local function _ref( c, t )
-               local k
-               if c == TYPE_SECTION then
-                       k = "package"
-               elseif c == TYPE_VARIABLE then
-                       k = "section"
-               elseif c == TYPE_ENUM then
-                       k = "variable"
-               end
+       return option:ok(), option:errors()
+end
 
-               local r = luci.util.split( t[k], "." )
-               r[1] = ( #r[1] > 0 and r[1] or scheme )
+--- Find all parts of given scheme and construct validation tree.
+-- This is normally done on demand, so you don't have to call this function
+-- by yourself.
+-- @param shm  Name of the scheme to parse
+-- @param alias                Create an alias for the loaded scheme
+function UVL.read_scheme( self, shm, alias )
 
-               _assert( #r == c, "Malformed %s reference in %s", k, _id(c, t) )
+       local so = scheme( self, shm )
+       local bc = "%s/bytecode/%s.lua" %{ self.schemedir, shm }
 
-               return r
-       end
+       if not fs.access(bc) then
+               local files = fs.glob(self.schemedir .. '/*/' .. shm)
 
-       -- Step 1: get all sections
-       for i, conf in ipairs( schemes ) do
-               for k, v in pairs( conf ) do
-                       if v['.type'] == 'section' then
+               if files then
+                       local ok, err
+                       for i, file in ipairs( files ) do
+                               if not fs.access(file) then
+                                       return false, so:error(ERR.SME_READ(so,file))
+                               end
 
-                               _req( TYPE_SECTION, v, { "name", "package" } )
+                               local uci = uci.cursor( fs.dirname(file), default_savedir )
 
-                               local r = _ref( TYPE_SECTION, v )
+                               local sname = fs.basename(file)
+                               local sd, err = uci:load( sname )
 
-                               self.packages[r[1]] =
-                                       self.packages[r[1]] or {
-                                               ["sections"]  = { };
-                                               ["variables"] = { };
-                                       }
+                               if not sd then
+                                       return false, ERR.UCILOAD(so, err)
+                               end
 
-                               local p = self.packages[r[1]]
-                                         p.sections[v.name]  = p.sections[v.name]  or { }
-                                         p.variables[v.name] = p.variables[v.name] or { }
+                               ok, err = pcall(function()
+                                       uci:foreach(sname, "package", function(s)
+                                               self:_parse_package(so, s[".name"], s)
+                                       end)
+                                       uci:foreach(sname, "section", function(s)
+                                               self:_parse_section(so, s[".name"], s)
+                                       end)
+                                       uci:foreach(sname, "variable", function(s)
+                                               self:_parse_var(so, s[".name"], s)
+                                       end)
+                                       uci:foreach(sname, "enum", function(s)
+                                               self:_parse_enum(so, s[".name"], s)
+                                       end)
+
+                               end)
+                       end
 
-                               local s = p.sections[v.name]
+                       if ok and alias then self.packages[alias] = self.packages[shm] end
+                       return ok and self, err
+               else
+                       return false, so:error(ERR.SME_FIND(so, self.schemedir))
+               end
+       else
+               local sc = loadfile(bc)
+               if sc then
+                       self.packages[shm] = sc()
+                       return true
+               else
+                       return false, so:error(ERR.SME_READ(so,bc))
+               end
+       end
+end
 
-                               for k, v2 in pairs(v) do
-                                       if k ~= "name" and k ~= "package" and k:sub(1,1) ~= "." then
-                                               if k:match("^depends") then
-                                                       s["depends"] = _assert(
-                                                               self:_read_depency( v2, s["depends"] ),
-                                                               "Section '%s' in scheme '%s' has malformed " ..
-                                                               "depency specification in '%s'",
-                                                               v.name or '<nil>', scheme or '<nil>', k
-                                                       )
-                                               else
-                                                       s[k] = v2
-                                               end
-                                       end
-                               end
+-- helper function to check for required fields
+local function _req( t, n, c, r )
+       for i, v in ipairs(r) do
+               if not c[v] then
+                       local p, o = scheme:sid(), nil
+
+                       if t == TYPE_SECTION then
+                               o = section( scheme, nil, p, n )
+                       elseif t == TYPE_OPTION then
+                               o = option( scheme, nil, p, '(nil)', n )
+                       elseif t == TYPE_ENUM then
+                               o = enum( scheme, nil, p, '(nil)', '(nil)', n )
                        end
+
+                       return false, ERR.SME_REQFLD(o,v)
                end
        end
+       return true
+end
 
-       -- Step 2: get all variables
-       for i, conf in ipairs( schemes ) do
-               for k, v in pairs( conf ) do
-                       if v['.type'] == "variable" then
+-- helper function to validate references
+local function _ref( c, t )
+       local r, k, n = {}
+       if c == TYPE_SECTION then
+               k = "package"
+               n = 1
+       elseif c == TYPE_OPTION then
+               k = "section"
+               n = 2
+       elseif c == TYPE_ENUM then
+               k = "variable"
+               n = 3
+       end
 
-                               _req( TYPE_VARIABLE, v, { "name", "section" } )
+       for o in t[k]:gmatch("[^.]+") do
+               r[#r+1] = o
+       end
+       r[1] = ( #r[1] > 0 and r[1] or scheme:sid() )
 
-                               local r = _ref( TYPE_VARIABLE, v )
+       if #r ~= n then
+               return false, ERR.SME_BADREF(scheme, k)
+       end
 
-                               local p = _assert( self.packages[r[1]],
-                                       "Variable '%s' in scheme '%s' references unknown package '%s'",
-                                       v.name, scheme, r[1] )
+       return r
+end
 
-                               local s = _assert( p.variables[r[2]],
-                                       "Variable '%s' in scheme '%s' references unknown section '%s'",
-                                       v.name, scheme, r[2] )
+-- helper function to read bools
+local function _bool( v )
+       return ( v == "true" or v == "yes" or v == "on" or v == "1" )
+end
 
-                               s[v.name] = s[v.name] or { }
+-- Step 0: get package meta information
+function UVL._parse_package(self, scheme, k, v)
+       local sid = scheme:sid()
+       local pkg = self.packages[sid] or {
+               ["name"]      = sid;
+               ["sections"]  = { };
+               ["variables"] = { };
+       }
 
-                               local t = s[v.name]
+       pkg.title = v.title
+       pkg.description = v.description
 
-                               for k, v in pairs(v) do
-                                       if k ~= "name" and k ~= "section" and k:sub(1,1) ~= "." then
-                                               if k:match("^depends") then
-                                                       t["depends"] = _assert(
-                                                               self:_read_depency( v, t["depends"] ),
-                                                               "Variable '%s' in scheme '%s' has malformed " ..
-                                                               "depency specification in '%s'",
-                                                               v.name, scheme, k
-                                                       )
-                                               elseif k:match("^validator") then
-                                                       t["validators"] = _assert(
-                                                               self:_read_validator( v, t["validators"] ),
-                                                               "Variable '%s' in scheme '%s' has malformed " ..
-                                                               "validator specification in '%s'",
-                                                               v.name, scheme, k
-                                                       )
-                                               else
-                                                       t[k] = v
-                                               end
-                                       end
+       self.packages[sid] = pkg
+end
+
+-- Step 1: get all sections
+function UVL._parse_section(self, scheme, k, v)
+       local ok, err = _req( TYPE_SECTION, k, v, { "name", "package" } )
+       if err then error(scheme:error(err)) end
+
+       local r, err = _ref( TYPE_SECTION, v )
+       if err then error(scheme:error(err)) end
+
+       local p = self.packages[r[1]] or {
+               ["name"]      = r[1];
+               ["sections"]  = { };
+               ["variables"] = { };
+       }
+       p.sections[v.name]  = p.sections[v.name]  or { }
+       p.variables[v.name] = p.variables[v.name] or { }
+       self.packages[r[1]] = p
+
+       local s  = p.sections[v.name]
+       local so = scheme:section(v.name)
+
+       for k, v2 in pairs(v) do
+               if k ~= "name" and k ~= "package" and k:sub(1,1) ~= "." then
+                       if k == "depends" then
+                               s.depends = self:_read_dependency( v2, s.depends )
+                               if not s.depends then
+                                       return false, scheme:error(
+                                               ERR.SME_BADDEP(so, util.serialize_data(s.depends))
+                                       )
                                end
+                       elseif k == "dynamic" or k == "unique" or
+                              k == "required" or k == "named"
+                       then
+                               s[k] = _bool(v2)
+                       else
+                               s[k] = v2
                        end
                end
        end
 
-       -- Step 3: get all enums
-       for i, conf in ipairs( schemes ) do
-               for k, v in pairs( conf ) do
-                       if v['.type'] == "enum" then
+       s.dynamic  = s.dynamic  or false
+       s.unique   = s.unique   or false
+       s.required = s.required or false
+       s.named    = s.named    or false
+end
 
-                               _req( TYPE_ENUM, v, { "value", "variable" } )
+-- Step 2: get all variables
+function UVL._parse_var(self, scheme, k, v)
+       local ok, err = _req( TYPE_OPTION, k, v, { "name", "section" } )
+       if err then error(scheme:error(err)) end
 
-                               local r = _ref( TYPE_ENUM, v )
+       local r, err = _ref( TYPE_OPTION, v )
+       if err then error(scheme:error(err)) end
 
-                               local p = _assert( self.packages[r[1]],
-                                       "Enum '%s' in scheme '%s' references unknown package '%s'",
-                                       v.value, scheme, r[1] )
+       local p = self.packages[r[1]]
+       if not p then
+               error(scheme:error(
+                       ERR.SME_VBADPACK({scheme:sid(), '', v.name}, r[1])
+               ))
+       end
 
-                               local s = _assert( p.variables[r[2]],
-                                       "Enum '%s' in scheme '%s' references unknown section '%s'",
-                                       v.value, scheme, r[2] )
+       local s = p.variables[r[2]]
+       if not s then
+               error(scheme:error(
+                       ERR.SME_VBADSECT({scheme:sid(), '', v.name}, r[2])
+               ))
+       end
 
-                               local t = _assert( s[r[3]],
-                                       "Enum '%s' in scheme '%s', section '%s' references " ..
-                                       "unknown variable '%s'",
-                                       v.value, scheme, r[2], r[3] )
+       s[v.name] = s[v.name] or { }
 
-                               _assert( t.type == "enum",
-                                       "Enum '%s' in scheme '%s', section '%s' references " ..
-                                       "variable '%s' with non enum type '%s'",
-                                       v.value, scheme, r[2], r[3], t.type )
+       local t  = s[v.name]
+       local so = scheme:section(r[2])
+       local to = so:option(v.name)
 
-                               if not t.values then
-                                       t.values = { [v.value] = v.title or v.value }
-                               else
-                                       t.values[v.value] = v.title or v.value
+       for k, v2 in pairs(v) do
+               if k ~= "name" and k ~= "section" and k:sub(1,1) ~= "." then
+                       if k == "depends" then
+                               t.depends = self:_read_dependency( v2, t.depends )
+                               if not t.depends then
+                                       error(scheme:error(so:error(
+                                               ERR.SME_BADDEP(to, util.serialize_data(v2))
+                                       )))
                                end
-
-                               if v.default then
-                                       _assert( not t.default,
-                                               "Enum '%s' in scheme '%s', section '%s' redeclares " ..
-                                               "the default value of variable '%s'",
-                                               v.value, scheme, r[2], v.variable )
-
-                                       t.default = v.value
+                       elseif k == "validator" then
+                               t.validators = self:_read_validator( v2, t.validators )
+                               if not t.validators then
+                                       error(scheme:error(so:error(
+                                               ERR.SME_BADVAL(to, util.serialize_data(v2))
+                                       )))
+                               end
+                       elseif k == "valueof" then
+                               local values, err = self:_read_reference( v2 )
+                               if err then
+                                       error(scheme:error(so:error(
+                                               ERR.REFERENCE(to, util.serialize_data(v2)):child(err)
+                                       )))
                                end
+                               t.type   = "reference"
+                               t.values = values
+                               t.valueof = type(v2) == "table" and v2 or {v2}
+                       elseif k == "required" then
+                               t[k] = _bool(v2)
+                       elseif k == "minlength" or k == "maxlength" or
+                   k == "minimum" or k == "maximum"
+            then
+                               t[k] = tonumber(v2)
+                       else
+                               t[k] = t[k] or v2
                        end
                end
        end
 
-       return self
+       t.type     = t.type     or "variable"
+       t.datatype = t.datatype or "string"
+       t.required = t.required or false
 end
 
--- Read a depency specification
-function UVL._read_depency( self, value, deps )
-       local parts     = luci.util.split( value, "%s*,%s*", nil, true )
-       local condition = { }
+-- Step 3: get all enums
+function UVL._parse_enum(self, scheme, k, v)
+       local ok, err = _req( TYPE_ENUM, k, v, { "value", "variable" } )
+       if err then error(scheme:error(err)) end
 
-       for i, val in ipairs(parts) do
-               local k, v = unpack(luci.util.split( val, "%s*=%s*", nil, true ))
+       local r, err = _ref( TYPE_ENUM, v )
+       if err then error(scheme:error(err)) end
 
-               if k and (
-                       k:match("^%$?[a-zA-Z0-9_]+%.%$?[a-zA-Z0-9_]+%.%$?[a-zA-Z0-9_]+$") or
-                       k:match("^%$?[a-zA-Z0-9_]+%.%$?[a-zA-Z0-9_]+$") or
-                       k:match("^%$?[a-zA-Z0-9_]+$")
-               ) then
-                       condition[k] = v or true
-               else
-                       return nil
-               end
+       local p = self.packages[r[1]]
+       if not p then
+               error(scheme:error(
+                       ERR.SME_EBADPACK({scheme:sid(), '', '', v.value}, r[1])
+               ))
        end
 
-       if not deps then
-               deps = { condition }
+       local s = p.variables[r[2]]
+       if not s then
+               error(scheme:error(
+                       ERR.SME_EBADSECT({scheme:sid(), '', '', v.value}, r[2])
+               ))
+       end
+
+       local t = s[r[3]]
+       if not t then
+               error(scheme:error(
+                       ERR.SME_EBADOPT({scheme:sid(), '', '', v.value}, r[3])
+               ))
+       end
+
+
+       local so = scheme:section(r[2])
+       local oo = so:option(r[3])
+       local eo = oo:enum(v.value)
+
+       if t.type ~= "enum" and t.type ~= "reference" then
+               error(scheme:error(ERR.SME_EBADTYPE(eo)))
+       end
+
+       if not t.values then
+               t.values = { [v.value] = v.title or v.value }
+               t.valuelist = { {value = v.value, title = v.title} }
        else
-               table.insert( deps, condition )
+               t.values[v.value] = v.title or v.value
+               t.valuelist[#t.valuelist + 1] = {value = v.value, title = v.title}
+       end
+
+       if not t.enum_depends then
+               t.enum_depends = { }
+       end
+
+       if v.default then
+               if t.default then
+                       error(scheme:error(ERR.SME_EBADDEF(eo)))
+               end
+               t.default = v.value
+       end
+
+       if v.depends then
+               t.enum_depends[v.value] = self:_read_dependency(
+                       v.depends, t.enum_depends[v.value]
+               )
+
+               if not t.enum_depends[v.value] then
+                       error(scheme:error(so:error(oo:error(
+                               ERR.SME_BADDEP(eo, util.serialize_data(v.depends))
+                       ))))
+               end
+       end
+end
+
+-- Read a dependency specification
+function UVL._read_dependency( self, values, deps )
+       local expr = "%$?[%w_]+"
+       if values then
+               values = ( type(values) == "table" and values or { values } )
+               for _, value in ipairs(values) do
+                       local condition = { }
+                       for val in value:gmatch("[^,]+") do
+                               local k, e, v = val:match("%s*([%w$_.]+)%s*(=?)%s*(.*)")
+
+                               if k and (
+                                       k:match("^"..expr.."%."..expr.."%."..expr.."$") or
+                                       k:match("^"..expr.."%."..expr.."$") or
+                                       k:match("^"..expr.."$")
+                               ) then
+                                       condition[k] = (e == '=') and v or true
+                               else
+                                       return nil
+                               end
+                       end
+
+                       if not deps then
+                               deps = { condition }
+                       else
+                               deps[#deps+1] = condition
+                       end
+               end
        end
 
        return deps
 end
 
 -- Read a validator specification
-function UVL._read_validator( self, value, validators )
-       local validator
+function UVL._read_validator( self, values, validators )
+       if values then
+               values = ( type(values) == "table" and values or { values } )
+               for _, value in ipairs(values) do
+                       local validator
+
+                       if value:match("^exec:") then
+                               validator = value:gsub("^exec:","")
+                       elseif value:match("^lua:") then
+                               validator = self:_resolve_function( (value:gsub("^lua:","") ) )
+                       elseif value:match("^regexp:") then
+                               local pattern = value:gsub("^regexp:","")
+                               validator = function( type, dtype, pack, sect, optn, ... )
+                                       local values = { ... }
+                                       for _, v in ipairs(values) do
+                                               local ok, match =
+                                                       pcall( string.match, v, pattern )
+
+                                               if not ok then
+                                                       return false, match
+                                               elseif not match then
+                                                       return false,
+                                                               'Value "%s" does not match pattern "%s"' % {
+                                                                       v, pattern
+                                                               }
+                                               end
+                                       end
+                                       return true
+                               end
+                       end
 
-       if value and value:match("/") and self.datatypes.file(value) then
-               validator = value
-       else
-               validator = self:_resolve_function( value )
+                       if validator then
+                               if not validators then
+                                       validators = { validator }
+                               else
+                                       validators[#validators+1] = validator
+                               end
+                       else
+                               return nil
+                       end
+               end
+
+               return validators
        end
+end
+
+-- Read a reference specification (XXX: We should validate external configs too...)
+function UVL._read_reference( self, values )
+       local val = { }
+       values = ( type(values) == "table" and values or { values } )
+
+       for _, value in ipairs(values) do
+               local ref = util.split(value, ".")
+
+               if #ref == 2 or #ref == 3 then
+                       local co = config( self, ref[1] )
+                       if not co:config() then return false, co:errors() end
 
-       if validator then
-               if not validators then
-                       validators = { validator }
+                       for k, v in pairs(co:config()) do
+                               if v['.type'] == ref[2] then
+                                       if #ref == 2 then
+                                               if v['.anonymous'] == true then
+                                                       return false, ERR.SME_INVREF('', value)
+                                               end
+                                               val[k] = k      -- XXX: title/description would be nice
+                                       elseif v[ref[3]] then
+                                               val[v[ref[3]]] = v[ref[3]]  -- XXX: dito
+                                       end
+                               end
+                       end
                else
-                       table.insert( validators, validator )
+                       return false, ERR.SME_BADREF('', value)
                end
-
-               return validators
        end
+
+       return val, nil
 end
 
 -- Resolve given path
 function UVL._resolve_function( self, value )
-       local path = luci.util.split(value, ".")
+       local path = util.split(value, ".")
 
        for i=1, #path-1 do
-               local stat, mod = pcall(require, table.concat(path, ".", 1, i))
+               local stat, mod = pcall(
+                       require, table.concat(path, ".", 1, i)
+               )
+
                if stat and mod then
                        for j=i+1, #path-1 do
                                if not type(mod) == "table" then
-                                       break;
+                                       break
                                end
                                mod = mod[path[j]]
                                if not mod then
@@ -501,3 +843,367 @@ function UVL._resolve_function( self, value )
                end
        end
 end
+
+
+--- Object representation of an uvl item - base class.
+uvlitem = util.class()
+
+function uvlitem.cid(self)
+       if #self.cref == 1 then
+               return self.cref[1]
+       else
+               local r = { unpack(self.cref) }
+               local c = self.c
+               if c and c[r[2]] and c[r[2]]['.anonymous'] and c[r[2]]['.index'] then
+                       r[2] = '@' .. c[r[2]]['.type'] ..
+                                  '[' .. tostring(c[r[2]]['.index']) .. ']'
+               end
+               return table.concat( r, '.' )
+       end
+end
+
+function uvlitem.sid(self)
+       return table.concat( self.sref, '.' )
+end
+
+function uvlitem.scheme(self, opt)
+       local s = self.s and self.s.packages
+       s = s      and s[self.sref[1]]
+       if #self.sref == 4 or #self.sref == 3 then
+               s = s      and s.variables
+               s = s      and s[self.sref[2]]
+               s = s      and s[self.sref[3]]
+       elseif #self.sref == 2 then
+               s = s      and s.sections
+               s = s      and s[self.sref[2]]
+       end
+
+       if s and opt then
+               return s[opt]
+       elseif s then
+               return s
+       end
+end
+
+function uvlitem.config(self, opt)
+       local c = self.c
+
+       if #self.cref >= 2 and #self.cref <= 4 then
+               c = c and self.c[self.cref[2]] or nil
+               if #self.cref >= 3 then
+                       c = c and c[self.cref[3]] or nil
+               end
+       end
+
+       if c and opt then
+               return c[opt]
+       elseif c then
+               return c
+       end
+end
+
+function uvlitem.title(self)
+       return self:scheme() and self:scheme('title') or
+               self.cref[3] or self.cref[2] or self.cref[1]
+end
+
+function uvlitem.type(self)
+       if self.t == TYPE_CONFIG then
+               return 'config'
+       elseif self.t == TYPE_SECTION then
+               return 'section'
+       elseif self.t == TYPE_OPTION then
+               return 'option'
+       elseif self.t == TYPE_ENUM then
+               return 'enum'
+       end
+end
+
+function uvlitem.error(self, ...)
+       if not self.e then
+               local errconst = { ERR.CONFIG, ERR.SECTION, ERR.OPTION, ERR.OPTION }
+               self.e = errconst[#self.cref]( self )
+       end
+
+       return self.e:child( ... )
+end
+
+function uvlitem.errors(self)
+       return self.e
+end
+
+function uvlitem.ok(self)
+       return not self:errors()
+end
+
+function uvlitem.parent(self)
+       if self.p then
+               return self.p
+       elseif #self.cref == 3 or #self.cref == 4 then
+               return section( self.s, self.c, self.cref[1], self.cref[2] )
+       elseif #self.cref == 2 then
+               return config( self.s, self.c, self.cref[1] )
+       else
+               return nil
+       end
+end
+
+function uvlitem._loadconf(self, co, c, configdir)
+       co = co or self._configcache
+       if not co then
+               local err
+               co, err = uci.cursor(configdir):get_all(c)
+
+               if err then
+                       self:error(ERR.UCILOAD(self, err))
+               end
+
+               self._configcache = co
+       end
+       return co
+end
+
+
+--- Object representation of a scheme.
+-- @class      scheme
+-- @cstyle     instance
+-- @name       luci.uvl.scheme
+
+--- Scheme instance constructor.
+-- @class                      function
+-- @name                       scheme
+-- @param scheme       Scheme instance
+-- @param co           Configuration data
+-- @param c                    Configuration name
+-- @return                     Config instance
+scheme = util.class(uvlitem)
+
+function scheme.__init__(self, scheme, co, c)
+       if not c then
+               c, co = co, nil
+       end
+
+       self.cref = { c }
+       self.sref = { c }
+       self.c    = self:_loadconf(co, c, scheme.configdir)
+       self.s    = scheme
+       self.t    = TYPE_SCHEME
+end
+
+--- Add an error to scheme.
+-- @return     Scheme error context
+function scheme.error(self, ...)
+       if not self.e then self.e = ERR.SCHEME( self ) end
+       return self.e:child( ... )
+end
+
+--- Get an associated config object.
+-- @return     Config instance
+function scheme.config(self)
+       local co = config( self.s, self.cref[1] )
+             co.p = self
+
+       return co
+end
+
+--- Get all section objects associated with this scheme.
+-- @return     Table containing all associated luci.uvl.section instances
+function scheme.sections(self)
+       local v = { }
+       if self.s.packages[self.sref[1]].sections then
+               for o, _ in pairs( self.s.packages[self.sref[1]].sections ) do
+                       v[#v+1] = option(
+                               self.s, self.c, self.cref[1], self.cref[2], o
+                       )
+               end
+       end
+       return v
+end
+
+--- Get an associated section object.
+-- @param s    Section to select
+-- @return     Section instance
+function scheme.section(self, s)
+       local so = section( self.s, self.c, self.cref[1], s )
+             so.p = self
+
+       return so
+end
+
+
+--- Object representation of a config.
+-- @class      config
+-- @cstyle     instance
+-- @name       luci.uvl.config
+
+--- Config instance constructor.
+-- @class                      function
+-- @name                       config
+-- @param scheme       Scheme instance
+-- @param co           Configuration data
+-- @param c                    Configuration name
+-- @return                     Config instance
+config = util.class(uvlitem)
+
+function config.__init__(self, scheme, co, c)
+       if not c then
+               c, co = co, nil
+       end
+       self.cref = { c }
+       self.sref = { c }
+       self.c    = self:_loadconf(co, c, scheme.configdir)
+       self.s    = scheme
+       self.t    = TYPE_CONFIG
+end
+
+--- Get all section objects associated with this config.
+-- @return     Table containing all associated luci.uvl.section instances
+function config.sections(self)
+       local v = { }
+       if self.s.packages[self.sref[1]].sections then
+               for o, _ in pairs( self.s.packages[self.sref[1]].sections ) do
+                       v[#v+1] = option(
+                               self.s, self.c, self.cref[1], self.cref[2], o
+                       )
+               end
+       end
+       return v
+end
+
+--- Get an associated section object.
+-- @param s    Section to select
+-- @return     Section instance
+function config.section(self, s)
+       local so = section( self.s, self.c, self.cref[1], s )
+             so.p = self
+
+       return so
+end
+
+
+--- Object representation of a scheme/config section.
+-- @class      module
+-- @cstyle     instance
+-- @name       luci.uvl.section
+
+--- Section instance constructor.
+-- @class                      function
+-- @name                       section
+-- @param scheme       Scheme instance
+-- @param co           Configuration data
+-- @param c                    Configuration name
+-- @param s                    Section name
+-- @return                     Section instance
+section = util.class(uvlitem)
+
+function section.__init__(self, scheme, co, c, s)
+       self.cref = { c, s }
+       self.sref = { c, co and co[s] and co[s]['.type'] or s }
+       self.c    = self:_loadconf(co, c, scheme.configdir)
+       self.s    = scheme
+       self.t    = TYPE_SECTION
+end
+
+--- Get all option objects associated with this section.
+-- @return     Table containing all associated luci.uvl.option instances
+function section.variables(self)
+       local v = { }
+       if self.s.packages[self.sref[1]].variables[self.sref[2]] then
+               for o, _ in pairs(
+                       self.s.packages[self.sref[1]].variables[self.sref[2]]
+               ) do
+                       v[#v+1] = option(
+                               self.s, self.c, self.cref[1], self.cref[2], o
+                       )
+               end
+       end
+       return v
+end
+
+--- Get an associated option object.
+-- @param o    Option to select
+-- @return     Option instance
+function section.option(self, o)
+       local oo = option( self.s, self.c, self.cref[1], self.cref[2], o )
+             oo.p = self
+
+       return oo
+end
+
+
+--- Object representation of a scheme/config option.
+-- @class      module
+-- @cstyle     instance
+-- @name       luci.uvl.option
+
+--- Section instance constructor.
+-- @class                      function
+-- @name                       option
+-- @param scheme       Scheme instance
+-- @param co           Configuration data
+-- @param c                    Configuration name
+-- @param s                    Section name
+-- @param o                    Option name
+-- @return                     Option instance
+option = util.class(uvlitem)
+
+function option.__init__(self, scheme, co, c, s, o)
+       self.cref = { c, s, o }
+       self.sref = { c, co and co[s] and co[s]['.type'] or s, o }
+       self.c    = self:_loadconf(co, c, scheme.configdir)
+       self.s    = scheme
+       self.t    = TYPE_OPTION
+end
+
+--- Get the value of this option.
+-- @return     The associated configuration value
+function option.value(self)
+       local v = self:config() or self:scheme('default')
+       if v and self:scheme('multival') then
+               v = util.split( v, "%s+", nil, true )
+       end
+       return v
+end
+
+--- Get the associated section information in scheme.
+-- @return     Table containing the scheme properties
+function option.section(self)
+       return self.s.packages[self.sref[1]].sections[self.sref[2]]
+end
+
+--- Construct an enum object instance from given or default value.
+-- @param v    Value to select
+-- @return     Enum instance for selected value
+function option.enum(self, val)
+       return enum(
+               self.s, self.c,
+               self.cref[1], self.cref[2], self.cref[3],
+               val or self:value()
+       )
+end
+
+
+--- Object representation of a enum value.
+-- @class      module
+-- @cstyle     instance
+-- @name       luci.uvl.enum
+
+--- Section instance constructor.
+-- @class                      function
+-- @name                       enum
+-- @param scheme       Scheme instance
+-- @param co           Configuration data
+-- @param c                    Configuration name
+-- @param s                    Section name
+-- @param o                    Enum name
+-- @param v                    Enum value
+-- @return                     Enum value instance
+enum = util.class(option)
+
+function enum.__init__(self, scheme, co, c, s, o, v)
+       self.cref = { c, s, o, v }
+       self.sref = { c, co and co[s] and co[s]['.type'] or s, o, v }
+       self.c    = self:_loadconf(co, c, scheme.configdir)
+       self.s    = scheme
+       self.t    = TYPE_ENUM
+end