--[[
LuCI - Utility library

Description:
Several common useful Lua functions

FileId:
$Id$

License:
Copyright 2008 Steven Barth <steven@midlink.org>

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

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

]]--

--- LuCI utility functions.
module("luci.util", package.seeall)

--
-- Class helper routines
--

--- Create a Class object (Python-style object model).
-- The class object can be instantiated by calling itself.
-- Any class functions or shared parameters can be attached to this object.
-- Attaching a table to the class object makes this table shared between
-- all instances of this class. For object parameters use the __init__ function.
-- Classes can inherit member functions and values from a base class.
-- Class can be instantiated by calling them. All parameters will be passed
-- to the __init__ function of this class - if such a function exists.
-- The __init__ function must be used to set any object parameters that are not shared
-- with other objects of this class. Any return values will be ignored.
-- @param base	The base class to inherit from (optional)
-- @return		A class object
-- @see			instanceof
-- @see			clone
function class(base)
	local class = {}

	local create = function(class, ...)
		local inst = {}
		setmetatable(inst, {__index = class})

		if inst.__init__ then
			local stat, err = copcall(inst.__init__, inst, ...)
			if not stat then
				error(err)
			end
		end

		return inst
	end

	local classmeta = {__call = create}

	if base then
		classmeta.__index = base
	end

	setmetatable(class, classmeta)
	return class
end

--- Test whether the given object is an instance of the given class.
-- @param object	Object instance
-- @param class		Class object to test against
-- @return			Boolean indicating whether the object is an instance
-- @see				class
-- @see				clone
function instanceof(object, class)
	local meta = getmetatable(object)
	while meta and meta.__index do
		if meta.__index == class then
			return true
		end
		meta = getmetatable(meta.__index)
	end
	return false
end


--
-- Scope manipulation routines
--

--- Replace a function scope with a shallow copy of itself.
-- This is useful if you want to get rid of several unwanted side effects
-- while changing the scope of a certain Lua function.
-- @param f		Lua function
function resfenv(f)
	setfenv(f, clone(getfenv(f)))
end

--- Store given object associated with given key in the scope of a function.
-- @param f		Lua function
-- @param key	String value containg the key of the object to store
-- @param obj	Object to store in the scope
-- @return		Always nil
-- @see updfenv
-- @see resfenv
function extfenv(f, key, obj)
	local scope = getfenv(f)
	scope[key] = obj
end

--- Extend the scope of a function with the contents of a table
-- @param f		Lua function
-- @param key	String value containg the key of the object to store
-- @param obj	Object to store in the scope
-- @return		Always nil
-- @see extfenv
-- @see resfenv
function updfenv(f, extscope)
	update(getfenv(f), extscope)
end

--- Create a new or get an already existing thread local store associated with
-- the current active coroutine. A thread local store is private a table object
-- whose values can't be accessed from outside of the running coroutine.
-- @return	Table value representing the corresponding thread local store
function threadlocal()
	local tbl = {}

	local function get(self, key)
		local c = coroutine.running()
		local thread = coxpt[c] or c or 0
		if not rawget(self, thread) then
			return nil
		end
		return rawget(self, thread)[key]
	end

	local function set(self, key, value)
		local c = coroutine.running()
		local thread = coxpt[c] or c or 0
		if not rawget(self, thread) then
			rawset(self, thread, {})
		end
		rawget(self, thread)[key] = value
	end

	setmetatable(tbl, {__index = get, __newindex = set, __mode = "k"})

	return tbl
end


--
-- Debugging routines
--

--- Write given object to stderr.
-- @param obj	Value to write to stderr
-- @return		Boolean indicating whether the write operation was successful
function perror(obj)
	return io.stderr:write(tostring(obj) .. "\n")
end

--- Recursively dumps a table to stdout, useful for testing and debugging.
-- @param t	Table value to dump
-- @param i	Number of tabs to prepend to each line
-- @return	Always nil
function dumptable(t, i)
	i = i or 0
	for k,v in pairs(t) do
		print(string.rep("\t", i) .. tostring(k), tostring(v))
		if type(v) == "table" then
			dumptable(v, i+1)
		end
	end
end


--
-- String and data manipulation routines
--

--- Escapes all occurrences of the given character in given string.
-- @param s	String value containing unescaped characters
-- @param c	String value with character to escape (optional, defaults to "\")
-- @return	String value with each occurrence of character escaped with "\"
function escape(s, c)
	c = c or "\\"
	return s:gsub(c, "\\" .. c)
end

--- Create valid XML PCDATA from given string.
-- @param value	String value containing the data to escape
-- @return		String value containing the escaped data
function pcdata(value)
	value = value:gsub("&", "&amp;")
	value = value:gsub('"', "&quot;")
	value = value:gsub("'", "&apos;")
	value = value:gsub("<", "&lt;")
	return value:gsub(">", "&gt;")
end

--- Splits given string on a defined separator sequence and return a table
-- containing the resulting substrings. The optional max parameter specifies
-- the number of bytes to process, regardless of the actual length of the given
-- string. The optional last parameter, regex, specifies whether the separator
-- sequence is interpreted as regular expression.
-- @param str		String value containing the data to split up
-- @param pat		String with separator pattern (optional, defaults to "\n")
-- @param max		Maximum times to split (optional)
-- @param regex 	Boolean indicating whether to interpret the separator
--					pattern as regular expression (optional, default is false)
-- @return			Table containing the resulting substrings
function split(str, pat, max, regex)
	pat = pat or "\n"
	max = max or #str

	local t = {}
	local c = 1

	if #str == 0 then
		return {""}
	end

	if #pat == 0 then
		return nil
	end

	if max == 0 then
		return str
	end

	repeat
		local s, e = str:find(pat, c, not regex)
		max = max - 1
		if s and max < 0 then
			table.insert(t, str:sub(c))
		else
			table.insert(t, str:sub(c, s and s - 1))
		end
		c = e and e + 1 or #str + 1
	until not s or max < 0

	return t
end

--- Remove leading and trailing whitespace from given string value.
-- @param str	String value containing whitespace padded data
-- @return		String value with leading and trailing space removed
function trim(str)
	local s = str:gsub("^%s*(.-)%s*$", "%1")
	return s
end

--- Parse certain units from the given string and return the canonical integer
-- value or 0 if the unit is unknown. Upper- or lower case is irrelevant.
-- Recognized units are:
--	o "y"	- one year   (60*60*24*366)
--  o "m"	- one month  (60*60*24*31)
--  o "w"	- one week   (60*60*24*7)
--  o "d"	- one day    (60*60*24)
--  o "h"	- one hour	 (60*60)
--  o "min"	- one minute (60)
--  o "kb"  - one kilobyte (1024)
--  o "mb"	- one megabyte (1024*1024)
--  o "gb"	- one gigabyte (1024*1024*1024)
--  o "kib" - one si kilobyte (1000)
--  o "mib"	- one si megabyte (1000*1000)
--  o "gib"	- one si gigabyte (1000*1000*1000)
-- @param ustr	String containing a numerical value with trailing unit
-- @return		Number containing the canonical value
function parse_units(ustr)

	local val = 0

	-- unit map
	local map = {
		-- date stuff
		y   = 60 * 60 * 24 * 366,
		m   = 60 * 60 * 24 * 31,
		w   = 60 * 60 * 24 * 7,
		d   = 60 * 60 * 24,
		h   = 60 * 60,
		min = 60,

		-- storage sizes
		kb  = 1024,
		mb  = 1024 * 1024,
		gb  = 1024 * 1024 * 1024,

		-- storage sizes (si)
		kib = 1000,
		mib = 1000 * 1000,
		gib = 1000 * 1000 * 1000
	}

	-- parse input string
	for spec in ustr:lower():gmatch("[0-9%.]+[a-zA-Z]*") do

		local num = spec:gsub("[^0-9%.]+$","")
		local spn = spec:gsub("^[0-9%.]+", "")

		if map[spn] or map[spn:sub(1,1)] then
			val = val + num * ( map[spn] or map[spn:sub(1,1)] )
		else
			val = val + num
		end
	end


	return val
end

--- Combines two or more numerically indexed tables into one.
-- @param tbl1	Table value to combine
-- @param tbl2	Table value to combine
-- @param ...	More tables to combine
-- @return		Table value containing all values of given tables
function combine(...)
	local result = {}
	for i, a in ipairs(arg) do
		for j, v in ipairs(a) do
			table.insert(result, v)
		end
	end
	return result
end

--- Checks whether the given table contains the given value.
-- @param table	Table value
-- @param value	Value to search within the given table
-- @return		Boolean indicating whether the given value occurs within table
function contains(table, value)
	for k, v in pairs(table) do
		if value == v then
			return k
		end
	end
	return false
end

--- Update values in given table with the values from the second given table.
-- Both table are - in fact - merged together.
-- @param t			Table which should be updated
-- @param updates	Table containing the values to update
-- @return			Always nil
function update(t, updates)
	for k, v in pairs(updates) do
		t[k] = v
	end
end

--- Clones the given object and return it's copy.
-- @param object	Table value to clone
-- @param deep		Boolean indicating whether to do recursive cloning
-- @return			Cloned table value
function clone(object, deep)
	local copy = {}

	for k, v in pairs(object) do
		if deep and type(v) == "table" then
			v = clone(v, deep)
		end
		copy[k] = v
	end

	setmetatable(copy, getmetatable(object))

	return copy
end


--- Create a dynamic table which automatically creates subtables.
-- @return	Dynamic Table
function dtable()
        return setmetatable({}, { __index =
                function(tbl, key)
                        return rawget(tbl, key)
                         or rawget(rawset(tbl, key, dtable()), key)
                end
        })
end


-- Serialize the contents of a table value.
function _serialize_table(t)
	local data = ""
	for k, v in pairs(t) do
		k = serialize_data(k)
		v = serialize_data(v)
		data = data .. ( #data > 0 and ", " or "" ) ..
			'[' .. k .. '] = ' .. v
	end
	return data
end

--- Recursively serialize given data to lua code, suitable for restoring
-- with loadstring().
-- @param val	Value containing the data to serialize
-- @return		String value containing the serialized code
-- @see			restore_data
-- @see			get_bytecode
function serialize_data(val)
	if val == nil then
		return "nil"
	elseif type(val) == "number" then
		return val
	elseif type(val) == "string" then
		return string.format("%q", val)
	elseif type(val) == "boolean" then
		return val and "true" or "false"
	elseif type(val) == "function" then
		return string.format("loadstring(%q)", get_bytecode(val))
	elseif type(val) == "table" then
		return "{ " .. _serialize_table(val) .. " }"
	else
		return '"[unhandled data type:' .. type(val) .. ']"'
	end
end

--- Restore data previously serialized with serialize_data().
-- @param str	String containing the data to restore
-- @return		Value containing the restored data structure
-- @see			serialize_data
-- @see			get_bytecode
function restore_data(str)
	return loadstring("return " .. str)()
end


--
-- Byte code manipulation routines
--

--- Return the current runtime bytecode of the given data. The byte code
-- will be stripped before it is returned.
-- @param val	Value to return as bytecode
-- @return		String value containing the bytecode of the given data
function get_bytecode(val)
	local code

	if type(val) == "function" then
		code = string.dump(val)
	else
		code = string.dump( loadstring( "return " .. serialize_data(val) ) )
	end

	return code and strip_bytecode(code)
end

--- Strips unnescessary lua bytecode from given string. Information like line
-- numbers and debugging numbers will be discarded. Original version by
-- Peter Cawley (http://lua-users.org/lists/lua-l/2008-02/msg01158.html)
-- @param code	String value containing the original lua byte code
-- @return		String value containing the stripped lua byte code
function strip_bytecode(code)
	local version, format, endian, int, size, ins, num, lnum = code:byte(5, 12)
	local subint
	if endian == 1 then
		subint = function(code, i, l)
			local val = 0
			for n = l, 1, -1 do
				val = val * 256 + code:byte(i + n - 1)
			end
			return val, i + l
		end
	else
		subint = function(code, i, l)
			local val = 0
			for n = 1, l, 1 do
				val = val * 256 + code:byte(i + n - 1)
			end
			return val, i + l
		end
	end

	local strip_function
	strip_function = function(code)
		local count, offset = subint(code, 1, size)
		local stripped, dirty = string.rep("\0", size), offset + count
		offset = offset + count + int * 2 + 4
		offset = offset + int + subint(code, offset, int) * ins
		count, offset = subint(code, offset, int)
		for n = 1, count do
			local t
			t, offset = subint(code, offset, 1)
			if t == 1 then
				offset = offset + 1
			elseif t == 4 then
				offset = offset + size + subint(code, offset, size)
			elseif t == 3 then
				offset = offset + num
			elseif t == 254 or t == 9 then
				offset = offset + lnum
			end
		end
		count, offset = subint(code, offset, int)
		stripped = stripped .. code:sub(dirty, offset - 1)
		for n = 1, count do
			local proto, off = strip_function(code:sub(offset, -1))
			stripped, offset = stripped .. proto, offset + off - 1
		end
		offset = offset + subint(code, offset, int) * int + int
		count, offset = subint(code, offset, int)
		for n = 1, count do
			offset = offset + subint(code, offset, size) + size + int * 2
		end
		count, offset = subint(code, offset, int)
		for n = 1, count do
			offset = offset + subint(code, offset, size) + size
		end
		stripped = stripped .. string.rep("\0", int * 3)
		return stripped, offset
	end

	return code:sub(1,12) .. strip_function(code:sub(13,-1))
end


--
-- Sorting iterator functions
--

function _sortiter( t, f )
	local keys = { }

	for k, v in pairs(t) do
		table.insert( keys, k )
	end

	local _pos = 0
	local _len = table.getn( keys )

	table.sort( keys, f )

	return function()
		_pos = _pos + 1
		if _pos <= _len then
			return keys[_pos], t[keys[_pos]]
		end
	end
end

--- Return a key, value iterator which returns the values sorted according to
-- the provided callback function.
-- @param t	The table to iterate
-- @param f A callback function to decide the order of elements
-- @return	Function value containing the corresponding iterator
function spairs(t,f)
	return _sortiter( t, f )
end

--- Return a key, value iterator for the given table.
-- The table pairs are sorted by key.
-- @param t	The table to iterate
-- @return	Function value containing the corresponding iterator
function kspairs(t)
	return _sortiter( t )
end

--- Return a key, value iterator for the given table.
-- The table pairs are sorted by value.
-- @param t	The table to iterate
-- @return	Function value containing the corresponding iterator
function vspairs(t)
	return _sortiter( t, function (a,b) return t[a] < t[b] end )
end


--
-- System utility functions
--

--- Test whether the current system is operating in big endian mode.
-- @return	Boolean value indicating whether system is big endian
function bigendian()
	return string.byte(string.dump(function() end), 7) == 0
end

--- Execute given commandline and gather stdout.
-- @param command	String containing command to execute
-- @return			String containing the command's stdout
function exec(command)
	local pp   = io.popen(command)
	local data = pp:read("*a")
	pp:close()

	return data
end

--- Execute given commandline and gather stdout.
-- @param command	String containing the command to execute
-- @return			Table containing the command's stdout splitted up in lines
function execl(command)
	local pp   = io.popen(command)
	local line = ""
	local data = {}

	while true do
		line = pp:read()
		if (line == nil) then break end
		table.insert(data, line)
	end
	pp:close()

	return data
end

--- Returns the absolute path to LuCI base directory.
-- @return		String containing the directory path
function libpath()
	return luci.fs.dirname(require("luci.debug").__file__)
end


--
-- Coroutine safe xpcall and pcall versions modified for Luci
-- original version:
-- coxpcall 1.13 - Copyright 2005 - Kepler Project (www.keplerproject.org)
--

local performResume, handleReturnValue
local oldpcall, oldxpcall = pcall, xpcall
coxpt = {}
setmetatable(coxpt, {__mode = "kv"})

-- Identity function for copcall
local function copcall_id(trace, ...)
  return ...
end

--- This is a coroutine-safe drop-in replacement for Lua's "xpcall"-function
-- @param f		Lua function to be called protected
-- @param err	Custom error handler
-- @param ...	Parameters passed to the function
-- @return		A boolean whether the function call succeeded and the return
--				values of either the function or the error handler
function coxpcall(f, err, ...)
	local res, co = oldpcall(coroutine.create, f)
	if not res then
		local params = {...}
		local newf = function() return f(unpack(params)) end
		co = coroutine.create(newf)
	end
	local c = coroutine.running()
	coxpt[co] = coxpt[c] or c or 0

	return performResume(err, co, ...)
end

--- This is a coroutine-safe drop-in replacement for Lua's "pcall"-function
-- @param f		Lua function to be called protected
-- @param ...	Parameters passed to the function
-- @return		A boolean whether the function call succeeded and the returns
--				values of the function or the error object
function copcall(f, ...)
	return coxpcall(f, copcall_id, ...)
end

-- Handle return value of protected call
function handleReturnValue(err, co, status, ...)
	if not status then
		return false, err(debug.traceback(co, (...)), ...)
	end
	if coroutine.status(co) == 'suspended' then
		return performResume(err, co, coroutine.yield(...))
	else
		return true, ...
	end
end

-- Resume execution of protected function call
function performResume(err, co, ...)
	return handleReturnValue(err, co, coroutine.resume(co, ...))
end