Module:String

--[[

This module is intended to provide access to basic string functions.

Most of the functions provided here can be invoked with named parameters,
unnamed parameters, or a mixture.  If named parameters are used, Mediawiki will
automatically remove any leading or trailing whitespace from the parameter.
Depending on the intended use, it may be advantageous to either preserve or
remove such whitespace.

Global options
    ignore_errors: If set to 'true' or 1, any error condition will result in
        an empty string being returned rather than an error message.

    error_category: If an error occurs, specifies the name of a category to
        include with the error message.  The default category is
        [Category:Errors reported by Module String].

    no_category: If set to 'true' or 1, no category will be added if an error
        is generated.

Unit tests for this module are available at Module:String/tests.
]]

local p = {}

--[[
Helper function that populates the argument list given that user may need to use a mix of
named and unnamed parameters.  This is relevant because named parameters are not
identical to unnamed parameters due to string trimming, and when dealing with strings
we sometimes want to either preserve or remove that whitespace depending on the application.
]]
local function _getParameters( frame_args, arg_list )
	local new_args = {}
	local index = 1
	local value
	
	for _, arg in ipairs( arg_list ) do
		value = frame_args[arg]
		if value == nil then
			value = frame_args[index]
			index = index + 1
		end
		new_args[arg] = value
	end
	
	return new_args
end        

--[[
Helper Function to interpret boolean strings
]]
local function _getBoolean( boolean_str )
	local boolean_value
	
	if type( boolean_str ) == 'string' then
		boolean_str = boolean_str:lower()
		if boolean_str == 'false' or boolean_str == 'no' or boolean_str == '0' 
				or boolean_str == '' then
			boolean_value = false
		else
			boolean_value = true
		end
	elseif type( boolean_str ) == 'boolean' then
		boolean_value = boolean_str
	else
		error( 'Cap valor booleà trobat' )
	end
	return boolean_value
end

--[[
Helper function to handle error messages.
]]
local function _error( error_str )
	local frame = mw.getCurrentFrame()
	local error_category = frame.args.error_category or 'Errors detectats pel mòdul String'
	local ignore_errors = frame.args.ignore_errors or false
	local no_category = frame.args.no_category or false
	
	if _getBoolean(ignore_errors) then
		return ''
	end
	
	local error_str = '<strong class="error">Error del mòdul String: ' .. error_str .. '</strong>'
	if error_category ~= '' and not _getBoolean( no_category ) then
		error_str = '[[Categoria:' .. error_category .. ']]' .. error_str
	end
	
	return error_str
end

--[[
Helper function that escapes all pattern characters so that they will be treated
as plain text.
]]
local function _escapePattern( pattern_str )
	return mw.ustring.gsub( pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1" )
end

--[[
len

This function returns the length of the target string.

Usage:
{{#invoke:String|len|target_string|}}
OR
{{#invoke:String|len|s=target_string}}

Parameters
    s: The string whose length to report

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the target string.
]]
function p.len( frame )
	local new_args = _getParameters( frame.args, {'s'} )
	local s = new_args['s'] or ''
	return mw.ustring.len( s )
end

--[[
sub

This function returns a substring of the target string at specified indices.

Usage:
{{#invoke:String|sub|target_string|start_index|end_index}}
OR
{{#invoke:String|sub|s=target_string|i=start_index|j=end_index}}

Parameters
    s: The string to return a subset of
    i: The fist index of the substring to return, defaults to 1.
    j: The last index of the string to return, defaults to the last character.

The first character of the string is assigned an index of 1.  If either i or j
is a negative value, it is interpreted the same as selecting a character by
counting from the end of the string.  Hence, a value of -1 is the same as
selecting the last character of the string.

If the requested indices are out of range for the given string, an error is
reported.
]]
function p.sub( frame )
	local new_args = _getParameters( frame.args, { 's', 'i', 'j' } )
	local s = new_args['s'] or ''
	local i = tonumber( new_args['i'] ) or 1
	local j = tonumber( new_args['j'] ) or -1
	
	local len = mw.ustring.len( s )
	
	-- Convert negatives for range checking
	if i < 0 then
		i = len + i + 1
	end
	if j < 0 then
		j = len + j + 1
	end
	
	if i > len or j > len or i < 1 or j < 1 then
		return _error( 'Índex fora del rang de la cadena' )
	end
	if j < i then
		return _error( 'Índexs de la cadena no ordenats' )
	end
	
	return mw.ustring.sub( s, i, j )
end

--[[
match

This function returns a substring from the source string that matches a
specified pattern.

Usage:
{{#invoke:String|match|source_string|pattern_string|start_index|match_number|plain_flag|nomatch_output}}
OR
{{#invoke:String|match|s=source_string|pattern=pattern_string|start=start_index
    |match=match_number|plain=plain_flag|nomatch=nomatch_output}}

Parameters
    s: The string to search
    pattern: The pattern or string to find within the string
    start: The index within the source string to start the search.  The first
        character of the string has index 1.  Defaults to 1.
    match: In some cases it may be possible to make multiple matches on a single
        string.  This specifies which match to return, where the first match is
        match= 1.  If a negative number is specified then a match is returned
        counting from the last match.  Hence match = -1 is the same as requesting
        the last match.  Defaults to 1.
    plain: A flag indicating that the pattern should be understood as plain
        text.  Defaults to false.
    nomatch: If no match is found, output the "nomatch" value rather than an error.

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from each string.  In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.

If the match_number or start_index are out of range for the string being queried, then
this function generates an error.  An error is also generated if no match is found.
If one adds the parameter ignore_errors=true, then the error will be suppressed and
an empty string will be returned on any failure.

For information on constructing Lua patterns, a form of [regular expression], see:

* http://www.lua.org/manual/5.1/manual.html#5.4.1
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Patterns
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Ustring_patterns

]]
-- This sub-routine is exported for use in other modules
function p._match( s, pattern, start, match_index, plain_flag, nomatch )
	if s == '' then
		return _error( 'Cadena on cercar està buida' )
	end
	if pattern == '' then
		return _error( 'Cadena de cerca està buida' )
	end
	start = tonumber(start) or 1
	if math.abs(start) < 1 or math.abs(start) > mw.ustring.len( s ) then
		return _error( 'Índex d\'inici fora del rang de la cadena' )
	end
	if match_index == 0 then
		return _error( 'Número de coincidència fora de rang' )
	end
	if plain_flag then
		pattern = str._escapePattern( pattern )
	end

	local result
	if match_index == 1 then
		-- Find first match is simple case
		result = mw.ustring.match( s, pattern, start )
	else
		if start > 1 then
			s = mw.ustring.sub( s, start )
		end

		local iterator = mw.ustring.gmatch(s, pattern)
		if match_index > 0 then
			-- Forward search
			for w in iterator do
				match_index = match_index - 1
				if match_index == 0 then
					result = w
					break
				end
			end
		else
			-- Reverse search
			local result_table = {}
			local count = 1
			for w in iterator do
				result_table[count] = w
				count = count + 1
			end

			result = result_table[ count + match_index ]
		end
	end

	if result == nil then
		if nomatch == nil then
			return _error( 'Cap coincidència trobada' )
		else
			return nomatch
		end
	else
		return result
	end
end
-- This is the entry point for #invoke:String|match
function p.match( frame )
	local new_args = _getParameters( frame.args, {'s', 'pattern', 'start', 'match', 'plain', 'nomatch'} )
	local s = new_args['s'] or ''
	local start = tonumber( new_args['start'] ) or 1
	local plain_flag = _getBoolean( new_args['plain'] or false )
	local pattern = new_args['pattern'] or ''
	local match_index = math.floor( tonumber(new_args['match']) or 1 )
	local nomatch = new_args['nomatch']
	
	return p._match( s, pattern, start, match_index, plain_flag, nomatch )
end

--[[
pos

This function returns a single character from the target string at position pos.

Usage:
{{#invoke:String|pos|target_string|index_value}}
OR
{{#invoke:String|pos|target=target_string|pos=index_value}}

Parameters
    target: The string to search
    pos: The index for the character to return

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the target string.  In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.

The first character has an index value of 1.

If one requests a negative value, this function will select a character by counting backwards
from the end of the string.  In other words pos = -1 is the same as asking for the last character.

A requested value of zero, or a value greater than the length of the string returns an error.
]]
function p.pos( frame )
	local new_args = _getParameters( frame.args, {'target', 'pos'} )
	local target_str = new_args['target'] or ''
	local pos = tonumber( new_args['pos'] ) or 0
	
	if pos == 0 or math.abs(pos) > mw.ustring.len( target_str ) then
		return _error( 'Índex fora del rang de la cadena' )
	end    
	
	return mw.ustring.sub( target_str, pos, pos )
end

--[[
find

This function allows one to search for a target string or pattern within another
string.

Usage:
{{#invoke:String|find|source_str|target_string|start_index|plain_flag}}
OR
{{#invoke:String|find|source=source_str|target=target_str|start=start_index|plain=plain_flag}}

Parameters
    source: The string to search
    target: The string or pattern to find within source
    start: The index within the source string to start the search, defaults to 1
    plain: Boolean flag indicating that target should be understood as plain
        text and not as a Lua style regular expression, defaults to true

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the parameter.  In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.

This function returns the first index >= "start" where "target" can be found
within "source".  Indices are 1-based.  If "target" is not found, then this
function returns 0.  If either "source" or "target" are missing / empty, this
function also returns 0.

This function should be safe for UTF-8 strings.
]]
function p.find( frame )
	local new_args = _getParameters( frame.args, {'source', 'target', 'start', 'plain' } ) 
	local source_str = new_args['source'] or ''
	local pattern = new_args['target'] or ''
	local start_pos = tonumber(new_args['start']) or 1
	local plain = new_args['plain'] or true
	
	if source_str == '' or pattern == '' then
		return 0
	end    
	
	plain = _getBoolean( plain )
	
	local start = mw.ustring.find( source_str, pattern, start_pos, plain )
	if start == nil then
		start = 0
	end
	
	return start
end

--[[
replace

This function allows one to replace a target string or pattern within another
string.

Usage:
{{#invoke:String|replace|source_str|pattern_string|replace_string|replacement_count|plain_flag}}
OR
{{#invoke:String|replace|source=source_string|pattern=pattern_string|replace=replace_string|
   count=replacement_count|plain=plain_flag}}

Parameters
    source: The string to search
    pattern: The string or pattern to find within source
    replace: The replacement text
    count: The number of occurences to replace, defaults to all.
    plain: Boolean flag indicating that pattern should be understood as plain
        text and not as a Lua style regular expression, defaults to true
]]
function p.replace( frame )
	local new_args = _getParameters( frame.args, {'source', 'pattern', 'replace', 'count', 'plain' } )
	local source_str = new_args['source'] or ''
	local pattern = new_args['pattern'] or ''
	local replace = new_args['replace'] or ''
	local count = tonumber( new_args['count'] )
	local plain = new_args['plain'] or true
	
	if source_str == '' or pattern == '' then
		return source_str
	end    
	plain = _getBoolean( plain )
	
	if plain then
		pattern = _escapePattern( pattern )
		replace = mw.ustring.gsub( replace, "%%", "%%%%" ) --Only need to escape replacement sequences.
	end
	
	local result
	
	if count ~= nil then
		result = mw.ustring.gsub( source_str, pattern, replace, count )
	else
		result = mw.ustring.gsub( source_str, pattern, replace )
	end        
	
	return result
end

--[[
    simple function to pipe string.rep to templates.
]]
function p.rep( frame )
	local repetitions = tonumber( frame.args[2] )
	if not repetitions then 
		return _error( "s'esperava un número com a segon paràmetre; trobat: " .. ( frame.args[2] or '' ))
	end
	return string.rep( frame.args[1] or '', repetitions )
end

--[[
escapePattern

This function escapes special characters from a Lua string pattern. See [1]
for details on how patterns work.

[1] https://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Patterns

Usage:
{{#invoke:String|escapePattern|pattern_string}}

Parameters
    pattern_string: The pattern string to escape.
]]
function p.escapePattern( frame )
	local pattern_str = frame.args[1]
	if not pattern_str then
		return _error( 'No pattern string specified' )
	end
	local result = _escapePattern( pattern_str )
	return result
end

--[[
count
This function counts the number of occurrences of one string in another.
]]
function p.count(frame)
	local args = _getParameters(frame.args, {'source', 'pattern', 'plain'})
	local source = args.source or ''
	local pattern = args.pattern or ''
	local plain = _getBoolean(args.plain or true)
	if plain then
		pattern = _escapePattern(pattern)
	end
	local _, count = mw.ustring.gsub(source, pattern, '')
	return count
end

--[[
endswith
This function determines whether a string ends with another string.
]]
function p.endswith(frame)
	local args = _getParameters(frame.args, {'source', 'pattern'})
	local source = args.source or ''
	local pattern = args.pattern or ''
	if pattern == '' then
		-- All strings end with the empty string.
		return "yes"
	end
	if mw.ustring.sub(source, -mw.ustring.len(pattern), -1) == pattern then
		return "yes"
	else
		return ""
	end
end

--[[
join

Join all non empty arguments together; the first argument is the separator.
Usage:
{{#invoke:String|join|sep|one|two|three}}
]]
function p.join(frame)
	local args = {}
	local sep
	for _, v in ipairs( frame.args ) do
		if sep then
			if v ~= '' then
				table.insert(args, v)
			end
		else
			sep = v
		end
	end
	return table.concat( args, sep or '' )
end

--[[ 
Strip

This function Strips charecters from string

Usage:
{{#invoke:StringFunc|strip|source_string|charecters_to_strip|plain_flag}}

Parameters
	source: The string to strip
	chars:  The pattern or list of charecters to strip from string, replaced with ''
	plain:  A flag indicating that the chars should be understood as plain text. defaults to true.

Leading and trailing whitespace is also automatically stripped from the string. 
]]
function p.strip( frame )
	local new_args = _getParameters( frame.args,  {'source', 'chars', 'plain'} )
	local source_str = new_args['source'] or ''
	local chars = new_args['chars'] or ''
	source_str = mw.text.trim(source_str)
	if source_str == '' or chars == '' then 
		return source_str
	end
	local l_plain = _getBoolean( new_args['plain'] or true )
	if l_plain then
		chars = _escapePattern( chars )
	end
	local result
	result = mw.ustring.gsub(source_str, "["..chars.."]", '')
	return result
end

--[[
Split

This function Splits a string based on a separator, returns nth substring based on count.

Usage:
{{#invoke:StringFunc|split|source_string|separator|count}}

Parameters:
	source:    The string to return a subset of
	separator: The string to split on 
	count:     The nth substring based on the separator to return
]]
function p.split( frame )
	local new_args = _getParameters( frame.args, {'source', 'separator', 'count'} )
	local source_str = new_args['source'] or ''
	local separator = new_args['separator'] or ''
	local separator_len = mw.ustring.len(separator)
	if source_str == '' or separator == '' then
		return source_str;
	end
	local ret_count = tonumber( new_args['count'] ) or 1
	if ret_count < 1 then
		return ""
	end
	local start = 1
	local iter = mw.ustring.find(source_str, separator, start, true)
	if iter == nil then
		if ret_count == 1 then
			return source_str
		else
			return ""
		end
	else
		iter = iter - 1
	end
	if ret_count == 1 then
		return mw.ustring.sub( source_str, start, iter)
	end
    for i=2, ret_count do
    	start = iter+separator_len + 1
    	iter = mw.ustring.find(source_str, separator, start, true)
    	if iter == nil then
    		if ret_count == i then
    			return mw.ustring.sub(source_str, start, mw.ustring.len(source_str))
    		else
    			return ""
    		end
    	else
    		iter = iter - 1
    	end
    end
    return mw.ustring.sub( source_str,start,iter)
end

function p.isNumber( frame )
	local new_args = _getParameters( frame.args, {'source'} )
	local source_str = new_args['source'] or ''
	if source_str == '' then
	   return "false"
	end
	if tonumber(source_str) == nil and tonumber(string.gsub(source_str, ",", ".", 1) .. '') == nil then
		return "false"
	end
	return "true"
end

return p