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 automatically removes 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 results 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 is added if an error is generated.

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

local str = {}

-- 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 i, 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( 'No boolean value found' ) 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 reported by Module 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 = 'String Module Error: ' .. error_str .. ' '	if error_category ~= '' and not _getBoolean( no_category ) then error_str = '' .. error_str end

return error_str end

-- Helper function that escapes all pattern characters so that they are 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:

OR

Parameters s: The string whose length to report

If invoked using named parameters, Mediawiki automatically removes any leading or trailing whitespace from the target string. ]] function str.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:

OR

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 str.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( 'String subset index out of range' ) end if j < i then return _error( 'String subset indices out of order' ) 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:

OR

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 automatically removes 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 is suppressed and an empty string 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

]] function str.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']

if s == '' then return _error( 'Target string is empty' ) end if pattern == '' then return _error( 'Pattern string is empty' ) end if math.abs(start) < 1 or math.abs(start) > mw.ustring.len( s ) then return _error( 'Requested start is out of range' ) end if match_index == 0 then return _error( 'Match index is out of range' ) end if plain_flag then pattern = _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( 'Match not found' ) else return nomatch end else return result end end

--[[ pos

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

Usage:

OR

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

If invoked using named parameters, Mediawiki automatically removes 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 selects 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 str.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( 'String index out of range' ) 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:

OR

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 automatically removes 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 str.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:

OR

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 str.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

--[[	rep

Repeats a string Usage:

Parameters source: The string to repeat count: The number of repetitions

Invocation supports only unnamed parameters. ]]

function str.rep( frame ) local repetitions = tonumber( frame.args[2] ) if not repetitions then return _error( 'function rep expects a number as second parameter, received "' .. ( frame.args[2] or '' ) .. '"' ) end return string.rep( frame.args[1] or '', repetitions ) end

--[[ reverse

Reverse a string

Usage:

OR

Parameters s: The string to reverse

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

for i = len, 1, -1 do -- strings are immutable in Lua, so use a table ... table.insert( result, mw.ustring.sub( s, i, i ) ) end

-- ... and implode/join it	return table.concat( result ) end

return str