# 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 str = {}  

---
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 will automatically remove any leading or  
trailing whitespace from the target string.  

function str.len  
local new_args = str._getParameters( .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 first 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  
local new_args = str._getParameters( .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 str._error( 'String subset index out of range' )  
end  
if j < i then  
return str._error( 'String subset indices out of order' )  
end  

return mw.ustring.sub( s, i, j )  
end  

---
This function implements that features of and is kept in order  
to maintain these older templates.  

function str.sublength  
local i = tonumber( .args.i ) or 0  
local len = tonumber( .args.len )  
return mw.ustring.sub( .args.s, i + 1, len and ( i + len ) )  
end  

--[[  
_match  

This function returns a substring from the source string that matches a  
specified pattern. It is exported for use in other modules  

Usage:  
strmatch = require("Module:String")._match  
sresult = strmatch( s, pattern, start, match, plain, nomatch )  

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.  

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 str._match( s, pattern, start, match_index, plain_flag, nomatch )  
if s == '' then  
return str._error( 'Target string is empty' )  
end  
if pattern == '' then  
return str._error( 'Pattern string is empty' )  
end  
start = tonumber(start) or 1  
if math.abs(start) < 1 or math.abs(start) > mw.ustring.len( s ) then  
return str._error( 'Requested start is out of range' )  
end  
if match_index == 0 then  
return str._error( 'Match index is out of range' )  
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 str._error( 'Match not found' )  
else  
return nomatch  
end  
else  
return result  
end  
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 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 is the entry point for #invoke:String|match  
function str.match  
local new_args = str._getParameters( .args, {'s', 'pattern', 'start', 'match', 'plain', 'nomatch'} )  
local s = new_args['s'] or ''  
local start = tonumber( new_args['start'] ) or 1  
local plain_flag = str._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 str._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:  

OR  

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 str.pos  
local new_args = str._getParameters( .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 str._error( 'String index out of range' )  
end  

return mw.ustring.sub( target_str, pos, pos )  
end  

---
str_find  

This function duplicates the behavior of , including all of its quirks.  
This is provided in order to support existing templates, but is NOT RECOMMENDED for  
new code and templates. New code is recommended to use the "find" function instead.  

Returns the first index in "source" that is a match to "target". Indexing is 1-based,  
and the function returns -1 if the "target" string is not present in "source".  

Important Note: If the "target" string is empty / missing, this function returns a  
value of "1", which is generally unexpected behavior, and must be accounted for  
separatetly.  

function str.str_find  
local new_args = str._getParameters( .args, {'source', 'target'} )  
local source_str = new_args['source'] or ''  
local target_str = new_args['target'] or ''  

if target_str == '' then  
return 1  
end  

local start = mw.ustring.find( source_str, target_str, 1, true )  
if start == nil then  
start = -1  
end  

return start  
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 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 str.find  
local new_args = str._getParameters( .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 = str._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  
local new_args = str._getParameters( .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 = str._getBoolean( plain )  

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

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

---
count  
This function counts the number of occurrences of one string in another.  

function str.count  
local args = str._getParameters(.args, {'source', 'pattern', 'plain'})  
local source = args.source or ''  
local pattern = args.pattern or ''  
local plain = str._getBoolean(args.plain or true)  
if plain then  
pattern = str._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 str.endswith  
local args = str._getParameters(.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:  

function str.join  
local args = {}  
local sep  
for _, v in ipairs( .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  

---
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.  

function str._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 handle error messages.  

function str._error( error_str )  
local = mw.getCurrentFrame  
local error_category = .args.error_category or 'Errors reported by Module String'  
local ignore_errors = .args.ignore_errors or false  
local no_category = .args.no_category or false  

if str._getBoolean(ignore_errors) then  
return ''  
end  

local error_str = '<strong>String Module Error: ' .. error_str .. '</strong>'  
if error_category ~= '' and not str._getBoolean( no_category ) then  
error_str = '' .. error_str  
end  

return error_str  
end  

---
Helper Function to interpret boolean strings  

function str._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 that escapes all pattern characters so that they will be treated  
as plain text.  

function str._escapePattern( pattern_str )  
return ( string.gsub( pattern_str, "[%(%)%.%%%+%-%*%?%[%^%$%]]", "%%%0" ) )  
end  

return str