--[[



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:

{{#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 str.len( frame )

	local new_args = str._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 str.sub( frame )

	local new_args = str._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 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 {{str sub old}} and is kept in order

to maintain these older templates.

]]

function str.sublength( frame )

	local i = tonumber( frame.args.i ) or 0

	local len = tonumber( frame.args.len )

	return mw.ustring.sub( frame.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 match_buffer = {}

			local index = 1

			match_index = -match_index



			for w in iterator do

				match_bufferindex = w



				-- Circular buffer with length 'match_index'

				-- Wraps around to overwrite matches too old to be the result,

				-- so memory use is O(match_index) and not O(total match count))

				index = (index == match_index) and 1 or (index + 1)

			end



			-- 'index' is now at oldest element, which next iteration would have

			-- overwritten. If 'match_buffer' has fewer than 'index' elements,

			-- there were too few matches; the resulting nil is handled below.

			result = match_bufferindex

		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:

{{#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 is the entry point for #invoke:String|match

function str.match( frame )

	local new_args = str._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 = 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:

{{#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 str.pos( frame )

	local new_args = str._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 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 {{str_find}}, 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( frame )

	local new_args = str._getParameters( frame.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:

{{#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 str.find( frame )

	local new_args = str._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 = 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:

{{#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 str.replace( frame )

	local new_args = str._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 = str._getBoolean( plain )



	if plain then

		pattern = str._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 str.rep( frame )

	local repetitions = tonumber( frame.args2 )

	if not repetitions then

		return str._error( 'function rep expects a number as second parameter, received "' .. ( frame.args2 or '' ) .. '"' )

	end

	return string.rep( frame.args1 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 str.escapePattern( frame )

	local pattern_str = frame.args1

	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(frame)

	local args = str._getParameters(frame.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(frame)

	local args = str._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 str.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



--[[

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_argsarg

		if value == nil then

			value = frame_argsindex

			index = index + 1

		end

		new_argsarg = value

	end



	return new_args

end



--[[

Helper function to handle error messages.

]]

function str._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 str._getBoolean(ignore_errors) then

		return ''

	end



	local error_str = '<strong class="error">String Module Error: ' .. error_str .. '</strong>'

	if error_category ~= '' and not str._getBoolean( no_category ) then

		error_str = '[[Category:' .. error_category .. ']]' .. 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 mw.ustring.gsub( pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1" )

end



return str