--[[  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 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: {{#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.args[2] )  if not repetitions then  return str._error( 'function rep expects a number as second parameter, received "' .. ( 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 str.escapePattern( frame )  local pattern_str = frame.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(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_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 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