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: {{#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.  Usage: {{#invoke:String|match|source_string|pattern_string|start_index|match_number|plain_flag|nomatch_output}} OR {{#invoke:String|pos|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  ]] 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'];          if s == '' then         return str._error( 'Target string is empty' );     end     if pattern == '' then         return str._error( 'Pattern string is empty' );     end     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  --[[ 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  --[[ 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 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 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 = 'String Module Error: ' .. error_str .. '';     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