Module:String

    From Nonbinary Wiki
    Revision as of 04:55, 24 February 2013 by m>Dragons flight (Continuing trials and tribulations of string trimming and Wikipedia template quirks)

    Documentation for this module may be created at Module:String/doc

    local str = {}
    
    function str.len( frame )
        return mw.ustring.len( frame.args.s )
    end
    
    function str.sub( frame )
        return mw.ustring.sub( frame.args.s, tonumber( frame.args.i ), tonumber( frame.args.j ) )
    end
    
    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
    
    function str.match( frame )
        return mw.ustring.match( frame.args.s, frame.args.pattern, tonumber( frame.args.i ) )
    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 '<strong class="error">String index out of range</strong>';
        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    
        
        if type( plain ) == 'string' then
            plain = plain:lower();
            if plain == 'false' or plain == 'no' or plain == '0' then
                plain = false;
            else
                plain = true;
            end    
        end
    
        local start = mw.ustring.find( source_str, pattern, start_pos, plain )
        if start == nil then
            start = 0
        end
        
        return start
    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        
    
    return str