Module:String

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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

--[====[
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".  Both 
strings have any leading or trailing whitespace removed before searching.

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 source_str = frame.args.source or '';
    local target_str = frame.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.

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
        
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.

Both "source" and "target" will be trimmed so that any leading or trailing 
whitespace is removed prior to searching.  This function should be safe for
UTF-8 strings.
]====]
function str.find( frame )
    local source_str = frame.args.source or '';
    local pattern = frame.args.target or '';
    local start_pos = tonumber(frame.args.start) or 1;
    local plain = frame.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
return str