/* Any copyright is dedicated to the Public Domain.
 * http://creativecommons.org/publicdomain/zero/1.0/
 */
 
interface(extern-c){
    xml2 = library:: pkgconfig("libxml-2.0").

    include {
        xml2 = {"string.h"}
    }.
}

Matcher = type variant {Sequence, ZeroOrMore, Text}.

matchText = function(text::string, matcher::string, posStart::i64):: i64 {   
    textLength = strlen(text):: i64.
    matcherLength = strlen(matcher):: i64.
    
    if(textLength >= posStart + matcherLength):: i64{
        if(strncmp(text + posStart, matcher, matcherLength) == 0):: i64 {
            matcherLength
            
        } else {-1:: i64}
    } else {-2:: i64}
}


matchSequence = function(text::string, pattern::undefType; i12n(on), posStart::i64):: i64; i12n(off){
    textLength = length(text):: i64.
    
    loop fold(pattern-> matcher:: undefType, posStart->pos):: i64{
        recognizedSymbols = match(text, matcher, pos):: i64.
               
        if (recognizedSymbols > (0::i64)):: i64{
            pos+recognizedSymbols
            
        } else {
            pos:: i64; final
        }
    }
}

matchZeroOrMore= function(text::string, matcher::undefType; i12n(on), posStart::i64):: i64; i12n(off){   
    textLength = length(text):: i64.
    
    loop (posStart->pos):: i64{
        recognizedSymbols = match(text, matcher, pos):: i64.
        
        if (recognizedSymbols > (0::i64)):: i64{
            pos+recognizedSymbols
            
        } else {
            pos:: i64; final
        }
    }
}

match = function(text::string, pattern::undefType; i12n(on), posStart::i64)::i64; i12n(off){

    key= pattern[0]::Matcher.
    switch variant(key) :: int
        case (Sequence) {matchSequence(text, pattern[1], posStart)}
        case (ZeroOrMore) {matchZeroOrMore(text, pattern[1], posStart)}
        case (Text) {matchText(text, pattern[1], posStart)}
}

main = function:: i64; entry {
    patternAB = 
        {Sequence(), 
          {{ZeroOrMore(), {Text(), "a"}}, 
            {Text(), "b"}}} :: undefType; i12n(on).

            
//    matchers = ["The ", "only ", "way "] :: [string]; i12n(on). 
    match("aaab", patternAB, 0):: i64
}