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::undef; interpretation(force), posStart::i64):: i64; interpretation(suppress){
    textLength = length(text):: i64.
    
    loop fold(pattern-> matcher:: undef, posStart->pos):: i64{
        recognizedSymbols = match(text, matcher, pos):: i64.
               
        if (recognizedSymbols > 0):: i64{
            pos+recognizedSymbols
            
        } else {
            pos:: i64; break
        }
    }
}

matchZeroOrMore= function(text::string, matcher::undef; interpretation(force), posStart::i64):: i64; interpretation(suppress){   
    textLength = length(text):: i64.
    
    loop fold inf(posStart->pos):: i64{
        recognizedSymbols = match(text, matcher, pos):: i64.
        
        if (recognizedSymbols > 0):: i64{
            pos+recognizedSymbols
            
        } else {
            pos:: i64; break
        }
    }
}

match = function(text::string, pattern::undef; interpretation(force), posStart::i64)::i64; interpretation(suppress){

    switch (pattern[0]) :: int
        case (Sequence) {matchSequence(text, pattern[1], posStart)}
        case (ZeroOrMore) {matchZeroOrMore(text, pattern[1], posStart)}
        case (Text) {matchText(text, pattern[1], posStart)}
        case default {-1}
}

main = function:: i64; entry {
    patternAB = 
        [Sequence, 
            [[ZeroOrMore, [Text, "a"]], 
            [Text, "b"]]] :: undef; interpretation(force).

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