Nasal-Interpreter/std/json.nas

# lib json.nas
# 2021 ValKmjolnir

var (
    _j_eof, _j_lbrace, _j_rbrace, _j_lbrkt, _j_rbrkt,
    _j_comma, _j_colon, _j_str, _j_num, _j_id
) = (0, 1, 2, 3, 4, 5, 6, 7, 8, 9);

var _j_content = [
    "eof",
    "`{`",
    "`}`",
    "`[`",
    "`]`",
    "`,`",
    "`:`",
    "string",
    "number",
    "identifier"
];

var JSON = func() {

    var text = "";
    var line = 1;
    var text_size = 0;
    var ptr = 0;
    var token = {
        content: "",
        type: ""
    };

    var init = func() {
        text = "";
        line = 1;
        text_size = 0;
        ptr = 0;
        token = {
            content: "",
            type: ""
        };
    }

    var isnum = func(c) {
        return '0'<=c and c<='9';
    }

    var isid = func(c) {
        var tmp = c[0];
        return ('a'[0]<=tmp and tmp<='z'[0]) or
            ('A'[0]<=tmp and tmp<='Z'[0]) or
            c=='_';
    }

    var check = func() {
        var c = char(text[ptr]);
        return (
            c=='{' or c=='}' or
            c=='[' or c==']' or
            c==',' or c==':' or
            c=='\"' or c=='\'' or
            isnum(c) or isid(c)
        );
    }

    var get = func(str) {
        init();
        if (!size(str)) {
            println("JSON.parse: empty string");
            str = "[]";
        }
        text = str;
        text_size = size(text);
        return;
    }

    var next = func() {
        while(ptr<text_size and !check()) {
            if (char(text[ptr])=='\n') {
                line += 1;
            }
            ptr += 1;
        }
        if(ptr>=text_size) {
            token.content = "eof";
            token.type = _j_eof;
            return;
        }
        
        var c = char(text[ptr]);
        if (c=='{') {
            token.content = '{';
            token.type = _j_lbrace;
        } elsif (c=='}') {
            token.content = '}';
            token.type = _j_rbrace;
        } elsif (c=='[') {
            token.content = '[';
            token.type = _j_lbrkt;
        } elsif (c==']') {
            token.content = ']';
            token.type = _j_rbrkt;
        } elsif (c==',') {
            token.content = ',';
            token.type = _j_comma;
        } elsif (c==':') {
            token.content = ':';
            token.type = _j_colon;
        } elsif (c=='\"' or c=='\'') {
            var strbegin = c;
            var s = "";
            ptr += 1;
            while(ptr<text_size and char(text[ptr])!=strbegin) {
                s ~= char(text[ptr]);
                ptr += 1;
                if (char(text[ptr-1])=="\\" and ptr<text_size) {
                    s ~= char(text[ptr]);
                    ptr += 1;
                }
            }
            token.content=s;
            token.type=_j_str;
        } elsif (isnum(c)) {
            var s = c;
            ptr += 1;
            while(ptr<text_size and ((isnum(char(text[ptr])) or char(text[ptr])=='.'))) {
                s ~= char(text[ptr]);
                ptr += 1;
            }
            ptr -= 1;
            token.content = num(s);
            token.type = _j_num;
        } elsif (isid(c)) {
            var s = c;
            ptr += 1;
            while(ptr<text_size and (isid(char(text[ptr])) or isnum(char(text[ptr])))) {
                s ~= char(text[ptr]);
                ptr += 1;
            }
            ptr -= 1;
            token.content = s;
            token.type = _j_id;
        }
        ptr += 1;
        return;
    }

    var match = func(type) {
        if(token.type!=type)
            println("JSON.parse: line ",line,": expect ",_j_content[type]," but get `",token.content,"`.");
        next();
        return;
    }

    var member = func(hash) {
        var name = token.content;
        if(token.type==_j_rbrace) {
            return;
        }
        if(token.type==_j_str) {
            match(_j_str);
        } else {
            match(_j_id);
        }
        match(_j_colon);
        if(token.type==_j_lbrace) {
            hash[name] = hash_gen();
        } elsif(token.type==_j_lbrkt) {
            hash[name] = vec_gen();
        } elsif(token.type==_j_str or token.type==_j_num) {
            hash[name] = token.content;
            next();
        }
        return;
    }

    var hash_gen = func() {
        var hash = {};
        match(_j_lbrace);
        member(hash);
        while(token.type==_j_comma) {
            match(_j_comma);
            member(hash);
        }
        match(_j_rbrace);
        return hash;
    }

    var vec_gen = func() {
        var vec = [];
        match(_j_lbrkt);
        if(token.type==_j_lbrace) {
            append(vec, hash_gen());
        } elsif(token.type==_j_lbrkt) {
            append(vec, vec_gen());
        } elsif(token.type==_j_str or token.type==_j_num) {
            append(vec, token.content);
            next();
        }
        while(token.type==_j_comma) {
            match(_j_comma);
            if(token.type==_j_lbrace) {
                append(vec, hash_gen());
            } elsif(token.type==_j_lbrkt) {
                append(vec, vec_gen());
            } elsif(token.type==_j_str or token.type==_j_num) {
                append(vec, token.content);
                next();
            }
        }
        match(_j_rbrkt);
        return vec;
    }

    return {
        parse:func(str) {
            if(typeof(str)!="str") {
                println("JSON.parse: must use string");
                return [];
            }
            get(str);
            next();

            if (token.type==_j_lbrkt) {
                var res = vec_gen();
            } else {
                var res = hash_gen();
            }

            init();
            return res;
        }
    };
}();

JSON.stringify = func(object) {
    if(typeof(object)!="hash" and typeof(object)!="vec") {
        println("JSON.stringify: must use hashmap or vector");
        return "[]";
    }

    var s = "";
    var gen = func(elem) {
        var t = typeof(elem);
        if(t=="num") {
            s ~= str(elem);
        } elsif(t=="str") {
            s ~= '"'~elem~'"';
        } elsif(t=="vec") {
            vgen(elem);
        } elsif(t=="hash") {
            hgen(elem);
        } else {
            s ~= '"undefined"';
        }
    }

    var vgen = func(v) {
        s ~= "[";
        var vsize = size(v);
        for(var i = 0; i<vsize; i += 1) {
            gen(v[i]);
            if (i!=vsize-1) {
                s~=",";
            }
        }
        s ~= "]";
    }

    var hgen = func(h) {
        s ~= "{";
        var k = keys(h);
        var vsize = size(k);
        for(var i = 0; i<vsize; i += 1) {
            s ~= k[i]~":";
            gen(h[k[i]]);
            if (i!=vsize-1) {
                s ~= ",";
            }
        }
        s ~= "}";
    }

    if (typeof(object)=="vec") {
        vgen(object);
    } else {
        hgen(object);
    }
    return s;
}