jsl/json.js

function jsonQuery(json, path, defaultValue = null) {

    let toks = tokenizePath(path);
    let ptr = json;
    let search = null;
    let searchTok = null;
    let multiResult = null;

    let tok;
    while (tok = toks.shift()) {
        switch (tok) {
            case ".": // find key
                search = 'key';
                break;
            case "[": // find array index
                search = "array";
                break;
            case "]": // find 
                // if searchTok is "", match all items
                if (search !== "array") {
                    throw new Error("Invalid path");
                }
                if (searchTok === null) {
                    if (multiResult !== null) {
                        throw new Error("Can't match full arrays on multiple levels");
                    }
                    multiResult = [];
                    ptr.forEach(item => {
                        let res = jsonQuery(item, toks.join(""));
                        multiResult.push(res);
                    });
                    return multiResult;
                }
                if (typeof ptr[searchTok] === 'undefined') {
                    return defaultValue;
                }
                ptr = ptr[searchTok];
                break;
            default:
                if (search === 'key') {
                    // find key tok in ptr
                    if (typeof ptr[tok] === 'undefined') {
                        return defaultValue;
                    } else {
                        ptr = ptr[tok];
                    }
                } else if (search  === 'array') {
                    // find index tok in ptr after finding a ]
                    searchTok = tok;
                }
        }
    }
    return ptr;
}

function jsonPatch(json, path, value) {
    let toks = tokenizePath(path);
    json = structuredClone(json);
    let ptr = json;
    let search = null;
    let searchTok = null;
    let multiResult = null;

    let tok;
    while (tok = toks.shift()) {
        switch (tok) {
            case ".": // find key
                search = 'key';
                break;
            case "[": // find array index
                search = "array";
                break;
            case "]": // find 
                // if searchTok is "", match all items
                if (search !== "array") {
                    throw new Error("Invalid path");
                }
                if (searchTok === null) {
                    throw new Error("Can't patch arrays yet");
                }
                if (typeof ptr[searchTok] === 'undefined') {
                    return json;
                }
                ptr = ptr[searchTok];
                break;
            default:
                if (search === 'key') {
                    // find key tok in ptr
                    if (typeof ptr[tok] === 'undefined') {
                        if (toks.length === 0) {
                            ptr[tok] = value;
                            return json;
                        } else {
                            ptr[tok] = {};
                            ptr = ptr[tok];
                        }
                    } else {
                        if (toks.length === 0) {
                            ptr[tok] = value;
                            return json;
                        } else {
                            ptr = ptr[tok];
                        }
                    }
                } else if (search  === 'array') {
                    // find index tok in ptr after finding a ]
                    searchTok = tok;
                }
        }
    }
    // ptr = value;

    return json;
}

function tokenizePath(path) {
    let t = [];
    let b = null;
    for (let p = 0; p < path.length; p++) {
        let c = path[p];
        if (c == ".") {
            if (b !== null) t.push(b);
            b = null;
            t.push(".");
        } else if (c == "[") {
            if (b !== null) t.push(b);
            b = null;
            t.push("[");
        } else if (c == "]") {
            if (b !== null) t.push(b);
            b = null;
            t.push("]");
        } else {
            b = ((b===null)?"":b) + c;
        }
    }
    if (b !== null) t.push(b);
    return t;
}


export {
    tokenizePath,
    jsonQuery,
    jsonPatch,
};