/*******************************************************************************

    uBlock Origin - a comprehensive, efficient content blocker
    Copyright (C) 2025-present Raymond Hill

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see {http://www.gnu.org/licenses/}.

    Home: https://github.com/gorhill/uBlock

*/

/**
 * Implement the parsing of uBO-flavored JSON path queries.
 * 
 * Reference to original JSON path syntax:
 * https://www.rfc-editor.org/info/rfc9535/
 * 
 * uBO-flavored JSON path implementation differs as follow:
 *   - Array slice operator not supported
 *   - Selectors can be a `/`-delimited regex, i.e. `$./pattern/`
 *   - Onle a single filter selector is allowed in filter selector syntax
 * 
 * - uBO-flavored JSON path supports a limited set of filter selectors:
 *   set of expressions since unlike the official implementation, uBO can't use
 *   JS eval() to evaluate arbitrary JS expressions. The operand MUST be valid
 *   JSON. The currently supported expressions are:
 *   - ==: strict equality
 *   - !=: strict inequality
 *   -  <: less than
 *   - <=: less than or equal to
 *   -  >: greater than
 *   - >=: greater than or equal to
 *   - ^=: stringified value starts with 
 *   - $=: stringified value ends with
 *   - *=: stringified value includes
 *   - =/.../: true if the regular expression matches the stringified value
 * 
 * - uBO-flavored JSON path supports assignement operator:
 *   - =[any well-formed JSON value]
 *   - =repl(...): [to be documented] i.e. {"regex":"...","flags":"i","replacement":"..."}
 *   - =call(...): [to be documented] i.e. ["${obj}","setAttribute","${key}"]
 *  * 
 * - Examples (from "JSONPath examples" at reference link)
 *   - .store.book[*].author
 *   - ..author
 *   - .store.*
 *   - .store..price
 *   - ..book[2]
 *   - ..book[?(.isbn)]
 *   - ..book[?(.price<10)]
 *   - ..*
 * 
 * uBO-flavored syntax supports assigning a value to a resolved JSON path by
 * appending `=[value]` to the JSON path query. The assigned value MUST be
 * valid JSON. Examples:
 * - .store..price=0
 * - .store.book[*].author="redacted"
 *
 * A JSONPath instance can be use to compile a JSON path query, and the result
 * of the compilation can be applied to different objects. When a JSON path
 * query does not assign a value, the resolved property will be removed.
 * 
 * More capabilities can be added in the future as needed.
 * 
 * */

export class JSONPath {
    static create(query) {
        const jsonp = new JSONPath();
        jsonp.compile(query);
        return jsonp;
    }
    static toJSON(obj, stringifier, ...args) {
        return (stringifier || JSON.stringify)(obj, ...args)
            .replace(/\//g, '\\/');
    }
    static keys = Object.keys;
    static entries = Object.entries;
    static hasOwn = Object.hasOwn;
    static Regex = RegExp;
    get value() {
        return this.#compiled && this.#compiled.rval;
    }
    set value(v) {
        if ( this.#compiled === undefined ) { return; }
        this.#compiled.rval = v;
    }
    get valid() {
        return this.#compiled !== undefined;
    }
    compile(query) {
        this.#compiled = undefined;
        const v2 = query.startsWith('v2:');
        if ( v2 ) { query = query.slice(3); }
        const r = this.#compile(query, 0);
        if ( r === undefined ) { return; }
        if ( r.i !== query.length ) {
            let val;
            if ( query.startsWith('=', r.i) ) {
                const match = this.#reRval.exec(query.slice(r.i));
                if ( match ) {
                    r.modify = match[1];
                    val = match[2];
                } else {
                    val = query.slice(r.i+1);
                }
            } else if ( query.startsWith('+=', r.i) ) {
                r.modify = '+';
                val = query.slice(r.i+2);
            }
            try { r.rval = JSON.parse(val); }
            catch { return; }
        }
        r.v2 = v2;
        this.#compiled = r;
    }
    evaluate(root) {
        if ( this.valid === false ) { return []; }
        this.#root = { '$': root };
        const paths = this.#evaluate(this.#compiled.steps, []);
        this.#root = null;
        return paths;
    }
    apply(root) {
        if ( this.valid === false ) { return; }
        const { rval } = this.#compiled;
        this.#root = { '$': root };
        const paths = this.#evaluate(this.#compiled.steps, []);
        let i = paths.length
        if ( i === 0 ) { this.#root = null; return; }
        while ( i-- ) {
            const { obj, key } = this.#resolvePath(paths[i]);
            if ( obj === undefined ) { continue; }
            if ( rval !== undefined ) {
                this.#modifyVal(obj, key);
            } else if ( Array.isArray(obj) && typeof key === 'number' ) {
                obj.splice(key, 1);
            } else {
                delete obj[key];
            }
        }
        const result = this.#root['$'] ?? null;
        this.#root = null;
        return result;
    }
    dump() {
        return JSON.stringify(this.#compiled);
    }
    toJSON(obj, ...args) {
        return JSONPath.toJSON(obj, null, ...args)
    }
    get [Symbol.toStringTag]() {
        return 'JSONPath';
    }
    #UNDEFINED = 0;
    #ROOT = 1;
    #CURRENT = 2;
    #CHILDREN = 3;
    #DESCENDANTS = 4;
    #QUANTIFIER = 5;
    #reUnquotedIdentifier = /^[A-Za-z_][\w]*|^\*/;
    #reExpr = /^\s*([!=^$*]=|[<>]=?)\s*(.+?)\]/;
    #reIndice = /^-?\d+/;
    #reRval = /^=([a-z]+)\((.+)\)$/;
    #reQuantifier = /^\{(\d+|\d+,\d+|\d+,|,\d+)\};\$/;
    #root;
    #compiled;
    #compile(query, i) {
        if ( query.length === 0 ) { return; }
        const steps = [];
        let c = query.charCodeAt(i);
        if ( c === 0x24 /* $ */ ) {
            steps.push({ mv: this.#ROOT });
            i += 1;
        } else if ( c === 0x40 /* @ */ ) {
            steps.push({ mv: this.#CURRENT });
            i += 1;
        } else {
            steps.push({ mv: i === 0 ? this.#ROOT : this.#CURRENT });
        }
        let mv = this.#UNDEFINED;
        for (;;) {
            if ( i === query.length ) { break; }
            c = query.charCodeAt(i);
            if ( c === 0x20 /* whitespace */ ) {
                i += 1;
                continue;
            }
            // Dot accessor syntax
            if ( c === 0x2E /* . */ ) {
                if ( mv !== this.#UNDEFINED ) { return; }
                if ( query.startsWith('..', i) ) {
                    mv = this.#DESCENDANTS;
                    i += 2;
                } else {
                    mv = this.#CHILDREN;
                    i += 1;
                }
                continue;
            }
            if ( c === 0x3B /* ; */ ) {
                if ( query.startsWith(';$', i) === false ) { return; }
                steps.push(
                    { mv: this.#QUANTIFIER, min: 1, max: 1e6 },
                    { mv: this.#ROOT }
                );
                i += 2;
                mv = this.#UNDEFINED;
                continue;
            }
            if ( c === 0x7B /* { */ ) {
                const match = this.#reQuantifier.exec(query.slice(i));
                if ( match === null ) { return; }
                const comma = match[1].indexOf(',');
                let min, max;
                if ( comma === -1 ) {
                    min = max = parseInt(match[1]);
                } else {
                    min = parseInt(match[1].slice(0, comma)) || 0;
                    max = parseInt(match[1].slice(comma+1)) || 1e6;
                }
                steps.push(
                    { mv: this.#QUANTIFIER, min, max },
                    { mv: this.#ROOT }
                );
                i += match[0].length;
                mv = this.#UNDEFINED;
                continue;
            }
            if ( c !== 0x5B /* [ */ ) {
                if ( mv === this.#UNDEFINED ) {
                    const step = steps.at(-1);
                    if ( step === undefined ) { return; }
                    const j = this.#compileExpr(query, step, i);
                    if ( j ) { i = j; }
                    break;
                }
                const r = this.#consumeUnquotedIdentifier(query, i);
                if  ( r === undefined ) { return; }
                steps.push({ mv, k: r.s });
                i = r.i;
                mv = this.#UNDEFINED;
                continue;
            }
            // Bracket accessor syntax
            if ( query.startsWith('[?', i) ) {
                const not = query.charCodeAt(i+2) === 0x21 /* ! */ ? 1 : 0;
                const j = i + 2 + not;
                const r = this.#compile(query, j);
                if ( r === undefined ) { return; }
                if ( query.startsWith(']', r.i) === false ) { return; }
                if ( not ) { r.steps.at(-1).not = true; }
                steps.push({ mv: mv || this.#CHILDREN, steps: r.steps });
                i = r.i + 1;
                mv = this.#UNDEFINED;
                continue;
            }
            if ( query.startsWith('[*]', i) ) {
                mv ||= this.#CHILDREN;
                steps.push({ mv, k: '*' });
                i += 3;
                mv = this.#UNDEFINED;
                continue;
            }
            const r = this.#consumeIdentifier(query, i+1);
            if ( r === undefined ) { return; }
            mv ||= this.#CHILDREN;
            steps.push({ mv, k: r.s });
            i = r.i + 1;
            mv = this.#UNDEFINED;
        }
        if ( steps.length === 0 ) { return; }
        if ( mv !== this.#UNDEFINED ) { return; }
        return { steps, i };
    }
    #evaluate(steps, pathin) {
        let resultset = [];
        if ( Array.isArray(steps) === false ) { return resultset; }
        for ( const step of steps ) {
            switch ( step.mv ) {
            case this.#ROOT:
                resultset = [ [ '$' ] ];
                break;
            case this.#CURRENT:
                if ( step.op ) {
                    const { obj, key } = this.#resolvePath(pathin);
                    if ( obj === undefined ) { return []; }
                    const outcome = this.#evaluateExpr(step, obj, key);
                    if ( outcome !== true ) { break; }
                }
                resultset = [ pathin ];
                break;
            case this.#CHILDREN:
            case this.#DESCENDANTS: {
                if ( resultset.length === 0 ) { break; }
                resultset = this.#getMatches(resultset, step);
                break;
            }
            case this.#QUANTIFIER: {
                const { length } = resultset;
                if ( length < step.min || length > step.max ) { return []; }
                resultset = [];
                break;
            }
            default:
                break;
            }
        }
        return resultset;
    }
    #getMatches(listin, step) {
        const listout = [];
        for ( const pathin of listin ) {
            const { value: owner } = this.#resolvePath(pathin);
            if ( owner === undefined ) { continue; }
            if ( step.steps ) {
                this.#getMatchesFromExpr(pathin, step, owner, listout);
                continue;
            }
            const iter = this.#expandKey(owner, step.k);
            if ( iter ) {
                for ( const k of iter ) {
                    const outcome = this.#evaluateExpr(step, owner, k);
                    if ( outcome !== true ) { continue; }
                    listout.push([ ...pathin, k ]);
                }
            }
            if ( step.mv !== this.#DESCENDANTS ) { continue; }
            for ( const { obj, key, path } of this.#getDescendants(owner, true) ) {
                const iter = this.#expandKey(obj[key], step.k);
                if ( iter === undefined ) { continue; }
                for ( const k of iter ) {
                    const outcome = this.#evaluateExpr(step, obj[key], k);
                    if ( outcome !== true ) { continue; }
                    listout.push([ ...pathin, ...path, k ]);
                }
            }
        }
        return listout;
    }
    #expandKey(owner, k) {
        if ( typeof owner !== 'object' ) { return; }
        if ( Array.isArray(k) ) {
            const out = [];
            for ( const a of k ) {
                const iter = this.#expandKey(owner, a);
                if ( iter === undefined ) { continue; }
                out.push(...iter);
            }
            return out;
        }
        if ( typeof k === 'number' ) {
            if ( Array.isArray(owner) === false ) { return; }
            return [ k >= 0 ? k : owner.length + k ];
        }
        if ( k === '*' ) {
            if ( Array.isArray(owner) ) { return owner.keys(); }
            return JSONPath.keys(owner);
        }
        if ( k instanceof JSONPath.Regex ) {
            const out = [];
            for ( const key of JSONPath.keys(owner) ) {
                if ( k.test(key) === false ) { continue; }
                out.push(key);
            }
            return out;
        }
        return [ k ];
    }
    #getMatchesFromExpr(pathin, step, owner, out) {
        const recursive = step.mv === this.#DESCENDANTS;
        const v2 = this.#compiled.v2 || recursive || Array.isArray(owner);
        for ( const { path } of this.#getDescendants(owner, recursive) ) {
            const q = v2 ? [ ...pathin, ...path ] : pathin;
            const r = this.#evaluate(step.steps, q);
            if ( Boolean(r?.length) === false ) { continue; }
            out.push(q);
            if ( v2 === false ) { break; }
        }
    }
    #getDescendants(v, recursive) {
        const iterator = {
            next() {
                const n = this.stack.length;
                if ( n === 0 ) {
                    this.value = undefined;
                    this.done = true;
                    return this;
                }
                const details = this.stack[n-1];
                const entry = details.keys.next();
                if ( entry.done ) {
                    this.stack.pop();
                    this.path.pop();
                    return this.next();
                }
                this.path[n-1] = entry.value;
                this.value = {
                    obj: details.obj,
                    key: entry.value,
                    path: this.path.slice(),
                };
                const v = this.value.obj[this.value.key];
                if ( recursive ) {
                    if ( Array.isArray(v) ) {
                        this.stack.push({ obj: v, keys: v.keys() });
                    } else if ( typeof v === 'object' && v !== null ) {
                        this.stack.push({ obj: v, keys: JSONPath.keys(v).values() });
                    }
                }
                return this;
            },
            path: [],
            value: undefined,
            done: false,
            stack: [],
            [Symbol.iterator]() { return this; },
        };
        if ( Array.isArray(v) ) {
            iterator.stack.push({ obj: v, keys: v.keys() });
        } else if ( typeof v === 'object' && v !== null ) {
            iterator.stack.push({ obj: v, keys: JSONPath.keys(v).values() });
        }
        return iterator;
    }
    #consumeIdentifier(query, i) {
        const keys = [];
        for (;;) {
            const c0 = query.charCodeAt(i);
            if ( c0 === 0x5D /* ] */ ) { break; }
            if ( c0 === 0x2C /* , */ || c0 === 0x20 /* SPACE */) {
                i += 1;
                continue;
            }
            if ( c0 === 0x22 /* " */ || c0 === 0x27 /* ' */ ) {
                const r = this.#untilChar(query, c0, i+1);
                if ( r === undefined ) { return; }
                keys.push(r.s);
                i = r.i;
                continue;
            }
            if ( c0 === 0x2D /* - */ || c0 >= 0x30 && c0 <= 0x39 ) {
                const match = this.#reIndice.exec(query.slice(i));
                if ( match === null ) { return; }
                const indice = parseInt(query.slice(i), 10);
                keys.push(indice);
                i += match[0].length;
                continue;
            }
            const r = this.#consumeUnquotedIdentifier(query, i);
            if ( r === undefined ) { return; }
            keys.push(r.s);
            i = r.i;
        }
        return { s: keys.length === 1 ? keys[0] : keys, i };
    }
    #consumeUnquotedIdentifier(query, i) {
        if ( query.charCodeAt(i) === 0x2F /* / */ ) {
            const r = this.#untilChar(query, 0x2F, i+1);
            if ( r === undefined ) { return; }
            let re;
            try { re = new JSONPath.Regex(r.s); } catch { return; }
            return { s: re, i: r.i };
        }
        const match = this.#reUnquotedIdentifier.exec(query.slice(i));
        if ( match === null ) { return; }
        return { s: match[0], i: i + match[0].length };
    }
    #untilChar(query, targetCharCode, i) {
        const len = query.length;
        const parts = [];
        let beg = i, end = i;
        for (;;) {
            if ( end === len ) { return; }
            const c = query.charCodeAt(end);
            if ( c === targetCharCode ) {
                parts.push(query.slice(beg, end));
                end += 1;
                break;
            }
            if ( c === 0x5C /* \ */ && (end+1) < len ) {
                const d = query.charCodeAt(end+1);
                if ( d === targetCharCode ) {
                    parts.push(query.slice(beg, end));
                    end += 1;
                    beg = end;
                }
            }
            end += 1;
        }
        return { s: parts.join(''), i: end };
    }
    #compileExpr(query, step, i) {
        if ( query.startsWith('=/', i) ) {
            const r = this.#untilChar(query, 0x2F /* / */, i+2);
            if ( r === undefined ) { return i; }
            const match = /^[i]/.exec(query.slice(r.i));
            try {
                step.rval = new JSONPath.Regex(r.s, match && match[0] || undefined);
            } catch { return; }
            step.op = 're';
            if ( match ) { r.i += match[0].length; }
            return r.i;
        }
        const match = this.#reExpr.exec(query.slice(i));
        if ( match === null ) { return; }
        const op = match[1], rval = match[2];
        if ( rval.charCodeAt(0) === 0x27 /* ' */ ) {
            const r = this.#untilChar(rval, 0x27, 1);
            if ( r === undefined ) { return; }
            step.rval = r.s;
            step.op = op;
        } else {
            try {
                step.rval = JSON.parse(rval);
                step.op = op;
            } catch { return; }
        }
        return i + match[0].length - 1;
    }
    #resolvePath(path) {
        if ( path.length === 0 ) { return { value: this.#root }; }
        const key = path.at(-1);
        let obj = this.#root
        for ( let i = 0, n = path.length-1; i < n; i++ ) {
            obj = obj[path[i]];
            if ( obj instanceof Object === false ) { return {}; }
        }
        return { obj, key, value: obj[key] };
    }
    #evaluateExpr(step, owner, k) {
        if ( owner === undefined || owner === null ) { return; }
        const hasOwn = owner[k] !== undefined || JSONPath.hasOwn(owner, k);
        if ( step.op !== undefined && hasOwn === false ) { return; }
        const target = step.not !== true;
        const v = owner[k];
        switch ( step.op ) {
        case '==': return (v === step.rval) === target;
        case '!=': return (v !== step.rval) === target;
        case  '<': return (v < step.rval) === target;
        case '<=': return (v <= step.rval) === target;
        case  '>': return (v > step.rval) === target;
        case '>=': return (v >= step.rval) === target;
        case '^=': return `${v}`.startsWith(step.rval) === target;
        case '$=': return `${v}`.endsWith(step.rval) === target;
        case '*=': return `${v}`.includes(step.rval) === target;
        case 're': return step.rval.test(`${v}`);
        default: break;
        }
        return hasOwn === target;
    }
    #modifyVal(obj, key) {
        let { modify, rval } = this.#compiled;
        if ( typeof rval === 'string' ) {
            rval = rval.replace('${now}', `${Date.now()}`);
        }
        switch ( modify ) {
        case undefined:
            obj[key] = rval;
            break;
        case '+': {
            if ( rval instanceof Object === false ) { return; }
            const lval = obj[key];
            if ( lval instanceof Object === false ) { return; }
            if ( Array.isArray(lval) ) { return; }
            for ( const [ k, v ] of JSONPath.entries(rval) ) {
                lval[k] = v;
            }
            break;
        }
        case 'call': {
            const entries = rval.slice();
            if ( entries.length < 2 ) { break; }
            entries.forEach((a, i, aa) => {
                if ( a === '${obj}' ) { aa[i] = obj; }
                else if ( a === '${key}' ) { aa[i] = key; }
                else if ( a === '${val}' ) { aa[i] = obj[key]; }
            });
            const instance = entries[0] ?? self;
            instance[entries[1]](...entries.slice(2));
            break;
        }
        case 'repl': {
            const lval = obj[key];
            if ( typeof lval !== 'string' ) { return; }
            if ( this.#compiled.re === undefined ) {
                this.#compiled.re = null;
                try {
                    this.#compiled.re = rval.regex !== undefined
                        ? new JSONPath.Regex(rval.regex, rval.flags)
                        : new JSONPath.Regex(rval.pattern.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'));
                } catch { }
            }
            if ( this.#compiled.re === null ) { return; }
            obj[key] = lval.replace(this.#compiled.re, rval.replacement);
            break;
        }
        default:
            break;
        }
    }
}
