/**
 * WYSIWYG fuzz test.
 *
 * Generates random keystroke sequences, types them char-by-char,
 * and checks structural invariants after every keystroke. When a
 * failure is found, the seed is logged for deterministic replay
 * and the sequence is shrunk to a minimal reproducing case.
 *
 * Run:
 *   node test/integration/test_fuzz.js
 *   node test/integration/test_fuzz.js --seed 12345
 *   node test/integration/test_fuzz.js --rounds 200
 *   node test/integration/test_fuzz.js --seed 12345 --shrink
 */
const { Builder, By, Key } = require('selenium-webdriver');
const firefox = require('selenium-webdriver/firefox');
const { createServer } = require('./server');

let server, driver;
const DELAY = 20;

/* ── Seeded PRNG (mulberry32) ── */

function mulberry32(seed) {
    return function () {
        seed |= 0;
        seed = (seed + 0x6d2b79f5) | 0;
        let t = Math.imul(seed ^ (seed >>> 15), 1 | seed);
        t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
        return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
    };
}

/* ── Keystroke generation ── */

const PRINTABLE = 'abcdefghijklmnopqrstuvwxyz 0123456789.,!?';
const DELIMITERS = ['*', '**', '***', '`', '~~', '_', '__', '___'];
const BLOCK_PREFIXES = ['# ', '## ', '### ', '- ', '+ ', '1. ', '> ', '---', '~~~'];
const SPECIAL_KEYS = [
    { name: 'Enter', keys: Key.ENTER, isSpecial: true },
    { name: 'Backspace', keys: Key.BACK_SPACE, isSpecial: true },
    { name: 'ArrowLeft', keys: Key.ARROW_LEFT, isSpecial: true },
    { name: 'ArrowRight', keys: Key.ARROW_RIGHT, isSpecial: true },
];

/**
 * Generate a random keystroke sequence.
 * Returns array of { name, keys } where keys is a string or Key constant.
 */
function generateSequence(random, length) {
    const sequence = [];
    for (let i = 0; i < length; i++) {
        const roll = random();
        if (roll < 0.50) {
            /* printable character */
            const character = PRINTABLE[Math.floor(random() * PRINTABLE.length)];
            sequence.push({ name: character === ' ' ? 'Space' : character, keys: character });
        } else if (roll < 0.70) {
            /* delimiter */
            const delimiter = DELIMITERS[Math.floor(random() * DELIMITERS.length)];
            sequence.push({ name: delimiter, keys: delimiter });
        } else if (roll < 0.80) {
            /* special key */
            const special = SPECIAL_KEYS[Math.floor(random() * SPECIAL_KEYS.length)];
            sequence.push(special);
        } else if (roll < 0.88) {
            /* block prefix (only useful at line start, but fuzz doesn't care) */
            const prefix = BLOCK_PREFIXES[Math.floor(random() * BLOCK_PREFIXES.length)];
            sequence.push({ name: `"${prefix.trim()}"`, keys: prefix });
        } else if (roll < 0.94) {
            /* repeated delimiter (stress test) */
            const count = 2 + Math.floor(random() * 4);
            const delimiters = ['*', '_', '~'];
            const character = delimiters[Math.floor(random() * delimiters.length)];
            sequence.push({ name: character.repeat(count), keys: character.repeat(count) });
        } else if (roll < 0.97) {
            /* backslash sequences */
            const escaped = ['\\*', '\\_', '\\`', '\\~', '\\\\', '\\'];
            const fragment = escaped[Math.floor(random() * escaped.length)];
            sequence.push({ name: fragment, keys: fragment });
        } else {
            /* angle bracket / HTML-like content */
            const fragments = ['<', '>', '<div>', '</div>', '<b>', '&amp;'];
            const fragment = fragments[Math.floor(random() * fragments.length)];
            sequence.push({ name: fragment, keys: fragment });
        }
    }
    return sequence;
}

/* ── Invariant checks ── */

/**
 * Valid direct children of the editor element.
 * Everything the WYSIWYG produces must be one of these.
 */
const VALID_BLOCK_TAGS = new Set([
    'P', 'H1', 'H2', 'H3', 'H4', 'H5', 'H6',
    'UL', 'OL', 'BLOCKQUOTE', 'PRE', 'HR', 'TABLE',
]);

/**
 * Valid inline elements that can appear inside block content.
 */
const VALID_INLINE_TAGS = new Set([
    'STRONG', 'B', 'EM', 'I', 'CODE', 'A', 'BR',
]);

/**
 * Elements that can only contain specific children.
 */
const REQUIRED_CHILDREN = {
    'UL': ['LI'],
    'OL': ['LI'],
    'TABLE': ['THEAD', 'TBODY', 'TR', 'CAPTION', 'COLGROUP'],
    'THEAD': ['TR'],
    'TBODY': ['TR'],
    'TR': ['TH', 'TD'],
};

/**
 * Elements that must not contain certain descendants.
 */
const FORBIDDEN_NESTING = {
    'LI': ['TABLE'],
    'A': ['A'],
    'STRONG': ['STRONG', 'B'],
    'B': ['STRONG', 'B'],
    'EM': ['EM', 'I'],
    'I': ['EM', 'I'],
    'CODE': ['CODE', 'STRONG', 'B', 'EM', 'I', 'A'],
};

/**
 * Run all invariant checks on the current editor state.
 * Returns null if all pass, or a string describing the violation.
 */
async function checkInvariants() {
    return driver.executeScript(function () {
        var editor = document.getElementById('ribbit');
        if (!editor) { return 'Editor element not found'; }
        if (editor.contentEditable !== 'true') { return 'contentEditable is not true'; }

        /* Invariant 1: all direct children are valid block elements */
        for (var i = 0; i < editor.childNodes.length; i++) {
            var child = editor.childNodes[i];
            if (child.nodeType === 3) {
                if (child.textContent.replace(/[\u200B\s]/g, '').length > 0) {
                    return 'Bare text node in editor: "' + child.textContent.slice(0, 40) + '"';
                }
                continue;
            }
            if (child.nodeType !== 1) { continue; }
            var validBlocks = ['P','H1','H2','H3','H4','H5','H6','UL','OL','BLOCKQUOTE','PRE','HR','TABLE'];
            if (validBlocks.indexOf(child.nodeName) === -1) {
                return 'Invalid block element: <' + child.nodeName.toLowerCase() + '>';
            }
        }

        /* Invariant 2: no nested speculative elements */
        var specs = editor.querySelectorAll('[data-speculative]');
        for (var s = 0; s < specs.length; s++) {
            if (specs[s].querySelector('[data-speculative]')) {
                return 'Nested speculative elements';
            }
        }

        /* Invariant 3: required children (UL must contain LI, etc.) */
        var parentChildRules = {
            'UL': ['LI'], 'OL': ['LI'],
            'TABLE': ['THEAD','TBODY','TR','CAPTION','COLGROUP'],
            'THEAD': ['TR'], 'TBODY': ['TR'], 'TR': ['TH','TD'],
        };
        function checkChildren(element) {
            var allowed = parentChildRules[element.nodeName];
            if (!allowed) { return null; }
            for (var c = 0; c < element.children.length; c++) {
                if (allowed.indexOf(element.children[c].nodeName) === -1) {
                    return '<' + element.children[c].nodeName.toLowerCase() +
                        '> inside <' + element.nodeName.toLowerCase() +
                        '> (allowed: ' + allowed.join(', ') + ')';
                }
            }
            for (var c = 0; c < element.children.length; c++) {
                var result = checkChildren(element.children[c]);
                if (result) { return result; }
            }
            return null;
        }
        var childViolation = checkChildren(editor);
        if (childViolation) { return 'Invalid nesting: ' + childViolation; }

        /* Invariant 4: forbidden nesting (no <strong> inside <strong>, etc.) */
        var forbiddenRules = {
            'STRONG': ['STRONG','B'], 'B': ['STRONG','B'],
            'EM': ['EM','I'], 'I': ['EM','I'],
            'CODE': ['CODE','STRONG','B','EM','I','A','DEL'],
            'DEL': ['DEL','S','STRIKE'], 'S': ['DEL','S','STRIKE'], 'STRIKE': ['DEL','S','STRIKE'],
            'A': ['A'],
        };
        var allElements = editor.querySelectorAll('*');
        for (var e = 0; e < allElements.length; e++) {
            var el = allElements[e];
            var forbidden = forbiddenRules[el.nodeName];
            if (!forbidden) { continue; }
            for (var f = 0; f < forbidden.length; f++) {
                if (el.querySelector(forbidden[f].toLowerCase() + ',' + forbidden[f])) {
                    return 'Forbidden nesting: <' + forbidden[f].toLowerCase() +
                        '> inside <' + el.nodeName.toLowerCase() + '>';
                }
            }
        }

        /* Invariant 5: getMarkdown() must not throw */
        try {
            window.__ribbitEditor.getMarkdown();
        } catch (err) {
            return 'getMarkdown() threw: ' + err.message;
        }

        /* Invariant 6: rendered HTML is stable through markdown round-trip.
           md → toHTML → toMarkdown → toHTML must eventually stabilize.
           The first round-trip may change the HTML (e.g. literal <strong>
           in text becomes a real element via HTML passthrough, then
           serializes as **). But the second round-trip must be stable.
           Skip if there are speculative elements (in-progress editing). */
        var hasSpeculative = editor.querySelector('[data-speculative]');
        if (!hasSpeculative) {
            try {
                var md = window.__ribbitEditor.getMarkdown();
                var converter = window.__ribbitEditor.converter;
                // Two round-trips: allow the first to normalize, check
                // that the second produces identical HTML
                var html1 = converter.toHTML(md);
                var md2 = converter.toMarkdown(html1);
                var html2 = converter.toHTML(md2);
                var md3 = converter.toMarkdown(html2);
                var html3 = converter.toHTML(md3);
                var normalize = function(html) {
                    return html
                        .replace(/\s*id='[^']*'/g, '')
                        .replace(/\s+/g, ' ')
                        .trim();
                };
                if (normalize(html2) !== normalize(html3)) {
                    return 'Round-trip HTML not stable after 2 passes:\n  pass2: "' + normalize(html2).slice(0, 80) +
                        '"\n  pass3: "' + normalize(html3).slice(0, 80) + '"';
                }
            } catch (err) {
                return 'Round-trip check threw: ' + err.message;
            }
        }

        /* Invariant 7: only valid inline elements inside block content */
        var validInline = ['STRONG','B','EM','I','CODE','A','BR','DEL','S','STRIKE'];
        var blocks = editor.querySelectorAll('p,h1,h2,h3,h4,h5,h6,li,blockquote,td,th');
        for (var b = 0; b < blocks.length; b++) {
            var inlineEls = blocks[b].querySelectorAll('*');
            for (var ie = 0; ie < inlineEls.length; ie++) {
                var inEl = inlineEls[ie];
                /* Skip nested block elements (blockquote can contain blocks) */
                if (inEl.parentElement !== blocks[b] && inEl.closest('blockquote,ul,ol,table,pre') !== blocks[b]) {
                    continue;
                }
                if (validInline.indexOf(inEl.nodeName) === -1 &&
                    ['P','H1','H2','H3','H4','H5','H6','UL','OL','BLOCKQUOTE','PRE','HR','TABLE','LI','THEAD','TBODY','TR','TH','TD','CAPTION','COLGROUP'].indexOf(inEl.nodeName) === -1) {
                    return 'Invalid inline element <' + inEl.nodeName.toLowerCase() +
                        '> inside <' + blocks[b].nodeName.toLowerCase() + '>';
                }
            }
        }

        return null;
    });
}

/* ── Test runner ── */

async function setup() {
    server = createServer(9996);
    await server.start();
    const options = new firefox.Options().addArguments('--headless');
    driver = await new Builder().forBrowser('firefox').setFirefoxOptions(options).build();
    await driver.get(server.url);
    await driver.wait(async () => driver.executeScript('return window.__ribbitReady === true'), 10000);
}

async function teardown() {
    if (driver) { await driver.quit(); }
    if (server) { await server.stop(); }
}

async function resetEditor() {
    await driver.executeScript(`
        var e = window.__ribbitEditor;
        e.wysiwyg();
        e.element.innerHTML = '<p><br></p>';
    `);
    await driver.findElement(By.id('ribbit')).click();
    await driver.sleep(50);
}

async function typeKeystroke(keystroke) {
    const keys = keystroke.keys;
    if (typeof keys !== 'string') {
        throw new Error('Invalid keystroke: ' + JSON.stringify(keystroke));
    }
    if (keys.length === 1 || keystroke.isSpecial) {
        await driver.actions().sendKeys(keys).perform();
        await driver.sleep(DELAY);
    } else {
        /* Multi-char string: type char by char */
        for (const character of keys) {
            await driver.actions().sendKeys(character).perform();
            await driver.sleep(DELAY);
        }
    }
}

function formatSequence(sequence, upTo) {
    return sequence.slice(0, upTo + 1).map(s => s.name).join(' ');
}

/**
 * Replay a sequence and return the index of the first invariant failure,
 * or -1 if no failure.
 */
async function replaySequence(sequence) {
    await resetEditor();
    for (let i = 0; i < sequence.length; i++) {
        await typeKeystroke(sequence[i]);
        const violation = await checkInvariants();
        if (violation) { return { index: i, violation }; }
    }
    return null;
}

/**
 * Shrink a failing sequence to find the minimal reproducing prefix.
 * Uses binary search on the sequence length.
 */
async function shrinkSequence(sequence, failIndex) {
    let lo = 0;
    let hi = failIndex;
    let bestSequence = sequence.slice(0, failIndex + 1);
    let bestViolation = '';

    while (lo < hi) {
        const mid = Math.floor((lo + hi) / 2);
        const candidate = sequence.slice(0, mid + 1);
        const result = await replaySequence(candidate);
        if (result) {
            hi = mid;
            bestSequence = candidate;
            bestViolation = result.violation;
        } else {
            lo = mid + 1;
        }
    }

    /* Try removing individual keystrokes from the beginning */
    let shrunk = true;
    while (shrunk) {
        shrunk = false;
        for (let i = 0; i < bestSequence.length - 1; i++) {
            const candidate = [...bestSequence.slice(0, i), ...bestSequence.slice(i + 1)];
            const result = await replaySequence(candidate);
            if (result) {
                bestSequence = candidate;
                bestViolation = result.violation;
                shrunk = true;
                break;
            }
        }
    }

    return { sequence: bestSequence, violation: bestViolation };
}

async function runFuzz(options) {
    const { rounds, minLength, maxLength, seed: baseSeed, doShrink } = options;
    let totalKeystrokes = 0;
    let failures = 0;

    console.log(`\nWYSIWYG Fuzz Test — ${rounds} rounds, seed ${baseSeed}\n`);

    for (let round = 0; round < rounds; round++) {
        const roundSeed = baseSeed + round;
        const random = mulberry32(roundSeed);
        const length = minLength + Math.floor(random() * (maxLength - minLength));
        const sequence = generateSequence(random, length);

        await resetEditor();
        let failed = false;

        for (let i = 0; i < sequence.length; i++) {
            await typeKeystroke(sequence[i]);
            const violation = await checkInvariants();

            if (violation) {
                failures++;
                failed = true;
                const html = await driver.executeScript('return document.getElementById("ribbit").innerHTML');

                console.log(`  ✗ Round ${round + 1} [seed=${roundSeed}] — keystroke ${i + 1}/${length}`);
                console.log(`    Invariant: ${violation}`);
                console.log(`    Sequence: ${formatSequence(sequence, i)}`);
                console.log(`    HTML: ${html.slice(0, 200)}`);

                if (doShrink) {
                    console.log(`    Shrinking...`);
                    const shrunk = await shrinkSequence(sequence, i);
                    console.log(`    Minimal (${shrunk.sequence.length} keystrokes): ${shrunk.sequence.map(s => s.name).join(' ')}`);
                    console.log(`    Violation: ${shrunk.violation}`);
                }

                console.log(`    Replay: node test/integration/test_fuzz.js --seed ${roundSeed}\n`);
                break;
            }
        }

        if (!failed) {
            totalKeystrokes += length;
            if ((round + 1) % 10 === 0 || round === rounds - 1) {
                process.stdout.write(`  ✓ ${round + 1}/${rounds} rounds (${totalKeystrokes} keystrokes)\r`);
            }
        }
    }

    console.log(`\n\n${rounds - failures}/${rounds} rounds passed — ${totalKeystrokes} keystrokes checked`);
    if (failures > 0) {
        console.log(`${failures} failure(s) found`);
    }
    return failures;
}

/* ── CLI ── */

function parseArgs() {
    const args = process.argv.slice(2);
    const options = {
        rounds: 50,
        minLength: 20,
        maxLength: 80,
        seed: Date.now() % 100000,
        doShrink: true,
    };
    for (let i = 0; i < args.length; i++) {
        if (args[i] === '--seed' && args[i + 1]) { options.seed = parseInt(args[i + 1]); i++; }
        if (args[i] === '--rounds' && args[i + 1]) { options.rounds = parseInt(args[i + 1]); i++; }
        if (args[i] === '--min' && args[i + 1]) { options.minLength = parseInt(args[i + 1]); i++; }
        if (args[i] === '--max' && args[i + 1]) { options.maxLength = parseInt(args[i + 1]); i++; }
        if (args[i] === '--no-shrink') { options.doShrink = false; }
        if (args[i] === '--shrink') { options.doShrink = true; }
    }
    return options;
}

(async () => {
    const options = parseArgs();
    try {
        await setup();
        const failures = await runFuzz(options);
        process.exitCode = failures > 0 ? 1 : 0;
    } catch (error) {
        console.error('Setup failed:', error.message);
        process.exitCode = 1;
    } finally {
        await teardown();
    }
})();