// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

/* eslint-disable no-console */

import fs from 'node:fs';
import path from 'node:path';

import chalk from 'chalk';

const MATTERMOST_URL_PATTERN = /https?:\/\/(?:[a-z0-9-]+\.)*mattermost\.com(?:[/?#][^"'\s<>()]*)?/gi;

const PERMALINK_PATTERN = /^https?:\/\/(www\.)?mattermost\.com\/pl\//;

const PUSH_SERVER_PATTERN = /^https?:\/\/(([a-z0-9-]+\.)?push|hpns-[a-z]+)\.mattermost\.com(\/|$)/;
const ROOT_DOMAIN_PATTERN = /^https?:\/\/(www\.)?mattermost\.com\/?$/;

const SOURCE_EXTENSIONS = ['.ts', '.tsx', '.js', '.jsx'];

const DIRECTORIES_TO_SCAN = [
    'channels/src',
    'platform/client/src',
    'platform/components/src',
    'platform/mattermost-redux/src',
];

function getAllSourceFiles(dir, excludeTests = true) {
    const files = [];

    function walk(currentDir) {
        if (!fs.existsSync(currentDir)) {
            return;
        }

        const entries = fs.readdirSync(currentDir, {withFileTypes: true});

        for (const entry of entries) {
            const fullPath = path.join(currentDir, entry.name);

            if (entry.isDirectory()) {
                if (entry.name === 'node_modules' || entry.name === 'dist' || entry.name === 'coverage') {
                    continue;
                }
                walk(fullPath);
            } else if (entry.isFile()) {
                const ext = path.extname(entry.name);
                if (!SOURCE_EXTENSIONS.includes(ext)) {
                    continue;
                }

                if (excludeTests && (entry.name.includes('.test.') || entry.name.includes('.spec.'))) {
                    continue;
                }

                files.push(fullPath);
            }
        }
    }

    walk(dir);
    return files;
}

function extractUrls(filePath) {
    const content = fs.readFileSync(filePath, 'utf-8');
    const matches = content.match(MATTERMOST_URL_PATTERN) || [];

    return matches.map((url) => {
        let cleanUrl = url;
        cleanUrl = cleanUrl.replace(/[',;)}\]]+$/, '');
        cleanUrl = cleanUrl.replace(/\\n$/, '');
        return cleanUrl;
    });
}

function findAllMattermostUrls(rootDir, excludeTests = true) {
    const urlMap = new Map();

    for (const dir of DIRECTORIES_TO_SCAN) {
        const fullDir = path.join(rootDir, dir);
        const files = getAllSourceFiles(fullDir, excludeTests);

        for (const file of files) {
            const urls = extractUrls(file);
            for (const url of urls) {
                if (!urlMap.has(url)) {
                    urlMap.set(url, []);
                }
                urlMap.get(url).push(path.relative(rootDir, file));
            }
        }
    }

    return urlMap;
}

function isValidPermalink(url) {
    return PERMALINK_PATTERN.test(url) ||
        ROOT_DOMAIN_PATTERN.test(url) ||
        PUSH_SERVER_PATTERN.test(url);
}

function findNonPermalinkUrls(urlMap) {
    const invalid = [];
    for (const [url, files] of urlMap) {
        if (!isValidPermalink(url)) {
            invalid.push({url, files});
        }
    }
    return invalid;
}

const FETCH_HEADERS = {
    'User-Agent': 'Mozilla/5.0 (compatible; MattermostLinkChecker/1.0; +https://github.com/mattermost/mattermost)',
    'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
    'Accept-Language': 'en-US,en;q=0.5',
};

const MAX_REDIRECTS = 10;

async function checkUrl(url, retries = 2) {
    for (let attempt = 0; attempt <= retries; attempt++) {
        try {
            return await checkUrlWithRedirects(url);
        } catch (error) {
            if (attempt === retries) {
                return {
                    url,
                    status: 0,
                    ok: false,
                    error: error.message,
                };
            }
            await new Promise((resolve) => setTimeout(resolve, 1000 * (attempt + 1)));
        }
    }
}

async function checkUrlWithRedirects(originalUrl) {
    let currentUrl = originalUrl;

    for (let redirectCount = 0; redirectCount <= MAX_REDIRECTS; redirectCount++) {
        const response = await fetch(currentUrl, {
            method: 'HEAD',
            redirect: 'manual',
            headers: FETCH_HEADERS,
            signal: AbortSignal.timeout(10000),
        });

        if (response.status === 405 || response.status === 403) {
            const getResponse = await fetch(currentUrl, {
                method: 'GET',
                redirect: 'manual',
                headers: FETCH_HEADERS,
                signal: AbortSignal.timeout(10000),
            });
            return processResponse(originalUrl, getResponse);
        }

        const result = processResponse(originalUrl, response);

        if (!result.redirect) {
            return result;
        }

        const location = response.headers.get('location');
        if (!location) {
            return {
                url: originalUrl,
                status: response.status,
                ok: false,
                error: 'Redirect without Location header',
            };
        }

        currentUrl = new URL(location, currentUrl).href;
    }

    return {
        url: originalUrl,
        status: 0,
        ok: false,
        error: 'Too many redirects',
    };
}

function processResponse(originalUrl, response) {
    const {status} = response;
    const cfHeader = response.headers.get('cf-mitigated');
    const isRedirect = status >= 300 && status < 400;

    if (cfHeader && (isRedirect || status === 403 || status === 503)) {
        return {url: originalUrl, status, ok: true};
    }

    if (status === 301) {
        return {url: originalUrl, status, ok: true};
    }

    if (isRedirect) {
        return {url: originalUrl, status, redirect: true};
    }

    if (response.ok) {
        return {url: originalUrl, status, ok: true};
    }

    return {url: originalUrl, status, ok: false};
}

function shouldSkipUrlCheck(url) {
    return PUSH_SERVER_PATTERN.test(url);
}

async function checkUrls(urls, concurrency = 5, silentProgress = false) {
    const results = [];
    const urlList = Array.from(urls.keys()).filter((url) => !shouldSkipUrlCheck(url));

    for (let i = 0; i < urlList.length; i += concurrency) {
        const batch = urlList.slice(i, i + concurrency);
        const batchResults = await Promise.all(batch.map((url) => checkUrl(url)));
        results.push(...batchResults);

        if (!silentProgress) {
            const completed = Math.min(i + concurrency, urlList.length);
            process.stderr.write(`\rChecking URLs: ${completed}/${urlList.length}`);
        }
    }
    if (!silentProgress) {
        process.stderr.write('\n');
    }

    return results;
}

function printResults(results, urlMap, nonPermalinkUrls) {
    const broken = results.filter((r) => !r.ok);
    const working = results.filter((r) => r.ok);

    console.log('\n' + chalk.bold('=== External Link Check Results ===\n'));

    console.log(chalk.green(`✓ ${working.length} URLs are accessible`));
    if (broken.length > 0) {
        console.log(chalk.red(`✗ ${broken.length} URLs are broken`));
    }
    if (nonPermalinkUrls.length > 0) {
        console.log(chalk.yellow(`⚠ ${nonPermalinkUrls.length} URLs are not using permalink format (warning)`));
    }
    console.log();

    if (broken.length > 0) {
        console.log(chalk.red.bold('Broken URLs:\n'));
        for (const result of broken) {
            const statusText = result.error ? `Error: ${result.error}` : `HTTP ${result.status}`;
            console.log(chalk.red(`  ${result.url}`));
            console.log(chalk.gray(`    Status: ${statusText}`));
            console.log(chalk.gray(`    Found in:`));
            for (const file of urlMap.get(result.url)) {
                console.log(chalk.gray(`      - ${file}`));
            }
            console.log();
        }
    }

    if (nonPermalinkUrls.length > 0) {
        console.log(chalk.yellow.bold('URLs not using permalink format (warning):\n'));
        console.log(chalk.gray('  All mattermost.com links should route via https://mattermost.com/pl/\n'));
        for (const item of nonPermalinkUrls) {
            console.log(chalk.yellow(`  ${item.url}`));
            console.log(chalk.gray(`    Found in:`));
            for (const file of item.files) {
                console.log(chalk.gray(`      - ${file}`));
            }
            console.log();
        }
    }

    if (broken.length === 0 && nonPermalinkUrls.length === 0) {
        console.log(chalk.green.bold(`✓ All URLs are valid and accessible\n`));
    }

    return broken.length > 0 ? 1 : 0;
}

function generateMarkdownSummary(results, urlMap, nonPermalinkUrls) {
    const broken = results.filter((r) => !r.ok);
    const working = results.filter((r) => r.ok);

    const lines = [];

    lines.push('## External Link Check Results\n');

    if (broken.length === 0 && nonPermalinkUrls.length === 0) {
        lines.push(`✅ **All ${working.length} mattermost.com URLs are valid and accessible**\n`);
        return lines.join('\n');
    }

    lines.push(`| Status | Count |`);
    lines.push(`|--------|-------|`);
    lines.push(`| ✅ Working | ${working.length} |`);
    if (broken.length > 0) {
        lines.push(`| ❌ Broken | ${broken.length} |`);
    }
    if (nonPermalinkUrls.length > 0) {
        lines.push(`| ⚠️ Missing /pl/ prefix (warning) | ${nonPermalinkUrls.length} |`);
    }
    lines.push('');

    if (broken.length > 0) {
        lines.push('### Broken URLs\n');
        lines.push('| URL | Status | Files |');
        lines.push('|-----|--------|-------|');

        for (const result of broken) {
            const statusText = result.error ? `Error: ${result.error}` : `HTTP ${result.status}`;
            const files = urlMap.get(result.url).map((f) => `\`${f}\``).join(', ');
            lines.push(`| ${result.url} | ${statusText} | ${files} |`);
        }
        lines.push('');
    }

    if (nonPermalinkUrls.length > 0) {
        lines.push('### ⚠️ URLs Missing Permalink Format (warning)\n');
        lines.push('> All mattermost.com links should route via `https://mattermost.com/pl/`\n');
        lines.push('<details>\n<summary>Show URLs</summary>\n');
        lines.push('| URL | Files |');
        lines.push('|-----|-------|');

        for (const item of nonPermalinkUrls) {
            const files = item.files.map((f) => `\`${f}\``).join(', ');
            lines.push(`| ${item.url} | ${files} |`);
        }
        lines.push('\n</details>');
        lines.push('');
    }

    return lines.join('\n');
}

async function main() {
    const args = process.argv.slice(2);
    const includeTests = args.includes('--include-tests');
    const jsonOutput = args.includes('--json');
    const markdownOutput = args.includes('--markdown');

    const rootDir = process.cwd();

    if (!markdownOutput) {
        console.log(chalk.inverse.bold(' Checking mattermost.com links in webapp... ') + '\n');

        if (includeTests) {
            console.log(chalk.yellow('Including test files in scan\n'));
        }
    }

    const urlMap = findAllMattermostUrls(rootDir, !includeTests);

    if (!markdownOutput) {
        console.log(`Found ${chalk.bold(urlMap.size)} unique mattermost.com URLs\n`);
    }

    if (urlMap.size === 0) {
        if (markdownOutput) {
            console.log('## External Link Check Results\n\n⚠️ No URLs found to check');
        } else {
            console.log(chalk.yellow('No URLs found to check'));
        }
        return 0;
    }

    const nonPermalinkUrls = findNonPermalinkUrls(urlMap);
    const results = await checkUrls(urlMap, 5, markdownOutput);
    const brokenCount = results.filter((r) => !r.ok).length;

    if (markdownOutput) {
        console.log(generateMarkdownSummary(results, urlMap, nonPermalinkUrls));
        return brokenCount > 0 ? 1 : 0;
    }

    if (jsonOutput) {
        const output = {
            total: results.length,
            working: results.filter((r) => r.ok).length,
            broken: results.filter((r) => !r.ok).map((r) => ({
                url: r.url,
                status: r.status,
                error: r.error,
                files: urlMap.get(r.url),
            })),
            nonPermalink: nonPermalinkUrls,
        };
        console.log(JSON.stringify(output, null, 2));
        return brokenCount > 0 ? 1 : 0;
    }

    return printResults(results, urlMap, nonPermalinkUrls);
}

main().then((exitCode) => {
    process.exitCode = exitCode;
}).catch((error) => {
    console.error(chalk.red('Error:'), error);
    process.exitCode = 1;
});