/**
 * Git Clone Utility
 *
 * Shallow-clones repositories into ~/.gitnexus/repos/{name}/.
 * If already cloned, does git pull instead.
 */

import { spawn } from 'child_process';
import path from 'path';
import os from 'os';
import fs from 'fs/promises';
import { isIP } from 'net';

/** Extract the repository name from a git URL (HTTPS or SSH). */
export function extractRepoName(url: string): string {
  const cleaned = url.replace(/\/+$/, '');
  const lastSegment = cleaned.split(/[/:]/).pop() || 'unknown';
  return lastSegment.replace(/\.git$/, '');
}

/** Get the clone target directory for a repo name. */
export function getCloneDir(repoName: string): string {
  return path.join(os.homedir(), '.gitnexus', 'repos', repoName);
}

// Cloud metadata hostnames that must never be reachable via user-supplied URLs
const BLOCKED_HOSTNAMES = new Set([
  'localhost',
  'metadata.google.internal',
  'metadata.azure.com',
  'metadata.internal',
]);

/**
 * Validate a git URL to prevent SSRF attacks.
 * Only allows https:// and http:// schemes. Blocks private/internal addresses,
 * IPv6 private ranges, cloud metadata hostnames, and numeric IP encodings.
 */
export function validateGitUrl(url: string): void {
  let parsed: URL;
  try {
    parsed = new URL(url);
  } catch {
    throw new Error('Invalid URL');
  }

  if (!['https:', 'http:'].includes(parsed.protocol)) {
    throw new Error('Only https:// and http:// git URLs are allowed');
  }

  const host = parsed.hostname.toLowerCase();

  // Block known dangerous hostnames (cloud metadata services)
  if (BLOCKED_HOSTNAMES.has(host)) {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }

  // Strip IPv6 brackets if present (URL parser behavior varies across Node versions)
  let normalizedHost = host;
  if (host.startsWith('[') && host.endsWith(']')) {
    normalizedHost = host.slice(1, -1);
  }

  // Check if this is an IPv6 address
  // Use manual colon detection as fallback since isIP may return 0 for some
  // normalized IPv6 forms (e.g. ::ffff:7f00:1)
  const isIPv6 = isIP(normalizedHost) === 6 || normalizedHost.includes(':');
  if (isIPv6) {
    assertNotPrivateIPv6(normalizedHost);
    return;
  }

  // Check if this is an IPv4 address (including numeric encodings)
  if (isIP(normalizedHost) === 4) {
    assertNotPrivateIPv4(normalizedHost);
    return;
  }

  // For non-IP hostnames, check for numeric IP tricks
  // Decimal encoding: 2130706433 = 127.0.0.1
  // Hex encoding: 0x7f000001 = 127.0.0.1
  if (/^\d+$/.test(host) || /^0x[0-9a-f]+$/i.test(host)) {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }

  // Standard IPv4 regex checks for dotted notation
  if (
    /^127\./.test(host) ||
    /^10\./.test(host) ||
    /^172\.(1[6-9]|2\d|3[01])\./.test(host) ||
    /^192\.168\./.test(host) ||
    /^169\.254\./.test(host) ||
    /^0\./.test(host) ||
    host === '0.0.0.0' ||
    /^100\.(6[4-9]|[7-9]\d|1[01]\d|12[0-7])\./.test(host) ||
    /^198\.1[89]\./.test(host)
  ) {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }
}

function assertNotPrivateIPv6(ip: string): void {
  // Expand common compressed forms for comparison
  const lower = ip.toLowerCase();

  // IPv6 loopback
  if (lower === '::1' || lower === '0:0:0:0:0:0:0:1') {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }

  // Unspecified address
  if (lower === '::' || lower === '0:0:0:0:0:0:0:0') {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }

  // IPv6 Unique Local Address (fc00::/7 = fc and fd prefixes)
  if (lower.startsWith('fc') || lower.startsWith('fd')) {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }

  // IPv6 link-local (fe80::/10)
  if (
    lower.startsWith('fe80') ||
    lower.startsWith('fe8') ||
    lower.startsWith('fe9') ||
    lower.startsWith('fea') ||
    lower.startsWith('feb')
  ) {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }

  // IPv4-mapped IPv6 (::ffff:x.x.x.x or ::ffff:hex:hex)
  // Node may normalize ::ffff:127.0.0.1 to ::ffff:7f00:1
  if (lower.startsWith('::ffff:')) {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }

  // Also catch the expanded form: 0:0:0:0:0:ffff:
  if (lower.includes(':ffff:')) {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }
}

function assertNotPrivateIPv4(ip: string): void {
  const parts = ip.split('.').map(Number);
  const [a, b] = parts;
  if (
    a === 127 ||
    a === 10 ||
    (a === 172 && b >= 16 && b <= 31) ||
    (a === 192 && b === 168) ||
    (a === 169 && b === 254) ||
    a === 0 ||
    (a === 100 && b >= 64 && b <= 127) ||
    (a === 198 && (b === 18 || b === 19))
  ) {
    throw new Error('Cloning from private/internal addresses is not allowed');
  }
}

export interface CloneProgress {
  phase: 'cloning' | 'pulling';
  message: string;
}

/**
 * Clone or pull a git repository.
 * If targetDir doesn't exist: git clone --depth 1
 * If targetDir exists with .git: git pull --ff-only
 */
export async function cloneOrPull(
  url: string,
  targetDir: string,
  onProgress?: (progress: CloneProgress) => void,
): Promise<string> {
  const exists = await fs.access(path.join(targetDir, '.git')).then(
    () => true,
    () => false,
  );

  if (exists) {
    onProgress?.({ phase: 'pulling', message: 'Pulling latest changes...' });
    await runGit(['pull', '--ff-only'], targetDir);
  } else {
    validateGitUrl(url);
    await fs.mkdir(path.dirname(targetDir), { recursive: true });
    onProgress?.({ phase: 'cloning', message: `Cloning ${url}...` });
    await runGit(['clone', '--depth', '1', url, targetDir]);
  }

  return targetDir;
}

function runGit(args: string[], cwd?: string): Promise<void> {
  return new Promise((resolve, reject) => {
    const proc = spawn('git', args, {
      cwd,
      stdio: ['ignore', 'pipe', 'pipe'],
      env: {
        ...process.env,
        // Prevent git from prompting for credentials (hangs the process)
        GIT_TERMINAL_PROMPT: '0',
        // Ensure no credential helper tries to open a GUI prompt
        GIT_ASKPASS: process.platform === 'win32' ? 'echo' : '/bin/true',
      },
    });

    let stderr = '';
    proc.stderr.on('data', (chunk: Buffer) => {
      stderr += chunk;
    });

    proc.on('close', (code) => {
      if (code === 0) resolve();
      else {
        // Log full stderr internally but don't expose it to API callers (SSRF mitigation)
        if (stderr.trim()) console.error(`git ${args[0]} stderr: ${stderr.trim()}`);
        reject(new Error(`git ${args[0]} failed (exit code ${code})`));
      }
    });

    proc.on('error', (err) => {
      reject(new Error(`Failed to spawn git: ${err.message}`));
    });
  });
}