#!/usr/bin/env node

import { execSync, spawnSync } from 'node:child_process'
import fs from 'node:fs'
import https from 'node:https'
import os from 'node:os'
import path from 'node:path'
import process from 'node:process'
import readline from 'node:readline'
import { fileURLToPath } from 'node:url'

const __filename = fileURLToPath(import.meta.url)
const __dirname = path.dirname(__filename)

// Ensure we are working in the script's directory
process.chdir(__dirname)

const CLI_VERSION = '1.2.0'
const REPO_OWNER = 'toddeTV'
const REPO_NAME = 'quick-conf'
const GITHUB_API_BASE = 'https://api.github.com'

let PACKAGE_MANAGER = 'pnpm'

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
})

// --- Helpers ---

function safeUnlink(filePath) {
  try {
    if (fs.existsSync(filePath)) {
      fs.unlinkSync(filePath)
    }
  }
  catch {
    // ignore errors (e.g. file locked)
  }
}

/**
 * Checks if the current directory is empty (ignoring .git and the script itself).
 * @returns {boolean} True if empty, false otherwise.
 */
function checkDirectoryEmpty() {
  const files = fs.readdirSync(process.cwd())
  const allowed = ['.git', path.basename(__filename)]
  const others = files.filter(f => !allowed.includes(f))
  return others.length === 0
}

/**
 * Checks if the current directory is a clone of the template.
 * @returns {boolean} True if it is a template clone, false otherwise.
 */
function checkIsTemplateClone() {
  const pkgPath = path.join(process.cwd(), 'package.json')
  if (!fs.existsSync(pkgPath))
    return false
  try {
    const pkg = JSON.parse(fs.readFileSync(pkgPath, 'utf-8'))
    return pkg.isQuickConfTemplate === true
  }
  catch {
    return false
  }
}

/**
 * Deletes all files in the current directory except .git and the script itself.
 * @param {string[]} additionalAllowed - Additional files/folders to preserve.
 */
function clearDirectory(additionalAllowed = []) {
  // Safety check: ensure we're not in a dangerous location
  const cwd = path.resolve(process.cwd())
  const home = path.resolve(os.homedir())
  const { root } = path.parse(cwd)
  if (cwd === home || cwd === root) {
    log('Error: Cannot clear directory in home or root directory', 'error')
    process.exit(1)
  }

  // Read and delete files and folders
  const files = fs.readdirSync(process.cwd())
  const allowed = ['.git', path.basename(__filename), ...additionalAllowed]
  for (const file of files) {
    if (allowed.includes(file))
      continue
    fs.rmSync(path.join(process.cwd(), file), { recursive: true, force: true })
  }
}

/**
 * Recursively replaces a string in all files within a directory.
 * @param {string} dir - The directory to search in.
 * @param {string} search - The string to search for.
 * @param {string | ((filePath: string) => string)} replacement - The string to replace with
 *   or a file-aware replacement factory.
 */
function replaceStringInDirectory(dir, search, replacement) {
  if (!fs.existsSync(dir))
    return
  const files = fs.readdirSync(dir)
  for (const file of files) {
    const filePath = path.join(dir, file)
    const stat = fs.lstatSync(filePath)
    if (stat.isSymbolicLink()) {
      continue
    }
    if (stat.isDirectory()) {
      replaceStringInDirectory(filePath, search, replacement)
    }
    else {
      try {
        let content = fs.readFileSync(filePath, 'utf-8')
        if (content.includes(search)) {
          const replacementValue = typeof replacement === 'function' ? replacement(filePath) : replacement
          content = content.replaceAll(search, replacementValue)
          fs.writeFileSync(filePath, content, 'utf-8')
        }
      }
      catch {
        // ignore binary files or errors
      }
    }
  }
}

/**
 * Creates a format-safe replacement string for each target file type.
 * @param {string} filePath - The file currently being processed.
 * @param {string} projectName - The user-defined project name.
 * @returns {string} A replacement value safe for the file format.
 */
function getSafeProjectNameReplacement(filePath, projectName) {
  const ext = path.extname(filePath).toLowerCase()

  if (ext === '.json') {
    return JSON.stringify(projectName).slice(1, -1)
  }

  if (ext === '.yml' || ext === '.yaml') {
    return `'${projectName.replaceAll('\'', '\'\'')}'`
  }

  return projectName
}

/**
 * Removes repository metadata files and folders that should not be in the final project.
 * These files are useful for maintaining the template repository, not for end-user projects.
 */
function removeRepoFiles() {
  log('Removing repository-only files...', 'info')
  const folders = [
    '.github',
    'docs',
  ]
  const files = [
    '.coderabbit.yml',
    '.release-please-manifest.json',
    'CHANGELOG.md',
    'CONTRIBUTING.md',
    'LICENSE.md',
    'README.md',
    'release-please-config.json',
    'renovate.json',
  ]

  for (const folder of folders) {
    const itemPath = path.join(process.cwd(), folder)
    if (fs.existsSync(itemPath)) {
      fs.rmSync(itemPath, { recursive: true, force: true })
    }
  }
  for (const file of files) {
    const itemPath = path.join(process.cwd(), file)
    if (fs.existsSync(itemPath)) {
      try {
        fs.unlinkSync(itemPath)
      }
      catch (e) {
        log(`Failed to delete ${file}: ${e.message}`, 'warn')
      }
    }
  }
}

/**
 * Replaces starter placeholders in project files.
 * @param {string} projectName - The project name used for placeholder replacement.
 */
function applyProjectNamePlaceholders(projectName) {
  const placeholderTargets = [
    'content',
    'public',
    'template-starter',
  ]
  for (const target of placeholderTargets) {
    const targetPath = path.join(process.cwd(), target)
    replaceStringInDirectory(
      targetPath,
      'ConferenceNamePlaceholder',
      filePath => getSafeProjectNameReplacement(filePath, projectName),
    )
  }
}

/**
 * Applies template-starter override files by moving them to the root.
 */
function applyTemplateStarter() {
  const starterPath = path.join(process.cwd(), 'template-starter')
  if (!fs.existsSync(starterPath)) {
    log('No template-starter found; skipping starter setup', 'info')
    return
  }

  log('Applying template-starter overrides...', 'info')

  // Step 5: Check collisions and delete in root
  const items = fs.readdirSync(starterPath)
  for (const item of items) {
    const rootPath = path.join(process.cwd(), item)
    if (fs.existsSync(rootPath)) {
      fs.rmSync(rootPath, { recursive: true, force: true })
    }
  }

  // Step 6: Move files
  for (const item of items) {
    const src = path.join(starterPath, item)
    const dest = path.join(process.cwd(), item)
    fs.renameSync(src, dest)
  }

  // Step 7: Delete folder
  fs.rmSync(starterPath, { recursive: true, force: true })
  log('Template-starter overrides applied.', 'info')
}

/**
 * Deletes package manager lock files to ensure a fresh dependency resolution.
 */
function deleteLockFiles() {
  const lockFiles = ['package-lock.json', 'yarn.lock', 'pnpm-lock.yaml', 'bun.lockb']
  for (const file of lockFiles) {
    const filePath = path.join(process.cwd(), file)
    if (fs.existsSync(filePath)) {
      try {
        fs.unlinkSync(filePath)
      }
      catch {
        // ignore
      }
    }
  }
  log('Deleted existing lock files to ensure fresh installation.', 'info')
}

/**
 * Prompts the user to install dependencies.
 * @returns {Promise<void>}
 */
async function promptInstallDependencies() {
  const installDeps = await askQuestion(`Do you want to run "${PACKAGE_MANAGER} install"? (y/N): `)
  if (installDeps.toLowerCase() === 'y') {
    const cmd = `${PACKAGE_MANAGER} install`
    log(`Running ${cmd} ...`)
    try {
      execSync(cmd, { stdio: 'inherit' })
    }
    catch (e) {
      log(`Failed to run install: ${e.message}`, 'error')
    }
  }
  else {
    log('Warning: Dependencies not installed.', 'warn')
    log('A lock file is required for stable builds and dependencies are needed to run the app.', 'warn')
    log(`Please run "${PACKAGE_MANAGER} install" manually to generate a lock file.`, 'warn')
  }
}

/**
 * Configures the project by asking for the name and clearing metadata.
 * @returns {Promise<string|null>} The user entered project name.
 */
async function configureProject() {
  log('Configuring project...', 'info')
  const pkgPath = path.join(process.cwd(), 'package.json')
  if (!fs.existsSync(pkgPath)) {
    log('package.json not found, skipping configuration.', 'warn')
    return null
  }

  let pkg
  try {
    pkg = JSON.parse(fs.readFileSync(pkgPath, 'utf-8'))
  }
  catch (e) {
    log(`Failed to parse package.json: ${e.message}`, 'error')
    return null
  }

  const rawInput = await askQuestion('Enter the name of your project: ')
  const cleanedProjectName = rawInput.trim().replace(/\s+/g, ' ')

  if (!cleanedProjectName) {
    log('Project name cannot be empty.', 'error')
    return null
  }

  const pkgName = cleanedProjectName
    .toLowerCase()
    .replace(/[^a-z0-9-]+/g, '-')
    .replace(/-+/g, '-')
    .replace(/^-+|-+$/g, '')

  if (!pkgName) {
    log('Project name yields an invalid package.json name.', 'error')
    return null
  }

  // Update package.json fields
  pkg.name = pkgName
  pkg.author = ''
  pkg.contributors = []
  pkg.description = ''
  pkg.repository = {}
  pkg.bugs = {}
  pkg.keywords = []
  delete pkg.isQuickConfTemplate

  fs.writeFileSync(pkgPath, JSON.stringify(pkg, null, 2))
  log(`Updated package.json with name "${pkgName}" and cleared metadata.`, 'success')

  return cleanedProjectName
}

/**
 * Displays the license compliance warning.
 */
async function showLicenseWarning() {
  console.log(`\n${'='.repeat(50)}`)
  log('LICENSE COMPLIANCE WARNING', 'warn')
  console.log('='.repeat(50))
  console.log('This template repository uses a dual-license model.')
  console.log('A small set of repository-only files is listed as "Restricted Repository Files (All Rights Reserved)".')
  console.log('\nThe installer removes these restricted repository files from your end-user project.')
  console.log('For the full list and legal terms, read LICENSE.md in the template repository:')
  console.log('https://github.com/toddeTV/quick-conf/blob/main/LICENSE.md')
  console.log('\nNote: The file \'public/custom-styles.css\' must exist.')
  console.log(`${'='.repeat(50)}\n`)

  await askQuestion('Press Enter to confirm you have read and understood this warning...')
}

/**
 * Prompts the user with a question and returns the answer.
 * @param {string} query - The question to ask.
 * @returns {Promise<string>} The user's input.
 */
function askQuestion(query) {
  return new Promise(resolve => rl.question(query, resolve))
}

/**
 * Logs a message to the console with color coding based on type.
 * @param {string} msg - The message to log.
 * @param {'info'|'success'|'warn'|'error'} type - The type of log message.
 */
function log(msg, type = 'info') {
  const colors = {
    info: '\x1B[36m%s\x1B[0m', // Cyan
    success: '\x1B[32m%s\x1B[0m', // Green
    warn: '\x1B[33m%s\x1B[0m', // Yellow
    error: '\x1B[31m%s\x1B[0m', // Red
  }
  console.log(colors[type] || colors.info, `[Quick Conf] ${msg}`)
}

/**
 * Fetches and parses JSON content from a URL.
 * @param {string} url - The URL to fetch.
 * @returns {Promise<any>} The parsed JSON data.
 */
async function fetchJson(url) {
  return new Promise((resolve, reject) => {
    const options = {
      headers: {
        'User-Agent': 'Quick-Conf-CLI',
        'Accept': 'application/vnd.github.v3+json',
      },
    }
    https.get(url, options, (res) => {
      let data = ''
      if (res.statusCode >= 400) {
        // Consume response data to free up memory
        res.resume()
        return reject(new Error(`Request Failed. Status Code: ${res.statusCode}`))
      }
      res.on('data', (chunk) => {
        data += chunk
      })
      res.on('end', () => {
        try {
          resolve(JSON.parse(data))
        }
        catch (e) {
          reject(e)
        }
      })
    }).on('error', reject)
  })
}

/**
 * Downloads a file from a URL to a local destination.
 * Handles redirects (301/302).
 * @param {string} url - The URL to download from.
 * @param {string} dest - The local file path destination.
 * @returns {Promise<string>} The destination path upon success.
 */
async function downloadFile(url, dest) {
  return new Promise((resolve, reject) => {
    const file = fs.createWriteStream(dest)
    https.get(url, { headers: { 'User-Agent': 'Quick-Conf-CLI' } }, (response) => {
      if (response.statusCode === 302 || response.statusCode === 301) {
        file.close()
        fs.unlinkSync(dest) // Delete partial file
        return downloadFile(response.headers.location, dest).then(resolve).catch(reject)
      }
      if (response.statusCode !== 200) {
        file.close()
        fs.unlinkSync(dest)
        return reject(new Error(`Failed to download. Status Code: ${response.statusCode}`))
      }
      response.pipe(file)
      file.on('finish', () => {
        file.close(() => resolve(dest))
      })
    }).on('error', (err) => {
      fs.unlink(dest, () => {})
      reject(err)
    })
  })
}

/**
 * Extracts a tarball to a destination directory using the system `tar` command.
 * @param {string} tarPath - The path to the tarball file.
 * @param {string} destDir - The directory where files should be extracted.
 * @throws {Error} If extraction fails.
 */
function extractTarball(tarPath, destDir) {
  // Ensure destDir exists
  if (!fs.existsSync(destDir)) {
    fs.mkdirSync(destDir, { recursive: true })
  }
  try {
    // Use spawnSync to avoid shell injection risks
    const result = spawnSync('tar', ['-xf', tarPath, '-C', destDir, '--strip-components=1'], { stdio: 'inherit' })

    if (result.error)
      throw result.error
    if (result.status !== 0)
      throw new Error(`tar exited with code ${result.status}`)
  }
  catch (error) {
    throw new Error(`Failed to extract tarball: ${error.message}`)
  }
}

/**
 * Fetches the content of a remote file as a string.
 * @param {string} url - The URL of the file to fetch.
 * @returns {Promise<string>} The file content.
 */
async function getRemoteFileContent(url) {
  return new Promise((resolve, reject) => {
    https.get(url, (res) => {
      let data = ''
      res.on('data', chunk => data += chunk)
      res.on('end', () => resolve(data))
    }).on('error', reject)
  })
}

/**
 * Retrieves the version of the CLI tool from the remote repository.
 * @returns {Promise<string>} The remote version string, or 'Unknown' if fetch fails.
 */
async function getRemoteCliVersion() {
  try {
    const url = `https://raw.githubusercontent.com/${REPO_OWNER}/${REPO_NAME}/main/quick-conf-cli.mjs`
    const content = await getRemoteFileContent(url)
    const match = content.match(/const CLI_VERSION = '([\d.]+)'/)
    return match ? match[1] : 'Unknown'
  }
  catch {
    return 'Unknown'
  }
}

/**
 * Retrieves the version of the local project from package.json.
 * @returns {string} The local project version, or '-' if not found.
 */
function getLocalProjectVersion() {
  try {
    const pkgPath = path.join(process.cwd(), 'package.json')
    if (fs.existsSync(pkgPath)) {
      const pkg = JSON.parse(fs.readFileSync(pkgPath, 'utf-8'))
      return pkg.version || '-'
    }
  }
  catch {}
  return '-'
}

/**
 * Prompts the user to select a package manager and updates the global configuration.
 * Defaults to 'pnpm'.
 * @returns {Promise<void>}
 */
async function selectPackageManager() {
  console.log('\nSelect Package Manager:')
  console.log('1. pnpm (Recommended because of existing `pnpm-lock.yaml`)')
  console.log('2. npm')
  console.log('3. yarn')
  console.log('4. bun')

  const choice = await askQuestion('Enter choice (1-4) [1]: ')
  switch (choice.trim()) {
    case '2':
      PACKAGE_MANAGER = 'npm'
      break
    case '3':
      PACKAGE_MANAGER = 'yarn'
      break
    case '4':
      PACKAGE_MANAGER = 'bun'
      break
    default:
      PACKAGE_MANAGER = 'pnpm'
      break
  }
  log(`Selected package manager: ${PACKAGE_MANAGER}`, 'info')
}

// --- Features ---

/**
 * Checks if a newer version of the CLI is available and prompts for update.
 * @param {string} remoteCliVer - The version string of the remote CLI.
 * @returns {Promise<void>}
 */
async function checkSelfUpdate(remoteCliVer) {
  log('Checking for updates...')
  try {
    const latestVersion = remoteCliVer

    if (latestVersion !== 'Unknown' && compareVersions(latestVersion, CLI_VERSION) > 0) {
      log(`New version available: ${latestVersion} (Current: ${CLI_VERSION})`, 'warn')
      const answer = await askQuestion('Do you want to update the CLI tool? (y/N): ')
      if (answer.toLowerCase() === 'y') {
        // Find asset
        const latestRelease = await fetchJson(`${GITHUB_API_BASE}/repos/${REPO_OWNER}/${REPO_NAME}/releases/latest`)
        const asset = latestRelease.assets.find(a => a.name === 'quick-conf-cli.mjs')
        let downloadUrl
        if (asset) {
          downloadUrl = asset.browser_download_url
        }
        else {
          // Fallback to raw file from tag if asset not found (assuming standard repo structure)
          downloadUrl = `https://raw.githubusercontent.com/${REPO_OWNER}/${REPO_NAME}/${latestRelease.tag_name}`
            + '/quick-conf-cli.mjs'
          log('CLI asset not found in release, trying to fetch from source...', 'warn')
        }

        log(`Downloading update from ${downloadUrl}...`)
        const newFile = `${__filename}.new`
        const oldFile = `${__filename}.old`

        await downloadFile(downloadUrl, newFile)

        // Rename current to .old
        try {
          if (fs.existsSync(oldFile))
            safeUnlink(oldFile)
          fs.renameSync(__filename, oldFile)
        }
        catch (e) {
          log(`Failed to rename current script: ${e.message}`, 'error')
          log(`Update downloaded to: ${newFile}`, 'info')
          log('Please manually rename it to quick-conf-cli.mjs', 'info')
          process.exit(1)
        }

        // Rename .new to current
        try {
          fs.renameSync(newFile, __filename)
          log('Update complete. Please restart the tool.', 'success')
          process.exit(0)
        }
        catch (e) {
          log(`Failed to install new script: ${e.message}`, 'error')
          // Try to restore
          try {
            fs.renameSync(oldFile, __filename)
            log('Restored original script.', 'info')
          }
          catch {
            log('Failed to restore original script. You may need to reinstall.', 'error')
          }
          process.exit(1)
        }
      }
    }
    else {
      log('CLI is up to date.')
    }
  }
  catch (error) {
    log(`Failed to check for updates: ${error.message}`, 'error')
    // Continue execution even if update check fails
  }
}

/**
 * Compares two semantic version strings.
 * @param {string} v1 - The first version string.
 * @param {string} v2 - The second version string.
 * @returns {number} 1 if v1 > v2, -1 if v1 < v2, 0 if equal.
 */
function compareVersions(v1, v2) {
  const s1 = parseSemver(v1)
  const s2 = parseSemver(v2)

  if (!s1 || !s2) {
    const n1 = normalizeSemver(v1) || String(v1 || '')
    const n2 = normalizeSemver(v2) || String(v2 || '')
    if (n1 === n2)
      return 0
    return n1 > n2 ? 1 : -1
  }

  if (s1.major !== s2.major)
    return s1.major > s2.major ? 1 : -1

  if (s1.minor !== s2.minor)
    return s1.minor > s2.minor ? 1 : -1

  if (s1.patch !== s2.patch)
    return s1.patch > s2.patch ? 1 : -1

  const p1 = s1.prerelease
  const p2 = s2.prerelease

  if (!p1.length && !p2.length)
    return 0

  // Stable releases sort after prereleases with identical major.minor.patch.
  if (!p1.length)
    return 1
  if (!p2.length)
    return -1

  for (let i = 0; i < Math.max(p1.length, p2.length); i++) {
    const id1 = p1[i]
    const id2 = p2[i]
    if (id1 === undefined)
      return -1
    if (id2 === undefined)
      return 1

    const numeric1 = /^\d+$/.test(id1)
    const numeric2 = /^\d+$/.test(id2)
    if (numeric1 && numeric2) {
      const n1 = Number(id1)
      const n2 = Number(id2)
      if (n1 !== n2)
        return n1 > n2 ? 1 : -1
      continue
    }

    if (numeric1 && !numeric2)
      return -1
    if (!numeric1 && numeric2)
      return 1

    if (id1 !== id2)
      return id1 > id2 ? 1 : -1
  }

  return 0
}

/**
 * Parses a semantic version into numeric parts and prerelease identifiers.
 * @param {string} version - Version string to parse.
 * @returns {{ major: number, minor: number, patch: number, prerelease: string[] } | null}
 *   Parsed semantic version object or null.
 */
function parseSemver(version) {
  const normalized = normalizeSemver(version)
  if (!normalized)
    return null

  const match = normalized.match(/^(\d+)\.(\d+)\.(\d+)(?:-([0-9a-z.-]+))?$/i)
  if (!match)
    return null

  return {
    major: Number(match[1]),
    minor: Number(match[2]),
    patch: Number(match[3]),
    prerelease: match[4] ? match[4].split('.') : [],
  }
}

/**
 * Normalizes a version string to x.y.z and removes a leading `v`.
 * Returns null when no semantic version pattern is found.
 * @param {string} version - Version string to normalize.
 * @returns {string|null} Normalized semantic version or null.
 */
function normalizeSemver(version) {
  if (!version)
    return null

  const clean = String(version).trim().replace(/^v/, '')
  const match = clean.match(/^(\d+)\.(\d+)\.(\d+)(?:-([0-9a-z.-]+))?/i)
  if (!match)
    return null

  const prerelease = match[4] ? `-${match[4]}` : ''
  return `${Number(match[1])}.${Number(match[2])}.${Number(match[3])}${prerelease}`
}

/**
 * Parses YAML-like frontmatter key-value pairs from markdown.
 * Supports simple scalar values used in migration guides.
 * @param {string} markdown - Markdown file contents.
 * @returns {Record<string, string>} Parsed frontmatter key-value map.
 */
function parseFrontmatter(markdown) {
  const match = markdown.match(/^---\n([\s\S]*?)\n---/)
  if (!match)
    return {}

  const values = {}
  for (const line of match[1].split('\n')) {
    const idx = line.indexOf(':')
    if (idx <= 0)
      continue

    const key = line.slice(0, idx).trim()
    let value = line.slice(idx + 1).trim()
    value = value.replace(/^['"]|['"]$/g, '')
    values[key] = value
  }

  return values
}

/**
 * Extracts migration versions from file name format vX.Y.Z-to-vA.B.C.md
 * @param {string} fileName - Migration guide file name.
 * @returns {{ fromVersion: string, toVersion: string } | null} Parsed versions or null.
 */
function parseMigrationGuideFileName(fileName) {
  const match = fileName.match(/^v(\d+\.\d+\.\d+)-to-v(\d+\.\d+\.\d+)\.md$/)
  if (!match)
    return null

  return {
    fromVersion: match[1],
    toVersion: match[2],
  }
}

/**
 * Builds migration path from current version to target version using available guides.
 * @param {Array<{name: string, fromVersion: string, toVersion: string, manualSteps: boolean}>} guides
 * @param {string} fromVersion
 * @param {string} toVersion
 */
function buildMigrationPath(guides, fromVersion, toVersion) {
  const start = normalizeSemver(fromVersion)
  const target = normalizeSemver(toVersion)
  if (!start || !target)
    return { complete: false, pathLabel: '', steps: [], actionableSteps: [] }

  if (compareVersions(start, target) >= 0)
    return { complete: true, pathLabel: `v${start}`, steps: [], actionableSteps: [] }

  const normalizedGuides = guides
    .map((guide) => {
      const from = normalizeSemver(guide.fromVersion)
      const to = normalizeSemver(guide.toVersion)
      if (!from || !to)
        return null

      return {
        ...guide,
        normalizedFrom: from,
        normalizedTo: to,
      }
    })
    .filter(Boolean)

  const guideMap = new Map()
  for (const guide of normalizedGuides) {
    const list = guideMap.get(guide.normalizedFrom) || []
    list.push(guide)
    guideMap.set(guide.normalizedFrom, list)
  }

  for (const [from, list] of guideMap) {
    const ordered = list
      .filter(guide => compareVersions(guide.normalizedTo, from) > 0)
      .filter(guide => compareVersions(guide.normalizedTo, target) <= 0)
      .sort((a, b) => compareVersions(a.normalizedTo, b.normalizedTo))
    guideMap.set(from, ordered)
  }

  const visited = new Set([start])
  const findPath = (currentVersion) => {
    if (currentVersion === target)
      return []

    const candidates = guideMap.get(currentVersion) || []
    for (const candidate of candidates) {
      if (visited.has(candidate.normalizedTo))
        continue

      visited.add(candidate.normalizedTo)
      const rest = findPath(candidate.normalizedTo)
      if (rest)
        return [candidate, ...rest]
      visited.delete(candidate.normalizedTo)
    }

    return null
  }

  const selectedPath = findPath(start) || []
  const versionsInPath = [`v${start}`]
  const steps = []
  let current = start

  for (const candidate of selectedPath) {
    steps.push(candidate)
    versionsInPath.push(`v${candidate.normalizedTo}`)
    current = candidate.normalizedTo
  }

  const complete = compareVersions(current, target) === 0
  const actionableSteps = steps.filter(step => step.manualSteps)

  return {
    complete,
    pathLabel: versionsInPath.join(' -> '),
    steps,
    actionableSteps,
  }
}

/**
 * Performs a fresh installation of the template.
 * Downloads the latest release, extracts it, and optionally installs dependencies.
 * @param {boolean} isTemplateClone - Whether we are installing over a template clone.
 * @returns {Promise<void>}
 */
async function freshInstall(isTemplateClone = false) {
  if (isTemplateClone) {
    log('Detected "Fresh Installation after using the Template on GitHub".', 'info')
    if (!checkIsTemplateClone()) {
      log('Error: Current directory does not appear to be a valid template clone', 'error')
      log('(wrong name or version in package.json).', 'error')
      return
    }
    const answer = await askQuestion(
      'This will DELETE ALL FILES in the current directory (except .git and this script) '
      + 'and install the latest release. Continue? (y/N): ',
    )
    if (answer.toLowerCase() !== 'y')
      return

    log('Clearing directory...', 'warn')
    // Step 1: Clear directory
    clearDirectory()
  }
  else {
    log('Detected "Fresh Installation in an empty folder".', 'info')
    log('Checking if directory is empty...', 'info')
    if (!checkDirectoryEmpty()) {
      log('Error: Directory is not empty. Please run this in an empty folder (except .git and this script).', 'error')
      return
    }
    const answer = await askQuestion(
      'This will download the latest release into the current directory. Continue? (y/N): ',
    )
    if (answer.toLowerCase() !== 'y')
      return
  }

  try {
    // Step 2: Download Everything
    log('Fetching latest release info...')
    const latestRelease = await fetchJson(`${GITHUB_API_BASE}/repos/${REPO_OWNER}/${REPO_NAME}/releases/latest`)
    const tarballUrl = latestRelease.tarball_url

    log(`Downloading release ${latestRelease.tag_name}...`)
    const tempTar = path.join(__dirname, 'temp_install.tar.gz')
    await downloadFile(tarballUrl, tempTar)

    const tempDir = path.join(__dirname, '.install_temp')
    if (fs.existsSync(tempDir))
      fs.rmSync(tempDir, { recursive: true, force: true })
    fs.mkdirSync(tempDir)

    log('Extracting...')
    extractTarball(tempTar, tempDir)
    fs.unlinkSync(tempTar)

    log('Installing files...')
    const extractedFiles = fs.readdirSync(tempDir)
    for (const file of extractedFiles) {
      if (file === 'quick-conf-cli.mjs')
        continue // Skip overwriting the CLI tool

      const src = path.join(tempDir, file)
      const dest = path.join(process.cwd(), file)
      // Move to root
      fs.renameSync(src, dest)
    }

    // Cleanup
    fs.rmSync(tempDir, { recursive: true, force: true })
    log('Installation files downloaded.', 'success')

    const projectName = await configureProject()

    if (!projectName)
      throw new Error('Project configuration failed.')

    log(`Replacing placeholders with "${projectName}"...`, 'info')
    applyProjectNamePlaceholders(projectName)

    // Remove repository-only files
    removeRepoFiles()

    // Apply template starter overrides
    applyTemplateStarter()

    await showLicenseWarning()

    deleteLockFiles()
    await promptInstallDependencies()

    log('Fresh installation complete!', 'success')
  }
  catch (error) {
    log(`Installation failed: ${error.message}`, 'error')
  }
}

/**
 * Updates the template while preserving user content.
 * Backs up specific directories/files, installs the new version, and restores the backup.
 * @returns {Promise<void>}
 */
async function updateTemplate() {
  log('Starting update process...')

  // Step 1: Backup to .update_temp
  const updateTemp = path.join(__dirname, '.update_temp')

  if (fs.existsSync(updateTemp))
    fs.rmSync(updateTemp, { recursive: true, force: true })
  fs.mkdirSync(updateTemp)
  const backupDir = path.join(updateTemp, 'backup')
  fs.mkdirSync(backupDir)

  log('Backing up user files...', 'info')

  const moveIfExists = (srcRel, destRel) => {
    const src = path.join(process.cwd(), srcRel)
    const dest = path.join(backupDir, destRel)
    if (fs.existsSync(src)) {
      const destParent = path.dirname(dest)
      if (!fs.existsSync(destParent))
        fs.mkdirSync(destParent, { recursive: true })
      fs.renameSync(src, dest)
      return true
    }
    return false
  }

  // Preserve user content based on "Preserve Map" strategy
  moveIfExists('.github', '.github')
  moveIfExists('content', 'content')
  moveIfExists('public', 'public')
  moveIfExists('.env', '.env')
  moveIfExists('LICENSE.md', 'LICENSE.md')
  moveIfExists('README.md', 'README.md')

  // Preserve IDE and LLM/AI settings
  moveIfExists('.claude', '.claude')
  moveIfExists('CLAUDE.md', 'CLAUDE.md')
  moveIfExists('.cursor', '.cursor')
  moveIfExists('.vscode', '.vscode')
  moveIfExists('.idea', '.idea')

  // Handle package.json metadata separately later, but we need to read it now
  let oldPkg = null
  const pkgPath = path.join(process.cwd(), 'package.json')
  if (fs.existsSync(pkgPath)) {
    try {
      oldPkg = JSON.parse(fs.readFileSync(pkgPath, 'utf-8'))
    }
    catch (e) {
      log(`Could not read current package.json: ${e.message}`, 'warn')
    }
  }

  // Step 2: Clear root (except cli, .git, .update_temp)
  log('Clearing directory for update...', 'warn')
  clearDirectory(['.update_temp'])

  try {
    // Step 3: Download Everything
    log('Fetching latest release info...')
    const latestRelease = await fetchJson(`${GITHUB_API_BASE}/repos/${REPO_OWNER}/${REPO_NAME}/releases/latest`)
    const tarballUrl = latestRelease.tarball_url

    const tempTar = path.join(updateTemp, 'temp_update.tar.gz')
    log(`Downloading release ${latestRelease.tag_name}...`)
    await downloadFile(tarballUrl, tempTar)

    const extractDir = path.join(updateTemp, 'extracted')
    fs.mkdirSync(extractDir)
    log(`Extracting release ${latestRelease.tag_name}...`)
    extractTarball(tempTar, extractDir)
    fs.unlinkSync(tempTar)

    // Move extracted files to root
    const extractedFiles = fs.readdirSync(extractDir)
    for (const file of extractedFiles) {
      if (file === 'quick-conf-cli.mjs')
        continue

      const src = path.join(extractDir, file)
      const dest = path.join(process.cwd(), file)
      fs.renameSync(src, dest)
    }

    // Step 4: Remove Repo Files AND template-starter
    removeRepoFiles()
    const starterPath = path.join(process.cwd(), 'template-starter')
    if (fs.existsSync(starterPath)) {
      fs.rmSync(starterPath, { recursive: true, force: true })
    }

    // Step 5: Restore package.json metadata
    if (oldPkg) {
      const newPkgPath = path.join(process.cwd(), 'package.json')
      if (fs.existsSync(newPkgPath)) {
        try {
          const newPkg = JSON.parse(fs.readFileSync(newPkgPath, 'utf-8'))
          newPkg.name = oldPkg.name
          newPkg.author = oldPkg.author
          newPkg.contributors = oldPkg.contributors
          newPkg.description = oldPkg.description
          newPkg.keywords = oldPkg.keywords
          newPkg.bugs = oldPkg.bugs
          newPkg.repository = oldPkg.repository
          delete newPkg.isQuickConfTemplate
          fs.writeFileSync(newPkgPath, JSON.stringify(newPkg, null, 2))
          log('Restored project metadata.', 'success')
        }
        catch (e) {
          log(`Failed to restore project metadata: ${e.message}`, 'error')
        }
      }
    }

    // Step 6 & 7: Restore Backup
    log('Restoring user files...')
    const backupItems = fs.readdirSync(backupDir)
    for (const item of backupItems) {
      // Step 6: Delete collisions from root (clean slate matching backup)
      const rootPath = path.join(process.cwd(), item)
      if (fs.existsSync(rootPath)) {
        fs.rmSync(rootPath, { recursive: true, force: true })
      }
    }
    // Step 7: Move backup to root
    for (const item of backupItems) {
      const src = path.join(backupDir, item)
      const dest = path.join(process.cwd(), item)
      fs.renameSync(src, dest)
    }

    // Step 8: Delete .update_temp
    fs.rmSync(updateTemp, { recursive: true, force: true })

    deleteLockFiles()
    await promptInstallDependencies()

    log('Update complete!', 'success')
  }
  catch (error) {
    log(`Update failed: ${error.message}`, 'error')
    log('You may need to manually restore files from .update_temp/backup if it exists.', 'warn')
  }
}

/**
 * Fetches and displays migration notes from the repository.
 * Allows the user to select a specific migration guide to view.
 * @returns {Promise<void>}
 */
async function viewMigrationNotes() {
  log('Fetching migration notes...')
  try {
    // Fetch the guides folder
    const contents = await fetchJson(
      `${GITHUB_API_BASE}/repos/${REPO_OWNER}/${REPO_NAME}/contents/docs/migrations/guides`,
    )
    if (!Array.isArray(contents)) {
      log('No migration notes found or invalid response.', 'warn')
      return
    }

    const files = contents.filter(f => f.type === 'file' && f.name.endsWith('.md'))
    if (files.length === 0) {
      log('No migration documents found.', 'info')
      return
    }

    const guides = []
    for (const file of files) {
      try {
        const markdown = await getRemoteFileContent(file.download_url)
        const frontmatter = parseFrontmatter(markdown)
        const fileMeta = parseMigrationGuideFileName(file.name) || { fromVersion: '', toVersion: '' }
        const manualSteps = frontmatter.manualSteps
          ? frontmatter.manualSteps.toLowerCase() === 'true'
          : true

        guides.push({
          ...file,
          markdown,
          fromVersion: normalizeSemver(frontmatter.fromVersion || fileMeta.fromVersion) || '',
          toVersion: normalizeSemver(frontmatter.toVersion || fileMeta.toVersion) || '',
          manualSteps,
        })
      }
      catch {
        // Skip entries that cannot be parsed.
      }
    }

    if (guides.length === 0) {
      log('No readable migration documents found.', 'warn')
      return
    }

    guides.sort((a, b) => {
      const fromDiff = compareVersions(a.fromVersion || '0.0.0', b.fromVersion || '0.0.0')
      if (fromDiff !== 0)
        return fromDiff
      return compareVersions(a.toVersion || '0.0.0', b.toVersion || '0.0.0')
    })

    let remoteVersion = null
    try {
      const latestRelease = await fetchJson(`${GITHUB_API_BASE}/repos/${REPO_OWNER}/${REPO_NAME}/releases/latest`)
      remoteVersion = normalizeSemver(latestRelease.tag_name)
    }
    catch {
      // Ignore if release metadata cannot be fetched.
    }

    const localVersion = normalizeSemver(getLocalProjectVersion())
    if (localVersion && remoteVersion && compareVersions(localVersion, remoteVersion) < 0) {
      const migrationPath = buildMigrationPath(guides, localVersion, remoteVersion)
      if (migrationPath.pathLabel) {
        console.log('\nSuggested Version Path:')
        console.log(migrationPath.pathLabel)

        if (migrationPath.actionableSteps.length > 0) {
          console.log('\nGuides With Manual Steps In This Path:')
          migrationPath.actionableSteps.forEach((step) => {
            console.log(`- ${step.name}`)
          })
        }
        else {
          console.log('\nNo manual migration steps in this path.')
        }

        if (!migrationPath.complete) {
          console.log('\nWarning: Could not build a full migration chain to the latest release.')
        }
      }
    }

    console.log('\nMigration Notes Mode:')
    console.log('1. Show guides with manual steps only (recommended)')
    console.log('2. Show all guides (maintainers)')
    const modeChoice = await askQuestion('\nEnter choice (1-2) [1]: ')
    const showAllGuides = modeChoice.trim() === '2'

    const visibleGuides = showAllGuides
      ? guides
      : guides.filter(guide => guide.manualSteps)

    if (visibleGuides.length === 0) {
      log('No migration documents found for the selected mode.', 'info')
      return
    }

    console.log('\nAvailable Migration Notes:')
    visibleGuides.forEach((guide, i) => {
      const stepType = guide.manualSteps ? 'manual' : 'empty'
      console.log(`${i + 1}. ${guide.name} [${stepType}]`)
    })

    const choice = await askQuestion('\nSelect a file number to view (or 0 to go back): ')
    const index = Number.parseInt(choice) - 1

    if (index >= 0 && index < visibleGuides.length) {
      const file = visibleGuides[index]
      log(`Fetching ${file.name}...`)

      console.log(`\n${'='.repeat(50)}`)
      console.log(file.markdown)
      console.log(`${'='.repeat(50)}\n`)
    }
  }
  catch (error) {
    log(`Failed to fetch migration notes: ${error.message}`, 'error')
  }
}

/**
 * Checks if the system meets the requirements for the CLI tool.
 * Specifically checks for the presence of the `tar` command.
 * Exits the process if requirements are not met.
 */
function checkRequirements() {
  try {
    execSync('tar --version', { stdio: 'ignore' })
  }
  catch {
    log('System "tar" command not found. This tool requires "tar" to extract files.', 'error')
    log('On Windows, ensure you are on Windows 10 or later.', 'error')
    process.exit(1)
  }
}

/**
 * The main entry point of the CLI application.
 * Displays the menu and handles user interaction.
 * @returns {Promise<void>}
 */
async function main() {
  console.log(`
   ___        _      _         ____             __     ____ _     ___
  / _ \\ _   _(_) ___| | __    / ___|___  _ __  / _|   / ___| |   |_ _|
 | | | | | | | |/ __| |/ /   | |   / _ \\| '_ \\| |_   | |   | |    | |
 | |_| | |_| | | (__|   <    | |__| (_) | | | |  _|  | |___| |___ | |
  \\__\\_\\\\__,_|_|\\___|_|\\_\\    \\____\\___/|_| |_|_|     \\____|_____|___|

  Quick Conf CLI v${CLI_VERSION}

`)

  checkRequirements()

  // Cleanup old update file if exists
  safeUnlink(`${__filename}.old`)

  log('Fetching version information...')
  const localCliVer = CLI_VERSION
  const remoteCliVer = await getRemoteCliVersion()
  const localProjVer = getLocalProjectVersion()
  let remoteProjVer = 'Unknown'
  try {
    const latestRelease = await fetchJson(`${GITHUB_API_BASE}/repos/${REPO_OWNER}/${REPO_NAME}/releases/latest`)
    remoteProjVer = latestRelease.tag_name
  }
  catch {
    // ignore
  }

  console.log('\nVersion Information:')
  console.log('--------------------------------------------------')
  console.log(`| ${'Component'.padEnd(20)} | ${'Local'.padEnd(10)} | ${'Remote'.padEnd(10)} |`)
  console.log('--------------------------------------------------')
  console.log(`| ${'CLI Tool'.padEnd(20)} | ${localCliVer.padEnd(10)} | ${remoteCliVer.padEnd(10)} |`)
  console.log(`| ${'Project Template'.padEnd(20)} | ${localProjVer.padEnd(10)} | ${remoteProjVer.padEnd(10)} |`)
  console.log('--------------------------------------------------')

  await selectPackageManager()

  await checkSelfUpdate(remoteCliVer)

  while (true) {
    console.log('\nMain Menu:')
    console.log('1. Fresh Installation in an empty folder')
    console.log('2. Fresh Installation after using the Template on GitHub')
    console.log('3. Update Template (Preserve Content)')
    console.log('4. View Migration Notes')
    console.log('5. Exit')

    const choice = await askQuestion('\nEnter your choice (1-5): ')

    switch (choice.trim()) {
      case '1':
        await freshInstall(false)
        break
      case '2':
        await freshInstall(true)
        break
      case '3':
        await updateTemplate()
        break
      case '4':
        await viewMigrationNotes()
        break
      case '5':
        log('Goodbye!')
        rl.close()
        process.exit(0)
        break
      default:
        log('Invalid choice, please try again.', 'warn')
    }
  }
}

main().catch((err) => {
  console.error(err)
  process.exit(1)
})