import { createHash, randomBytes, scryptSync, timingSafeEqual } from 'node:crypto'
import { createReadStream, existsSync, mkdirSync, readFileSync, statSync } from 'node:fs'
import { extname, join, normalize, resolve } from 'node:path'
import { execFileSync } from 'node:child_process'
import http from 'node:http'

const port = Number(process.env.PORT ?? 9174)
const publicDir = resolve(process.env.PUBLIC_DIR ?? 'dist')
const dataDir = resolve(process.env.LIBREBIBLE_DATA_DIR ?? '../libre-bible-data/packages/json')
const stateDir = resolve(process.env.STATE_DIR ?? 'web-state')
const dbPath = resolve(process.env.DB_PATH ?? join(stateDir, 'libre-study-web.sqlite3'))
const deployInfoPath = process.env.DEPLOY_INFO_PATH ? resolve(process.env.DEPLOY_INFO_PATH) : ''
const sqliteBin = process.env.SQLITE_BIN ?? 'sqlite3'
const maxBodyBytes = Number(process.env.MAX_BODY_BYTES ?? 4 * 1024 * 1024)
const sessionCookieName = process.env.SESSION_COOKIE_NAME ?? 'libre_study_session'
const bootstrapUser = process.env.LIBRESTUDY_BOOTSTRAP_USER ?? ''
const bootstrapPassword = process.env.LIBRESTUDY_BOOTSTRAP_PASSWORD ?? ''

const mimeTypes = new Map([
  ['.css', 'text/css; charset=utf-8'],
  ['.html', 'text/html; charset=utf-8'],
  ['.ico', 'image/x-icon'],
  ['.js', 'application/javascript; charset=utf-8'],
  ['.json', 'application/json; charset=utf-8'],
  ['.jsonl', 'application/x-ndjson; charset=utf-8'],
  ['.map', 'application/json; charset=utf-8'],
  ['.png', 'image/png'],
  ['.svg', 'image/svg+xml'],
  ['.txt', 'text/plain; charset=utf-8'],
  ['.woff2', 'font/woff2'],
])

mkdirSync(stateDir, { recursive: true })
sqlite(`
CREATE TABLE IF NOT EXISTS users (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  username TEXT NOT NULL UNIQUE,
  password_hash TEXT NOT NULL,
  created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP,
  updated_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE IF NOT EXISTS login_sessions (
  token_hash TEXT PRIMARY KEY,
  user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP,
  expires_at TEXT NOT NULL
);

CREATE TABLE IF NOT EXISTS workspace_state (
  user_id INTEGER PRIMARY KEY REFERENCES users(id) ON DELETE CASCADE,
  state_json TEXT NOT NULL,
  updated_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
);
`)
ensureWorkspaceStateSchema()
bootstrapAccount()
migrateLegacyWorkspaceToBootstrap()

function sqlite(sql) {
  const output = execFileSync(sqliteBin, ['-json', dbPath, sql], {
    encoding: 'utf8',
    maxBuffer: 1024 * 1024 * 20,
  })
  return output.trim() ? JSON.parse(output) : []
}

function quoteSql(value) {
  return `'${String(value).replaceAll("'", "''")}'`
}

function passwordHash(password) {
  const salt = randomBytes(16).toString('hex')
  const hash = scryptSync(password, salt, 64).toString('hex')
  return `scrypt:${salt}:${hash}`
}

function verifyPassword(password, stored) {
  const [scheme, salt, expected] = String(stored).split(':')
  if (scheme !== 'scrypt' || !salt || !expected) return false
  const actual = scryptSync(password, salt, 64)
  const expectedBuffer = Buffer.from(expected, 'hex')
  return actual.length === expectedBuffer.length && timingSafeEqual(actual, expectedBuffer)
}

function tokenHash(token) {
  return createHash('sha256').update(token).digest('hex')
}

function parseCookies(header = '') {
  const cookies = new Map()
  for (const pair of header.split(';')) {
    const [name, ...valueParts] = pair.trim().split('=')
    if (!name || !valueParts.length) continue
    cookies.set(name, decodeURIComponent(valueParts.join('=')))
  }
  return cookies
}

function sessionCookie(token, expiresAt) {
  return `${sessionCookieName}=${encodeURIComponent(token)}; Path=/; HttpOnly; SameSite=Lax; Expires=${new Date(expiresAt).toUTCString()}`
}

function expiredSessionCookie() {
  return `${sessionCookieName}=; Path=/; HttpOnly; SameSite=Lax; Expires=Thu, 01 Jan 1970 00:00:00 GMT`
}

function bootstrapAccount() {
  if (!bootstrapUser || !bootstrapPassword) return
  const existing = sqlite(`SELECT id FROM users WHERE username = ${quoteSql(bootstrapUser)} LIMIT 1;`)
  if (existing.length) return
  sqlite(
    `INSERT INTO users (username, password_hash)
     VALUES (${quoteSql(bootstrapUser)}, ${quoteSql(passwordHash(bootstrapPassword))});`,
  )
}

function ensureWorkspaceStateSchema() {
  const columns = sqlite('PRAGMA table_info(workspace_state);')
  if (columns.some((column) => column.name === 'user_id')) return
  sqlite('ALTER TABLE workspace_state RENAME TO workspace_state_legacy;')
  sqlite(`
CREATE TABLE workspace_state (
  user_id INTEGER PRIMARY KEY REFERENCES users(id) ON DELETE CASCADE,
  state_json TEXT NOT NULL,
  updated_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
);
`)
}

function migrateLegacyWorkspaceToBootstrap() {
  if (!bootstrapUser) return
  const legacyTable = sqlite(
    `SELECT name FROM sqlite_master WHERE type = 'table' AND name = 'workspace_state_legacy';`,
  )
  if (!legacyTable.length) return
  const user = sqlite(`SELECT id FROM users WHERE username = ${quoteSql(bootstrapUser)} LIMIT 1;`)
  if (!user.length) return
  const existing = sqlite(`SELECT user_id FROM workspace_state WHERE user_id = ${Number(user[0].id)};`)
  if (existing.length) return
  const legacy = sqlite(`SELECT state_json FROM workspace_state_legacy ORDER BY updated_at DESC LIMIT 1;`)
  if (!legacy.length) return
  sqlite(
    `INSERT INTO workspace_state (user_id, state_json, updated_at)
     VALUES (${Number(user[0].id)}, json(${quoteSql(legacy[0].state_json)}), CURRENT_TIMESTAMP);`,
  )
}

function sendJson(response, status, value) {
  const body = JSON.stringify(value)
  response.writeHead(status, {
    'Content-Type': 'application/json; charset=utf-8',
    'Content-Length': Buffer.byteLength(body),
    'Cache-Control': 'no-store',
  })
  response.end(body)
}

function sendJsonWithHeaders(response, status, value, headers = {}) {
  const body = JSON.stringify(value)
  response.writeHead(status, {
    'Content-Type': 'application/json; charset=utf-8',
    'Content-Length': Buffer.byteLength(body),
    'Cache-Control': 'no-store',
    ...headers,
  })
  response.end(body)
}

function sendText(response, status, value) {
  response.writeHead(status, {
    'Content-Type': 'text/plain; charset=utf-8',
    'Content-Length': Buffer.byteLength(value),
    'Cache-Control': 'no-store',
  })
  response.end(value)
}

function readBody(request) {
  return new Promise((resolveBody, reject) => {
    let size = 0
    const chunks = []
    request.on('data', (chunk) => {
      size += chunk.length
      if (size > maxBodyBytes) {
        reject(new Error('Request body is too large.'))
        request.destroy()
        return
      }
      chunks.push(chunk)
    })
    request.on('end', () => resolveBody(Buffer.concat(chunks).toString('utf8')))
    request.on('error', reject)
  })
}

function safeFile(root, requestPath) {
  const decoded = decodeURIComponent(requestPath)
  const candidate = normalize(join(root, decoded))
  const rootWithSeparator = root.endsWith('\\') || root.endsWith('/') ? root : `${root}/`
  if (candidate !== root && !candidate.startsWith(rootWithSeparator)) return null
  return candidate
}

function serveFile(response, filePath, cache = 'no-store') {
  if (!existsSync(filePath) || !statSync(filePath).isFile()) return false

  const stat = statSync(filePath)
  const contentType = mimeTypes.get(extname(filePath).toLowerCase()) ?? 'application/octet-stream'
  response.writeHead(200, {
    'Content-Type': contentType,
    'Content-Length': stat.size,
    'Cache-Control': cache,
  })
  createReadStream(filePath).pipe(response)
  return true
}

function serveStatic(response, requestPath) {
  const pathWithoutSlash = requestPath.replace(/^\/+/, '')
  const staticPath = safeFile(publicDir, pathWithoutSlash || 'index.html')
  if (staticPath && serveFile(response, staticPath, requestPath.startsWith('/assets/') ? 'public, max-age=31536000, immutable' : 'no-store')) {
    return true
  }

  return serveFile(response, join(publicDir, 'index.html'), 'no-store')
}

function serveLibreBible(response, requestPath) {
  const relative = requestPath.replace(/^\/librebible\/?/, '')
  const filePath = safeFile(dataDir, relative)
  if (!filePath || !serveFile(response, filePath, 'public, max-age=300')) {
    sendText(response, 404, 'Not found')
  }
}

function deployInfo() {
  if (!deployInfoPath || !existsSync(deployInfoPath)) return { commit: 'unknown' }

  try {
    return JSON.parse(readFileSync(deployInfoPath, 'utf8'))
  } catch {
    return { commit: readFileSync(deployInfoPath, 'utf8').trim() || 'unknown' }
  }
}

async function handleApi(request, response, url) {
  if (url.pathname === '/api/health') {
    sendJson(response, 200, { ok: true, deploy: deployInfo() })
    return
  }

  if (url.pathname === '/api/session' && request.method === 'GET') {
    const user = currentUser(request)
    sendJson(response, 200, { authenticated: Boolean(user), user })
    return
  }

  if (url.pathname === '/api/login' && request.method === 'POST') {
    const body = await readBody(request)
    let parsed
    try {
      parsed = JSON.parse(body)
    } catch {
      sendJson(response, 400, { error: 'Login payload must be valid JSON.' })
      return
    }

    const username = String(parsed.username ?? '').trim()
    const password = String(parsed.password ?? '')
    const rows = username
      ? sqlite(`SELECT id, username, password_hash FROM users WHERE username = ${quoteSql(username)} LIMIT 1;`)
      : []

    if (!rows.length || !verifyPassword(password, rows[0].password_hash)) {
      sendJson(response, 401, { error: 'Invalid username or password.' })
      return
    }

    const token = randomBytes(32).toString('base64url')
    const expiresAt = new Date(Date.now() + 1000 * 60 * 60 * 24 * 30).toISOString()
    sqlite(
      `INSERT INTO login_sessions (token_hash, user_id, expires_at)
       VALUES (${quoteSql(tokenHash(token))}, ${Number(rows[0].id)}, ${quoteSql(expiresAt)});`,
    )
    sendJsonWithHeaders(
      response,
      200,
      { authenticated: true, user: { id: Number(rows[0].id), username: rows[0].username } },
      { 'Set-Cookie': sessionCookie(token, expiresAt) },
    )
    return
  }

  if (url.pathname === '/api/logout' && request.method === 'POST') {
    const cookies = parseCookies(request.headers.cookie)
    const token = cookies.get(sessionCookieName)
    if (token) sqlite(`DELETE FROM login_sessions WHERE token_hash = ${quoteSql(tokenHash(token))};`)
    sendJsonWithHeaders(response, 200, { ok: true }, { 'Set-Cookie': expiredSessionCookie() })
    return
  }

  if (url.pathname === '/api/workspace' && request.method === 'GET') {
    const user = requireUser(request, response)
    if (!user) return
    const rows = sqlite(`SELECT state_json FROM workspace_state WHERE user_id = ${user.id};`)
    if (!rows.length) {
      response.writeHead(204, { 'Cache-Control': 'no-store' })
      response.end()
      return
    }

    response.writeHead(200, {
      'Content-Type': 'application/json; charset=utf-8',
      'Cache-Control': 'no-store',
    })
    response.end(rows[0].state_json)
    return
  }

  if (url.pathname === '/api/workspace' && request.method === 'PUT') {
    const user = requireUser(request, response)
    if (!user) return
    const body = await readBody(request)
    let parsed
    try {
      parsed = JSON.parse(body)
    } catch {
      sendJson(response, 400, { error: 'Workspace payload must be valid JSON.' })
      return
    }

    sqlite(
      `INSERT INTO workspace_state (user_id, state_json, updated_at)
       VALUES (${user.id}, json(${quoteSql(JSON.stringify(parsed))}), CURRENT_TIMESTAMP)
       ON CONFLICT(user_id) DO UPDATE SET state_json = excluded.state_json, updated_at = CURRENT_TIMESTAMP;`,
    )
    sendJson(response, 200, {
      ok: true,
      checksum: createHash('sha256').update(JSON.stringify(parsed)).digest('hex'),
    })
    return
  }

  sendJson(response, 404, { error: 'Unknown API route.' })
}

function currentUser(request) {
  const cookies = parseCookies(request.headers.cookie)
  const token = cookies.get(sessionCookieName)
  if (!token) return null
  const rows = sqlite(
    `SELECT users.id, users.username
     FROM login_sessions
     JOIN users ON users.id = login_sessions.user_id
     WHERE login_sessions.token_hash = ${quoteSql(tokenHash(token))}
       AND login_sessions.expires_at > CURRENT_TIMESTAMP
     LIMIT 1;`,
  )
  if (!rows.length) return null
  return { id: Number(rows[0].id), username: rows[0].username }
}

function requireUser(request, response) {
  const user = currentUser(request)
  if (!user) sendJson(response, 401, { error: 'Login is required.' })
  return user
}

const server = http.createServer((request, response) => {
  const url = new URL(request.url ?? '/', 'http://localhost')

  Promise.resolve()
    .then(() => {
      if (url.pathname.startsWith('/api/')) return handleApi(request, response, url)
      if (url.pathname.startsWith('/librebible/')) return serveLibreBible(response, url.pathname)
      return serveStatic(response, url.pathname)
    })
    .catch((error) => {
      sendJson(response, 500, { error: String(error.message ?? error) })
    })
})

server.listen(port, '127.0.0.1', () => {
  console.log(`Libre Study web server listening on http://127.0.0.1:${port}`)
  console.log(`Serving app from ${publicDir}`)
  console.log(`Serving LibreBible data from ${dataDir}`)
  console.log(`Persisting workspace to ${dbPath}`)
})