import { getCookie, deleteCookie, setCookie, getRequestURL } from 'h3'
import {
  getOidcConfig,
  constantTimeCompare,
  validateRedirectPath,
  exchangeCode,
} from '../../../utils/oidc.js'
import { getDb } from '../../../utils/db.js'
import { getSessionMaxAgeDays } from '../../../utils/constants.js'

const DEFAULT_ROLE = process.env.OIDC_DEFAULT_ROLE || 'member'

function getIdentifier(claims) {
  return claims?.email ?? claims?.preferred_username ?? claims?.name ?? claims?.sub ?? 'oidc-user'
}

export default defineEventHandler(async (event) => {
  const query = getQuery(event)
  const code = query?.code
  const state = query?.state
  if (!code || !state) throw createError({ statusCode: 400, message: 'Invalid request' })

  const cookieRaw = getCookie(event, 'oidc_state')
  if (!cookieRaw) throw createError({ statusCode: 400, message: 'Invalid request' })
  let stored
  try {
    stored = JSON.parse(cookieRaw)
  }
  catch {
    throw createError({ statusCode: 400, message: 'Invalid request' })
  }
  if (!stored?.state || !constantTimeCompare(state, stored.state)) {
    throw createError({ statusCode: 400, message: 'Invalid request' })
  }

  const config = await getOidcConfig()
  if (!config) throw createError({ statusCode: 500, message: 'OIDC not configured' })

  const currentUrl = getRequestURL(event)
  const checks = {
    expectedState: state,
    expectedNonce: stored.nonce,
    pkceCodeVerifier: stored.codeVerifier,
  }

  let tokens
  try {
    tokens = await exchangeCode(config, currentUrl, checks)
  }
  catch {
    deleteCookie(event, 'oidc_state', { path: '/' })
    throw createError({ statusCode: 401, message: 'Authentication failed' })
  }

  deleteCookie(event, 'oidc_state', { path: '/' })

  const claims = tokens.claims?.()
  if (!claims?.sub) throw createError({ statusCode: 401, message: 'Authentication failed' })

  const issuer = process.env.OIDC_ISSUER ?? ''
  const { get, run } = await getDb()
  let user = await get(
    'SELECT id, identifier, role FROM users WHERE oidc_issuer = ? AND oidc_sub = ?',
    [issuer, claims.sub],
  )
  if (!user) {
    const id = crypto.randomUUID()
    const now = new Date().toISOString()
    const identifier = getIdentifier(claims)
    await run(
      'INSERT INTO users (id, identifier, password_hash, role, created_at, auth_provider, oidc_issuer, oidc_sub) VALUES (?, ?, ?, ?, ?, ?, ?, ?)',
      [id, identifier, null, DEFAULT_ROLE, now, 'oidc', issuer, claims.sub],
    )
    user = await get('SELECT id, identifier, role FROM users WHERE id = ?', [id])
  }

  // Invalidate all existing sessions for this user to prevent session fixation
  await run('DELETE FROM sessions WHERE user_id = ?', [user.id])

  const sessionDays = getSessionMaxAgeDays()
  const sid = crypto.randomUUID()
  const now = new Date()
  const expires = new Date(now.getTime() + sessionDays * 24 * 60 * 60 * 1000)
  await run(
    'INSERT INTO sessions (id, user_id, created_at, expires_at) VALUES (?, ?, ?, ?)',
    [sid, user.id, now.toISOString(), expires.toISOString()],
  )
  setCookie(event, 'session_id', sid, {
    httpOnly: true,
    sameSite: 'strict',
    path: '/',
    maxAge: sessionDays * 24 * 60 * 60,
    secure: process.env.NODE_ENV === 'production',
  })

  const redirectParam = query?.redirect
  const path = validateRedirectPath(redirectParam)
  return sendRedirect(event, path.startsWith('http') ? path : new URL(path, getRequestURL(event).origin).href, 302)
})