import type { Context, Hono } from 'hono'
import { sign, verify } from 'hono/jwt'
import { getCookie, setCookie, deleteCookie } from 'hono/cookie'

/**
 * Pluggable OpenID Connect sign-in with a guest fallback.
 *
 * - Providers are configured from env and auto-detected:
 *     Hugging Face  → OAUTH_CLIENT_ID / OAUTH_CLIENT_SECRET (injected by `hf_oauth: true`)
 *     Google        → GOOGLE_CLIENT_ID / GOOGLE_CLIENT_SECRET
 *   (any OIDC provider can be added the same way.)
 * - AUTH_REQUIRED=true forces sign-in. Otherwise anyone may use the app as a guest, and
 *   signing in simply upgrades them to their real identity.
 */
export interface SessionUser {
  id: string
  name: string
  avatar?: string
  provider?: string
}

const SECRET = process.env.SESSION_SECRET || 'dev-insecure-secret-change-me'
const ALG = 'HS256' as const
const SESSION_COOKIE = 'ms_session'
const STATE_COOKIE = 'ms_oauth_state'
const WEEK = 60 * 60 * 24 * 7

interface ProviderConfig {
  id: string
  label: string
  clientId: string
  clientSecret: string
  discoveryUrl: string
  scopes: string
}

function loadProviders(): ProviderConfig[] {
  const list: ProviderConfig[] = []
  const hfId = process.env.OAUTH_CLIENT_ID
  const hfSecret = process.env.OAUTH_CLIENT_SECRET
  if (hfId && hfSecret) {
    const base = process.env.OPENID_PROVIDER_URL || 'https://huggingface.co'
    list.push({
      id: 'hf',
      label: 'Hugging Face',
      clientId: hfId,
      clientSecret: hfSecret,
      discoveryUrl: `${base}/.well-known/openid-configuration`,
      scopes: process.env.OAUTH_SCOPES || 'openid profile',
    })
  }
  const gId = process.env.GOOGLE_CLIENT_ID
  const gSecret = process.env.GOOGLE_CLIENT_SECRET
  if (gId && gSecret) {
    list.push({
      id: 'google',
      label: 'Google',
      clientId: gId,
      clientSecret: gSecret,
      discoveryUrl: 'https://accounts.google.com/.well-known/openid-configuration',
      scopes: 'openid profile email',
    })
  }
  return list
}

const PROVIDERS = loadProviders()
export const providers = PROVIDERS.map((p) => ({ id: p.id, label: p.label }))
export const authRequired = process.env.AUTH_REQUIRED === 'true'

interface Discovery {
  authorization_endpoint: string
  token_endpoint: string
  userinfo_endpoint: string
}
const discoveryCache = new Map<string, Discovery>()
async function getDiscovery(p: ProviderConfig): Promise<Discovery> {
  let d = discoveryCache.get(p.id)
  if (!d) {
    const res = await fetch(p.discoveryUrl)
    d = (await res.json()) as Discovery
    discoveryCache.set(p.id, d)
  }
  return d
}

function publicOrigin(c: Context): string {
  if (process.env.SPACE_HOST) return `https://${process.env.SPACE_HOST}`
  const proto = c.req.header('x-forwarded-proto') || 'https'
  const host = c.req.header('x-forwarded-host') || c.req.header('host') || 'localhost'
  return `${proto}://${host}`
}
const redirectUri = (c: Context, id: string) => `${publicOrigin(c)}/api/auth/callback/${id}`

export async function verifySessionToken(token?: string): Promise<SessionUser | null> {
  if (!token) return null
  try {
    const payload = (await verify(token, SECRET, ALG)) as { user?: SessionUser }
    return payload.user ?? null
  } catch {
    return null
  }
}

/** Read the signed-in user from the httpOnly session cookie (for REST routes). */
export async function getSessionUser(c: Context): Promise<SessionUser | null> {
  const session = getCookie(c, SESSION_COOKIE)
  if (!session) return null
  try {
    return ((await verify(session, SECRET, ALG)) as { user?: SessionUser }).user ?? null
  } catch {
    return null
  }
}

export function registerAuth(app: Hono): void {
  app.get('/api/auth/me', async (c) => {
    let user: SessionUser | null = null
    const session = getCookie(c, SESSION_COOKIE)
    if (session) {
      try {
        user = ((await verify(session, SECRET, ALG)) as { user?: SessionUser }).user ?? null
      } catch {
        /* expired / invalid */
      }
    }
    const collabToken = user
      ? await sign({ user, exp: Math.floor(Date.now() / 1000) + 3600 }, SECRET, ALG)
      : null
    return c.json({ providers, authRequired, user, collabToken })
  })

  app.get('/api/auth/login/:provider', async (c) => {
    const p = PROVIDERS.find((x) => x.id === c.req.param('provider'))
    if (!p) return c.redirect('/')
    const d = await getDiscovery(p)
    const state = `${p.id}:${crypto.randomUUID()}`
    setCookie(c, STATE_COOKIE, state, {
      httpOnly: true,
      secure: true,
      sameSite: 'Lax',
      maxAge: 600,
      path: '/',
    })
    const url = new URL(d.authorization_endpoint)
    url.searchParams.set('client_id', p.clientId)
    url.searchParams.set('redirect_uri', redirectUri(c, p.id))
    url.searchParams.set('response_type', 'code')
    url.searchParams.set('scope', p.scopes)
    url.searchParams.set('state', state)
    return c.redirect(url.toString())
  })

  app.get('/api/auth/callback/:provider', async (c) => {
    const p = PROVIDERS.find((x) => x.id === c.req.param('provider'))
    if (!p) return c.redirect('/')
    const code = c.req.query('code')
    const state = c.req.query('state')
    if (!code || !state || state !== getCookie(c, STATE_COOKIE)) {
      return c.text('Invalid OAuth state', 400)
    }
    const d = await getDiscovery(p)
    const basic = Buffer.from(`${p.clientId}:${p.clientSecret}`).toString('base64')
    const tokenRes = await fetch(d.token_endpoint, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
        Authorization: `Basic ${basic}`,
      },
      body: new URLSearchParams({
        grant_type: 'authorization_code',
        code,
        redirect_uri: redirectUri(c, p.id),
        client_id: p.clientId,
      }),
    })
    if (!tokenRes.ok) return c.text('Token exchange failed', 401)
    const token = (await tokenRes.json()) as { access_token: string }

    const userRes = await fetch(d.userinfo_endpoint, {
      headers: { Authorization: `Bearer ${token.access_token}` },
    })
    const info = (await userRes.json()) as {
      sub: string
      name?: string
      preferred_username?: string
      email?: string
      picture?: string
    }
    const user: SessionUser = {
      id: `${p.id}:${info.sub}`,
      name: info.preferred_username || info.name || info.email || 'User',
      avatar: info.picture,
      provider: p.id,
    }

    deleteCookie(c, STATE_COOKIE, { path: '/' })
    const session = await sign({ user, exp: Math.floor(Date.now() / 1000) + WEEK }, SECRET, ALG)
    setCookie(c, SESSION_COOKIE, session, {
      httpOnly: true,
      secure: true,
      sameSite: 'Lax',
      maxAge: WEEK,
      path: '/',
    })
    return c.redirect('/')
  })

  app.get('/api/auth/logout', (c) => {
    deleteCookie(c, SESSION_COOKIE, { path: '/' })
    return c.redirect('/')
  })
}