// src/server/session.ts
import {
  getRequestHeader,
  setResponseHeader,
} from '@tanstack/react-start/server'

const SESSION_COOKIE = '__Host-session' // __Host- prefix binds to the exact origin + path '/'
const ONE_DAY = 60 * 60 * 24

export function setSessionCookie(token: string) {
  setResponseHeader(
    'Set-Cookie',
    [
      `${SESSION_COOKIE}=${token}`,
      `HttpOnly`, // not readable from JS — defeats XSS exfiltration
      `Secure`, // HTTPS only (required for __Host- prefix)
      `SameSite=Lax`, // sent on top-level navigations, blocks most CSRF
      `Path=/`, // required for __Host- prefix
      `Max-Age=${ONE_DAY}`,
    ].join('; '),
  )
}

export function clearSessionCookie() {
  setResponseHeader(
    'Set-Cookie',
    `${SESSION_COOKIE}=; HttpOnly; Secure; SameSite=Lax; Path=/; Max-Age=0`,
  )
}

export function readSessionToken(): string | null {
  const header = getRequestHeader('cookie')
  if (!header) return null
  for (const part of header.split(/;\s*/)) {
    // Split only on the FIRST '=' — signed/base64 values often contain '='.
    const eq = part.indexOf('=')
    if (eq === -1) continue
    if (part.slice(0, eq) === SESSION_COOKIE) return part.slice(eq + 1)
  }
  return null
}

// src/server/auth-middleware.ts
import { createMiddleware } from '@tanstack/react-start'
import { readSessionToken } from './session'

export const authMiddleware = createMiddleware({ type: 'function' }).server(
  async ({ next }) => {
    const token = readSessionToken()
    const session = token ? await db.sessions.findValid(token) : null
    if (!session) throw new Error('Unauthorized')
    return next({ context: { session } })
  },
)

import { createServerFn } from '@tanstack/react-start'
import { authMiddleware } from '~/server/auth-middleware'

export const getMyOrders = createServerFn({ method: 'GET' })
  .middleware([authMiddleware])
  .handler(async ({ context }) => {
    return db.orders.findMany({ where: { userId: context.session.userId } })
  })

// src/server/login.functions.ts
import { createServerFn } from '@tanstack/react-start'
import { z } from 'zod'
import { setSessionCookie } from './session'

export const login = createServerFn({ method: 'POST' })
  .validator(z.object({ email: z.string().email(), password: z.string() }))
  .handler(async ({ data }) => {
    const user = await db.users.findByEmail(data.email)
    // Always run verifyPasswordHash — even when the user doesn't exist —
    // so the user-not-found branch takes the same time as wrong-password.
    // DUMMY_PASSWORD_HASH is a hash of any throwaway password computed once
    // at startup with the same algorithm/cost as real password hashes.
    const hashToCheck = user?.passwordHash ?? DUMMY_PASSWORD_HASH
    const passwordMatches = await verifyPasswordHash(hashToCheck, data.password)
    const ok = user != null && passwordMatches
    if (!ok) throw new Error('Invalid email or password')

    // ROTATE on privilege change: destroy any existing session, then issue fresh.
    await db.sessions.revokeAllForUser(user.id)
    const token = await db.sessions.create({ userId: user.id })
    setSessionCookie(token)
    return { ok: true }
  })

import { createServerFn } from '@tanstack/react-start'
import { authMiddleware } from '~/server/auth-middleware'
import { clearSessionCookie } from '~/server/session'

export const logout = createServerFn({ method: 'POST' })
  .middleware([authMiddleware])
  .handler(async ({ context }) => {
    await db.sessions.revoke(context.session.id)
    clearSessionCookie()
    return { ok: true }
  })

// src/server/oauth.functions.ts
import { createServerFn } from '@tanstack/react-start'
import { redirect } from '@tanstack/react-router'
import {
  getRequestHeader,
  setResponseHeader,
} from '@tanstack/react-start/server'
import crypto from 'node:crypto'

const OAUTH_STATE_COOKIE = '__Host-oauth' // expires fast; one-shot

function base64url(buf: Buffer) {
  return buf
    .toString('base64')
    .replace(/=/g, '')
    .replace(/\+/g, '-')
    .replace(/\//g, '_')
}

export const startOAuth = createServerFn({ method: 'GET' }).handler(
  async () => {
    const state = base64url(crypto.randomBytes(32))
    const verifier = base64url(crypto.randomBytes(32))
    const challenge = base64url(
      crypto.createHash('sha256').update(verifier).digest(),
    )

    setResponseHeader(
      'Set-Cookie',
      `${OAUTH_STATE_COOKIE}=${signed({ state, verifier })}; HttpOnly; Secure; SameSite=Lax; Path=/; Max-Age=600`,
    )

    throw redirect({
      href:
        `https://provider.example/authorize` +
        `?response_type=code` +
        `&client_id=${process.env.OAUTH_CLIENT_ID}` +
        `&redirect_uri=${encodeURIComponent(process.env.OAUTH_REDIRECT_URI!)}` +
        `&state=${state}` +
        `&code_challenge=${challenge}` +
        `&code_challenge_method=S256`,
    })
  },
)

import { createServerFn } from '@tanstack/react-start'
import { z } from 'zod'

export const requestPasswordReset = createServerFn({ method: 'POST' })
  .validator(z.object({ email: z.string().email() }))
  .handler(async ({ data }) => {
    const user = await db.users.findByEmail(data.email)
    if (user) {
      const token = await db.passwordResets.issue(user.id)
      await sendResetEmail(user.email, token)
    }
    // Always 200, always the same body, regardless of whether the user exists.
    // The user is told to check their inbox; no confirmation either way.
    return { ok: true }
  })

import { createMiddleware } from '@tanstack/react-start'
import { getRequest } from '@tanstack/react-start/server'

export const csrfMiddleware = createMiddleware().server(async ({ next }) => {
  const request = getRequest()
  if (request.method !== 'GET' && request.method !== 'HEAD') {
    const origin = request.headers.get('origin')
    // Compare the FULL origin (scheme + host + port) — host alone lets
    // http://example.com pass a check meant for https://example.com.
    if (!origin || new URL(origin).origin !== process.env.APP_ORIGIN) {
      throw new Error('Origin check failed')
    }
  }
  return next()
})

import { createMiddleware } from '@tanstack/react-start'
import { getRequest } from '@tanstack/react-start/server'

function rateLimitMiddleware(opts: {
  key: string
  max: number
  windowMs: number
}) {
  return createMiddleware().server(async ({ next }) => {
    const request = getRequest()
    const ip =
      request.headers.get('cf-connecting-ip') ??
      request.headers.get('x-forwarded-for')?.split(',')[0] ??
      'unknown'
    const bucketKey = `rl:${opts.key}:${ip}`
    const allowed = await rateLimiter.consume(
      bucketKey,
      opts.max,
      opts.windowMs,
    )
    if (!allowed) throw new Error('Too many requests')
    return next()
  })
}

// On the login server function:
export const login = createServerFn({ method: 'POST' }).middleware([
  rateLimitMiddleware({ key: 'login', max: 5, windowMs: 60_000 }),
])
// ...

// In the login handler (already shown above): destroy any pre-login session, then create a fresh one.
await db.sessions.revokeAllForUser(user.id)
const token = await db.sessions.create({ userId: user.id })
setSessionCookie(token)

// On password change / role grant:
await db.sessions.revokeAllForUser(user.id) // destroy existing
const token = await db.sessions.create({ userId: user.id }) // issue fresh
setSessionCookie(token)

// WRONG — the RPC is callable directly via POST regardless of the route
export const Route = createFileRoute('/_authenticated/orders')({
  beforeLoad: ({ context }) => {
    if (!context.auth.isAuthenticated) throw redirect({ to: '/login' })
  },
})
const getMyOrders = createServerFn({ method: 'GET' }).handler(async () => {
  return db.orders.findMany() // ← anyone can hit the RPC and get all orders
})

// CORRECT — auth enforced on the handler itself
const getMyOrders = createServerFn({ method: 'GET' })
  .middleware([authMiddleware])
  .handler(async ({ context }) => {
    return db.orders.findMany({ where: { userId: context.session.userId } })
  })

// WRONG — UUID is well-formed but the user may not be a member
const getWorkspaceData = createServerFn({ method: 'GET' })
  .middleware([authMiddleware])
  .validator(z.object({ workspaceId: z.string().uuid() }))
  .handler(async ({ context, data }) => {
    return db.workspaces.findById(data.workspaceId) // missing membership check!
  })

// CORRECT — verify the session principal has access to that workspace
const getWorkspaceData = createServerFn({ method: 'GET' })
  .middleware([authMiddleware])
  .validator(z.object({ workspaceId: z.string().uuid() }))
  .handler(async ({ context, data }) => {
    const member = await db.memberships.find({
      userId: context.session.userId,
      workspaceId: data.workspaceId,
    })
    if (!member) throw new Error('Not a member of this workspace')
    return db.workspaces.findById(data.workspaceId)
  })

// WRONG — module-load time, before any request exists
const SESSION_SECRET = process.env.SESSION_SECRET
export function signSession(payload) {
  return sign(payload, SESSION_SECRET)
}

// CORRECT — read inside per-request callback
export function signSession(payload) {
  return sign(payload, process.env.SESSION_SECRET)
}