// Auth context: who is seated at the table. Wraps the /auth REST endpoints
// and exposes { user, checking, login, register, logout } to the app.

import { createContext, useCallback, useContext, useEffect, useMemo, useState } from 'react'
import type { ReactNode } from 'react'
import * as api from '../api'
import type { User } from '../api'

export type AuthApi = {
  user: User | null
  checking: boolean
  login: (username: string, password: string) => Promise<User>
  register: (username: string, password: string) => Promise<User>
  logout: () => Promise<void>
}

const AuthContext = createContext<AuthApi | null>(null)

export function AuthProvider({ children }: { children: ReactNode }) {
  const [user, setUser] = useState<User | null>(null)
  const [checking, setChecking] = useState(true)

  useEffect(() => {
    api
      .me()
      .then(setUser)
      .catch(() => setUser(null))
      .finally(() => setChecking(false))
  }, [])

  const login = useCallback(async (username: string, password: string) => {
    const u = await api.login(username, password)
    setUser(u)
    return u
  }, [])

  const register = useCallback(
    async (username: string, password: string) => {
      await api.register(username, password)
      return login(username, password)
    },
    [login],
  )

  const logout = useCallback(async () => {
    await api.logout()
    setUser(null)
  }, [])

  const value = useMemo<AuthApi>(
    () => ({ user, checking, login, register, logout }),
    [user, checking, login, register, logout],
  )
  return <AuthContext.Provider value={value}>{children}</AuthContext.Provider>
}

export function useAuth(): AuthApi {
  const ctx = useContext(AuthContext)
  if (!ctx) throw new Error('useAuth must be used inside <AuthProvider>')
  return ctx
}