package main

import (
	"fmt"
	"log"
	"math/rand/v2"
	"sync"

	"github.com/gofiber/fiber/v2"
	"github.com/gofiber/fiber/v2/middleware/logger"
)

func main() {
	app := fiber.New()
	app.Use(logger.New())

	app.Post("/api/v3/auth/login", handleLogin)
	app.Get("/api/v3/auth/check", handleAuthCheck)
	app.Get("/api/v3/auth/401", func(c *fiber.Ctx) error {
		return c.Status(fiber.StatusUnauthorized).JSON(fiber.Map{
			"err": "custom err 401",
		})
	})

	log.Fatal(app.Listen(":3000"))
}

type User struct {
	Username string `json:"username"`
	Password string `json:"password"`
}

var (
	store     = &sync.Map{}
	letters   = []byte("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
	mockUsers = map[string]User{
		"admin": {
			Username: "admin",
			Password: "123456",
		},
		"user": {
			Username: "user",
			Password: "12345678",
		},
	}
)

func randomString(n int) string {
	b := make([]byte, n)
	for i := range b {
		b[i] = letters[rand.IntN(len(letters))]
	}
	return string(b)
}

func handleLogin(c *fiber.Ctx) error {
	type Req struct {
		Username string `json:"username"`
		Password string `json:"password"`
	}

	var (
		err error
		req Req
	)

	if err = c.BodyParser(&req); err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
			"error": err.Error(),
		})
	}

	user, ok := mockUsers[req.Username]
	if !ok {
		return c.Status(fiber.StatusUnauthorized).JSON(fiber.Map{
			"error": "user not found",
		})
	}

	session := randomString(16)
	store.Store(session, user)
	c.Response().Header.Set("Set-Cookie", fmt.Sprintf("session=%s; Path=/; HttpOnly; SameSite=Lax", session))
	c.Response().Header.Set("Server", "Fiber")

	return c.Status(fiber.StatusOK).JSON(user)
}

func handleAuthCheck(c *fiber.Ctx) error {
	session := c.Cookies("session")
	if session == "" {
		return c.Status(fiber.StatusUnauthorized).JSON(fiber.Map{
			"error": "unauthorized",
		})
	}

	user, ok := store.Load(session)
	if !ok {
		return c.Status(fiber.StatusUnauthorized).JSON(fiber.Map{
			"error": "unauthorized",
		})
	}

	return c.Status(fiber.StatusOK).JSON(user)
}