package services

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"platform/pkg/env"
	"platform/web/auth"
	g "platform/web/globals"
	"time"

	"github.com/google/uuid"
	"github.com/redis/go-redis/v9"
)

// region SessionService

var Session SessionServiceInter = &sessionService{}

type SessionServiceInter interface {
	// Find 通过访问令牌获取会话信息
	Find(ctx context.Context, token string) (*auth.Context, error)
	// Create 创建一个新的会话
	Create(ctx context.Context, authCtx auth.Context, remember bool) (*TokenDetails, error)
	// Refresh 刷新一个会话
	Refresh(ctx context.Context, refreshToken string) (*TokenDetails, error)
	// Remove 删除会话
	Remove(ctx context.Context, accessToken, refreshToken string) error
}

type SessionServiceError string

func (e SessionServiceError) Error() string {
	return string(e)
}

var (
	ErrInvalidToken = SessionServiceError("invalid_token")
)

type sessionService struct{}

// Find 通过访问令牌获取会话信息
func (s *sessionService) Find(ctx context.Context, token string) (*auth.Context, error) {

	// 读取认证数据
	authJSON, err := g.Redis.Get(ctx, accessKey(token)).Result()
	if err != nil {
		if errors.Is(err, redis.Nil) {
			return nil, ErrInvalidToken
		}
		return nil, err
	}

	// 反序列化
	authCtx := new(auth.Context)
	if err := json.Unmarshal([]byte(authJSON), authCtx); err != nil {
		return nil, err
	}

	return authCtx, nil
}

// Create 创建一个新的会话
func (s *sessionService) Create(ctx context.Context, authCtx auth.Context, remember bool) (*TokenDetails, error) {
	var now = time.Now()

	// 生成令牌组
	accessToken := genToken()
	refreshToken := genToken()

	// 序列化认证数据
	authData, err := json.Marshal(authCtx)
	if err != nil {
		return nil, err
	}

	// 序列化刷新令牌数据
	refreshData, err := json.Marshal(RefreshData{
		AuthContext: authCtx,
		AccessToken: accessToken,
	})
	if err != nil {
		return nil, err
	}

	// 事务保存数据到 Redis
	var accessExpire = time.Duration(env.SessionAccessExpire) * time.Second
	var refreshExpire = time.Duration(env.SessionRefreshExpire) * time.Second

	pipe := g.Redis.TxPipeline()
	pipe.Set(ctx, accessKey(accessToken), authData, accessExpire)
	if remember {
		pipe.Set(ctx, refreshKey(refreshToken), refreshData, refreshExpire)
	}
	_, err = pipe.Exec(ctx)
	if err != nil {
		return nil, err
	}

	return &TokenDetails{
		AccessToken:         accessToken,
		AccessTokenExpires:  now.Add(accessExpire),
		RefreshToken:        refreshToken,
		RefreshTokenExpires: now.Add(refreshExpire),
		Auth:                authCtx,
	}, nil
}

// Refresh 刷新一个会话
func (s *sessionService) Refresh(ctx context.Context, refreshToken string) (*TokenDetails, error) {
	var now = time.Now()

	rKey := refreshKey(refreshToken)
	var tokenDetails *TokenDetails

	// 刷新令牌
	err := g.Redis.Watch(ctx, func(tx *redis.Tx) error {

		// 先获取刷新令牌数据
		refreshJson, err := tx.Get(ctx, rKey).Result()
		if err != nil {
			if errors.Is(err, redis.Nil) {
				return ErrInvalidToken
			}
			return err
		}

		// 解析刷新令牌数据
		refreshData := new(RefreshData)
		if err := json.Unmarshal([]byte(refreshJson), refreshData); err != nil {
			return err
		}

		// 生成新的令牌
		newAccessToken := genToken()
		newRefreshToken := genToken()

		authData, err := json.Marshal(refreshData.AuthContext)
		if err != nil {
			return err
		}
		newRefreshData, err := json.Marshal(RefreshData{
			AuthContext: refreshData.AuthContext,
			AccessToken: newAccessToken,
		})
		if err != nil {
			return err
		}

		pipeline := tx.Pipeline()

		// 保存新的令牌
		var accessExpire = time.Duration(env.SessionAccessExpire) * time.Second
		var refreshExpire = time.Duration(env.SessionRefreshExpire) * time.Second

		pipeline.Set(ctx, accessKey(newAccessToken), authData, accessExpire)
		pipeline.Set(ctx, refreshKey(newRefreshToken), newRefreshData, refreshExpire)

		// 删除旧的令牌
		pipeline.Del(ctx, accessKey(refreshData.AccessToken))
		pipeline.Del(ctx, refreshKey(refreshToken))

		_, err = pipeline.Exec(ctx)
		if err != nil {
			return err
		}

		tokenDetails = &TokenDetails{
			AccessToken:         newAccessToken,
			RefreshToken:        newRefreshToken,
			AccessTokenExpires:  now.Add(accessExpire),
			RefreshTokenExpires: now.Add(refreshExpire),
			Auth:                refreshData.AuthContext,
		}
		return nil
	}, rKey)
	if err != nil {
		return nil, fmt.Errorf("刷新令牌失败: %w", err)
	}

	return tokenDetails, nil
}

// Remove 删除会话
func (s *sessionService) Remove(ctx context.Context, accessToken, refreshToken string) error {
	g.Redis.Del(ctx, accessKey(accessToken), refreshKey(refreshToken))
	return nil
}

// 生成一个新的令牌
func genToken() string {
	return uuid.NewString()
}

// 令牌键的格式为 "session:<token>"
func accessKey(token string) string {
	return fmt.Sprintf("session:%s", token)
}

// 刷新令牌键的格式为 "session:refreshKey:<token>"
func refreshKey(token string) string {
	return fmt.Sprintf("session:refresh:%s", token)
}

// endregion

type RefreshData struct {
	AuthContext auth.Context
	AccessToken string
}

// TokenDetails 存储令牌详细信息
type TokenDetails struct {
	// 访问令牌
	AccessToken string
	// 刷新令牌
	RefreshToken string
	// 访问令牌过期时间
	AccessTokenExpires time.Time
	// 刷新令牌过期时间
	RefreshTokenExpires time.Time
	// 认证信息
	Auth auth.Context
}