package service

import (
	"context"
	"fmt"
	"strconv"
	"strings"
	"time"

	"github.com/Wei-Shaw/sub2api/internal/pkg/antigravity"
)

type AntigravityOAuthService struct {
	sessionStore *antigravity.SessionStore
	proxyRepo    ProxyRepository
}

func NewAntigravityOAuthService(proxyRepo ProxyRepository) *AntigravityOAuthService {
	return &AntigravityOAuthService{
		sessionStore: antigravity.NewSessionStore(),
		proxyRepo:    proxyRepo,
	}
}

// AntigravityAuthURLResult is the result of generating an authorization URL
type AntigravityAuthURLResult struct {
	AuthURL   string `json:"auth_url"`
	SessionID string `json:"session_id"`
	State     string `json:"state"`
}

// GenerateAuthURL 生成 Google OAuth 授权链接
func (s *AntigravityOAuthService) GenerateAuthURL(ctx context.Context, proxyID *int64) (*AntigravityAuthURLResult, error) {
	state, err := antigravity.GenerateState()
	if err != nil {
		return nil, fmt.Errorf("生成 state 失败: %w", err)
	}

	codeVerifier, err := antigravity.GenerateCodeVerifier()
	if err != nil {
		return nil, fmt.Errorf("生成 code_verifier 失败: %w", err)
	}

	sessionID, err := antigravity.GenerateSessionID()
	if err != nil {
		return nil, fmt.Errorf("生成 session_id 失败: %w", err)
	}

	var proxyURL string
	if proxyID != nil {
		proxy, err := s.proxyRepo.GetByID(ctx, *proxyID)
		if err == nil && proxy != nil {
			proxyURL = proxy.URL()
		}
	}

	session := &antigravity.OAuthSession{
		State:        state,
		CodeVerifier: codeVerifier,
		ProxyURL:     proxyURL,
		CreatedAt:    time.Now(),
	}
	s.sessionStore.Set(sessionID, session)

	codeChallenge := antigravity.GenerateCodeChallenge(codeVerifier)
	authURL := antigravity.BuildAuthorizationURL(state, codeChallenge)

	return &AntigravityAuthURLResult{
		AuthURL:   authURL,
		SessionID: sessionID,
		State:     state,
	}, nil
}

// AntigravityExchangeCodeInput 交换 code 的输入
type AntigravityExchangeCodeInput struct {
	SessionID string
	State     string
	Code      string
	ProxyID   *int64
}

// AntigravityTokenInfo token 信息
type AntigravityTokenInfo struct {
	AccessToken      string `json:"access_token"`
	RefreshToken     string `json:"refresh_token"`
	ExpiresIn        int64  `json:"expires_in"`
	ExpiresAt        int64  `json:"expires_at"`
	TokenType        string `json:"token_type"`
	Email            string `json:"email,omitempty"`
	ProjectID        string `json:"project_id,omitempty"`
	ProjectIDMissing bool   `json:"-"` // LoadCodeAssist 未返回 project_id
}

// ExchangeCode 用 authorization code 交换 token
func (s *AntigravityOAuthService) ExchangeCode(ctx context.Context, input *AntigravityExchangeCodeInput) (*AntigravityTokenInfo, error) {
	session, ok := s.sessionStore.Get(input.SessionID)
	if !ok {
		return nil, fmt.Errorf("session 不存在或已过期")
	}

	if strings.TrimSpace(input.State) == "" || input.State != session.State {
		return nil, fmt.Errorf("state 无效")
	}

	// 确定代理 URL
	proxyURL := session.ProxyURL
	if input.ProxyID != nil {
		proxy, err := s.proxyRepo.GetByID(ctx, *input.ProxyID)
		if err == nil && proxy != nil {
			proxyURL = proxy.URL()
		}
	}

	client := antigravity.NewClient(proxyURL)

	// 交换 token
	tokenResp, err := client.ExchangeCode(ctx, input.Code, session.CodeVerifier)
	if err != nil {
		return nil, fmt.Errorf("token 交换失败: %w", err)
	}

	// 删除 session
	s.sessionStore.Delete(input.SessionID)

	// 计算过期时间（减去 5 分钟安全窗口）
	expiresAt := time.Now().Unix() + tokenResp.ExpiresIn - 300

	result := &AntigravityTokenInfo{
		AccessToken:  tokenResp.AccessToken,
		RefreshToken: tokenResp.RefreshToken,
		ExpiresIn:    tokenResp.ExpiresIn,
		ExpiresAt:    expiresAt,
		TokenType:    tokenResp.TokenType,
	}

	// 获取用户信息
	userInfo, err := client.GetUserInfo(ctx, tokenResp.AccessToken)
	if err != nil {
		fmt.Printf("[AntigravityOAuth] 警告: 获取用户信息失败: %v\n", err)
	} else {
		result.Email = userInfo.Email
	}

	// 获取 project_id（部分账户类型可能没有），失败时重试
	projectID, loadErr := s.loadProjectIDWithRetry(ctx, tokenResp.AccessToken, proxyURL, 3)
	if loadErr != nil {
		fmt.Printf("[AntigravityOAuth] 警告: 获取 project_id 失败（重试后）: %v\n", loadErr)
		result.ProjectIDMissing = true
	} else {
		result.ProjectID = projectID
	}

	return result, nil
}

// RefreshToken 刷新 token
func (s *AntigravityOAuthService) RefreshToken(ctx context.Context, refreshToken, proxyURL string) (*AntigravityTokenInfo, error) {
	var lastErr error

	for attempt := 0; attempt <= 3; attempt++ {
		if attempt > 0 {
			backoff := time.Duration(1<<uint(attempt-1)) * time.Second
			if backoff > 30*time.Second {
				backoff = 30 * time.Second
			}
			time.Sleep(backoff)
		}

		client := antigravity.NewClient(proxyURL)
		tokenResp, err := client.RefreshToken(ctx, refreshToken)
		if err == nil {
			now := time.Now()
			expiresAt := now.Unix() + tokenResp.ExpiresIn - 300
			fmt.Printf("[AntigravityOAuth] Token refreshed: expires_in=%d, expires_at=%d (%s)\n",
				tokenResp.ExpiresIn, expiresAt, time.Unix(expiresAt, 0).Format("2006-01-02 15:04:05"))
			return &AntigravityTokenInfo{
				AccessToken:  tokenResp.AccessToken,
				RefreshToken: tokenResp.RefreshToken,
				ExpiresIn:    tokenResp.ExpiresIn,
				ExpiresAt:    expiresAt,
				TokenType:    tokenResp.TokenType,
			}, nil
		}

		if isNonRetryableAntigravityOAuthError(err) {
			return nil, err
		}
		lastErr = err
	}

	return nil, fmt.Errorf("token 刷新失败 (重试后): %w", lastErr)
}

func isNonRetryableAntigravityOAuthError(err error) bool {
	msg := err.Error()
	nonRetryable := []string{
		"invalid_grant",
		"invalid_client",
		"unauthorized_client",
		"access_denied",
	}
	for _, needle := range nonRetryable {
		if strings.Contains(msg, needle) {
			return true
		}
	}
	return false
}

// RefreshAccountToken 刷新账户的 token
func (s *AntigravityOAuthService) RefreshAccountToken(ctx context.Context, account *Account) (*AntigravityTokenInfo, error) {
	if account.Platform != PlatformAntigravity || account.Type != AccountTypeOAuth {
		return nil, fmt.Errorf("非 Antigravity OAuth 账户")
	}

	refreshToken := account.GetCredential("refresh_token")
	if strings.TrimSpace(refreshToken) == "" {
		return nil, fmt.Errorf("无可用的 refresh_token")
	}

	var proxyURL string
	if account.ProxyID != nil {
		proxy, err := s.proxyRepo.GetByID(ctx, *account.ProxyID)
		if err == nil && proxy != nil {
			proxyURL = proxy.URL()
		}
	}

	tokenInfo, err := s.RefreshToken(ctx, refreshToken, proxyURL)
	if err != nil {
		return nil, err
	}

	// 保留原有的 email
	existingEmail := strings.TrimSpace(account.GetCredential("email"))
	if existingEmail != "" {
		tokenInfo.Email = existingEmail
	}

	// 每次刷新都调用 LoadCodeAssist 获取 project_id，失败时重试
	existingProjectID := strings.TrimSpace(account.GetCredential("project_id"))
	projectID, loadErr := s.loadProjectIDWithRetry(ctx, tokenInfo.AccessToken, proxyURL, 3)

	if loadErr != nil {
		// LoadCodeAssist 失败，保留原有 project_id
		tokenInfo.ProjectID = existingProjectID
		// 只有从未获取过 project_id 且本次也获取失败时，才标记为真正缺失
		// 如果之前有 project_id，本次只是临时故障，不应标记为错误
		if existingProjectID == "" {
			tokenInfo.ProjectIDMissing = true
		}
	} else {
		tokenInfo.ProjectID = projectID
	}

	return tokenInfo, nil
}

// loadProjectIDWithRetry 带重试机制获取 project_id
// 返回 project_id 和错误，失败时会重试指定次数
func (s *AntigravityOAuthService) loadProjectIDWithRetry(ctx context.Context, accessToken, proxyURL string, maxRetries int) (string, error) {
	var lastErr error

	for attempt := 0; attempt <= maxRetries; attempt++ {
		if attempt > 0 {
			// 指数退避：1s, 2s, 4s
			backoff := time.Duration(1<<uint(attempt-1)) * time.Second
			if backoff > 8*time.Second {
				backoff = 8 * time.Second
			}
			time.Sleep(backoff)
		}

		client := antigravity.NewClient(proxyURL)
		loadResp, _, err := client.LoadCodeAssist(ctx, accessToken)

		if err == nil && loadResp != nil && loadResp.CloudAICompanionProject != "" {
			return loadResp.CloudAICompanionProject, nil
		}

		// 记录错误
		if err != nil {
			lastErr = err
		} else if loadResp == nil {
			lastErr = fmt.Errorf("LoadCodeAssist 返回空响应")
		} else {
			lastErr = fmt.Errorf("LoadCodeAssist 返回空 project_id")
		}
	}

	return "", fmt.Errorf("获取 project_id 失败 (重试 %d 次后): %w", maxRetries, lastErr)
}

// BuildAccountCredentials 构建账户凭证
func (s *AntigravityOAuthService) BuildAccountCredentials(tokenInfo *AntigravityTokenInfo) map[string]any {
	creds := map[string]any{
		"access_token": tokenInfo.AccessToken,
		"expires_at":   strconv.FormatInt(tokenInfo.ExpiresAt, 10),
	}
	if tokenInfo.RefreshToken != "" {
		creds["refresh_token"] = tokenInfo.RefreshToken
	}
	if tokenInfo.TokenType != "" {
		creds["token_type"] = tokenInfo.TokenType
	}
	if tokenInfo.Email != "" {
		creds["email"] = tokenInfo.Email
	}
	if tokenInfo.ProjectID != "" {
		creds["project_id"] = tokenInfo.ProjectID
	}
	return creds
}

// Stop 停止服务
func (s *AntigravityOAuthService) Stop() {
	s.sessionStore.Stop()
}