package handlers

import (
	"context"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"go.uber.org/zap"
	"gorm.io/gorm"

	"veza-backend-api/internal/services"
	"veza-backend-api/internal/utils"
)

// DeleteAccountRequest is the request body for account deletion (v0.10.8 F065)
type DeleteAccountRequest struct {
	Password         string `json:"password" binding:"required"`
	Reason           string `json:"reason"`
	ConfirmText      string `json:"confirm_text" binding:"required"`
	KeepPublicTracks bool   `json:"keep_public_tracks"` // If true, public tracks remain (attributed to deleted account)
}

// DeleteAccountHandler returns a handler for DELETE /users/me (v0.803 SEC2-05)
//
// @Summary      Delete account
// @Description  Permanently delete user account with anonymization, session revocation, audit log
// @Tags         Users
// @Security     BearerAuth
// @Param        body  body  DeleteAccountRequest  true  "Password, reason, confirm_text (must be DELETE)"
// @Success      200   {object}  map[string]interface{}
// @Failure      400   {object}  map[string]interface{}
// @Failure      401   {object}  map[string]interface{}
// @Failure      500   {object}  map[string]interface{}
// @Router       /users/me [delete]
func DeleteAccountHandler(
	db *gorm.DB,
	sessionService *services.SessionService,
	auditService *services.AuditService,
	s3Service *services.S3StorageService,
	logger *zap.Logger,
) gin.HandlerFunc {
	refreshTokenService := services.NewRefreshTokenService(db)

	return func(c *gin.Context) {
		userID, ok := GetUserIDUUID(c)
		if !ok || userID == uuid.Nil {
			c.JSON(http.StatusUnauthorized, gin.H{"error": "Authentication required"})
			return
		}

		var req DeleteAccountRequest
		if err := c.ShouldBindJSON(&req); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid request: password and confirm_text required"})
			return
		}

		if req.ConfirmText != "DELETE" {
			c.JSON(http.StatusBadRequest, gin.H{"error": "Type DELETE to confirm"})
			return
		}

		// 1. Verify password
		var passwordHash string
		if err := db.WithContext(c.Request.Context()).Raw("SELECT password_hash FROM users WHERE id = ?", userID).Scan(&passwordHash).Error; err != nil || passwordHash == "" {
			c.JSON(http.StatusUnauthorized, gin.H{"error": "Invalid password"})
			return
		}
		if err := utils.CheckPasswordHash(req.Password, passwordHash); err != nil {
			c.JSON(http.StatusUnauthorized, gin.H{"error": "Invalid password"})
			return
		}

		ctx := c.Request.Context()
		recoveryDeadline := time.Now().Add(30 * 24 * time.Hour)
		anonUsername := "deleted-" + userID.String()
		anonEmail := "deleted-" + userID.String() + "@veza.app"

		// 2. Soft delete + full PII anonymization (v0.10.8 droit à l'oubli)
		result := db.WithContext(ctx).Exec(`
			UPDATE users SET
				is_active = false,
				deleted_at = NOW(),
				deletion_reason = ?,
				recovery_deadline = ?,
				username = ?,
				email = ?,
				first_name = NULL,
				last_name = NULL,
				bio = '',
				location = '',
				avatar = '',
				banner_url = '',
				updated_at = NOW()
			WHERE id = ?
		`, req.Reason, recoveryDeadline, anonUsername, anonEmail, userID)
		if result.Error != nil {
			logger.Error("Failed to delete account", zap.Error(result.Error), zap.String("user_id", userID.String()))
			c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to delete account"})
			return
		}

		// 2b. Anonymize user_profiles if exists (v0.10.8)
		_ = db.WithContext(ctx).Exec("UPDATE user_profiles SET bio = NULL, tagline = NULL, location = NULL, website_url = NULL, avatar_url = NULL, banner_url = NULL, updated_at = NOW() WHERE user_id = ?", userID)

		// 2c. Tracks: if !KeepPublicTracks, soft-delete all user tracks (v0.10.8)
		if !req.KeepPublicTracks {
			_ = db.WithContext(ctx).Exec("UPDATE tracks SET deleted_at = NOW() WHERE creator_id = ?", userID)
		}

		// 2d. SECURITY(REM-013): Anonymize financial data for GDPR compliance.
		// Orders are anonymized (not deleted) for legal/accounting obligations.
		_ = db.WithContext(ctx).Exec("UPDATE orders SET buyer_id = ? WHERE buyer_id = ?", uuid.Nil, userID)
		// Revoke active licenses
		_ = db.WithContext(ctx).Exec("UPDATE licenses SET revoked_at = NOW() WHERE buyer_id = ? AND revoked_at IS NULL", userID)
		// Zero out seller balances (prevent orphaned payouts)
		_ = db.WithContext(ctx).Exec("UPDATE seller_balances SET available_cents = 0, pending_cents = 0 WHERE seller_id = ?", userID)
		// Cancel pending payouts
		_ = db.WithContext(ctx).Exec("UPDATE seller_payouts SET status = 'cancelled' WHERE seller_id = ? AND status IN ('pending', 'processing')", userID)
		// Cancel active subscriptions
		_ = db.WithContext(ctx).Exec("UPDATE user_subscriptions SET status = 'cancelled', cancelled_at = NOW() WHERE user_id = ? AND status IN ('active', 'trialing')", userID)

		// 3. Revoke all sessions
		if sessionService != nil {
			if _, err := sessionService.RevokeAllUserSessions(ctx, userID); err != nil {
				logger.Warn("Failed to revoke sessions during account deletion", zap.Error(err), zap.String("user_id", userID.String()))
			}
		}

		// 4. Revoke all refresh tokens
		if err := refreshTokenService.RevokeAll(userID); err != nil {
			logger.Warn("Failed to revoke refresh tokens during account deletion", zap.Error(err), zap.String("user_id", userID.String()))
		}

		// 5. S3 cleanup (cloud files for user)
		if s3Service != nil {
			deleteUserS3Files(ctx, db, s3Service, userID, logger)
		}

		// 6. Audit log
		if auditService != nil {
			_ = auditService.LogDeletion(ctx, userID, "user", userID, c.ClientIP(), c.Request.UserAgent())
		}

		RespondSuccess(c, http.StatusOK, gin.H{"message": "Account deleted"})
	}
}

// deleteUserS3Files deletes cloud files for a user from S3
func deleteUserS3Files(ctx context.Context, db *gorm.DB, s3Service *services.S3StorageService, userID uuid.UUID, logger *zap.Logger) {
	var files []struct {
		S3Key string
	}
	if err := db.WithContext(ctx).Raw("SELECT s3_key FROM user_files WHERE user_id = ?", userID).Scan(&files).Error; err != nil {
		logger.Warn("Failed to list user files for S3 cleanup", zap.Error(err), zap.String("user_id", userID.String()))
		return
	}
	for _, f := range files {
		if err := s3Service.DeleteFile(ctx, f.S3Key); err != nil {
			logger.Warn("Failed to delete S3 file during account deletion", zap.Error(err), zap.String("key", f.S3Key))
		}
	}
}