package handlers

import (
	"errors"
	"net/http"
	"time"

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

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

// UpgradeCreatorResponse is returned by POST /users/me/upgrade-creator.
type UpgradeCreatorResponse struct {
	Role                string     `json:"role"`
	PromotedToCreatorAt *time.Time `json:"promoted_to_creator_at,omitempty"`
	AlreadyElevated     bool       `json:"already_elevated"`
}

// creatorOrHigher lists roles that already have creator-tier privileges.
// Self-promotion is a no-op for these (idempotent 200).
func creatorOrHigher(role string) bool {
	switch role {
	case "creator", "premium", "moderator", "admin", "artist", "producer", "label":
		return true
	}
	return false
}

// UpgradeToCreator returns the handler for POST /users/me/upgrade-creator.
// Self-service path: a verified `role='user'` account flips to `role='creator'`
// on one conscious click. One-way — downgrade requires a support ticket.
//
// Guards:
//   - 401 if no authenticated user (middleware should catch this first, belt+braces)
//   - 403 EMAIL_NOT_VERIFIED if `is_verified=false`
//   - 200 idempotent if the caller is already creator-tier or above
//   - 200 with the new role + promoted_to_creator_at if the flip happened
func UpgradeToCreator(db *gorm.DB, auditService *services.AuditService, logger *zap.Logger) gin.HandlerFunc {
	return func(c *gin.Context) {
		userIDRaw, ok := c.Get("user_id")
		if !ok {
			c.JSON(http.StatusUnauthorized, gin.H{
				"error": gin.H{"code": "UNAUTHORIZED", "message": "User ID not found in context"},
			})
			return
		}
		userID, ok := userIDRaw.(uuid.UUID)
		if !ok {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": gin.H{"code": "INVALID_USER_ID", "message": "Invalid user ID"},
			})
			return
		}

		ctx := c.Request.Context()

		var user models.User
		if err := db.WithContext(ctx).First(&user, "id = ?", userID).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				c.JSON(http.StatusNotFound, gin.H{
					"error": gin.H{"code": "USER_NOT_FOUND", "message": "User not found"},
				})
				return
			}
			logger.Error("Failed to load user for creator upgrade",
				zap.String("user_id", userID.String()),
				zap.Error(err),
			)
			c.JSON(http.StatusInternalServerError, gin.H{
				"error": gin.H{"code": "INTERNAL_ERROR", "message": "Failed to load user"},
			})
			return
		}

		if !user.IsVerified {
			c.JSON(http.StatusForbidden, gin.H{
				"error": gin.H{
					"code":    "EMAIL_NOT_VERIFIED",
					"message": "Verify your email before upgrading to a creator account",
				},
			})
			return
		}

		if creatorOrHigher(user.Role) {
			// Already creator-tier. Keep the existing role and promoted_to_creator_at
			// (may be nil for admin-assigned roles — that's fine, the timestamp only
			// records self-promotions).
			c.JSON(http.StatusOK, UpgradeCreatorResponse{
				Role:                user.Role,
				PromotedToCreatorAt: user.PromotedToCreatorAt,
				AlreadyElevated:     true,
			})
			return
		}

		now := time.Now().UTC()
		updates := map[string]interface{}{
			"role":                   "creator",
			"promoted_to_creator_at": now,
			"updated_at":             now,
		}
		// Only flip if role is still 'user' — avoids racing with an admin who
		// may have assigned a different role between the load and the write.
		res := db.WithContext(ctx).
			Model(&models.User{}).
			Where("id = ? AND role = ?", userID, "user").
			Updates(updates)
		if res.Error != nil {
			logger.Error("Failed to upgrade user to creator",
				zap.String("user_id", userID.String()),
				zap.Error(res.Error),
			)
			c.JSON(http.StatusInternalServerError, gin.H{
				"error": gin.H{"code": "INTERNAL_ERROR", "message": "Failed to upgrade user"},
			})
			return
		}
		if res.RowsAffected == 0 {
			// Race: role changed between load and write. Re-load and treat as
			// "already elevated" (the race landed on a higher role, which is fine).
			if reloadErr := db.WithContext(ctx).First(&user, "id = ?", userID).Error; reloadErr == nil {
				c.JSON(http.StatusOK, UpgradeCreatorResponse{
					Role:                user.Role,
					PromotedToCreatorAt: user.PromotedToCreatorAt,
					AlreadyElevated:     true,
				})
				return
			}
			logger.Warn("Creator upgrade UPDATE matched zero rows and reload failed",
				zap.String("user_id", userID.String()),
			)
			c.JSON(http.StatusConflict, gin.H{
				"error": gin.H{"code": "UPGRADE_CONFLICT", "message": "Role changed concurrently, please retry"},
			})
			return
		}

		// Log to audit trail (non-fatal on failure — upgrade already succeeded).
		if auditService != nil {
			if auditErr := auditService.LogAction(ctx, &services.AuditLogCreateRequest{
				UserID:    &userID,
				Action:    "user.upgrade_creator",
				Resource:  "user",
				IPAddress: c.ClientIP(),
				UserAgent: c.GetHeader("User-Agent"),
				Metadata: map[string]interface{}{
					"from_role":              "user",
					"to_role":                "creator",
					"promoted_to_creator_at": now.Format(time.RFC3339),
				},
			}); auditErr != nil {
				logger.Warn("Failed to log creator upgrade in audit trail",
					zap.String("user_id", userID.String()),
					zap.Error(auditErr),
				)
			}
		}

		logger.Info("User upgraded to creator",
			zap.String("user_id", userID.String()),
			zap.Time("promoted_at", now),
		)

		c.JSON(http.StatusOK, UpgradeCreatorResponse{
			Role:                "creator",
			PromotedToCreatorAt: &now,
			AlreadyElevated:     false,
		})
	}
}