package services

import (
	"context"
	"encoding/json"
	"time"

	"github.com/breakpilot/billing-service/internal/database"
	"github.com/breakpilot/billing-service/internal/models"
	"github.com/google/uuid"
)

// EntitlementService handles entitlement-related operations
type EntitlementService struct {
	db         *database.DB
	subService *SubscriptionService
}

// NewEntitlementService creates a new EntitlementService
func NewEntitlementService(db *database.DB, subService *SubscriptionService) *EntitlementService {
	return &EntitlementService{
		db:         db,
		subService: subService,
	}
}

// GetEntitlements returns the entitlement info for a user
func (s *EntitlementService) GetEntitlements(ctx context.Context, userID uuid.UUID) (*models.EntitlementInfo, error) {
	entitlements, err := s.getUserEntitlements(ctx, userID)
	if err != nil || entitlements == nil {
		return nil, err
	}

	return &models.EntitlementInfo{
		Features:        entitlements.Features.FeatureFlags,
		MaxTeamMembers:  entitlements.Features.MaxTeamMembers,
		PrioritySupport: entitlements.Features.PrioritySupport,
		CustomBranding:  entitlements.Features.CustomBranding,
	}, nil
}

// GetEntitlementsByUserIDString returns entitlements by user ID string (for internal API)
func (s *EntitlementService) GetEntitlementsByUserIDString(ctx context.Context, userIDStr string) (*models.UserEntitlements, error) {
	userID, err := uuid.Parse(userIDStr)
	if err != nil {
		return nil, err
	}

	return s.getUserEntitlements(ctx, userID)
}

// getUserEntitlements retrieves or creates entitlements for a user
func (s *EntitlementService) getUserEntitlements(ctx context.Context, userID uuid.UUID) (*models.UserEntitlements, error) {
	query := `
		SELECT id, user_id, plan_id, ai_requests_limit, ai_requests_used,
		       documents_limit, documents_used, features, period_start, period_end,
		       created_at, updated_at
		FROM user_entitlements
		WHERE user_id = $1
	`

	var ent models.UserEntitlements
	var featuresJSON []byte
	var periodStart, periodEnd *time.Time

	err := s.db.Pool.QueryRow(ctx, query, userID).Scan(
		&ent.ID, &ent.UserID, &ent.PlanID, &ent.AIRequestsLimit, &ent.AIRequestsUsed,
		&ent.DocumentsLimit, &ent.DocumentsUsed, &featuresJSON, &periodStart, &periodEnd,
		nil, &ent.UpdatedAt,
	)

	if err != nil {
		if err.Error() == "no rows in result set" {
			// Try to create entitlements based on subscription
			return s.createEntitlementsFromSubscription(ctx, userID)
		}
		return nil, err
	}

	if len(featuresJSON) > 0 {
		json.Unmarshal(featuresJSON, &ent.Features)
	}

	return &ent, nil
}

// createEntitlementsFromSubscription creates entitlements based on user's subscription
func (s *EntitlementService) createEntitlementsFromSubscription(ctx context.Context, userID uuid.UUID) (*models.UserEntitlements, error) {
	// Get user's subscription
	sub, err := s.subService.GetByUserID(ctx, userID)
	if err != nil || sub == nil {
		return nil, err
	}

	// Get plan details
	plan, err := s.subService.GetPlanByID(ctx, string(sub.PlanID))
	if err != nil || plan == nil {
		return nil, err
	}

	// Create entitlements
	return s.CreateEntitlements(ctx, userID, sub.PlanID, plan.Features, sub.CurrentPeriodEnd)
}

// CreateEntitlements creates entitlements for a user
func (s *EntitlementService) CreateEntitlements(ctx context.Context, userID uuid.UUID, planID models.PlanID, features models.PlanFeatures, periodEnd *time.Time) (*models.UserEntitlements, error) {
	featuresJSON, _ := json.Marshal(features)

	now := time.Now()
	periodStart := now

	query := `
		INSERT INTO user_entitlements (
			user_id, plan_id, ai_requests_limit, ai_requests_used,
			documents_limit, documents_used, features, period_start, period_end
		) VALUES ($1, $2, $3, 0, $4, 0, $5, $6, $7)
		ON CONFLICT (user_id) DO UPDATE SET
			plan_id = EXCLUDED.plan_id,
			ai_requests_limit = EXCLUDED.ai_requests_limit,
			documents_limit = EXCLUDED.documents_limit,
			features = EXCLUDED.features,
			period_start = EXCLUDED.period_start,
			period_end = EXCLUDED.period_end,
			updated_at = NOW()
		RETURNING id, user_id, plan_id, ai_requests_limit, ai_requests_used,
		          documents_limit, documents_used, updated_at
	`

	var ent models.UserEntitlements
	err := s.db.Pool.QueryRow(ctx, query,
		userID, planID, features.AIRequestsLimit, features.DocumentsLimit,
		featuresJSON, periodStart, periodEnd,
	).Scan(
		&ent.ID, &ent.UserID, &ent.PlanID, &ent.AIRequestsLimit, &ent.AIRequestsUsed,
		&ent.DocumentsLimit, &ent.DocumentsUsed, &ent.UpdatedAt,
	)

	if err != nil {
		return nil, err
	}

	ent.Features = features
	return &ent, nil
}

// UpdateEntitlements updates entitlements for a user (e.g., on plan change)
func (s *EntitlementService) UpdateEntitlements(ctx context.Context, userID uuid.UUID, planID models.PlanID, features models.PlanFeatures) error {
	featuresJSON, _ := json.Marshal(features)

	query := `
		UPDATE user_entitlements SET
			plan_id = $2,
			ai_requests_limit = $3,
			documents_limit = $4,
			features = $5,
			updated_at = NOW()
		WHERE user_id = $1
	`

	_, err := s.db.Pool.Exec(ctx, query,
		userID, planID, features.AIRequestsLimit, features.DocumentsLimit, featuresJSON,
	)
	return err
}

// ResetUsageCounters resets usage counters for a new period
func (s *EntitlementService) ResetUsageCounters(ctx context.Context, userID uuid.UUID, newPeriodStart, newPeriodEnd *time.Time) error {
	query := `
		UPDATE user_entitlements SET
			ai_requests_used = 0,
			documents_used = 0,
			period_start = $2,
			period_end = $3,
			updated_at = NOW()
		WHERE user_id = $1
	`

	_, err := s.db.Pool.Exec(ctx, query, userID, newPeriodStart, newPeriodEnd)
	return err
}

// CheckEntitlement checks if a user has a specific feature entitlement
func (s *EntitlementService) CheckEntitlement(ctx context.Context, userIDStr, feature string) (bool, models.PlanID, error) {
	userID, err := uuid.Parse(userIDStr)
	if err != nil {
		return false, "", err
	}

	ent, err := s.getUserEntitlements(ctx, userID)
	if err != nil || ent == nil {
		return false, "", err
	}

	// Check if feature is in the feature flags
	for _, f := range ent.Features.FeatureFlags {
		if f == feature {
			return true, ent.PlanID, nil
		}
	}

	return false, ent.PlanID, nil
}

// IncrementUsage increments a usage counter
func (s *EntitlementService) IncrementUsage(ctx context.Context, userID uuid.UUID, usageType string, amount int) error {
	var column string
	switch usageType {
	case "ai_request":
		column = "ai_requests_used"
	case "document_created":
		column = "documents_used"
	default:
		return nil
	}

	query := `
		UPDATE user_entitlements SET
			` + column + ` = ` + column + ` + $2,
			updated_at = NOW()
		WHERE user_id = $1
	`

	_, err := s.db.Pool.Exec(ctx, query, userID, amount)
	return err
}

// DeleteEntitlements removes entitlements for a user (on subscription cancellation)
func (s *EntitlementService) DeleteEntitlements(ctx context.Context, userID uuid.UUID) error {
	query := `DELETE FROM user_entitlements WHERE user_id = $1`
	_, err := s.db.Pool.Exec(ctx, query, userID)
	return err
}