package distribution

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

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

	"veza-backend-api/internal/core/subscription"
)

// Service errors
var (
	ErrDistributionNotFound     = errors.New("distribution not found")
	ErrTrackNotFound            = errors.New("track not found")
	ErrNotEligible              = errors.New("distribution requires Creator or Premium plan")
	ErrTrackNotPublic           = errors.New("track must be public to distribute")
	ErrAlreadyDistributed       = errors.New("track already has a pending or live distribution")
	ErrInvalidPlatform          = errors.New("unsupported platform")
	ErrNoPlatformsSelected      = errors.New("at least one platform must be selected")
	ErrDistributionNotRemovable = errors.New("distribution cannot be removed in current status")
)

// DistributorProvider defines the interface for external distribution APIs
type DistributorProvider interface {
	SubmitTrack(ctx context.Context, req DistributorSubmitRequest) (*DistributorSubmitResponse, error)
	GetStatus(ctx context.Context, submissionID string) (*DistributorStatusResponse, error)
}

// DistributorSubmitRequest is the payload sent to the distributor API
type DistributorSubmitRequest struct {
	TrackFilePath string               `json:"track_file_path"`
	CoverFilePath string               `json:"cover_file_path"`
	Metadata      DistributionMetadata `json:"metadata"`
	Platforms     []Platform           `json:"platforms"`
}

// DistributorSubmitResponse is the response from the distributor API
type DistributorSubmitResponse struct {
	SubmissionID      string `json:"submission_id"`
	UPC               string `json:"upc,omitempty"`
	ISRC              string `json:"isrc,omitempty"`
	EstimatedLiveDays int    `json:"estimated_live_days"`
}

// DistributorStatusResponse is the status response from the distributor API
type DistributorStatusResponse struct {
	SubmissionID     string                      `json:"submission_id"`
	OverallStatus    DistributionStatus          `json:"overall_status"`
	PlatformStatuses map[Platform]PlatformStatus `json:"platform_statuses"`
}

// ServiceOption is a functional option for configuring the Service
type ServiceOption func(*Service)

// WithDistributorProvider sets the distributor API provider
func WithDistributorProvider(p DistributorProvider) ServiceOption {
	return func(s *Service) {
		s.distributorProvider = p
	}
}

// Service handles distribution business logic
type Service struct {
	db                  *gorm.DB
	logger              *zap.Logger
	subscriptionService *subscription.Service
	distributorProvider DistributorProvider
}

// NewService creates a new distribution service
func NewService(db *gorm.DB, logger *zap.Logger, subSvc *subscription.Service, opts ...ServiceOption) *Service {
	s := &Service{
		db:                  db,
		logger:              logger,
		subscriptionService: subSvc,
	}
	for _, opt := range opts {
		opt(s)
	}
	return s
}

// SubmitRequest holds the parameters for submitting a track for distribution
type SubmitRequest struct {
	TrackID   uuid.UUID            `json:"track_id" binding:"required"`
	Platforms []Platform           `json:"platforms" binding:"required"`
	Metadata  DistributionMetadata `json:"metadata" binding:"required"`
}

// SubmitResponse holds the result of a distribution submission
type SubmitResponse struct {
	Distribution      *TrackDistribution `json:"distribution"`
	EstimatedLiveDays int                `json:"estimated_live_days"`
}

// Submit submits a track for distribution to selected platforms
func (s *Service) Submit(ctx context.Context, creatorID uuid.UUID, req SubmitRequest) (*SubmitResponse, error) {
	// Validate platforms
	if len(req.Platforms) == 0 {
		return nil, ErrNoPlatformsSelected
	}
	validPlatforms := make(map[Platform]bool)
	for _, p := range AllPlatforms() {
		validPlatforms[p] = true
	}
	for _, p := range req.Platforms {
		if !validPlatforms[p] {
			return nil, fmt.Errorf("%w: %s", ErrInvalidPlatform, p)
		}
	}

	// Check subscription eligibility
	eligible, err := s.checkEligibility(ctx, creatorID)
	if err != nil {
		return nil, err
	}
	if !eligible {
		return nil, ErrNotEligible
	}

	// Verify track exists and belongs to creator
	var trackExists bool
	err = s.db.WithContext(ctx).
		Raw("SELECT EXISTS(SELECT 1 FROM tracks WHERE id = ? AND creator_id = ? AND is_public = true AND deleted_at IS NULL)", req.TrackID, creatorID).
		Scan(&trackExists).Error
	if err != nil {
		return nil, fmt.Errorf("failed to verify track: %w", err)
	}
	if !trackExists {
		return nil, ErrTrackNotPublic
	}

	// Check for existing active distribution
	var existingCount int64
	s.db.WithContext(ctx).Model(&TrackDistribution{}).
		Where("track_id = ? AND overall_status IN ?", req.TrackID,
			[]string{string(StatusSubmitted), string(StatusProcessing), string(StatusLive)}).
		Count(&existingCount)
	if existingCount > 0 {
		return nil, ErrAlreadyDistributed
	}

	// Build platform statuses
	platformStatuses := make(map[Platform]PlatformStatus)
	for _, p := range req.Platforms {
		platformStatuses[p] = PlatformStatus{Status: string(StatusSubmitted)}
	}

	metadataJSON, err := json.Marshal(req.Metadata)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal metadata: %w", err)
	}
	platformJSON, err := json.Marshal(platformStatuses)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal platform statuses: %w", err)
	}

	// Generate a submission ID (in production, this comes from distributor API)
	submissionID := fmt.Sprintf("veza-%s-%d", req.TrackID.String()[:8], time.Now().Unix())
	estimatedDays := 7

	// If distributor provider is configured, call it
	if s.distributorProvider != nil {
		resp, err := s.distributorProvider.SubmitTrack(ctx, DistributorSubmitRequest{
			Metadata:  req.Metadata,
			Platforms: req.Platforms,
		})
		if err != nil {
			return nil, fmt.Errorf("distributor submission failed: %w", err)
		}
		submissionID = resp.SubmissionID
		estimatedDays = resp.EstimatedLiveDays
		if resp.UPC != "" {
			req.Metadata.UPC = resp.UPC
		}
		if resp.ISRC != "" {
			req.Metadata.ISRC = resp.ISRC
		}
		metadataJSON, _ = json.Marshal(req.Metadata)
	}

	now := time.Now()
	dist := &TrackDistribution{
		TrackID:          req.TrackID,
		CreatorID:        creatorID,
		Distributor:      "distrokid",
		SubmissionID:     submissionID,
		SubmissionUPC:    req.Metadata.UPC,
		SubmissionISRC:   req.Metadata.ISRC,
		Metadata:         metadataJSON,
		OverallStatus:    StatusSubmitted,
		PlatformStatuses: platformJSON,
		SubmittedAt:      now,
	}

	err = s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		if err := tx.Create(dist).Error; err != nil {
			return fmt.Errorf("failed to create distribution: %w", err)
		}

		// Create initial status history entries
		for _, p := range req.Platforms {
			entry := &StatusHistoryEntry{
				DistributionID: dist.ID,
				Platform:       string(p),
				NewStatus:      string(StatusSubmitted),
				Note:           "Track submitted for distribution",
			}
			if err := tx.Create(entry).Error; err != nil {
				return fmt.Errorf("failed to create status history: %w", err)
			}
		}
		return nil
	})
	if err != nil {
		return nil, err
	}

	s.logger.Info("Track submitted for distribution",
		zap.String("creator_id", creatorID.String()),
		zap.String("track_id", req.TrackID.String()),
		zap.String("submission_id", submissionID),
		zap.Int("platforms", len(req.Platforms)),
	)

	return &SubmitResponse{
		Distribution:      dist,
		EstimatedLiveDays: estimatedDays,
	}, nil
}

// checkEligibility verifies that the user has a Creator or Premium subscription with distribution access
func (s *Service) checkEligibility(ctx context.Context, userID uuid.UUID) (bool, error) {
	if s.subscriptionService == nil {
		// No subscription service configured, allow by default (dev mode)
		return true, nil
	}

	sub, err := s.subscriptionService.GetUserSubscription(ctx, userID)
	if err != nil {
		if errors.Is(err, subscription.ErrNoActiveSubscription) {
			return false, nil
		}
		return false, err
	}

	return sub.Plan.HasDistribution || sub.Plan.CanSellOnMarketplace, nil
}

// GetDistribution returns a distribution by ID
func (s *Service) GetDistribution(ctx context.Context, distID uuid.UUID) (*TrackDistribution, error) {
	var dist TrackDistribution
	err := s.db.WithContext(ctx).First(&dist, "id = ?", distID).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrDistributionNotFound
		}
		return nil, fmt.Errorf("failed to get distribution: %w", err)
	}
	return &dist, nil
}

// ListDistributions returns distributions for a creator with optional filters
func (s *Service) ListDistributions(ctx context.Context, creatorID uuid.UUID, trackID *uuid.UUID, status *DistributionStatus, limit, offset int) ([]TrackDistribution, int64, error) {
	if limit <= 0 || limit > 100 {
		limit = 20
	}
	if offset < 0 {
		offset = 0
	}

	query := s.db.WithContext(ctx).Where("creator_id = ?", creatorID)
	if trackID != nil {
		query = query.Where("track_id = ?", *trackID)
	}
	if status != nil {
		query = query.Where("overall_status = ?", string(*status))
	}

	var total int64
	query.Model(&TrackDistribution{}).Count(&total)

	var dists []TrackDistribution
	err := query.Order("submitted_at DESC").Limit(limit).Offset(offset).Find(&dists).Error
	if err != nil {
		return nil, 0, fmt.Errorf("failed to list distributions: %w", err)
	}
	return dists, total, nil
}

// GetTrackDistributions returns all distributions for a specific track
func (s *Service) GetTrackDistributions(ctx context.Context, trackID uuid.UUID) ([]TrackDistribution, error) {
	var dists []TrackDistribution
	err := s.db.WithContext(ctx).
		Where("track_id = ?", trackID).
		Order("submitted_at DESC").
		Find(&dists).Error
	if err != nil {
		return nil, fmt.Errorf("failed to get track distributions: %w", err)
	}
	return dists, nil
}

// GetStatusHistory returns the status change history for a distribution
func (s *Service) GetStatusHistory(ctx context.Context, distID uuid.UUID) ([]StatusHistoryEntry, error) {
	var entries []StatusHistoryEntry
	err := s.db.WithContext(ctx).
		Where("distribution_id = ?", distID).
		Order("created_at ASC").
		Find(&entries).Error
	if err != nil {
		return nil, fmt.Errorf("failed to get status history: %w", err)
	}
	return entries, nil
}

// RemoveDistribution marks a live distribution for removal
func (s *Service) RemoveDistribution(ctx context.Context, creatorID, distID uuid.UUID) error {
	dist, err := s.GetDistribution(ctx, distID)
	if err != nil {
		return err
	}
	if dist.CreatorID != creatorID {
		return ErrDistributionNotFound
	}
	if dist.OverallStatus != StatusLive {
		return ErrDistributionNotRemovable
	}

	now := time.Now()
	dist.OverallStatus = StatusRemoved
	dist.UpdatedAt = now

	return s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		if err := tx.Save(dist).Error; err != nil {
			return err
		}
		entry := &StatusHistoryEntry{
			DistributionID: dist.ID,
			Platform:       "all",
			OldStatus:      string(StatusLive),
			NewStatus:      string(StatusRemoved),
			Note:           "Removed by creator",
		}
		return tx.Create(entry).Error
	})
}

// PollDistributionStatuses polls the distributor API for status updates (background job)
func (s *Service) PollDistributionStatuses(ctx context.Context) (int, error) {
	if s.distributorProvider == nil {
		return 0, nil
	}

	var dists []TrackDistribution
	err := s.db.WithContext(ctx).
		Where("overall_status IN ?", []string{string(StatusSubmitted), string(StatusProcessing)}).
		Find(&dists).Error
	if err != nil {
		return 0, fmt.Errorf("failed to query distributions for polling: %w", err)
	}

	updated := 0
	now := time.Now()
	for i := range dists {
		dist := &dists[i]
		resp, err := s.distributorProvider.GetStatus(ctx, dist.SubmissionID)
		if err != nil {
			s.logger.Warn("Failed to poll distribution status",
				zap.String("submission_id", dist.SubmissionID),
				zap.Error(err),
			)
			continue
		}

		if resp.OverallStatus != dist.OverallStatus {
			oldStatus := dist.OverallStatus
			dist.OverallStatus = resp.OverallStatus
			dist.LastStatusCheckAt = &now

			if resp.OverallStatus == StatusLive && dist.FirstLiveAt == nil {
				dist.FirstLiveAt = &now
			}

			platformJSON, _ := json.Marshal(resp.PlatformStatuses)
			dist.PlatformStatuses = platformJSON

			if err := s.db.WithContext(ctx).Save(dist).Error; err != nil {
				s.logger.Error("Failed to update distribution status",
					zap.String("distribution_id", dist.ID.String()),
					zap.Error(err),
				)
				continue
			}

			// Record status history
			entry := &StatusHistoryEntry{
				DistributionID: dist.ID,
				Platform:       "all",
				OldStatus:      string(oldStatus),
				NewStatus:      string(resp.OverallStatus),
				Note:           "Status updated via distributor API poll",
			}
			s.db.WithContext(ctx).Create(entry)

			updated++
			s.logger.Info("Distribution status updated",
				zap.String("distribution_id", dist.ID.String()),
				zap.String("old_status", string(oldStatus)),
				zap.String("new_status", string(resp.OverallStatus)),
			)
		} else {
			dist.LastStatusCheckAt = &now
			s.db.WithContext(ctx).Model(dist).Update("last_status_check_at", now)
		}
	}

	return updated, nil
}

// GetExternalRoyalties returns external streaming royalties for a creator
func (s *Service) GetExternalRoyalties(ctx context.Context, creatorID uuid.UUID, startDate, endDate *time.Time, platform *string, limit, offset int) ([]ExternalStreamingRoyalty, *RoyaltySummary, error) {
	if limit <= 0 || limit > 100 {
		limit = 20
	}
	if offset < 0 {
		offset = 0
	}

	query := s.db.WithContext(ctx).Where("creator_id = ? AND import_status = ?", creatorID, string(ImportCompleted))
	if startDate != nil {
		query = query.Where("reporting_period_start >= ?", *startDate)
	}
	if endDate != nil {
		query = query.Where("reporting_period_end <= ?", *endDate)
	}
	if platform != nil && *platform != "" {
		query = query.Where("platform = ?", *platform)
	}

	var royalties []ExternalStreamingRoyalty
	err := query.Order("reporting_period_start DESC").
		Limit(limit).Offset(offset).
		Find(&royalties).Error
	if err != nil {
		return nil, nil, fmt.Errorf("failed to get royalties: %w", err)
	}

	// Compute summary
	summary := &RoyaltySummary{
		ByPlatform: make(map[string]PlatformRoyaltySummary),
	}
	summaryQuery := s.db.WithContext(ctx).
		Model(&ExternalStreamingRoyalty{}).
		Where("creator_id = ? AND import_status = ?", creatorID, string(ImportCompleted))
	if startDate != nil {
		summaryQuery = summaryQuery.Where("reporting_period_start >= ?", *startDate)
	}
	if endDate != nil {
		summaryQuery = summaryQuery.Where("reporting_period_end <= ?", *endDate)
	}
	if platform != nil && *platform != "" {
		summaryQuery = summaryQuery.Where("platform = ?", *platform)
	}

	var summaryRows []struct {
		Platform          string `gorm:"column:platform"`
		TotalStreams      int64  `gorm:"column:total_streams"`
		TotalRevenueCents int64  `gorm:"column:total_revenue_cents"`
	}
	summaryQuery.Select("platform, SUM(total_streams) as total_streams, SUM(total_revenue_cents) as total_revenue_cents").
		Group("platform").Scan(&summaryRows)

	for _, row := range summaryRows {
		summary.TotalStreams += row.TotalStreams
		summary.TotalRevenueCents += row.TotalRevenueCents
		summary.ByPlatform[row.Platform] = PlatformRoyaltySummary{
			Streams:      row.TotalStreams,
			RevenueCents: row.TotalRevenueCents,
		}
	}

	return royalties, summary, nil
}

// RoyaltySummary provides aggregated royalty data
type RoyaltySummary struct {
	TotalStreams      int64                             `json:"total_streams"`
	TotalRevenueCents int64                             `json:"total_revenue_cents"`
	ByPlatform        map[string]PlatformRoyaltySummary `json:"by_platform"`
}

// PlatformRoyaltySummary provides per-platform aggregated data
type PlatformRoyaltySummary struct {
	Streams      int64 `json:"streams"`
	RevenueCents int64 `json:"revenue_cents"`
}