package services

import (
	"bookhoard/internal/database"
	"context"
	"encoding/json"
	"errors"
	"fmt"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgtype"
)

type DashboardService struct {
	db                *database.Queries
	collectionService *CollectionService
}

func NewDashboardService(db *database.Queries) *DashboardService {
	return &DashboardService{
		db:                db,
		collectionService: NewCollectionService(db),
	}
}

// viewSettingsFlag reads a boolean key from a collection's view_settings
// JSONB. Malformed or absent → false.
func viewSettingsFlag(raw []byte, key string) bool {
	if len(raw) == 0 {
		return false
	}
	var settings map[string]interface{}
	if err := json.Unmarshal(raw, &settings); err != nil {
		return false
	}
	b, ok := settings[key].(bool)
	return ok && b
}

// viewSettingsHasKey reports whether the key exists at all (any value) —
// used for provenance markers like imported_from_series.
func viewSettingsHasKey(raw []byte, key string) bool {
	if len(raw) == 0 {
		return false
	}
	var settings map[string]interface{}
	if err := json.Unmarshal(raw, &settings); err != nil {
		return false
	}
	_, ok := settings[key]
	return ok
}

type DashboardSection struct {
	CollectionID   uuid.UUID
	CollectionName string
	Items          []database.MediaItems
	QueryType      string
	Priority       int
	IsSystem       bool
	Title          string
	Description    string
	Icon           string
	// A2c: the collection's own ordering-construct marker — the section is
	// a curated playlist ("The Witcher (Reading Order)"), rendered with a
	// badge by the frontend.
	IsPlaylist bool
	// A2c §3.5: hide_finished filtered every item out of a NON-empty
	// collection — render "playlist complete" instead of dropping silently.
	Complete bool
}

func (s *DashboardService) GetDashboardSections(
	ctx context.Context,
	userID uuid.UUID,
	libraryID pgtype.UUID,
	limit int,
	collectionOrder []string,
	hiddenCollections []string,
) ([]DashboardSection, error) {
	var results []DashboardSection

	systemCollections, err := s.db.GetSystemCollectionsForDashboard(ctx, pgtype.UUID{Bytes: userID, Valid: true})
	if err != nil {
		return nil, err
	}

	for _, coll := range systemCollections {
		items, err := s.getCollectionItemsByQueryType(ctx, coll, userID, libraryID, limit)
		if err != nil {
			continue
		}

		results = append(results, DashboardSection{
			CollectionID:   coll.ID.Bytes,
			CollectionName: coll.Name,
			Items:          items,
			QueryType:      coll.QueryType.String,
			Priority:       int(coll.Priority.Int32),
			IsSystem:       coll.IsSystemCollection.Bool,
			Title:          coll.Name,
			Description:    coll.Description.String,
			Icon:           coll.Icon.String,
		})
	}

	userCollections, err := s.db.GetUserCollectionsForDashboard(ctx, pgtype.UUID{Bytes: userID, Valid: true})
	if err != nil {
		return nil, err
	}

	for _, coll := range userCollections {
		items, err := s.getUserCollectionItems(ctx, coll, userID, libraryID, limit)
		if err != nil {
			continue
		}

		// A2c §3.5: hide_finished filtered everything out — but the
		// collection is NOT empty. That's a finished playlist: render a
		// completion marker instead of silently vanishing.
		if len(items) == 0 {
			hideFinished := viewSettingsFlag(coll.ViewSettings, "hide_finished")
			if hideFinished {
				collUUIDBytes, _ := uuid.FromBytes(coll.ID.Bytes[0:16])
				if count, countErr := s.db.CountCollectionItems(ctx, pgtype.UUID{Bytes: collUUIDBytes, Valid: true}); countErr == nil && count > 0 {
					results = append(results, DashboardSection{
						CollectionID:   coll.ID.Bytes,
						CollectionName: coll.Name,
						Items:          []database.MediaItems{},
						QueryType:      coll.QueryType.String,
						Priority:       int(coll.Priority.Int32),
						IsSystem:       false,
						Title:          coll.Name,
						Description:    coll.Description.String,
						Icon:           coll.Icon.String,
						IsPlaylist:     viewSettingsHasKey(coll.ViewSettings, "imported_from_series"),
						Complete:       true,
					})
				}
			}
			continue
		}

		results = append(results, DashboardSection{
			CollectionID:   coll.ID.Bytes,
			CollectionName: coll.Name,
			Items:          items,
			QueryType:      coll.QueryType.String,
			Priority:       int(coll.Priority.Int32),
			IsSystem:       false,
			Title:          coll.Name,
			Description:    coll.Description.String,
			Icon:           coll.Icon.String,
			IsPlaylist:     viewSettingsHasKey(coll.ViewSettings, "imported_from_series"),
		})
	}

	results = s.FilterHiddenCollections(results, hiddenCollections)
	results = s.reorderCollections(results, collectionOrder)

	if len(collectionOrder) == 0 {
		results = s.sortByPriority(results)
	}

	return results, nil
}

func (s *DashboardService) FilterHiddenCollections(sections []DashboardSection, hidden []string) []DashboardSection {
	if len(hidden) == 0 {
		return sections
	}

	var filtered []DashboardSection
	for _, section := range sections {
		isHidden := false
		for _, h := range hidden {
			if section.CollectionName == h {
				isHidden = true
				break
			}
		}
		if !isHidden {
			filtered = append(filtered, section)
		}
	}
	return filtered
}

func (s *DashboardService) reorderCollections(sections []DashboardSection, order []string) []DashboardSection {
	if len(order) == 0 {
		return sections
	}

	var ordered []DashboardSection
	remaining := make(map[string]DashboardSection)
	for _, section := range sections {
		remaining[section.CollectionName] = section
	}

	for _, name := range order {
		if section, exists := remaining[name]; exists {
			ordered = append(ordered, section)
			delete(remaining, name)
		}
	}

	for _, section := range sections {
		if _, exists := remaining[section.CollectionName]; exists {
			ordered = append(ordered, section)
		}
	}

	return ordered
}

func (s *DashboardService) sortByPriority(sections []DashboardSection) []DashboardSection {
	sorted := make([]DashboardSection, len(sections))
	copy(sorted, sections)

	for i := 0; i < len(sorted)-1; i++ {
		for j := 0; j < len(sorted)-i-1; j++ {
			if sorted[j].Priority > sorted[j+1].Priority {
				sorted[j], sorted[j+1] = sorted[j+1], sorted[j]
			}
		}
	}

	return sorted
}

func (s *DashboardService) getCollectionItemsByQueryType(ctx context.Context, coll database.Collections, userID uuid.UUID, libraryID pgtype.UUID, limit int) ([]database.MediaItems, error) {
	switch coll.QueryType.String {
	case "continue-reading":
		return s.db.GetContinueReadingItems(ctx, database.GetContinueReadingItemsParams{
			UserID:    pgtype.UUID{Bytes: userID, Valid: true},
			LibraryID: libraryID,
			Limit:     pgtype.Int4{Int32: int32(limit), Valid: true},
		})
	case "recently-added":
		return s.db.GetRecentlyAddedItems(ctx, database.GetRecentlyAddedItemsParams{
			LibraryID: libraryID,
			Limit:     pgtype.Int4{Int32: int32(limit), Valid: true},
		})
	case "recently-read":
		return s.db.GetRecentlyReadItems(ctx, database.GetRecentlyReadItemsParams{
			UserID:    pgtype.UUID{Bytes: userID, Valid: true},
			LibraryID: libraryID,
			Limit:     pgtype.Int4{Int32: int32(limit), Valid: true},
		})
	case "not-started":
		return s.db.GetNotStartedItems(ctx, database.GetNotStartedItemsParams{
			UserID:    pgtype.UUID{Bytes: userID, Valid: true},
			LibraryID: libraryID,
			Limit:     pgtype.Int4{Int32: int32(limit), Valid: true},
		})
	case "continue-series":
		rows, err := s.db.GetContinueSeriesItems(ctx, database.GetContinueSeriesItemsParams{
			LibraryID: libraryID,
			UserID:    pgtype.UUID{Bytes: userID, Valid: true},
			Limit:     pgtype.Int4{Int32: int32(limit), Valid: true},
		})
		if err != nil {
			return nil, err
		}
		items := make([]database.MediaItems, 0, len(rows))
		for _, row := range rows {
			items = append(items, continueSeriesRowToMediaItems(row))
		}
		return items, nil
	default:
		return []database.MediaItems{}, nil
	}
}

func (s *DashboardService) getUserCollectionItems(ctx context.Context, coll database.Collections, userID uuid.UUID, libraryID pgtype.UUID, limit int) ([]database.MediaItems, error) {
	collUUID, _ := uuid.FromBytes(coll.ID.Bytes[0:16])

	// A2c §3.3: per-collection hide_finished (view_settings), evaluated
	// against the VIEWER's reading progress. The section then shows the
	// head of the reading queue in playlist order.
	hideFinished := viewSettingsFlag(coll.ViewSettings, "hide_finished")
	manualItems, err := s.db.GetCollectionItemsForDashboard(ctx, database.GetCollectionItemsForDashboardParams{
		CollectionID: pgtype.UUID{Bytes: collUUID, Valid: true},
		LibraryID:    libraryID,
		ViewerUserID: pgtype.UUID{Bytes: userID, Valid: true},
		HideFinished: pgtype.Bool{Bool: hideFinished, Valid: true},
		Limit:        pgtype.Int4{Int32: int32(limit), Valid: true},
	})
	if err != nil {
		return nil, err
	}

	// The query filters excluded rows in SQL and embeds the media row,
	// so the items are MediaItems as-is.
	var manualNonExcluded []database.MediaItems
	for _, row := range manualItems {
		manualNonExcluded = append(manualNonExcluded, row.MediaItems)
	}

	var autoItems []database.MediaItems
	if len(coll.AutoAssignRules) > 0 {
		var rules []Rule
		if err := json.Unmarshal(coll.AutoAssignRules, &rules); err == nil && len(rules) > 0 {
			allLibraryItems, err := s.db.GetLibraryItems(ctx, libraryID)
			if err == nil {
				for _, item := range allLibraryItems {
					alreadyInCollection := false
					for _, manualItem := range manualNonExcluded {
						manualUUID := uuid.UUID(manualItem.ID.Bytes)
						itemUUID := uuid.UUID(item.ID.Bytes)
						if manualUUID == itemUUID {
							alreadyInCollection = true
							break
						}
					}
					if alreadyInCollection {
						continue
					}

					evaluations := s.collectionService.EvaluateRules(item, rules)
					for _, eval := range evaluations {
						if eval.Matches {
							autoItems = append(autoItems, item)
							break
						}
					}
				}
			}
		}
	}

	var finalItems []database.MediaItems
	finalItems = append(finalItems, manualNonExcluded...)
	finalItems = append(finalItems, autoItems...)

	if len(finalItems) > limit {
		finalItems = finalItems[:limit]
	}

	return finalItems, nil
}

func (s *DashboardService) GetDashboardPreferences(ctx context.Context, userID uuid.UUID, libraryID pgtype.UUID) (database.UserDashboardPreferences, error) {
	// Absent library = the global (All Libraries) scope: a separate
	// one-row-per-user table, so an accidental per-library write can never
	// masquerade as global.
	if !libraryID.Valid {
		g, err := s.db.GetGlobalDashboardPreferences(ctx, pgtype.UUID{Bytes: userID, Valid: true})
		if err != nil {
			return database.UserDashboardPreferences{}, err
		}
		return database.UserDashboardPreferences{
			UserID:            g.UserID,
			HiddenCollections: g.HiddenCollections,
			CollectionOrder:   g.CollectionOrder,
			ItemsPerSection:   g.ItemsPerSection,
			UpdatedAt:         g.UpdatedAt,
		}, nil
	}
	return s.db.GetDashboardPreferences(ctx, database.GetDashboardPreferencesParams{
		UserID:    pgtype.UUID{Bytes: userID, Valid: true},
		LibraryID: libraryID,
	})
}

func (s *DashboardService) UpsertDashboardPreferences(ctx context.Context, params database.UpsertDashboardPreferencesParams) (database.UserDashboardPreferences, error) {
	if !params.LibraryID.Valid {
		g, err := s.db.UpsertGlobalDashboardPreferences(ctx, database.UpsertGlobalDashboardPreferencesParams{
			UserID:            params.UserID,
			HiddenCollections: params.HiddenCollections,
			CollectionOrder:   params.CollectionOrder,
			ItemsPerSection:   params.ItemsPerSection,
		})
		if err != nil {
			return database.UserDashboardPreferences{}, err
		}
		return database.UserDashboardPreferences{
			UserID:            g.UserID,
			HiddenCollections: g.HiddenCollections,
			CollectionOrder:   g.CollectionOrder,
			ItemsPerSection:   g.ItemsPerSection,
			UpdatedAt:         g.UpdatedAt,
		}, nil
	}
	return s.db.UpsertDashboardPreferences(ctx, params)
}

func (s *DashboardService) SanitizeDashboardPreferences(hiddenCollections, collectionOrder []string) ([]string, []string) {
	// Deduplicate collection_order while preserving order
	seen := make(map[string]bool)
	var sanitizedOrder []string
	for _, id := range collectionOrder {
		if !seen[id] {
			seen[id] = true
			sanitizedOrder = append(sanitizedOrder, id)
		}
	}

	// Deduplicate hidden_collections
	seen = make(map[string]bool)
	var sanitizedHidden []string
	for _, id := range hiddenCollections {
		if !seen[id] {
			seen[id] = true
			sanitizedHidden = append(sanitizedHidden, id)
		}
	}

	return sanitizedHidden, sanitizedOrder
}

func (s *DashboardService) RestoreSystemCollection(ctx context.Context, userID uuid.UUID, collectionName string, resetType string) error {
	defaultMetadata := map[string]struct {
		Description string
		Icon        string
		Color       string
		Priority    int32
		QueryType   string
	}{
		"Continue Reading": {"Books you're currently reading (0 < progress < 1)", "📖", "#7aa2f7", 1, "continue-reading"},
		"Recently Added":   {"Newly added items to this library", "🆕", "#9ece6a", 2, "recently-added"},
		"Recently Read":    {"Books you've finished (progress >= 1)", "✅", "#e0af68", 3, "recently-read"},
		"Not Started":      {"Books you haven't read yet (progress = 0 or no record)", "📕", "#f7768e", 4, "not-started"},
		"Continue Series":  {"Next book in series you're reading", "📚", "#bb9af7", 5, "continue-series"},
	}

	meta, exists := defaultMetadata[collectionName]
	if !exists {
		return fmt.Errorf("unknown collection: %s", collectionName)
	}

	// System collections are PERMANENT rows identified by the stable
	// (user_id, query_type) pair — restore never deletes or re-creates,
	// so the row id (and every reference to it: device shelf mappings,
	// dashboard order/hidden prefs, /collections/{id} links) never churns.
	// Resolution includes tombstoned rows: restoring a deleted section
	// un-deletes the exact same row.
	row, err := s.db.GetSystemCollectionByQueryType(ctx, database.GetSystemCollectionByQueryTypeParams{
		UserID:    pgtype.UUID{Bytes: userID, Valid: true},
		QueryType: pgtype.Text{String: meta.QueryType, Valid: true},
	})
	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
		return err
	}

	if errors.Is(err, pgx.ErrNoRows) {
		// Provision: the only path that mints a system-collection row.
		_, cerr := s.db.CreateSystemCollection(ctx, database.CreateSystemCollectionParams{
			UserID:          pgtype.UUID{Bytes: userID, Valid: true},
			Name:            collectionName,
			Description:     pgtype.Text{String: meta.Description, Valid: true},
			Icon:            pgtype.Text{String: meta.Icon, Valid: true},
			Color:           pgtype.Text{String: meta.Color, Valid: true},
			ShowOnDashboard: pgtype.Bool{Bool: true, Valid: true},
			QueryType:       pgtype.Text{String: meta.QueryType, Valid: true},
			Priority:        pgtype.Int4{Int32: meta.Priority, Valid: true},
		})
		return cerr
	}

	// "full": clear item assignments (a fresh section has none) and reset
	// everything, IN PLACE. "keep_books": metadata-only, in place. Both
	// un-tombstone, so a deleted section comes back as the same row.
	if resetType != "keep_books" {
		if err := s.db.ClearCollectionItems(ctx, row.ID); err != nil {
			return err
		}
	}
	_, err = s.db.RestoreSystemCollectionRow(ctx, database.RestoreSystemCollectionRowParams{
		ID:          row.ID,
		Name:        collectionName,
		Description: pgtype.Text{String: meta.Description, Valid: true},
		Icon:        pgtype.Text{String: meta.Icon, Valid: true},
		Color:       pgtype.Text{String: meta.Color, Valid: true},
		Priority:    pgtype.Int4{Int32: meta.Priority, Valid: true},
	})
	return err
}