import 'package:async/async.dart';
import 'package:commons_core/commons_core.dart';
import 'package:drift/drift.dart';
import 'package:equatable/equatable.dart';

import '../db/database.dart';
import '../db/enums.dart';

/// A lightweight row for the inventory list (only what the list renders).
class VarietyListItem extends Equatable {
  const VarietyListItem({required this.id, required this.label, this.category});

  final String id;
  final String label;
  final String? category;

  @override
  List<Object?> get props => [id, label, category];
}

/// One held batch of a variety, for the detail view.
class VarietyLot extends Equatable {
  const VarietyLot({
    required this.id,
    this.harvestYear,
    this.quantity,
    this.storageLocation,
  });

  final String id;
  final int? harvestYear;
  final Quantity? quantity;
  final String? storageLocation;

  @override
  List<Object?> get props => [id, harvestYear, quantity, storageLocation];
}

/// The full detail of one variety (identity + its lots, names and first photo).
class VarietyDetail extends Equatable {
  const VarietyDetail({
    required this.id,
    required this.label,
    this.category,
    this.notes,
    this.lots = const [],
    this.vernacularNames = const [],
    this.photo,
  });

  final String id;
  final String label;
  final String? category;
  final String? notes;
  final List<VarietyLot> lots;
  final List<String> vernacularNames;
  final Uint8List? photo;

  @override
  List<Object?> get props => [
    id,
    label,
    category,
    notes,
    lots,
    vernacularNames,
    photo,
  ];
}

/// Reads and writes the inventory. The encrypted Drift DB is the single source
/// of truth; [watchInventory] exposes a reactive stream the UI subscribes to.
///
/// Every write stamps the row with the local [Hlc] and [nodeId] so the CRDT
/// metadata is correct from day one, even though sync does not exist yet.
class VarietyRepository {
  VarietyRepository(
    this._db, {
    required this.idGen,
    required this.nodeId,
    int Function()? nowMillis,
  }) : _now = nowMillis ?? (() => DateTime.now().millisecondsSinceEpoch),
       _clock = Hlc.zero(nodeId);

  final AppDatabase _db;
  final IdGen idGen;
  final String nodeId;
  final int Function() _now;
  Hlc _clock;

  /// Emits the non-deleted inventory, ordered by category then label.
  Stream<List<VarietyListItem>> watchInventory() {
    final query = _db.select(_db.varieties)
      ..where((v) => v.isDeleted.equals(false))
      ..orderBy([
        (v) => OrderingTerm(expression: v.category),
        (v) => OrderingTerm(expression: v.label),
      ]);
    return query.watch().map(
      (rows) => rows
          .map(
            (v) =>
                VarietyListItem(id: v.id, label: v.label, category: v.category),
          )
          .toList(),
    );
  }

  /// The 20-second quick-add: a [label] (required) plus an optional [category],
  /// an optional [quantity] (creates a Lot) and an optional [photoBytes]
  /// (stored as an encrypted BLOB Attachment). Returns the new Variety id.
  Future<String> addQuickVariety({
    required String label,
    String? category,
    Quantity? quantity,
    Uint8List? photoBytes,
  }) async {
    final varietyId = idGen.newId();
    await _db.transaction(() async {
      final (created, updated) = _stamp();
      await _db
          .into(_db.varieties)
          .insert(
            VarietiesCompanion.insert(
              id: varietyId,
              label: label,
              createdAt: created,
              updatedAt: updated,
              lastAuthor: nodeId,
              category: Value(category),
            ),
          );

      if (quantity != null) {
        final (created, updated) = _stamp();
        await _db
            .into(_db.lots)
            .insert(
              LotsCompanion.insert(
                id: idGen.newId(),
                varietyId: varietyId,
                createdAt: created,
                updatedAt: updated,
                lastAuthor: nodeId,
                quantityKind: Value(quantity.kind.name),
                quantityPrecise: Value(quantity.precise),
                quantityLabel: Value(quantity.label),
              ),
            );
      }

      if (photoBytes != null) {
        final (created, updated) = _stamp();
        await _db
            .into(_db.attachments)
            .insert(
              AttachmentsCompanion.insert(
                id: idGen.newId(),
                createdAt: created,
                updatedAt: updated,
                lastAuthor: nodeId,
                parentType: ParentType.variety,
                parentId: varietyId,
                kind: AttachmentKind.photo,
                bytes: Value(photoBytes),
                mimeType: const Value('image/jpeg'),
              ),
            );
      }
    });
    return varietyId;
  }

  /// Reactively watches one variety with its lots, vernacular names and first
  /// photo. Emits `null` if the variety does not exist or is soft-deleted.
  ///
  /// Re-emits whenever the variety or any related row changes: a merged trigger
  /// stream over the four tables drives a full reload, so adding a lot (a change
  /// to a *different* table) still refreshes the view.
  Stream<VarietyDetail?> watchVariety(String id) {
    final triggers = StreamGroup.merge<void>([
      (_db.select(
        _db.varieties,
      )..where((v) => v.id.equals(id))).watch().map((_) {}),
      (_db.select(
        _db.lots,
      )..where((l) => l.varietyId.equals(id))).watch().map((_) {}),
      (_db.select(
        _db.varietyVernacularNames,
      )..where((n) => n.varietyId.equals(id))).watch().map((_) {}),
      (_db.select(
        _db.attachments,
      )..where((a) => a.parentId.equals(id))).watch().map((_) {}),
    ]);
    return triggers.asyncMap((_) => _loadVariety(id));
  }

  Future<VarietyDetail?> _loadVariety(String id) async {
    final v =
        await (_db.select(_db.varieties)
              ..where((t) => t.id.equals(id) & t.isDeleted.equals(false)))
            .getSingleOrNull();
    if (v == null) return null;

    final lots =
        await (_db.select(_db.lots)
              ..where((l) => l.varietyId.equals(id) & l.isDeleted.equals(false))
              ..orderBy([(l) => OrderingTerm.desc(l.harvestYear)]))
            .get();
    final names = await (_db.select(
      _db.varietyVernacularNames,
    )..where((n) => n.varietyId.equals(id) & n.isDeleted.equals(false))).get();
    final photos =
        await (_db.select(_db.attachments)
              ..where(
                (a) =>
                    a.parentId.equals(id) &
                    a.parentType.equalsValue(ParentType.variety) &
                    a.kind.equalsValue(AttachmentKind.photo) &
                    a.isDeleted.equals(false),
              )
              ..limit(1))
            .get();

    return VarietyDetail(
      id: v.id,
      label: v.label,
      category: v.category,
      notes: v.notes,
      lots: lots.map(_toLot).toList(),
      vernacularNames: names.map((n) => n.name).toList(),
      photo: photos.isEmpty ? null : photos.first.bytes,
    );
  }

  /// Updates a variety's scalar fields (LWW). Passing null clears [category]
  /// and [notes]; a null [label] leaves the label unchanged.
  Future<void> updateVariety({
    required String id,
    String? label,
    String? category,
    String? notes,
  }) async {
    final (_, updated) = _stamp();
    await (_db.update(_db.varieties)..where((v) => v.id.equals(id))).write(
      VarietiesCompanion(
        label: label == null ? const Value.absent() : Value(label),
        category: Value(category),
        notes: Value(notes),
        updatedAt: Value(updated),
        lastAuthor: Value(nodeId),
      ),
    );
  }

  /// Adds a lot (a held batch) to a variety. Returns the new lot id.
  Future<String> addLot({
    required String varietyId,
    int? harvestYear,
    Quantity? quantity,
    String? storageLocation,
  }) async {
    final (created, updated) = _stamp();
    final id = idGen.newId();
    await _db
        .into(_db.lots)
        .insert(
          LotsCompanion.insert(
            id: id,
            varietyId: varietyId,
            createdAt: created,
            updatedAt: updated,
            lastAuthor: nodeId,
            harvestYear: Value(harvestYear),
            quantityKind: Value(quantity?.kind.name),
            quantityPrecise: Value(quantity?.precise),
            quantityLabel: Value(quantity?.label),
            storageLocation: Value(storageLocation),
          ),
        );
    return id;
  }

  /// Soft-deletes a variety (tombstone); it disappears from the inventory but
  /// the row survives for correct CRDT merges later.
  Future<void> softDeleteVariety(String id) async {
    final (_, updated) = _stamp();
    await (_db.update(_db.varieties)..where((v) => v.id.equals(id))).write(
      VarietiesCompanion(
        isDeleted: const Value(true),
        updatedAt: Value(updated),
        lastAuthor: Value(nodeId),
      ),
    );
  }

  VarietyLot _toLot(Lot l) {
    final hasQuantity =
        l.quantityKind != null ||
        l.quantityPrecise != null ||
        l.quantityLabel != null;
    return VarietyLot(
      id: l.id,
      harvestYear: l.harvestYear,
      storageLocation: l.storageLocation,
      quantity: hasQuantity
          ? Quantity(
              kind: _parseKind(l.quantityKind),
              precise: l.quantityPrecise,
              label: l.quantityLabel,
            )
          : null,
    );
  }

  QuantityKind _parseKind(String? name) =>
      QuantityKind.values.asNameMap()[name] ?? QuantityKind.aFew;

  /// Advances the local clock and returns `(createdAtMillis, packedHlc)`.
  (int, String) _stamp() {
    final now = _now();
    _clock = _clock.localEvent(now);
    return (now, _clock.pack());
  }
}