import 'dart:convert';
import 'dart:typed_data';

import 'package:halkyon_learn_flutter/src/feature/feedback/data/feedback_gateway.dart';
import 'package:halkyon_learn_flutter/src/feature/feedback/model/feedback.dart';

/// A [FeedbackWriteGateway] in memory: what was written, in order.
class FakeFeedbackWriteGateway() implements FeedbackWriteGateway {
  /// The threads written: their published studyset, kind and payload JSON.
  final threads =
      <
        ({String publicationId, FeedbackKind kind, Map<String, Object?> json})
      >[];

  /// The replies written, by thread.
  final messages = <({String threadId, Map<String, Object?> json})>[];

  /// The decisions written, by thread.
  final decisions = <({String threadId, FeedbackDecision decision})>[];

  @override
  Future<String> insertThread({
    required String publicationId,
    required FeedbackKind kind,
    required ByteData payload,
  }) async {
    threads.add((
      publicationId: publicationId,
      kind: kind,
      json: _json(payload),
    ));
    return 'thread-${threads.length}';
  }

  @override
  Future<void> insertMessage(String threadId, ByteData payload) async =>
      messages.add((threadId: threadId, json: _json(payload)));

  @override
  Future<void> insertDecision(
    String threadId,
    FeedbackDecision decision,
  ) async => decisions.add((threadId: threadId, decision: decision));

  static Map<String, Object?> _json(ByteData payload) =>
      jsonDecode(utf8.decode(Uint8List.sublistView(payload)))
          as Map<String, Object?>;
}

/// A [FeedbackServerGateway] in memory: [threads] as the instance gathers
/// them (all public, for the inbox too), [files] by SHA-256.
class FakeFeedbackServerGateway({
  final List<FeedbackThread> threads = const [],
  final Map<String, Uint8List> files = const {},
}) implements FeedbackServerGateway {
  late var _threads = [...threads];

  /// The threads read, and the people blocked.
  final seen = <String>[];
  final blocked = <String>[];

  /// When set, every request fails with it.
  Exception? fail;

  /// Replaces what the instance gathers.
  set gathered(List<FeedbackThread> threads) => _threads = [...threads];

  Future<void> _maybeFail() async {
    if (fail case final error?) {
      throw error;
    }
  }

  @override
  Future<List<FeedbackThread>> threadsOf(String publicId) async {
    await _maybeFail();
    return [
      for (final thread in _threads)
        if (thread.publicId == publicId) thread,
    ];
  }

  @override
  Future<List<FeedbackThread>> inbox() async {
    await _maybeFail();
    return [
      for (final thread in _threads)
        if (thread.mine || thread.forMe) thread,
    ];
  }

  @override
  Future<int> unseen() async =>
      (await inbox()).where((thread) => thread.unseen).length;

  @override
  Future<void> markSeen(String threadId) async {
    await _maybeFail();
    seen.add(threadId);
  }

  @override
  Future<void> block(String handle) async => blocked.add(handle);

  @override
  Future<void> unblock(String handle) async => blocked.remove(handle);

  @override
  Future<List<String>> blockedPeople() async => [...blocked];

  @override
  Future<Uint8List> file(String threadId, String sha256) async {
    await _maybeFail();
    return files[sha256]!;
  }
}