import 'dart:async';

import 'package:flutter_gemma/flutter_gemma.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:life_helper/data/ai/gemma_llm_service.dart';

/// Unit tests for `collectFunctionCall` (fn-spec §D, 8 cases).
///
/// `GemmaLlmService.load` / `.generateStructured` themselves require the
/// flutter_gemma native runtime and are covered by AC-7 (on-device E2E),
/// not by host tests. The pure stream-parsing helper is unit-testable in
/// isolation because we can feed a synthetic `Stream<ModelResponse>`.
void main() {
  const fn = 'emit_frame_candidates';

  test('1. single FCR with expected name returns args', () async {
    final stream = Stream<ModelResponse>.fromIterable([
      const FunctionCallResponse(
        name: fn,
        args: {
          'candidates': [
            {'text': 'a', 'level': 'L2'},
            {'text': 'b', 'level': 'L2'},
            {'text': 'c', 'level': 'L3'},
          ],
        },
      ),
    ]);
    final args = await collectFunctionCall(stream, fn);
    expect(args['candidates'], hasLength(3));
  });

  test('2. TextResponse before FCR is skipped', () async {
    final stream = Stream<ModelResponse>.fromIterable([
      const TextResponse('hello'),
      const FunctionCallResponse(name: fn, args: {'candidates': []}),
    ]);
    final args = await collectFunctionCall(stream, fn);
    expect(args['candidates'], isEmpty);
  });

  test('3. ThinkingResponse + TextResponse before empty-args FCR', () async {
    final stream = Stream<ModelResponse>.fromIterable([
      const ThinkingResponse('reasoning...'),
      const TextResponse('preamble'),
      const FunctionCallResponse(name: fn, args: {}),
    ]);
    final args = await collectFunctionCall(stream, fn);
    expect(args, isEmpty);
  });

  test('4. wrong function name throws FormatException', () async {
    final stream = Stream<ModelResponse>.fromIterable([
      const FunctionCallResponse(name: 'wrong_name', args: {}),
    ]);
    expect(
      () => collectFunctionCall(stream, fn),
      throwsA(
        isA<FormatException>().having(
          (e) => e.message,
          'message',
          contains('wrong_name'),
        ),
      ),
    );
  });

  test('5. text-only stream throws "no function call emitted"', () async {
    final stream = Stream<ModelResponse>.fromIterable([
      const TextResponse('only text, no call'),
    ]);
    expect(
      () => collectFunctionCall(stream, fn),
      throwsA(
        isA<FormatException>().having(
          (e) => e.message,
          'message',
          contains('no function call emitted'),
        ),
      ),
    );
  });

  test('6. stream error throws sanitized FormatException (no leak)', () async {
    final stream = Stream<ModelResponse>.error(
      Exception('SENSITIVE: user_prompt_leaked_in_error'),
    );
    expect(
      () => collectFunctionCall(stream, fn),
      throwsA(
        isA<FormatException>().having(
          (e) => e.message,
          'message',
          allOf(
            equals('stream error'),
            isNot(contains('SENSITIVE')),
            isNot(contains('user_prompt_leaked_in_error')),
          ),
        ),
      ),
    );
  });

  test('7. FCR with empty args map returns empty map (no throw)', () async {
    final stream = Stream<ModelResponse>.fromIterable([
      const FunctionCallResponse(name: fn, args: {}),
    ]);
    final args = await collectFunctionCall(stream, fn);
    expect(args, isEmpty);
  });

  test('8. empty stream throws "no function call emitted"', () async {
    final stream = const Stream<ModelResponse>.empty();
    expect(
      () => collectFunctionCall(stream, fn),
      throwsA(
        isA<FormatException>().having(
          (e) => e.message,
          'message',
          contains('no function call emitted'),
        ),
      ),
    );
  });

  group('ParallelFunctionCallResponse', () {
    test('first call with expected name returns its args', () async {
      final stream = Stream<ModelResponse>.fromIterable([
        ParallelFunctionCallResponse(calls: [
          const FunctionCallResponse(name: fn, args: {'x': 1}),
          const FunctionCallResponse(name: 'other', args: {'y': 2}),
        ]),
      ]);
      final args = await collectFunctionCall(stream, fn);
      expect(args['x'], 1);
    });

    test('first call with wrong name throws', () async {
      final stream = Stream<ModelResponse>.fromIterable([
        ParallelFunctionCallResponse(calls: [
          const FunctionCallResponse(name: 'wrong_first', args: {}),
        ]),
      ]);
      expect(
        () => collectFunctionCall(stream, fn),
        throwsA(isA<FormatException>()),
      );
    });
  });
}