using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using GermanApp.Application.Services;
using GermanApp.Domain.Interfaces;
using Microsoft.Extensions.Logging;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Moq;

namespace GermanApp.Tests.Unit.Application.Services;

[TestClass]
public class StoryGenerationServiceTests
{
    private Mock<IMistralService> _mockMistralService;
    private Mock<ILogger<StoryGenerationService>> _mockLogger;
    private StoryGenerationService _service;

    [TestInitialize]
    public void Setup()
    {
        _mockMistralService = new Mock<IMistralService>();
        _mockLogger = new Mock<ILogger<StoryGenerationService>>();
        _service = new StoryGenerationService(
            _mockMistralService.Object,
            _mockLogger.Object);
    }

    [TestMethod]
    public async Task GenerateStoryAsync_WithValidParameters_ReturnsStory()
    {
        // Arrange
        var expectedStory = "Once upon a time in Germany...";
        var level = "A1";
        var topic = "Travel";
        var vocabularyWords = new List<string> { "Bahn", "Reise", "Stadt" };
        var length = 200;
        var cancellationToken = CancellationToken.None;

        _mockMistralService.Setup(s => s.GenerateStoryAsync(
            level, topic, vocabularyWords, length, cancellationToken))
            .ReturnsAsync(expectedStory);

        // Act
        var result = await _service.GenerateStoryAsync(
            level, topic, vocabularyWords, length, cancellationToken);

        // Assert
        Assert.AreEqual(expectedStory, result);
        _mockMistralService.Verify(s => s.GenerateStoryAsync(
            level, topic, vocabularyWords, length, cancellationToken), Times.Once);
    }

    [TestMethod]
    public async Task GenerateStoryAsync_WithEmptyStory_ThrowsAiServiceException()
    {
        // Arrange
        var level = "A1";
        var topic = "Travel";
        var vocabularyWords = new List<string> { "Bahn" };
        var cancellationToken = CancellationToken.None;

        _mockMistralService.Setup(s => s.GenerateStoryAsync(
            level, topic, vocabularyWords, 200, cancellationToken))
            .ReturnsAsync(string.Empty);

        // Act & Assert
        try
        {
            await _service.GenerateStoryAsync(level, topic, vocabularyWords, 200, cancellationToken);
            Assert.Fail("Expected AiServiceException was not thrown");
        }
        catch (AiServiceException)
        {
            // Expected - StoryGenerationService wraps validation exceptions in AiServiceException
        }
    }

    [TestMethod]
    public async Task GenerateStoryAsync_WithNullStory_ThrowsAiServiceException()
    {
        // Arrange
        var level = "A1";
        var topic = "Travel";
        var vocabularyWords = new List<string> { "Bahn" };
        var cancellationToken = CancellationToken.None;

        _mockMistralService.Setup(s => s.GenerateStoryAsync(
            level, topic, vocabularyWords, 200, cancellationToken))
            .ReturnsAsync((string?)null);

        // Act & Assert
        try
        {
            await _service.GenerateStoryAsync(level, topic, vocabularyWords, 200, cancellationToken);
            Assert.Fail("Expected AiServiceException was not thrown");
        }
        catch (AiServiceException)
        {
            // Expected - StoryGenerationService wraps validation exceptions in AiServiceException
        }
    }

    [TestMethod]
    public async Task GenerateStoryAsync_WhenMistralThrows_ThrowsAiServiceException()
    {
        // Arrange
        var level = "A1";
        var topic = "Travel";
        var vocabularyWords = new List<string> { "Bahn" };
        var cancellationToken = CancellationToken.None;

        _mockMistralService.Setup(s => s.GenerateStoryAsync(
            level, topic, vocabularyWords, 200, cancellationToken))
            .ThrowsAsync(new Exception("API Error"));

        // Act & Assert
        try
        {
            await _service.GenerateStoryAsync(level, topic, vocabularyWords, 200, cancellationToken);
            Assert.Fail("Expected AiServiceException was not thrown");
        }
        catch (AiServiceException)
        {
            // Expected
        }
    }

    [TestMethod]
    public async Task GenerateLessonStoryAsync_WithValidParameters_CallsGenerateStory()
    {
        // Arrange
        var expectedStory = "Lesson story...";
        var lessonTitle = "Greetings";
        var level = "A1";
        var vocabularyWords = new List<string> { "Hallo", "Tschüss" };
        var length = 250;
        var cancellationToken = CancellationToken.None;

        _mockMistralService.Setup(s => s.GenerateStoryAsync(
            level, lessonTitle, vocabularyWords, length, cancellationToken))
            .ReturnsAsync(expectedStory);

        // Act
        var result = await _service.GenerateLessonStoryAsync(
            lessonTitle, level, vocabularyWords, length, cancellationToken);

        // Assert
        Assert.AreEqual(expectedStory, result);
        _mockMistralService.Verify(s => s.GenerateStoryAsync(
            level, lessonTitle, vocabularyWords, length, cancellationToken), Times.Once);
    }

    [TestMethod]
    public async Task GenerateLessonStoryAsync_WithDefaultLength_Uses250()
    {
        // Arrange
        var expectedStory = "Lesson story...";
        var lessonTitle = "Greetings";
        var level = "A1";
        var vocabularyWords = new List<string> { "Hallo" };
        var cancellationToken = CancellationToken.None;

        _mockMistralService.Setup(s => s.GenerateStoryAsync(
            level, lessonTitle, vocabularyWords, 250, cancellationToken))
            .ReturnsAsync(expectedStory);

        // Act
        var result = await _service.GenerateLessonStoryAsync(
            lessonTitle, level, vocabularyWords, cancellationToken: cancellationToken);

        // Assert
        Assert.AreEqual(expectedStory, result);
    }

    [TestMethod]
    public async Task GenerateStoriesByLevelAsync_WithMultipleLevels_ReturnsAllStories()
    {
        // Arrange
        var topic = "Food";
        var vocabularyByLevel = new Dictionary<string, IReadOnlyList<string>>
        {
            ["A1"] = new List<string> { "Apfel", "Banane" },
            ["A2"] = new List<string> { "Restaurant", "Bestrellung" }
        };
        var lengthByLevel = new Dictionary<string, int>
        {
            ["A1"] = 100,
            ["A2"] = 150
        };
        var cancellationToken = CancellationToken.None;

        _mockMistralService.Setup(s => s.GenerateStoryAsync("A1", topic, vocabularyByLevel["A1"], 100, cancellationToken))
            .ReturnsAsync("A1 story");
        _mockMistralService.Setup(s => s.GenerateStoryAsync("A2", topic, vocabularyByLevel["A2"], 150, cancellationToken))
            .ReturnsAsync("A2 story");

        // Act
        var result = await _service.GenerateStoriesByLevelAsync(
            topic, vocabularyByLevel, lengthByLevel, cancellationToken);

        // Assert
        Assert.AreEqual(2, result.Count);
        Assert.AreEqual("A1 story", result["A1"]);
        Assert.AreEqual("A2 story", result["A2"]);
    }

    [TestMethod]
    public async Task GenerateStoriesByLevelAsync_WithMissingLength_UsesDefault()
    {
        // Arrange
        var topic = "Food";
        var vocabularyByLevel = new Dictionary<string, IReadOnlyList<string>>
        {
            ["A1"] = new List<string> { "Apfel" }
        };
        // No lengthByLevel provided
        var cancellationToken = CancellationToken.None;

        _mockMistralService.Setup(s => s.GenerateStoryAsync("A1", topic, vocabularyByLevel["A1"], 200, cancellationToken))
            .ReturnsAsync("A1 story");

        // Act
        var result = await _service.GenerateStoriesByLevelAsync(
            topic, vocabularyByLevel, null, cancellationToken);

        // Assert
        Assert.AreEqual(1, result.Count);
        Assert.AreEqual("A1 story", result["A1"]);
    }

    [TestMethod]
    public async Task GenerateStoriesByLevelAsync_WhenOneLevelFails_ReturnsEmptyForThatLevel()
    {
        // Arrange
        var topic = "Food";
        var vocabularyByLevel = new Dictionary<string, IReadOnlyList<string>>
        {
            ["A1"] = new List<string> { "Apfel" },
            ["A2"] = new List<string> { "Restaurant" }
        };
        var cancellationToken = CancellationToken.None;

        _mockMistralService.Setup(s => s.GenerateStoryAsync("A1", topic, vocabularyByLevel["A1"], 200, cancellationToken))
            .ReturnsAsync("A1 story");
        _mockMistralService.Setup(s => s.GenerateStoryAsync("A2", topic, vocabularyByLevel["A2"], 200, cancellationToken))
            .ThrowsAsync(new Exception("Error"));

        // Act
        var result = await _service.GenerateStoriesByLevelAsync(
            topic, vocabularyByLevel, null, cancellationToken);

        // Assert
        Assert.AreEqual(2, result.Count);
        Assert.AreEqual("A1 story", result["A1"]);
        Assert.AreEqual(string.Empty, result["A2"]);
    }

    [TestMethod]
    public async Task TestServiceAsync_WithWorkingService_ReturnsTrue()
    {
        // Arrange
        var cancellationToken = CancellationToken.None;
        _mockMistralService.Setup(s => s.GenerateStoryAsync(
            "A1", "Test", It.IsAny<IReadOnlyList<string>>(), 50, cancellationToken))
            .ReturnsAsync("Test story");

        // Act
        var result = await _service.TestServiceAsync(cancellationToken);

        // Assert
        Assert.IsTrue(result);
    }

    [TestMethod]
    public async Task TestServiceAsync_WhenServiceFails_ReturnsFalse()
    {
        // Arrange
        var cancellationToken = CancellationToken.None;
        _mockMistralService.Setup(s => s.GenerateStoryAsync(
            "A1", "Test", It.IsAny<IReadOnlyList<string>>(), 50, cancellationToken))
            .ThrowsAsync(new Exception("Error"));

        // Act
        var result = await _service.TestServiceAsync(cancellationToken);

        // Assert
        Assert.IsFalse(result);
    }

    [TestMethod]
    public async Task TestServiceAsync_WithEmptyResult_ReturnsFalse()
    {
        // Arrange
        var cancellationToken = CancellationToken.None;
        _mockMistralService.Setup(s => s.GenerateStoryAsync(
            "A1", "Test", It.IsAny<IReadOnlyList<string>>(), 50, cancellationToken))
            .ReturnsAsync(string.Empty);

        // Act
        var result = await _service.TestServiceAsync(cancellationToken);

        // Assert
        Assert.IsFalse(result);
    }
}