using System.Net;
using System.Text;
using System.Text.Json;
using FiscalFlow.Core.Interfaces;
using FiscalFlow.Infrastructure.Services;
using FluentAssertions;
using Microsoft.Extensions.Logging;
using Moq;
using Xunit;

namespace FiscalFlow.UnitTests.Services;

public sealed class OcrServiceTests
{
    private readonly Mock<ILogger<OcrService>> _loggerMock;

    public OcrServiceTests()
    {
        _loggerMock = new Mock<ILogger<OcrService>>();
    }

    [Fact]
    public async Task ExtractAsync_SuccessfulExtraction_ReturnsCompleteOcrResult()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "Processed document abc123",
            result = new
            {
                document_id = "abc123",
                success = true,
                document_type = "invoice",
                fields = new Dictionary<string, string?>
                {
                    ["InvoiceNumber"] = "INV-001",
                    ["InvoiceDate"] = "2024-01-15",
                    ["InvoiceDueDate"] = "2024-02-15",
                    ["OCR"] = "123456789",
                    ["Bankgiro"] = "1234-5678",
                    ["Plusgiro"] = null,
                    ["Amount"] = "12500.00",
                    ["SupplierName"] = "Test AB",
                    ["supplier_org_number"] = "556677-8899",
                    ["customer_number"] = "C-001",
                    ["payment_line"] = "# 123456789 # 12500 00 #",
                    ["Currency"] = "SEK",
                },
                confidence = new Dictionary<string, decimal>
                {
                    ["InvoiceNumber"] = 0.95m,
                    ["InvoiceDate"] = 0.88m,
                    ["Amount"] = 0.92m,
                },
                detections = new List<object>(),
                processing_time_ms = 1234.5,
                errors = new List<string>(),
                vat_summary = new
                {
                    breakdowns = new[]
                    {
                        new
                        {
                            rate = 25.0m,
                            vat_amount = "2500.00",
                            base_amount = "10000.00",
                            source = "regex",
                        },
                    },
                    total_excl_vat = "10000.00",
                    total_vat = "2500.00",
                    total_incl_vat = "12500.00",
                    confidence = 0.85m,
                },
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.Success.Should().BeTrue();
        result.Confidence.Should().Be(0.9167m);
        result.ProcessingTimeMs.Should().Be(1234.5);
        result.DocumentType.Should().Be("invoice");
        result.FieldConfidences.Should().ContainKey("InvoiceNumber").WhoseValue.Should().Be(0.95m);
        result.FieldConfidences.Should().ContainKey("InvoiceDate").WhoseValue.Should().Be(0.88m);
        result.FieldConfidences.Should().ContainKey("Amount").WhoseValue.Should().Be(0.92m);

        var data = result.Data;
        data.Should().NotBeNull();
        data!.InvoiceNumber.Should().Be("INV-001");
        data.InvoiceDate.Should().Be(new DateTime(2024, 1, 15));
        data.DueDate.Should().Be(new DateTime(2024, 2, 15));
        data.OcrNumber.Should().Be("123456789");
        data.Bankgiro.Should().Be("1234-5678");
        data.Plusgiro.Should().BeNull();
        data.AmountTotal.Should().Be(12500.00m);
        data.SupplierName.Should().Be("Test AB");
        data.SupplierOrgNumber.Should().Be("556677-8899");
        data.CustomerNumber.Should().Be("C-001");
        data.PaymentLine.Should().Be("# 123456789 # 12500 00 #");
        data.Currency.Should().Be("SEK");
        data.AmountVat.Should().Be(2500.00m);
        data.VatRate.Should().Be(25);
    }

    [Fact]
    public async Task ExtractAsync_FieldMapping_MapsAllFieldsCorrectly()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>
                {
                    ["InvoiceNumber"] = "TEST-123",
                    ["InvoiceDate"] = "2024-03-20",
                    ["InvoiceDueDate"] = "2024-04-20",
                    ["OCR"] = "987654321",
                    ["Bankgiro"] = "9999-8888",
                    ["Plusgiro"] = "123456-7",
                    ["Amount"] = "5000.00",
                    ["supplier_org_number"] = "111222-3333",
                    ["customer_number"] = "CUST-999",
                    ["payment_line"] = "Payment reference line",
                },
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 500.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        var data = result.Data;
        data.Should().NotBeNull();
        data!.InvoiceNumber.Should().Be("TEST-123");
        data.InvoiceDate.Should().Be(new DateTime(2024, 3, 20));
        data.DueDate.Should().Be(new DateTime(2024, 4, 20));
        data.OcrNumber.Should().Be("987654321");
        data.Bankgiro.Should().Be("9999-8888");
        data.Plusgiro.Should().Be("123456-7");
        data.AmountTotal.Should().Be(5000.00m);
        data.SupplierOrgNumber.Should().Be("111222-3333");
        data.CustomerNumber.Should().Be("CUST-999");
        data.PaymentLine.Should().Be("Payment reference line");
    }

    [Fact]
    public async Task ExtractAsync_VatSummaryParsing_PopulatesVatFieldsFromTotalVat()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>(),
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
                vat_summary = new
                {
                    total_vat = "1250.50",
                    breakdowns = new[]
                    {
                        new
                        {
                            rate = 25.0m,
                            vat_amount = "1250.50",
                            base_amount = "5000.00",
                            source = "table",
                        },
                    },
                },
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        var data = result.Data;
        data.Should().NotBeNull();
        data!.AmountVat.Should().Be(1250.50m);
        data.VatRate.Should().Be(25);
    }

    [Fact]
    public async Task ExtractAsync_VatSummaryWithoutTotalVat_SumsFromBreakdowns()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>(),
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
                vat_summary = new
                {
                    breakdowns = new[]
                    {
                        new
                        {
                            rate = 25.0m,
                            vat_amount = "1000.00",
                            base_amount = "4000.00",
                            source = "table",
                        },
                        new
                        {
                            rate = 12.0m,
                            vat_amount = "240.00",
                            base_amount = "2000.00",
                            source = "table",
                        },
                    },
                },
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        var data = result.Data;
        data.Should().NotBeNull();
        data!.AmountVat.Should().Be(1240.00m);
        data.VatRate.Should().Be(25);
    }

    [Fact]
    public async Task ExtractAsync_ConfidenceCalculation_AveragesFieldConfidencesAndRoundsToFourDecimals()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>(),
                confidence = new Dictionary<string, decimal>
                {
                    ["Field1"] = 0.123456789m,
                    ["Field2"] = 0.987654321m,
                    ["Field3"] = 0.555555555m,
                },
                processing_time_ms = 100.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Confidence.Should().Be(0.5556m);
    }

    [Fact]
    public async Task ExtractAsync_NoConfidenceScores_ReturnsZeroConfidence()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>(),
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Confidence.Should().Be(0m);
    }

    [Fact]
    public async Task ExtractAsync_HttpError500_ReturnsFailureWithErrorMessage()
    {
        // Arrange
        var httpClient = CreateHttpClient(HttpStatusCode.InternalServerError, "Internal server error");
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.Success.Should().BeFalse();
        result.ErrorMessage.Should().Be("OCR API returned InternalServerError");
    }

    [Fact]
    public async Task ExtractAsync_NullResponse_ReturnsFailure()
    {
        // Arrange
        var httpClient = CreateHttpClient(HttpStatusCode.OK, "{}");
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.Success.Should().BeFalse();
        result.ErrorMessage.Should().NotBeNullOrEmpty();
    }

    [Fact]
    public async Task ExtractAsync_NullResult_ReturnsFailureWithMessage()
    {
        // Arrange
        var apiResponse = new
        {
            status = "error",
            message = "Processing failed",
            result = (object?)null,
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.Success.Should().BeFalse();
        result.ErrorMessage.Should().Be("Processing failed");
    }

    [Fact]
    public async Task ExtractAsync_ErrorStatus_ReturnsFailureWithMessage()
    {
        // Arrange
        var apiResponse = new
        {
            status = "error",
            message = "Document format not supported",
            result = new
            {
                document_id = "test",
                success = false,
                fields = new Dictionary<string, string?>(),
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 10.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.Success.Should().BeFalse();
        result.ErrorMessage.Should().Be("Document format not supported");
    }

    [Fact]
    public async Task ExtractAsync_PartialStatus_TreatedAsSuccess()
    {
        // Arrange
        var apiResponse = new
        {
            status = "partial",
            message = "Some fields not detected",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>
                {
                    ["InvoiceNumber"] = "PARTIAL-001",
                },
                confidence = new Dictionary<string, decimal>
                {
                    ["InvoiceNumber"] = 0.75m,
                },
                processing_time_ms = 200.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.Success.Should().BeTrue();
        result.Data.Should().NotBeNull();
        result.Data!.InvoiceNumber.Should().Be("PARTIAL-001");
    }

    [Fact]
    public async Task ExtractAsync_TaskCanceledException_NotUserCancellation_ReturnsTimeoutError()
    {
        // Arrange
        var handler = new TimeoutHttpMessageHandler();
        var httpClient = new HttpClient(handler) { BaseAddress = new Uri("http://localhost") };
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.Success.Should().BeFalse();
        result.ErrorMessage.Should().Be("OCR API request timed out");
    }

    [Fact]
    public async Task ExtractAsync_HttpRequestException_ReturnsConnectionError()
    {
        // Arrange
        var handler = new ConnectionErrorHttpMessageHandler();
        var httpClient = new HttpClient(handler) { BaseAddress = new Uri("http://localhost") };
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.Success.Should().BeFalse();
        result.ErrorMessage.Should().Contain("OCR API connection error");
    }

    [Theory]
    [InlineData("1234.56", 1234.56)]
    [InlineData("1 234,56", 1234.56)]
    [InlineData("1,234.56", 1234.56)]
    [InlineData("1234,56", 1234.56)]
    [InlineData("12345", 12345)]
    [InlineData("0.99", 0.99)]
    public async Task ExtractAsync_DecimalParsing_HandlesVariousFormats(string input, decimal expected)
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>
                {
                    ["Amount"] = input,
                },
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Data.Should().NotBeNull();
        result.Data!.AmountTotal.Should().Be(expected);
    }

    [Theory]
    [InlineData("2024-01-15", 2024, 1, 15)]
    [InlineData("15/01/2024", 2024, 1, 15)]
    [InlineData("15.01.2024", 2024, 1, 15)]
    [InlineData("2024/01/15", 2024, 1, 15)]
    public async Task ExtractAsync_DateParsing_HandlesVariousFormats(string input, int year, int month, int day)
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>
                {
                    ["InvoiceDate"] = input,
                },
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Data.Should().NotBeNull();
        result.Data!.InvoiceDate.Should().Be(new DateTime(year, month, day));
    }

    [Theory]
    [InlineData("test.pdf")]
    [InlineData("invoice.PDF")]
    [InlineData("scan.png")]
    [InlineData("photo.PNG")]
    [InlineData("image.jpg")]
    [InlineData("photo.jpeg")]
    [InlineData("document.JPG")]
    [InlineData("unknown.txt")]
    public async Task ExtractAsync_DifferentFileTypes_ProcessesSuccessfully(string fileName)
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>(),
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, fileName, CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.Success.Should().BeTrue();
    }

    [Fact]
    public async Task ExtractAsync_ErrorsInResult_IncludedInErrorMessage()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>(),
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
                errors = new List<string> { "Low quality image", "Missing page 2" },
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Should().NotBeNull();
        result.ErrorMessage.Should().Be("Low quality image; Missing page 2");
    }

    [Fact]
    public async Task ExtractAsync_DefaultCurrency_SetToSEK()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>(),
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Data.Should().NotBeNull();
        result.Data!.Currency.Should().Be("SEK");
    }

    [Fact]
    public async Task ExtractAsync_CustomCurrency_OverridesDefault()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>
                {
                    ["Currency"] = "EUR",
                },
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
            },
        };

        var httpClient = CreateHttpClient(HttpStatusCode.OK, apiResponse);
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream();

        // Act
        var result = await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        result.Data.Should().NotBeNull();
        result.Data!.Currency.Should().Be("EUR");
    }

    [Fact]
    public async Task ExtractAsync_MultipartFormData_IncludesFileAndExtractLineItemsParameter()
    {
        // Arrange
        var apiResponse = new
        {
            status = "success",
            message = "OK",
            result = new
            {
                document_id = "test",
                success = true,
                fields = new Dictionary<string, string?>(),
                confidence = new Dictionary<string, decimal>(),
                processing_time_ms = 100.0,
            },
        };

        var captureHandler = new CaptureHttpMessageHandler(HttpStatusCode.OK, apiResponse);
        var httpClient = new HttpClient(captureHandler) { BaseAddress = new Uri("http://localhost") };
        var service = new OcrService(httpClient, _loggerMock.Object);
        using var stream = new MemoryStream(Encoding.UTF8.GetBytes("test file content"));

        // Act
        await service.ExtractAsync(stream, "test.pdf", CancellationToken.None);

        // Assert
        captureHandler.CapturedRequest.Should().NotBeNull();
        captureHandler.CapturedRequest!.RequestUri.Should().NotBeNull();
        captureHandler.CapturedRequest.RequestUri!.ToString().Should().EndWith("infer");
        captureHandler.CapturedRequest.Content.Should().NotBeNull();
        captureHandler.CapturedRequest.Content.Should().BeOfType<MultipartFormDataContent>();
    }

    private static HttpClient CreateHttpClient(HttpStatusCode statusCode, object response)
    {
        var json = JsonSerializer.Serialize(response);
        var handler = new MockHttpMessageHandler(statusCode, json);
        return new HttpClient(handler) { BaseAddress = new Uri("http://localhost") };
    }

    private static HttpClient CreateHttpClient(HttpStatusCode statusCode, string responseBody)
    {
        var handler = new MockHttpMessageHandler(statusCode, responseBody);
        return new HttpClient(handler) { BaseAddress = new Uri("http://localhost") };
    }

    private sealed class MockHttpMessageHandler : HttpMessageHandler
    {
        private readonly HttpStatusCode _statusCode;
        private readonly string _responseBody;

        public MockHttpMessageHandler(HttpStatusCode statusCode, string responseBody)
        {
            _statusCode = statusCode;
            _responseBody = responseBody;
        }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            var response = new HttpResponseMessage(_statusCode)
            {
                Content = new StringContent(_responseBody, Encoding.UTF8, "application/json"),
            };
            return Task.FromResult(response);
        }
    }

    private sealed class TimeoutHttpMessageHandler : HttpMessageHandler
    {
        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            throw new TaskCanceledException("Request timed out");
        }
    }

    private sealed class ConnectionErrorHttpMessageHandler : HttpMessageHandler
    {
        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            throw new HttpRequestException("Unable to connect to server");
        }
    }

    private sealed class CaptureHttpMessageHandler : HttpMessageHandler
    {
        private readonly HttpStatusCode _statusCode;
        private readonly string _responseBody;

        public HttpRequestMessage? CapturedRequest { get; private set; }

        public CaptureHttpMessageHandler(HttpStatusCode statusCode, object response)
        {
            _statusCode = statusCode;
            _responseBody = JsonSerializer.Serialize(response);
        }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            CapturedRequest = request;

            var response = new HttpResponseMessage(_statusCode)
            {
                Content = new StringContent(_responseBody, Encoding.UTF8, "application/json"),
            };
            return Task.FromResult(response);
        }
    }
}