//
//  ImageCacheTests.swift
//  PlantGuideTests
//
//  Unit tests for ImageCache - the actor-based image cache service
//  that provides both memory and disk caching for plant images.
//

import XCTest
@testable import PlantGuide

// MARK: - MockURLSession

/// Mock URL session for testing image downloads
final class MockURLSessionForCache: URLSession, @unchecked Sendable {
    var dataToReturn: Data?
    var errorToThrow: Error?
    var downloadCallCount = 0
    var lastRequestedURL: URL?

    override func data(from url: URL) async throws -> (Data, URLResponse) {
        downloadCallCount += 1
        lastRequestedURL = url

        if let error = errorToThrow {
            throw error
        }

        let response = HTTPURLResponse(
            url: url,
            statusCode: 200,
            httpVersion: "HTTP/1.1",
            headerFields: nil
        )!

        return (dataToReturn ?? Data(), response)
    }
}

// MARK: - ImageCacheTests

final class ImageCacheTests: XCTestCase {

    // MARK: - Properties

    private var sut: ImageCache!
    private var mockSession: MockURLSessionForCache!
    private var testDirectory: URL!
    private var fileManager: FileManager!

    // MARK: - Test Lifecycle

    override func setUp() async throws {
        try await super.setUp()

        fileManager = FileManager.default
        mockSession = MockURLSessionForCache()

        // Create a unique test directory for each test
        let tempDir = fileManager.temporaryDirectory
        testDirectory = tempDir.appendingPathComponent("ImageCacheTests_\(UUID().uuidString)")
        try fileManager.createDirectory(at: testDirectory, withIntermediateDirectories: true)

        sut = ImageCache(
            fileManager: fileManager,
            urlSession: mockSession
        )
    }

    override func tearDown() async throws {
        // Clean up test directory
        if let testDirectory = testDirectory, fileManager.fileExists(atPath: testDirectory.path) {
            try? fileManager.removeItem(at: testDirectory)
        }

        sut = nil
        mockSession = nil
        testDirectory = nil
        fileManager = nil

        try await super.tearDown()
    }

    // MARK: - Test Helpers

    private func createTestImageData() -> Data {
        let size = CGSize(width: 100, height: 100)
        let renderer = UIGraphicsImageRenderer(size: size)
        let image = renderer.image { context in
            UIColor.green.setFill()
            context.fill(CGRect(origin: .zero, size: size))
        }
        return image.jpegData(compressionQuality: 0.8)!
    }

    private func createInvalidImageData() -> Data {
        return "This is not valid image data".data(using: .utf8)!
    }

    // MARK: - cacheImage() Tests

    func testCacheImage_WhenDownloadSucceeds_StoresImageInCache() async throws {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // When
        try await sut.cacheImage(from: url, for: plantID)

        // Then
        XCTAssertEqual(mockSession.downloadCallCount, 1)
        XCTAssertEqual(mockSession.lastRequestedURL, url)
    }

    func testCacheImage_WhenDownloadFails_ThrowsDownloadFailed() async {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        mockSession.errorToThrow = URLError(.notConnectedToInternet)

        // When/Then
        do {
            try await sut.cacheImage(from: url, for: plantID)
            XCTFail("Expected downloadFailed error to be thrown")
        } catch let error as ImageCacheError {
            switch error {
            case .downloadFailed:
                break // Expected
            default:
                XCTFail("Expected downloadFailed error, got \(error)")
            }
        } catch {
            XCTFail("Expected ImageCacheError, got \(error)")
        }
    }

    func testCacheImage_WhenInvalidImageData_ThrowsInvalidImageData() async {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        mockSession.dataToReturn = createInvalidImageData()

        // When/Then
        do {
            try await sut.cacheImage(from: url, for: plantID)
            XCTFail("Expected invalidImageData error to be thrown")
        } catch let error as ImageCacheError {
            XCTAssertEqual(error, .invalidImageData)
        } catch {
            XCTFail("Expected ImageCacheError, got \(error)")
        }
    }

    func testCacheImage_WhenAlreadyCached_DoesNotDownloadAgain() async throws {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // When - Cache twice
        try await sut.cacheImage(from: url, for: plantID)
        try await sut.cacheImage(from: url, for: plantID)

        // Then - Should only download once
        XCTAssertEqual(mockSession.downloadCallCount, 1)
    }

    // MARK: - getCachedImage() Tests

    func testGetCachedImage_WhenNotCached_ReturnsNil() async {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!

        // When
        let result = await sut.getCachedImage(for: plantID, url: url)

        // Then
        XCTAssertNil(result)
    }

    func testGetCachedImage_WhenCached_ReturnsImage() async throws {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // Cache the image first
        try await sut.cacheImage(from: url, for: plantID)

        // When
        let result = await sut.getCachedImage(for: plantID, url: url)

        // Then
        XCTAssertNotNil(result)
    }

    func testGetCachedImage_WithDifferentPlantID_ReturnsNil() async throws {
        // Given
        let plantID1 = UUID()
        let plantID2 = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // Cache for plant 1
        try await sut.cacheImage(from: url, for: plantID1)

        // When - Try to get for plant 2
        let result = await sut.getCachedImage(for: plantID2, url: url)

        // Then
        XCTAssertNil(result)
    }

    func testGetCachedImage_WithDifferentURL_ReturnsNil() async throws {
        // Given
        let plantID = UUID()
        let url1 = URL(string: "https://example.com/plant1.jpg")!
        let url2 = URL(string: "https://example.com/plant2.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // Cache url1
        try await sut.cacheImage(from: url1, for: plantID)

        // When - Try to get url2
        let result = await sut.getCachedImage(for: plantID, url: url2)

        // Then
        XCTAssertNil(result)
    }

    func testGetCachedImage_ByURLHash_ReturnsImage() async throws {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        let urlHash = url.absoluteString.sha256Hash
        mockSession.dataToReturn = createTestImageData()

        // Cache the image
        try await sut.cacheImage(from: url, for: plantID)

        // When
        let result = await sut.getCachedImage(for: plantID, urlHash: urlHash)

        // Then
        XCTAssertNotNil(result)
    }

    // MARK: - clearCache() Tests

    func testClearCache_ForSpecificPlant_RemovesOnlyThatPlantsImages() async throws {
        // Given
        let plantID1 = UUID()
        let plantID2 = UUID()
        let url1 = URL(string: "https://example.com/plant1.jpg")!
        let url2 = URL(string: "https://example.com/plant2.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // Cache images for both plants
        try await sut.cacheImage(from: url1, for: plantID1)
        try await sut.cacheImage(from: url2, for: plantID2)

        // When - Clear only plant 1's cache
        await sut.clearCache(for: plantID1)

        // Then - Plant 1's image should be gone, plant 2's should still exist
        // Note: Due to memory cache clearing behavior, we need to re-cache
        // This test verifies the disk cache behavior
        mockSession.downloadCallCount = 0
        try await sut.cacheImage(from: url1, for: plantID1)
        XCTAssertEqual(mockSession.downloadCallCount, 1) // Had to redownload
    }

    func testClearCache_ForPlant_RemovesMultipleImages() async throws {
        // Given
        let plantID = UUID()
        let url1 = URL(string: "https://example.com/plant1.jpg")!
        let url2 = URL(string: "https://example.com/plant2.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // Cache multiple images for the same plant
        try await sut.cacheImage(from: url1, for: plantID)
        try await sut.cacheImage(from: url2, for: plantID)

        // When
        await sut.clearCache(for: plantID)

        // Then - Both images should be gone
        let result1 = await sut.getCachedImage(for: plantID, url: url1)
        let result2 = await sut.getCachedImage(for: plantID, url: url2)
        XCTAssertNil(result1)
        XCTAssertNil(result2)
    }

    // MARK: - clearAllCache() Tests

    func testClearAllCache_RemovesAllImages() async throws {
        // Given
        let plantID1 = UUID()
        let plantID2 = UUID()
        let url1 = URL(string: "https://example.com/plant1.jpg")!
        let url2 = URL(string: "https://example.com/plant2.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // Cache images for multiple plants
        try await sut.cacheImage(from: url1, for: plantID1)
        try await sut.cacheImage(from: url2, for: plantID2)

        // When
        await sut.clearAllCache()

        // Then - All images should be gone
        let result1 = await sut.getCachedImage(for: plantID1, url: url1)
        let result2 = await sut.getCachedImage(for: plantID2, url: url2)
        XCTAssertNil(result1)
        XCTAssertNil(result2)
    }

    // MARK: - getCacheSize() Tests

    func testGetCacheSize_WhenEmpty_ReturnsZero() async {
        // Given - New cache

        // When
        let size = await sut.getCacheSize()

        // Then
        XCTAssertGreaterThanOrEqual(size, 0)
    }

    func testGetCacheSize_AfterCaching_ReturnsNonZero() async throws {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // Cache an image
        try await sut.cacheImage(from: url, for: plantID)

        // When
        let size = await sut.getCacheSize()

        // Then
        XCTAssertGreaterThan(size, 0)
    }

    func testGetCacheSize_AfterClearing_ReturnsZeroOrLess() async throws {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // Cache an image
        try await sut.cacheImage(from: url, for: plantID)

        // Clear cache
        await sut.clearAllCache()

        // When
        let size = await sut.getCacheSize()

        // Then - Size should be back to zero (or minimal)
        XCTAssertGreaterThanOrEqual(size, 0) // At least not negative
    }

    // MARK: - Memory Cache Tests

    func testMemoryCache_HitOnSecondAccess_NoReload() async throws {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // Cache the image
        try await sut.cacheImage(from: url, for: plantID)

        // When - Access twice
        let _ = await sut.getCachedImage(for: plantID, url: url)
        let result2 = await sut.getCachedImage(for: plantID, url: url)

        // Then - Image should still be available
        XCTAssertNotNil(result2)
    }

    // MARK: - Error Description Tests

    func testImageCacheError_InvalidImageData_HasCorrectDescription() {
        // Given
        let error = ImageCacheError.invalidImageData

        // Then
        XCTAssertNotNil(error.errorDescription)
        XCTAssertTrue(error.errorDescription?.contains("invalid") ?? false)
    }

    func testImageCacheError_CompressionFailed_HasCorrectDescription() {
        // Given
        let error = ImageCacheError.compressionFailed

        // Then
        XCTAssertNotNil(error.errorDescription)
        XCTAssertTrue(error.errorDescription?.contains("compress") ?? false)
    }

    func testImageCacheError_WriteFailed_HasCorrectDescription() {
        // Given
        let error = ImageCacheError.writeFailed

        // Then
        XCTAssertNotNil(error.errorDescription)
        XCTAssertTrue(error.errorDescription?.contains("write") ?? false)
    }

    func testImageCacheError_DownloadFailed_HasCorrectDescription() {
        // Given
        let underlyingError = URLError(.notConnectedToInternet)
        let error = ImageCacheError.downloadFailed(underlyingError)

        // Then
        XCTAssertNotNil(error.errorDescription)
        XCTAssertTrue(error.errorDescription?.contains("download") ?? false)
    }

    // MARK: - Protocol Conformance Tests

    func testImageCache_ConformsToProtocol() {
        XCTAssertTrue(sut is ImageCacheProtocol)
    }

    // MARK: - Edge Cases

    func testCacheImage_WithLongURL_Works() async throws {
        // Given
        let plantID = UUID()
        let longPath = String(repeating: "path/", count: 50) + "image.jpg"
        let url = URL(string: "https://example.com/\(longPath)")!
        mockSession.dataToReturn = createTestImageData()

        // When/Then - Should not throw
        try await sut.cacheImage(from: url, for: plantID)
    }

    func testCacheImage_WithSpecialCharactersInURL_Works() async throws {
        // Given
        let plantID = UUID()
        let url = URL(string: "https://example.com/plant%20image%231.jpg")!
        mockSession.dataToReturn = createTestImageData()

        // When/Then - Should not throw
        try await sut.cacheImage(from: url, for: plantID)
    }

    func testCacheImage_MultipleImagesForSamePlant_AllCached() async throws {
        // Given
        let plantID = UUID()
        let urls = (0..<5).map { URL(string: "https://example.com/plant\($0).jpg")! }
        mockSession.dataToReturn = createTestImageData()

        // When - Cache all images
        for url in urls {
            try await sut.cacheImage(from: url, for: plantID)
        }

        // Then - All should be retrievable
        for url in urls {
            let result = await sut.getCachedImage(for: plantID, url: url)
            XCTAssertNotNil(result, "Image for \(url) should be cached")
        }
    }

    func testCacheImage_ConcurrentAccess_HandledCorrectly() async throws {
        // Given
        let plantID = UUID()
        let urls = (0..<10).map { URL(string: "https://example.com/plant\($0).jpg")! }
        mockSession.dataToReturn = createTestImageData()

        // When - Cache concurrently
        await withTaskGroup(of: Void.self) { group in
            for url in urls {
                group.addTask {
                    try? await self.sut.cacheImage(from: url, for: plantID)
                }
            }
        }

        // Then - All should be retrievable (no crashes)
        for url in urls {
            let result = await sut.getCachedImage(for: plantID, url: url)
            XCTAssertNotNil(result)
        }
    }
}