import XCTest
import os.signpost
@testable import RSSuper

final class FeedFetcherTests: XCTestCase {
    private var fetcher: FeedFetcher!
    private var session: MockURLSession!
    
    override func setUp() {
        super.setUp()
        session = MockURLSession()
        fetcher = FeedFetcher(session: session)
    }
    
    override func tearDown() {
        fetcher = nil
        session = nil
        super.tearDown()
    }
    
    func testFetchFeedSuccess() async throws {
        let url = URL(string: "https://example.com/feed.xml")!
        let feedData = Data(rssSample.utf8)
        
        session.response = (feedData, HTTPURLResponse(url: url, statusCode: 200, httpVersion: "HTTP/1.1", headerFields: nil)!)
        
        let result = try await fetcher.fetchFeed(url: url)
        
        XCTAssertEqual(result.feedData, feedData)
        XCTAssertEqual(result.url, url)
        XCTAssertFalse(result.cached)
    }
    
    func testFetchFeedWithAuthentication() async throws {
        let url = URL(string: "https://example.com/feed.xml")!
        let feedData = Data(rssSample.utf8)
        let credentials = HTTPAuthCredentials(username: "user", password: "pass")
        
        session.response = (feedData, HTTPURLResponse(url: url, statusCode: 200, httpVersion: "HTTP/1.1", headerFields: nil)!)
        
        let result = try await fetcher.fetchFeed(url: url, credentials: credentials)
        
        XCTAssertEqual(result.feedData, feedData)
        let authHeader = session.lastAuthHeader
        XCTAssertTrue(authHeader?.starts(with: "Basic ") ?? false)
    }
    
    func testFetchFeedTimeoutError() async throws {
        let url = URL(string: "https://example.com/feed.xml")!
        
        session.error = URLError(.timedOut)
        
        do {
            _ = try await fetcher.fetchFeed(url: url)
            XCTFail("Expected error to be thrown")
        } catch {
            XCTAssertTrue(true)
        }
    }
    
    func testFetchFeed404Error() async throws {
        let url = URL(string: "https://example.com/feed.xml")!
        
        session.response = (Data(), HTTPURLResponse(url: url, statusCode: 404, httpVersion: "HTTP/1.1", headerFields: nil)!)
        
        do {
            _ = try await fetcher.fetchFeed(url: url)
            XCTFail("Expected error to be thrown")
        } catch {
            XCTAssertTrue(true)
        }
    }
    
    func testFetchFeedAuthenticationError() async throws {
        let url = URL(string: "https://example.com/feed.xml")!
        
        session.response = (Data(), HTTPURLResponse(url: url, statusCode: 401, httpVersion: "HTTP/1.1", headerFields: nil)!)
        
        do {
            _ = try await fetcher.fetchFeed(url: url)
            XCTFail("Expected error to be thrown")
        } catch {
            XCTAssertTrue(true)
        }
    }
    
    func testFetchFeedRetriesOnTimeout() async throws {
        let url = URL(string: "https://example.com/feed.xml")!
        let feedData = Data(rssSample.utf8)
        
        var callCount = 0
        session.onRequest = { [unowned self] in
            callCount += 1
            if callCount < 3 {
                self.session.error = URLError(.timedOut)
            }
        }
        
        session.response = (feedData, HTTPURLResponse(url: url, statusCode: 200, httpVersion: "HTTP/1.1", headerFields: nil)!)
        
        let result = try await fetcher.fetchFeed(url: url)
        
        XCTAssertEqual(result.feedData, feedData)
        XCTAssertEqual(callCount, 3)
    }
    
    func testFetchFeedCaching() async throws {
        let url = URL(string: "https://example.com/feed.xml")!
        let feedData = Data(rssSample.utf8)
        
        session.response = (feedData, HTTPURLResponse(url: url, statusCode: 200, httpVersion: "HTTP/1.1", headerFields: nil)!)
        
        let result1 = try await fetcher.fetchFeed(url: url)
        XCTAssertFalse(result1.cached)
        
        let result2 = try await fetcher.fetchFeed(url: url)
        XCTAssertTrue(result2.cached)
        
        XCTAssertEqual(result1.feedData, result2.feedData)
    }
    
    func testFetchFeedRespectsCacheControlNoStore() async throws {
        let url = URL(string: "https://example.com/feed.xml")!
        let feedData = Data(rssSample.utf8)
        
        session.response = (feedData, HTTPURLResponse(url: url, statusCode: 200, httpVersion: "HTTP/1.1", headerFields: ["Cache-Control": "no-store"])!)
        
        let result1 = try await fetcher.fetchFeed(url: url)
        XCTAssertFalse(result1.cached)
        
        let result2 = try await fetcher.fetchFeed(url: url)
        XCTAssertFalse(result2.cached)
    }
    
    func testHTTPAuthAuthorizationHeader() {
        let credentials = HTTPAuthCredentials(username: "user", password: "pass")
        let authHeader = credentials.authorizationHeader()
        
        XCTAssertEqual(authHeader, "Basic dXNlcjpwYXNz")
    }
    
    func testHTTPAuthAuthorizationHeaderWithSpecialCharacters() {
        let credentials = HTTPAuthCredentials(username: "user@domain", password: "p@ss:w0rd")
        let authHeader = credentials.authorizationHeader()
        
        let expectedData = "user@domain:p@ss:w0rd".data(using: .utf8)!
        let expectedBase64 = expectedData.base64EncodedString()
        XCTAssertEqual(authHeader, "Basic \(expectedBase64)")
    }
}

private let rssSample = """
<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0">
  <channel>
    <title>Test Feed</title>
    <link>https://example.com</link>
    <description>A test feed</description>
    <item>
      <title>Test Item</title>
      <link>https://example.com/item1</link>
      <guid>item-1</guid>
      <description>Test item description</description>
    </item>
  </channel>
</rss>
"""

final class MockURLSession: URLSession {
    var response: (Data, URLResponse)?
    var error: Error?
    var onRequest: (() -> Void)?
    var lastAuthHeader: String?
    
    private var requestCounter = 0
    
    override func dataTask(with request: URLRequest, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask {
        requestCounter += 1
        
        if let auth = request.allHTTPHeaderFields?["Authorization"] {
            lastAuthHeader = auth
        }
        
        onRequest?()
        
        if let error {
            completionHandler(nil, nil, error)
            return MockURLSessionDataTask(error: error)
        }
        
        if let (data, response) = response {
            completionHandler(data, response, nil)
            return MockURLSessionDataTask()
        }
        
        completionHandler(nil, nil, nil)
        return MockURLSessionDataTask()
    }
    
    func reset() {
        requestCounter = 0
        lastAuthHeader = nil
    }
}

final class MockURLSessionDataTask: URLSessionDataTask {
    private let mockError: Error?
    
    init(error: Error? = nil) {
        self.mockError = error
        super.init()
    }
    
    override func resume() {
        // No-op for testing
    }
}