SWCompression/Tests/TestSWCompression/ZlibTests.swift

// Copyright (c) 2026 Timofey Solomko
// Licensed under MIT License
//
// See LICENSE for license information

import XCTest
import SWCompression

class ZlibTests: XCTestCase {

    private static let testType: String = "zlib"

    func testZlib() throws {
        let testName = "test"

        let testData = try Constants.data(forTest: testName, withType: ZlibTests.testType)
        let testZlibHeader = try ZlibHeader(archive: testData)

        XCTAssertEqual(testZlibHeader.compressionMethod, .deflate)
        XCTAssertEqual(testZlibHeader.compressionLevel, .defaultAlgorithm)
        XCTAssertEqual(testZlibHeader.windowSize, 32768)
    }

    func testZlibFull() throws {
        let testData = try Constants.data(forTest: "random_file", withType: ZlibTests.testType)
        let decompressedData = try ZlibArchive.unarchive(archive: testData)

        let answerData = try Constants.data(forAnswer: "test9")
        XCTAssertEqual(decompressedData, answerData)
    }

    func testCreateZlib() throws {
        let testData = try Constants.data(forAnswer: "test9")
        let archiveData = ZlibArchive.archive(data: testData)
        let reextractedData = try ZlibArchive.unarchive(archive: archiveData)

        XCTAssertEqual(testData, reextractedData)
    }

    func testZlibEmpty() throws {
        let testData = try Constants.data(forTest: "test_empty", withType: ZlibTests.testType)
        XCTAssertEqual(try ZlibArchive.unarchive(archive: testData), Data())
    }

    func testBadFile_short() {
        XCTAssertThrowsError(try ZlibArchive.unarchive(archive: Data([0x78])))
        XCTAssertThrowsError(try ZlibHeader(archive: Data([0x78])))
    }

    func testBadFile_invalid() throws {
        let testData = try Constants.data(forAnswer: "test6")
        XCTAssertThrowsError(try ZlibArchive.unarchive(archive: testData))
    }

    func testEmptyData() throws {
        XCTAssertThrowsError(try ZlibArchive.unarchive(archive: Data()))
    }

    func testChecksumMismatch() throws {
        // Here we test that an error for checksum mismatch is thrown correctly and its associated value contains
        // expected data. We do this by programmatically adjusting the input: we change one of the bytes for the checkum,
        // which makes it incorrect.
        var testData = try Constants.data(forTest: "random_file", withType: ZlibTests.testType)
        // Here we modify the stored value of adler32.
        testData[10249] &+= 1
        var thrownError: Error? = nil
        XCTAssertThrowsError(try ZlibArchive.unarchive(archive: testData)) { thrownError = $0 }
        XCTAssertTrue(thrownError is ZlibError, "Unexpected error type: \(type(of: thrownError))")
        if case let .some(.wrongAdler32(decompressedData)) = thrownError as? ZlibError {
            let answerData = try Constants.data(forAnswer: "test9")
            XCTAssertEqual(decompressedData, answerData)
        } else {
            XCTFail("Unexpected error: \(String(describing: thrownError))")
        }
    }

    func testZlibTruncation() throws {
        for testName in ["test", "random_file", "test_empty"] {
            let testData = try Constants.data(forTest: testName, withType: ZlibTests.testType)
            for _ in 0..<100 {
                let truncationIndex = Int.random(in: (testData.startIndex + 1)..<testData.endIndex)
                _ = try? ZlibArchive.unarchive(archive: testData[testData.startIndex..<truncationIndex])
            }
        }
    }

}