import XCTest
import Foundation
@testable import ForgeOffload

final class HashingTests: XCTestCase {

    // xxHash64 official spec vectors (seed 0).
    func testXXHash64SpecVectors() {
        XCTAssertEqual(XXHash64.hash(Data()), 0xEF46_DB37_51D8_E999)
        XCTAssertEqual(XXHash64.hash(Data([0x9E])), 0x4FCE_394C_C88952D8)
        // "Nobody inspects the spammish repetition" — widely published vector.
        let spam = Data("Nobody inspects the spammish repetition".utf8)
        XCTAssertEqual(XXHash64.hash(spam), 0xFBCE_A83C_8A378BF1)
    }

    // Known ASCII vector.
    func testXXHash64Ascii() {
        XCTAssertEqual(XXHash64.hash(Data("xxhash".utf8)), 0x32DD_38952C_4BC720)
    }

    // Streaming hash == whole-buffer hash for multi-MB input crossing block sizes.
    func testStreamingMatchesWhole() {
        var data = Data()
        var seed: UInt64 = 0x12345678
        for _ in 0..<(3 * 1024 * 1024 / 8) {
            seed = seed &* 6364136223846793005 &+ 1442695040888963407
            withUnsafeBytes(of: seed) { data.append(contentsOf: $0) }
        }
        let whole = XXHash64.hash(data)

        var streamer = XXHash64()
        // Uneven chunk sizes to exercise buffering.
        var offset = 0
        let chunks = [1, 31, 32, 33, 4096, 1_000_000]
        var i = 0
        while offset < data.count {
            let size = min(chunks[i % chunks.count], data.count - offset)
            streamer.update(data.subdata(in: offset..<offset + size))
            offset += size
            i += 1
        }
        XCTAssertEqual(streamer.finalize(), whole)
    }

    // Hex formatting: 16 lowercase hex chars, zero-padded.
    func testHexFormat() {
        let h = XXHash64.hexString(XXHash64.hash(Data("xxhash".utf8)))
        XCTAssertEqual(h, "32dd38952c4bc720")
        // Zero-padding for small values.
        XCTAssertEqual(XXHash64.hexString(0xAB), "00000000000000ab")
    }

    // MD5 known vectors (RFC 1321).
    func testMD5Vectors() {
        XCTAssertEqual(MD5.hexString(Data()), "d41d8cd98f00b204e9800998ecf8427e")
        XCTAssertEqual(MD5.hexString(Data("abc".utf8)), "900150983cd24fb0d6963f7d28e17f72")
        XCTAssertEqual(
            MD5.hexString(Data("message digest".utf8)),
            "f96b697d7cb7938d525a2f31aaf161d0")
    }

    // File hashing: chunked reader over a temp file matches in-memory hash.
    func testFileHashing() throws {
        let path = NSTemporaryDirectory() + "forge-hash-\(UUID().uuidString).bin"
        defer { try? FileManager.default.removeItem(atPath: path) }
        var data = Data()
        for i in 0..<100_000 {
            data.append(UInt8(truncatingIfNeeded: i))
        }
        try data.write(to: URL(fileURLWithPath: path))

        let fileHash = try FileHasher.xxh64(path: path)
        XCTAssertEqual(fileHash, XXHash64.hexString(XXHash64.hash(data)))

        let fileMD5 = try FileHasher.md5(path: path)
        XCTAssertEqual(fileMD5, MD5.hexString(data))
    }

    func testMissingFileThrows() {
        XCTAssertThrowsError(try FileHasher.xxh64(path: "/nonexistent/nope.bin"))
    }
}