#include "nand_settings.h"

#include <chrono>
#include <iostream>
#include <stdexcept>
#include <thread>
#include <vector>

static void Require(bool condition, const char* message = "NAND settings check failed") {
    if (!condition) {
        throw std::runtime_error(message);
    }
}

static std::string ReadBytes(const std::filesystem::path& path) {
    std::ifstream input(path, std::ios::binary);
    return {std::istreambuf_iterator<char>(input), std::istreambuf_iterator<char>()};
}

int main() {
    const auto root = std::filesystem::temp_directory_path() /
        ("wiicomp-nand-settings-" + std::to_string(
            std::chrono::steady_clock::now().time_since_epoch().count()));
    const auto path = root / "title/00000001/00000002/data/setting.txt";
    try {
        using namespace RuntimeNandSettings;
        Require(GenerateSerial(1800000123) == "800000123", "Dolphin timestamp modulo");
        Require(GenerateSerial(1000000001) == "000000001", "Dolphin leading zero padding");
        Require(GenerateSerial(-1).empty(), "Invalid clock must not supply an identity");
        // Golden bytes generated by Dolphin's unmodified SettingsHandler.cpp
        // (upstream 2026-09-06), PAL boot fields and synthetic serial 000000001.
        // Everything after this prefix is raw zero padding to 256 bytes.
        const std::string goldenHex =
            "bba6ac929a0bc96b7eed83d27f33a1e7e73d9b836d8b47c59ee23df6b275baab"
            "bec9d9dead03cc7a3bdafee50c30ab9fb86194e119fe4ba19eff62d5ec3aacb3"
            "b5c9d9e3977eac0943d7ff903120a49ef024eafe1cf77be79cf6229a823aabf0f0";
        std::array<uint8_t, 256> golden{};
        for (size_t i = 0; i < goldenHex.size() / 2; ++i) {
            golden[i] = static_cast<uint8_t>(std::stoul(goldenHex.substr(i * 2, 2), nullptr, 16));
        }
        Require(EncodeNew("000000001") == golden, "Exact Dolphin writer golden fixture");
        std::string error;
        Require(!RuntimeNandSettings::Read(root));
        Require(!std::filesystem::exists(root));
        std::filesystem::create_directories(path.parent_path());
        const auto scratchParent = root / "scratch-collisions";
        std::filesystem::create_directories(scratchParent / ".setting-init-fixed-0");
        const auto sentinel = scratchParent / ".setting-init-fixed-0" / "setting.txt";
        { std::ofstream output(sentinel); output << "another launch owns this"; }
        const auto occupiedFile = scratchParent / ".setting-init-fixed-1";
        { std::ofstream output(occupiedFile); output << "leave this file alone"; }
        std::error_code scratchError;
        const auto claimed = CreateScratchDirectory(scratchParent, "fixed", scratchError);
        Require(claimed && *claimed == scratchParent / ".setting-init-fixed-2" && !scratchError,
                "Retry collisions with both existing directories and files");
        Require(ReadBytes(sentinel) == "another launch owns this" &&
                ReadBytes(occupiedFile) == "leave this file alone", "Never modify another launch's scratch data");
        Require(!CreateScratchDirectory(occupiedFile / "not-a-directory", "fixed", scratchError) && scratchError,
                "Real filesystem errors must fail rather than retry indefinitely");

        // Force all claimants to use the same token; this deterministically
        // exercises the collision path even when host clock precision is high.
        std::array<std::optional<std::filesystem::path>, 16> claims;
        std::vector<std::thread> claimants;
        for (size_t i = 0; i < claims.size(); ++i) {
            claimants.emplace_back([&, i] {
                std::error_code ec;
                claims[i] = CreateScratchDirectory(scratchParent, "shared", ec);
            });
        }
        for (auto& claimant : claimants) claimant.join();
        for (size_t i = 0; i < claims.size(); ++i) {
            Require(claims[i].has_value(), "Every concurrent claimant must acquire a scratch directory");
            for (size_t j = 0; j < i; ++j) {
                Require(claims[i] != claims[j], "Concurrent claimants must own different scratch directories");
            }
        }
        const std::string plain = "AREA=USA\r\n\nCODE=LU\r\nSERNO=987654321\r\nGAME=US\r\n";
        std::array<uint8_t, 256> fixture{};
        for (size_t i = 0; i < fixture.size(); ++i) {
            const unsigned shift = i % 32;
            const uint32_t key = shift == 0 ? 0x73B5DBFAu :
                (0x73B5DBFAu << shift) | (0x73B5DBFAu >> (32 - shift));
            fixture[i] = static_cast<uint8_t>(key) ^ (i < plain.size() ? plain[i] : 0);
        }
        {
            std::ofstream output(path, std::ios::binary);
            output.write(reinterpret_cast<const char*>(fixture.data()), fixture.size());
        }
        auto settings = RuntimeNandSettings::Read(root);
        Require(settings && RuntimeNandSettings::HasIdentity(*settings));
        Require(settings->at("SERNO") == "987654321" && settings->at("CODE") == "LU");
        Require(settings->at("AREA") == "USA" && settings->at("GAME") == "US");
        Require(Ensure(root, error, 1800000123), "Existing imported NAND must work");
        std::array<uint8_t, 256> after{};
        {
            std::ifstream input(path, std::ios::binary);
            input.read(reinterpret_cast<char*>(after.data()), after.size());
        }
        Require(after == fixture);
        for (const auto serial : {"", "000000000", "1234567890", "123ABC789"}) {
            (*settings)["SERNO"] = serial;
            Require(!RuntimeNandSettings::HasIdentity(*settings));
        }
        (*settings)["SERNO"] = "012345678";
        Require(RuntimeNandSettings::HasIdentity(*settings));
        (*settings)["CODE"] = "TOOLONG";
        Require(!RuntimeNandSettings::HasIdentity(*settings));
        (*settings)["CODE"] = "LEH";
        settings->erase("GAME");
        Require(!RuntimeNandSettings::HasIdentity(*settings));
        std::filesystem::resize_file(path, 128);
        Require(!RuntimeNandSettings::Read(root));
        const auto damaged = ReadBytes(path);
        Require(!Ensure(root, error, 1800000123), "Do not replace a truncated identity");
        Require(ReadBytes(path) == damaged, "Damaged file must remain untouched");

        const auto fresh = root / "fresh";
        Require(Ensure(fresh, error, 1800000123), "Missing setting.txt must initialize");
        const auto generated = Read(fresh);
        Require(generated && HasIdentity(*generated), "Generated file must be readable");
        Require(generated->at("SERNO") == "800000123", "Persist Dolphin-generated serial");
        Require(generated->at("CODE") == "LEH" && generated->at("AREA") == "EUR" &&
                generated->at("GAME") == "EU", "PAL first-boot fields");
        Require(generated->at("MODEL") == "RVL-001(EUR)" && generated->at("VIDEO") == "PAL" &&
                generated->at("DVD") == "0" && generated->at("MPCH") == "0x7FFE",
                "Complete Dolphin boot settings");
        const auto firstBoot = ReadBytes(FilePath(fresh));
        Require(firstBoot.size() == 256 && firstBoot.back() == 0, "Dolphin buffer size and raw zero padding");
        Require(Ensure(fresh, error, 1900000999), "Second boot");
        Require(ReadBytes(FilePath(fresh)) == firstBoot, "Second boot must not change any bytes");

        const auto blocked = root / "blocked";
        { std::ofstream output(blocked); output << "file obstructing NAND directory"; }
        Require(!Ensure(blocked, error, 1800000123), "Write failure must not return an ephemeral identity");
        Require(!Ensure(root / "bad-clock", error, -1), "Clock failure must not initialize");

        const auto concurrent = root / "concurrent";
        std::array<bool, 16> results{};
        std::vector<std::thread> workers;
        for (size_t i = 0; i < results.size(); ++i) {
            workers.emplace_back([&, i] {
                std::string detail;
                results[i] = Ensure(concurrent, detail, 1800000001 + i);
            });
        }
        for (auto& worker : workers) worker.join();
        for (const bool result : results) Require(result, "Concurrent boot must read the persisted winner");
        const auto winner = ReadBytes(FilePath(concurrent));
        Require(Read(concurrent) && HasIdentity(*Read(concurrent)), "Concurrent boot must persist valid settings");
        Require(Ensure(concurrent, error, 1900000999), "Boot after concurrent initialization");
        Require(ReadBytes(FilePath(concurrent)) == winner, "Concurrent winner must remain stable");

        // Independently decode as Nintendo does: stop at the first encoded NUL.
        // Exercise serials that force Dolphin's extra-LF escaping, not only
        // values that happen to work with a plain rotating-XOR encoder.
        bool sawExtraLf = false;
        for (int serial = 1; serial <= 10000; ++serial) {
            const auto number = GenerateSerial(1000000000 + serial);
            const auto encoded = EncodeNew(number);
            Require(encoded.has_value(), "Serial encoding must fit");
            std::string decoded;
            for (size_t i = 0; i < encoded->size() && (*encoded)[i] != 0; ++i) {
                const unsigned shift = i % 32;
                const uint32_t key = shift == 0 ? 0x73B5DBFAu :
                    (0x73B5DBFAu << shift) | (0x73B5DBFAu >> (32 - shift));
                decoded += static_cast<char>((*encoded)[i] ^ static_cast<uint8_t>(key));
            }
            Require(decoded.find("SERNO=" + number + "\r\n") != std::string::npos &&
                    decoded.find("GAME=EU\r\n") != std::string::npos,
                    "Encoded NUL must not truncate settings");
            sawExtraLf |= decoded.find("\r\n\n") != std::string::npos;
        }
        Require(sawExtraLf, "Exercise Dolphin LF escape path");
        std::filesystem::remove_all(root);
        std::cout << "NAND settings checks passed\n";
        return 0;
    } catch (const std::exception& error) {
        std::filesystem::remove_all(root);
        std::cerr << error.what() << '\n';
        return 1;
    }
}