// SPDX-License-Identifier: LGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

import std;
import Crafter.Build;
namespace fs = std::filesystem;
using namespace Crafter;

// Builds that run at the same time share their dependencies' clones in the
// cache: the tests `crafter-build test --jobs=N` builds side by side each
// declare the same ExternalDependency, and two crafter-builds can run at
// once. Fetching a clone that already exists ran `git pull` (and the CMake
// build) in it with nothing to keep a second fetch out, and the second git
// fails on the first one's index.lock. A clone's fetch and build now hold a
// lock of their own.
//
// Eight threads fetch the same tracked branch of a local repository at
// once, a few rounds over, the branch moving between rounds so every pull
// has work to do; every fetch has to succeed. Everything is local;
// XDG_CACHE_HOME keeps the clone out of the real cache.

extern "C" int setenv(const char* name, const char* value, int overwrite);

namespace {
    std::int32_t failures = 0;

    void Check(bool cond, std::string_view msg) {
        if (!cond) {
            std::println(std::cerr, "FAIL: {}", msg);
            ++failures;
        }
    }

    void Git(const fs::path& dir, std::string_view args) {
        const std::string command = std::format("git -C {} {}", ShellQuote(dir.string()), args);
        auto result = RunCommandWithTimeout(command, std::chrono::seconds(60));
        if (result.exitCode != 0) throw std::runtime_error(std::format("{} failed: {}", command, result.output));
    }

    void Commit(const fs::path& repo, std::uint32_t round) {
        std::ofstream(repo / "round.txt", std::ios::binary | std::ios::trunc) << round;
        Git(repo, "add round.txt");
        Git(repo, std::format("commit -q -m round-{}", round));
    }
}

int main() {
    const fs::path scratch = fs::temp_directory_path() / "crafter-build-concurrent-external-fetch";
    fs::remove_all(scratch);
    fs::create_directories(scratch);
    setenv("XDG_CACHE_HOME", (scratch / "cache").c_str(), 1);
    setenv("GIT_CONFIG_NOSYSTEM", "1", 1);
    setenv("GIT_CONFIG_GLOBAL", "/dev/null", 1);
    for (const char* name : { "GIT_AUTHOR_NAME", "GIT_COMMITTER_NAME" }) setenv(name, "crafter-build test", 1);
    for (const char* name : { "GIT_AUTHOR_EMAIL", "GIT_COMMITTER_EMAIL" }) setenv(name, "test@example.invalid", 1);

    const fs::path repo = scratch / "shared";
    fs::create_directories(repo);
    Git(repo, "init -q -b main");
    Commit(repo, 0);
    const GitSource source { .url = std::format("file://{}", repo.string()), .branch = "main" };
    const fs::path clone = GitFetch(source);

    constexpr std::uint32_t threads = 8;
    constexpr std::uint32_t rounds = 4;
    std::vector<std::string> errors;
    std::mutex errorsMutex;
    for (std::uint32_t round = 1; round <= rounds; ++round) {
        Commit(repo, round);
        std::vector<std::jthread> fetchers;
        for (std::uint32_t i = 0; i < threads; ++i) {
            fetchers.emplace_back([&] {
                try {
                    (void)GitFetch(source);
                } catch (const std::exception& e) {
                    std::lock_guard lock(errorsMutex);
                    errors.push_back(e.what());
                }
            });
        }
    }
    Check(errors.empty(), std::format("{} fetches at once, {} rounds: every one succeeds ({} failed{}{})", threads, rounds, errors.size(), errors.empty() ? "" : ", the first: ", errors.empty() ? "" : errors.front()));
    std::ifstream round(clone / "round.txt");
    std::uint32_t last = 0;
    round >> last;
    Check(last == rounds, std::format("and the clone ends at the last round ({})", last));

    std::error_code ec;
    fs::remove_all(scratch, ec);
    if (failures > 0) {
        std::println(std::cerr, "{} assertions failed", failures);
        return 1;
    }
    return 0;
}