// 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;

// A change to what an executable is linked with has to relink it, even when
// no object changed. The relink check compared modification times only, so a
// link flag added in project.cpp, or a dependency's library moving (an
// ExternalDependency whose options changed is fetched and built into a new
// cache directory, and its -L and rpath follow), left the old binary in
// place: Crafter.Network's tests kept loading the msquic they were first
// linked against.
//
// The test adds an rpath to an executable's link flags, takes it away again,
// and then builds once more with nothing changed, which must not relink.
// The flags come out of sets the dependency threads fill as they finish, so
// the recorded command lists them sorted: in the order they happened to land
// in, an unchanged build could look like a changed one.

namespace {
    std::int32_t failures = 0;

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

    constexpr std::string_view marker = "/crafter-build-link-flags-change-marker";

    BuildResult BuildOnce(const fs::path& project, std::vector<std::string> linkFlags) {
        Configuration app;
        app.path = project;
        app.name = "linked";
        app.outputName = "linked";
        app.target = HostTarget();
        app.type = ConfigurationType::Executable;
        app.linkFlags = std::move(linkFlags);
        std::array<fs::path, 0> ifaces = {};
        std::array<fs::path, 1> impls = { "main" };
        app.GetInterfacesAndImplementations(ifaces, impls);
        std::unordered_map<fs::path, std::shared_future<BuildResult>> depResults;
        std::mutex depMutex;
        BuildResult result = Build(app, depResults, depMutex);
        return result;
    }

    Configuration Plain(const fs::path& project) {
        Configuration app;
        app.path = project;
        app.name = "linked";
        app.outputName = "linked";
        app.target = HostTarget();
        app.type = ConfigurationType::Executable;
        return app;
    }

    fs::path Binary(const fs::path& project) {
        return Plain(project).BinDir() / "linked";
    }

    bool HasMarker(const fs::path& binary) {
        std::ifstream stream(binary, std::ios::binary);
        const std::string bytes((std::istreambuf_iterator<char>(stream)), std::istreambuf_iterator<char>());
        return bytes.find(marker) != std::string::npos;
    }
}

int main() {
    const fs::path project = fs::temp_directory_path() / "crafter-build-link-flags-change";
    fs::remove_all(project);
    fs::copy(fs::current_path() / "tests" / "LinkFlagsChange" / "fixture", project, fs::copy_options::recursive);
    const std::string rpath = std::format("-Wl,-rpath,{}", marker);

    const BuildResult first = BuildOnce(project, {});
    Check(first.result.empty(), std::format("the plain build succeeds: {}", first.result));
    const fs::path binary = Binary(project);
    Check(fs::exists(binary) && !HasMarker(binary), "the plain binary has no rpath to the marker");

    const BuildResult added = BuildOnce(project, { rpath });
    Check(added.result.empty(), std::format("the build with the rpath succeeds: {}", added.result));
    Check(HasMarker(binary), "adding a link flag relinks the binary");

    const BuildResult removed = BuildOnce(project, {});
    Check(removed.result.empty(), std::format("the build without it succeeds: {}", removed.result));
    Check(!HasMarker(binary), "taking it away relinks it again");

    const fs::file_time_type linked = fs::last_write_time(binary);
    const BuildResult again = BuildOnce(project, {});
    Check(again.result.empty() && fs::last_write_time(binary) == linked, "an unchanged build doesn't relink");

    const std::vector<std::string> flags = { "-Wl,-z,now", "-Wl,-O1", "-Wl,--as-needed", "-Wl,-z,relro", "-Wl,--build-id", "-Wl,--hash-style=gnu" };
    const BuildResult many = BuildOnce(project, flags);
    Check(many.result.empty(), std::format("the build with six flags succeeds: {}", many.result));
    std::ifstream recorded(Plain(project).BuildDir() / "linked.link", std::ios::binary);
    const std::string record((std::istreambuf_iterator<char>(recorded)), std::istreambuf_iterator<char>());
    std::vector<std::size_t> at;
    for (const std::string& flag : flags) at.push_back(record.find(std::format(" {}", flag)));
    std::vector<std::string> sorted = flags;
    std::ranges::sort(sorted);
    bool inOrder = !std::ranges::contains(at, std::string::npos);
    for (std::size_t k = 0; inOrder && k + 1 < sorted.size(); ++k) {
        const auto index = [&](const std::string& flag) { return at[static_cast<std::size_t>(std::ranges::find(flags, flag) - flags.begin())]; };
        inOrder = index(sorted[k]) < index(sorted[k + 1]);
    }
    Check(inOrder, std::format("the link record lists the flags sorted: {}", record));

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