// 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;

// Editing a header must rebuild everything that #includes it. The staleness
// check used to compare an artifact against its own source and its module
// imports only — and the module scanner reads `import` lines, so a header was
// invisible to it. A build after a header-only edit reported nothing to do and
// left objects compiled against the previous contents: the same silent
// mixed-layout binary as issue #27, reached through #include instead.
//
// Each pass below edits exactly one header and asserts both directions — the
// objects that include it are recompiled, the ones that don't are left alone —
// then runs the binary, because "was recompiled" is only interesting if the
// resulting program agrees with itself.

namespace {
    std::int32_t Failures = 0;

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

    // The fixture is mutated during the run, so work on a copy outside the repo.
    fs::path StageFixture() {
        fs::path source = fs::current_path() / "tests" / "IncrementalHeaderChange" / "fixture";
        fs::path staged = fs::temp_directory_path() / "crafter-build-incremental-header-change";
        fs::remove_all(staged);
        fs::copy(source, staged, fs::copy_options::recursive);
        return staged;
    }

    // Swap <name>-grown.h.in in for <name>.h. The replacement text lives in a
    // file rather than a string literal so the header the fixture #includes is
    // the only one under that name, whichever variant is in place.
    void Grow(const fs::path& header) {
        fs::path grown = header.parent_path() / std::format("{}-grown.h.in", header.stem().string());
        fs::copy_file(grown, header, fs::copy_options::overwrite_existing);
        // copy_file carries the source's mtime across, which would leave the
        // rewritten header looking older than the objects built from it.
        fs::last_write_time(header, fs::file_time_type::clock::now());
    }

    std::unique_ptr<Configuration> MakeLib(const fs::path& staged) {
        auto lib = std::make_unique<Configuration>();
        lib->path = staged / "lib";
        lib->name = "widget";
        lib->outputName = "widget";
        lib->target = HostTarget();
        lib->type = ConfigurationType::LibraryStatic;
        std::array<fs::path, 1> ifaces = { "Widget" };
        std::array<fs::path, 1> impls = { "Widget" };
        lib->GetInterfacesAndImplementations(ifaces, impls);
        // cFiles are resolved against the cwd at build time, so spell it out.
        lib->cFiles = { staged / "lib" / "counter" };
        return lib;
    }

    Configuration MakeApp(const fs::path& staged, Configuration* lib) {
        Configuration app;
        app.path = staged;
        app.name = "widget-app";
        app.outputName = "widget-app";
        app.target = HostTarget();
        app.type = ConfigurationType::Executable;
        std::array<fs::path, 0> ifaces = {};
        std::array<fs::path, 1> impls = { "main" };
        app.GetInterfacesAndImplementations(ifaces, impls);
        app.dependencies = { lib };
        return app;
    }

    bool BuildOk(Configuration& app, std::string_view label) {
        // A fresh depResults per pass: the map memoizes each Configuration's
        // build for the duration of one pass, so reusing it would skip the
        // library's second build entirely.
        std::unordered_map<fs::path, std::shared_future<BuildResult>> depResults;
        std::mutex depMutex;
        BuildResult r = Build(app, depResults, depMutex);
        if (!r.result.empty()) {
            std::println(std::cerr, "FAIL: {} build failed: {}", label, r.result);
            ++Failures;
            return false;
        }
        return true;
    }

    // "<sizeof in the consumer> <sizeof in the library> <count> <limit>" — see
    // the fixture's main.cpp.
    void CheckRun(const fs::path& binary, std::string_view expected, std::string_view label) {
        auto r = RunCommandWithTimeout(binary.string(), std::chrono::seconds(30));
        Check(r.exitCode == 0 && !r.crashed && !r.timedOut && r.output == expected, std::format("{}: expected '{}', got '{}' (exit={})", label, expected, r.output, r.exitCode));
    }
}

int main() {
    fs::path staged = StageFixture();
    std::unique_ptr<Configuration> lib = MakeLib(staged);
    Configuration app = MakeApp(staged, lib.get());

    fs::path binary = app.BinDir() / "widget-app";
    // One artifact per compile path a header can reach: the module interface
    // (BMI plus the object made from it), the module's implementation unit, a C
    // source, and the consumer that imports the module.
    fs::path interfacePcm = lib->PcmDir() / "Widget.pcm";
    fs::path interfaceObject = lib->BuildDir() / "Widget.o";
    fs::path libraryObject = lib->BuildDir() / "Widget_impl.o";
    fs::path counterObject = lib->BuildDir() / "counter_source.o";
    fs::path consumerObject = app.BuildDir() / "main_impl.o";

    if (!BuildOk(app, "first pass")) {
        std::println(std::cerr, "{} assertions failed", Failures);
        return 1;
    }
    CheckRun(binary, "8 8 1 5", "first pass");

    auto stamps = [&]() {
        return std::array<fs::file_time_type, 5>{
            fs::last_write_time(interfacePcm),
            fs::last_write_time(interfaceObject),
            fs::last_write_time(libraryObject),
            fs::last_write_time(counterObject),
            fs::last_write_time(consumerObject),
        };
    };

    // Nothing changed: the depfiles must not read as staleness of their own,
    // or every build would recompile the world.
    {
        std::array<fs::file_time_type, 5> before = stamps();
        if (BuildOk(app, "idle pass")) {
            Check(stamps() == before, "an idle rebuild recompiles nothing");
        }
    }

    // A header only the module's implementation unit includes. Its name carries
    // a space, so the depfile spells it escaped.
    {
        std::array<fs::file_time_type, 5> before = stamps();
        Grow(staged / "lib" / "widget count.h");
        if (BuildOk(app, "implementation header pass")) {
            std::array<fs::file_time_type, 5> after = stamps();
            Check(after[2] > before[2], "implementation object is recompiled after a header it includes changes");
            Check(after[0] == before[0], "interface BMI is left alone by a header it does not include");
            Check(after[3] == before[3], "C object is left alone by a header it does not include");
            Check(after[4] == before[4], "consumer object is left alone by a header it does not include");
            CheckRun(binary, "8 8 2 5", "implementation header pass");
        }
    }

    // A header only the C source includes.
    {
        std::array<fs::file_time_type, 5> before = stamps();
        Grow(staged / "lib" / "counter-limit.h");
        if (BuildOk(app, "C header pass")) {
            std::array<fs::file_time_type, 5> after = stamps();
            Check(after[3] > before[3], "C object is recompiled after a header it includes changes");
            Check(after[2] == before[2], "implementation object is left alone by a header it does not include");
            CheckRun(binary, "8 8 2 9", "C header pass");
        }
    }

    // A header the interface unit includes, changing the layout of an exported
    // class: the BMI and everything compiled against it has to follow.
    {
        std::array<fs::file_time_type, 5> before = stamps();
        Grow(staged / "lib" / "widget-layout.h");
        if (BuildOk(app, "interface header pass")) {
            std::array<fs::file_time_type, 5> after = stamps();
            Check(after[0] > before[0], "interface BMI is rebuilt after a header it includes changes");
            Check(after[1] > before[1], "interface object is rebuilt after a header it includes changes");
            Check(after[2] > before[2], "implementation object follows the rebuilt BMI");
            Check(after[4] > before[4], "consumer object follows the rebuilt BMI");
            CheckRun(binary, "16 16 2 9", "interface header pass");
        }
    }

    // An object built before depfiles were emitted at all — an upgrade over an
    // existing build directory — has no record of what it included, so the one
    // safe reading is "rebuild it once".
    {
        std::array<fs::file_time_type, 5> before = stamps();
        fs::remove(lib->BuildDir() / "Widget_impl.o.d");
        if (BuildOk(app, "missing depfile pass")) {
            std::array<fs::file_time_type, 5> after = stamps();
            Check(after[2] > before[2], "an object whose dependency record is missing is rebuilt");
            Check(after[3] == before[3], "the objects that still have one are left alone");
        }
    }

    if (Failures > 0) {
        std::println(std::cerr, "{} assertions failed", Failures);
        return 1;
    }
    return 0;
}