// 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 compiler warning must not fail the build. Success used to be inferred from
// whether the command printed anything, and a warning is printing something —
// so a translation unit that warns failed the build the moment it was compiled
// and passed on every run after that, because warnings are only emitted when
// something actually recompiles. Same source, opposite verdicts, decided by
// whether an object file happened to be up to date: it read as a flaky test,
// and a cold CI checkout turned every latent warning in a project into a wall
// of unrelated failures.
//
// The fixture puts a #warning in each kind of source the build knows how to
// compile — module interface, module implementation, C, consumer — and a
// linker warning on top, then asserts the build succeeds cold, succeeds when
// there is nothing to do, and succeeds again after each source is touched back
// into staleness. The last pass introduces a real error, because "never fails"
// would satisfy everything above just as well.

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, and every assertion here depends
    // on units compiling for the first time, so work on a fresh copy outside
    // the repo rather than against whatever an earlier run left behind.
    fs::path StageFixture() {
        fs::path source = fs::current_path() / "tests" / "CompilerWarning" / "fixture";
        fs::path staged = fs::temp_directory_path() / "crafter-build-compiler-warning";
        fs::remove_all(staged);
        fs::copy(source, staged, fs::copy_options::recursive);
        return staged;
    }

    std::unique_ptr<Configuration> MakeLib(const fs::path& staged) {
        auto lib = std::make_unique<Configuration>();
        lib->path = staged / "lib";
        lib->name = "noisy-widget";
        lib->outputName = "noisy-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 = "noisy-app";
        app.outputName = "noisy-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 };
        // The link step reads a command's output the same way a compile does,
        // so cover it too: an unknown -z value makes ld.lld warn and exit 0.
        // GNU-style only — lld-link spells its options differently — so the
        // link case rides along on hosts that use it and is skipped elsewhere.
        if (!app.target.contains("windows")) {
            app.linkFlags = { "-Wl,-z,crafter-build-nonexistent-z-value" };
        }
        return app;
    }

    BuildResult BuildOnce(Configuration& app) {
        // 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 rebuild entirely.
        std::unordered_map<fs::path, std::shared_future<BuildResult>> depResults;
        std::mutex depMutex;
        return Build(app, depResults, depMutex);
    }

    bool BuildOk(Configuration& app, std::string_view label) {
        BuildResult r = BuildOnce(app);
        if (!r.result.empty()) {
            std::println(std::cerr, "FAIL: {} build failed: {}", label, r.result);
            ++Failures;
            return false;
        }
        return true;
    }

    void CheckRun(const fs::path& binary, std::string_view label) {
        auto r = RunCommandWithTimeout(binary.string(), std::chrono::seconds(30));
        Check(r.exitCode == 0 && !r.crashed && !r.timedOut && r.output == "42 7", std::format("{}: expected '42 7', got '{}' (exit={})", label, r.output, r.exitCode));
    }

    void Touch(const fs::path& source) {
        fs::last_write_time(source, fs::file_time_type::clock::now());
    }
}

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

    // Cold: every unit compiles, so every #warning in the fixture is emitted
    // and the linker warns as well. This is the pass that used to fail.
    if (!BuildOk(app, "cold")) {
        std::println(std::cerr, "{} assertions failed", Failures);
        return 1;
    }
    CheckRun(binary, "cold");

    // Nothing to recompile, so nothing warns. Same sources as the pass above,
    // and the verdict has to match it.
    if (BuildOk(app, "idle")) {
        CheckRun(binary, "idle");
    }

    // Back into staleness one source at a time: whichever compile path a
    // warning comes out of, it stays non-fatal.
    for (auto [source, label] : std::initializer_list<std::pair<fs::path, std::string_view>>{
             { staged / "lib" / "Widget.cppm", "interface unit" },
             { staged / "lib" / "Widget.cpp",  "implementation unit" },
             { staged / "lib" / "counter.c",   "C source" },
             { staged / "main.cpp",            "consumer" },
         }) {
        Touch(source);
        if (BuildOk(app, label)) {
            CheckRun(binary, label);
        }
    }

    // The other direction, last because it leaves the fixture broken: a real
    // error still has to fail, and still has to say what went wrong.
    {
        std::ofstream broken(staged / "main.cpp", std::ios::binary | std::ios::trunc);
        broken << "int main() { return NotDeclaredAnywhere(); }\n";
        broken.close();
        Touch(staged / "main.cpp");

        BuildResult r = BuildOnce(app);
        Check(!r.result.empty(), "a source that fails to compile fails the build");
        Check(r.result.contains("error:"), std::format("the failure reports the compiler's diagnostic, got '{}'", r.result));
    }

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