// 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 shader's output is stale when anything that went into it changed, not
// only its own source. Check() used to compare the .spv against the source's
// mtime alone, so:
//   - editing a file the shader #includes left the .spv built against the old
//     contents, the GLSL twin of IncrementalHeaderChange;
//   - changing an entry's defines without touching the source did too.
// Each pass changes one thing and checks both directions: the shader it
// reaches is recompiled, to new contents, and the shader that includes
// nothing is left alone. A build with nothing changed compiles nothing.
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 edited between passes, so work on a copy outside the repo.
    fs::path StageFixture() {
        fs::path source = fs::current_path() / "tests" / "ShaderIncludeChange" / "fixture";
        fs::path staged = fs::temp_directory_path() / "crafter-build-shader-include-change";
        fs::remove_all(staged);
        fs::copy(source, staged, fs::copy_options::recursive);
        return staged;
    }

    Configuration MakeApp(const fs::path& staged) {
        Configuration app;
        app.path = staged;
        app.name = "lit";
        app.outputName = "lit";
        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.shaders.emplace_back(staged / "lit.frag", std::string("main"), ShaderType::Fragment);
        app.shaders.emplace_back(staged / "plain.frag", std::string("main"), ShaderType::Fragment);
        // Puts include/ on the shaders' #include path.
        app.buildFiles = { staged / "include" / "palette.glsl" };
        return app;
    }

    bool BuildOk(Configuration& app, std::string_view label) {
        // A fresh depResults per pass: the map memoizes a Configuration's
        // build for the duration of one pass.
        std::unordered_map<fs::path, std::shared_future<BuildResult>> depResults;
        std::mutex depMutex;
        BuildResult r = Build(app, depResults, depMutex);
        Check(r.result.empty(), std::format("{} builds: {}", label, r.result));
        return r.result.empty();
    }

    std::string ReadAll(const fs::path& file) {
        std::ifstream stream(file, std::ios::binary);
        return std::string(std::istreambuf_iterator<char>(stream), std::istreambuf_iterator<char>());
    }
}

int main() {
    const fs::path staged = StageFixture();
    Configuration app = MakeApp(staged);
    const fs::path lit = app.BinDir() / "lit.spv";
    const fs::path plain = app.BinDir() / "plain.spv";
    const fs::path palette = staged / "include" / "palette.glsl";

    // Pass 1: everything from scratch.
    if (!BuildOk(app, "the first pass")) return 1;
    Check(fs::exists(lit) && fs::exists(plain), "both shaders are in the bin dir");
    const fs::file_time_type plainBuilt = fs::last_write_time(plain);
    const std::string green = ReadAll(lit);

    // Pass 2: nothing changed.
    fs::file_time_type litBuilt = fs::last_write_time(lit);
    BuildOk(app, "an unchanged project");
    Check(fs::last_write_time(lit) == litBuilt && fs::last_write_time(plain) == plainBuilt, "with nothing changed, no shader is recompiled");

    // Pass 3: the included file changes. Dated just after the output it must
    // outdate, so the rebuilt output is newer than it again.
    {
        std::ofstream out(palette, std::ios::trunc);
        out << "const vec4 kTint = vec4(1.0, 0.0, 0.0, 1.0);\n";
    }
    fs::last_write_time(palette, litBuilt + std::chrono::milliseconds(1));
    BuildOk(app, "an edited include");
    const std::string red = ReadAll(lit);
    Check(fs::last_write_time(lit) > litBuilt && red != green, "editing an included file recompiles the shader that includes it, to new contents");
    Check(fs::last_write_time(plain) == plainBuilt, "and leaves the shader that includes nothing alone");

    // Pass 4: the entry's defines change, no file does.
    app.shaders[0].defines = { "LIT_DIM" };
    litBuilt = fs::last_write_time(lit);
    BuildOk(app, "a new define");
    const std::string dim = ReadAll(lit);
    Check(fs::last_write_time(lit) > litBuilt && dim != red, "a define added to the entry recompiles it, taking the #ifdef branch");
    Check(fs::last_write_time(plain) == plainBuilt, "and leaves the other entry alone");

    // Pass 5: and back.
    app.shaders[0].defines = {};
    BuildOk(app, "the define taken out");
    Check(ReadAll(lit) == red, "taking the define out again recompiles it as it was");

    // Pass 6: nothing changed again; what the passes above recorded holds.
    litBuilt = fs::last_write_time(lit);
    BuildOk(app, "an unchanged project, again");
    Check(fs::last_write_time(lit) == litBuilt && fs::last_write_time(plain) == plainBuilt, "with nothing changed since, no shader is recompiled");

    std::error_code ec;
    fs::remove_all(staged, ec);

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