// 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;

// Compile a tiny GLSL fragment shader directly via the Shader API. Verifies
// the SPIR-V output lands in the target dir and starts with the SPIR-V magic
// number, without dragging in the full Build() pipeline. The second half
// registers one source twice, with and without defines, and checks that the
// variant gets its own output, its own staleness and the other #ifdef branch
// (tests/ShaderVariantBuild drives the same thing through Build()).
int main() {
    fs::path src = fs::current_path() / "tests" / "ShaderCompile" / "fixture" / "triangle.frag";
    if (!fs::exists(src)) {
        std::println(std::cerr, "fixture missing: {}", src.string());
        return 1;
    }

    fs::path outDir = fs::temp_directory_path() / "crafter-build-shader-test";
    std::error_code ec;
    fs::remove_all(outDir, ec);
    fs::create_directories(outDir);

    Shader shader(fs::path(src), "main", ShaderType::Fragment);

    std::array<fs::path, 0> includeDirs = {};
    std::string err = shader.Compile(outDir, includeDirs);
    if (!err.empty()) {
        std::println(std::cerr, "shader compile failed: {}", err);
        return 1;
    }

    fs::path spv = outDir / "triangle.spv";
    if (!fs::exists(spv)) {
        std::println(std::cerr, "spv not produced at {}", spv.string());
        return 1;
    }

    // SPIR-V binaries start with the magic number 0x07230203 (little-endian
    // when written by glslang on x86). Read the first four bytes to confirm
    // the produced file is real SPIR-V, not a fluke empty file.
    std::ifstream in(spv, std::ios::binary);
    std::uint32_t magic = 0;
    in.read(reinterpret_cast<char*>(&magic), sizeof(magic));
    if (!in || magic != 0x07230203u) {
        std::println(std::cerr, "spv has wrong magic: 0x{:08x}", magic);
        return 1;
    }

    // Compiling again should be a no-op since the source isn't newer.
    if (!shader.Check(outDir)) {
        std::println(std::cerr, "Shader::Check returned false on an up-to-date spv");
        return 1;
    }

    // One source registered twice: the second entry carries defines and a
    // variant name. It must land in its own file instead of overwriting the
    // first, and it must take the other #ifdef branch. Crafter.Graphics ships
    // each UI shader in a descriptor-heap and a descriptor-set flavour this
    // way; if the variant were dropped from the output name, whichever compile
    // finished last would silently win.
    fs::path variantSrc = fs::current_path() / "tests" / "ShaderCompile" / "fixture" / "variant.frag";
    Shader plain(fs::path(variantSrc), "main", ShaderType::Fragment);
    Shader red(fs::path(variantSrc), "main", ShaderType::Fragment);
    red.defines = {"VARIANT_RED", "VARIANT_ALPHA=0.5"};
    red.variant = "red";

    if (plain.OutputName() != "variant.spv" || red.OutputName() != "variant.red.spv") {
        std::println(std::cerr, "unexpected output names: {} and {}", plain.OutputName().string(), red.OutputName().string());
        return 1;
    }
    for (const Shader* each : {&plain, &red}) {
        // Staleness is per output, not per source: while only variant.spv
        // exists, the variant is still due. A Check() that ignored the
        // variant would call it up to date here, and Build() would then
        // never compile a variant added to an already built project.
        if (each == &red && red.Check(outDir)) {
            std::println(std::cerr, "Shader::Check called the variant up to date before it was ever compiled");
            return 1;
        }
        std::string variantErr = each->Compile(outDir, includeDirs);
        if (!variantErr.empty()) {
            std::println(std::cerr, "variant shader compile failed: {}", variantErr);
            return 1;
        }
        if (!each->Check(outDir)) {
            std::println(std::cerr, "Shader::Check returned false for {}", each->OutputName().string());
            return 1;
        }
    }

    // Malformed defines and variants are refused by name. Left to glslang, an
    // empty macro name surfaces as "-1:<line>" with no file, and a variant
    // with a separator as a failed open after the whole compile.
    for (const char* bad : {"", "=1", "A\nB"}) {
        Shader malformed(fs::path(variantSrc), "main", ShaderType::Fragment);
        malformed.defines = {bad};
        malformed.variant = "malformed";
        if (!malformed.Compile(outDir, includeDirs).contains("invalid shader define")) {
            std::println(std::cerr, "a malformed define was not rejected by name");
            return 1;
        }
    }
    Shader nested(fs::path(variantSrc), "main", ShaderType::Fragment);
    nested.variant = "sub/red";
    if (!nested.Compile(outDir, includeDirs).contains("path separator")) {
        std::println(std::cerr, "a variant with a path separator was not rejected by name");
        return 1;
    }

    auto readAll = [](const fs::path& file) {
        std::ifstream stream(file, std::ios::binary);
        return std::string(std::istreambuf_iterator<char>(stream), std::istreambuf_iterator<char>());
    };
    std::string plainSpv = readAll(outDir / "variant.spv");
    std::string redSpv = readAll(outDir / "variant.red.spv");
    if (plainSpv.empty() || redSpv.empty()) {
        std::println(std::cerr, "a variant output is missing or empty");
        return 1;
    }
    if (plainSpv == redSpv) {
        std::println(std::cerr, "both variants compiled to the same SPIR-V: the defines did not reach the preprocessor");
        return 1;
    }
    return 0;
}