// 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 sysroot build precompiles the std module from a module source that has to
// belong to the libc++ release whose headers the sysroot carries. Not every
// distro packages that source with its libc++ (Alpine does not), and the
// fallback used to be the toolchain's own copy whatever its release: with a
// libc++ 22 toolchain and a libc++ 23 sysroot the build died on a page of "no
// member named 'runtime_format' in namespace 'std'" that named neither
// release nor what to do about it.
//
// Staged, compiler-free layouts cover the order SysrootStdModule picks in: the
// sysroot's own source, the toolchain's for the same major release, the copy
// crafter-build ships for another release, and otherwise one line naming both
// releases and where the matching source belongs. The last block drives
// Build() against a sysroot nothing matches and expects that line back in
// place of compiler output.
namespace {
    std::int32_t Failures = 0;

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

    void Write(const fs::path& file, std::string_view content) {
        fs::create_directories(file.parent_path());
        std::ofstream(file) << content;
    }

    // What libc++ installs as include/c++/v1/__config, reduced to the line
    // that states the release.
    void StageHeaders(const fs::path& includeDir, std::int32_t version) {
        Write(includeDir / "__config", std::format("#ifndef _LIBCPP___CONFIG\n#  define _LIBCPP___CONFIG\n#  define _LIBCPP_VERSION {}\n#endif\n", version));
    }

    fs::path StageSysroot(const fs::path& sysroot, std::int32_t version) {
        StageHeaders(sysroot / "usr" / "include" / "c++" / "v1", version);
        return sysroot;
    }
}

int main() {
    const fs::path scratch = fs::temp_directory_path() / "crafter-build-sysroot-std-module";
    std::error_code ec;
    fs::remove_all(scratch, ec);
    fs::create_directories(scratch);

    {
        StageHeaders(scratch / "headers", 230102);
        Check(LibcxxVersion(scratch / "headers") == 230102, "the release is read from __config");
        Check(LibcxxVersion(scratch / "no-such-dir") == 0, "missing headers read as an unknown release");
        Write(scratch / "other" / "__config", "#define _LIBCPP_ABI_VERSION 1\n");
        Check(LibcxxVersion(scratch / "other") == 0, "a __config without the version line reads as an unknown release");
        Check(LibcxxVersionString(230102) == "23.1.2" && LibcxxVersionString(220108) == "22.1.8", "XXYYZZ is spelled as a dotted release");
    }

    // A toolchain on libc++ 22.1.8 that also ships the sources for 23.
    Toolchain tc;
    tc.stdCppm = scratch / "toolchain" / "share" / "libc++" / "v1" / "std.cppm";
    tc.libcxxVersion = 220108;
    tc.stdModulesDir = scratch / "shipped";
    Write(tc.stdCppm, "");
    Write(tc.stdModulesDir / "23" / "std.cppm", "");

    {
        // The sysroot's own source matches its headers by construction, so
        // it wins whatever the releases are.
        const fs::path sysroot = StageSysroot(scratch / "sysroot-own", 240100);
        const fs::path own = sysroot / "usr" / "share" / "libc++" / "v1" / "std.cppm";
        Write(own, "");
        StdModuleSource source = SysrootStdModule(tc, sysroot);
        Check(source.error.empty() && source.stdCppm == own, "a sysroot that ships the module source uses its own");
    }
    {
        const fs::path sysroot = StageSysroot(scratch / "sysroot-same-major", 220103);
        StdModuleSource source = SysrootStdModule(tc, sysroot);
        Check(source.error.empty() && source.stdCppm == tc.stdCppm, "a point release of the toolchain's libc++ uses the toolchain's source");
    }
    {
        // The reported case: libc++ 23 headers, a libc++ 22 toolchain.
        const fs::path sysroot = StageSysroot(scratch / "sysroot-next-major", 230102);
        StdModuleSource source = SysrootStdModule(tc, sysroot);
        Check(source.error.empty() && source.stdCppm == tc.stdModulesDir / "23" / "std.cppm", "another release uses the source shipped for it, not the toolchain's");
    }
    {
        const fs::path sysroot = StageSysroot(scratch / "sysroot-unshipped", 210108);
        StdModuleSource source = SysrootStdModule(tc, sysroot);
        Check(source.stdCppm.empty() && !source.error.empty(), "a release nothing was shipped for is an error, not a compile against the wrong source");
        Check(source.error.contains("21.1.8") && source.error.contains("22.1.8"), std::format("the error names both releases, got '{}'", source.error));
        Check(source.error.contains((sysroot / "usr" / "share" / "libc++" / "v1").string()), std::format("the error says where the matching source belongs, got '{}'", source.error));
        Check(!source.error.contains('\n'), "the error is one line");
    }
    {
        const fs::path sysroot = scratch / "sysroot-no-libcxx";
        fs::create_directories(sysroot / "usr" / "include");
        StdModuleSource source = SysrootStdModule(tc, sysroot);
        Check(source.stdCppm.empty() && source.error.contains("no libc++ headers"), std::format("a sysroot without libc++ says so, got '{}'", source.error));
    }
    {
        // Nothing to compare when either release is unknown: the toolchain's
        // source goes to the compiler, as it did before releases were read.
        const fs::path sysroot = scratch / "sysroot-unreadable";
        Write(sysroot / "usr" / "include" / "c++" / "v1" / "__config", "#define _LIBCPP_ABI_VERSION 1\n");
        Check(SysrootStdModule(tc, sysroot).stdCppm == tc.stdCppm, "an unreadable sysroot release falls back to the toolchain's source");
        Toolchain unknown = tc;
        unknown.libcxxVersion = 0;
        unknown.stdModulesDir.clear();
        Check(SysrootStdModule(unknown, StageSysroot(scratch / "sysroot-vs-unknown", 230102)).stdCppm == tc.stdCppm, "an unreadable toolchain release falls back to the toolchain's source");
    }
    {
        Toolchain bare;
        bare.stdCppm = scratch / "nowhere" / "std.cppm";
        bare.libcxxVersion = 220108;
        StdModuleSource source = SysrootStdModule(bare, StageSysroot(scratch / "sysroot-vs-bare", 220108));
        Check(source.stdCppm.empty() && source.error.contains("no std module source"), std::format("a toolchain without a module source is an error too, got '{}'", source.error));
    }

    {
        // End to end with the real toolchain: a sysroot on a libc++ release
        // that does not exist fails the build with the one-line explanation
        // before clang is run. The target is the host's so the std PCM cache
        // directory is the one every other test already uses.
        const Toolchain& real = GetToolchain();
        Check(real.libcxxVersion != 0, "the running toolchain's libc++ release is read from its headers");

        const fs::path project = scratch / "project";
        Write(project / "main.cpp", "int main() { return 0; }\n");
        Configuration app;
        app.path = project;
        app.name = "sysroot-std-module";
        app.outputName = "sysroot-std-module";
        app.target = HostTarget();
        app.type = ConfigurationType::Executable;
        app.sysroot = StageSysroot(scratch / "sysroot-future", 990000).string();
        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 r = Build(app, depResults, depMutex);
        Check(r.result.contains("libc++ 99.0.0"), std::format("the build fails naming the sysroot's release, got '{}'", r.result));
        Check(r.result.contains(LibcxxVersionString(real.libcxxVersion)), std::format("the build fails naming the toolchain's release, got '{}'", r.result));
        Check(!r.result.contains('\n') && !r.result.contains("error:"), std::format("the failure is one line, not compiler output, got '{}'", r.result));
    }

    return Failures == 0 ? 0 : 1;
}