// SPDX-License-Identifier: LGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

export module Crafter.Build:Toolchain;
import std;
namespace fs = std::filesystem;

export namespace Crafter {
    // The compiler crafter-build drives and what sits next to it, resolved
    // once per process by GetToolchain(). Every clang++, clang and llvm-ar
    // the tool spawns, the libclang the linter dlopens, the std module
    // source and the default sysroots come from here, so a toolchain
    // installed anywhere other than /usr (the Flatpak carries its own under
    // /app) needs no per-call-site knowledge.
    struct Toolchain {
        // LLVM install prefix. Empty when the tools are bare names on PATH.
        fs::path prefix;
        fs::path clangxx;
        fs::path clang;
        fs::path llvmAr;
        // Where clang-c/Index.h lives when it is not on the default include
        // path; empty otherwise.
        fs::path llvmIncludeDir;
        // The exact libclang to dlopen; nullopt means search the usual names.
        std::optional<fs::path> libclang;
        // A libc++ install other than the compiler's own
        // (CRAFTER_BUILD_LIBCXX_DIR); empty means clang finds its own.
        fs::path libcxxDir;
        // libc++'s std module source for host builds.
        fs::path stdCppm;
        // The _LIBCPP_VERSION of the libc++ stdCppm belongs to (220108 for
        // 22.1.8); 0 when its <__config> could not be read.
        std::int32_t libcxxVersion = 0;
        // Std module sources for libc++ releases other than the toolchain's
        // own, one <major>/std.cppm each, for sysroots that carry libc++
        // without them: <crafter prefix>/share/crafter-build/libc++-modules.
        // Empty when the crafter prefix is unknown; need not exist.
        fs::path stdModulesDir;
        fs::path wasiSysroot;
        // The mingw-w64 install prefix, the directory that holds
        // x86_64-w64-mingw32/ and lib/gcc/x86_64-w64-mingw32/ (/usr for a
        // distro package), absolute and lexically normal. Empty means clang's
        // own discovery, which follows the mingw gcc on PATH. Set by
        // CRAFTER_MINGW_DIR, else the host's /usr when running sandboxed and
        // it has mingw-w64 (the sandbox's own /usr never does). What the
        // mingw target passes as --sysroot is MingwSysroot(), not this:
        // see mingwPrefixIsSystem.
        fs::path mingwPrefix;
        // The prefix holds a Linux system as well as mingw-w64: the host's
        // /usr in the sandbox, or a prefix whose include/ has a C library's
        // features.h, as /usr has. clang searches a mingw sysroot's include/
        // and lib/, so such a prefix is shown to it only through a view of
        // its mingw-w64 parts; any other prefix is the sysroot itself, and
        // Windows libraries installed into its include/ and lib/ are found.
        bool mingwPrefixIsSystem = false;
        // `clang++ -print-target-triple` and the first line of
        // `clang++ --version`; both empty when clang++ could not be run.
        std::string hostTriple;
        std::string clangVersion;
        // Why clang++ could not be resolved or run; empty when it could.
        std::string error;

        // Flags for compiling against libcxxDir; empty without one.
        std::string LibcxxCompileFlags() const;
        // Flags for linking against the libc++ the compiler will use: a -L
        // and an rpath for <prefix>/lib when the prefix is not the system one
        // (clang searches only its per-target runtime directory and the
        // system paths, and a bundled toolchain's libc++.so.1 is on neither
        // the linker's nor the loader's default path), or for an explicit
        // libcxxDir.
        std::string LibcxxLinkFlags() const;
        // Names this toolchain for cache directory names: the clang version
        // followed by a hash of what decides which headers and libraries a
        // PCM is built against. Two toolchains with different keys never
        // share a PCM.
        std::string Key() const;
    };

    // What ResolveToolchain reads, so a test can feed it a staged layout.
    struct ToolchainInputs {
        // The CRAFTER_* variables, present only when set and non-empty.
        std::map<std::string, std::string, std::less<>> env;
        // The <prefix> of <prefix>/share/crafter-build; empty when unknown.
        fs::path crafterPrefix;
        // Where the host's root shows inside a sandbox (/run/host in a
        // Flatpak); empty outside one.
        fs::path hostRoot;
    };
    // Pure path resolution: an env override wins, then a toolchain installed
    // beside crafter-build (<crafterPrefix>/bin/clang++), then bare names on
    // PATH. Never runs a process, so hostTriple and clangVersion stay empty.
    Toolchain ResolveToolchain(const ToolchainInputs& inputs);
    // ResolveToolchain over the real environment plus the two clang probes,
    // computed once and cached. Never throws.
    const Toolchain& GetToolchain();
    // GetToolchain(), or a std::runtime_error carrying its error.
    const Toolchain& RequireToolchain();
    // Makes, in the first of `parents` that can hold one, a directory that
    // shows clang only the mingw-w64 parts of `prefix`: links named
    // x86_64-w64-mingw32, lib/gcc and lib64/gcc to the same paths under
    // `prefix`, at <parent>/mingw-sysroot/<hash of prefix>, and returns it.
    // A view already there is reused; one another process makes at the same
    // moment is as good as one made here. Throws when no parent can hold
    // one, with the reason for each.
    fs::path MakeMingwSysroot(const fs::path& prefix, std::span<const fs::path> parents);
    // The --sysroot of every compile, link and CMake configure for the mingw
    // target, settled on the first call of a process: empty without a
    // mingwPrefix, the prefix itself for one that holds mingw-w64 alone, and
    // for a system prefix the view MakeMingwSysroot makes in crafter-build's
    // cache, or in $XDG_RUNTIME_DIR/crafter.build when the cache's
    // filesystem takes no symbolic links. A system prefix cannot be the
    // sysroot: clang takes a mingw sysroot for a tree that holds mingw-w64
    // alone and searches its include/ and lib/ as well, which for /usr are
    // the Linux system's own. A Windows build then saw glibc's headers, and
    // libstdc++, finding <sys/single_threaded.h>, had shared_ptr read
    // __libc_single_threaded, which nothing on Windows defines (issue #43).
    // Throws when the view cannot be made.
    const fs::path& MingwSysroot();
    // `text` with every path into the view MingwSysroot() made written as
    // the same path into the prefix it shows, so that compiler messages name
    // a header where the user installed it rather than in a hashed cache
    // directory; `text` unchanged when no view was made.
    std::string MingwViewToPrefix(std::string text);
    // _LIBCPP_VERSION as the <__config> in `includeDir` (an include/c++/v1)
    // defines it, XXYYZZ; 0 when the file is missing or has no such line.
    std::int32_t LibcxxVersion(const fs::path& includeDir);
    // "23.1.2" for 230102.
    std::string LibcxxVersionString(std::int32_t version);

    struct StdModuleSource {
        fs::path stdCppm;
        // One line saying why no source fits; empty when stdCppm is set.
        std::string error;
    };
    // The std module source to precompile for a native (non-wasm) build
    // against `sysroot`. The module source is a list of using-declarations
    // for names the headers of the same libc++ release declare, so one from
    // another release fails on every name that release added or dropped. In
    // order: the sysroot's own <sysroot>/usr/share/libc++/v1/std.cppm, the
    // toolchain's when both are the same major release, the copy for the
    // sysroot's release under toolchain.stdModulesDir. Not every distro
    // packages the module sources with its libc++ (Alpine does not), which
    // is why the sysroot's own copy cannot be the only answer. When the
    // sysroot's release cannot be read, the toolchain's source is returned
    // and the compile is the check.
    StdModuleSource SysrootStdModule(const Toolchain& toolchain, const fs::path& sysroot);
    // The version baked in when crafter-build was built; "0.0.0-dev" for a
    // build that was given none.
    std::string_view CrafterBuildVersion();
}