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

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

export namespace Crafter {
    struct Configuration;

    struct GitSource {
        std::string url;
        std::string branch;
        std::string commit;
    };

    enum class ExternalBuilder {
        None,
        CMake,
    };

    struct ExternalDependency {
        std::string name;
        GitSource source;
        ExternalBuilder builder = ExternalBuilder::None;
        std::vector<std::string> options;
        std::vector<fs::path> includeDirs;
        // Extra library search paths (each becomes a -L flag), interpreted
        // relative to the CMake build dir. Currently only honoured for
        // ExternalBuilder::CMake. The CMake builder always adds its
        // top-level build dir as a -L; libDirs is for projects (msquic,
        // others) whose CMakeLists set LIBRARY_OUTPUT_DIRECTORY to a subdir
        // of the build tree.
        std::vector<fs::path> libDirs;
        std::vector<std::string> libs;
    };

    struct ExternalBuildResult {
        std::vector<std::string> compileFlags;
        std::vector<std::string> linkFlags;
        fs::file_time_type latestArtifact = fs::file_time_type::min();
    };

    // Where this dependency's clone lives in the cache. A pure function of the
    // declaration and target — BuildExternal derives its own working directory
    // through this, so a caller that only needs to know where the headers ended
    // up cannot drift from where they actually are.
    fs::path ExternalCloneDir(const ExternalDependency& dep, std::string_view target);
    // Where BuildExternal leaves this dependency: the CMake build directory,
    // or the clone itself when it is only fetched. Pure, like ExternalCloneDir.
    // Build() keys a pass's record of the work on it rather than on the clone,
    // so a declaration that shares the clone but builds it with CMake is not
    // handed the outcome of a fetch alone.
    fs::path ExternalBuildDir(const ExternalDependency& dep, std::string_view target);
    // The -I flags this dependency contributes, from its declared includeDirs.
    // Also pure, which is what lets the linter's AST layer parse a source that
    // includes an external's headers without running a build to find out where
    // they are. The paths only resolve once something has fetched the clone.
    std::vector<std::string> ExternalIncludeFlags(const ExternalDependency& dep, std::string_view target);
    // Fetches the clone and, for ExternalBuilder::CMake, configures and builds
    // it. Empty on success, otherwise what failed. A lock on the clone is held
    // throughout, so another crafter-build, or another build pass in this one,
    // works on it before or after this call and never during it. Not
    // cancellable once started: Build() hands the outcome to every
    // configuration of the pass that declares the dependency, and a run cut
    // short would leave them a clone nobody fetched.
    std::string BuildExternal(const ExternalDependency& dep, std::string_view target);
    // What a configuration that declares `dep` compiles and links with once
    // BuildExternal has run: the -I flags and, for CMake, the -L, -rpath and -l
    // flags and the newest library. Per declaration, because two that share a
    // clone can still differ in includeDirs, libDirs and libs.
    ExternalBuildResult ExternalOutputs(const ExternalDependency& dep, std::string_view target);

    // The args the project file now running its CrafterBuildProject was
    // loaded with: everything that function receives, --target=, --debug and
    // the other standard flags included. Not cfg.projectArgs, which holds
    // only what ApplyStandardArgs left uninterpreted: `.args =
    // cfg.projectArgs` would drop the target and the build type. Empty
    // everywhere else, because it reads the stack LoadProject keeps per
    // thread, as IsTopLevelProject does: outside a project file, on any
    // thread but the one running it, once CrafterBuildProject has returned
    // (a script runs later), and before it is called, which covers the
    // file's static initialisers and its `#pragma crafter dependency`
    // pre-pass. The specs below default their args to it. Defined beside
    // LoadProject, but declared here so those defaults can see it: importing
    // :Platform into this partition would make the exported `struct
    // Configuration;` above a redeclaration of :Platform's unexported one,
    // which clang rejects.
    std::vector<std::string> ProjectArgs();

    // Specification for a sibling crafter-build project to fetch and depend on.
    // GitSource picks the revision: leave branch + commit empty for the
    // remote's default branch HEAD (sloppy but convenient), set branch to
    // track a branch tip, or set commit to pin to an immutable SHA. args are
    // what the dep's CrafterBuildProject receives. They default to this
    // project's own, read when the spec is made, so --target=, --march=,
    // --debug and the project's own flags reach every sibling down a chain
    // without being passed. Set them to forward something else: {} for
    // nothing, or a list built from this project's args, such as one without
    // a flag only this project reads. Give such a list to every sibling:
    // Build() refuses a graph in which two paths load one project with two
    // different lists, since the program would end up with both builds.
    struct GitProjectSpec {
        GitSource source;
        fs::path projectFile = "project.cpp";
        std::vector<std::string> args = ProjectArgs();
    };

    // Clones the spec's git URL into the external cache, recursively
    // LoadProject's the remote's project.cpp, and returns a stable
    // Configuration* you can drop into cfg.dependencies. The clone is keyed by
    // url+branch+commit+projectFile alone, so every arg list builds in the
    // same working tree, each into variant directories of its own. The
    // Configuration is owned by an internal cache for the lifetime of the
    // build, keyed by the clone and the args: identical specs share one.
    Configuration* GitProject(const GitProjectSpec& spec);

    // Specification for a local sibling crafter-build project (e.g. an
    // example folder depending on its parent project, or a workspace where
    // multiple projects live side-by-side without going through git).
    struct LocalProjectSpec {
        fs::path projectFile;                            // relative to cwd or absolute
        std::vector<std::string> args = ProjectArgs();   // as GitProjectSpec::args
    };

    // Same as GitProject but for a local on-disk project — no fetch, no
    // cache copy. Resolves projectFile to its canonical absolute path and
    // recursively LoadProject's it. Returns a stable Configuration* owned
    // by the same internal cache as GitProject.
    Configuration* LocalProject(const LocalProjectSpec& spec);

    // Clone (or update) the given git source into the shared external
    // cache and return the path to the cloned working tree. Intended for
    // example projects that need large asset bundles which shouldn't
    // live in the parent repo — push the returned path (or specific
    // files inside it) into `cfg.assets`. Reuses the same cache root as
    // ExternalDependency / GitProject. Caching key = url + branch + commit;
    // identical calls reuse the existing clone. Pin `source.commit` to a
    // SHA for reproducible, offline-after-first-fetch builds.
    fs::path GitFetch(const GitSource& source);
}

namespace Crafter {
    // Where GitProject or LocalProject loaded a Configuration from. The
    // loader keeps this beside the cache that owns the Configuration, since
    // the Configuration itself cannot say: only the one they return has its
    // path rebased, and the configurations a dependency's project file makes
    // for itself keep a path such as "./", which resolves against the
    // consumer's directory.
    struct LoadedProject {
        fs::path projectFile;   // absolute
        // What a consumer's AGENTS.md calls it: the repository's name for a
        // git project, with the path below the clone's root for one that is
        // not at it, and the directory's name for a local one. The same on
        // every machine and for a --local checkout and its clone alike,
        // which a path into the cache or a sibling checkout is not, and free
        // of what a URL can carry, credentials included.
        std::string name;
        // Which library this is, whatever the revision: the repository and
        // the project file in it for git, the project file for a local one.
        // Two specs that pin one library differently are one library.
        std::string identity;
    };
    // The LoadedProject behind a Configuration that GitProject or
    // LocalProject returned; nullopt for any other: the project crafter-build
    // was pointed at, and every configuration a project file makes itself.
    std::optional<LoadedProject> LoadedProjectOf(const Configuration& cfg);
}