backend/src/git.cpp

/*  This file is part of FediBlock-backend.
 *  Copyright © 2020 tastytea <tastytea@tastytea.de>
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as published by
 *  the Free Software Foundation, version 3.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "git.hpp"

#include "config.hpp"
#include "files.hpp"
#include "fs-compat.hpp"
#include "gitea.hpp"
#include "json.hpp"

#include <fmt/format.h>
#include <fmt/ostream.h> // For compatibility with fmt 4.
#include <git2.h>

#include <chrono>
#include <cstdint>
#include <fstream>
#include <stdexcept>
#include <string>
#include <string_view>
#include <thread>

#if LIBGIT2_VER_MAJOR == 0
#    if LIBGIT2_VER_MINOR < 28
#        define git_error_last giterr_last
#    endif
#    if LIBGIT2_VER_MINOR < 99
#        define git_credential_ssh_key_new git_cred_ssh_key_new
#        define git_push_options_init git_push_init_options
#        define git_fetch_options_init git_fetch_init_options
#        define git_checkout_options_init git_checkout_init_options
#    endif
#endif

namespace FediBlock::git
{

using fmt::format;
using std::ofstream;
using std::runtime_error;
using std::string;
using std::string_view;
using std::to_string;
using std::uint8_t;
using std::this_thread::sleep_for;

using namespace std::chrono_literals;

git_repository *_repo{nullptr};
const string _clone_url{format("git@{:s}:{:s}/{:s}.git", config::forge_domain,
                               config::forge_org, config::forge_repo_data)};
fs::path _repo_dir{};

void init(const bool cache)
{
    if (cache)
    {
        _repo_dir = files::get_cachedir() / "repo";
    }
    else
    {
        _repo_dir = files::get_tmpdir() / "repo";
    }

    git_libgit2_init();
}

void cleanup(const bool cache)
{
    git_libgit2_shutdown();

    if (cache)
    {
        files::remove_lockfile();
    }
    else
    {
        files::remove_tmpdir();
    }
}

void check(int error)
{
    if (error != 0)
    {
        const git_error *e = git_error_last();
        throw runtime_error{e->message};
    }
}

int cred_acquire(git_cred **cred, const char * /*url*/,
                 const char *username_from_url, unsigned int /*allowed_types*/,
                 void * /*payload*/)
{
    const auto datadir{files::get_datadir()};

    return git_credential_ssh_key_new(cred, username_from_url,
                                      (datadir / "ssh_id.pub").c_str(),
                                      (datadir / "ssh_id").c_str(), nullptr);
}

void clone()
{
    git_clone_options options = GIT_CLONE_OPTIONS_INIT;
    options.fetch_opts.callbacks.credentials = cred_acquire;
    check(git_clone(&_repo, _clone_url.data(), _repo_dir.c_str(), &options));
}

void create_branch()
{
    const string branch_name{get_branch_name()};
    const string ref_name{"refs/heads/" + branch_name};
    git_oid oid_parent;
    git_commit *commit{nullptr};

    // Get SHA1 of HEAD.
    check(git_reference_name_to_id(&oid_parent, _repo, "HEAD"));

    // Translate SHA-1 to git_commit.
    check(git_commit_lookup(&commit, _repo, &oid_parent));

    git_reference *branch{nullptr};
    // Create new branch.
    check(git_branch_create(&branch, _repo, branch_name.c_str(), commit, 0));

    check(git_repository_set_head(_repo, ref_name.c_str()));
}

void commit(const entry_type &entry)
{
    // Write files.
    const string basename{_repo_dir / get_branch_name()};

    ofstream file(basename + ".json");
    if (!file.good())
    {
        throw runtime_error{
            format("Could not create file: {:s}.json", basename)};
    }
    file << json::to_json(entry);
    file.close();

    if (!entry.screenshot_filepaths.empty())
    {
        uint8_t counter{0};
        for (const auto &screenshot : entry.screenshot_filepaths)
        {
            ++counter;
            const string extension{fs::path(screenshot).extension()};
            fs::copy(screenshot,
                     basename + "-" += to_string(counter) += extension);
        }
    }

    // Add files.
    git_index *index{nullptr};
    check(git_repository_index(&index, _repo));

    check(git_index_add_all(index, nullptr, 0, nullptr, nullptr));

    check(git_index_write(index));

    // Create commit.
    git_signature *sig{nullptr};
    git_oid oid_commit;
    git_oid oid_tree;
    git_oid oid_parent;
    git_tree *tree{nullptr};
    git_object *parent{nullptr};
    git_reference *ref{nullptr};

    check(git_signature_now(&sig, "Web", "Don't @ me"));

    check(git_revparse_ext(&parent, &ref, _repo, "HEAD"));

    check(git_repository_index(&index, _repo));

    check(git_index_write_tree(&oid_tree, index));

    check(git_index_write(index));

    check(git_tree_lookup(&tree, _repo, &oid_tree));

    check(git_reference_name_to_id(&oid_parent, _repo, "HEAD"));

    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-vararg)
    check(git_commit_create_v(&oid_commit, _repo, "HEAD", sig, sig, nullptr,
                              ("New entry: " + entry.instance).c_str(), tree,
                              parent != nullptr ? 1 : 0, parent));

    git_index_free(index);
    git_signature_free(sig);
    git_tree_free(tree);
    git_object_free(parent);
    git_reference_free(ref);
}

void push()
{
    git_push_options options;
    git_remote *remote{nullptr};
    string refspec_str{("refs/heads/" + get_branch_name())};
    char *refspec = &refspec_str[0];
    const git_strarray refspecs = {&refspec, 1};

    check(git_remote_lookup(&remote, _repo, "origin"));
    check(git_push_options_init(&options, GIT_PUSH_OPTIONS_VERSION));
    options.callbacks.credentials = cred_acquire;

    check(git_remote_push(remote, &refspecs, &options));

    git_remote_free(remote);
}

string get_branch_name()
{
    const auto id{gitea::get_last_pr_number() + 1};
    return "web-" + to_string(id);
}

void update_cached_repo(const uint8_t timeout)
{
    bool lock_created{false};
    for (uint8_t counter{0}; counter < timeout; ++counter)
    {
        if ((lock_created = files::create_lockfile()))
        {
            break;
        }
        sleep_for(1s);
    }
    if (!lock_created)
    {
        throw runtime_error{"Repository was locked for too long, giving up."};
    }

    if (!fs::exists(_repo_dir / ".git"))
    {
        clone();
        return;
    }

    git_remote *remote{nullptr};
    check(git_repository_open(&_repo, _repo_dir.c_str()));
    check(git_remote_lookup(&remote, _repo, "origin"));

    git_fetch_options fetch_opts;
    check(git_fetch_options_init(&fetch_opts, GIT_FETCH_OPTIONS_VERSION));
    fetch_opts.callbacks.credentials = cred_acquire;
    check(git_remote_fetch(remote, nullptr, &fetch_opts, nullptr));

    // FIXME: HEAD is detached.
    git_checkout_options checkout_opts;
    check(git_checkout_options_init(&checkout_opts,
                                    GIT_CHECKOUT_OPTIONS_VERSION));
    checkout_opts.checkout_strategy = GIT_CHECKOUT_FORCE;

    check(git_repository_set_head(_repo, "refs/remotes/origin/main"));
    check(git_checkout_head(_repo, &checkout_opts));

    git_remote_free(remote);
}

} // namespace FediBlock::git