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

#include <cstdint>
#include <fstream>
#include <git2.h>

#include <stdexcept>
#include <string>
#include <string_view>

#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
#    endif
#endif

namespace FediBlock::git
{

using std::ofstream;
using std::runtime_error;
using std::stoull;
using std::string;
using std::string_view;
using std::to_string;
using std::uint64_t;

git_repository *_repo{nullptr};

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*/)
{
    return git_credential_ssh_key_new(
        cred, username_from_url, (files::get_datadir() / "ssh_id.pub").c_str(),
        (files::get_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, "git@schlomp.space:FediBlock/data.git",
                    (files::get_tmpdir() / "repo").c_str(), &options));
}

uint64_t get_last_id()
{
    constexpr string_view branch_prefix{"web-"};
    uint64_t id{0};

    git_branch_iterator *it;
    if (git_branch_iterator_new(&it, _repo, GIT_BRANCH_ALL) == 0)
    {
        git_reference *ref;
        git_branch_t type;
        while (git_branch_next(&ref, &type, it) == 0)
        {
            const char *out{nullptr};
            git_branch_name(&out, ref);
            if (type == GIT_BRANCH_REMOTE)
            {
                const string branch_name{out};
                size_t pos{branch_name.find(branch_prefix)};
                if (pos != string::npos)
                {
                    pos += branch_prefix.size();
                    uint64_t newid{stoull(branch_name.substr(pos))};
                    if (newid > id)
                    {
                        id = newid;
                    }
                }
            }
            git_reference_free(ref);
        }
        git_branch_iterator_free(it);
    }

    return id;
}

void create_branch()
{
    const auto id{get_last_id() + 1};
    const string branch_name = "web-" + std::to_string(id);
    const string ref_name{"refs/heads/" + branch_name};
    git_oid oid_parent;
    git_commit *commit;

    // 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;
    // 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 cgi::entry_type &entry)
{
    // Write files.
    const auto id{get_last_id() + 1};
    const string basename{files::get_tmpdir() / "repo"
                          / ("web-" + to_string(id))};

    ofstream file(basename + ".json");
    if (!file.good())
    {
        throw; // FIXME
    }
    file << json::to_json(entry);
    file.close();

    if (!entry.screenshot_filepath.empty())
    {
        const string extension{fs::path(entry.screenshot_filepath).extension()};
        fs::copy(entry.screenshot_filepath, basename + 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;
    git_oid oid_commit;
    git_oid oid_tree;
    git_oid oid_parent;
    git_tree *tree;
    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);
}

void push()
{
    git_push_options options;
    git_remote *remote{nullptr};
    const string branch_name{"web-" + std::to_string(get_last_id() + 1)};
    string refspec_str{("refs/heads/" + 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));
}

} // namespace FediBlock::git