/*
* Copyright (C) the libgit2 contributors. All rights reserved.
*
* This file is part of libgit2, distributed under the GNU GPL v2 with
* a Linking Exception. For full terms see the included COPYING file.
*/

#include "common.h"
#include "repository.h"
#include "filebuf.h"
#include "merge.h"
#include "revert.h"

#include "git2/types.h"
#include "git2/merge.h"
#include "git2/revert.h"
#include "git2/commit.h"
#include "git2/sys/commit.h"

#define GIT_REVERT_FILE_MODE		0666

static int write_revert_head(
	git_repository *repo,
	const git_commit *commit,
	const char *commit_oidstr)
{
	git_filebuf file = GIT_FILEBUF_INIT;
	git_buf file_path = GIT_BUF_INIT;
	int error = 0;

	assert(repo && commit);

	if ((error = git_buf_joinpath(&file_path, repo->path_repository, GIT_REVERT_HEAD_FILE)) >= 0 &&
		(error = git_filebuf_open(&file, file_path.ptr, GIT_FILEBUF_FORCE, GIT_REVERT_FILE_MODE)) >= 0 &&
		(error = git_filebuf_printf(&file, "%s\n", commit_oidstr)) >= 0)
		error = git_filebuf_commit(&file);

	if (error < 0)
		git_filebuf_cleanup(&file);

	git_buf_free(&file_path);

	return error;
}

static int write_merge_msg(
	git_repository *repo,
	const git_commit *commit,
	const char *commit_oidstr,
	const char *commit_msgline)
{
	git_filebuf file = GIT_FILEBUF_INIT;
	git_buf file_path = GIT_BUF_INIT;
	int error = 0;

	assert(repo && commit);

	if ((error = git_buf_joinpath(&file_path, repo->path_repository, GIT_MERGE_MSG_FILE)) < 0 ||
		(error = git_filebuf_open(&file, file_path.ptr, GIT_FILEBUF_FORCE, GIT_REVERT_FILE_MODE)) < 0 ||
		(error = git_filebuf_printf(&file, "Revert \"%s\"\n\nThis reverts commit %s.\n",
		commit_msgline, commit_oidstr)) < 0)
		goto cleanup;

	error = git_filebuf_commit(&file);

cleanup:
	if (error < 0)
		git_filebuf_cleanup(&file);

	git_buf_free(&file_path);

	return error;
}

static int revert_normalize_opts(
	git_repository *repo,
	git_revert_opts *opts,
	const git_revert_opts *given,
	const char *their_label)
{
	int error = 0;
	unsigned int default_checkout_strategy = GIT_CHECKOUT_SAFE_CREATE |
		GIT_CHECKOUT_ALLOW_CONFLICTS;

	GIT_UNUSED(repo);

	if (given != NULL)
		memcpy(opts, given, sizeof(git_revert_opts));
	else {
		git_revert_opts default_opts = GIT_REVERT_OPTS_INIT;
		memcpy(opts, &default_opts, sizeof(git_revert_opts));
	}

	if (!opts->checkout_opts.checkout_strategy)
		opts->checkout_opts.checkout_strategy = default_checkout_strategy;

	if (!opts->checkout_opts.our_label)
		opts->checkout_opts.our_label = "HEAD";

	if (!opts->checkout_opts.their_label)
		opts->checkout_opts.their_label = their_label;

	return error;
}

int git_revert(
	git_repository *repo,
	git_commit *commit,
	const git_revert_opts *given_opts)
{
	git_revert_opts opts;
	git_commit *parent_commit = NULL;
	git_tree *parent_tree = NULL, *our_tree = NULL, *revert_tree = NULL;
	git_index *index_new = NULL, *index_repo = NULL;
	char commit_oidstr[GIT_OID_HEXSZ + 1];
	const char *commit_msg;
	git_buf their_label = GIT_BUF_INIT;
	int parent = 0;
	int error = 0;

	assert(repo && commit);

	if ((error = git_repository__ensure_not_bare(repo, "revert")) < 0)
		return error;

	git_oid_fmt(commit_oidstr, git_commit_id(commit));
	commit_oidstr[GIT_OID_HEXSZ] = '\0';

	if ((commit_msg = git_commit_summary(commit)) == NULL) {
		error = -1;
		goto on_error;
	}

	if ((error = git_buf_printf(&their_label, "parent of %.7s... %s", commit_oidstr, commit_msg)) < 0 ||
		(error = revert_normalize_opts(repo, &opts, given_opts, git_buf_cstr(&their_label))) < 0 ||
		(error = write_revert_head(repo, commit, commit_oidstr)) < 0 ||
		(error = write_merge_msg(repo, commit, commit_oidstr, commit_msg)) < 0 ||
		(error = git_repository_head_tree(&our_tree, repo)) < 0 ||
		(error = git_commit_tree(&revert_tree, commit)) < 0)
		goto on_error;

	if (git_commit_parentcount(commit) > 1) {
		if (!opts.mainline) {
			giterr_set(GITERR_REVERT,
				"Mainline branch is not specified but %s is a merge commit",
				commit_oidstr);
			error = -1;
			goto on_error;
		}

		parent = opts.mainline;
	} else {
		if (opts.mainline) {
			giterr_set(GITERR_REVERT,
				"Mainline branch was specified but %s is not a merge",
				commit_oidstr);
			error = -1;
			goto on_error;
		}

		parent = git_commit_parentcount(commit);
	}

	if (parent &&
		((error = git_commit_parent(&parent_commit, commit, (parent - 1))) < 0 ||
		(error = git_commit_tree(&parent_tree, parent_commit)) < 0))
		goto on_error;

	if ((error = git_merge_trees(&index_new, repo, revert_tree, our_tree, parent_tree, &opts.merge_tree_opts)) < 0 ||
		(error = git_merge__indexes(repo, index_new)) < 0 ||
		(error = git_repository_index(&index_repo, repo)) < 0 ||
		(error = git_checkout_index(repo, index_repo, &opts.checkout_opts)) < 0)
		goto on_error;

	goto done;

on_error:
	git_revert__cleanup(repo);

done:
	git_index_free(index_new);
	git_index_free(index_repo);
	git_tree_free(parent_tree);
	git_tree_free(our_tree);
	git_tree_free(revert_tree);
	git_commit_free(parent_commit);
	git_buf_free(&their_label);

	return error;
}

int git_revert__cleanup(git_repository *repo)
{
	int error = 0;
	git_buf revert_head_path = GIT_BUF_INIT,
		merge_msg_path = GIT_BUF_INIT;

	assert(repo);

	if (git_buf_joinpath(&revert_head_path, repo->path_repository, GIT_REVERT_HEAD_FILE) < 0 ||
		git_buf_joinpath(&merge_msg_path, repo->path_repository, GIT_MERGE_MSG_FILE) < 0)
		return -1;

	if (git_path_isfile(revert_head_path.ptr)) {
		if ((error = p_unlink(revert_head_path.ptr)) < 0)
			goto cleanup;
	}

	if (git_path_isfile(merge_msg_path.ptr))
		(void)p_unlink(merge_msg_path.ptr);

cleanup:
	git_buf_free(&merge_msg_path);
	git_buf_free(&revert_head_path);

	return error;
}