/*
 * "git replay" builtin command
 */

#define USE_THE_INDEX_VARIABLE
#include "git-compat-util.h"

#include "builtin.h"
#include "environment.h"
#include "hex.h"
#include "lockfile.h"
#include "merge-ort.h"
#include "object-name.h"
#include "parse-options.h"
#include "refs.h"
#include "revision.h"
#include <oidset.h>
#include <tree.h>

static const char *short_commit_name(struct commit *commit)
{
	return repo_find_unique_abbrev(the_repository, &commit->object.oid,
				       DEFAULT_ABBREV);
}

static struct commit *peel_committish(const char *name)
{
	struct object *obj;
	struct object_id oid;

	if (repo_get_oid(the_repository, name, &oid))
		return NULL;
	obj = parse_object(the_repository, &oid);
	return (struct commit *)repo_peel_to_type(the_repository, name, 0, obj,
						  OBJ_COMMIT);
}

static char *get_author(const char *message)
{
	size_t len;
	const char *a;

	a = find_commit_header(message, "author", &len);
	if (a)
		return xmemdupz(a, len);

	return NULL;
}

static struct commit *create_commit(struct tree *tree,
				    struct commit *based_on,
				    struct commit *parent)
{
	struct object_id ret;
	struct object *obj;
	struct commit_list *parents = NULL;
	char *author;
	char *sign_commit = NULL; /* FIXME: cli users might want to sign again */
	struct commit_extra_header *extra;
	struct strbuf msg = STRBUF_INIT;
	const char *out_enc = get_commit_output_encoding();
	const char *message = repo_logmsg_reencode(the_repository, based_on,
						   NULL, out_enc);
	const char *orig_message = NULL;
	const char *exclude_gpgsig[] = { "gpgsig", NULL };

	commit_list_insert(parent, &parents);
	extra = read_commit_extra_headers(based_on, exclude_gpgsig);
	find_commit_subject(message, &orig_message);
	strbuf_addstr(&msg, orig_message);
	author = get_author(message);
	reset_ident_date();
	if (commit_tree_extended(msg.buf, msg.len, &tree->object.oid, parents,
				 &ret, author, NULL, sign_commit, extra)) {
		error(_("failed to write commit object"));
		return NULL;
	}
	free(author);
	strbuf_release(&msg);

	obj = parse_object(the_repository, &ret);
	return (struct commit *)obj;
}

static struct commit *pick_regular_commit(struct commit *pickme,
					  struct commit *last_commit,
					  struct merge_options *merge_opt,
					  struct merge_result *result)
{
	struct commit *base;
	struct tree *pickme_tree, *base_tree;

	base = pickme->parents->item;

	pickme_tree = repo_get_commit_tree(the_repository, pickme);
	base_tree = repo_get_commit_tree(the_repository, base);

	merge_opt->branch1 = short_commit_name(last_commit);
	merge_opt->branch2 = short_commit_name(pickme);
	merge_opt->ancestor = xstrfmt("parent of %s", merge_opt->branch2);

	merge_incore_nonrecursive(merge_opt,
				  base_tree,
				  result->tree,
				  pickme_tree,
				  result);

	free((char*)merge_opt->ancestor);
	merge_opt->ancestor = NULL;
	if (!result->clean)
		return NULL;
	return create_commit(result->tree, pickme, last_commit);
}

int cmd_replay(int argc, const char **argv, const char *prefix)
{
	struct commit *onto;
	const char *onto_name = NULL;
	struct commit *last_commit = NULL;
	struct rev_info revs;
	struct commit *commit;
	struct merge_options merge_opt;
	struct merge_result result;
	int ret = 0;

	const char * const replay_usage[] = {
		N_("(EXPERIMENTAL!) git replay --onto <newbase> <revision-range>..."),
		NULL
	};
	struct option replay_options[] = {
		OPT_STRING(0, "onto", &onto_name,
			   N_("revision"),
			   N_("replay onto given commit")),
		OPT_END()
	};

	argc = parse_options(argc, argv, prefix, replay_options, replay_usage,
			     PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_KEEP_UNKNOWN_OPT);

	if (!onto_name) {
		error(_("option --onto is mandatory"));
		usage_with_options(replay_usage, replay_options);
	}

	onto = peel_committish(onto_name);

	repo_init_revisions(the_repository, &revs, prefix);

	/*
	 * Set desired values for rev walking options here. If they
	 * are changed by some user specified option in setup_revisions()
	 * below, we will detect that below and then warn.
	 *
	 * TODO: In the future we might want to either die(), or allow
	 * some options changing these values if we think they could
	 * be useful.
	 */
	revs.reverse = 1;
	revs.sort_order = REV_SORT_IN_GRAPH_ORDER;
	revs.topo_order = 1;
	revs.simplify_history = 0;

	argc = setup_revisions(argc, argv, &revs, NULL);
	if (argc > 1) {
		ret = error(_("unrecognized argument: %s"), argv[1]);
		goto cleanup;
	}

	/*
	 * Detect and warn if we override some user specified rev
	 * walking options.
	 */
	if (revs.reverse != 1) {
		warning(_("some rev walking options will be overridden as "
			  "'%s' bit in 'struct rev_info' will be forced"),
			"reverse");
		revs.reverse = 1;
	}
	if (revs.sort_order != REV_SORT_IN_GRAPH_ORDER) {
		warning(_("some rev walking options will be overridden as "
			  "'%s' bit in 'struct rev_info' will be forced"),
			"sort_order");
		revs.sort_order = REV_SORT_IN_GRAPH_ORDER;
	}
	if (revs.topo_order != 1) {
		warning(_("some rev walking options will be overridden as "
			  "'%s' bit in 'struct rev_info' will be forced"),
			"topo_order");
		revs.topo_order = 1;
	}
	if (revs.simplify_history != 0) {
		warning(_("some rev walking options will be overridden as "
			  "'%s' bit in 'struct rev_info' will be forced"),
			"simplify_history");
		revs.simplify_history = 0;
	}

	if (prepare_revision_walk(&revs) < 0) {
		ret = error(_("error preparing revisions"));
		goto cleanup;
	}

	init_merge_options(&merge_opt, the_repository);
	memset(&result, 0, sizeof(result));
	merge_opt.show_rename_progress = 0;
	result.tree = repo_get_commit_tree(the_repository, onto);
	last_commit = onto;
	while ((commit = get_revision(&revs))) {
		const struct name_decoration *decoration;

		if (!commit->parents)
			die(_("replaying down to root commit is not supported yet!"));
		if (commit->parents->next)
			die(_("replaying merge commits is not supported yet!"));

		last_commit = pick_regular_commit(commit, last_commit, &merge_opt, &result);
		if (!last_commit)
			break;

		decoration = get_name_decoration(&commit->object);
		if (!decoration)
			continue;

		while (decoration) {
			if (decoration->type == DECORATION_REF_LOCAL) {
				printf("update %s %s %s\n",
				       decoration->name,
				       oid_to_hex(&last_commit->object.oid),
				       oid_to_hex(&commit->object.oid));
			}
			decoration = decoration->next;
		}
	}

	merge_finalize(&merge_opt, &result);
	ret = result.clean;

cleanup:
	release_revisions(&revs);

	/* Return */
	if (ret < 0)
		exit(128);
	return ret ? 0 : 1;
}