#include "builtin.h"
#include "config.h"
#include "parse-options.h"
#include "refs.h"
#include "lockfile.h"
#include "cache-tree.h"
#include "unpack-trees.h"
#include "merge-recursive.h"
#include "argv-array.h"
#include "run-command.h"
#include "dir.h"
#include "rerere.h"

static const char * const git_stash_helper_usage[] = {
	N_("git stash--helper apply [--index] [-q|--quiet] [<stash>]"),
	NULL
};

static const char * const git_stash_helper_apply_usage[] = {
	N_("git stash--helper apply [--index] [-q|--quiet] [<stash>]"),
	NULL
};

static const char *ref_stash = "refs/stash";
static struct strbuf stash_index_path = STRBUF_INIT;

/*
 * w_commit is set to the commit containing the working tree
 * b_commit is set to the base commit
 * i_commit is set to the commit containing the index tree
 * u_commit is set to the commit containing the untracked files tree
 * w_tree is set to the working tree
 * b_tree is set to the base tree
 * i_tree is set to the index tree
 * u_tree is set to the untracked files tree
 */
struct stash_info {
	struct object_id w_commit;
	struct object_id b_commit;
	struct object_id i_commit;
	struct object_id u_commit;
	struct object_id w_tree;
	struct object_id b_tree;
	struct object_id i_tree;
	struct object_id u_tree;
	struct strbuf revision;
	int is_stash_ref;
	int has_u;
};

static void free_stash_info(struct stash_info *info)
{
	strbuf_release(&info->revision);
}

static void assert_stash_like(struct stash_info *info, const char *revision)
{
	if (get_oidf(&info->b_commit, "%s^1", revision) ||
	    get_oidf(&info->w_tree, "%s:", revision) ||
	    get_oidf(&info->b_tree, "%s^1:", revision) ||
	    get_oidf(&info->i_tree, "%s^2:", revision))
		die(_("'%s' is not a stash-like commit"), revision);
}

static int get_stash_info(struct stash_info *info, int argc, const char **argv)
{
	int ret;
	char *end_of_rev;
	char *expanded_ref;
	const char *revision;
	const char *commit = NULL;
	struct object_id dummy;
	struct strbuf symbolic = STRBUF_INIT;

	if (argc > 1) {
		int i;
		struct strbuf refs_msg = STRBUF_INIT;

		for (i = 0; i < argc; i++)
			strbuf_addf(&refs_msg, " '%s'", argv[i]);

		fprintf_ln(stderr, _("Too many revisions specified:%s"),
			   refs_msg.buf);
		strbuf_release(&refs_msg);

		return -1;
	}

	if (argc == 1)
		commit = argv[0];

	strbuf_init(&info->revision, 0);
	if (!commit) {
		if (!ref_exists(ref_stash)) {
			free_stash_info(info);
			fprintf_ln(stderr, _("No stash entries found."));
			return -1;
		}

		strbuf_addf(&info->revision, "%s@{0}", ref_stash);
	} else if (strspn(commit, "0123456789") == strlen(commit)) {
		strbuf_addf(&info->revision, "%s@{%s}", ref_stash, commit);
	} else {
		strbuf_addstr(&info->revision, commit);
	}

	revision = info->revision.buf;

	if (get_oid(revision, &info->w_commit)) {
		error(_("%s is not a valid reference"), revision);
		free_stash_info(info);
		return -1;
	}

	assert_stash_like(info, revision);

	info->has_u = !get_oidf(&info->u_tree, "%s^3:", revision);

	end_of_rev = strchrnul(revision, '@');
	strbuf_add(&symbolic, revision, end_of_rev - revision);

	ret = dwim_ref(symbolic.buf, symbolic.len, &dummy, &expanded_ref);
	strbuf_release(&symbolic);
	switch (ret) {
	case 0: /* Not found, but valid ref */
		info->is_stash_ref = 0;
		break;
	case 1:
		info->is_stash_ref = !strcmp(expanded_ref, ref_stash);
		break;
	default: /* Invalid or ambiguous */
		free_stash_info(info);
	}

	free(expanded_ref);
	return !(ret == 0 || ret == 1);
}

static int reset_tree(struct object_id *i_tree, int update, int reset)
{
	int nr_trees = 1;
	struct unpack_trees_options opts;
	struct tree_desc t[MAX_UNPACK_TREES];
	struct tree *tree;
	struct lock_file lock_file = LOCK_INIT;

	read_cache_preload(NULL);
	if (refresh_cache(REFRESH_QUIET))
		return -1;

	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);

	memset(&opts, 0, sizeof(opts));

	tree = parse_tree_indirect(i_tree);
	if (parse_tree(tree))
		return -1;

	init_tree_desc(t, tree->buffer, tree->size);

	opts.head_idx = 1;
	opts.src_index = &the_index;
	opts.dst_index = &the_index;
	opts.merge = 1;
	opts.reset = reset;
	opts.update = update;
	opts.fn = oneway_merge;

	if (unpack_trees(nr_trees, t, &opts))
		return -1;

	if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
		return error(_("unable to write new index file"));

	return 0;
}

static int diff_tree_binary(struct strbuf *out, struct object_id *w_commit)
{
	struct child_process cp = CHILD_PROCESS_INIT;
	const char *w_commit_hex = oid_to_hex(w_commit);

	/*
	 * Diff-tree would not be very hard to replace with a native function,
	 * however it should be done together with apply_cached.
	 */
	cp.git_cmd = 1;
	argv_array_pushl(&cp.args, "diff-tree", "--binary", NULL);
	argv_array_pushf(&cp.args, "%s^2^..%s^2", w_commit_hex, w_commit_hex);

	return pipe_command(&cp, NULL, 0, out, 0, NULL, 0);
}

static int apply_cached(struct strbuf *out)
{
	struct child_process cp = CHILD_PROCESS_INIT;

	/*
	 * Apply currently only reads either from stdin or a file, thus
	 * apply_all_patches would have to be updated to optionally take a
	 * buffer.
	 */
	cp.git_cmd = 1;
	argv_array_pushl(&cp.args, "apply", "--cached", NULL);
	return pipe_command(&cp, out->buf, out->len, NULL, 0, NULL, 0);
}

static int reset_head(void)
{
	struct child_process cp = CHILD_PROCESS_INIT;

	/*
	 * Reset is overall quite simple, however there is no current public
	 * API for resetting.
	 */
	cp.git_cmd = 1;
	argv_array_push(&cp.args, "reset");

	return run_command(&cp);
}

static int get_newly_staged(struct strbuf *out, struct object_id *c_tree)
{
	struct child_process cp = CHILD_PROCESS_INIT;
	const char *c_tree_hex = oid_to_hex(c_tree);

	/*
	 * diff-index is very similar to diff-tree above, and should be
	 * converted together with update_index.
	 */
	cp.git_cmd = 1;
	argv_array_pushl(&cp.args, "diff-index", "--cached", "--name-only",
			 "--diff-filter=A", NULL);
	argv_array_push(&cp.args, c_tree_hex);
	return pipe_command(&cp, NULL, 0, out, 0, NULL, 0);
}

static int update_index(struct strbuf *out)
{
	struct child_process cp = CHILD_PROCESS_INIT;

	/*
	 * Update-index is very complicated and may need to have a public
	 * function exposed in order to remove this forking.
	 */
	cp.git_cmd = 1;
	argv_array_pushl(&cp.args, "update-index", "--add", "--stdin", NULL);
	return pipe_command(&cp, out->buf, out->len, NULL, 0, NULL, 0);
}

static int restore_untracked(struct object_id *u_tree)
{
	int res;
	struct child_process cp = CHILD_PROCESS_INIT;

	/*
	 * We need to run restore files from a given index, but without
	 * affecting the current index, so we use GIT_INDEX_FILE with
	 * run_command to fork processes that will not interfere.
	 */
	cp.git_cmd = 1;
	argv_array_push(&cp.args, "read-tree");
	argv_array_push(&cp.args, oid_to_hex(u_tree));
	argv_array_pushf(&cp.env_array, "GIT_INDEX_FILE=%s",
			 stash_index_path.buf);
	if (run_command(&cp)) {
		remove_path(stash_index_path.buf);
		return -1;
	}

	child_process_init(&cp);
	cp.git_cmd = 1;
	argv_array_pushl(&cp.args, "checkout-index", "--all", NULL);
	argv_array_pushf(&cp.env_array, "GIT_INDEX_FILE=%s",
			 stash_index_path.buf);

	res = run_command(&cp);
	remove_path(stash_index_path.buf);
	return res;
}

static int do_apply_stash(const char *prefix, struct stash_info *info,
			  int index, int quiet)
{
	int ret;
	int has_index = index;
	struct merge_options o;
	struct object_id c_tree;
	struct object_id index_tree;
	struct commit *result;
	const struct object_id *bases[1];

	read_cache_preload(NULL);
	if (refresh_cache(REFRESH_QUIET))
		return -1;

	if (write_cache_as_tree(&c_tree, 0, NULL))
		return error(_("cannot apply a stash in the middle of a merge"));

	if (index) {
		if (oideq(&info->b_tree, &info->i_tree) ||
		    oideq(&c_tree, &info->i_tree)) {
			has_index = 0;
		} else {
			struct strbuf out = STRBUF_INIT;

			if (diff_tree_binary(&out, &info->w_commit)) {
				strbuf_release(&out);
				return error(_("could not generate diff %s^!."),
					     oid_to_hex(&info->w_commit));
			}

			ret = apply_cached(&out);
			strbuf_release(&out);
			if (ret)
				return error(_("conflicts in index."
					       "Try without --index."));

			discard_cache();
			read_cache();
			if (write_cache_as_tree(&index_tree, 0, NULL))
				return error(_("could not save index tree"));

			reset_head();
		}
	}

	if (info->has_u && restore_untracked(&info->u_tree))
		return error(_("could not restore untracked files from stash"));

	init_merge_options(&o);

	o.branch1 = "Updated upstream";
	o.branch2 = "Stashed changes";

	if (oideq(&info->b_tree, &c_tree))
		o.branch1 = "Version stash was based on";

	if (quiet)
		o.verbosity = 0;

	if (o.verbosity >= 3)
		printf_ln(_("Merging %s with %s"), o.branch1, o.branch2);

	bases[0] = &info->b_tree;

	ret = merge_recursive_generic(&o, &c_tree, &info->w_tree, 1, bases,
				      &result);
	if (ret) {
		rerere(0);

		if (index)
			fprintf_ln(stderr, _("Index was not unstashed."));

		return ret;
	}

	if (has_index) {
		if (reset_tree(&index_tree, 0, 0))
			return -1;
	} else {
		struct strbuf out = STRBUF_INIT;

		if (get_newly_staged(&out, &c_tree)) {
			strbuf_release(&out);
			return -1;
		}

		if (reset_tree(&c_tree, 0, 1)) {
			strbuf_release(&out);
			return -1;
		}

		ret = update_index(&out);
		strbuf_release(&out);
		if (ret)
			return -1;

		discard_cache();
	}

	if (quiet) {
		if (refresh_cache(REFRESH_QUIET))
			warning("could not refresh index");
	} else {
		struct child_process cp = CHILD_PROCESS_INIT;

		/*
		 * Status is quite simple and could be replaced with calls to
		 * wt_status in the future, but it adds complexities which may
		 * require more tests.
		 */
		cp.git_cmd = 1;
		cp.dir = prefix;
		argv_array_push(&cp.args, "status");
		run_command(&cp);
	}

	return 0;
}

static int apply_stash(int argc, const char **argv, const char *prefix)
{
	int ret;
	int quiet = 0;
	int index = 0;
	struct stash_info info;
	struct option options[] = {
		OPT__QUIET(&quiet, N_("be quiet, only report errors")),
		OPT_BOOL(0, "index", &index,
			 N_("attempt to recreate the index")),
		OPT_END()
	};

	argc = parse_options(argc, argv, prefix, options,
			     git_stash_helper_apply_usage, 0);

	if (get_stash_info(&info, argc, argv))
		return -1;

	ret = do_apply_stash(prefix, &info, index, quiet);
	free_stash_info(&info);
	return ret;
}

int cmd_stash__helper(int argc, const char **argv, const char *prefix)
{
	pid_t pid = getpid();
	const char *index_file;

	struct option options[] = {
		OPT_END()
	};

	git_config(git_default_config, NULL);

	argc = parse_options(argc, argv, prefix, options, git_stash_helper_usage,
			     PARSE_OPT_KEEP_UNKNOWN | PARSE_OPT_KEEP_DASHDASH);

	index_file = get_index_file();
	strbuf_addf(&stash_index_path, "%s.stash.%" PRIuMAX, index_file,
		    (uintmax_t)pid);

	if (argc < 1)
		usage_with_options(git_stash_helper_usage, options);
	if (!strcmp(argv[0], "apply"))
		return !!apply_stash(argc, argv, prefix);

	usage_msg_opt(xstrfmt(_("unknown subcommand: %s"), argv[0]),
		      git_stash_helper_usage, options);
}