/*
 * This is a sample program that is similar to "git init".  See the
 * documentation for that (try "git help init") to understand what this
 * program is emulating.
 *
 * This demonstrates using the libgit2 APIs to initialize a new repository.
 *
 * This also contains a special additional option that regular "git init"
 * does not support which is "--initial-commit" to make a first empty commit.
 * That is demonstrated in the "create_initial_commit" helper function.
 *
 * 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 <stdio.h>
#include <git2.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

/* not actually good error handling */
static void fail(const char *msg, const char *arg)
{
	if (arg)
		fprintf(stderr, "%s %s\n", msg, arg);
	else
		fprintf(stderr, "%s\n", msg);
	exit(1);
}

static void usage(const char *error, const char *arg)
{
	fprintf(stderr, "error: %s '%s'\n", error, arg);
	fprintf(stderr, "usage: init [-q | --quiet] [--bare] "
			"[--template=<dir>] [--shared[=perms]] <directory>\n");
	exit(1);
}

/* simple string prefix test used in argument parsing */
static size_t is_prefixed(const char *arg, const char *pfx)
{
	size_t len = strlen(pfx);
	return !strncmp(arg, pfx, len) ? len : 0;
}

/* parse the tail of the --shared= argument */
static uint32_t parse_shared(const char *shared)
{
	if (!strcmp(shared, "false") || !strcmp(shared, "umask"))
		return GIT_REPOSITORY_INIT_SHARED_UMASK;

	else if (!strcmp(shared, "true") || !strcmp(shared, "group"))
		return GIT_REPOSITORY_INIT_SHARED_GROUP;

	else if (!strcmp(shared, "all") || !strcmp(shared, "world") ||
			 !strcmp(shared, "everybody"))
		return GIT_REPOSITORY_INIT_SHARED_ALL;

	else if (shared[0] == '0') {
		long val;
		char *end = NULL;
		val = strtol(shared + 1, &end, 8);
		if (end == shared + 1 || *end != 0)
			usage("invalid octal value for --shared", shared);
		return (uint32_t)val;
	}

	else
		usage("unknown value for --shared", shared);

	return 0;
}

/* forward declaration of helper to make an empty parent-less commit */
static void create_initial_commit(git_repository *repo);


int main(int argc, char *argv[])
{
	git_repository *repo = NULL;
	int no_options = 1, quiet = 0, bare = 0, initial_commit = 0, i;
	uint32_t shared = GIT_REPOSITORY_INIT_SHARED_UMASK;
	const char *template = NULL, *gitdir = NULL, *dir = NULL;
	size_t pfxlen;

	git_threads_init();

	/* Process arguments */

	for (i = 1; i < argc; ++i) {
		char *a = argv[i];

		if (a[0] == '-')
			no_options = 0;

		if (a[0] != '-') {
			if (dir != NULL)
				usage("extra argument", a);
			dir = a;
		}
		else if (!strcmp(a, "-q") || !strcmp(a, "--quiet"))
			quiet = 1;
		else if (!strcmp(a, "--bare"))
			bare = 1;
		else if ((pfxlen = is_prefixed(a, "--template=")) > 0)
			template = a + pfxlen;
		else if (!strcmp(a, "--separate-git-dir"))
			gitdir = argv[++i];
		else if ((pfxlen = is_prefixed(a, "--separate-git-dir=")) > 0)
			gitdir = a + pfxlen;
		else if (!strcmp(a, "--shared"))
			shared = GIT_REPOSITORY_INIT_SHARED_GROUP;
		else if ((pfxlen = is_prefixed(a, "--shared=")) > 0)
			shared = parse_shared(a + pfxlen);
		else if (!strcmp(a, "--initial-commit"))
			initial_commit = 1;
		else
			usage("unknown option", a);
	}

	if (!dir)
		usage("must specify directory to init", NULL);

	/* Initialize repository */

	if (no_options) {
		/* No options were specified, so let's demonstrate the default
		 * simple case of git_repository_init() API usage...
		 */

		if (git_repository_init(&repo, dir, 0) < 0)
			fail("Could not initialize repository", dir);
	}
	else {
		/* Some command line options were specified, so we'll use the
		 * extended init API to handle them
		 */
		git_repository_init_options opts = GIT_REPOSITORY_INIT_OPTIONS_INIT;

		if (bare)
			opts.flags |= GIT_REPOSITORY_INIT_BARE;

		if (template) {
			opts.flags |= GIT_REPOSITORY_INIT_EXTERNAL_TEMPLATE;
			opts.template_path = template;
		}

		if (gitdir) {
			/* if you specified a separate git directory, then initialize
			 * the repository at that path and use the second path as the
			 * working directory of the repository (with a git-link file)
			 */
			opts.workdir_path = dir;
			dir = gitdir;
		}

		if (shared != 0)
			opts.mode = shared;

		if (git_repository_init_ext(&repo, dir, &opts) < 0)
			fail("Could not initialize repository", dir);
	}

	/* Print a message to stdout like "git init" does */

	if (!quiet) {
		if (bare || gitdir)
			dir = git_repository_path(repo);
		else
			dir = git_repository_workdir(repo);

		printf("Initialized empty Git repository in %s\n", dir);
	}

	/* As an extension to the basic "git init" command, this example
	 * gives the option to create an empty initial commit.  This is
	 * mostly to demonstrate what it takes to do that, but also some
	 * people like to have that empty base commit in their repo.
	 */
	if (initial_commit) {
		create_initial_commit(repo);
		printf("Created empty initial commit\n");
	}

	git_repository_free(repo);
	git_threads_shutdown();

	return 0;
}

/* Unlike regular "git init", this example shows how to create an initial
 * empty commit in the repository.  This is the helper function that does
 * that.
 */
static void create_initial_commit(git_repository *repo)
{
	git_signature *sig;
	git_index *index;
	git_oid tree_id, commit_id;
	git_tree *tree;

	/* First use the config to initialize a commit signature for the user */

	if (git_signature_default(&sig, repo) < 0)
		fail("Unable to create a commit signature.",
			 "Perhaps 'user.name' and 'user.email' are not set");

	/* Now let's create an empty tree for this commit */

	if (git_repository_index(&index, repo) < 0)
		fail("Could not open repository index", NULL);

	/* Outside of this example, you could call git_index_add_bypath()
	 * here to put actual files into the index.  For our purposes, we'll
	 * leave it empty for now.
	 */

	if (git_index_write_tree(&tree_id, index) < 0)
		fail("Unable to write initial tree from index", NULL);

	git_index_free(index);

	if (git_tree_lookup(&tree, repo, &tree_id) < 0)
		fail("Could not look up initial tree", NULL);

	/* Ready to create the initial commit
	 *
	 * Normally creating a commit would involve looking up the current
	 * HEAD commit and making that be the parent of the initial commit,
	 * but here this is the first commit so there will be no parent.
	 */

	if (git_commit_create_v(
			&commit_id, repo, "HEAD", sig, sig,
			NULL, "Initial commit", tree, 0) < 0)
		fail("Could not create the initial commit", NULL);

	/* Clean up so we don't leak memory */

	git_tree_free(tree);
	git_signature_free(sig);
}