#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <git2.h>

#include "dive.h"

/*
 * If it's not a git repo, return NULL. Be very conservative.
 */
struct git_repository *is_git_repository(const char *filename, const char **branchp)
{
	int flen, blen, ret;
	struct stat st;
	git_repository *repo;
	char *loc, *branch;

	flen = strlen(filename);
	if (!flen || filename[--flen] != ']')
		return NULL;

	/* Find the matching '[' */
	blen = 0;
	while (flen && filename[--flen] != '[')
		blen++;

	if (!flen)
		return NULL;

	/*
	 * This is the "point of no return": the name matches
	 * the git repository name rules, and we will no longer
	 * return NULL.
	 *
	 * We will either return "dummy_git_repository" and the
	 * branch pointer will have the _whole_ filename in it,
	 * or we will return a real git repository with the
	 * branch pointer being filled in with just the branch
	 * name.
	 *
	 * The actual git reading/writing routines can use this
	 * to generate proper error messages.
	 */
	*branchp = filename;
	loc = malloc(flen+1);
	if (!loc)
		return dummy_git_repository;
	memcpy(loc, filename, flen);
	loc[flen] = 0;

	branch = malloc(blen+1);
	if (!branch) {
		free(loc);
		return dummy_git_repository;
	}
	memcpy(branch, filename+flen+1, blen);
	branch[blen] = 0;

	if (stat(loc, &st) < 0 || !S_ISDIR(st.st_mode)) {
		free(loc);
		free(branch);
		return dummy_git_repository;
	}

	ret = git_repository_open(&repo, loc);
	free(loc);
	if (ret < 0) {
		free(branch);
		return dummy_git_repository;
	}
	*branchp = branch;
	return repo;
}