#include "cache.h"
#include "refs.h"
#include "pkt-line.h"
#include <sys/wait.h>

static const char fetch_pack_usage[] = "git-fetch-pack [host:]directory [heads]* < mycommitlist";
static const char *exec = "git-upload-pack";

static int get_ack(int fd, unsigned char *result_sha1)
{
	static char line[1000];
	int len = packet_read_line(fd, line, sizeof(line));

	if (!len)
		die("git-fetch-pack: expected ACK/NAK, got EOF");
	if (line[len-1] == '\n')
		line[--len] = 0;
	if (!strcmp(line, "NAK"))
		return 0;
	if (!strncmp(line, "ACK ", 3)) {
		if (!get_sha1_hex(line+4, result_sha1))
			return 1;
	}
	die("git-fetch_pack: expected ACK/NAK, got '%s'", line);
}

static int find_common(int fd[2], unsigned char *result_sha1, unsigned char *remote)
{
	static char line[1000];
	int count = 0, flushes = 0, retval;
	FILE *revs;

	revs = popen("git-rev-list $(git-rev-parse --all)", "r");
	if (!revs)
		die("unable to run 'git-rev-list'");
	packet_write(fd[1], "want %s\n", sha1_to_hex(remote));
	packet_flush(fd[1]);
	flushes = 1;
	retval = -1;
	while (fgets(line, sizeof(line), revs) != NULL) {
		unsigned char sha1[20];
		if (get_sha1_hex(line, sha1))
			die("git-fetch-pack: expected object name, got crud");
		packet_write(fd[1], "have %s\n", sha1_to_hex(sha1));
		if (!(31 & ++count)) {
			packet_flush(fd[1]);
			flushes++;

			/*
			 * We keep one window "ahead" of the other side, and
			 * will wait for an ACK only on the next one
			 */
			if (count == 32)
				continue;
			if (get_ack(fd[0], result_sha1)) {
				flushes = 0;
				retval = 0;
				break;
			}
			flushes--;
		}
	}
	pclose(revs);
	packet_write(fd[1], "done\n");
	while (flushes) {
		flushes--;
		if (get_ack(fd[0], result_sha1))
			return 0;
	}
	return retval;
}

static int get_old_sha1(const char *refname, unsigned char *sha1)
{
	int fd, ret;

	fd = open(git_path("%s", refname), O_RDONLY);
	ret = -1;
	if (fd >= 0) {
		char buffer[60];
		if (read(fd, buffer, sizeof(buffer)) >= 40)
			ret = get_sha1_hex(buffer, sha1);
		close(fd);
	}
	return ret;
}

static int check_ref(const char *refname, const unsigned char *sha1)
{
	unsigned char mysha1[20];
	char oldhex[41];

	if (get_old_sha1(refname, mysha1) < 0)
		memset(mysha1, 0, 20);

	if (!memcmp(sha1, mysha1, 20)) {
		fprintf(stderr, "%s: unchanged\n", refname);
		return 0;
	}
	
	memcpy(oldhex, sha1_to_hex(mysha1), 41);
	fprintf(stderr, "%s: %s (%s)\n", refname, sha1_to_hex(sha1), oldhex);
	return 1;
}

static int get_remote_heads(int fd, int nr_match, char **match, unsigned char *result)
{
	int count = 0;

	for (;;) {
		static char line[1000];
		unsigned char sha1[20];
		char *refname;
		int len;

		len = packet_read_line(fd, line, sizeof(line));
		if (!len)
			break;
		if (line[len-1] == '\n')
			line[--len] = 0;
		if (len < 42 || get_sha1_hex(line, sha1))
			die("git-fetch-pack: protocol error - expected ref descriptor, got '%sä'", line);
		refname = line+41;
		if (nr_match && !path_match(refname, nr_match, match))
			continue;
		if (check_ref(refname, sha1)) {
			count++;
			memcpy(result, sha1, 20);
		}
	}
	return count;
}

static int fetch_pack(int fd[2], int nr_match, char **match)
{
	unsigned char sha1[20], remote[20];
	int heads, status;
	pid_t pid;

	heads = get_remote_heads(fd[0], nr_match, match, remote);
	if (heads != 1) {
		packet_flush(fd[1]);
		die(heads ? "multiple remote heads" : "no matching remote head");
	}
	if (find_common(fd, sha1, remote) < 0)
		die("git-fetch-pack: no common commits");
	pid = fork();
	if (pid < 0)
		die("git-fetch-pack: unable to fork off git-unpack-objects");
	if (!pid) {
		close(fd[1]);
		dup2(fd[0], 0);
		close(fd[0]);
		execlp("git-unpack-objects", "git-unpack-objects", NULL);
		die("git-unpack-objects exec failed");
	}
	close(fd[0]);
	close(fd[1]);
	while (waitpid(pid, &status, 0) < 0) {
		if (errno != EINTR)
			die("waiting for git-unpack-objects: %s", strerror(errno));
	}
	if (WIFEXITED(status)) {
		int code = WEXITSTATUS(status);
		if (code)
			die("git-unpack-objects died with error code %d", code);
		puts(sha1_to_hex(remote));
		return 0;
	}
	if (WIFSIGNALED(status)) {
		int sig = WTERMSIG(status);
		die("git-unpack-objects died of signal %d", sig);
	}
	die("Sherlock Holmes! git-unpack-objects died of unnatural causes %d!", status);
}

int main(int argc, char **argv)
{
	int i, ret, nr_heads;
	char *dest = NULL, **heads;
	int fd[2];
	pid_t pid;

	nr_heads = 0;
	heads = NULL;
	for (i = 1; i < argc; i++) {
		char *arg = argv[i];

		if (*arg == '-') {
			/* Arguments go here */
			usage(fetch_pack_usage);
		}
		dest = arg;
		heads = argv + i + 1;
		nr_heads = argc - i - 1;
		break;
	}
	if (!dest)
		usage(fetch_pack_usage);
	pid = git_connect(fd, dest, exec);
	if (pid < 0)
		return 1;
	ret = fetch_pack(fd, nr_heads, heads);
	close(fd[0]);
	close(fd[1]);
	finish_connect(pid);
	return ret;
}