#include "cache.h"
#include "refs.h"
#include "pkt-line.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;

        packet_write(fd[1], "want %s\n", sha1_to_hex(remote));
        packet_flush(fd[1]);
        while (fgets(line, sizeof(line), stdin) != 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))
                                return 0;
                        flushes--;
                }
        }
        flushes++;
        packet_flush(fd[1]);
        while (flushes) {
                flushes--;
                if (get_ack(fd[0], result_sha1))
                        return 0;
        }
        return -1;
}

static int get_old_sha1(const char *refname, unsigned char *sha1)
{
        static char pathname[PATH_MAX];
        const char *git_dir;
        int fd, ret;

        git_dir = gitenv(GIT_DIR_ENVIRONMENT) ? : DEFAULT_GIT_DIR_ENVIRONMENT;
        snprintf(pathname, sizeof(pathname), "%s/%s", git_dir, refname);
        fd = open(pathname, 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)) {
                printf("%s: unchanged\n", refname);
                return 0;
        }
        
        memcpy(oldhex, sha1_to_hex(mysha1), 41);
        printf("%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;

        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");
        close(fd[1]);
        dup2(fd[0], 0);
        close(fd[0]);
        execlp("git-unpack-objects", "git-unpack-objects", NULL);
        die("git-unpack-objects exec failed");
}

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;
}