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

static const char upload_pack_usage[] = "git-upload-pack <dir>";

#define MAX_HAS (16)
#define MAX_NEEDS (256)
static int nr_has = 0, nr_needs = 0;
static unsigned char has_sha1[MAX_HAS][20];
static unsigned char needs_sha1[MAX_NEEDS][20];

static int strip(char *line, int len)
{
        if (len && line[len-1] == '\n')
                line[--len] = 0;
        return len;
}

static void create_pack_file(void)
{
        int fd[2];
        pid_t pid;

        if (pipe(fd) < 0)
                die("git-upload-pack: unable to create pipe");
        pid = fork();
        if (pid < 0)
                die("git-upload-pack: unable to fork git-rev-list");

        if (!pid) {
                int i;
                int args = nr_has + nr_needs + 5;
                char **argv = xmalloc(args * sizeof(char *));
                char *buf = xmalloc(args * 45);
                char **p = argv;

                dup2(fd[1], 1);
                close(0);
                close(fd[0]);
                close(fd[1]);
                *p++ = "git-rev-list";
                *p++ = "--objects";
                for (i = 0; i < nr_needs; i++) {
                        *p++ = buf;
                        memcpy(buf, sha1_to_hex(needs_sha1[i]), 41);
                        buf += 41;
                }
                for (i = 0; i < nr_has; i++) {
                        *p++ = buf;
                        *buf++ = '^';
                        memcpy(buf, sha1_to_hex(has_sha1[i]), 41);
                        buf += 41;
                }
                *p++ = NULL;
                execvp("git-rev-list", argv);
                die("git-upload-pack: unable to exec git-rev-list");
        }
        dup2(fd[0], 0);
        close(fd[0]);
        close(fd[1]);
        execlp("git-pack-objects", "git-pack-objects", "--stdout", NULL);
        die("git-upload-pack: unable to exec git-pack-objects");
}

static int got_sha1(char *hex, unsigned char *sha1)
{
        int nr;
        if (get_sha1_hex(hex, sha1))
                die("git-upload-pack: expected SHA1 object, got '%s'", hex);
        if (!has_sha1_file(sha1))
                return 0;
        nr = nr_has;
        if (nr < MAX_HAS) {
                memcpy(has_sha1[nr], sha1, 20);
                nr_has = nr+1;
        }
        return 1;
}

static int get_common_commits(void)
{
        static char line[1000];
        unsigned char sha1[20];
        int len;

        for(;;) {
                len = packet_read_line(0, line, sizeof(line));

                if (!len) {
                        packet_write(1, "NAK\n");
                        continue;
                }
                len = strip(line, len);
                if (!strncmp(line, "have ", 5)) {
                        if (got_sha1(line+5, sha1)) {
                                packet_write(1, "ACK %s\n", sha1_to_hex(sha1));
                                break;
                        }
                        continue;
                }
                if (!strcmp(line, "done")) {
                        packet_write(1, "NAK\n");
                        return -1;
                }
                die("git-upload-pack: expected SHA1 list, got '%s'", line);
        }

        for (;;) {
                len = packet_read_line(0, line, sizeof(line));
                if (!len)
                        continue;
                len = strip(line, len);
                if (!strncmp(line, "have ", 5)) {
                        got_sha1(line+5, sha1);
                        continue;
                }
                if (!strcmp(line, "done"))
                        break;
                die("git-upload-pack: expected SHA1 list, got '%s'", line);
        }
        return 0;
}

static int receive_needs(void)
{
        static char line[1000];
        int len, needs;

        needs = 0;
        for (;;) {
                len = packet_read_line(0, line, sizeof(line));
                if (!len)
                        return needs;

                /*
                 * This is purely theoretical right now: git-fetch-pack only
                 * ever asks for a single HEAD
                 */
                if (needs >= MAX_NEEDS)
                        die("I'm only doing a max of %d requests", MAX_NEEDS);
                if (strncmp("want ", line, 5) || get_sha1_hex(line+5, needs_sha1[needs]))
                        die("git-upload-pack: protocol error, expected to get sha, not '%s'", line);
                needs++;
        }
}

static int send_ref(const char *refname, const unsigned char *sha1)
{
        packet_write(1, "%s %s\n", sha1_to_hex(sha1), refname);
        return 0;
}

static int upload_pack(void)
{
        head_ref(send_ref);
        for_each_ref(send_ref);
        packet_flush(1);
        nr_needs = receive_needs();
        if (!nr_needs)
                return 0;
        get_common_commits();
        create_pack_file();
        return 0;
}

int main(int argc, char **argv)
{
        const char *dir;
        if (argc != 2)
                usage(upload_pack_usage);
        dir = argv[1];

        /* chdir to the directory. If that fails, try appending ".git" */
        if (chdir(dir) < 0) {
                if (chdir(mkpath("%s.git", dir)) < 0)
                        die("git-upload-pack unable to chdir to %s", dir);
        }
        chdir(".git");
        if (access("objects", X_OK) || access("refs", X_OK))
                die("git-upload-pack: %s doesn't seem to be a git archive", dir);
        setenv("GIT_DIR", ".", 1);
        upload_pack();
        return 0;
}