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

static const char clone_pack_usage[] = "git-clone-pack [host:]directory [heads]*";
static const char *exec = "git-upload-pack";

struct ref {
        struct ref *next;
        unsigned char sha1[20];
        char name[0];
};

static struct ref *get_remote_refs(int fd, int nr_match, char **match)
{
        struct ref *ref_list = NULL, **next_ref = &ref_list;

        for (;;) {
                static char line[1000];
                unsigned char sha1[20];
                struct ref *ref;
                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 '%s¤'", line);
                refname = line+41;
                len = len-40;
                if (nr_match && !path_match(refname, nr_match, match))
                        continue;
                ref = xmalloc(sizeof(struct ref) + len);
                ref->next = NULL;
                memcpy(ref->sha1, sha1, 20);
                memcpy(ref->name, refname, len);
                *next_ref = ref;
                next_ref = &ref->next;
        }
        return ref_list;
}

static void clone_handshake(int fd[2], struct ref *ref)
{
        unsigned char sha1[20];

        while (ref) {
                packet_write(fd[1], "want %s\n", sha1_to_hex(ref->sha1));
                ref = ref->next;
        }
        packet_flush(fd[1]);

        /* We don't have nuttin' */
        packet_write(fd[1], "done\n");
        if (get_ack(fd[0], sha1))
                error("Huh! git-clone-pack got positive ack for %s", sha1_to_hex(sha1));
}

static int is_master(struct ref *ref)
{
        return !strcmp(ref->name, "refs/heads/master");
}

static void write_one_ref(struct ref *ref)
{
        char *path = git_path(ref->name);
        int fd;
        char *hex;

        if (safe_create_leading_directories(path))
                die("unable to create leading directory for %s", ref->name);
        fd = open(path, O_CREAT | O_EXCL | O_WRONLY, 0666);
        if (fd < 0)
                die("unable to create ref %s", ref->name);
        hex = sha1_to_hex(ref->sha1);
        hex[40] = '\n';
        if (write(fd, hex, 41) != 41)
                die("unable to write ref %s", ref->name);
        close(fd);
}

static void write_refs(struct ref *ref)
{
        struct ref *head = NULL, *head_ptr, *master_ref;
        char *head_path;

        if (!strcmp(ref->name, "HEAD")) {
                head = ref;
                ref = ref->next;
        }
        head_ptr = NULL;
        master_ref = NULL;
        while (ref) {
                if (is_master(ref))
                        master_ref = ref;
                if (head && !memcmp(ref->sha1, head->sha1, 20)) {
                        if (!head_ptr || ref == master_ref)
                                head_ptr = ref;
                }
                write_one_ref(ref);
                ref = ref->next;
        }
        if (!head)
                return;

        head_path = git_path("HEAD");
        if (!head_ptr) {
                /*
                 * If we had a master ref, and it wasn't HEAD, we need to undo the
                 * symlink, and write a standalone HEAD. Give a warning, because that's
                 * really really wrong.
                 */
                if (master_ref) {
                        error("HEAD doesn't point to any refs! Making standalone HEAD");
                        unlink(head_path);
                }
                write_one_ref(head);
                return;
        }

        /* We reset to the master branch if it's available */
        if (master_ref)
                return;

        /*
         * Uhhuh. Other end didn't have master. We start HEAD off with
         * the first branch with the same value.
         */
        unlink(head_path);
        if (symlink(head_ptr->name, head_path) < 0)
                die("unable to link HEAD to %s", head_ptr->name);
}

static int clone_pack(int fd[2], int nr_match, char **match)
{
        struct ref *refs;
        int status;
        pid_t pid;

        refs = get_remote_refs(fd[0], nr_match, match);
        if (!refs) {
                packet_flush(fd[1]);
                die("no matching remote head");
        }
        clone_handshake(fd, refs);
        pid = fork();
        if (pid < 0)
                die("git-clone-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);
                write_refs(refs);
                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(clone_pack_usage);
                }
                dest = arg;
                heads = argv + i + 1;
                nr_heads = argc - i - 1;
                break;
        }
        if (!dest)
                usage(clone_pack_usage);
        pid = git_connect(fd, dest, exec);
        if (pid < 0)
                return 1;
        ret = clone_pack(fd, nr_heads, heads);
        close(fd[0]);
        close(fd[1]);
        finish_connect(pid);
        return ret;
}