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

static int quiet;
static int verbose;
static const char fetch_pack_usage[] =
"git-fetch-pack [-q] [-v] [--exec=upload-pack] [host:]directory <refs>...";
static const char *exec = "git-upload-pack";

#define COMPLETE        (1U << 0)
#define COMMON          (1U << 1)
#define COMMON_REF      (1U << 2 | COMMON)
#define SEEN            (1U << 3)
#define POPPED          (1U << 4)

static struct commit_list *rev_list = NULL;
static struct commit_list *rev_list_end = NULL;
static unsigned long non_common_revs = 0;

static void rev_list_append(struct commit *commit, int mark)
{
        if (!(commit->object.flags & mark)) {
                commit->object.flags |= mark;

                if (rev_list == NULL) {
                        commit_list_insert(commit, &rev_list);
                        rev_list_end = rev_list;
                } else {
                        commit_list_insert(commit, &(rev_list_end->next));
                        rev_list_end = rev_list_end->next;
                }

                if (!(commit->object.flags & COMMON))
                        non_common_revs++;
        }
}

static int rev_list_append_sha1(const char *path, const unsigned char *sha1)
{
        struct object *o = deref_tag(parse_object(sha1));

        if (o->type == commit_type)
                rev_list_append((struct commit *)o, SEEN);

        return 0;
}

static void mark_common(struct commit *commit)
{
        if (commit != NULL && !(commit->object.flags & COMMON)) {
                struct object *o = (struct object *)commit;
                o->flags |= COMMON;
                if (!(o->flags & SEEN))
                        rev_list_append(commit, SEEN);
                else {
                        struct commit_list *parents;

                        if (!(o->flags & POPPED))
                                non_common_revs--;
                        if (!o->parsed)
                                parse_commit(commit);
                        for (parents = commit->parents;
                                        parents;
                                        parents = parents->next)
                                mark_common(parents->item);
                }
        }
}

/*
  Get the next rev to send, ignoring the common.
*/

static const unsigned char* get_rev()
{
        struct commit *commit = NULL;

        while (commit == NULL) {
                unsigned int mark;
                struct commit_list* parents;

                if (rev_list == NULL || non_common_revs == 0)
                        return NULL;

                commit = rev_list->item;
                if (!(commit->object.parsed))
                        parse_commit(commit);
                commit->object.flags |= POPPED;
                if (!(commit->object.flags & COMMON))
                        non_common_revs--;
        
                parents = commit->parents;

                if (commit->object.flags & COMMON) {
                        /* do not send "have", and ignore ancestors */
                        commit = NULL;
                        mark = COMMON | SEEN;
                } else if (commit->object.flags & COMMON_REF)
                        /* send "have", and ignore ancestors */
                        mark = COMMON | SEEN;
                else
                        /* send "have", also for its ancestors */
                        mark = SEEN;

                while (parents) {
                        if (mark & COMMON)
                                mark_common(parents->item);
                        else
                                rev_list_append(parents->item, mark);
                        parents = parents->next;
                }

                rev_list = rev_list->next;
        }

        return commit->object.sha1;
}

static int find_common(int fd[2], unsigned char *result_sha1,
                       struct ref *refs)
{
        int fetching;
        int count = 0, flushes = 0, retval;
        const unsigned char *sha1;

        for_each_ref(rev_list_append_sha1);

        fetching = 0;
        for ( ; refs ; refs = refs->next) {
                unsigned char *remote = refs->old_sha1;
                struct object *o;

                /*
                 * If that object is complete (i.e. it is an ancestor of a
                 * local ref), we tell them we have it but do not have to
                 * tell them about its ancestors, which they already know
                 * about.
                 *
                 * We use lookup_object here because we are only
                 * interested in the case we *know* the object is
                 * reachable and we have already scanned it.
                 */
                if (((o = lookup_object(remote)) != NULL) &&
                    (o->flags & COMPLETE)) {
                        o = deref_tag(o);

                        if (o->type == commit_type)
                                rev_list_append((struct commit *)o,
                                                COMMON_REF | SEEN);

                        continue;
                }

                packet_write(fd[1], "want %s\n", sha1_to_hex(remote));
                fetching++;
        }
        packet_flush(fd[1]);
        if (!fetching)
                return 1;

        flushes = 1;
        retval = -1;
        while ((sha1 = get_rev())) {
                packet_write(fd[1], "have %s\n", sha1_to_hex(sha1));
                if (verbose)
                        fprintf(stderr, "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;
                                if (verbose)
                                        fprintf(stderr, "got ack\n");
                                break;
                        }
                        flushes--;
                }
        }
        packet_write(fd[1], "done\n");
        if (verbose)
                fprintf(stderr, "done\n");
        while (flushes) {
                flushes--;
                if (get_ack(fd[0], result_sha1)) {
                        if (verbose)
                                fprintf(stderr, "got ack\n");
                        return 0;
                }
        }
        return retval;
}

static struct commit_list *complete = NULL;

static int mark_complete(const char *path, const unsigned char *sha1)
{
        struct object *o = parse_object(sha1);

        while (o && o->type == tag_type) {
                struct tag *t = (struct tag *) o;
                if (!t->tagged)
                        break; /* broken repository */
                o->flags |= COMPLETE;
                o = parse_object(t->tagged->sha1);
        }
        if (o && o->type == commit_type) {
                struct commit *commit = (struct commit *)o;
                commit->object.flags |= COMPLETE;
                insert_by_date(commit, &complete);
        }
        return 0;
}

static void mark_recent_complete_commits(unsigned long cutoff)
{
        while (complete && cutoff <= complete->item->date) {
                if (verbose)
                        fprintf(stderr, "Marking %s as complete\n",
                                sha1_to_hex(complete->item->object.sha1));
                pop_most_recent_commit(&complete, COMPLETE);
        }
}

static int everything_local(struct ref *refs)
{
        struct ref *ref;
        int retval;
        unsigned long cutoff = 0;

        track_object_refs = 0;
        save_commit_buffer = 0;

        for (ref = refs; ref; ref = ref->next) {
                struct object *o;

                o = parse_object(ref->old_sha1);
                if (!o)
                        continue;

                /* We already have it -- which may mean that we were
                 * in sync with the other side at some time after
                 * that (it is OK if we guess wrong here).
                 */
                if (o->type == commit_type) {
                        struct commit *commit = (struct commit *)o;
                        if (!cutoff || cutoff < commit->date)
                                cutoff = commit->date;
                }
        }

        for_each_ref(mark_complete);
        if (cutoff)
                mark_recent_complete_commits(cutoff);

        for (retval = 1; refs ; refs = refs->next) {
                const unsigned char *remote = refs->old_sha1;
                unsigned char local[20];
                struct object *o;

                o = parse_object(remote);
                if (!o || !(o->flags & COMPLETE)) {
                        retval = 0;
                        if (!verbose)
                                continue;
                        fprintf(stderr,
                                "want %s (%s)\n", sha1_to_hex(remote),
                                refs->name);
                        continue;
                }

                memcpy(refs->new_sha1, local, 20);
                if (!verbose)
                        continue;
                fprintf(stderr,
                        "already have %s (%s)\n", sha1_to_hex(remote),
                        refs->name);
        }
        return retval;
}

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

        get_remote_heads(fd[0], &ref, nr_match, match, 1);
        if (!ref) {
                packet_flush(fd[1]);
                die("no matching remote head");
        }
        if (everything_local(ref)) {
                packet_flush(fd[1]);
                goto all_done;
        }
        if (find_common(fd, sha1, ref) < 0)
                fprintf(stderr, "warning: no common commits\n");
        pid = fork();
        if (pid < 0)
                die("git-fetch-pack: unable to fork off git-unpack-objects");
        if (!pid) {
                dup2(fd[0], 0);
                close(fd[0]);
                close(fd[1]);
                execlp("git-unpack-objects", "git-unpack-objects",
                       quiet ? "-q" : NULL, 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);
all_done:
                while (ref) {
                        printf("%s %s\n",
                               sha1_to_hex(ref->old_sha1), ref->name);
                        ref = ref->next;
                }
                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 == '-') {
                        if (!strncmp("--exec=", arg, 7)) {
                                exec = arg + 7;
                                continue;
                        }
                        if (!strcmp("-q", arg)) {
                                quiet = 1;
                                continue;
                        }
                        if (!strcmp("-v", arg)) {
                                verbose = 1;
                                continue;
                        }
                        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;
}