#include "cache.h"
#include "refs.h"
#include "tag.h"
#include "commit.h"
#include "tree.h"
#include "blob.h"
#include "epoch.h"
#include "diff.h"

#define SEEN            (1u << 0)
#define INTERESTING     (1u << 1)
#define COUNTED         (1u << 2)
#define SHOWN           (1u << 3)
#define TREECHANGE      (1u << 4)

static const char rev_list_usage[] =
"git-rev-list [OPTION] <commit-id>... [ -- paths... ]\n"
"  limiting output:\n"
"    --max-count=nr\n"
"    --max-age=epoch\n"
"    --min-age=epoch\n"
"    --sparse\n"
"    --no-merges\n"
"    --all\n"
"  ordering output:\n"
"    --merge-order [ --show-breaks ]\n"
"    --topo-order\n"
"  formatting output:\n"
"    --parents\n"
"    --objects\n"
"    --unpacked\n"
"    --header | --pretty\n"
"  special purpose:\n"
"    --bisect"
;

static int dense = 1;
static int unpacked = 0;
static int bisect_list = 0;
static int tag_objects = 0;
static int tree_objects = 0;
static int blob_objects = 0;
static int verbose_header = 0;
static int show_parents = 0;
static int hdr_termination = 0;
static const char *commit_prefix = "";
static unsigned long max_age = -1;
static unsigned long min_age = -1;
static int max_count = -1;
static enum cmit_fmt commit_format = CMIT_FMT_RAW;
static int merge_order = 0;
static int show_breaks = 0;
static int stop_traversal = 0;
static int topo_order = 0;
static int no_merges = 0;
static const char **paths = NULL;

static void show_commit(struct commit *commit)
{
        commit->object.flags |= SHOWN;
        if (show_breaks) {
                commit_prefix = "| ";
                if (commit->object.flags & DISCONTINUITY) {
                        commit_prefix = "^ ";     
                } else if (commit->object.flags & BOUNDARY) {
                        commit_prefix = "= ";
                } 
        }                       
        printf("%s%s", commit_prefix, sha1_to_hex(commit->object.sha1));
        if (show_parents) {
                struct commit_list *parents = commit->parents;
                while (parents) {
                        printf(" %s", sha1_to_hex(parents->item->object.sha1));
                        parents = parents->next;
                }
        }
        if (commit_format == CMIT_FMT_ONELINE)
                putchar(' ');
        else
                putchar('\n');

        if (verbose_header) {
                static char pretty_header[16384];
                pretty_print_commit(commit_format, commit->buffer, ~0, pretty_header, sizeof(pretty_header));
                printf("%s%c", pretty_header, hdr_termination);
        }
        fflush(stdout);
}

static int rewrite_one(struct commit **pp)
{
        for (;;) {
                struct commit *p = *pp;
                if (p->object.flags & (TREECHANGE | UNINTERESTING))
                        return 0;
                if (!p->parents)
                        return -1;
                *pp = p->parents->item;
        }
}

static void rewrite_parents(struct commit *commit)
{
        struct commit_list **pp = &commit->parents;
        while (*pp) {
                struct commit_list *parent = *pp;
                if (rewrite_one(&parent->item) < 0) {
                        *pp = parent->next;
                        continue;
                }
                pp = &parent->next;
        }
}

static int filter_commit(struct commit * commit)
{
        if (stop_traversal && (commit->object.flags & BOUNDARY))
                return STOP;
        if (commit->object.flags & (UNINTERESTING|SHOWN))
                return CONTINUE;
        if (min_age != -1 && (commit->date > min_age))
                return CONTINUE;
        if (max_age != -1 && (commit->date < max_age)) {
                stop_traversal=1;
                return CONTINUE;
        }
        if (no_merges && (commit->parents && commit->parents->next))
                return CONTINUE;
        if (paths && dense) {
                if (!(commit->object.flags & TREECHANGE))
                        return CONTINUE;
                rewrite_parents(commit);
        }
        return DO;
}

static int process_commit(struct commit * commit)
{
        int action=filter_commit(commit);

        if (action == STOP) {
                return STOP;
        }

        if (action == CONTINUE) {
                return CONTINUE;
        }

        if (max_count != -1 && !max_count--)
                return STOP;

        show_commit(commit);

        return CONTINUE;
}

static struct object_list **add_object(struct object *obj, struct object_list **p, const char *name)
{
        struct object_list *entry = xmalloc(sizeof(*entry));
        entry->item = obj;
        entry->next = *p;
        entry->name = name;
        *p = entry;
        return &entry->next;
}

static struct object_list **process_blob(struct blob *blob, struct object_list **p, const char *name)
{
        struct object *obj = &blob->object;

        if (!blob_objects)
                return p;
        if (obj->flags & (UNINTERESTING | SEEN))
                return p;
        obj->flags |= SEEN;
        return add_object(obj, p, name);
}

static struct object_list **process_tree(struct tree *tree, struct object_list **p, const char *name)
{
        struct object *obj = &tree->object;
        struct tree_entry_list *entry;

        if (!tree_objects)
                return p;
        if (obj->flags & (UNINTERESTING | SEEN))
                return p;
        if (parse_tree(tree) < 0)
                die("bad tree object %s", sha1_to_hex(obj->sha1));
        obj->flags |= SEEN;
        p = add_object(obj, p, name);
        entry = tree->entries;
        tree->entries = NULL;
        while (entry) {
                struct tree_entry_list *next = entry->next;
                if (entry->directory)
                        p = process_tree(entry->item.tree, p, entry->name);
                else
                        p = process_blob(entry->item.blob, p, entry->name);
                free(entry);
                entry = next;
        }
        return p;
}

static struct object_list *pending_objects = NULL;

static void show_commit_list(struct commit_list *list)
{
        struct object_list *objects = NULL, **p = &objects, *pending;
        while (list) {
                struct commit *commit = pop_most_recent_commit(&list, SEEN);

                p = process_tree(commit->tree, p, "");
                if (process_commit(commit) == STOP)
                        break;
        }
        for (pending = pending_objects; pending; pending = pending->next) {
                struct object *obj = pending->item;
                const char *name = pending->name;
                if (obj->flags & (UNINTERESTING | SEEN))
                        continue;
                if (obj->type == tag_type) {
                        obj->flags |= SEEN;
                        p = add_object(obj, p, name);
                        continue;
                }
                if (obj->type == tree_type) {
                        p = process_tree((struct tree *)obj, p, name);
                        continue;
                }
                if (obj->type == blob_type) {
                        p = process_blob((struct blob *)obj, p, name);
                        continue;
                }
                die("unknown pending object %s (%s)", sha1_to_hex(obj->sha1), name);
        }
        while (objects) {
                /* An object with name "foo\n0000000000000000000000000000000000000000"
                 * can be used confuse downstream git-pack-objects very badly.
                 */
                const char *ep = strchr(objects->name, '\n');
                if (ep) {
                        printf("%s %.*s\n", sha1_to_hex(objects->item->sha1),
                               (int) (ep - objects->name),
                               objects->name);
                }
                else
                        printf("%s %s\n", sha1_to_hex(objects->item->sha1), objects->name);
                objects = objects->next;
        }
}

static void mark_blob_uninteresting(struct blob *blob)
{
        if (!blob_objects)
                return;
        if (blob->object.flags & UNINTERESTING)
                return;
        blob->object.flags |= UNINTERESTING;
}

static void mark_tree_uninteresting(struct tree *tree)
{
        struct object *obj = &tree->object;
        struct tree_entry_list *entry;

        if (!tree_objects)
                return;
        if (obj->flags & UNINTERESTING)
                return;
        obj->flags |= UNINTERESTING;
        if (!has_sha1_file(obj->sha1))
                return;
        if (parse_tree(tree) < 0)
                die("bad tree %s", sha1_to_hex(obj->sha1));
        entry = tree->entries;
        tree->entries = NULL;
        while (entry) {
                struct tree_entry_list *next = entry->next;
                if (entry->directory)
                        mark_tree_uninteresting(entry->item.tree);
                else
                        mark_blob_uninteresting(entry->item.blob);
                free(entry);
                entry = next;
        }
}

static void mark_parents_uninteresting(struct commit *commit)
{
        struct commit_list *parents = commit->parents;

        while (parents) {
                struct commit *commit = parents->item;
                commit->object.flags |= UNINTERESTING;

                /*
                 * Normally we haven't parsed the parent
                 * yet, so we won't have a parent of a parent
                 * here. However, it may turn out that we've
                 * reached this commit some other way (where it
                 * wasn't uninteresting), in which case we need
                 * to mark its parents recursively too..
                 */
                if (commit->parents)
                        mark_parents_uninteresting(commit);

                /*
                 * A missing commit is ok iff its parent is marked 
                 * uninteresting.
                 *
                 * We just mark such a thing parsed, so that when
                 * it is popped next time around, we won't be trying
                 * to parse it and get an error.
                 */
                if (!has_sha1_file(commit->object.sha1))
                        commit->object.parsed = 1;
                parents = parents->next;
        }
}

static int everybody_uninteresting(struct commit_list *orig)
{
        struct commit_list *list = orig;
        while (list) {
                struct commit *commit = list->item;
                list = list->next;
                if (commit->object.flags & UNINTERESTING)
                        continue;
                return 0;
        }
        return 1;
}

/*
 * This is a truly stupid algorithm, but it's only
 * used for bisection, and we just don't care enough.
 *
 * We care just barely enough to avoid recursing for
 * non-merge entries.
 */
static int count_distance(struct commit_list *entry)
{
        int nr = 0;

        while (entry) {
                struct commit *commit = entry->item;
                struct commit_list *p;

                if (commit->object.flags & (UNINTERESTING | COUNTED))
                        break;
                nr++;
                commit->object.flags |= COUNTED;
                p = commit->parents;
                entry = p;
                if (p) {
                        p = p->next;
                        while (p) {
                                nr += count_distance(p);
                                p = p->next;
                        }
                }
        }
        return nr;
}

static void clear_distance(struct commit_list *list)
{
        while (list) {
                struct commit *commit = list->item;
                commit->object.flags &= ~COUNTED;
                list = list->next;
        }
}

static struct commit_list *find_bisection(struct commit_list *list)
{
        int nr, closest;
        struct commit_list *p, *best;

        nr = 0;
        p = list;
        while (p) {
                nr++;
                p = p->next;
        }
        closest = 0;
        best = list;

        p = list;
        while (p) {
                int distance = count_distance(p);
                clear_distance(list);
                if (nr - distance < distance)
                        distance = nr - distance;
                if (distance > closest) {
                        best = p;
                        closest = distance;
                }
                p = p->next;
        }
        if (best)
                best->next = NULL;
        return best;
}

static void mark_edges_uninteresting(struct commit_list *list)
{
        for ( ; list; list = list->next) {
                struct commit_list *parents = list->item->parents;

                for ( ; parents; parents = parents->next) {
                        struct commit *commit = parents->item;
                        if (commit->object.flags & UNINTERESTING)
                                mark_tree_uninteresting(commit->tree);
                }
        }
}

static int is_different = 0;

static void file_add_remove(struct diff_options *options,
                    int addremove, unsigned mode,
                    const unsigned char *sha1,
                    const char *base, const char *path)
{
        is_different = 1;
}

static void file_change(struct diff_options *options,
                 unsigned old_mode, unsigned new_mode,
                 const unsigned char *old_sha1,
                 const unsigned char *new_sha1,
                 const char *base, const char *path)
{
        is_different = 1;
}

static struct diff_options diff_opt = {
        .recursive = 1,
        .add_remove = file_add_remove,
        .change = file_change,
};

static int same_tree(struct tree *t1, struct tree *t2)
{
        is_different = 0;
        if (diff_tree_sha1(t1->object.sha1, t2->object.sha1, "", &diff_opt) < 0)
                return 0;
        return !is_different;
}

static int same_tree_as_empty(struct tree *t1)
{
        int retval;
        void *tree;
        struct tree_desc empty, real;

        if (!t1)
                return 0;

        tree = read_object_with_reference(t1->object.sha1, "tree", &real.size, NULL);
        if (!tree)
                return 0;
        real.buf = tree;

        empty.buf = "";
        empty.size = 0;

        is_different = 0;
        retval = diff_tree(&empty, &real, "", &diff_opt);
        free(tree);

        return retval >= 0 && !is_different;
}

static struct commit *try_to_simplify_merge(struct commit *commit, struct commit_list *parent)
{
        if (!commit->tree)
                return NULL;

        while (parent) {
                struct commit *p = parent->item;
                parent = parent->next;
                parse_commit(p);
                if (!p->tree)
                        continue;
                if (same_tree(commit->tree, p->tree))
                        return p;
        }
        return NULL;
}

static void add_parents_to_list(struct commit *commit, struct commit_list **list)
{
        struct commit_list *parent = commit->parents;

        /*
         * If the commit is uninteresting, don't try to
         * prune parents - we want the maximal uninteresting
         * set.
         *
         * Normally we haven't parsed the parent
         * yet, so we won't have a parent of a parent
         * here. However, it may turn out that we've
         * reached this commit some other way (where it
         * wasn't uninteresting), in which case we need
         * to mark its parents recursively too..
         */
        if (commit->object.flags & UNINTERESTING) {
                while (parent) {
                        struct commit *p = parent->item;
                        parent = parent->next;
                        parse_commit(p);
                        p->object.flags |= UNINTERESTING;
                        if (p->parents)
                                mark_parents_uninteresting(p);
                        if (p->object.flags & SEEN)
                                continue;
                        p->object.flags |= SEEN;
                        insert_by_date(p, list);
                }
                return;
        }

        /*
         * Ok, the commit wasn't uninteresting. If it
         * is a merge, try to find the parent that has
         * no differences in the path set if one exists.
         */
        if (paths && parent && parent->next) {
                struct commit *preferred;

                preferred = try_to_simplify_merge(commit, parent);
                if (preferred) {
                        parent->item = preferred;
                        parent->next = NULL;
                }
        }

        while (parent) {
                struct commit *p = parent->item;

                parent = parent->next;

                parse_commit(p);
                if (p->object.flags & SEEN)
                        continue;
                p->object.flags |= SEEN;
                insert_by_date(p, list);
        }
}

static void compress_list(struct commit_list *list)
{
        while (list) {
                struct commit *commit = list->item;
                struct commit_list *parent = commit->parents;
                list = list->next;

                if (!parent) {
                        if (!same_tree_as_empty(commit->tree))
                                commit->object.flags |= TREECHANGE;
                        continue;
                }

                /*
                 * Exactly one parent? Check if it leaves the tree
                 * unchanged
                 */
                if (!parent->next) {
                        struct tree *t1 = commit->tree;
                        struct tree *t2 = parent->item->tree;
                        if (!t1 || !t2 || same_tree(t1, t2))
                                continue;
                }
                commit->object.flags |= TREECHANGE;
        }
}

static struct commit_list *limit_list(struct commit_list *list)
{
        struct commit_list *newlist = NULL;
        struct commit_list **p = &newlist;
        while (list) {
                struct commit_list *entry = list;
                struct commit *commit = list->item;
                struct object *obj = &commit->object;

                list = list->next;
                free(entry);

                if (max_age != -1 && (commit->date < max_age))
                        obj->flags |= UNINTERESTING;
                if (unpacked && has_sha1_pack(obj->sha1))
                        obj->flags |= UNINTERESTING;
                add_parents_to_list(commit, &list);
                if (obj->flags & UNINTERESTING) {
                        mark_parents_uninteresting(commit);
                        if (everybody_uninteresting(list))
                                break;
                        continue;
                }
                if (min_age != -1 && (commit->date > min_age))
                        continue;
                p = &commit_list_insert(commit, p)->next;
        }
        if (tree_objects)
                mark_edges_uninteresting(newlist);
        if (paths && dense)
                compress_list(newlist);
        if (bisect_list)
                newlist = find_bisection(newlist);
        return newlist;
}

static void add_pending_object(struct object *obj, const char *name)
{
        add_object(obj, &pending_objects, name);
}

static struct commit *get_commit_reference(const char *name, const unsigned char *sha1, unsigned int flags)
{
        struct object *object;

        object = parse_object(sha1);
        if (!object)
                die("bad object %s", name);

        /*
         * Tag object? Look what it points to..
         */
        while (object->type == tag_type) {
                struct tag *tag = (struct tag *) object;
                object->flags |= flags;
                if (tag_objects && !(object->flags & UNINTERESTING))
                        add_pending_object(object, tag->tag);
                object = parse_object(tag->tagged->sha1);
                if (!object)
                        die("bad object %s", sha1_to_hex(tag->tagged->sha1));
        }

        /*
         * Commit object? Just return it, we'll do all the complex
         * reachability crud.
         */
        if (object->type == commit_type) {
                struct commit *commit = (struct commit *)object;
                object->flags |= flags;
                if (parse_commit(commit) < 0)
                        die("unable to parse commit %s", name);
                if (flags & UNINTERESTING)
                        mark_parents_uninteresting(commit);
                return commit;
        }

        /*
         * Tree object? Either mark it uniniteresting, or add it
         * to the list of objects to look at later..
         */
        if (object->type == tree_type) {
                struct tree *tree = (struct tree *)object;
                if (!tree_objects)
                        return NULL;
                if (flags & UNINTERESTING) {
                        mark_tree_uninteresting(tree);
                        return NULL;
                }
                add_pending_object(object, "");
                return NULL;
        }

        /*
         * Blob object? You know the drill by now..
         */
        if (object->type == blob_type) {
                struct blob *blob = (struct blob *)object;
                if (!blob_objects)
                        return NULL;
                if (flags & UNINTERESTING) {
                        mark_blob_uninteresting(blob);
                        return NULL;
                }
                add_pending_object(object, "");
                return NULL;
        }
        die("%s is unknown object", name);
}

static void handle_one_commit(struct commit *com, struct commit_list **lst)
{
        if (!com || com->object.flags & SEEN)
                return;
        com->object.flags |= SEEN;
        commit_list_insert(com, lst);
}

/* for_each_ref() callback does not allow user data -- Yuck. */
static struct commit_list **global_lst;

static int include_one_commit(const char *path, const unsigned char *sha1)
{
        struct commit *com = get_commit_reference(path, sha1, 0);
        handle_one_commit(com, global_lst);
        return 0;
}

static void handle_all(struct commit_list **lst)
{
        global_lst = lst;
        for_each_ref(include_one_commit);
        global_lst = NULL;
}

int main(int argc, const char **argv)
{
        const char *prefix = setup_git_directory();
        struct commit_list *list = NULL;
        int i, limited = 0;

        for (i = 1 ; i < argc; i++) {
                int flags;
                const char *arg = argv[i];
                char *dotdot;
                struct commit *commit;
                unsigned char sha1[20];

                if (!strncmp(arg, "--max-count=", 12)) {
                        max_count = atoi(arg + 12);
                        continue;
                }
                if (!strncmp(arg, "--max-age=", 10)) {
                        max_age = atoi(arg + 10);
                        limited = 1;
                        continue;
                }
                if (!strncmp(arg, "--min-age=", 10)) {
                        min_age = atoi(arg + 10);
                        limited = 1;
                        continue;
                }
                if (!strcmp(arg, "--header")) {
                        verbose_header = 1;
                        continue;
                }
                if (!strncmp(arg, "--pretty", 8)) {
                        commit_format = get_commit_format(arg+8);
                        verbose_header = 1;
                        hdr_termination = '\n';
                        if (commit_format == CMIT_FMT_ONELINE)
                                commit_prefix = "";
                        else
                                commit_prefix = "commit ";
                        continue;
                }
                if (!strncmp(arg, "--no-merges", 11)) {
                        no_merges = 1;
                        continue;
                }
                if (!strcmp(arg, "--parents")) {
                        show_parents = 1;
                        continue;
                }
                if (!strcmp(arg, "--bisect")) {
                        bisect_list = 1;
                        continue;
                }
                if (!strcmp(arg, "--all")) {
                        handle_all(&list);
                        continue;
                }
                if (!strcmp(arg, "--objects")) {
                        tag_objects = 1;
                        tree_objects = 1;
                        blob_objects = 1;
                        continue;
                }
                if (!strcmp(arg, "--unpacked")) {
                        unpacked = 1;
                        limited = 1;
                        continue;
                }
                if (!strcmp(arg, "--merge-order")) {
                        merge_order = 1;
                        continue;
                }
                if (!strcmp(arg, "--show-breaks")) {
                        show_breaks = 1;
                        continue;
                }
                if (!strcmp(arg, "--topo-order")) {
                        topo_order = 1;
                        limited = 1;
                        continue;
                }
                if (!strcmp(arg, "--dense")) {
                        dense = 1;
                        continue;
                }
                if (!strcmp(arg, "--sparse")) {
                        dense = 0;
                        continue;
                }
                if (!strcmp(arg, "--")) {
                        i++;
                        break;
                }

                if (show_breaks && !merge_order)
                        usage(rev_list_usage);

                flags = 0;
                dotdot = strstr(arg, "..");
                if (dotdot) {
                        unsigned char from_sha1[20];
                        char *next = dotdot + 2;
                        *dotdot = 0;
                        if (!*next)
                                next = "HEAD";
                        if (!get_sha1(arg, from_sha1) && !get_sha1(next, sha1)) {
                                struct commit *exclude;
                                struct commit *include;
                                
                                exclude = get_commit_reference(arg, from_sha1, UNINTERESTING);
                                include = get_commit_reference(next, sha1, 0);
                                if (!exclude || !include)
                                        die("Invalid revision range %s..%s", arg, next);
                                limited = 1;
                                handle_one_commit(exclude, &list);
                                handle_one_commit(include, &list);
                                continue;
                        }
                        *dotdot = '.';
                }
                if (*arg == '^') {
                        flags = UNINTERESTING;
                        arg++;
                        limited = 1;
                }
                if (get_sha1(arg, sha1) < 0)
                        break;
                commit = get_commit_reference(arg, sha1, flags);
                handle_one_commit(commit, &list);
        }

        if (!list)
                usage(rev_list_usage);

        paths = get_pathspec(prefix, argv + i);
        if (paths) {
                limited = 1;
                diff_tree_setup_paths(paths);
        }

        save_commit_buffer = verbose_header;
        track_object_refs = 0;

        if (!merge_order) {             
                sort_by_date(&list);
                if (list && !limited && max_count == 1 &&
                    !tag_objects && !tree_objects && !blob_objects) {
                        show_commit(list->item);
                        return 0;
                }
                if (limited)
                        list = limit_list(list);
                if (topo_order)
                        sort_in_topological_order(&list);
                show_commit_list(list);
        } else {
#ifndef NO_OPENSSL
                if (sort_list_in_merge_order(list, &process_commit)) {
                        die("merge order sort failed\n");
                }
#else
                die("merge order sort unsupported, OpenSSL not linked");
#endif
        }

        return 0;
}