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

static char *path_name(struct name_path *path, const char *name)
{
        struct name_path *p;
        char *n, *m;
        int nlen = strlen(name);
        int len = nlen + 1;

        for (p = path; p; p = p->up) {
                if (p->elem_len)
                        len += p->elem_len + 1;
        }
        n = xmalloc(len);
        m = n + len - (nlen + 1);
        strcpy(m, name);
        for (p = path; p; p = p->up) {
                if (p->elem_len) {
                        m -= p->elem_len + 1;
                        memcpy(m, p->elem, p->elem_len);
                        m[p->elem_len] = '/';
                }
        }
        return n;
}

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

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

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

        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;
        }
}

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

        while (parents) {
                struct commit *commit = parents->item;
                if (!(commit->object.flags & UNINTERESTING)) {
                        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 void add_pending_object(struct rev_info *revs, struct object *obj, const char *name)
{
        add_object(obj, &revs->pending_objects, NULL, name);
}

static struct commit *get_commit_reference(struct rev_info *revs, 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 (revs->tag_objects && !(object->flags & UNINTERESTING))
                        add_pending_object(revs, 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);
                        revs->limited = 1;
                }
                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 (!revs->tree_objects)
                        return NULL;
                if (flags & UNINTERESTING) {
                        mark_tree_uninteresting(tree);
                        return NULL;
                }
                add_pending_object(revs, object, "");
                return NULL;
        }

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

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;
}

#define TREE_SAME       0
#define TREE_NEW        1
#define TREE_DIFFERENT  2
static int tree_difference = TREE_SAME;

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

        /*
         * Is it an add of a new file? It means that
         * the old tree didn't have it at all, so we
         * will turn "TREE_SAME" -> "TREE_NEW", but
         * leave any "TREE_DIFFERENT" alone (and if
         * it already was "TREE_NEW", we'll keep it
         * "TREE_NEW" of course).
         */
        if (addremove == '+') {
                diff = tree_difference;
                if (diff != TREE_SAME)
                        return;
                diff = TREE_NEW;
        }
        tree_difference = diff;
}

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)
{
        tree_difference = TREE_DIFFERENT;
}

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

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

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;

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

        return retval >= 0 && !tree_difference;
}

static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
{
        struct commit_list **pp, *parent;

        if (!commit->tree)
                return;

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

        pp = &commit->parents;
        while ((parent = *pp) != NULL) {
                struct commit *p = parent->item;

                if (p->object.flags & UNINTERESTING) {
                        pp = &parent->next;
                        continue;
                }

                parse_commit(p);
                switch (compare_tree(p->tree, commit->tree)) {
                case TREE_SAME:
                        parent->next = NULL;
                        commit->parents = parent;
                        return;

                case TREE_NEW:
                        if (revs->remove_empty_trees && same_tree_as_empty(p->tree)) {
                                *pp = parent->next;
                                continue;
                        }
                /* fallthrough */
                case TREE_DIFFERENT:
                        pp = &parent->next;
                        continue;
                }
                die("bad tree compare for commit %s", sha1_to_hex(commit->object.sha1));
        }
        commit->object.flags |= TREECHANGE;
}

static void add_parents_to_list(struct rev_info *revs, 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. Try to
         * simplify the commit history and find the parent
         * that has no differences in the path set if one exists.
         */
        if (revs->paths)
                try_to_simplify_commit(revs, commit);

        parent = commit->parents;
        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 limit_list(struct rev_info *revs)
{
        struct commit_list *list = revs->commits;
        struct commit_list *newlist = NULL;
        struct commit_list **p = &newlist;

        if (revs->paths)
                diff_tree_setup_paths(revs->paths);

        while (list) {
                struct commit_list *entry = list;
                struct commit *commit = list->item;
                struct object *obj = &commit->object;

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

                if (revs->max_age != -1 && (commit->date < revs->max_age))
                        obj->flags |= UNINTERESTING;
                if (revs->unpacked && has_sha1_pack(obj->sha1))
                        obj->flags |= UNINTERESTING;
                add_parents_to_list(revs, commit, &list);
                if (obj->flags & UNINTERESTING) {
                        mark_parents_uninteresting(commit);
                        if (everybody_uninteresting(list))
                                break;
                        continue;
                }
                if (revs->min_age != -1 && (commit->date > revs->min_age))
                        continue;
                p = &commit_list_insert(commit, p)->next;
        }
        revs->commits = newlist;
}

static void add_one_commit(struct commit *commit, struct rev_info *revs)
{
        if (!commit || (commit->object.flags & SEEN))
                return;
        commit->object.flags |= SEEN;
        commit_list_insert(commit, &revs->commits);
}

static int all_flags;
static struct rev_info *all_revs;

static int handle_one_ref(const char *path, const unsigned char *sha1)
{
        struct commit *commit = get_commit_reference(all_revs, path, sha1, all_flags);
        add_one_commit(commit, all_revs);
        return 0;
}

static void handle_all(struct rev_info *revs, unsigned flags)
{
        all_revs = revs;
        all_flags = flags;
        for_each_ref(handle_one_ref);
}

/*
 * Parse revision information, filling in the "rev_info" structure,
 * and removing the used arguments from the argument list.
 *
 * Returns the number of arguments left that weren't recognized
 * (which are also moved to the head of the argument list)
 */
int setup_revisions(int argc, const char **argv, struct rev_info *revs, const char *def)
{
        int i, flags, seen_dashdash;
        const char **unrecognized = argv + 1;
        int left = 1;

        memset(revs, 0, sizeof(*revs));
        revs->lifo = 1;
        revs->dense = 1;
        revs->prefix = setup_git_directory();
        revs->max_age = -1;
        revs->min_age = -1;
        revs->max_count = -1;

        /* First, search for "--" */
        seen_dashdash = 0;
        for (i = 1; i < argc; i++) {
                const char *arg = argv[i];
                if (strcmp(arg, "--"))
                        continue;
                argv[i] = NULL;
                argc = i;
                revs->paths = get_pathspec(revs->prefix, argv + i + 1);
                seen_dashdash = 1;
                break;
        }

        flags = 0;
        for (i = 1; i < argc; i++) {
                struct commit *commit;
                const char *arg = argv[i];
                unsigned char sha1[20];
                char *dotdot;
                int local_flags;

                if (*arg == '-') {
                        if (!strncmp(arg, "--max-count=", 12)) {
                                revs->max_count = atoi(arg + 12);
                                continue;
                        }
                        /* accept -<digit>, like traditilnal "head" */
                        if ((*arg == '-') && isdigit(arg[1])) {
                                revs->max_count = atoi(arg + 1);
                                continue;
                        }
                        if (!strcmp(arg, "-n")) {
                                if (argc <= i + 1)
                                        die("-n requires an argument");
                                revs->max_count = atoi(argv[++i]);
                                continue;
                        }
                        if (!strncmp(arg,"-n",2)) {
                                revs->max_count = atoi(arg + 2);
                                continue;
                        }
                        if (!strncmp(arg, "--max-age=", 10)) {
                                revs->max_age = atoi(arg + 10);
                                revs->limited = 1;
                                continue;
                        }
                        if (!strncmp(arg, "--min-age=", 10)) {
                                revs->min_age = atoi(arg + 10);
                                revs->limited = 1;
                                continue;
                        }
                        if (!strncmp(arg, "--since=", 8)) {
                                revs->max_age = approxidate(arg + 8);
                                revs->limited = 1;
                                continue;
                        }
                        if (!strncmp(arg, "--after=", 8)) {
                                revs->max_age = approxidate(arg + 8);
                                revs->limited = 1;
                                continue;
                        }
                        if (!strncmp(arg, "--before=", 9)) {
                                revs->min_age = approxidate(arg + 9);
                                revs->limited = 1;
                                continue;
                        }
                        if (!strncmp(arg, "--until=", 8)) {
                                revs->min_age = approxidate(arg + 8);
                                revs->limited = 1;
                                continue;
                        }
                        if (!strcmp(arg, "--all")) {
                                handle_all(revs, flags);
                                continue;
                        }
                        if (!strcmp(arg, "--not")) {
                                flags ^= UNINTERESTING;
                                continue;
                        }
                        if (!strcmp(arg, "--default")) {
                                if (++i >= argc)
                                        die("bad --default argument");
                                def = argv[i];
                                continue;
                        }
                        if (!strcmp(arg, "--topo-order")) {
                                revs->topo_order = 1;
                                revs->limited = 1;
                                continue;
                        }
                        if (!strcmp(arg, "--date-order")) {
                                revs->lifo = 0;
                                revs->topo_order = 1;
                                revs->limited = 1;
                                continue;
                        }
                        if (!strcmp(arg, "--dense")) {
                                revs->dense = 1;
                                continue;
                        }
                        if (!strcmp(arg, "--sparse")) {
                                revs->dense = 0;
                                continue;
                        }
                        if (!strcmp(arg, "--remove-empty")) {
                                revs->remove_empty_trees = 1;
                                continue;
                        }
                        if (!strncmp(arg, "--no-merges", 11)) {
                                revs->no_merges = 1;
                                continue;
                        }
                        if (!strcmp(arg, "--objects")) {
                                revs->tag_objects = 1;
                                revs->tree_objects = 1;
                                revs->blob_objects = 1;
                                continue;
                        }
                        if (!strcmp(arg, "--objects-edge")) {
                                revs->tag_objects = 1;
                                revs->tree_objects = 1;
                                revs->blob_objects = 1;
                                revs->edge_hint = 1;
                                continue;
                        }
                        if (!strcmp(arg, "--unpacked")) {
                                revs->unpacked = 1;
                                revs->limited = 1;
                                continue;
                        }
                        *unrecognized++ = arg;
                        left++;
                        continue;
                }
                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(revs, arg, from_sha1, flags ^ UNINTERESTING);
                                include = get_commit_reference(revs, next, sha1, flags);
                                if (!exclude || !include)
                                        die("Invalid revision range %s..%s", arg, next);
                                add_one_commit(exclude, revs);
                                add_one_commit(include, revs);
                                continue;
                        }
                        *dotdot = '.';
                }
                local_flags = 0;
                if (*arg == '^') {
                        local_flags = UNINTERESTING;
                        arg++;
                }
                if (get_sha1(arg, sha1) < 0) {
                        struct stat st;
                        int j;

                        if (seen_dashdash || local_flags)
                                die("bad revision '%s'", arg);

                        /* If we didn't have a "--", all filenames must exist */
                        for (j = i; j < argc; j++) {
                                if (lstat(argv[j], &st) < 0)
                                        die("'%s': %s", arg, strerror(errno));
                        }
                        revs->paths = get_pathspec(revs->prefix, argv + i);
                        break;
                }
                commit = get_commit_reference(revs, arg, sha1, flags ^ local_flags);
                add_one_commit(commit, revs);
        }
        if (def && !revs->commits) {
                unsigned char sha1[20];
                struct commit *commit;
                if (get_sha1(def, sha1) < 0)
                        die("bad default revision '%s'", def);
                commit = get_commit_reference(revs, def, sha1, 0);
                add_one_commit(commit, revs);
        }
        if (revs->paths)
                revs->limited = 1;
        return left;
}

void prepare_revision_walk(struct rev_info *revs)
{
        sort_by_date(&revs->commits);
        if (revs->limited)
                limit_list(revs);
        if (revs->topo_order)
                sort_in_topological_order(&revs->commits, revs->lifo);
}

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;
        }
}

struct commit *get_revision(struct rev_info *revs)
{
        struct commit_list *list = revs->commits;

        if (!list)
                return NULL;

        /* Check the max_count ... */
        switch (revs->max_count) {
        case -1:
                break;
        case 0:
                return NULL;
        default:
                revs->max_count--;
        }

        do {
                struct commit *commit = revs->commits->item;

                if (commit->object.flags & (UNINTERESTING|SHOWN))
                        goto next;
                if (revs->min_age != -1 && (commit->date > revs->min_age))
                        goto next;
                if (revs->max_age != -1 && (commit->date < revs->max_age))
                        return NULL;
                if (revs->no_merges && commit->parents && commit->parents->next)
                        goto next;
                if (revs->paths && revs->dense) {
                        if (!(commit->object.flags & TREECHANGE))
                                goto next;
                        rewrite_parents(commit);
                }
                /* More to go? */
                if (revs->max_count)
                        pop_most_recent_commit(&revs->commits, SEEN);
                commit->object.flags |= SHOWN;
                return commit;
next:
                pop_most_recent_commit(&revs->commits, SEEN);
        } while (revs->commits);
        return NULL;
}