#include "cache.h"
#include "refs.h"
#include "cache-tree.h"
#include "blame.h"

void blame_origin_decref(struct blame_origin *o)
{
        if (o && --o->refcnt <= 0) {
                struct blame_origin *p, *l = NULL;
                if (o->previous)
                        blame_origin_decref(o->previous);
                free(o->file.ptr);
                /* Should be present exactly once in commit chain */
                for (p = o->commit->util; p; l = p, p = p->next) {
                        if (p == o) {
                                if (l)
                                        l->next = p->next;
                                else
                                        o->commit->util = p->next;
                                free(o);
                                return;
                        }
                }
                die("internal error in blame_origin_decref");
        }
}

/*
 * Given a commit and a path in it, create a new origin structure.
 * The callers that add blame to the scoreboard should use
 * get_origin() to obtain shared, refcounted copy instead of calling
 * this function directly.
 */
static struct blame_origin *make_origin(struct commit *commit, const char *path)
{
        struct blame_origin *o;
        FLEX_ALLOC_STR(o, path, path);
        o->commit = commit;
        o->refcnt = 1;
        o->next = commit->util;
        commit->util = o;
        return o;
}

/*
 * Locate an existing origin or create a new one.
 * This moves the origin to front position in the commit util list.
 */
struct blame_origin *get_origin(struct commit *commit, const char *path)
{
        struct blame_origin *o, *l;

        for (o = commit->util, l = NULL; o; l = o, o = o->next) {
                if (!strcmp(o->path, path)) {
                        /* bump to front */
                        if (l) {
                                l->next = o->next;
                                o->next = commit->util;
                                commit->util = o;
                        }
                        return blame_origin_incref(o);
                }
        }
        return make_origin(commit, path);
}



static void verify_working_tree_path(struct commit *work_tree, const char *path)
{
        struct commit_list *parents;
        int pos;

        for (parents = work_tree->parents; parents; parents = parents->next) {
                const struct object_id *commit_oid = &parents->item->object.oid;
                struct object_id blob_oid;
                unsigned mode;

                if (!get_tree_entry(commit_oid->hash, path, blob_oid.hash, &mode) &&
                    sha1_object_info(blob_oid.hash, NULL) == OBJ_BLOB)
                        return;
        }

        pos = cache_name_pos(path, strlen(path));
        if (pos >= 0)
                ; /* path is in the index */
        else if (-1 - pos < active_nr &&
                 !strcmp(active_cache[-1 - pos]->name, path))
                ; /* path is in the index, unmerged */
        else
                die("no such path '%s' in HEAD", path);
}

static struct commit_list **append_parent(struct commit_list **tail, const struct object_id *oid)
{
        struct commit *parent;

        parent = lookup_commit_reference(oid->hash);
        if (!parent)
                die("no such commit %s", oid_to_hex(oid));
        return &commit_list_insert(parent, tail)->next;
}

static void append_merge_parents(struct commit_list **tail)
{
        int merge_head;
        struct strbuf line = STRBUF_INIT;

        merge_head = open(git_path_merge_head(), O_RDONLY);
        if (merge_head < 0) {
                if (errno == ENOENT)
                        return;
                die("cannot open '%s' for reading", git_path_merge_head());
        }

        while (!strbuf_getwholeline_fd(&line, merge_head, '\n')) {
                struct object_id oid;
                if (line.len < GIT_SHA1_HEXSZ || get_oid_hex(line.buf, &oid))
                        die("unknown line in '%s': %s", git_path_merge_head(), line.buf);
                tail = append_parent(tail, &oid);
        }
        close(merge_head);
        strbuf_release(&line);
}

/*
 * This isn't as simple as passing sb->buf and sb->len, because we
 * want to transfer ownership of the buffer to the commit (so we
 * must use detach).
 */
static void set_commit_buffer_from_strbuf(struct commit *c, struct strbuf *sb)
{
        size_t len;
        void *buf = strbuf_detach(sb, &len);
        set_commit_buffer(c, buf, len);
}

/*
 * Prepare a dummy commit that represents the work tree (or staged) item.
 * Note that annotating work tree item never works in the reverse.
 */
struct commit *fake_working_tree_commit(struct diff_options *opt,
                                        const char *path,
                                        const char *contents_from)
{
        struct commit *commit;
        struct blame_origin *origin;
        struct commit_list **parent_tail, *parent;
        struct object_id head_oid;
        struct strbuf buf = STRBUF_INIT;
        const char *ident;
        time_t now;
        int size, len;
        struct cache_entry *ce;
        unsigned mode;
        struct strbuf msg = STRBUF_INIT;

        read_cache();
        time(&now);
        commit = alloc_commit_node();
        commit->object.parsed = 1;
        commit->date = now;
        parent_tail = &commit->parents;

        if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, head_oid.hash, NULL))
                die("no such ref: HEAD");

        parent_tail = append_parent(parent_tail, &head_oid);
        append_merge_parents(parent_tail);
        verify_working_tree_path(commit, path);

        origin = make_origin(commit, path);

        ident = fmt_ident("Not Committed Yet", "not.committed.yet", NULL, 0);
        strbuf_addstr(&msg, "tree 0000000000000000000000000000000000000000\n");
        for (parent = commit->parents; parent; parent = parent->next)
                strbuf_addf(&msg, "parent %s\n",
                            oid_to_hex(&parent->item->object.oid));
        strbuf_addf(&msg,
                    "author %s\n"
                    "committer %s\n\n"
                    "Version of %s from %s\n",
                    ident, ident, path,
                    (!contents_from ? path :
                     (!strcmp(contents_from, "-") ? "standard input" : contents_from)));
        set_commit_buffer_from_strbuf(commit, &msg);

        if (!contents_from || strcmp("-", contents_from)) {
                struct stat st;
                const char *read_from;
                char *buf_ptr;
                unsigned long buf_len;

                if (contents_from) {
                        if (stat(contents_from, &st) < 0)
                                die_errno("Cannot stat '%s'", contents_from);
                        read_from = contents_from;
                }
                else {
                        if (lstat(path, &st) < 0)
                                die_errno("Cannot lstat '%s'", path);
                        read_from = path;
                }
                mode = canon_mode(st.st_mode);

                switch (st.st_mode & S_IFMT) {
                case S_IFREG:
                        if (DIFF_OPT_TST(opt, ALLOW_TEXTCONV) &&
                            textconv_object(read_from, mode, &null_oid, 0, &buf_ptr, &buf_len))
                                strbuf_attach(&buf, buf_ptr, buf_len, buf_len + 1);
                        else if (strbuf_read_file(&buf, read_from, st.st_size) != st.st_size)
                                die_errno("cannot open or read '%s'", read_from);
                        break;
                case S_IFLNK:
                        if (strbuf_readlink(&buf, read_from, st.st_size) < 0)
                                die_errno("cannot readlink '%s'", read_from);
                        break;
                default:
                        die("unsupported file type %s", read_from);
                }
        }
        else {
                /* Reading from stdin */
                mode = 0;
                if (strbuf_read(&buf, 0, 0) < 0)
                        die_errno("failed to read from stdin");
        }
        convert_to_git(path, buf.buf, buf.len, &buf, 0);
        origin->file.ptr = buf.buf;
        origin->file.size = buf.len;
        pretend_sha1_file(buf.buf, buf.len, OBJ_BLOB, origin->blob_oid.hash);

        /*
         * Read the current index, replace the path entry with
         * origin->blob_sha1 without mucking with its mode or type
         * bits; we are not going to write this index out -- we just
         * want to run "diff-index --cached".
         */
        discard_cache();
        read_cache();

        len = strlen(path);
        if (!mode) {
                int pos = cache_name_pos(path, len);
                if (0 <= pos)
                        mode = active_cache[pos]->ce_mode;
                else
                        /* Let's not bother reading from HEAD tree */
                        mode = S_IFREG | 0644;
        }
        size = cache_entry_size(len);
        ce = xcalloc(1, size);
        oidcpy(&ce->oid, &origin->blob_oid);
        memcpy(ce->name, path, len);
        ce->ce_flags = create_ce_flags(0);
        ce->ce_namelen = len;
        ce->ce_mode = create_ce_mode(mode);
        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);

        cache_tree_invalidate_path(&the_index, path);

        return commit;
}