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

#ifndef DEBUG
#define DEBUG 0
#endif

struct cache_tree *cache_tree(void)
{
        struct cache_tree *it = xcalloc(1, sizeof(struct cache_tree));
        it->entry_count = -1;
        return it;
}

void cache_tree_free(struct cache_tree **it_p)
{
        int i;
        struct cache_tree *it = *it_p;

        if (!it)
                return;
        for (i = 0; i < it->subtree_nr; i++)
                if (it->down[i])
                        cache_tree_free(&it->down[i]->cache_tree);
        free(it->down);
        free(it);
        *it_p = NULL;
}

static int subtree_name_cmp(const char *one, int onelen,
                            const char *two, int twolen)
{
        if (onelen < twolen)
                return -1;
        if (twolen < onelen)
                return 1;
        return memcmp(one, two, onelen);
}

static int subtree_pos(struct cache_tree *it, const char *path, int pathlen)
{
        struct cache_tree_sub **down = it->down;
        int lo, hi;
        lo = 0;
        hi = it->subtree_nr;
        while (lo < hi) {
                int mi = (lo + hi) / 2;
                struct cache_tree_sub *mdl = down[mi];
                int cmp = subtree_name_cmp(path, pathlen,
                                           mdl->name, mdl->namelen);
                if (!cmp)
                        return mi;
                if (cmp < 0)
                        hi = mi;
                else
                        lo = mi + 1;
        }
        return -lo-1;
}

static struct cache_tree_sub *find_subtree(struct cache_tree *it,
                                           const char *path,
                                           int pathlen,
                                           int create)
{
        struct cache_tree_sub *down;
        int pos = subtree_pos(it, path, pathlen);
        if (0 <= pos)
                return it->down[pos];
        if (!create)
                return NULL;

        pos = -pos-1;
        if (it->subtree_alloc <= it->subtree_nr) {
                it->subtree_alloc = alloc_nr(it->subtree_alloc);
                it->down = xrealloc(it->down, it->subtree_alloc *
                                    sizeof(*it->down));
        }
        it->subtree_nr++;

        down = xmalloc(sizeof(*down) + pathlen + 1);
        down->cache_tree = NULL;
        down->namelen = pathlen;
        memcpy(down->name, path, pathlen);
        down->name[pathlen] = 0;

        if (pos < it->subtree_nr)
                memmove(it->down + pos + 1,
                        it->down + pos,
                        sizeof(down) * (it->subtree_nr - pos - 1));
        it->down[pos] = down;
        return down;
}

struct cache_tree_sub *cache_tree_sub(struct cache_tree *it, const char *path)
{
        int pathlen = strlen(path);
        return find_subtree(it, path, pathlen, 1);
}

void cache_tree_invalidate_path(struct cache_tree *it, const char *path)
{
        /* a/b/c
         * ==> invalidate self
         * ==> find "a", have it invalidate "b/c"
         * a
         * ==> invalidate self
         * ==> if "a" exists as a subtree, remove it.
         */
        const char *slash;
        int namelen;
        struct cache_tree_sub *down;

#if DEBUG
        fprintf(stderr, "cache-tree invalidate <%s>\n", path);
#endif

        if (!it)
                return;
        slash = strchr(path, '/');
        it->entry_count = -1;
        if (!slash) {
                int pos;
                namelen = strlen(path);
                pos = subtree_pos(it, path, namelen);
                if (0 <= pos) {
                        cache_tree_free(&it->down[pos]->cache_tree);
                        free(it->down[pos]);
                        /* 0 1 2 3 4 5
                         *       ^     ^subtree_nr = 6
                         *       pos
                         * move 4 and 5 up one place (2 entries)
                         * 2 = 6 - 3 - 1 = subtree_nr - pos - 1
                         */
                        memmove(it->down+pos, it->down+pos+1,
                                sizeof(struct cache_tree_sub *) *
                                (it->subtree_nr - pos - 1));
                        it->subtree_nr--;
                }
                return;
        }
        namelen = slash - path;
        down = find_subtree(it, path, namelen, 0);
        if (down)
                cache_tree_invalidate_path(down->cache_tree, slash + 1);
}

static int verify_cache(struct cache_entry **cache,
                        int entries)
{
        int i, funny;

        /* Verify that the tree is merged */
        funny = 0;
        for (i = 0; i < entries; i++) {
                struct cache_entry *ce = cache[i];
                if (ce_stage(ce)) {
                        if (10 < ++funny) {
                                fprintf(stderr, "...\n");
                                break;
                        }
                        fprintf(stderr, "%s: unmerged (%s)\n",
                                ce->name, sha1_to_hex(ce->sha1));
                }
        }
        if (funny)
                return -1;

        /* Also verify that the cache does not have path and path/file
         * at the same time.  At this point we know the cache has only
         * stage 0 entries.
         */
        funny = 0;
        for (i = 0; i < entries - 1; i++) {
                /* path/file always comes after path because of the way
                 * the cache is sorted.  Also path can appear only once,
                 * which means conflicting one would immediately follow.
                 */
                const char *this_name = cache[i]->name;
                const char *next_name = cache[i+1]->name;
                int this_len = strlen(this_name);
                if (this_len < strlen(next_name) &&
                    strncmp(this_name, next_name, this_len) == 0 &&
                    next_name[this_len] == '/') {
                        if (10 < ++funny) {
                                fprintf(stderr, "...\n");
                                break;
                        }
                        fprintf(stderr, "You have both %s and %s\n",
                                this_name, next_name);
                }
        }
        if (funny)
                return -1;
        return 0;
}

static void discard_unused_subtrees(struct cache_tree *it)
{
        struct cache_tree_sub **down = it->down;
        int nr = it->subtree_nr;
        int dst, src;
        for (dst = src = 0; src < nr; src++) {
                struct cache_tree_sub *s = down[src];
                if (s->used)
                        down[dst++] = s;
                else {
                        cache_tree_free(&s->cache_tree);
                        free(s);
                        it->subtree_nr--;
                }
        }
}

int cache_tree_fully_valid(struct cache_tree *it)
{
        int i;
        if (!it)
                return 0;
        if (it->entry_count < 0 || !has_sha1_file(it->sha1))
                return 0;
        for (i = 0; i < it->subtree_nr; i++) {
                if (!cache_tree_fully_valid(it->down[i]->cache_tree))
                        return 0;
        }
        return 1;
}

static int update_one(struct cache_tree *it,
                      struct cache_entry **cache,
                      int entries,
                      const char *base,
                      int baselen,
                      int missing_ok,
                      int dryrun)
{
        struct strbuf buffer;
        int i;

        if (0 <= it->entry_count && has_sha1_file(it->sha1))
                return it->entry_count;

        /*
         * We first scan for subtrees and update them; we start by
         * marking existing subtrees -- the ones that are unmarked
         * should not be in the result.
         */
        for (i = 0; i < it->subtree_nr; i++)
                it->down[i]->used = 0;

        /*
         * Find the subtrees and update them.
         */
        for (i = 0; i < entries; i++) {
                struct cache_entry *ce = cache[i];
                struct cache_tree_sub *sub;
                const char *path, *slash;
                int pathlen, sublen, subcnt;

                path = ce->name;
                pathlen = ce_namelen(ce);
                if (pathlen <= baselen || memcmp(base, path, baselen))
                        break; /* at the end of this level */

                slash = strchr(path + baselen, '/');
                if (!slash)
                        continue;
                /*
                 * a/bbb/c (base = a/, slash = /c)
                 * ==>
                 * path+baselen = bbb/c, sublen = 3
                 */
                sublen = slash - (path + baselen);
                sub = find_subtree(it, path + baselen, sublen, 1);
                if (!sub->cache_tree)
                        sub->cache_tree = cache_tree();
                subcnt = update_one(sub->cache_tree,
                                    cache + i, entries - i,
                                    path,
                                    baselen + sublen + 1,
                                    missing_ok,
                                    dryrun);
                if (subcnt < 0)
                        return subcnt;
                i += subcnt - 1;
                sub->used = 1;
        }

        discard_unused_subtrees(it);

        /*
         * Then write out the tree object for this level.
         */
        strbuf_init(&buffer, 8192);

        for (i = 0; i < entries; i++) {
                struct cache_entry *ce = cache[i];
                struct cache_tree_sub *sub;
                const char *path, *slash;
                int pathlen, entlen;
                const unsigned char *sha1;
                unsigned mode;

                path = ce->name;
                pathlen = ce_namelen(ce);
                if (pathlen <= baselen || memcmp(base, path, baselen))
                        break; /* at the end of this level */

                slash = strchr(path + baselen, '/');
                if (slash) {
                        entlen = slash - (path + baselen);
                        sub = find_subtree(it, path + baselen, entlen, 0);
                        if (!sub)
                                die("cache-tree.c: '%.*s' in '%s' not found",
                                    entlen, path + baselen, path);
                        i += sub->cache_tree->entry_count - 1;
                        sha1 = sub->cache_tree->sha1;
                        mode = S_IFDIR;
                }
                else {
                        sha1 = ce->sha1;
                        mode = ce->ce_mode;
                        entlen = pathlen - baselen;
                }
                if (mode != S_IFGITLINK && !missing_ok && !has_sha1_file(sha1))
                        return error("invalid object %s", sha1_to_hex(sha1));

                if (ce->ce_flags & CE_REMOVE)
                        continue; /* entry being removed */

                strbuf_grow(&buffer, entlen + 100);
                strbuf_addf(&buffer, "%o %.*s%c", mode, entlen, path + baselen, '\0');
                strbuf_add(&buffer, sha1, 20);

#if DEBUG
                fprintf(stderr, "cache-tree update-one %o %.*s\n",
                        mode, entlen, path + baselen);
#endif
        }

        if (dryrun)
                hash_sha1_file(buffer.buf, buffer.len, tree_type, it->sha1);
        else
                write_sha1_file(buffer.buf, buffer.len, tree_type, it->sha1);
        strbuf_release(&buffer);
        it->entry_count = i;
#if DEBUG
        fprintf(stderr, "cache-tree update-one (%d ent, %d subtree) %s\n",
                it->entry_count, it->subtree_nr,
                sha1_to_hex(it->sha1));
#endif
        return i;
}

int cache_tree_update(struct cache_tree *it,
                      struct cache_entry **cache,
                      int entries,
                      int missing_ok,
                      int dryrun)
{
        int i;
        i = verify_cache(cache, entries);
        if (i)
                return i;
        i = update_one(it, cache, entries, "", 0, missing_ok, dryrun);
        if (i < 0)
                return i;
        return 0;
}

static void write_one(struct strbuf *buffer, struct cache_tree *it,
                      const char *path, int pathlen)
{
        int i;

        /* One "cache-tree" entry consists of the following:
         * path (NUL terminated)
         * entry_count, subtree_nr ("%d %d\n")
         * tree-sha1 (missing if invalid)
         * subtree_nr "cache-tree" entries for subtrees.
         */
        strbuf_grow(buffer, pathlen + 100);
        strbuf_add(buffer, path, pathlen);
        strbuf_addf(buffer, "%c%d %d\n", 0, it->entry_count, it->subtree_nr);

#if DEBUG
        if (0 <= it->entry_count)
                fprintf(stderr, "cache-tree <%.*s> (%d ent, %d subtree) %s\n",
                        pathlen, path, it->entry_count, it->subtree_nr,
                        sha1_to_hex(it->sha1));
        else
                fprintf(stderr, "cache-tree <%.*s> (%d subtree) invalid\n",
                        pathlen, path, it->subtree_nr);
#endif

        if (0 <= it->entry_count) {
                strbuf_add(buffer, it->sha1, 20);
        }
        for (i = 0; i < it->subtree_nr; i++) {
                struct cache_tree_sub *down = it->down[i];
                if (i) {
                        struct cache_tree_sub *prev = it->down[i-1];
                        if (subtree_name_cmp(down->name, down->namelen,
                                             prev->name, prev->namelen) <= 0)
                                die("fatal - unsorted cache subtree");
                }
                write_one(buffer, down->cache_tree, down->name, down->namelen);
        }
}

void cache_tree_write(struct strbuf *sb, struct cache_tree *root)
{
        write_one(sb, root, "", 0);
}

static struct cache_tree *read_one(const char **buffer, unsigned long *size_p)
{
        const char *buf = *buffer;
        unsigned long size = *size_p;
        const char *cp;
        char *ep;
        struct cache_tree *it;
        int i, subtree_nr;

        it = NULL;
        /* skip name, but make sure name exists */
        while (size && *buf) {
                size--;
                buf++;
        }
        if (!size)
                goto free_return;
        buf++; size--;
        it = cache_tree();

        cp = buf;
        it->entry_count = strtol(cp, &ep, 10);
        if (cp == ep)
                goto free_return;
        cp = ep;
        subtree_nr = strtol(cp, &ep, 10);
        if (cp == ep)
                goto free_return;
        while (size && *buf && *buf != '\n') {
                size--;
                buf++;
        }
        if (!size)
                goto free_return;
        buf++; size--;
        if (0 <= it->entry_count) {
                if (size < 20)
                        goto free_return;
                hashcpy(it->sha1, (const unsigned char*)buf);
                buf += 20;
                size -= 20;
        }

#if DEBUG
        if (0 <= it->entry_count)
                fprintf(stderr, "cache-tree <%s> (%d ent, %d subtree) %s\n",
                        *buffer, it->entry_count, subtree_nr,
                        sha1_to_hex(it->sha1));
        else
                fprintf(stderr, "cache-tree <%s> (%d subtrees) invalid\n",
                        *buffer, subtree_nr);
#endif

        /*
         * Just a heuristic -- we do not add directories that often but
         * we do not want to have to extend it immediately when we do,
         * hence +2.
         */
        it->subtree_alloc = subtree_nr + 2;
        it->down = xcalloc(it->subtree_alloc, sizeof(struct cache_tree_sub *));
        for (i = 0; i < subtree_nr; i++) {
                /* read each subtree */
                struct cache_tree *sub;
                struct cache_tree_sub *subtree;
                const char *name = buf;

                sub = read_one(&buf, &size);
                if (!sub)
                        goto free_return;
                subtree = cache_tree_sub(it, name);
                subtree->cache_tree = sub;
        }
        if (subtree_nr != it->subtree_nr)
                die("cache-tree: internal error");
        *buffer = buf;
        *size_p = size;
        return it;

 free_return:
        cache_tree_free(&it);
        return NULL;
}

struct cache_tree *cache_tree_read(const char *buffer, unsigned long size)
{
        if (buffer[0])
                return NULL; /* not the whole tree */
        return read_one(&buffer, &size);
}

struct cache_tree *cache_tree_find(struct cache_tree *it, const char *path)
{
        while (*path) {
                const char *slash;
                struct cache_tree_sub *sub;

                slash = strchr(path, '/');
                if (!slash)
                        slash = path + strlen(path);
                /* between path and slash is the name of the
                 * subtree to look for.
                 */
                sub = find_subtree(it, path, slash - path, 0);
                if (!sub)
                        return NULL;
                it = sub->cache_tree;
                if (slash)
                        while (*slash && *slash == '/')
                                slash++;
                if (!slash || !*slash)
                        return it; /* prefix ended with slashes */
                path = slash;
        }
        return it;
}

int write_cache_as_tree(unsigned char *sha1, int missing_ok, const char *prefix)
{
        int entries, was_valid, newfd;

        /*
         * We can't free this memory, it becomes part of a linked list
         * parsed atexit()
         */
        struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));

        newfd = hold_locked_index(lock_file, 1);

        entries = read_cache();
        if (entries < 0)
                return WRITE_TREE_UNREADABLE_INDEX;

        if (!active_cache_tree)
                active_cache_tree = cache_tree();

        was_valid = cache_tree_fully_valid(active_cache_tree);

        if (!was_valid) {
                if (cache_tree_update(active_cache_tree,
                                      active_cache, active_nr,
                                      missing_ok, 0) < 0)
                        return WRITE_TREE_UNMERGED_INDEX;
                if (0 <= newfd) {
                        if (!write_cache(newfd, active_cache, active_nr) &&
                            !commit_lock_file(lock_file))
                                newfd = -1;
                }
                /* Not being able to write is fine -- we are only interested
                 * in updating the cache-tree part, and if the next caller
                 * ends up using the old index with unupdated cache-tree part
                 * it misses the work we did here, but that is just a
                 * performance penalty and not a big deal.
                 */
        }

        if (prefix) {
                struct cache_tree *subtree =
                        cache_tree_find(active_cache_tree, prefix);
                if (!subtree)
                        return WRITE_TREE_PREFIX_ERROR;
                hashcpy(sha1, subtree->sha1);
        }
        else
                hashcpy(sha1, active_cache_tree->sha1);

        if (0 <= newfd)
                rollback_lock_file(lock_file);

        return 0;
}