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

#define DEBUG 0

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)
{
        int i;

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

static struct cache_tree_sub *find_subtree(struct cache_tree *it,
                                           const char *path,
                                           int pathlen,
                                           int create)
{
        int i;
        struct cache_tree_sub *down;
        for (i = 0; i < it->subtree_nr; i++) {
                down = it->down[i];
                if (down->namelen == pathlen &&
                    !memcmp(down->name, path, pathlen))
                        return down;
        }
        if (!create)
                return NULL;
        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));
        }
        down = xmalloc(sizeof(*down) + pathlen + 1);
        down->cache_tree = NULL; /* cache_tree(); */
        down->namelen = pathlen;
        memcpy(down->name, path, pathlen);
        down->name[pathlen] = 0; /* not strictly needed */
        it->down[it->subtree_nr++] = down;
        return down;
}

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

static int update_one(struct cache_tree *it,
                      struct cache_entry **cache,
                      int entries,
                      const char *base,
                      int baselen,
                      int missing_ok)
{
        unsigned long size, offset;
        char *buffer;
        int i;

        if (0 <= it->entry_count)
                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);
                i += subcnt - 1;
                sub->used = 1;
        }

        discard_unused_subtrees(it);

        /*
         * Then write out the tree object for this level.
         */
        size = 8192;
        buffer = xmalloc(size);
        offset = 0;

        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 = ntohl(ce->ce_mode);
                        entlen = pathlen - baselen;
                }
                if (!missing_ok && !has_sha1_file(sha1))
                        return error("invalid object %s", sha1_to_hex(sha1));

                if (!ce->ce_mode)
                        continue; /* entry being removed */

                if (size < offset + entlen + 100) {
                        size = alloc_nr(offset + entlen + 100);
                        buffer = xrealloc(buffer, size);
                }
                offset += sprintf(buffer + offset,
                                  "%o %.*s", mode, entlen, path + baselen);
                buffer[offset++] = 0;
                memcpy(buffer + offset, sha1, 20);
                offset += 20;

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

        write_sha1_file(buffer, offset, tree_type, it->sha1);
        free(buffer);
        it->entry_count = i;
#if DEBUG
        fprintf(stderr, "cache-tree (%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 i;
        i = verify_cache(cache, entries);
        if (i)
                return i;
        i = update_one(it, cache, entries, "", 0, missing_ok);
        if (i < 0)
                return i;
        return 0;
}

static void *write_one(struct cache_tree *it,
                       char *path,
                       int pathlen,
                       char *buffer,
                       unsigned long *size,
                       unsigned long *offset)
{
        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.
         */
        if (*size < *offset + pathlen + 100) {
                *size = alloc_nr(*offset + pathlen + 100);
                buffer = xrealloc(buffer, *size);
        }
        *offset += sprintf(buffer + *offset, "%.*s%c%d %d\n",
                           pathlen, path, 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) {
                memcpy(buffer + *offset, it->sha1, 20);
                *offset += 20;
        }
        for (i = 0; i < it->subtree_nr; i++) {
                struct cache_tree_sub *down = it->down[i];
                buffer = write_one(down->cache_tree, down->name, down->namelen,
                                   buffer, size, offset);
        }
        return buffer;
}

static void *cache_tree_write(const unsigned char *cache_sha1,
                              struct cache_tree *root,
                              unsigned long *offset_p)
{
        char path[PATH_MAX];
        unsigned long size = 8192;
        char *buffer = xmalloc(size);

        /* the cache checksum of the corresponding index file. */
        memcpy(buffer, cache_sha1, 20);
        *offset_p = 20;
        path[0] = 0;
        return write_one(root, path, 0, buffer, &size, offset_p);
}

static struct cache_tree *read_one(const char **buffer, unsigned long *size_p)
{
        const char *buf = *buffer;
        unsigned long size = *size_p;
        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();
        if (sscanf(buf, "%d %d\n", &it->entry_count, &subtree_nr) != 2)
                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;
                memcpy(it->sha1, buf, 20);
                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;
                const char *name = buf;
                int namelen;
                sub = read_one(&buf, &size);
                if (!sub)
                        goto free_return;
                namelen = strlen(name);
                it->down[i] = find_subtree(it, name, namelen, 1);
                it->down[i]->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;
}

static struct cache_tree *cache_tree_read(unsigned char *sha1,
                                          const char *buffer,
                                          unsigned long size)
{
        /* check the cache-tree matches the index */
        if (memcmp(buffer, sha1, 20))
                return NULL; /* checksum mismatch */
        if (buffer[20])
                return NULL; /* not the whole tree */
        buffer += 20;
        size -= 20;
        return read_one(&buffer, &size);
}

struct cache_tree *read_cache_tree(unsigned char *sha1)
{
        int fd;
        struct stat st;
        char path[PATH_MAX];
        unsigned long size = 0;
        void *map;
        struct cache_tree *it;

        sprintf(path, "%s.aux", get_index_file());
        fd = open(path, O_RDONLY);
        if (fd < 0)
                return cache_tree();

        if (fstat(fd, &st))
                return cache_tree();
        size = st.st_size;
        map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
        close(fd);
        if (map == MAP_FAILED)
                return cache_tree();
        it = cache_tree_read(sha1, map, size);
        munmap(map, size);
        if (!it)
                return cache_tree();
        return it;
}

int write_cache_tree(const unsigned char *sha1, struct cache_tree *root)
{
        char path[PATH_MAX];
        unsigned long size = 0;
        void *buf, *buffer;
        int fd, ret = -1;

        sprintf(path, "%s.aux", get_index_file());
        if (!root) {
                unlink(path);
                return -1;
        }
        fd = open(path, O_WRONLY|O_CREAT, 0666);
        if (fd < 0)
                return -1;
        buffer = buf = cache_tree_write(sha1, root, &size);
        while (size) {
                int written = xwrite(fd, buf, size);
                if (written <= 0)
                        goto fail;
                buf += written;
                size -= written;
        }
        ret = 0;

 fail:
        close(fd);
        free(buffer);
        if (ret)
                unlink(path);
        return ret;
}