/*
 * name-hash.c
 *
 * Hashing names in the index state
 *
 * Copyright (C) 2008 Linus Torvalds
 */
#define NO_THE_INDEX_COMPATIBILITY_MACROS
#include "cache.h"

struct dir_entry {
        struct hashmap_entry ent;
        struct dir_entry *parent;
        struct cache_entry *ce;
        int nr;
        unsigned int namelen;
};

static int dir_entry_cmp(const struct dir_entry *e1,
                const struct dir_entry *e2, const char *name)
{
        return e1->namelen != e2->namelen || strncasecmp(e1->ce->name,
                        name ? name : e2->ce->name, e1->namelen);
}

static struct dir_entry *find_dir_entry(struct index_state *istate,
                const char *name, unsigned int namelen)
{
        struct dir_entry key;
        hashmap_entry_init(&key, memihash(name, namelen));
        key.namelen = namelen;
        return hashmap_get(&istate->dir_hash, &key, name);
}

static struct dir_entry *hash_dir_entry(struct index_state *istate,
                struct cache_entry *ce, int namelen)
{
        /*
         * Throw each directory component in the hash for quick lookup
         * during a git status. Directory components are stored without their
         * closing slash.  Despite submodules being a directory, they never
         * reach this point, because they are stored
         * in index_state.name_hash (as ordinary cache_entries).
         *
         * Note that the cache_entry stored with the dir_entry merely
         * supplies the name of the directory (up to dir_entry.namelen). We
         * track the number of 'active' files in a directory in dir_entry.nr,
         * so we can tell if the directory is still relevant, e.g. for git
         * status. However, if cache_entries are removed, we cannot pinpoint
         * an exact cache_entry that's still active. It is very possible that
         * multiple dir_entries point to the same cache_entry.
         */
        struct dir_entry *dir;

        /* get length of parent directory */
        while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
                namelen--;
        if (namelen <= 0)
                return NULL;
        namelen--;

        /* lookup existing entry for that directory */
        dir = find_dir_entry(istate, ce->name, namelen);
        if (!dir) {
                /* not found, create it and add to hash table */
                dir = xcalloc(1, sizeof(struct dir_entry));
                hashmap_entry_init(dir, memihash(ce->name, namelen));
                dir->namelen = namelen;
                dir->ce = ce;
                hashmap_add(&istate->dir_hash, dir);

                /* recursively add missing parent directories */
                dir->parent = hash_dir_entry(istate, ce, namelen);
        }
        return dir;
}

static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
{
        /* Add reference to the directory entry (and parents if 0). */
        struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
        while (dir && !(dir->nr++))
                dir = dir->parent;
}

static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
{
        /*
         * Release reference to the directory entry. If 0, remove and continue
         * with parent directory.
         */
        struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
        while (dir && !(--dir->nr)) {
                struct dir_entry *parent = dir->parent;
                hashmap_remove(&istate->dir_hash, dir, NULL);
                free(dir);
                dir = parent;
        }
}

static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
{
        if (ce->ce_flags & CE_HASHED)
                return;
        ce->ce_flags |= CE_HASHED;
        hashmap_entry_init(ce, memihash(ce->name, ce_namelen(ce)));
        hashmap_add(&istate->name_hash, ce);

        if (ignore_case)
                add_dir_entry(istate, ce);
}

static int cache_entry_cmp(const struct cache_entry *ce1,
                const struct cache_entry *ce2, const void *remove)
{
        /*
         * For remove_name_hash, find the exact entry (pointer equality); for
         * index_file_exists, find all entries with matching hash code and
         * decide whether the entry matches in same_name.
         */
        return remove ? !(ce1 == ce2) : 0;
}

static void lazy_init_name_hash(struct index_state *istate)
{
        int nr;

        if (istate->name_hash_initialized)
                return;
        hashmap_init(&istate->name_hash, (hashmap_cmp_fn) cache_entry_cmp,
                        istate->cache_nr);
        hashmap_init(&istate->dir_hash, (hashmap_cmp_fn) dir_entry_cmp, 0);
        for (nr = 0; nr < istate->cache_nr; nr++)
                hash_index_entry(istate, istate->cache[nr]);
        istate->name_hash_initialized = 1;
}

void add_name_hash(struct index_state *istate, struct cache_entry *ce)
{
        if (istate->name_hash_initialized)
                hash_index_entry(istate, ce);
}

void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
{
        if (!istate->name_hash_initialized || !(ce->ce_flags & CE_HASHED))
                return;
        ce->ce_flags &= ~CE_HASHED;
        hashmap_remove(&istate->name_hash, ce, ce);

        if (ignore_case)
                remove_dir_entry(istate, ce);
}

static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
{
        if (len1 != len2)
                return 0;

        while (len1) {
                unsigned char c1 = *name1++;
                unsigned char c2 = *name2++;
                len1--;
                if (c1 != c2) {
                        c1 = toupper(c1);
                        c2 = toupper(c2);
                        if (c1 != c2)
                                return 0;
                }
        }
        return 1;
}

static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
{
        int len = ce_namelen(ce);

        /*
         * Always do exact compare, even if we want a case-ignoring comparison;
         * we do the quick exact one first, because it will be the common case.
         */
        if (len == namelen && !memcmp(name, ce->name, len))
                return 1;

        if (!icase)
                return 0;

        return slow_same_name(name, namelen, ce->name, len);
}

struct cache_entry *index_dir_exists(struct index_state *istate, const char *name, int namelen)
{
        struct cache_entry *ce;
        struct dir_entry *dir;

        lazy_init_name_hash(istate);
        dir = find_dir_entry(istate, name, namelen);
        if (dir && dir->nr)
                return dir->ce;

        /*
         * It might be a submodule. Unlike plain directories, which are stored
         * in the dir-hash, submodules are stored in the name-hash, so check
         * there, as well.
         */
        ce = index_file_exists(istate, name, namelen, 1);
        if (ce && S_ISGITLINK(ce->ce_mode))
                return ce;

        return NULL;
}

struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
{
        struct cache_entry *ce;

        lazy_init_name_hash(istate);

        ce = hashmap_get_from_hash(&istate->name_hash,
                                   memihash(name, namelen), NULL);
        while (ce) {
                if (same_name(ce, name, namelen, icase))
                        return ce;
                ce = hashmap_get_next(&istate->name_hash, ce);
        }
        return NULL;
}

void free_name_hash(struct index_state *istate)
{
        if (!istate->name_hash_initialized)
                return;
        istate->name_hash_initialized = 0;

        hashmap_free(&istate->name_hash, 0);
        hashmap_free(&istate->dir_hash, 1);
}