/*
 * GIT - The information manager from hell
 *
 * Copyright (C) Linus Torvalds, 2005
 */
#include "cache.h"

/*
 * Default to not allowing changes to the list of files. The
 * tool doesn't actually care, but this makes it harder to add
 * files to the revision control by mistake by doing something
 * like "update-cache *" and suddenly having all the object
 * files be revision controlled.
 */
static int allow_add = 0, allow_remove = 0;

static int index_fd(const char *path, int namelen, struct cache_entry *ce, int fd, struct stat *st)
{
        z_stream stream;
        int max_out_bytes = namelen + st->st_size + 200;
        void *out = malloc(max_out_bytes);
        void *metadata = malloc(namelen + 200);
        void *in = mmap(NULL, st->st_size, PROT_READ, MAP_PRIVATE, fd, 0);
        SHA_CTX c;

        close(fd);
        if (!out || (int)(long)in == -1)
                return -1;

        memset(&stream, 0, sizeof(stream));
        deflateInit(&stream, Z_BEST_COMPRESSION);

        /*
         * ASCII size + nul byte
         */     
        stream.next_in = metadata;
        stream.avail_in = 1+sprintf(metadata, "blob %lu", (unsigned long) st->st_size);
        stream.next_out = out;
        stream.avail_out = max_out_bytes;
        while (deflate(&stream, 0) == Z_OK)
                /* nothing */;

        /*
         * File content
         */
        stream.next_in = in;
        stream.avail_in = st->st_size;
        while (deflate(&stream, Z_FINISH) == Z_OK)
                /*nothing */;

        deflateEnd(&stream);
        
        SHA1_Init(&c);
        SHA1_Update(&c, out, stream.total_out);
        SHA1_Final(ce->sha1, &c);

        return write_sha1_buffer(ce->sha1, out, stream.total_out);
}

/*
 * This only updates the "non-critical" parts of the directory
 * cache, ie the parts that aren't tracked by GIT, and only used
 * to validate the cache.
 */
static void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
{
        ce->ctime.sec = st->st_ctime;
        ce->ctime.nsec = st->st_ctim.tv_nsec;
        ce->mtime.sec = st->st_mtime;
        ce->mtime.nsec = st->st_mtim.tv_nsec;
        ce->st_dev = st->st_dev;
        ce->st_ino = st->st_ino;
        ce->st_uid = st->st_uid;
        ce->st_gid = st->st_gid;
}

static int add_file_to_cache(char *path)
{
        int size, namelen;
        struct cache_entry *ce;
        struct stat st;
        int fd;

        fd = open(path, O_RDONLY);
        if (fd < 0) {
                if (errno == ENOENT) {
                        if (allow_remove)
                                return remove_file_from_cache(path);
                }
                return -1;
        }
        if (fstat(fd, &st) < 0) {
                close(fd);
                return -1;
        }
        namelen = strlen(path);
        size = cache_entry_size(namelen);
        ce = malloc(size);
        memset(ce, 0, size);
        memcpy(ce->name, path, namelen);
        fill_stat_cache_info(ce, &st);
        ce->st_mode = st.st_mode;
        ce->st_size = st.st_size;
        ce->namelen = namelen;

        if (index_fd(path, namelen, ce, fd, &st) < 0)
                return -1;

        return add_cache_entry(ce, allow_add);
}

static int match_data(int fd, void *buffer, unsigned long size)
{
        while (size) {
                char compare[1024];
                int ret = read(fd, compare, sizeof(compare));

                if (ret <= 0 || ret > size || memcmp(buffer, compare, ret))
                        return -1;
                size -= ret;
                buffer += ret;
        }
        return 0;
}

static int compare_data(struct cache_entry *ce, unsigned long expected_size)
{
        int match = -1;
        int fd = open(ce->name, O_RDONLY);

        if (fd >= 0) {
                void *buffer;
                unsigned long size;
                char type[10];

                buffer = read_sha1_file(ce->sha1, type, &size);
                if (buffer) {
                        if (size == expected_size && !strcmp(type, "blob"))
                                match = match_data(fd, buffer, size);
                        free(buffer);
                }
                close(fd);
        }
        return match;
}

/*
 * "refresh" does not calculate a new sha1 file or bring the
 * cache up-to-date for mode/content changes. But what it
 * _does_ do is to "re-match" the stat information of a file
 * with the cache, so that you can refresh the cache for a
 * file that hasn't been changed but where the stat entry is
 * out of date.
 *
 * For example, you'd want to do this after doing a "read-tree",
 * to link up the stat cache details with the proper files.
 */
static struct cache_entry *refresh_entry(struct cache_entry *ce)
{
        struct stat st;
        struct cache_entry *updated;
        int changed, size;

        if (stat(ce->name, &st) < 0)
                return NULL;

        changed = cache_match_stat(ce, &st);
        if (!changed)
                return ce;

        /*
         * If the mode has changed, there's no point in trying
         * to refresh the entry - it's not going to match
         */
        if (changed & MODE_CHANGED)
                return NULL;

        if (compare_data(ce, st.st_size))
                return NULL;

        size = ce_size(ce);
        updated = malloc(size);
        memcpy(updated, ce, size);
        fill_stat_cache_info(updated, &st);
        updated->st_size = st.st_size;
        return updated;
}

static void refresh_cache(void)
{
        int i;

        for (i = 0; i < active_nr; i++) {
                struct cache_entry *ce = active_cache[i];
                struct cache_entry *new = refresh_entry(ce);

                if (!new) {
                        printf("%s: needs update\n", ce->name);
                        continue;
                }
                active_cache[i] = new;
        }
}

/*
 * We fundamentally don't like some paths: we don't want
 * dot or dot-dot anywhere, and in fact, we don't even want
 * any other dot-files (.dircache or anything else). They
 * are hidden, for chist sake.
 *
 * Also, we don't want double slashes or slashes at the
 * end that can make pathnames ambiguous. 
 */
static int verify_path(char *path)
{
        char c;

        goto inside;
        for (;;) {
                if (!c)
                        return 1;
                if (c == '/') {
inside:
                        c = *path++;
                        if (c != '/' && c != '.' && c != '\0')
                                continue;
                        return 0;
                }
                c = *path++;
        }
}

static int remove_lock = 0;

static void remove_lock_file(void)
{
        if (remove_lock)
                unlink(".dircache/index.lock");
}

int main(int argc, char **argv)
{
        int i, newfd, entries;
        int allow_options = 1;

        newfd = open(".dircache/index.lock", O_RDWR | O_CREAT | O_EXCL, 0600);
        if (newfd < 0)
                usage("unable to create new cachefile");

        atexit(remove_lock_file);
        remove_lock = 1;

        entries = read_cache();
        if (entries < 0)
                usage("cache corrupted");

        for (i = 1 ; i < argc; i++) {
                char *path = argv[i];

                if (allow_options && *path == '-') {
                        if (!strcmp(path, "--")) {
                                allow_options = 0;
                                continue;
                        }
                        if (!strcmp(path, "--add")) {
                                allow_add = 1;
                                continue;
                        }
                        if (!strcmp(path, "--remove")) {
                                allow_remove = 1;
                                continue;
                        }
                        if (!strcmp(path, "--refresh")) {
                                refresh_cache();
                                continue;
                        }
                        usage("unknown option %s", path);
                }
                if (!verify_path(path)) {
                        fprintf(stderr, "Ignoring path %s\n", argv[i]);
                        continue;
                }
                if (add_file_to_cache(path))
                        usage("Unable to add %s to database", path);
        }
        if (write_cache(newfd, active_cache, active_nr) ||
            rename(".dircache/index.lock", ".dircache/index"))
                usage("Unable to write new cachefile");

        remove_lock = 0;
        return 0;
}