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

struct cache_entry **active_cache = NULL;
unsigned int active_nr = 0, active_alloc = 0, active_cache_changed = 0;

int cache_match_stat(struct cache_entry *ce, struct stat *st)
{
        unsigned int changed = 0;

        switch (ntohl(ce->ce_mode) & S_IFMT) {
        case S_IFREG:
                changed |= !S_ISREG(st->st_mode) ? TYPE_CHANGED : 0;
                /* We consider only the owner x bit to be relevant for "mode changes" */
                if (0100 & (ntohl(ce->ce_mode) ^ st->st_mode))
                        changed |= MODE_CHANGED;
                break;
        case S_IFLNK:
                changed |= !S_ISLNK(st->st_mode) ? TYPE_CHANGED : 0;
                break;
        default:
                die("internal error: ce_mode is %o", ntohl(ce->ce_mode));
        }
        if (ce->ce_mtime.sec != htonl(st->st_mtime))
                changed |= MTIME_CHANGED;
        if (ce->ce_ctime.sec != htonl(st->st_ctime))
                changed |= CTIME_CHANGED;

#ifdef NSEC
        /*
         * nsec seems unreliable - not all filesystems support it, so
         * as long as it is in the inode cache you get right nsec
         * but after it gets flushed, you get zero nsec.
         */
        if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec))
                changed |= MTIME_CHANGED;
        if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec))
                changed |= CTIME_CHANGED;
#endif  

        if (ce->ce_uid != htonl(st->st_uid) ||
            ce->ce_gid != htonl(st->st_gid))
                changed |= OWNER_CHANGED;
        if (ce->ce_dev != htonl(st->st_dev) ||
            ce->ce_ino != htonl(st->st_ino))
                changed |= INODE_CHANGED;
        if (ce->ce_size != htonl(st->st_size))
                changed |= DATA_CHANGED;
        return changed;
}

int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
{
        int len1 = flags1 & CE_NAMEMASK;
        int len2 = flags2 & CE_NAMEMASK;
        int len = len1 < len2 ? len1 : len2;
        int cmp;

        cmp = memcmp(name1, name2, len);
        if (cmp)
                return cmp;
        if (len1 < len2)
                return -1;
        if (len1 > len2)
                return 1;
        if (flags1 < flags2)
                return -1;
        if (flags1 > flags2)
                return 1;
        return 0;
}

int cache_name_pos(const char *name, int namelen)
{
        int first, last;

        first = 0;
        last = active_nr;
        while (last > first) {
                int next = (last + first) >> 1;
                struct cache_entry *ce = active_cache[next];
                int cmp = cache_name_compare(name, namelen, ce->name, htons(ce->ce_flags));
                if (!cmp)
                        return next;
                if (cmp < 0) {
                        last = next;
                        continue;
                }
                first = next+1;
        }
        return -first-1;
}

/* Remove entry, return true if there are more entries to go.. */
int remove_entry_at(int pos)
{
        active_cache_changed = 1;
        active_nr--;
        if (pos >= active_nr)
                return 0;
        memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
        return 1;
}

int remove_file_from_cache(char *path)
{
        int pos = cache_name_pos(path, strlen(path));
        if (pos < 0)
                pos = -pos-1;
        while (pos < active_nr && !strcmp(active_cache[pos]->name, path))
                remove_entry_at(pos);
        return 0;
}

int same_name(struct cache_entry *a, struct cache_entry *b)
{
        int len = ce_namelen(a);
        return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
}

/* We may be in a situation where we already have path/file and path
 * is being added, or we already have path and path/file is being
 * added.  Either one would result in a nonsense tree that has path
 * twice when git-write-tree tries to write it out.  Prevent it.
 * 
 * If ok-to-replace is specified, we remove the conflicting entries
 * from the cache so the caller should recompute the insert position.
 * When this happens, we return non-zero.
 */
static int check_file_directory_conflict(const struct cache_entry *ce,
                                         int ok_to_replace)
{
        int pos, replaced = 0;
        const char *path = ce->name;
        int namelen = strlen(path);
        int stage = ce_stage(ce);
        char *pathbuf = xmalloc(namelen + 1);
        char *cp;

        memcpy(pathbuf, path, namelen + 1);

        /*
         * We are inserting path/file.  Do they have path registered at
         * the same stage?  We need to do this for all the levels of our
         * subpath.
         */
        cp = pathbuf;
        while (1) {
                char *ep = strchr(cp, '/');
                if (!ep)
                        break;
                *ep = 0;    /* first cut it at slash */
                pos = cache_name_pos(pathbuf,
                                     htons(create_ce_flags(ep-cp, stage)));
                if (0 <= pos) {
                        /* Our leading path component is registered as a file,
                         * and we are trying to make it a directory.  This is
                         * bad.
                         */
                        if (!ok_to_replace) {
                                free(pathbuf);
                                return -1;
                        }
                        fprintf(stderr, "removing file '%s' to replace it with a directory to create '%s'.\n", pathbuf, path);
                        remove_entry_at(pos);
                        replaced = 1;
                }
                *ep = '/';  /* then restore it and go downwards */
                cp = ep + 1;
        }
        free(pathbuf);

        /* Do we have an entry in the cache that makes our path a prefix
         * of it?  That is, are we creating a file where they already expect
         * a directory there?
         */
        pos = cache_name_pos(path,
                             htons(create_ce_flags(namelen, stage)));

        /* (0 <= pos) cannot happen because add_cache_entry()
         * should have taken care of that case.
         */
        pos = -pos-1;

        /* pos would point at an existing entry that would come immediately
         * after our path.  It could be the same as our path in higher stage,
         * or different path but in a lower stage.
         *
         * E.g. when we are inserting path at stage 2,
         *
         *        1 path
         * pos->  3 path
         *        2 path/file1
         *        3 path/file1
         *        2 path/file2
         *        2 patho
         *
         * We need to examine pos, ignore it because it is at different
         * stage, examine next to find the path/file at stage 2, and
         * complain.  We need to do this until we are not the leading
         * path of an existing entry anymore.
         */

        while (pos < active_nr) {
                struct cache_entry *other = active_cache[pos];
                if (strncmp(other->name, path, namelen))
                        break; /* it is not our "subdirectory" anymore */
                if ((ce_stage(other) == stage) &&
                    other->name[namelen] == '/') {
                        if (!ok_to_replace)
                                return -1;
                        fprintf(stderr, "removing file '%s' under '%s' to be replaced with a file\n", other->name, path);
                        remove_entry_at(pos);
                        replaced = 1;
                        continue; /* cycle without updating pos */
                }
                pos++;
        }
        return replaced;
}

int add_cache_entry(struct cache_entry *ce, int option)
{
        int pos;
        int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
        int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
        pos = cache_name_pos(ce->name, htons(ce->ce_flags));

        /* existing match? Just replace it */
        if (pos >= 0) {
                active_cache_changed = 1;
                active_cache[pos] = ce;
                return 0;
        }
        pos = -pos-1;

        /*
         * Inserting a merged entry ("stage 0") into the index
         * will always replace all non-merged entries..
         */
        if (pos < active_nr && ce_stage(ce) == 0) {
                while (same_name(active_cache[pos], ce)) {
                        ok_to_add = 1;
                        if (!remove_entry_at(pos))
                                break;
                }
        }

        if (!ok_to_add)
                return -1;

        if (check_file_directory_conflict(ce, ok_to_replace)) {
                if (!ok_to_replace)
                        return -1;
                pos = cache_name_pos(ce->name, htons(ce->ce_flags));
                pos = -pos-1;
        }

        /* Make sure the array is big enough .. */
        if (active_nr == active_alloc) {
                active_alloc = alloc_nr(active_alloc);
                active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
        }

        /* Add it in.. */
        active_nr++;
        if (active_nr > pos)
                memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
        active_cache[pos] = ce;
        active_cache_changed = 1;
        return 0;
}

static int verify_hdr(struct cache_header *hdr, unsigned long size)
{
        SHA_CTX c;
        unsigned char sha1[20];

        if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
                return error("bad signature");
        if (hdr->hdr_version != htonl(2))
                return error("bad index version");
        SHA1_Init(&c);
        SHA1_Update(&c, hdr, size - 20);
        SHA1_Final(sha1, &c);
        if (memcmp(sha1, (void *)hdr + size - 20, 20))
                return error("bad index file sha1 signature");
        return 0;
}

int read_cache(void)
{
        int fd, i;
        struct stat st;
        unsigned long size, offset;
        void *map;
        struct cache_header *hdr;

        errno = EBUSY;
        if (active_cache)
                return error("more than one cachefile");
        errno = ENOENT;
        fd = open(get_index_file(), O_RDONLY);
        if (fd < 0)
                return (errno == ENOENT) ? 0 : error("open failed");

        size = 0; // avoid gcc warning
        map = (void *)-1;
        if (!fstat(fd, &st)) {
                size = st.st_size;
                errno = EINVAL;
                if (size >= sizeof(struct cache_header) + 20)
                        map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
        }
        close(fd);
        if (-1 == (int)(long)map)
                return error("mmap failed");

        hdr = map;
        if (verify_hdr(hdr, size) < 0)
                goto unmap;

        active_nr = ntohl(hdr->hdr_entries);
        active_alloc = alloc_nr(active_nr);
        active_cache = calloc(active_alloc, sizeof(struct cache_entry *));

        offset = sizeof(*hdr);
        for (i = 0; i < active_nr; i++) {
                struct cache_entry *ce = map + offset;
                offset = offset + ce_size(ce);
                active_cache[i] = ce;
        }
        return active_nr;

unmap:
        munmap(map, size);
        errno = EINVAL;
        return error("verify header failed");
}

#define WRITE_BUFFER_SIZE 8192
static char write_buffer[WRITE_BUFFER_SIZE];
static unsigned long write_buffer_len;

static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
{
        while (len) {
                unsigned int buffered = write_buffer_len;
                unsigned int partial = WRITE_BUFFER_SIZE - buffered;
                if (partial > len)
                        partial = len;
                memcpy(write_buffer + buffered, data, partial);
                buffered += partial;
                if (buffered == WRITE_BUFFER_SIZE) {
                        SHA1_Update(context, write_buffer, WRITE_BUFFER_SIZE);
                        if (write(fd, write_buffer, WRITE_BUFFER_SIZE) != WRITE_BUFFER_SIZE)
                                return -1;
                        buffered = 0;
                }
                write_buffer_len = buffered;
                len -= partial;
                data += partial;
        }
        return 0;
}

static int ce_flush(SHA_CTX *context, int fd)
{
        unsigned int left = write_buffer_len;

        if (left) {
                write_buffer_len = 0;
                SHA1_Update(context, write_buffer, left);
        }

        /* Append the SHA1 signature at the end */
        SHA1_Final(write_buffer + left, context);
        left += 20;
        if (write(fd, write_buffer, left) != left)
                return -1;
        return 0;
}

int write_cache(int newfd, struct cache_entry **cache, int entries)
{
        SHA_CTX c;
        struct cache_header hdr;
        int i;

        hdr.hdr_signature = htonl(CACHE_SIGNATURE);
        hdr.hdr_version = htonl(2);
        hdr.hdr_entries = htonl(entries);

        SHA1_Init(&c);
        if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
                return -1;

        for (i = 0; i < entries; i++) {
                struct cache_entry *ce = cache[i];
                if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
                        return -1;
        }
        return ce_flush(&c, newfd);
}