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

const char *sha1_file_directory = NULL;
struct cache_entry **active_cache = NULL;
unsigned int active_nr = 0, active_alloc = 0;

void usage(const char *err)
{
        fprintf(stderr, "usage: %s\n", err);
        exit(1);
}

static void report(const char *prefix, const char *err, va_list params)
{
        fputs(prefix, stderr);
        vfprintf(stderr, err, params);
        fputs("\n", stderr);
}

void die(const char *err, ...)
{
        va_list params;

        va_start(params, err);
        report("fatal: ", err, params);
        va_end(params);
        exit(1);
}

int error(const char *err, ...)
{
        va_list params;

        va_start(params, err);
        report("error: ", err, params);
        va_end(params);
        return -1;
}


static unsigned hexval(char c)
{
        if (c >= '0' && c <= '9')
                return c - '0';
        if (c >= 'a' && c <= 'f')
                return c - 'a' + 10;
        if (c >= 'A' && c <= 'F')
                return c - 'A' + 10;
        return ~0;
}

int get_sha1_hex(const char *hex, unsigned char *sha1)
{
        int i;
        for (i = 0; i < 20; i++) {
                unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
                if (val & ~0xff)
                        return -1;
                *sha1++ = val;
                hex += 2;
        }
        return 0;
}

char * sha1_to_hex(const unsigned char *sha1)
{
        static char buffer[50];
        static const char hex[] = "0123456789abcdef";
        char *buf = buffer;
        int i;

        for (i = 0; i < 20; i++) {
                unsigned int val = *sha1++;
                *buf++ = hex[val >> 4];
                *buf++ = hex[val & 0xf];
        }
        return buffer;
}

/*
 * NOTE! This returns a statically allocated buffer, so you have to be
 * careful about using it. Do a "strdup()" if you need to save the
 * filename.
 */
char *sha1_file_name(const unsigned char *sha1)
{
        int i;
        static char *name, *base;

        if (!base) {
                char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
                int len = strlen(sha1_file_directory);
                base = malloc(len + 60);
                memcpy(base, sha1_file_directory, len);
                memset(base+len, 0, 60);
                base[len] = '/';
                base[len+3] = '/';
                name = base + len + 1;
        }
        for (i = 0; i < 20; i++) {
                static char hex[] = "0123456789abcdef";
                unsigned int val = sha1[i];
                char *pos = name + i*2 + (i > 0);
                *pos++ = hex[val >> 4];
                *pos = hex[val & 0xf];
        }
        return base;
}

int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size)
{
        unsigned char real_sha1[20];
        SHA_CTX c;

        SHA1_Init(&c);
        SHA1_Update(&c, map, size);
        SHA1_Final(real_sha1, &c);
        return memcmp(sha1, real_sha1, 20) ? -1 : 0;
}

void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
{
        char *filename = sha1_file_name(sha1);
        int fd = open(filename, O_RDONLY);
        struct stat st;
        void *map;

        if (fd < 0) {
                perror(filename);
                return NULL;
        }
        if (fstat(fd, &st) < 0) {
                close(fd);
                return NULL;
        }
        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
        close(fd);
        if (-1 == (int)(long)map)
                return NULL;
        *size = st.st_size;
        return map;
}

void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
{
        int ret, bytes;
        z_stream stream;
        char buffer[8192];
        char *buf;

        /* Get the data stream */
        memset(&stream, 0, sizeof(stream));
        stream.next_in = map;
        stream.avail_in = mapsize;
        stream.next_out = buffer;
        stream.avail_out = sizeof(buffer);

        inflateInit(&stream);
        ret = inflate(&stream, 0);
        if (sscanf(buffer, "%10s %lu", type, size) != 2)
                return NULL;

        bytes = strlen(buffer) + 1;
        buf = malloc(*size);
        if (!buf)
                return NULL;

        memcpy(buf, buffer + bytes, stream.total_out - bytes);
        bytes = stream.total_out - bytes;
        if (bytes < *size && ret == Z_OK) {
                stream.next_out = buf + bytes;
                stream.avail_out = *size - bytes;
                while (inflate(&stream, Z_FINISH) == Z_OK)
                        /* nothing */;
        }
        inflateEnd(&stream);
        return buf;
}

void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
{
        unsigned long mapsize;
        void *map, *buf;

        map = map_sha1_file(sha1, &mapsize);
        if (map) {
                buf = unpack_sha1_file(map, mapsize, type, size);
                munmap(map, mapsize);
                return buf;
        }
        return NULL;
}

int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
{
        int size;
        char *compressed;
        z_stream stream;
        unsigned char sha1[20];
        SHA_CTX c;

        /* Set it up */
        memset(&stream, 0, sizeof(stream));
        deflateInit(&stream, Z_BEST_COMPRESSION);
        size = deflateBound(&stream, len);
        compressed = malloc(size);

        /* Compress it */
        stream.next_in = buf;
        stream.avail_in = len;
        stream.next_out = compressed;
        stream.avail_out = size;
        while (deflate(&stream, Z_FINISH) == Z_OK)
                /* nothing */;
        deflateEnd(&stream);
        size = stream.total_out;

        /* Sha1.. */
        SHA1_Init(&c);
        SHA1_Update(&c, compressed, size);
        SHA1_Final(sha1, &c);

        if (write_sha1_buffer(sha1, compressed, size) < 0)
                return -1;
        if (returnsha1)
                memcpy(returnsha1, sha1, 20);
        return 0;
}

static inline int collision_check(char *filename, void *buf, unsigned int size)
{
#ifdef COLLISION_CHECK
        void *map;
        int fd = open(filename, O_RDONLY);
        struct stat st;
        int cmp;

        /* Unreadable object, or object went away? Strange. */
        if (fd < 0)
                return -1;

        if (fstat(fd, &st) < 0 || size != st.st_size)
                return -1;

        map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
        close(fd);
        if (map == MAP_FAILED)
                return -1;
        cmp = memcmp(buf, map, size);
        munmap(map, size);
        if (cmp)
                return -1;
#endif
        return 0;
}

int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
{
        char *filename = sha1_file_name(sha1);
        int fd;

        fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
        if (fd < 0) {
                if (errno != EEXIST)
                        return -1;
                if (collision_check(filename, buf, size))
                        return error("SHA1 collision detected!"
                                        " This is bad, bad, BAD!\a\n");
                return 0;
        }
        write(fd, buf, size);
        close(fd);
        return 0;
}

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

        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;
        /* We consider only the owner x bit to be relevant for "mode changes" */
        if (0100 & (ntohs(ce->ce_mode) ^ st->st_mode))
                changed |= MODE_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.. */
static int remove_entry_at(int pos)
{
        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)
                remove_entry_at(pos);
        return 0;
}

static 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);
}

int add_cache_entry(struct cache_entry *ce, int ok_to_add)
{
        int pos;

        pos = cache_name_pos(ce->name, htons(ce->ce_flags));

        /* existing match? Just replace it */
        if (pos >= 0) {
                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;
                        active_nr--;
                        if (!remove_entry_at(pos))
                                break;
                }
        }

        if (!ok_to_add)
                return -1;

        /* Make sure the array is big enough .. */
        if (active_nr == active_alloc) {
                active_alloc = alloc_nr(active_alloc);
                active_cache = realloc(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;
        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(1))
                return error("bad version");
        SHA1_Init(&c);
        SHA1_Update(&c, hdr, offsetof(struct cache_header, sha1));
        SHA1_Update(&c, hdr+1, size - sizeof(*hdr));
        SHA1_Final(sha1, &c);
        if (memcmp(sha1, hdr->sha1, 20))
                return error("bad header sha1");
        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;
        sha1_file_directory = getenv(DB_ENVIRONMENT);
        if (!sha1_file_directory)
                sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
        if (access(sha1_file_directory, X_OK) < 0)
                return error("no access to SHA1 file directory");
        fd = open(".git/index", 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))
                        map = mmap(NULL, size, PROT_READ, 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");
}

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(1);
        hdr.hdr_entries = htonl(entries);

        SHA1_Init(&c);
        SHA1_Update(&c, &hdr, offsetof(struct cache_header, sha1));
        for (i = 0; i < entries; i++) {
                struct cache_entry *ce = cache[i];
                int size = ce_size(ce);
                SHA1_Update(&c, ce, size);
        }
        SHA1_Final(hdr.sha1, &c);

        if (write(newfd, &hdr, sizeof(hdr)) != sizeof(hdr))
                return -1;

        for (i = 0; i < entries; i++) {
                struct cache_entry *ce = cache[i];
                int size = ce_size(ce);
                if (write(newfd, ce, size) != size)
                        return -1;
        }
        return 0;
}