#include "builtin.h"
#include "cache.h"
#include "object.h"
#include "blob.h"
#include "delta.h"
#include "pack.h"
#include "csum-file.h"

static int max_depth = 10;
static unsigned long object_count;
static int packfd;
static int current_depth;
static void *lastdat;
static unsigned long lastdatlen;
static unsigned char lastsha1[20];

static ssize_t yread(int fd, void *buffer, size_t length)
{
        ssize_t ret = 0;
        while (ret < length) {
                ssize_t size = xread(fd, (char *) buffer + ret, length - ret);
                if (size < 0) {
                        return size;
                }
                if (size == 0) {
                        return ret;
                }
                ret += size;
        }
        return ret;
}

static ssize_t ywrite(int fd, void *buffer, size_t length)
{
        ssize_t ret = 0;
        while (ret < length) {
                ssize_t size = xwrite(fd, (char *) buffer + ret, length - ret);
                if (size < 0) {
                        return size;
                }
                if (size == 0) {
                        return ret;
                }
                ret += size;
        }
        return ret;
}

static unsigned long encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
{
        int n = 1;
        unsigned char c;

        if (type < OBJ_COMMIT || type > OBJ_DELTA)
                die("bad type %d", type);

        c = (type << 4) | (size & 15);
        size >>= 4;
        while (size) {
                *hdr++ = c | 0x80;
                c = size & 0x7f;
                size >>= 7;
                n++;
        }
        *hdr = c;
        return n;
}

static void write_blob (void *dat, unsigned long datlen)
{
        z_stream s;
        void *out, *delta;
        unsigned char hdr[64];
        unsigned long hdrlen, deltalen;

        if (lastdat && current_depth < max_depth) {
                delta = diff_delta(lastdat, lastdatlen,
                        dat, datlen,
                        &deltalen, 0);
        } else
                delta = 0;

        memset(&s, 0, sizeof(s));
        deflateInit(&s, zlib_compression_level);

        if (delta) {
                current_depth++;
                s.next_in = delta;
                s.avail_in = deltalen;
                hdrlen = encode_header(OBJ_DELTA, deltalen, hdr);
                if (ywrite(packfd, hdr, hdrlen) != hdrlen)
                        die("Can't write object header: %s", strerror(errno));
                if (ywrite(packfd, lastsha1, sizeof(lastsha1)) != sizeof(lastsha1))
                        die("Can't write object base: %s", strerror(errno));
        } else {
                current_depth = 0;
                s.next_in = dat;
                s.avail_in = datlen;
                hdrlen = encode_header(OBJ_BLOB, datlen, hdr);
                if (ywrite(packfd, hdr, hdrlen) != hdrlen)
                        die("Can't write object header: %s", strerror(errno));
        }

        s.avail_out = deflateBound(&s, s.avail_in);
        s.next_out = out = xmalloc(s.avail_out);
        while (deflate(&s, Z_FINISH) == Z_OK)
                /* nothing */;
        deflateEnd(&s);

        if (ywrite(packfd, out, s.total_out) != s.total_out)
                die("Failed writing compressed data %s", strerror(errno));

        free(out);
        if (delta)
                free(delta);
}

static void init_pack_header ()
{
        const char* magic = "PACK";
        unsigned long version = 2;
        unsigned long zero = 0;

        version = htonl(version);

        if (ywrite(packfd, (char*)magic, 4) != 4)
                die("Can't write pack magic: %s", strerror(errno));
        if (ywrite(packfd, &version, 4) != 4)
                die("Can't write pack version: %s", strerror(errno));
        if (ywrite(packfd, &zero, 4) != 4)
                die("Can't write 0 object count: %s", strerror(errno));
}

static void fixup_header_footer ()
{
        SHA_CTX c;
        char hdr[8];
        unsigned char sha1[20];
        unsigned long cnt;
        char *buf;
        size_t n;

        if (lseek(packfd, 0, SEEK_SET) != 0)
                die("Failed seeking to start: %s", strerror(errno));

        SHA1_Init(&c);
        if (yread(packfd, hdr, 8) != 8)
                die("Failed reading header: %s", strerror(errno));
        SHA1_Update(&c, hdr, 8);

fprintf(stderr, "%lu objects\n", object_count);
        cnt = htonl(object_count);
        SHA1_Update(&c, &cnt, 4);
        if (ywrite(packfd, &cnt, 4) != 4)
                die("Failed writing object count: %s", strerror(errno));

        buf = xmalloc(128 * 1024);
        for (;;) {
                n = xread(packfd, buf, 128 * 1024);
                if (n <= 0)
                        break;
                SHA1_Update(&c, buf, n);
        }
        free(buf);

        SHA1_Final(sha1, &c);
        if (ywrite(packfd, sha1, sizeof(sha1)) != sizeof(sha1))
                die("Failed writing pack checksum: %s", strerror(errno));
}

int main (int argc, const char **argv)
{
        packfd = open(argv[1], O_RDWR|O_CREAT|O_TRUNC, 0666);
        if (packfd < 0)
                die("Can't create pack file %s: %s", argv[1], strerror(errno));

        init_pack_header();
        for (;;) {
                unsigned long datlen;
                int hdrlen;
                void *dat;
                char hdr[128];
                unsigned char sha1[20];
                SHA_CTX c;

                if (yread(0, &datlen, 4) != 4)
                        break;

                dat = xmalloc(datlen);
                if (yread(0, dat, datlen) != datlen)
                        break;

                hdrlen = sprintf(hdr, "blob %lu", datlen) + 1;
                SHA1_Init(&c);
                SHA1_Update(&c, hdr, hdrlen);
                SHA1_Update(&c, dat, datlen);
                SHA1_Final(sha1, &c);

                write_blob(dat, datlen);
                object_count++;
                printf("%s\n", sha1_to_hex(sha1));
                fflush(stdout);

                if (lastdat)
                        free(lastdat);
                lastdat = dat;
                lastdatlen = datlen;
                memcpy(lastsha1, sha1, sizeof(sha1));
        }
        fixup_header_footer();
        close(packfd);

        return 0;
}