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

struct object_entry
{
        struct object_entry *next;
        unsigned long offset;
        unsigned char sha1[20];
};

struct object_entry_block
{
        struct object_entry_block *next_block;
        struct object_entry *next_free;
        struct object_entry *end;
        struct object_entry entries[FLEX_ARRAY]; /* more */
};

struct last_object
{
        void *data;
        unsigned long len;
        int depth;
        unsigned char sha1[20];
};

/* Stats and misc. counters. */
static int max_depth = 10;
static unsigned long alloc_count;
static unsigned long object_count;
static unsigned long duplicate_count;

/* The .pack file */
static int pack_fd;
static unsigned long pack_offset;
static unsigned char pack_sha1[20];

/* Table of objects we've written. */
struct object_entry_block *blocks;
struct object_entry *object_table[1 << 16];

/* Our last blob */
struct last_object last_blob;

static void alloc_objects(int cnt)
{
        struct object_entry_block *b;

        b = xmalloc(sizeof(struct object_entry_block)
                + cnt * sizeof(struct object_entry));
        b->next_block = blocks;
        b->next_free = b->entries;
        b->end = b->entries + cnt;
        blocks = b;
        alloc_count += cnt;
}

static struct object_entry* new_object(unsigned char *sha1)
{
        struct object_entry *e;

        if (blocks->next_free == blocks->end)
                alloc_objects(1000);

        e = blocks->next_free++;
        memcpy(e->sha1, sha1, sizeof(e->sha1));
        return e;
}

static struct object_entry* insert_object(unsigned char *sha1)
{
        unsigned int h = sha1[0] << 8 | sha1[1];
        struct object_entry *e = object_table[h];
        struct object_entry *p = 0;

        while (e) {
                if (!memcmp(sha1, e->sha1, sizeof(e->sha1)))
                        return e;
                p = e;
                e = e->next;
        }

        e = new_object(sha1);
        e->next = 0;
        e->offset = 0;
        if (p)
                p->next = e;
        else
                object_table[h] = e;
        return e;
}

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 int store_object(
        enum object_type type,
        void *dat,
        unsigned long datlen,
        struct last_object *last)
{
        void *out, *delta;
        struct object_entry *e;
        unsigned char hdr[96];
        unsigned char sha1[20];
        unsigned long hdrlen, deltalen;
        SHA_CTX c;
        z_stream s;

        hdrlen = sprintf((char*)hdr,"%s %lu",type_names[type],datlen) + 1;
        SHA1_Init(&c);
        SHA1_Update(&c, hdr, hdrlen);
        SHA1_Update(&c, dat, datlen);
        SHA1_Final(sha1, &c);

        e = insert_object(sha1);
        if (e->offset) {
                duplicate_count++;
                return 0;
        }
        e->offset = pack_offset;
        object_count++;

        if (last->data && last->depth < max_depth)
                delta = diff_delta(last->data, last->len,
                        dat, datlen,
                        &deltalen, 0);
        else
                delta = 0;

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

        if (delta) {
                last->depth++;
                s.next_in = delta;
                s.avail_in = deltalen;
                hdrlen = encode_header(OBJ_DELTA, deltalen, hdr);
                if (ywrite(pack_fd, hdr, hdrlen) != hdrlen)
                        die("Can't write object header: %s", strerror(errno));
                if (ywrite(pack_fd, last->sha1, sizeof(sha1)) != sizeof(sha1))
                        die("Can't write object base: %s", strerror(errno));
                pack_offset += hdrlen + sizeof(sha1);
        } else {
                last->depth = 0;
                s.next_in = dat;
                s.avail_in = datlen;
                hdrlen = encode_header(type, datlen, hdr);
                if (ywrite(pack_fd, hdr, hdrlen) != hdrlen)
                        die("Can't write object header: %s", strerror(errno));
                pack_offset += hdrlen;
        }

        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(pack_fd, out, s.total_out) != s.total_out)
                die("Failed writing compressed data %s", strerror(errno));
        pack_offset += s.total_out;

        free(out);
        if (delta)
                free(delta);
        if (last->data)
                free(last->data);
        last->data = dat;
        last->len = datlen;
        memcpy(last->sha1, sha1, sizeof(sha1));
        return 1;
}

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

        version = htonl(version);

        if (ywrite(pack_fd, (char*)magic, 4) != 4)
                die("Can't write pack magic: %s", strerror(errno));
        if (ywrite(pack_fd, &version, 4) != 4)
                die("Can't write pack version: %s", strerror(errno));
        if (ywrite(pack_fd, &zero, 4) != 4)
                die("Can't write 0 object count: %s", strerror(errno));
        pack_offset = 4 * 3;
}

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

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

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

        cnt = htonl(object_count);
        SHA1_Update(&c, &cnt, 4);
        if (ywrite(pack_fd, &cnt, 4) != 4)
                die("Failed writing object count: %s", strerror(errno));

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

        SHA1_Final(pack_sha1, &c);
        if (ywrite(pack_fd, pack_sha1, sizeof(pack_sha1)) != sizeof(pack_sha1))
                die("Failed writing pack checksum: %s", strerror(errno));
}

static int oecmp (const void *_a, const void *_b)
{
        struct object_entry *a = *((struct object_entry**)_a);
        struct object_entry *b = *((struct object_entry**)_b);
        return memcmp(a->sha1, b->sha1, sizeof(a->sha1));
}

static void write_index(const char *idx_name)
{
        struct sha1file *f;
        struct object_entry **idx, **c, **last;
        struct object_entry *e;
        struct object_entry_block *o;
        unsigned int array[256];
        int i;

        /* Build the sorted table of object IDs. */
        idx = xmalloc(object_count * sizeof(struct object_entry*));
        c = idx;
        for (o = blocks; o; o = o->next_block)
                for (e = o->entries; e != o->next_free; e++)
                        *c++ = e;
        last = idx + object_count;
        qsort(idx, object_count, sizeof(struct object_entry*), oecmp);

        /* Generate the fan-out array. */
        c = idx;
        for (i = 0; i < 256; i++) {
                struct object_entry **next = c;;
                while (next < last) {
                        if ((*next)->sha1[0] != i)
                                break;
                        next++;
                }
                array[i] = htonl(next - idx);
                c = next;
        }

        f = sha1create("%s", idx_name);
        sha1write(f, array, 256 * sizeof(int));
        for (c = idx; c != last; c++) {
                unsigned int offset = htonl((*c)->offset);
                sha1write(f, &offset, 4);
                sha1write(f, (*c)->sha1, sizeof((*c)->sha1));
        }
        sha1write(f, pack_sha1, sizeof(pack_sha1));
        sha1close(f, NULL, 1);
        free(idx);
}

int main(int argc, const char **argv)
{
        const char *base_name = argv[1];
        int est_obj_cnt = atoi(argv[2]);
        char *pack_name;
        char *idx_name;

        pack_name = xmalloc(strlen(base_name) + 6);
        sprintf(pack_name, "%s.pack", base_name);
        idx_name = xmalloc(strlen(base_name) + 5);
        sprintf(idx_name, "%s.idx", base_name);

        pack_fd = open(pack_name, O_RDWR|O_CREAT|O_EXCL, 0666);
        if (pack_fd < 0)
                die("Can't create pack file %s: %s", pack_name, strerror(errno));

        alloc_objects(est_obj_cnt);
        init_pack_header();
        for (;;) {
                unsigned long datlen;
                void *dat;

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

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

                if (!store_object(OBJ_BLOB, dat, datlen, &last_blob))
                        free(dat);
        }
        fixup_header_footer();
        close(pack_fd);
        write_index(idx_name);

        fprintf(stderr, "%lu objects, %lu duplicates, %lu allocated (%lu overflow)\n",
                object_count, duplicate_count, alloc_count, alloc_count - est_obj_cnt);

        return 0;
}