#include "builtin.h"
#include "cache.h"
#include "object.h"
#include "delta.h"
#include "pack.h"
#include "blob.h"
#include "commit.h"
#include "tag.h"
#include "tree.h"

#include <sys/time.h>

static int dry_run, quiet;
static const char unpack_usage[] = "git-unpack-objects [-n] [-q] < pack-file";

/* We always read in 4kB chunks. */
static unsigned char buffer[4096];
static unsigned long offset, len;
static SHA_CTX ctx;

/*
 * Make sure at least "min" bytes are available in the buffer, and
 * return the pointer to the buffer.
 */
static void * fill(int min)
{
        if (min <= len)
                return buffer + offset;
        if (min > sizeof(buffer))
                die("cannot fill %d bytes", min);
        if (offset) {
                SHA1_Update(&ctx, buffer, offset);
                memcpy(buffer, buffer + offset, len);
                offset = 0;
        }
        do {
                int ret = xread(0, buffer + len, sizeof(buffer) - len);
                if (ret <= 0) {
                        if (!ret)
                                die("early EOF");
                        die("read error on input: %s", strerror(errno));
                }
                len += ret;
        } while (len < min);
        return buffer;
}

static void use(int bytes)
{
        if (bytes > len)
                die("used more bytes than were available");
        len -= bytes;
        offset += bytes;
}

static void *get_data(unsigned long size)
{
        z_stream stream;
        void *buf = xmalloc(size);

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

        stream.next_out = buf;
        stream.avail_out = size;
        stream.next_in = fill(1);
        stream.avail_in = len;
        inflateInit(&stream);

        for (;;) {
                int ret = inflate(&stream, 0);
                use(len - stream.avail_in);
                if (stream.total_out == size && ret == Z_STREAM_END)
                        break;
                if (ret != Z_OK)
                        die("inflate returned %d\n", ret);
                stream.next_in = fill(1);
                stream.avail_in = len;
        }
        inflateEnd(&stream);
        return buf;
}

struct delta_info {
        unsigned char base_sha1[20];
        unsigned long size;
        void *delta;
        struct delta_info *next;
};

static struct delta_info *delta_list;

static void add_delta_to_list(unsigned char *base_sha1, void *delta, unsigned long size)
{
        struct delta_info *info = xmalloc(sizeof(*info));

        hashcpy(info->base_sha1, base_sha1);
        info->size = size;
        info->delta = delta;
        info->next = delta_list;
        delta_list = info;
}

static void added_object(unsigned char *sha1, const char *type, void *data, unsigned long size);

static void write_object(void *buf, unsigned long size, const char *type)
{
        unsigned char sha1[20];
        if (write_sha1_file(buf, size, type, sha1) < 0)
                die("failed to write object");
        added_object(sha1, type, buf, size);
}

static int resolve_delta(const char *type,
        void *base, unsigned long base_size,
        void *delta, unsigned long delta_size)
{
        void *result;
        unsigned long result_size;

        result = patch_delta(base, base_size,
                             delta, delta_size,
                             &result_size);
        if (!result)
                die("failed to apply delta");
        free(delta);
        write_object(result, result_size, type);
        free(result);
        return 0;
}

static void added_object(unsigned char *sha1, const char *type, void *data, unsigned long size)
{
        struct delta_info **p = &delta_list;
        struct delta_info *info;

        while ((info = *p) != NULL) {
                if (!hashcmp(info->base_sha1, sha1)) {
                        *p = info->next;
                        p = &delta_list;
                        resolve_delta(type, data, size, info->delta, info->size);
                        free(info);
                        continue;
                }
                p = &info->next;
        }
}

static int unpack_non_delta_entry(enum object_type kind, unsigned long size)
{
        void *buf = get_data(size);
        const char *type;

        switch (kind) {
        case OBJ_COMMIT: type = commit_type; break;
        case OBJ_TREE:   type = tree_type; break;
        case OBJ_BLOB:   type = blob_type; break;
        case OBJ_TAG:    type = tag_type; break;
        default: die("bad type %d", kind);
        }
        if (!dry_run)
                write_object(buf, size, type);
        free(buf);
        return 0;
}

static int unpack_delta_entry(unsigned long delta_size)
{
        void *delta_data, *base;
        unsigned long base_size;
        char type[20];
        unsigned char base_sha1[20];
        int result;

        hashcpy(base_sha1, fill(20));
        use(20);

        delta_data = get_data(delta_size);
        if (dry_run) {
                free(delta_data);
                return 0;
        }

        if (!has_sha1_file(base_sha1)) {
                add_delta_to_list(base_sha1, delta_data, delta_size);
                return 0;
        }
        base = read_sha1_file(base_sha1, type, &base_size);
        if (!base)
                die("failed to read delta-pack base object %s", sha1_to_hex(base_sha1));
        result = resolve_delta(type, base, base_size, delta_data, delta_size);
        free(base);
        return result;
}

static void unpack_one(unsigned nr, unsigned total)
{
        unsigned shift;
        unsigned char *pack, c;
        unsigned long size;
        enum object_type type;

        pack = fill(1);
        c = *pack;
        use(1);
        type = (c >> 4) & 7;
        size = (c & 15);
        shift = 4;
        while (c & 0x80) {
                pack = fill(1);
                c = *pack++;
                use(1);
                size += (c & 0x7f) << shift;
                shift += 7;
        }
        if (!quiet) {
                static unsigned long last_sec;
                static unsigned last_percent;
                struct timeval now;
                unsigned percentage = (nr * 100) / total;

                gettimeofday(&now, NULL);
                if (percentage != last_percent || now.tv_sec != last_sec) {
                        last_sec = now.tv_sec;
                        last_percent = percentage;
                        fprintf(stderr, "%4u%% (%u/%u) done\r", percentage, nr, total);
                }
        }
        switch (type) {
        case OBJ_COMMIT:
        case OBJ_TREE:
        case OBJ_BLOB:
        case OBJ_TAG:
                unpack_non_delta_entry(type, size);
                return;
        case OBJ_DELTA:
                unpack_delta_entry(size);
                return;
        default:
                die("bad object type %d", type);
        }
}

static void unpack_all(void)
{
        int i;
        struct pack_header *hdr = fill(sizeof(struct pack_header));
        unsigned nr_objects = ntohl(hdr->hdr_entries);

        if (ntohl(hdr->hdr_signature) != PACK_SIGNATURE)
                die("bad pack file");
        if (!pack_version_ok(hdr->hdr_version))
                die("unknown pack file version %d", ntohl(hdr->hdr_version));
        fprintf(stderr, "Unpacking %d objects\n", nr_objects);

        use(sizeof(struct pack_header));
        for (i = 0; i < nr_objects; i++)
                unpack_one(i+1, nr_objects);
        if (delta_list)
                die("unresolved deltas left after unpacking");
}

int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
{
        int i;
        unsigned char sha1[20];

        git_config(git_default_config);

        quiet = !isatty(2);

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

                if (*arg == '-') {
                        if (!strcmp(arg, "-n")) {
                                dry_run = 1;
                                continue;
                        }
                        if (!strcmp(arg, "-q")) {
                                quiet = 1;
                                continue;
                        }
                        usage(unpack_usage);
                }

                /* We don't take any non-flag arguments now.. Maybe some day */
                usage(unpack_usage);
        }
        SHA1_Init(&ctx);
        unpack_all();
        SHA1_Update(&ctx, buffer, offset);
        SHA1_Final(sha1, &ctx);
        if (hashcmp(fill(20), sha1))
                die("final sha1 did not match");
        use(20);

        /* Write the last part of the buffer to stdout */
        while (len) {
                int ret = xwrite(1, buffer + offset, len);
                if (ret <= 0)
                        break;
                len -= ret;
                offset += ret;
        }

        /* All done */
        if (!quiet)
                fprintf(stderr, "\n");
        return 0;
}