#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 "tree-walk.h"
#include "progress.h"
#include "decorate.h"
#include "fsck.h"

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

/* We always read in 4kB chunks. */
static unsigned char buffer[4096];
static unsigned int offset, len;
static off_t consumed_bytes;
static git_SHA_CTX ctx;

/*
 * When running under --strict mode, objects whose reachability are
 * suspect are kept in core without getting written in the object
 * store.
 */
struct obj_buffer {
        char *buffer;
        unsigned long size;
};

static struct decoration obj_decorate;

static struct obj_buffer *lookup_object_buffer(struct object *base)
{
        return lookup_decoration(&obj_decorate, base);
}

static void add_object_buffer(struct object *object, char *buffer, unsigned long size)
{
        struct obj_buffer *obj;
        obj = xcalloc(1, sizeof(struct obj_buffer));
        obj->buffer = buffer;
        obj->size = size;
        if (add_decoration(&obj_decorate, object, obj))
                die("object %s tried to add buffer twice!", sha1_to_hex(object->sha1));
}

/*
 * 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) {
                git_SHA1_Update(&ctx, buffer, offset);
                memmove(buffer, buffer + offset, len);
                offset = 0;
        }
        do {
                ssize_t ret = xread(0, buffer + len, sizeof(buffer) - len);
                if (ret <= 0) {
                        if (!ret)
                                die("early EOF");
                        die_errno("read error on input");
                }
                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;

        /* make sure off_t is sufficiently large not to wrap */
        if (signed_add_overflows(consumed_bytes, bytes))
                die("pack too large for current definition of off_t");
        consumed_bytes += bytes;
}

static void *get_data(unsigned long size)
{
        git_zstream stream;
        void *buf = xmallocz(size);

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

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

        for (;;) {
                int ret = git_inflate(&stream, 0);
                use(len - stream.avail_in);
                if (stream.total_out == size && ret == Z_STREAM_END)
                        break;
                if (ret != Z_OK) {
                        error("inflate returned %d", ret);
                        free(buf);
                        buf = NULL;
                        if (!recover)
                                exit(1);
                        has_errors = 1;
                        break;
                }
                stream.next_in = fill(1);
                stream.avail_in = len;
        }
        git_inflate_end(&stream);
        return buf;
}

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

static struct delta_info *delta_list;

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

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

struct obj_info {
        off_t offset;
        unsigned char sha1[20];
        struct object *obj;
};

#define FLAG_OPEN (1u<<20)
#define FLAG_WRITTEN (1u<<21)

static struct obj_info *obj_list;
static unsigned nr_objects;

/*
 * Called only from check_object() after it verified this object
 * is Ok.
 */
static void write_cached_object(struct object *obj, struct obj_buffer *obj_buf)
{
        unsigned char sha1[20];

        if (write_sha1_file(obj_buf->buffer, obj_buf->size, typename(obj->type), sha1) < 0)
                die("failed to write object %s", sha1_to_hex(obj->sha1));
        obj->flags |= FLAG_WRITTEN;
}

/*
 * At the very end of the processing, write_rest() scans the objects
 * that have reachability requirements and calls this function.
 * Verify its reachability and validity recursively and write it out.
 */
static int check_object(struct object *obj, int type, void *data)
{
        struct obj_buffer *obj_buf;

        if (!obj)
                return 1;

        if (obj->flags & FLAG_WRITTEN)
                return 0;

        if (type != OBJ_ANY && obj->type != type)
                die("object type mismatch");

        if (!(obj->flags & FLAG_OPEN)) {
                unsigned long size;
                int type = sha1_object_info(obj->sha1, &size);
                if (type != obj->type || type <= 0)
                        die("object of unexpected type");
                obj->flags |= FLAG_WRITTEN;
                return 0;
        }

        obj_buf = lookup_object_buffer(obj);
        if (!obj_buf)
                die("Whoops! Cannot find object '%s'", sha1_to_hex(obj->sha1));
        if (fsck_object(obj, obj_buf->buffer, obj_buf->size, 1,
                        fsck_error_function))
                die("Error in object");
        if (fsck_walk(obj, check_object, NULL))
                die("Error on reachable objects of %s", sha1_to_hex(obj->sha1));
        write_cached_object(obj, obj_buf);
        return 0;
}

static void write_rest(void)
{
        unsigned i;
        for (i = 0; i < nr_objects; i++) {
                if (obj_list[i].obj)
                        check_object(obj_list[i].obj, OBJ_ANY, NULL);
        }
}

static void added_object(unsigned nr, enum object_type type,
                         void *data, unsigned long size);

/*
 * Write out nr-th object from the list, now we know the contents
 * of it.  Under --strict, this buffers structured objects in-core,
 * to be checked at the end.
 */
static void write_object(unsigned nr, enum object_type type,
                         void *buf, unsigned long size)
{
        if (!strict) {
                if (write_sha1_file(buf, size, typename(type), obj_list[nr].sha1) < 0)
                        die("failed to write object");
                added_object(nr, type, buf, size);
                free(buf);
                obj_list[nr].obj = NULL;
        } else if (type == OBJ_BLOB) {
                struct blob *blob;
                if (write_sha1_file(buf, size, typename(type), obj_list[nr].sha1) < 0)
                        die("failed to write object");
                added_object(nr, type, buf, size);
                free(buf);

                blob = lookup_blob(obj_list[nr].sha1);
                if (blob)
                        blob->object.flags |= FLAG_WRITTEN;
                else
                        die("invalid blob object");
                obj_list[nr].obj = NULL;
        } else {
                struct object *obj;
                int eaten;
                hash_sha1_file(buf, size, typename(type), obj_list[nr].sha1);
                added_object(nr, type, buf, size);
                obj = parse_object_buffer(obj_list[nr].sha1, type, size, buf, &eaten);
                if (!obj)
                        die("invalid %s", typename(type));
                add_object_buffer(obj, buf, size);
                obj->flags |= FLAG_OPEN;
                obj_list[nr].obj = obj;
        }
}

static void resolve_delta(unsigned nr, enum object_type 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(nr, type, result, result_size);
}

/*
 * We now know the contents of an object (which is nr-th in the pack);
 * resolve all the deltified objects that are based on it.
 */
static void added_object(unsigned nr, enum object_type 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, obj_list[nr].sha1) ||
                    info->base_offset == obj_list[nr].offset) {
                        *p = info->next;
                        p = &delta_list;
                        resolve_delta(info->nr, type, data, size,
                                      info->delta, info->size);
                        free(info);
                        continue;
                }
                p = &info->next;
        }
}

static void unpack_non_delta_entry(enum object_type type, unsigned long size,
                                   unsigned nr)
{
        void *buf = get_data(size);

        if (!dry_run && buf)
                write_object(nr, type, buf, size);
        else
                free(buf);
}

static int resolve_against_held(unsigned nr, const unsigned char *base,
                                void *delta_data, unsigned long delta_size)
{
        struct object *obj;
        struct obj_buffer *obj_buffer;
        obj = lookup_object(base);
        if (!obj)
                return 0;
        obj_buffer = lookup_object_buffer(obj);
        if (!obj_buffer)
                return 0;
        resolve_delta(nr, obj->type, obj_buffer->buffer,
                      obj_buffer->size, delta_data, delta_size);
        return 1;
}

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

        if (type == OBJ_REF_DELTA) {
                hashcpy(base_sha1, fill(20));
                use(20);
                delta_data = get_data(delta_size);
                if (dry_run || !delta_data) {
                        free(delta_data);
                        return;
                }
                if (has_sha1_file(base_sha1))
                        ; /* Ok we have this one */
                else if (resolve_against_held(nr, base_sha1,
                                              delta_data, delta_size))
                        return; /* we are done */
                else {
                        /* cannot resolve yet --- queue it */
                        hashcpy(obj_list[nr].sha1, null_sha1);
                        add_delta_to_list(nr, base_sha1, 0, delta_data, delta_size);
                        return;
                }
        } else {
                unsigned base_found = 0;
                unsigned char *pack, c;
                off_t base_offset;
                unsigned lo, mid, hi;

                pack = fill(1);
                c = *pack;
                use(1);
                base_offset = c & 127;
                while (c & 128) {
                        base_offset += 1;
                        if (!base_offset || MSB(base_offset, 7))
                                die("offset value overflow for delta base object");
                        pack = fill(1);
                        c = *pack;
                        use(1);
                        base_offset = (base_offset << 7) + (c & 127);
                }
                base_offset = obj_list[nr].offset - base_offset;
                if (base_offset <= 0 || base_offset >= obj_list[nr].offset)
                        die("offset value out of bound for delta base object");

                delta_data = get_data(delta_size);
                if (dry_run || !delta_data) {
                        free(delta_data);
                        return;
                }
                lo = 0;
                hi = nr;
                while (lo < hi) {
                        mid = (lo + hi)/2;
                        if (base_offset < obj_list[mid].offset) {
                                hi = mid;
                        } else if (base_offset > obj_list[mid].offset) {
                                lo = mid + 1;
                        } else {
                                hashcpy(base_sha1, obj_list[mid].sha1);
                                base_found = !is_null_sha1(base_sha1);
                                break;
                        }
                }
                if (!base_found) {
                        /*
                         * The delta base object is itself a delta that
                         * has not been resolved yet.
                         */
                        hashcpy(obj_list[nr].sha1, null_sha1);
                        add_delta_to_list(nr, null_sha1, base_offset, delta_data, delta_size);
                        return;
                }
        }

        if (resolve_against_held(nr, base_sha1, delta_data, delta_size))
                return;

        base = read_sha1_file(base_sha1, &type, &base_size);
        if (!base) {
                error("failed to read delta-pack base object %s",
                      sha1_to_hex(base_sha1));
                if (!recover)
                        exit(1);
                has_errors = 1;
                return;
        }
        resolve_delta(nr, type, base, base_size, delta_data, delta_size);
        free(base);
}

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

        obj_list[nr].offset = consumed_bytes;

        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;
        }

        switch (type) {
        case OBJ_COMMIT:
        case OBJ_TREE:
        case OBJ_BLOB:
        case OBJ_TAG:
                unpack_non_delta_entry(type, size, nr);
                return;
        case OBJ_REF_DELTA:
        case OBJ_OFS_DELTA:
                unpack_delta_entry(type, size, nr);
                return;
        default:
                error("bad object type %d", type);
                has_errors = 1;
                if (recover)
                        return;
                exit(1);
        }
}

static void unpack_all(void)
{
        int i;
        struct progress *progress = NULL;
        struct pack_header *hdr = fill(sizeof(struct pack_header));

        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 %"PRIu32,
                        ntohl(hdr->hdr_version));
        use(sizeof(struct pack_header));

        if (!quiet)
                progress = start_progress(_("Unpacking objects"), nr_objects);
        obj_list = xcalloc(nr_objects, sizeof(*obj_list));
        for (i = 0; i < nr_objects; i++) {
                unpack_one(i);
                display_progress(progress, i + 1);
        }
        stop_progress(&progress);

        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];

        check_replace_refs = 0;

        git_config(git_default_config, NULL);

        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;
                        }
                        if (!strcmp(arg, "-r")) {
                                recover = 1;
                                continue;
                        }
                        if (!strcmp(arg, "--strict")) {
                                strict = 1;
                                continue;
                        }
                        if (starts_with(arg, "--pack_header=")) {
                                struct pack_header *hdr;
                                char *c;

                                hdr = (struct pack_header *)buffer;
                                hdr->hdr_signature = htonl(PACK_SIGNATURE);
                                hdr->hdr_version = htonl(strtoul(arg + 14, &c, 10));
                                if (*c != ',')
                                        die("bad %s", arg);
                                hdr->hdr_entries = htonl(strtoul(c + 1, &c, 10));
                                if (*c)
                                        die("bad %s", arg);
                                len = sizeof(*hdr);
                                continue;
                        }
                        usage(unpack_usage);
                }

                /* We don't take any non-flag arguments now.. Maybe some day */
                usage(unpack_usage);
        }
        git_SHA1_Init(&ctx);
        unpack_all();
        git_SHA1_Update(&ctx, buffer, offset);
        git_SHA1_Final(sha1, &ctx);
        if (strict)
                write_rest();
        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 */
        return has_errors;
}