#include "cache.h"
#include "delta.h"
#include "pack.h"
#include "csum-file.h"
#include "blob.h"
#include "commit.h"
#include "tag.h"
#include "tree.h"

static const char index_pack_usage[] =
"git-index-pack [-o index-file] pack-file";

struct object_entry
{
        unsigned long offset;
        unsigned long size;
        unsigned int hdr_size;
        enum object_type type;
        enum object_type real_type;
        unsigned char sha1[20];
};

union delta_base {
        unsigned char sha1[20];
        unsigned long offset;
};

/*
 * Even if sizeof(union delta_base) == 24 on 64-bit archs, we really want
 * to memcmp() only the first 20 bytes.
 */
#define UNION_BASE_SZ   20

struct delta_entry
{
        struct object_entry *obj;
        union delta_base base;
};

static const char *pack_name;
static struct object_entry *objects;
static struct delta_entry *deltas;
static int nr_objects;
static int nr_deltas;

/* We always read in 4kB chunks. */
static unsigned char input_buffer[4096];
static unsigned long input_offset, input_len, consumed_bytes;
static SHA_CTX input_ctx;
static int input_fd;

/*
 * 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 <= input_len)
                return input_buffer + input_offset;
        if (min > sizeof(input_buffer))
                die("cannot fill %d bytes", min);
        if (input_offset) {
                SHA1_Update(&input_ctx, input_buffer, input_offset);
                memmove(input_buffer, input_buffer + input_offset, input_len);
                input_offset = 0;
        }
        do {
                int ret = xread(input_fd, input_buffer + input_len,
                                sizeof(input_buffer) - input_len);
                if (ret <= 0) {
                        if (!ret)
                                die("early EOF");
                        die("read error on input: %s", strerror(errno));
                }
                input_len += ret;
        } while (input_len < min);
        return input_buffer;
}

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

static void open_pack_file(void)
{
        input_fd = open(pack_name, O_RDONLY);
        if (input_fd < 0)
                die("cannot open packfile '%s': %s", pack_name,
                    strerror(errno));
        SHA1_Init(&input_ctx);
}

static void parse_pack_header(void)
{
        struct pack_header *hdr = fill(sizeof(struct pack_header));

        /* Header consistency check */
        if (hdr->hdr_signature != htonl(PACK_SIGNATURE))
                die("packfile '%s' signature mismatch", pack_name);
        if (!pack_version_ok(hdr->hdr_version))
                die("packfile '%s' version %d unsupported",
                    pack_name, ntohl(hdr->hdr_version));

        nr_objects = ntohl(hdr->hdr_entries);
        use(sizeof(struct pack_header));
        /*fprintf(stderr, "Indexing %d objects\n", nr_objects);*/
}

static void bad_object(unsigned long offset, const char *format,
                       ...) NORETURN __attribute__((format (printf, 2, 3)));

static void bad_object(unsigned long offset, const char *format, ...)
{
        va_list params;
        char buf[1024];

        va_start(params, format);
        vsnprintf(buf, sizeof(buf), format, params);
        va_end(params);
        die("packfile '%s': bad object at offset %lu: %s",
            pack_name, offset, buf);
}

static void *unpack_entry_data(unsigned long offset, 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 = input_len;
        inflateInit(&stream);

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

static void *unpack_raw_entry(struct object_entry *obj, union delta_base *delta_base)
{
        unsigned char *p, c;
        unsigned long size, base_offset;
        unsigned shift;

        obj->offset = consumed_bytes;

        p = fill(1);
        c = *p;
        use(1);
        obj->type = (c >> 4) & 7;
        size = (c & 15);
        shift = 4;
        while (c & 0x80) {
                p = fill(1);
                c = *p;
                use(1);
                size += (c & 0x7fUL) << shift;
                shift += 7;
        }
        obj->size = size;

        switch (obj->type) {
        case OBJ_REF_DELTA:
                hashcpy(delta_base->sha1, fill(20));
                use(20);
                break;
        case OBJ_OFS_DELTA:
                memset(delta_base, 0, sizeof(*delta_base));
                p = fill(1);
                c = *p;
                use(1);
                base_offset = c & 127;
                while (c & 128) {
                        base_offset += 1;
                        if (!base_offset || base_offset & ~(~0UL >> 7))
                                bad_object(obj->offset, "offset value overflow for delta base object");
                        p = fill(1);
                        c = *p;
                        use(1);
                        base_offset = (base_offset << 7) + (c & 127);
                }
                delta_base->offset = obj->offset - base_offset;
                if (delta_base->offset >= obj->offset)
                        bad_object(obj->offset, "delta base offset is out of bound");
                break;
        case OBJ_COMMIT:
        case OBJ_TREE:
        case OBJ_BLOB:
        case OBJ_TAG:
                break;
        default:
                bad_object(obj->offset, "bad object type %d", obj->type);
        }
        obj->hdr_size = consumed_bytes - obj->offset;

        return unpack_entry_data(obj->offset, obj->size);
}

static void * get_data_from_pack(struct object_entry *obj)
{
        unsigned long from = obj[0].offset + obj[0].hdr_size;
        unsigned long len = obj[1].offset - from;
        unsigned pg_offset = from % getpagesize();
        unsigned char *map, *data;
        z_stream stream;
        int st;

        map = mmap(NULL, len + pg_offset, PROT_READ, MAP_PRIVATE,
                   input_fd, from - pg_offset);
        if (map == MAP_FAILED)
                die("cannot mmap packfile '%s': %s", pack_name, strerror(errno));
        data = xmalloc(obj->size);
        memset(&stream, 0, sizeof(stream));
        stream.next_out = data;
        stream.avail_out = obj->size;
        stream.next_in = map + pg_offset;
        stream.avail_in = len;
        inflateInit(&stream);
        while ((st = inflate(&stream, Z_FINISH)) == Z_OK);
        inflateEnd(&stream);
        if (st != Z_STREAM_END || stream.total_out != obj->size)
                die("serious inflate inconsistency");
        munmap(map, len + pg_offset);
        return data;
}

static int find_delta(const union delta_base *base)
{
        int first = 0, last = nr_deltas;

        while (first < last) {
                int next = (first + last) / 2;
                struct delta_entry *delta = &deltas[next];
                int cmp;

                cmp = memcmp(base, &delta->base, UNION_BASE_SZ);
                if (!cmp)
                        return next;
                if (cmp < 0) {
                        last = next;
                        continue;
                }
                first = next+1;
        }
        return -first-1;
}

static int find_delta_childs(const union delta_base *base,
                             int *first_index, int *last_index)
{
        int first = find_delta(base);
        int last = first;
        int end = nr_deltas - 1;

        if (first < 0)
                return -1;
        while (first > 0 && !memcmp(&deltas[first - 1].base, base, UNION_BASE_SZ))
                --first;
        while (last < end && !memcmp(&deltas[last + 1].base, base, UNION_BASE_SZ))
                ++last;
        *first_index = first;
        *last_index = last;
        return 0;
}

static void sha1_object(const void *data, unsigned long size,
                        enum object_type type, unsigned char *sha1)
{
        SHA_CTX ctx;
        char header[50];
        int header_size;
        const char *type_str;

        switch (type) {
        case OBJ_COMMIT: type_str = commit_type; break;
        case OBJ_TREE:   type_str = tree_type; break;
        case OBJ_BLOB:   type_str = blob_type; break;
        case OBJ_TAG:    type_str = tag_type; break;
        default:
                die("bad type %d", type);
        }

        header_size = sprintf(header, "%s %lu", type_str, size) + 1;

        SHA1_Init(&ctx);
        SHA1_Update(&ctx, header, header_size);
        SHA1_Update(&ctx, data, size);
        SHA1_Final(sha1, &ctx);
}

static void resolve_delta(struct delta_entry *delta, void *base_data,
                          unsigned long base_size, enum object_type type)
{
        struct object_entry *obj = delta->obj;
        void *delta_data;
        unsigned long delta_size;
        void *result;
        unsigned long result_size;
        union delta_base delta_base;
        int j, first, last;

        obj->real_type = type;
        delta_data = get_data_from_pack(obj);
        delta_size = obj->size;
        result = patch_delta(base_data, base_size, delta_data, delta_size,
                             &result_size);
        free(delta_data);
        if (!result)
                bad_object(obj->offset, "failed to apply delta");
        sha1_object(result, result_size, type, obj->sha1);

        hashcpy(delta_base.sha1, obj->sha1);
        if (!find_delta_childs(&delta_base, &first, &last)) {
                for (j = first; j <= last; j++)
                        if (deltas[j].obj->type == OBJ_REF_DELTA)
                                resolve_delta(&deltas[j], result, result_size, type);
        }

        memset(&delta_base, 0, sizeof(delta_base));
        delta_base.offset = obj->offset;
        if (!find_delta_childs(&delta_base, &first, &last)) {
                for (j = first; j <= last; j++)
                        if (deltas[j].obj->type == OBJ_OFS_DELTA)
                                resolve_delta(&deltas[j], result, result_size, type);
        }

        free(result);
}

static int compare_delta_entry(const void *a, const void *b)
{
        const struct delta_entry *delta_a = a;
        const struct delta_entry *delta_b = b;
        return memcmp(&delta_a->base, &delta_b->base, UNION_BASE_SZ);
}

/* Parse all objects and return the pack content SHA1 hash */
static void parse_pack_objects(unsigned char *sha1)
{
        int i;
        struct delta_entry *delta = deltas;
        void *data;
        struct stat st;

        /*
         * First pass:
         * - find locations of all objects;
         * - calculate SHA1 of all non-delta objects;
         * - remember base SHA1 for all deltas.
         */
        for (i = 0; i < nr_objects; i++) {
                struct object_entry *obj = &objects[i];
                data = unpack_raw_entry(obj, &delta->base);
                obj->real_type = obj->type;
                if (obj->type == OBJ_REF_DELTA || obj->type == OBJ_OFS_DELTA) {
                        nr_deltas++;
                        delta->obj = obj;
                        delta++;
                } else
                        sha1_object(data, obj->size, obj->type, obj->sha1);
                free(data);
        }
        objects[i].offset = consumed_bytes;

        /* Check pack integrity */
        SHA1_Update(&input_ctx, input_buffer, input_offset);
        SHA1_Final(sha1, &input_ctx);
        if (hashcmp(fill(20), sha1))
                die("packfile '%s' SHA1 mismatch", pack_name);
        use(20);

        /* If input_fd is a file, we should have reached its end now. */
        if (fstat(input_fd, &st))
                die("cannot fstat packfile '%s': %s", pack_name, strerror(errno));
        if (S_ISREG(st.st_mode) && st.st_size != consumed_bytes)
                die("packfile '%s' has junk at the end", pack_name);

        /* Sort deltas by base SHA1/offset for fast searching */
        qsort(deltas, nr_deltas, sizeof(struct delta_entry),
              compare_delta_entry);

        /*
         * Second pass:
         * - for all non-delta objects, look if it is used as a base for
         *   deltas;
         * - if used as a base, uncompress the object and apply all deltas,
         *   recursively checking if the resulting object is used as a base
         *   for some more deltas.
         */
        for (i = 0; i < nr_objects; i++) {
                struct object_entry *obj = &objects[i];
                union delta_base base;
                int j, ref, ref_first, ref_last, ofs, ofs_first, ofs_last;

                if (obj->type == OBJ_REF_DELTA || obj->type == OBJ_OFS_DELTA)
                        continue;
                hashcpy(base.sha1, obj->sha1);
                ref = !find_delta_childs(&base, &ref_first, &ref_last);
                memset(&base, 0, sizeof(base));
                base.offset = obj->offset;
                ofs = !find_delta_childs(&base, &ofs_first, &ofs_last);
                if (!ref && !ofs)
                        continue;
                data = get_data_from_pack(obj);
                if (ref)
                        for (j = ref_first; j <= ref_last; j++)
                                if (deltas[j].obj->type == OBJ_REF_DELTA)
                                        resolve_delta(&deltas[j], data,
                                                      obj->size, obj->type);
                if (ofs)
                        for (j = ofs_first; j <= ofs_last; j++)
                                if (deltas[j].obj->type == OBJ_OFS_DELTA)
                                        resolve_delta(&deltas[j], data,
                                                      obj->size, obj->type);
                free(data);
        }

        /* Check for unresolved deltas */
        for (i = 0; i < nr_deltas; i++) {
                if (deltas[i].obj->real_type == OBJ_REF_DELTA ||
                    deltas[i].obj->real_type == OBJ_OFS_DELTA)
                        die("packfile '%s' has unresolved deltas",  pack_name);
        }
}

static int sha1_compare(const void *_a, const void *_b)
{
        struct object_entry *a = *(struct object_entry **)_a;
        struct object_entry *b = *(struct object_entry **)_b;
        return hashcmp(a->sha1, b->sha1);
}

/*
 * On entry *sha1 contains the pack content SHA1 hash, on exit it is
 * the SHA1 hash of sorted object names.
 */
static void write_index_file(const char *index_name, unsigned char *sha1)
{
        struct sha1file *f;
        struct object_entry **sorted_by_sha, **list, **last;
        unsigned int array[256];
        int i;
        SHA_CTX ctx;

        if (nr_objects) {
                sorted_by_sha =
                        xcalloc(nr_objects, sizeof(struct object_entry *));
                list = sorted_by_sha;
                last = sorted_by_sha + nr_objects;
                for (i = 0; i < nr_objects; ++i)
                        sorted_by_sha[i] = &objects[i];
                qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
                      sha1_compare);

        }
        else
                sorted_by_sha = list = last = NULL;

        unlink(index_name);
        f = sha1create("%s", index_name);

        /*
         * Write the first-level table (the list is sorted,
         * but we use a 256-entry lookup to be able to avoid
         * having to do eight extra binary search iterations).
         */
        for (i = 0; i < 256; i++) {
                struct object_entry **next = list;
                while (next < last) {
                        struct object_entry *obj = *next;
                        if (obj->sha1[0] != i)
                                break;
                        next++;
                }
                array[i] = htonl(next - sorted_by_sha);
                list = next;
        }
        sha1write(f, array, 256 * sizeof(int));

        /* recompute the SHA1 hash of sorted object names.
         * currently pack-objects does not do this, but that
         * can be fixed.
         */
        SHA1_Init(&ctx);
        /*
         * Write the actual SHA1 entries..
         */
        list = sorted_by_sha;
        for (i = 0; i < nr_objects; i++) {
                struct object_entry *obj = *list++;
                unsigned int offset = htonl(obj->offset);
                sha1write(f, &offset, 4);
                sha1write(f, obj->sha1, 20);
                SHA1_Update(&ctx, obj->sha1, 20);
        }
        sha1write(f, sha1, 20);
        sha1close(f, NULL, 1);
        free(sorted_by_sha);
        SHA1_Final(sha1, &ctx);
}

int main(int argc, char **argv)
{
        int i;
        char *index_name = NULL;
        char *index_name_buf = NULL;
        unsigned char sha1[20];

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

                if (*arg == '-') {
                        if (!strcmp(arg, "-o")) {
                                if (index_name || (i+1) >= argc)
                                        usage(index_pack_usage);
                                index_name = argv[++i];
                        } else
                                usage(index_pack_usage);
                        continue;
                }

                if (pack_name)
                        usage(index_pack_usage);
                pack_name = arg;
        }

        if (!pack_name)
                usage(index_pack_usage);
        if (!index_name) {
                int len = strlen(pack_name);
                if (!has_extension(pack_name, ".pack"))
                        die("packfile name '%s' does not end with '.pack'",
                            pack_name);
                index_name_buf = xmalloc(len);
                memcpy(index_name_buf, pack_name, len - 5);
                strcpy(index_name_buf + len - 5, ".idx");
                index_name = index_name_buf;
        }

        open_pack_file();
        parse_pack_header();
        objects = xcalloc(nr_objects + 1, sizeof(struct object_entry));
        deltas = xcalloc(nr_objects, sizeof(struct delta_entry));
        parse_pack_objects(sha1);
        free(deltas);
        write_index_file(index_name, sha1);
        free(objects);
        free(index_name_buf);

        printf("%s\n", sha1_to_hex(sha1));

        return 0;
}