#include "cache.h"
#include "pack.h"
#include "pack-revindex.h"

struct idx_entry
{
        const unsigned char *sha1;
        off_t                offset;
};

static int compare_entries(const void *e1, const void *e2)
{
        const struct idx_entry *entry1 = e1;
        const struct idx_entry *entry2 = e2;
        if (entry1->offset < entry2->offset)
                return -1;
        if (entry1->offset > entry2->offset)
                return 1;
        return 0;
}

static int verify_packfile(struct packed_git *p,
                struct pack_window **w_curs)
{
        off_t index_size = p->index_size;
        const unsigned char *index_base = p->index_data;
        SHA_CTX ctx;
        unsigned char sha1[20], *pack_sig;
        off_t offset = 0, pack_sig_ofs = p->pack_size - 20;
        uint32_t nr_objects, i;
        int err = 0;
        struct idx_entry *entries;

        /* Note that the pack header checks are actually performed by
         * use_pack when it first opens the pack file.  If anything
         * goes wrong during those checks then the call will die out
         * immediately.
         */

        SHA1_Init(&ctx);
        while (offset < pack_sig_ofs) {
                unsigned int remaining;
                unsigned char *in = use_pack(p, w_curs, offset, &remaining);
                offset += remaining;
                if (offset > pack_sig_ofs)
                        remaining -= (unsigned int)(offset - pack_sig_ofs);
                SHA1_Update(&ctx, in, remaining);
        }
        SHA1_Final(sha1, &ctx);
        pack_sig = use_pack(p, w_curs, pack_sig_ofs, NULL);
        if (hashcmp(sha1, pack_sig))
                err = error("%s SHA1 checksum mismatch",
                            p->pack_name);
        if (hashcmp(index_base + index_size - 40, pack_sig))
                err = error("%s SHA1 does not match its inddex",
                            p->pack_name);
        unuse_pack(w_curs);

        /* Make sure everything reachable from idx is valid.  Since we
         * have verified that nr_objects matches between idx and pack,
         * we do not do scan-streaming check on the pack file.
         */
        nr_objects = p->num_objects;
        entries = xmalloc(nr_objects * sizeof(*entries));
        /* first sort entries by pack offset, since unpacking them is more efficient that way */
        for (i = 0; i < nr_objects; i++) {
                entries[i].sha1 = nth_packed_object_sha1(p, i);
                if (!entries[i].sha1)
                        die("internal error pack-check nth-packed-object");
                entries[i].offset = find_pack_entry_one(entries[i].sha1, p);
                if (!entries[i].offset)
                        die("internal error pack-check find-pack-entry-one");
        }
        qsort(entries, nr_objects, sizeof(*entries), compare_entries);

        for (i = 0; i < nr_objects; i++) {
                void *data;
                enum object_type type;
                unsigned long size;

                data = unpack_entry(p, entries[i].offset, &type, &size);
                if (!data) {
                        err = error("cannot unpack %s from %s at offset %"PRIuMAX"",
                                    sha1_to_hex(entries[i].sha1), p->pack_name,
                                    (uintmax_t)entries[i].offset);
                        break;
                }
                if (check_sha1_signature(entries[i].sha1, data, size, typename(type))) {
                        err = error("packed %s from %s is corrupt",
                                    sha1_to_hex(entries[i].sha1), p->pack_name);
                        free(data);
                        break;
                }
                free(data);
        }
        free(entries);

        return err;
}


#define MAX_CHAIN 50

static void show_pack_info(struct packed_git *p)
{
        uint32_t nr_objects, i, chain_histogram[MAX_CHAIN+1];

        nr_objects = p->num_objects;
        memset(chain_histogram, 0, sizeof(chain_histogram));

        for (i = 0; i < nr_objects; i++) {
                const unsigned char *sha1;
                unsigned char base_sha1[20];
                const char *type;
                unsigned long size;
                unsigned long store_size;
                off_t offset;
                unsigned int delta_chain_length;

                sha1 = nth_packed_object_sha1(p, i);
                if (!sha1)
                        die("internal error pack-check nth-packed-object");
                offset = find_pack_entry_one(sha1, p);
                if (!offset)
                        die("internal error pack-check find-pack-entry-one");

                type = packed_object_info_detail(p, offset, &size, &store_size,
                                                 &delta_chain_length,
                                                 base_sha1);
                printf("%s ", sha1_to_hex(sha1));
                if (!delta_chain_length)
                        printf("%-6s %lu %lu %"PRIuMAX"\n",
                               type, size, store_size, (uintmax_t)offset);
                else {
                        printf("%-6s %lu %lu %"PRIuMAX" %u %s\n",
                               type, size, store_size, (uintmax_t)offset,
                               delta_chain_length, sha1_to_hex(base_sha1));
                        if (delta_chain_length <= MAX_CHAIN)
                                chain_histogram[delta_chain_length]++;
                        else
                                chain_histogram[0]++;
                }
        }

        for (i = 0; i <= MAX_CHAIN; i++) {
                if (!chain_histogram[i])
                        continue;
                printf("chain length = %d: %d object%s\n", i,
                       chain_histogram[i], chain_histogram[i] > 1 ? "s" : "");
        }
        if (chain_histogram[0])
                printf("chain length > %d: %d object%s\n", MAX_CHAIN,
                       chain_histogram[0], chain_histogram[0] > 1 ? "s" : "");
}

int verify_pack(struct packed_git *p, int verbose)
{
        off_t index_size;
        const unsigned char *index_base;
        SHA_CTX ctx;
        unsigned char sha1[20];
        int err = 0;
        struct pack_window *w_curs = NULL;

        if (open_pack_index(p))
                return error("packfile %s index not opened", p->pack_name);
        index_size = p->index_size;
        index_base = p->index_data;

        /* Verify SHA1 sum of the index file */
        SHA1_Init(&ctx);
        SHA1_Update(&ctx, index_base, (unsigned int)(index_size - 20));
        SHA1_Final(sha1, &ctx);
        if (hashcmp(sha1, index_base + index_size - 20))
                err = error("Packfile index for %s SHA1 mismatch",
                            p->pack_name);

        /* Verify pack file */
        err |= verify_packfile(p, &w_curs);
        unuse_pack(&w_curs);

        if (verbose) {
                if (err)
                        printf("%s: bad\n", p->pack_name);
                else {
                        show_pack_info(p);
                        printf("%s: ok\n", p->pack_name);
                }
        }

        return err;
}