/*
 * Copyright (c) 2011, Google Inc.
 */
#include "cache.h"
#include "bulk-checkin.h"
#include "csum-file.h"
#include "pack.h"
#include "strbuf.h"

static int pack_compression_level = Z_DEFAULT_COMPRESSION;

static struct bulk_checkin_state {
        unsigned plugged:1;

        char *pack_tmp_name;
        struct sha1file *f;
        off_t offset;
        struct pack_idx_option pack_idx_opts;

        struct pack_idx_entry **written;
        uint32_t alloc_written;
        uint32_t nr_written;
} state;

static void finish_bulk_checkin(struct bulk_checkin_state *state)
{
        unsigned char sha1[20];
        struct strbuf packname = STRBUF_INIT;
        int i;

        if (!state->f)
                return;

        if (state->nr_written == 0) {
                close(state->f->fd);
                unlink(state->pack_tmp_name);
                goto clear_exit;
        } else if (state->nr_written == 1) {
                sha1close(state->f, sha1, CSUM_FSYNC);
        } else {
                int fd = sha1close(state->f, sha1, 0);
                fixup_pack_header_footer(fd, sha1, state->pack_tmp_name,
                                         state->nr_written, sha1,
                                         state->offset);
                close(fd);
        }

        strbuf_addf(&packname, "%s/pack/pack-", get_object_directory());
        finish_tmp_packfile(&packname, state->pack_tmp_name,
                            state->written, state->nr_written,
                            &state->pack_idx_opts, sha1);
        for (i = 0; i < state->nr_written; i++)
                free(state->written[i]);

clear_exit:
        free(state->written);
        memset(state, 0, sizeof(*state));

        strbuf_release(&packname);
        /* Make objects we just wrote available to ourselves */
        reprepare_packed_git();
}

static int already_written(struct bulk_checkin_state *state, unsigned char sha1[])
{
        int i;

        /* The object may already exist in the repository */
        if (has_sha1_file(sha1))
                return 1;

        /* Might want to keep the list sorted */
        for (i = 0; i < state->nr_written; i++)
                if (!hashcmp(state->written[i]->sha1, sha1))
                        return 1;

        /* This is a new object we need to keep */
        return 0;
}

/*
 * Read the contents from fd for size bytes, streaming it to the
 * packfile in state while updating the hash in ctx. Signal a failure
 * by returning a negative value when the resulting pack would exceed
 * the pack size limit and this is not the first object in the pack,
 * so that the caller can discard what we wrote from the current pack
 * by truncating it and opening a new one. The caller will then call
 * us again after rewinding the input fd.
 *
 * The already_hashed_to pointer is kept untouched by the caller to
 * make sure we do not hash the same byte when we are called
 * again. This way, the caller does not have to checkpoint its hash
 * status before calling us just in case we ask it to call us again
 * with a new pack.
 */
static int stream_to_pack(struct bulk_checkin_state *state,
                          git_SHA_CTX *ctx, off_t *already_hashed_to,
                          int fd, size_t size, enum object_type type,
                          const char *path, unsigned flags)
{
        git_zstream s;
        unsigned char obuf[16384];
        unsigned hdrlen;
        int status = Z_OK;
        int write_object = (flags & HASH_WRITE_OBJECT);
        off_t offset = 0;

        memset(&s, 0, sizeof(s));
        git_deflate_init(&s, pack_compression_level);

        hdrlen = encode_in_pack_object_header(type, size, obuf);
        s.next_out = obuf + hdrlen;
        s.avail_out = sizeof(obuf) - hdrlen;

        while (status != Z_STREAM_END) {
                unsigned char ibuf[16384];

                if (size && !s.avail_in) {
                        ssize_t rsize = size < sizeof(ibuf) ? size : sizeof(ibuf);
                        if (read_in_full(fd, ibuf, rsize) != rsize)
                                die("failed to read %d bytes from '%s'",
                                    (int)rsize, path);
                        offset += rsize;
                        if (*already_hashed_to < offset) {
                                size_t hsize = offset - *already_hashed_to;
                                if (rsize < hsize)
                                        hsize = rsize;
                                if (hsize)
                                        git_SHA1_Update(ctx, ibuf, hsize);
                                *already_hashed_to = offset;
                        }
                        s.next_in = ibuf;
                        s.avail_in = rsize;
                        size -= rsize;
                }

                status = git_deflate(&s, size ? 0 : Z_FINISH);

                if (!s.avail_out || status == Z_STREAM_END) {
                        if (write_object) {
                                size_t written = s.next_out - obuf;

                                /* would we bust the size limit? */
                                if (state->nr_written &&
                                    pack_size_limit_cfg &&
                                    pack_size_limit_cfg < state->offset + written) {
                                        git_deflate_abort(&s);
                                        return -1;
                                }

                                sha1write(state->f, obuf, written);
                                state->offset += written;
                        }
                        s.next_out = obuf;
                        s.avail_out = sizeof(obuf);
                }

                switch (status) {
                case Z_OK:
                case Z_BUF_ERROR:
                case Z_STREAM_END:
                        continue;
                default:
                        die("unexpected deflate failure: %d", status);
                }
        }
        git_deflate_end(&s);
        return 0;
}

/* Lazily create backing packfile for the state */
static void prepare_to_stream(struct bulk_checkin_state *state,
                              unsigned flags)
{
        if (!(flags & HASH_WRITE_OBJECT) || state->f)
                return;

        state->f = create_tmp_packfile(&state->pack_tmp_name);
        reset_pack_idx_option(&state->pack_idx_opts);

        /* Pretend we are going to write only one object */
        state->offset = write_pack_header(state->f, 1);
        if (!state->offset)
                die_errno("unable to write pack header");
}

static int deflate_to_pack(struct bulk_checkin_state *state,
                           unsigned char result_sha1[],
                           int fd, size_t size,
                           enum object_type type, const char *path,
                           unsigned flags)
{
        off_t seekback, already_hashed_to;
        git_SHA_CTX ctx;
        unsigned char obuf[16384];
        unsigned header_len;
        struct sha1file_checkpoint checkpoint;
        struct pack_idx_entry *idx = NULL;

        seekback = lseek(fd, 0, SEEK_CUR);
        if (seekback == (off_t) -1)
                return error("cannot find the current offset");

        header_len = sprintf((char *)obuf, "%s %" PRIuMAX,
                             typename(type), (uintmax_t)size) + 1;
        git_SHA1_Init(&ctx);
        git_SHA1_Update(&ctx, obuf, header_len);

        /* Note: idx is non-NULL when we are writing */
        if ((flags & HASH_WRITE_OBJECT) != 0)
                idx = xcalloc(1, sizeof(*idx));

        already_hashed_to = 0;

        while (1) {
                prepare_to_stream(state, flags);
                if (idx) {
                        sha1file_checkpoint(state->f, &checkpoint);
                        idx->offset = state->offset;
                        crc32_begin(state->f);
                }
                if (!stream_to_pack(state, &ctx, &already_hashed_to,
                                    fd, size, type, path, flags))
                        break;
                /*
                 * Writing this object to the current pack will make
                 * it too big; we need to truncate it, start a new
                 * pack, and write into it.
                 */
                if (!idx)
                        die("BUG: should not happen");
                sha1file_truncate(state->f, &checkpoint);
                state->offset = checkpoint.offset;
                finish_bulk_checkin(state);
                if (lseek(fd, seekback, SEEK_SET) == (off_t) -1)
                        return error("cannot seek back");
        }
        git_SHA1_Final(result_sha1, &ctx);
        if (!idx)
                return 0;

        idx->crc32 = crc32_end(state->f);
        if (already_written(state, result_sha1)) {
                sha1file_truncate(state->f, &checkpoint);
                state->offset = checkpoint.offset;
                free(idx);
        } else {
                hashcpy(idx->sha1, result_sha1);
                ALLOC_GROW(state->written,
                           state->nr_written + 1,
                           state->alloc_written);
                state->written[state->nr_written++] = idx;
        }
        return 0;
}

int index_bulk_checkin(unsigned char *sha1,
                       int fd, size_t size, enum object_type type,
                       const char *path, unsigned flags)
{
        int status = deflate_to_pack(&state, sha1, fd, size, type,
                                     path, flags);
        if (!state.plugged)
                finish_bulk_checkin(&state);
        return status;
}

void plug_bulk_checkin(void)
{
        state.plugged = 1;
}

void unplug_bulk_checkin(void)
{
        state.plugged = 0;
        if (state.f)
                finish_bulk_checkin(&state);
}