#include "cache.h"
#include "object-store.h"
#include "commit.h"
#include "tag.h"
#include "diff.h"
#include "revision.h"
#include "list-objects.h"
#include "progress.h"
#include "pack-revindex.h"
#include "pack.h"
#include "pack-bitmap.h"
#include "sha1-lookup.h"
#include "pack-objects.h"
#include "commit-reach.h"

struct bitmapped_commit {
        struct commit *commit;
        struct ewah_bitmap *bitmap;
        struct ewah_bitmap *write_as;
        int flags;
        int xor_offset;
        uint32_t commit_pos;
};

struct bitmap_writer {
        struct ewah_bitmap *commits;
        struct ewah_bitmap *trees;
        struct ewah_bitmap *blobs;
        struct ewah_bitmap *tags;

        khash_sha1 *bitmaps;
        khash_sha1 *reused;
        struct packing_data *to_pack;

        struct bitmapped_commit *selected;
        unsigned int selected_nr, selected_alloc;

        struct progress *progress;
        int show_progress;
        unsigned char pack_checksum[GIT_MAX_RAWSZ];
};

static struct bitmap_writer writer;

void bitmap_writer_show_progress(int show)
{
        writer.show_progress = show;
}

/**
 * Build the initial type index for the packfile
 */
void bitmap_writer_build_type_index(struct packing_data *to_pack,
                                    struct pack_idx_entry **index,
                                    uint32_t index_nr)
{
        uint32_t i;

        writer.commits = ewah_new();
        writer.trees = ewah_new();
        writer.blobs = ewah_new();
        writer.tags = ewah_new();
        ALLOC_ARRAY(to_pack->in_pack_pos, to_pack->nr_objects);

        for (i = 0; i < index_nr; ++i) {
                struct object_entry *entry = (struct object_entry *)index[i];
                enum object_type real_type;

                oe_set_in_pack_pos(to_pack, entry, i);

                switch (oe_type(entry)) {
                case OBJ_COMMIT:
                case OBJ_TREE:
                case OBJ_BLOB:
                case OBJ_TAG:
                        real_type = oe_type(entry);
                        break;

                default:
                        real_type = oid_object_info(to_pack->repo,
                                                    &entry->idx.oid, NULL);
                        break;
                }

                switch (real_type) {
                case OBJ_COMMIT:
                        ewah_set(writer.commits, i);
                        break;

                case OBJ_TREE:
                        ewah_set(writer.trees, i);
                        break;

                case OBJ_BLOB:
                        ewah_set(writer.blobs, i);
                        break;

                case OBJ_TAG:
                        ewah_set(writer.tags, i);
                        break;

                default:
                        die("Missing type information for %s (%d/%d)",
                            oid_to_hex(&entry->idx.oid), real_type,
                            oe_type(entry));
                }
        }
}

/**
 * Compute the actual bitmaps
 */
static struct object **seen_objects;
static unsigned int seen_objects_nr, seen_objects_alloc;

static inline void push_bitmapped_commit(struct commit *commit, struct ewah_bitmap *reused)
{
        if (writer.selected_nr >= writer.selected_alloc) {
                writer.selected_alloc = (writer.selected_alloc + 32) * 2;
                REALLOC_ARRAY(writer.selected, writer.selected_alloc);
        }

        writer.selected[writer.selected_nr].commit = commit;
        writer.selected[writer.selected_nr].bitmap = reused;
        writer.selected[writer.selected_nr].flags = 0;

        writer.selected_nr++;
}

static inline void mark_as_seen(struct object *object)
{
        ALLOC_GROW(seen_objects, seen_objects_nr + 1, seen_objects_alloc);
        seen_objects[seen_objects_nr++] = object;
}

static inline void reset_all_seen(void)
{
        unsigned int i;
        for (i = 0; i < seen_objects_nr; ++i) {
                seen_objects[i]->flags &= ~(SEEN | ADDED | SHOWN);
        }
        seen_objects_nr = 0;
}

static uint32_t find_object_pos(const struct object_id *oid)
{
        struct object_entry *entry = packlist_find(writer.to_pack, oid, NULL);

        if (!entry) {
                die("Failed to write bitmap index. Packfile doesn't have full closure "
                        "(object %s is missing)", oid_to_hex(oid));
        }

        return oe_in_pack_pos(writer.to_pack, entry);
}

static void show_object(struct object *object, const char *name, void *data)
{
        struct bitmap *base = data;
        bitmap_set(base, find_object_pos(&object->oid));
        mark_as_seen(object);
}

static void show_commit(struct commit *commit, void *data)
{
        mark_as_seen((struct object *)commit);
}

static int
add_to_include_set(struct bitmap *base, struct commit *commit)
{
        khiter_t hash_pos;
        uint32_t bitmap_pos = find_object_pos(&commit->object.oid);

        if (bitmap_get(base, bitmap_pos))
                return 0;

        hash_pos = kh_get_sha1(writer.bitmaps, commit->object.oid.hash);
        if (hash_pos < kh_end(writer.bitmaps)) {
                struct bitmapped_commit *bc = kh_value(writer.bitmaps, hash_pos);
                bitmap_or_ewah(base, bc->bitmap);
                return 0;
        }

        bitmap_set(base, bitmap_pos);
        return 1;
}

static int
should_include(struct commit *commit, void *_data)
{
        struct bitmap *base = _data;

        if (!add_to_include_set(base, commit)) {
                struct commit_list *parent = commit->parents;

                mark_as_seen((struct object *)commit);

                while (parent) {
                        parent->item->object.flags |= SEEN;
                        mark_as_seen((struct object *)parent->item);
                        parent = parent->next;
                }

                return 0;
        }

        return 1;
}

static void compute_xor_offsets(void)
{
        static const int MAX_XOR_OFFSET_SEARCH = 10;

        int i, next = 0;

        while (next < writer.selected_nr) {
                struct bitmapped_commit *stored = &writer.selected[next];

                int best_offset = 0;
                struct ewah_bitmap *best_bitmap = stored->bitmap;
                struct ewah_bitmap *test_xor;

                for (i = 1; i <= MAX_XOR_OFFSET_SEARCH; ++i) {
                        int curr = next - i;

                        if (curr < 0)
                                break;

                        test_xor = ewah_pool_new();
                        ewah_xor(writer.selected[curr].bitmap, stored->bitmap, test_xor);

                        if (test_xor->buffer_size < best_bitmap->buffer_size) {
                                if (best_bitmap != stored->bitmap)
                                        ewah_pool_free(best_bitmap);

                                best_bitmap = test_xor;
                                best_offset = i;
                        } else {
                                ewah_pool_free(test_xor);
                        }
                }

                stored->xor_offset = best_offset;
                stored->write_as = best_bitmap;

                next++;
        }
}

void bitmap_writer_build(struct packing_data *to_pack)
{
        static const double REUSE_BITMAP_THRESHOLD = 0.2;

        int i, reuse_after, need_reset;
        struct bitmap *base = bitmap_new();
        struct rev_info revs;

        writer.bitmaps = kh_init_sha1();
        writer.to_pack = to_pack;

        if (writer.show_progress)
                writer.progress = start_progress("Building bitmaps", writer.selected_nr);

        repo_init_revisions(to_pack->repo, &revs, NULL);
        revs.tag_objects = 1;
        revs.tree_objects = 1;
        revs.blob_objects = 1;
        revs.no_walk = 0;

        revs.include_check = should_include;
        reset_revision_walk();

        reuse_after = writer.selected_nr * REUSE_BITMAP_THRESHOLD;
        need_reset = 0;

        for (i = writer.selected_nr - 1; i >= 0; --i) {
                struct bitmapped_commit *stored;
                struct object *object;

                khiter_t hash_pos;
                int hash_ret;

                stored = &writer.selected[i];
                object = (struct object *)stored->commit;

                if (stored->bitmap == NULL) {
                        if (i < writer.selected_nr - 1 &&
                            (need_reset ||
                             !in_merge_bases(writer.selected[i + 1].commit,
                                             stored->commit))) {
                            bitmap_reset(base);
                            reset_all_seen();
                        }

                        add_pending_object(&revs, object, "");
                        revs.include_check_data = base;

                        if (prepare_revision_walk(&revs))
                                die("revision walk setup failed");

                        traverse_commit_list(&revs, show_commit, show_object, base);

                        object_array_clear(&revs.pending);

                        stored->bitmap = bitmap_to_ewah(base);
                        need_reset = 0;
                } else
                        need_reset = 1;

                if (i >= reuse_after)
                        stored->flags |= BITMAP_FLAG_REUSE;

                hash_pos = kh_put_sha1(writer.bitmaps, object->oid.hash, &hash_ret);
                if (hash_ret == 0)
                        die("Duplicate entry when writing index: %s",
                            oid_to_hex(&object->oid));

                kh_value(writer.bitmaps, hash_pos) = stored;
                display_progress(writer.progress, writer.selected_nr - i);
        }

        bitmap_free(base);
        stop_progress(&writer.progress);

        compute_xor_offsets();
}

/**
 * Select the commits that will be bitmapped
 */
static inline unsigned int next_commit_index(unsigned int idx)
{
        static const unsigned int MIN_COMMITS = 100;
        static const unsigned int MAX_COMMITS = 5000;

        static const unsigned int MUST_REGION = 100;
        static const unsigned int MIN_REGION = 20000;

        unsigned int offset, next;

        if (idx <= MUST_REGION)
                return 0;

        if (idx <= MIN_REGION) {
                offset = idx - MUST_REGION;
                return (offset < MIN_COMMITS) ? offset : MIN_COMMITS;
        }

        offset = idx - MIN_REGION;
        next = (offset < MAX_COMMITS) ? offset : MAX_COMMITS;

        return (next > MIN_COMMITS) ? next : MIN_COMMITS;
}

static int date_compare(const void *_a, const void *_b)
{
        struct commit *a = *(struct commit **)_a;
        struct commit *b = *(struct commit **)_b;
        return (long)b->date - (long)a->date;
}

void bitmap_writer_reuse_bitmaps(struct packing_data *to_pack)
{
        struct bitmap_index *bitmap_git;
        if (!(bitmap_git = prepare_bitmap_git(to_pack->repo)))
                return;

        writer.reused = kh_init_sha1();
        rebuild_existing_bitmaps(bitmap_git, to_pack, writer.reused,
                                 writer.show_progress);
        /*
         * NEEDSWORK: rebuild_existing_bitmaps() makes writer.reused reference
         * some bitmaps in bitmap_git, so we can't free the latter.
         */
}

static struct ewah_bitmap *find_reused_bitmap(const struct object_id *oid)
{
        khiter_t hash_pos;

        if (!writer.reused)
                return NULL;

        hash_pos = kh_get_sha1(writer.reused, oid->hash);
        if (hash_pos >= kh_end(writer.reused))
                return NULL;

        return kh_value(writer.reused, hash_pos);
}

void bitmap_writer_select_commits(struct commit **indexed_commits,
                                  unsigned int indexed_commits_nr,
                                  int max_bitmaps)
{
        unsigned int i = 0, j, next;

        QSORT(indexed_commits, indexed_commits_nr, date_compare);

        if (writer.show_progress)
                writer.progress = start_progress("Selecting bitmap commits", 0);

        if (indexed_commits_nr < 100) {
                for (i = 0; i < indexed_commits_nr; ++i)
                        push_bitmapped_commit(indexed_commits[i], NULL);
                return;
        }

        for (;;) {
                struct ewah_bitmap *reused_bitmap = NULL;
                struct commit *chosen = NULL;

                next = next_commit_index(i);

                if (i + next >= indexed_commits_nr)
                        break;

                if (max_bitmaps > 0 && writer.selected_nr >= max_bitmaps) {
                        writer.selected_nr = max_bitmaps;
                        break;
                }

                if (next == 0) {
                        chosen = indexed_commits[i];
                        reused_bitmap = find_reused_bitmap(&chosen->object.oid);
                } else {
                        chosen = indexed_commits[i + next];

                        for (j = 0; j <= next; ++j) {
                                struct commit *cm = indexed_commits[i + j];

                                reused_bitmap = find_reused_bitmap(&cm->object.oid);
                                if (reused_bitmap || (cm->object.flags & NEEDS_BITMAP) != 0) {
                                        chosen = cm;
                                        break;
                                }

                                if (cm->parents && cm->parents->next)
                                        chosen = cm;
                        }
                }

                push_bitmapped_commit(chosen, reused_bitmap);

                i += next + 1;
                display_progress(writer.progress, i);
        }

        stop_progress(&writer.progress);
}


static int hashwrite_ewah_helper(void *f, const void *buf, size_t len)
{
        /* hashwrite will die on error */
        hashwrite(f, buf, len);
        return len;
}

/**
 * Write the bitmap index to disk
 */
static inline void dump_bitmap(struct hashfile *f, struct ewah_bitmap *bitmap)
{
        if (ewah_serialize_to(bitmap, hashwrite_ewah_helper, f) < 0)
                die("Failed to write bitmap index");
}

static const unsigned char *sha1_access(size_t pos, void *table)
{
        struct pack_idx_entry **index = table;
        return index[pos]->oid.hash;
}

static void write_selected_commits_v1(struct hashfile *f,
                                      struct pack_idx_entry **index,
                                      uint32_t index_nr)
{
        int i;

        for (i = 0; i < writer.selected_nr; ++i) {
                struct bitmapped_commit *stored = &writer.selected[i];

                int commit_pos =
                        sha1_pos(stored->commit->object.oid.hash, index, index_nr, sha1_access);

                if (commit_pos < 0)
                        BUG("trying to write commit not in index");

                hashwrite_be32(f, commit_pos);
                hashwrite_u8(f, stored->xor_offset);
                hashwrite_u8(f, stored->flags);

                dump_bitmap(f, stored->write_as);
        }
}

static void write_hash_cache(struct hashfile *f,
                             struct pack_idx_entry **index,
                             uint32_t index_nr)
{
        uint32_t i;

        for (i = 0; i < index_nr; ++i) {
                struct object_entry *entry = (struct object_entry *)index[i];
                uint32_t hash_value = htonl(entry->hash);
                hashwrite(f, &hash_value, sizeof(hash_value));
        }
}

void bitmap_writer_set_checksum(unsigned char *sha1)
{
        hashcpy(writer.pack_checksum, sha1);
}

void bitmap_writer_finish(struct pack_idx_entry **index,
                          uint32_t index_nr,
                          const char *filename,
                          uint16_t options)
{
        static uint16_t default_version = 1;
        static uint16_t flags = BITMAP_OPT_FULL_DAG;
        struct strbuf tmp_file = STRBUF_INIT;
        struct hashfile *f;

        struct bitmap_disk_header header;

        int fd = odb_mkstemp(&tmp_file, "pack/tmp_bitmap_XXXXXX");

        f = hashfd(fd, tmp_file.buf);

        memcpy(header.magic, BITMAP_IDX_SIGNATURE, sizeof(BITMAP_IDX_SIGNATURE));
        header.version = htons(default_version);
        header.options = htons(flags | options);
        header.entry_count = htonl(writer.selected_nr);
        hashcpy(header.checksum, writer.pack_checksum);

        hashwrite(f, &header, sizeof(header) - GIT_MAX_RAWSZ + the_hash_algo->rawsz);
        dump_bitmap(f, writer.commits);
        dump_bitmap(f, writer.trees);
        dump_bitmap(f, writer.blobs);
        dump_bitmap(f, writer.tags);
        write_selected_commits_v1(f, index, index_nr);

        if (options & BITMAP_OPT_HASH_CACHE)
                write_hash_cache(f, index, index_nr);

        finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC | CSUM_CLOSE);

        if (adjust_shared_perm(tmp_file.buf))
                die_errno("unable to make temporary bitmap file readable");

        if (rename(tmp_file.buf, filename))
                die_errno("unable to rename temporary bitmap file to '%s'", filename);

        strbuf_release(&tmp_file);
}