/* Copyright (c) 2004-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "ioloop.h"
#include "array.h"
#include "mmap-util.h"
#include "mail-index-modseq.h"
#include "mail-index-view-private.h"
#include "mail-index-sync-private.h"
#include "mail-transaction-log.h"
#include "mail-transaction-log-private.h"

/* If we have less than this many bytes to sync from log file, don't bother
   reading the main index */
#define MAIL_INDEX_SYNC_MIN_READ_INDEX_SIZE 2048

static void
mail_index_sync_update_log_offset(struct mail_index_sync_map_ctx *ctx,
				  struct mail_index_map *map, bool eol)
{
	uint32_t prev_seq;
	uoff_t prev_offset;

	mail_transaction_log_view_get_prev_pos(ctx->view->log_view,
					       &prev_seq, &prev_offset);
	if (prev_seq == 0) {
		/* handling lost changes in view syncing */
		return;
	}

	if (!eol) {
		if (prev_offset == ctx->ext_intro_end_offset &&
		    prev_seq == ctx->ext_intro_seq) {
			/* previous transaction was an extension introduction.
			   we probably came here from
			   mail_index_sync_ext_reset(). if there are any more
			   views which want to continue syncing it needs the
			   intro. so back up a bit more.

			   don't do this in case the last transaction in the
			   log is the extension intro, so we don't keep trying
			   to sync it over and over again. */
			prev_offset = ctx->ext_intro_offset;
		}
		map->hdr.log_file_seq = prev_seq;
	} else {
		i_assert(ctx->view->index->log->head->hdr.file_seq == prev_seq);
		if (map->hdr.log_file_seq != prev_seq) {
			map->hdr.log_file_seq = prev_seq;
			map->hdr.log_file_tail_offset = 0;
		}
	}
	map->hdr.log_file_head_offset = prev_offset;
}

static void mail_index_sync_replace_map(struct mail_index_sync_map_ctx *ctx,
					struct mail_index_map *map)
{
        struct mail_index_view *view = ctx->view;

	i_assert(view->map != map);

	mail_index_sync_update_log_offset(ctx, view->map, FALSE);
	mail_index_unmap(&view->map);
	view->map = map;

	if (ctx->type != MAIL_INDEX_SYNC_HANDLER_VIEW)
		view->index->map = map;
}

static struct mail_index_map *
mail_index_sync_move_to_private_memory(struct mail_index_sync_map_ctx *ctx)
{
	struct mail_index_map *map = ctx->view->map;

	if (map->refcount > 1) {
		/* Multiple views point to this map. Make a copy of the map
		   (but not rec_map). */
		map = mail_index_map_clone(map);
		mail_index_sync_replace_map(ctx, map);
		i_assert(ctx->view->map == map);
	}

	if (!MAIL_INDEX_MAP_IS_IN_MEMORY(ctx->view->map)) {
		/* map points to mmap()ed area, copy it into memory. */
		mail_index_map_move_to_memory(ctx->view->map);
	}
	return map;
}

struct mail_index_map *
mail_index_sync_get_atomic_map(struct mail_index_sync_map_ctx *ctx)
{
	/* First make sure we have a private map with rec_map pointing to
	   memory. */
	(void)mail_index_sync_move_to_private_memory(ctx);
	/* Next make sure the rec_map is also private to us. */
	mail_index_record_map_move_to_private(ctx->view->map);
	return ctx->view->map;
}

static int
mail_index_header_update_counts(struct mail_index_header *hdr,
				uint8_t old_flags, uint8_t new_flags,
				const char **error_r)
{
	if (((old_flags ^ new_flags) & MAIL_SEEN) != 0) {
		/* different seen-flag */
		if ((old_flags & MAIL_SEEN) != 0) {
			if (hdr->seen_messages_count == 0) {
				*error_r = "Seen counter wrong";
				return -1;
			}
			hdr->seen_messages_count--;
		} else {
			if (hdr->seen_messages_count >= hdr->messages_count) {
				*error_r = "Seen counter wrong";
				return -1;
			}

			if (++hdr->seen_messages_count == hdr->messages_count)
				hdr->first_unseen_uid_lowwater = hdr->next_uid;
		}
	}

	if (((old_flags ^ new_flags) & MAIL_DELETED) != 0) {
		/* different deleted-flag */
		if ((old_flags & MAIL_DELETED) == 0) {
			hdr->deleted_messages_count++;
			if (hdr->deleted_messages_count > hdr->messages_count) {
				*error_r = "Deleted counter wrong";
				return -1;
			}
		} else {
			if (hdr->deleted_messages_count == 0 ||
			    hdr->deleted_messages_count > hdr->messages_count) {
				*error_r = "Deleted counter wrong";
				return -1;
			}

			if (--hdr->deleted_messages_count == 0)
				hdr->first_deleted_uid_lowwater = hdr->next_uid;
		}
	}
	return 0;
}

static void
mail_index_sync_header_update_counts_all(struct mail_index_sync_map_ctx *ctx,
					 uint32_t uid,
					 uint8_t old_flags, uint8_t new_flags)
{
	struct mail_index_map *const *maps;
	const char *error;
	unsigned int i, count;

	maps = array_get(&ctx->view->map->rec_map->maps, &count);
	for (i = 0; i < count; i++) {
		if (uid >= maps[i]->hdr.next_uid)
			continue;

		if (mail_index_header_update_counts(&maps[i]->hdr,
						    old_flags, new_flags,
						    &error) < 0)
			mail_index_sync_set_corrupted(ctx, "%s", error);
	}
}

static void
mail_index_sync_header_update_counts(struct mail_index_sync_map_ctx *ctx,
				     uint32_t uid, uint8_t old_flags,
				     uint8_t new_flags)
{
	const char *error;

	if (uid >= ctx->view->map->hdr.next_uid) {
		mail_index_sync_set_corrupted(ctx, "uid %u >= next_uid %u",
					      uid, ctx->view->map->hdr.next_uid);
	} else {
		if (mail_index_header_update_counts(&ctx->view->map->hdr,
						    old_flags, new_flags,
						    &error) < 0)
			mail_index_sync_set_corrupted(ctx, "%s", error);
	}
}

static void
mail_index_header_update_lowwaters(struct mail_index_sync_map_ctx *ctx,
				   uint32_t uid, enum mail_flags flags)
{
	struct mail_index_map *const *maps;
	unsigned int i, count;

	maps = array_get(&ctx->view->map->rec_map->maps, &count);
	for (i = 0; i < count; i++) {
		if ((flags & MAIL_SEEN) == 0 &&
		    uid < maps[i]->hdr.first_unseen_uid_lowwater)
			maps[i]->hdr.first_unseen_uid_lowwater = uid;
		if ((flags & MAIL_DELETED) != 0 &&
		    uid < maps[i]->hdr.first_deleted_uid_lowwater)
			maps[i]->hdr.first_deleted_uid_lowwater = uid;
	}
}

static void
sync_expunge_call_handlers(struct mail_index_sync_map_ctx *ctx,
			   uint32_t seq1, uint32_t seq2)
{
	const struct mail_index_expunge_handler *eh;
	struct mail_index_record *rec;
	uint32_t seq;

	array_foreach(&ctx->expunge_handlers, eh) {
		for (seq = seq1; seq <= seq2; seq++) {
			rec = MAIL_INDEX_REC_AT_SEQ(ctx->view->map, seq);
			eh->handler(ctx, PTR_OFFSET(rec, eh->record_offset),
				    eh->sync_context);
		}
	}
}

static bool
sync_expunge_handlers_init(struct mail_index_sync_map_ctx *ctx)
{
	/* call expunge handlers only when syncing index file */
	if (ctx->type != MAIL_INDEX_SYNC_HANDLER_FILE)
		return FALSE;

	if (!ctx->expunge_handlers_set)
		mail_index_sync_init_expunge_handlers(ctx);

	if (!array_is_created(&ctx->expunge_handlers))
		return FALSE;
	return TRUE;
}

static void
sync_expunge_range(struct mail_index_sync_map_ctx *ctx, const ARRAY_TYPE(seq_range) *seqs)
{
	struct mail_index_map *map;
	const struct seq_range *range;
	unsigned int i, count;
	uint32_t dest_seq1, prev_seq2, orig_rec_count;

	range = array_get(seqs, &count);
	if (count == 0)
		return;

	/* Get a private in-memory rec_map, which we can modify. */
	map = mail_index_sync_get_atomic_map(ctx);

	/* call the expunge handlers first */
	if (sync_expunge_handlers_init(ctx)) {
		for (i = 0; i < count; i++) {
			sync_expunge_call_handlers(ctx,
				range[i].seq1, range[i].seq2);
		}
	}

	prev_seq2 = 0;
	dest_seq1 = 1;
	orig_rec_count = map->rec_map->records_count;
	for (i = 0; i < count; i++) {
		uint32_t seq1 = range[i].seq1;
		uint32_t seq2 = range[i].seq2;
		struct mail_index_record *rec;
		uint32_t seq_count, seq;

		i_assert(seq1 > prev_seq2);

		for (seq = seq1; seq <= seq2; seq++) {
			rec = MAIL_INDEX_REC_AT_SEQ(map, seq);
			mail_index_sync_header_update_counts(ctx, rec->uid, rec->flags, 0);
		}

		if (prev_seq2+1 <= seq1-1) {
			/* @UNSAFE: move (prev_seq2+1) .. (seq1-1) to its
			   final location in the map if necessary */
			uint32_t move_count = (seq1-1) - (prev_seq2+1) + 1;
			if (prev_seq2+1-1 != dest_seq1-1)
				memmove(MAIL_INDEX_REC_AT_SEQ(map, dest_seq1),
					MAIL_INDEX_REC_AT_SEQ(map, prev_seq2+1),
					move_count * map->hdr.record_size);
			dest_seq1 += move_count;
		}
		seq_count = seq2 - seq1 + 1;
		map->rec_map->records_count -= seq_count;
		map->hdr.messages_count -= seq_count;
		prev_seq2 = seq2;
	}
	/* Final stragglers */
	if (orig_rec_count > prev_seq2) {
		uint32_t final_move_count = orig_rec_count - prev_seq2;
		memmove(MAIL_INDEX_REC_AT_SEQ(map, dest_seq1),
			MAIL_INDEX_REC_AT_SEQ(map, prev_seq2+1),
			final_move_count * map->hdr.record_size);
	}
}

static void *sync_append_record(struct mail_index_map *map)
{
	size_t append_pos;
	void *ret;

	append_pos = map->rec_map->records_count * map->hdr.record_size;
	ret = buffer_get_space_unsafe(map->rec_map->buffer, append_pos,
				      map->hdr.record_size);
	map->rec_map->records =
		buffer_get_modifiable_data(map->rec_map->buffer, NULL);
	return ret;
}

static bool sync_update_ignored_change(struct mail_index_sync_map_ctx *ctx)
{
	struct mail_index_transaction_commit_result *result =
		ctx->view->index->sync_commit_result;
	uint32_t prev_log_seq;
	uoff_t prev_log_offset, trans_start_offset, trans_end_offset;

	if (result == NULL)
		return FALSE;

	/* we'll return TRUE if this modseq change was written within the
	   transaction that was just committed */
	mail_transaction_log_view_get_prev_pos(ctx->view->log_view,
					       &prev_log_seq, &prev_log_offset);
	if (prev_log_seq != result->log_file_seq)
		return FALSE;

	trans_end_offset = result->log_file_offset;
	trans_start_offset = trans_end_offset - result->commit_size;
	if (prev_log_offset < trans_start_offset ||
	    prev_log_offset >= trans_end_offset)
		return FALSE;

	return TRUE;
}

static int
sync_modseq_update(struct mail_index_sync_map_ctx *ctx,
		   const struct mail_transaction_modseq_update *u,
		   unsigned int size)
{
	struct mail_index_view *view = ctx->view;
	const struct mail_transaction_modseq_update *end;
	uint32_t seq;
	uint64_t min_modseq;
	int ret;

	end = CONST_PTR_OFFSET(u, size);
	for (; u < end; u++) {
		if (u->uid == 0)
			seq = 0;
		else if (!mail_index_lookup_seq(view, u->uid, &seq))
			continue;

		min_modseq = ((uint64_t)u->modseq_high32 << 32) |
			u->modseq_low32;

		ret = seq == 0 ? 1 :
			mail_index_modseq_set(view, seq, min_modseq);
		if (ret < 0) {
			mail_index_sync_set_corrupted(ctx,
				"modseqs updated before they were enabled");
			return -1;
		}
		if (ret == 0 && sync_update_ignored_change(ctx))
			view->index->sync_commit_result->ignored_modseq_changes++;
	}
	return 1;
}

static int sync_append(const struct mail_index_record *rec,
		       struct mail_index_sync_map_ctx *ctx)
{
	struct mail_index_view *view = ctx->view;
	struct mail_index_map *map = view->map;
	const struct mail_index_record *old_rec;
	enum mail_flags new_flags;
	void *dest;

	if (rec->uid < map->hdr.next_uid) {
		mail_index_sync_set_corrupted(ctx,
			"Append with UID %u, but next_uid = %u",
			rec->uid, map->hdr.next_uid);
		return -1;
	}

	/* We'll need to append a new record. If map currently points to
	   mmap()ed index, it first needs to be moved to memory since we can't
	   write past the mmap()ed memory area. */
	map = mail_index_sync_move_to_private_memory(ctx);

	if (rec->uid <= map->rec_map->last_appended_uid) {
		i_assert(map->hdr.messages_count < map->rec_map->records_count);
		/* the flags may have changed since it was added to map.
		   use the updated flags already, so flag counters won't get
		   broken. */
		old_rec = MAIL_INDEX_MAP_IDX(map, map->hdr.messages_count);
		i_assert(old_rec->uid == rec->uid);
		new_flags = old_rec->flags;
	} else {
		/* don't rely on buffer->used being at the correct position.
		   at least expunges can move it */
		dest = sync_append_record(map);
		memcpy(dest, rec, sizeof(*rec));
		memset(PTR_OFFSET(dest, sizeof(*rec)), 0,
		       map->hdr.record_size - sizeof(*rec));
		map->rec_map->records_count++;
		map->rec_map->last_appended_uid = rec->uid;
		new_flags = rec->flags;

		mail_index_modseq_update_to_highest(
			ctx->modseq_ctx, map->rec_map->records_count,
			map->rec_map->records_count);
	}

	map->hdr.messages_count++;
	map->hdr.next_uid = rec->uid+1;

	if ((new_flags & MAIL_INDEX_MAIL_FLAG_DIRTY) != 0 &&
	    (view->index->flags & MAIL_INDEX_OPEN_FLAG_NO_DIRTY) == 0)
		map->hdr.flags |= MAIL_INDEX_HDR_FLAG_HAVE_DIRTY;

	mail_index_header_update_lowwaters(ctx, rec->uid, new_flags);
	mail_index_sync_header_update_counts(ctx, rec->uid, 0, new_flags);
	return 1;
}

static int sync_flag_update(const struct mail_transaction_flag_update *u,
			    struct mail_index_sync_map_ctx *ctx)
{
	struct mail_index_view *view = ctx->view;
	struct mail_index_record *rec;
	uint8_t flag_mask, old_flags;
	uint32_t seq, seq1, seq2;

	if (!mail_index_lookup_seq_range(view, u->uid1, u->uid2, &seq1, &seq2))
		return 1;

	if (!MAIL_TRANSACTION_FLAG_UPDATE_IS_INTERNAL(u))
		mail_index_modseq_update_to_highest(ctx->modseq_ctx, seq1, seq2);

	if ((u->add_flags & MAIL_INDEX_MAIL_FLAG_DIRTY) != 0 &&
	    (view->index->flags & MAIL_INDEX_OPEN_FLAG_NO_DIRTY) == 0)
		view->map->hdr.flags |= MAIL_INDEX_HDR_FLAG_HAVE_DIRTY;

        flag_mask = (unsigned char)~u->remove_flags;

	if (((u->add_flags | u->remove_flags) &
	     (MAIL_SEEN | MAIL_DELETED)) == 0) {
		/* we're not modifying any counted/lowwatered flags */
		for (seq = seq1; seq <= seq2; seq++) {
			rec = MAIL_INDEX_REC_AT_SEQ(view->map, seq);
			rec->flags = (rec->flags & flag_mask) | u->add_flags;
		}
	} else {
		for (seq = seq1; seq <= seq2; seq++) {
			rec = MAIL_INDEX_REC_AT_SEQ(view->map, seq);

			old_flags = rec->flags;
			rec->flags = (rec->flags & flag_mask) | u->add_flags;

			mail_index_header_update_lowwaters(ctx, rec->uid,
							   rec->flags);
			mail_index_sync_header_update_counts_all(ctx, rec->uid,
								 old_flags,
								 rec->flags);
		}
	}
	return 1;
}

static int sync_header_update(const struct mail_transaction_header_update *u,
			      struct mail_index_sync_map_ctx *ctx)
{
	struct mail_index_map *map = ctx->view->map;
	uint32_t orig_log_file_tail_offset = map->hdr.log_file_tail_offset;
	uint32_t orig_next_uid = map->hdr.next_uid;

	if (u->offset >= map->hdr.base_header_size ||
	    u->offset + u->size > map->hdr.base_header_size) {
		mail_index_sync_set_corrupted(ctx,
			"Header update outside range: %u + %u > %u",
			u->offset, u->size, map->hdr.base_header_size);
		return -1;
	}

	buffer_write(map->hdr_copy_buf, u->offset, u + 1, u->size);
	i_assert(map->hdr_copy_buf->used == map->hdr.header_size);

	/* @UNSAFE */
	if ((uint32_t)(u->offset + u->size) <= sizeof(map->hdr)) {
		memcpy(PTR_OFFSET(&map->hdr, u->offset),
		       u + 1, u->size);
	} else if (u->offset < sizeof(map->hdr)) {
		memcpy(PTR_OFFSET(&map->hdr, u->offset),
		       u + 1, sizeof(map->hdr) - u->offset);
	}

	if (map->hdr.next_uid < orig_next_uid) {
		/* next_uid update tried to shrink its value. this can happen
		   in some race conditions with e.g. with dsync, so just
		   silently ignore it. */
		map->hdr.next_uid = orig_next_uid;
	}

	/* the tail offset updates are intended for internal transaction
	   log handling. we'll update the offset in the header only when
	   the sync is finished. */
	map->hdr.log_file_tail_offset = orig_log_file_tail_offset;
	return 1;
}

static int
mail_index_sync_record_real(struct mail_index_sync_map_ctx *ctx,
			    const struct mail_transaction_header *hdr,
			    const void *data)
{
	int ret = 0;

	switch (hdr->type & MAIL_TRANSACTION_TYPE_MASK) {
	case MAIL_TRANSACTION_APPEND: {
		const struct mail_index_record *rec, *end;

		end = CONST_PTR_OFFSET(data, hdr->size);
		for (rec = data; rec < end; rec++) {
			ret = sync_append(rec, ctx);
			if (ret <= 0)
				break;
		}
		break;
	}
	case MAIL_TRANSACTION_EXPUNGE:
	case MAIL_TRANSACTION_EXPUNGE|MAIL_TRANSACTION_EXPUNGE_PROT: {
		const struct mail_transaction_expunge *rec = data, *end;
		ARRAY_TYPE(seq_range) seqs;
		uint32_t seq1, seq2;

		if ((hdr->type & MAIL_TRANSACTION_EXTERNAL) == 0) {
			/* this is simply a request for expunge */
			break;
		}
		t_array_init(&seqs, 64);
		end = CONST_PTR_OFFSET(data, hdr->size);
		for (; rec != end; rec++) {
			if (mail_index_lookup_seq_range(ctx->view,
					rec->uid1, rec->uid2, &seq1, &seq2))
				seq_range_array_add_range(&seqs, seq1, seq2);
		}
		sync_expunge_range(ctx, &seqs);
		break;
	}
	case MAIL_TRANSACTION_EXPUNGE_GUID:
	case MAIL_TRANSACTION_EXPUNGE_GUID|MAIL_TRANSACTION_EXPUNGE_PROT: {
		const struct mail_transaction_expunge_guid *rec = data, *end;
		ARRAY_TYPE(seq_range) seqs;
		uint32_t seq;

		if ((hdr->type & MAIL_TRANSACTION_EXTERNAL) == 0) {
			/* this is simply a request for expunge */
			break;
		}
		t_array_init(&seqs, 64);
		end = CONST_PTR_OFFSET(data, hdr->size);
		for (; rec != end; rec++) {
			i_assert(rec->uid != 0);

			if (mail_index_lookup_seq(ctx->view, rec->uid, &seq))
				seq_range_array_add(&seqs, seq);
		}

		sync_expunge_range(ctx, &seqs);
		break;
	}
	case MAIL_TRANSACTION_FLAG_UPDATE: {
		const struct mail_transaction_flag_update *rec, *end;

		end = CONST_PTR_OFFSET(data, hdr->size);
		for (rec = data; rec < end; rec++) {
			ret = sync_flag_update(rec, ctx);
			if (ret <= 0)
				break;
		}
		break;
	}
	case MAIL_TRANSACTION_HEADER_UPDATE: {
		const struct mail_transaction_header_update *rec;
		unsigned int i;

		for (i = 0; i < hdr->size; ) {
			rec = CONST_PTR_OFFSET(data, i);
			ret = sync_header_update(rec, ctx);
			if (ret <= 0)
				break;

			i += sizeof(*rec) + rec->size;
			if ((i % 4) != 0)
				i += 4 - (i % 4);
		}
		break;
	}
	case MAIL_TRANSACTION_EXT_INTRO: {
		const struct mail_transaction_ext_intro *rec = data;
		unsigned int i;
		uint32_t prev_seq;
		uoff_t prev_offset;

		mail_transaction_log_view_get_prev_pos(ctx->view->log_view,
						       &prev_seq, &prev_offset);
		ctx->ext_intro_seq = prev_seq;
		ctx->ext_intro_offset = prev_offset;
		ctx->ext_intro_end_offset =
			prev_offset + hdr->size + sizeof(*hdr);

		for (i = 0; i < hdr->size; ) {
			if (i + sizeof(*rec) > hdr->size) {
				/* should be just extra padding */
				break;
			}

			rec = CONST_PTR_OFFSET(data, i);
			/* name_size checked by _log_view_next() */
			i_assert(i + sizeof(*rec) + rec->name_size <= hdr->size);

			ret = mail_index_sync_ext_intro(ctx, rec);
			if (ret <= 0)
				break;

			i += sizeof(*rec) + rec->name_size;
			if ((i % 4) != 0)
				i += 4 - (i % 4);
		}
		break;
	}
	case MAIL_TRANSACTION_EXT_RESET: {
		struct mail_transaction_ext_reset rec;

		/* old versions have only new_reset_id */
		if (hdr->size < sizeof(uint32_t)) {
			mail_index_sync_set_corrupted(ctx,
				"ext reset: invalid record size");
			ret = -1;
			break;
		}
		i_zero(&rec);
		memcpy(&rec, data, I_MIN(hdr->size, sizeof(rec)));
		ret = mail_index_sync_ext_reset(ctx, &rec);
		break;
	}
	case MAIL_TRANSACTION_EXT_HDR_UPDATE: {
		const struct mail_transaction_ext_hdr_update *rec;
		unsigned int i;

		for (i = 0; i < hdr->size; ) {
			rec = CONST_PTR_OFFSET(data, i);

			if (i + sizeof(*rec) > hdr->size ||
			    i + sizeof(*rec) + rec->size > hdr->size) {
				mail_index_sync_set_corrupted(ctx,
					"ext hdr update: invalid record size");
				ret = -1;
				break;
			}

			ret = mail_index_sync_ext_hdr_update(ctx, rec->offset,
							     rec->size, rec + 1);
			if (ret <= 0)
				break;

			i += sizeof(*rec) + rec->size;
			if ((i % 4) != 0)
				i += 4 - (i % 4);
		}
		break;
	}
	case MAIL_TRANSACTION_EXT_HDR_UPDATE32: {
		const struct mail_transaction_ext_hdr_update32 *rec;
		unsigned int i;

		for (i = 0; i < hdr->size; ) {
			rec = CONST_PTR_OFFSET(data, i);

			if (i + sizeof(*rec) > hdr->size ||
			    i + sizeof(*rec) + rec->size > hdr->size) {
				mail_index_sync_set_corrupted(ctx,
					"ext hdr update: invalid record size");
				ret = -1;
				break;
			}

			ret = mail_index_sync_ext_hdr_update(ctx, rec->offset,
							     rec->size, rec + 1);
			if (ret <= 0)
				break;

			i += sizeof(*rec) + rec->size;
			if ((i % 4) != 0)
				i += 4 - (i % 4);
		}
		break;
	}
	case MAIL_TRANSACTION_EXT_REC_UPDATE: {
		const struct mail_transaction_ext_rec_update *rec;
		unsigned int i, record_size;

		if (ctx->cur_ext_map_idx == (uint32_t)-1) {
			mail_index_sync_set_corrupted(ctx,
				"Extension record updated "
				"without intro prefix");
			ret = -1;
			break;
		}

		if (ctx->cur_ext_ignore) {
			ret = 1;
			break;
		}

		/* the record is padded to 32bits in the transaction log */
		record_size = (sizeof(*rec) + ctx->cur_ext_record_size + 3) & ~3U;

		for (i = 0; i < hdr->size; i += record_size) {
			rec = CONST_PTR_OFFSET(data, i);

			if (i + record_size > hdr->size) {
				mail_index_sync_set_corrupted(ctx,
					"ext rec update: invalid record size");
				ret = -1;
				break;
			}

			ret = mail_index_sync_ext_rec_update(ctx, rec);
			if (ret <= 0)
				break;
		}
		break;
	}
	case MAIL_TRANSACTION_EXT_ATOMIC_INC: {
		const struct mail_transaction_ext_atomic_inc *rec, *end;

		if (ctx->cur_ext_map_idx == (uint32_t)-1) {
			mail_index_sync_set_corrupted(ctx,
				"Extension record updated "
				"without intro prefix");
			ret = -1;
			break;
		}

		if (ctx->cur_ext_ignore) {
			ret = 1;
			break;
		}

		end = CONST_PTR_OFFSET(data, hdr->size);
		for (rec = data; rec < end; rec++) {
			ret = mail_index_sync_ext_atomic_inc(ctx, rec);
			if (ret <= 0)
				break;
		}
		break;
	}
	case MAIL_TRANSACTION_KEYWORD_UPDATE: {
		const struct mail_transaction_keyword_update *rec = data;

		ret = mail_index_sync_keywords(ctx, hdr, rec);
		break;
	}
	case MAIL_TRANSACTION_KEYWORD_RESET: {
		const struct mail_transaction_keyword_reset *rec = data;

		ret = mail_index_sync_keywords_reset(ctx, hdr, rec);
		break;
	}
	case MAIL_TRANSACTION_MODSEQ_UPDATE: {
		const struct mail_transaction_modseq_update *rec = data;

		ret = sync_modseq_update(ctx, rec, hdr->size);
		break;
	}
	case MAIL_TRANSACTION_INDEX_DELETED:
		if ((hdr->type & MAIL_TRANSACTION_EXTERNAL) == 0) {
			/* next sync finishes the deletion */
			ctx->view->index->index_delete_requested = TRUE;
		} else {
			/* transaction log reading handles this */
		}
		break;
	case MAIL_TRANSACTION_INDEX_UNDELETED:
		ctx->view->index->index_delete_requested = FALSE;
		break;
	case MAIL_TRANSACTION_BOUNDARY:
		break;
	case MAIL_TRANSACTION_ATTRIBUTE_UPDATE:
		break;
	default:
		mail_index_sync_set_corrupted(ctx,
			"Unknown transaction record type 0x%x",
			(hdr->type & MAIL_TRANSACTION_TYPE_MASK));
		ret = -1;
		break;
	}
	return ret;
}

int mail_index_sync_record(struct mail_index_sync_map_ctx *ctx,
			   const struct mail_transaction_header *hdr,
			   const void *data)
{
	int ret;

	T_BEGIN {
		ret = mail_index_sync_record_real(ctx, hdr, data);
	} T_END;
	return ret;
}

void mail_index_sync_map_init(struct mail_index_sync_map_ctx *sync_map_ctx,
			      struct mail_index_view *view,
			      enum mail_index_sync_handler_type type)
{
	i_zero(sync_map_ctx);
	sync_map_ctx->view = view;
	sync_map_ctx->cur_ext_map_idx = (uint32_t)-1;
	sync_map_ctx->type = type;
	sync_map_ctx->modseq_ctx = mail_index_modseq_sync_begin(sync_map_ctx);

	mail_index_sync_init_handlers(sync_map_ctx);
}

void mail_index_sync_map_deinit(struct mail_index_sync_map_ctx *sync_map_ctx)
{
	i_assert(sync_map_ctx->modseq_ctx == NULL);

	buffer_free(&sync_map_ctx->unknown_extensions);
	if (sync_map_ctx->expunge_handlers_used)
		mail_index_sync_deinit_expunge_handlers(sync_map_ctx);
	mail_index_sync_deinit_handlers(sync_map_ctx);
}

static void mail_index_sync_update_hdr_dirty_flag(struct mail_index_map *map)
{
	const struct mail_index_record *rec;
	uint32_t seq;

	if ((map->hdr.flags & MAIL_INDEX_HDR_FLAG_HAVE_DIRTY) != 0 ||
	    (map->index->flags & MAIL_INDEX_OPEN_FLAG_NO_DIRTY) != 0)
		return;

	/* do we have dirty flags anymore? */
	for (seq = 1; seq <= map->rec_map->records_count; seq++) {
		rec = MAIL_INDEX_REC_AT_SEQ(map, seq);
		if ((rec->flags & MAIL_INDEX_MAIL_FLAG_DIRTY) != 0) {
			map->hdr.flags |= MAIL_INDEX_HDR_FLAG_HAVE_DIRTY;
			break;
		}
	}
}

#ifdef DEBUG
void mail_index_map_check(struct mail_index_map *map)
{
	const struct mail_index_header *hdr = &map->hdr;
	unsigned int del = 0, seen = 0;
	uint32_t seq, prev_uid = 0;

	if (getenv("DEBUG_IGNORE_INDEX_CORRUPTION") != NULL)
		return;

	i_assert(hdr->messages_count <= map->rec_map->records_count);
	for (seq = 1; seq <= hdr->messages_count; seq++) {
		const struct mail_index_record *rec;

		rec = MAIL_INDEX_REC_AT_SEQ(map, seq);
		i_assert(rec->uid > prev_uid);
		prev_uid = rec->uid;

		if ((rec->flags & MAIL_DELETED) != 0) {
			i_assert(rec->uid >= hdr->first_deleted_uid_lowwater);
			del++;
		}
		if ((rec->flags & MAIL_SEEN) != 0)
			seen++;
		else
			i_assert(rec->uid >= hdr->first_unseen_uid_lowwater);
	}
	i_assert(del == hdr->deleted_messages_count);
	i_assert(seen == hdr->seen_messages_count);
}
#endif

bool mail_index_sync_map_want_index_reopen(struct mail_index_map *map,
					   enum mail_index_sync_handler_type type)
{
	struct mail_index *index = map->index;

	if (index->log->head == NULL)
		return TRUE;

	uoff_t start_offset = type == MAIL_INDEX_SYNC_HANDLER_FILE ?
		map->hdr.log_file_tail_offset : map->hdr.log_file_head_offset;
	/* don't check this if mmap is disabled, because reopening
	   index causes sync to get lost. */
	if ((index->flags & MAIL_INDEX_OPEN_FLAG_MMAP_DISABLE) == 0) {
		uoff_t log_size, index_size;

		if (index->fd == -1 &&
		    index->log->head->hdr.prev_file_seq != 0) {
			/* we don't know the index's size, so use the
			   smallest index size we're willing to read */
			index_size = MAIL_INDEX_SYNC_MIN_READ_INDEX_SIZE;
		} else {
			index_size = map->hdr.header_size +
				map->rec_map->records_count *
				map->hdr.record_size;
		}

		/* this isn't necessary correct currently, but it should be
		   close enough */
		log_size = index->log->head->last_size;
		if (log_size > start_offset &&
		    log_size - start_offset > index_size)
			return TRUE;
	}
	return FALSE;
}

int mail_index_sync_map(struct mail_index_map **_map,
			enum mail_index_sync_handler_type type,
			const char **reason_r)
{
	struct mail_index_map *map = *_map;
	struct mail_index *index = map->index;
	struct mail_index_view *view;
	struct mail_index_sync_map_ctx sync_map_ctx;
	const struct mail_transaction_header *thdr;
	const void *tdata;
	uint32_t prev_seq;
	uoff_t start_offset, prev_offset;
	const char *reason, *error;
	int ret;
	bool had_dirty, reset;

	i_assert(index->log->head != NULL);
	i_assert(index->map == map || type == MAIL_INDEX_SYNC_HANDLER_VIEW);

	start_offset = type == MAIL_INDEX_SYNC_HANDLER_FILE ?
		map->hdr.log_file_tail_offset : map->hdr.log_file_head_offset;

	view = mail_index_view_open_with_map(index, map);
	ret = mail_transaction_log_view_set(view->log_view,
					    map->hdr.log_file_seq, start_offset,
					    (uint32_t)-1, UOFF_T_MAX,
					    &reset, &reason);
	if (ret <= 0) {
		mail_index_view_close(&view);
		if (ret < 0) {
			/* I/O failure */
			return -1;
		}
		/* the seq/offset is probably broken */
		*reason_r = t_strdup_printf(
			"Lost log for seq=%u offset=%"PRIuUOFF_T": %s "
			"(initial_mapped=%d)",
			map->hdr.log_file_seq, start_offset, reason,
			index->initial_mapped ? 1 : 0);
		return 0;
	}

	mail_transaction_log_get_head(index->log, &prev_seq, &prev_offset);
	if (prev_seq != map->hdr.log_file_seq ||
	    prev_offset - map->hdr.log_file_tail_offset >
	    		index->optimization_set.index.rewrite_min_log_bytes) {
		/* we're reading more from log than we would have preferred.
		   remember that we probably want to rewrite index soon. */
		index->index_min_write = TRUE;
	}

	/* view referenced the map. avoid unnecessary map cloning by
	   unreferencing the map while view exists. */
	map->refcount--;

	had_dirty = (map->hdr.flags & MAIL_INDEX_HDR_FLAG_HAVE_DIRTY) != 0;
	if (had_dirty)
		map->hdr.flags &= ENUM_NEGATE(MAIL_INDEX_HDR_FLAG_HAVE_DIRTY);

	mail_transaction_log_view_get_prev_pos(view->log_view,
					       &prev_seq, &prev_offset);

	mail_index_sync_map_init(&sync_map_ctx, view, type);
	if (reset) {
		/* Reset the entire index. Leave only indexid and
		   log_file_seq. */
		mail_transaction_log_view_get_prev_pos(view->log_view,
						       &prev_seq, &prev_offset);
		map = mail_index_map_alloc(index);
		if ((index->map->hdr.flags & MAIL_INDEX_HDR_FLAG_FSCKD) != 0)
			map->hdr.flags |= MAIL_INDEX_HDR_FLAG_FSCKD;
		map->hdr.log_file_seq = prev_seq;
		map->hdr.log_file_tail_offset = 0;
		mail_index_sync_replace_map(&sync_map_ctx, map);
	}
	map = NULL;

	/* mail_transaction_log_view_next() returns -1 on corruption.
	   Since the log file content before the corruption was found can be
	   useful and important, we don't fail this sync entirely. Instead,
	   we'll just mark the rest of the log file as synced. */
	while ((ret = mail_transaction_log_view_next(view->log_view, &thdr,
						     &tdata)) > 0) {
		mail_transaction_log_view_get_prev_pos(view->log_view,
						       &prev_seq, &prev_offset);

		if (LOG_IS_BEFORE(prev_seq, prev_offset,
				  view->map->hdr.log_file_seq,
				  view->map->hdr.log_file_head_offset)) {
			/* this has been synced already. */
			i_assert(type == MAIL_INDEX_SYNC_HANDLER_FILE);
			continue;
		}

		/* we'll just skip over broken entries */
		(void)mail_index_sync_record(&sync_map_ctx, thdr, tdata);
	}
	map = view->map;

	if (had_dirty)
		mail_index_sync_update_hdr_dirty_flag(map);
	mail_index_modseq_sync_end(&sync_map_ctx.modseq_ctx);

	mail_index_sync_update_log_offset(&sync_map_ctx, view->map, TRUE);

#ifdef DEBUG
	mail_index_map_check(map);
#endif
	i_assert(map->hdr.indexid == index->indexid || map->hdr.indexid == 0);

	/* transaction log tracks internally the current tail offset.
	   besides using header updates, it also updates the offset to skip
	   over following external transactions to avoid extra unneeded log
	   reading. */
	i_assert(map->hdr.log_file_seq == index->log->head->hdr.file_seq);
	if (map->hdr.log_file_tail_offset < index->log->head->max_tail_offset) {
		map->hdr.log_file_tail_offset =
			index->log->head->max_tail_offset;
	}

	buffer_write(map->hdr_copy_buf, 0, &map->hdr, sizeof(map->hdr));
	if (!MAIL_INDEX_MAP_IS_IN_MEMORY(map)) {
		memcpy(map->rec_map->mmap_base, map->hdr_copy_buf->data,
		       map->hdr_copy_buf->used);
	}

	/* restore refcount before closing the view. this is necessary also
	   if map got cloned, because view closing would otherwise destroy it */
	map->refcount++;
	mail_index_sync_map_deinit(&sync_map_ctx);
	mail_index_view_close(&view);

	i_assert(index->map == map || type == MAIL_INDEX_SYNC_HANDLER_VIEW);

	if (mail_index_map_check_header(map, &error) <= 0) {
		mail_index_set_error(index,
			"Synchronization corrupted index header %s: %s",
			index->filepath, error);
		(void)mail_index_fsck(index);
		map = index->map;
	} else if (sync_map_ctx.errors) {
		/* make sure the index looks valid now */
		(void)mail_index_fsck(index);
		map = index->map;
	}

	*_map = map;
	return ret < 0 ? -1 : 1;
}
