package syncer

import (
	"container/list"
	"context"
	"database/sql"
	"sync"
	"time"

	"golang.org/x/xerrors"

	"github.com/ipfs/go-cid"
	logging "github.com/ipfs/go-log/v2"

	"github.com/filecoin-project/lotus/api"
	"github.com/filecoin-project/lotus/chain/store"
	"github.com/filecoin-project/lotus/chain/types"
)

var log = logging.Logger("syncer")

type Syncer struct {
	db *sql.DB

	headerLk sync.Mutex
	node     api.FullNode
}

func NewSyncer(db *sql.DB, node api.FullNode) *Syncer {
	return &Syncer{
		db:   db,
		node: node,
	}
}

func (s *Syncer) setupSchemas() error {
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}

	if _, err := tx.Exec(`
create table if not exists block_cids
(
	cid text not null
		constraint block_cids_pk
			primary key
);

create unique index if not exists block_cids_cid_uindex
	on block_cids (cid);

create table if not exists blocks_synced
(
	cid text not null
		constraint blocks_synced_pk
			primary key
	    constraint blocks_block_cids_cid_fk
			references block_cids (cid),
	synced_at int not null,
	processed_at int
);

create unique index if not exists blocks_synced_cid_uindex
	on blocks_synced (cid,processed_at);

create table if not exists block_parents
(
	block text not null
	    constraint blocks_block_cids_cid_fk
			references block_cids (cid),
	parent text not null
);

create unique index if not exists block_parents_block_parent_uindex
	on block_parents (block, parent);

create table if not exists drand_entries
(
    round bigint not null
    	constraint drand_entries_pk
			primary key,
	data bytea not null
);
create unique index if not exists drand_entries_round_uindex
	on drand_entries (round);

create table if not exists block_drand_entries
(
    round bigint not null
    	constraint block_drand_entries_drand_entries_round_fk
			references drand_entries (round),
	block text not null
	    constraint blocks_block_cids_cid_fk
			references block_cids (cid)
);
create unique index if not exists block_drand_entries_round_uindex
	on block_drand_entries (round, block);

create table if not exists blocks
(
	cid text not null
		constraint blocks_pk
			primary key
	    constraint blocks_block_cids_cid_fk
			references block_cids (cid),
	parentWeight numeric not null,
	parentStateRoot text not null,
	height bigint not null,
	miner text not null,
	timestamp bigint not null,
	ticket bytea not null,
	election_proof bytea,
	win_count bigint,
	parent_base_fee text not null,
	forksig bigint not null
);

create unique index if not exists block_cid_uindex
	on blocks (cid,height);

create materialized view if not exists state_heights
    as select distinct height, parentstateroot from blocks;

create index if not exists state_heights_height_index
	on state_heights (height);

create index if not exists state_heights_parentstateroot_index
	on state_heights (parentstateroot);
`); err != nil {
		return err
	}

	return tx.Commit()
}

func (s *Syncer) Start(ctx context.Context) {
	log.Debug("Starting Syncer")

	if err := s.setupSchemas(); err != nil {
		log.Fatal(err)
	}

	// doing the initial sync here lets us avoid the HCCurrent case in the switch
	head, err := s.node.ChainHead(ctx)
	if err != nil {
		log.Fatalw("Failed to get chain head form lotus", "error", err)
	}

	unsynced, err := s.unsyncedBlocks(ctx, head, time.Unix(0, 0))
	if err != nil {
		log.Fatalw("failed to gather unsynced blocks", "error", err)
	}

	if err := s.storeHeaders(unsynced, true, time.Now()); err != nil {
		log.Fatalw("failed to store unsynced blocks", "error", err)
	}

	// continue to keep the block headers table up to date.
	notifs, err := s.node.ChainNotify(ctx)
	if err != nil {
		log.Fatal(err)
	}

	lastSynced := time.Now()
	go func() {
		for notif := range notifs {
			for _, change := range notif {
				switch change.Type {
				case store.HCApply:
					unsynced, err := s.unsyncedBlocks(ctx, change.Val, lastSynced)
					if err != nil {
						log.Errorw("failed to gather unsynced blocks", "error", err)
					}

					if len(unsynced) == 0 {
						continue
					}

					if err := s.storeHeaders(unsynced, true, lastSynced); err != nil {
						// so this is pretty bad, need some kind of retry..
						// for now just log an error and the blocks will be attempted again on next notifi
						log.Errorw("failed to store unsynced blocks", "error", err)
					}

					lastSynced = time.Now()
				case store.HCRevert:
					log.Debug("revert todo")
				}
			}
		}
	}()
}

func (s *Syncer) unsyncedBlocks(ctx context.Context, head *types.TipSet, since time.Time) (map[cid.Cid]*types.BlockHeader, error) {
	// get a list of blocks we have already synced in the past 3 mins. This ensures we aren't returning the entire
	// table every time.
	lookback := since.Add(-(time.Minute * 3))
	log.Debugw("Gathering unsynced blocks", "since", lookback.String())
	hasList, err := s.syncedBlocks(lookback)
	if err != nil {
		return nil, err
	}

	// build a list of blocks that we have not synced.
	toVisit := list.New()
	for _, header := range head.Blocks() {
		toVisit.PushBack(header)
	}

	toSync := map[cid.Cid]*types.BlockHeader{}

	for toVisit.Len() > 0 {
		bh := toVisit.Remove(toVisit.Back()).(*types.BlockHeader)
		_, has := hasList[bh.Cid()]
		if _, seen := toSync[bh.Cid()]; seen || has {
			continue
		}

		toSync[bh.Cid()] = bh
		if len(toSync)%500 == 10 {
			log.Debugw("To visit", "toVisit", toVisit.Len(), "toSync", len(toSync), "current_height", bh.Height)
		}

		if len(bh.Parents) == 0 {
			continue
		}

		pts, err := s.node.ChainGetTipSet(ctx, types.NewTipSetKey(bh.Parents...))
		if err != nil {
			log.Error(err)
			continue
		}

		for _, header := range pts.Blocks() {
			toVisit.PushBack(header)
		}
	}
	log.Debugw("Gathered unsynced blocks", "count", len(toSync))
	return toSync, nil
}

func (s *Syncer) syncedBlocks(timestamp time.Time) (map[cid.Cid]struct{}, error) {
	// timestamp is used to return a configurable amount of rows based on when they were last added.
	rws, err := s.db.Query(`select cid FROM blocks_synced where synced_at > $1`, timestamp.Unix())
	if err != nil {
		return nil, xerrors.Errorf("Failed to query blocks_synced: %w", err)
	}
	out := map[cid.Cid]struct{}{}

	for rws.Next() {
		var c string
		if err := rws.Scan(&c); err != nil {
			return nil, xerrors.Errorf("Failed to scan blocks_synced: %w", err)
		}

		ci, err := cid.Parse(c)
		if err != nil {
			return nil, xerrors.Errorf("Failed to parse blocks_synced: %w", err)
		}

		out[ci] = struct{}{}
	}
	return out, nil
}

func (s *Syncer) storeHeaders(bhs map[cid.Cid]*types.BlockHeader, sync bool, timestamp time.Time) error {
	s.headerLk.Lock()
	defer s.headerLk.Unlock()
	if len(bhs) == 0 {
		return nil
	}
	log.Debugw("Storing Headers", "count", len(bhs))

	tx, err := s.db.Begin()
	if err != nil {
		return xerrors.Errorf("begin: %w", err)
	}

	if _, err := tx.Exec(`

create temp table bc (like block_cids excluding constraints) on commit drop;
create temp table de (like drand_entries excluding constraints) on commit drop;
create temp table bde (like block_drand_entries excluding constraints) on commit drop;
create temp table tbp (like block_parents excluding constraints) on commit drop;
create temp table bs (like blocks_synced excluding constraints) on commit drop;
create temp table b (like blocks excluding constraints) on commit drop;


`); err != nil {
		return xerrors.Errorf("prep temp: %w", err)
	}

	{
		stmt, err := tx.Prepare(`copy bc (cid) from STDIN`)
		if err != nil {
			return err
		}

		for _, bh := range bhs {
			if _, err := stmt.Exec(bh.Cid().String()); err != nil {
				log.Error(err)
			}
		}

		if err := stmt.Close(); err != nil {
			return err
		}

		if _, err := tx.Exec(`insert into block_cids select * from bc on conflict do nothing `); err != nil {
			return xerrors.Errorf("drand entries put: %w", err)
		}
	}

	{
		stmt, err := tx.Prepare(`copy de (round, data) from STDIN`)
		if err != nil {
			return err
		}

		for _, bh := range bhs {
			for _, ent := range bh.BeaconEntries {
				if _, err := stmt.Exec(ent.Round, ent.Data); err != nil {
					log.Error(err)
				}
			}
		}

		if err := stmt.Close(); err != nil {
			return err
		}

		if _, err := tx.Exec(`insert into drand_entries select * from de on conflict do nothing `); err != nil {
			return xerrors.Errorf("drand entries put: %w", err)
		}
	}

	{
		stmt, err := tx.Prepare(`copy bde (round, block) from STDIN`)
		if err != nil {
			return err
		}

		for _, bh := range bhs {
			for _, ent := range bh.BeaconEntries {
				if _, err := stmt.Exec(ent.Round, bh.Cid().String()); err != nil {
					log.Error(err)
				}
			}
		}

		if err := stmt.Close(); err != nil {
			return err
		}

		if _, err := tx.Exec(`insert into block_drand_entries select * from bde on conflict do nothing `); err != nil {
			return xerrors.Errorf("block drand entries put: %w", err)
		}
	}

	{
		stmt, err := tx.Prepare(`copy tbp (block, parent) from STDIN`)
		if err != nil {
			return err
		}

		for _, bh := range bhs {
			for _, parent := range bh.Parents {
				if _, err := stmt.Exec(bh.Cid().String(), parent.String()); err != nil {
					log.Error(err)
				}
			}
		}

		if err := stmt.Close(); err != nil {
			return err
		}

		if _, err := tx.Exec(`insert into block_parents select * from tbp on conflict do nothing `); err != nil {
			return xerrors.Errorf("parent put: %w", err)
		}
	}

	if sync {

		stmt, err := tx.Prepare(`copy bs (cid, synced_at) from stdin `)
		if err != nil {
			return err
		}

		for _, bh := range bhs {
			if _, err := stmt.Exec(bh.Cid().String(), timestamp.Unix()); err != nil {
				log.Error(err)
			}
		}

		if err := stmt.Close(); err != nil {
			return err
		}

		if _, err := tx.Exec(`insert into blocks_synced select * from bs on conflict do nothing `); err != nil {
			return xerrors.Errorf("syncd put: %w", err)
		}
	}

	stmt2, err := tx.Prepare(`copy b (cid, parentWeight, parentStateRoot, height, miner, "timestamp", ticket, election_proof, win_count, parent_base_fee, forksig) from stdin`)
	if err != nil {
		return err
	}

	for _, bh := range bhs {
		var eproof, winCount interface{}
		if bh.ElectionProof != nil {
			eproof = bh.ElectionProof.VRFProof
			winCount = bh.ElectionProof.WinCount
		}

		if bh.Ticket == nil {
			log.Warnf("got a block with nil ticket")

			bh.Ticket = &types.Ticket{
				VRFProof: []byte{},
			}
		}

		if _, err := stmt2.Exec(
			bh.Cid().String(),
			bh.ParentWeight.String(),
			bh.ParentStateRoot.String(),
			bh.Height,
			bh.Miner.String(),
			bh.Timestamp,
			bh.Ticket.VRFProof,
			eproof,
			winCount,
			bh.ParentBaseFee.String(),
			bh.ForkSignaling); err != nil {
			log.Error(err)
		}
	}

	if err := stmt2.Close(); err != nil {
		return xerrors.Errorf("s2 close: %w", err)
	}

	if _, err := tx.Exec(`insert into blocks select * from b on conflict do nothing `); err != nil {
		return xerrors.Errorf("blk put: %w", err)
	}

	return tx.Commit()
}