package sealing

import (
	"bytes"
	"context"
	"sort"
	"sync"
	"time"

	"github.com/ipfs/go-cid"
	"golang.org/x/xerrors"

	"github.com/filecoin-project/go-address"
	"github.com/filecoin-project/go-state-types/abi"
	"github.com/filecoin-project/go-state-types/big"
	miner0 "github.com/filecoin-project/specs-actors/actors/builtin/miner"
	miner5 "github.com/filecoin-project/specs-actors/v5/actors/builtin/miner"

	"github.com/filecoin-project/lotus/api"
	"github.com/filecoin-project/lotus/chain/actors/builtin/miner"
)

var (
	// TODO: config

	PreCommitBatchMax  uint64 = 100 // adjust based on real-world gas numbers, actors limit at 10k
	PreCommitBatchMin  uint64 = 1
	PreCommitBatchWait        = 5 * time.Minute
)

type PreCommitBatcherApi interface {
	SendMsg(ctx context.Context, from, to address.Address, method abi.MethodNum, value, maxFee abi.TokenAmount, params []byte) (cid.Cid, error)
	StateMinerInfo(context.Context, address.Address, TipSetToken) (miner.MinerInfo, error)
	ChainHead(ctx context.Context) (TipSetToken, abi.ChainEpoch, error)
}

type PreCommitBatcher struct {
	api       PreCommitBatcherApi
	maddr     address.Address
	mctx      context.Context
	addrSel   AddrSel
	feeCfg    FeeConfig
	getConfig GetSealingConfigFunc

	deadlines map[abi.SectorNumber]time.Time
	todo      map[abi.SectorNumber]*miner0.SectorPreCommitInfo
	waiting   map[abi.SectorNumber][]chan cid.Cid

	notify, stop, stopped chan struct{}
	force                 chan chan *cid.Cid
	lk                    sync.Mutex
}

func NewPreCommitBatcher(mctx context.Context, maddr address.Address, api PreCommitBatcherApi, addrSel AddrSel, feeCfg FeeConfig, getConfig GetSealingConfigFunc) *PreCommitBatcher {
	b := &PreCommitBatcher{
		api:       api,
		maddr:     maddr,
		mctx:      mctx,
		addrSel:   addrSel,
		feeCfg:    feeCfg,
		getConfig: getConfig,

		deadlines: map[abi.SectorNumber]time.Time{},
		todo:      map[abi.SectorNumber]*miner0.SectorPreCommitInfo{},
		waiting:   map[abi.SectorNumber][]chan cid.Cid{},

		notify:  make(chan struct{}, 1),
		force:   make(chan chan *cid.Cid),
		stop:    make(chan struct{}),
		stopped: make(chan struct{}),
	}

	go b.run()

	return b
}

func (b *PreCommitBatcher) run() {
	var forceRes chan *cid.Cid
	var lastMsg *cid.Cid

	cfg, err := b.getConfig()
	if err != nil {
		panic(err)
	}

	for {
		if forceRes != nil {
			forceRes <- lastMsg
			forceRes = nil
		}
		lastMsg = nil

		var sendAboveMax, sendAboveMin bool
		select {
		case <-b.stop:
			close(b.stopped)
			return
		case <-b.notify:
			sendAboveMax = true
		case <-time.After(b.batchWait(cfg.PreCommitBatchWait, cfg.PreCommitBatchSlack)):
			sendAboveMin = true
		case fr := <-b.force: // user triggered
			forceRes = fr
		}

		var err error
		lastMsg, err = b.processBatch(sendAboveMax, sendAboveMin)
		if err != nil {
			log.Warnw("TerminateBatcher processBatch error", "error", err)
		}
	}
}

func (b *PreCommitBatcher) batchWait(maxWait, slack time.Duration) time.Duration {
	now := time.Now()

	b.lk.Lock()
	defer b.lk.Unlock()

	var deadline time.Time
	for sn := range b.todo {
		sectorDeadline := b.deadlines[sn]
		if deadline.IsZero() || (!sectorDeadline.IsZero() && sectorDeadline.Before(deadline)) {
			deadline = sectorDeadline
		}
	}
	for sn := range b.waiting {
		sectorDeadline := b.deadlines[sn]
		if deadline.IsZero() || (!sectorDeadline.IsZero() && sectorDeadline.Before(deadline)) {
			deadline = sectorDeadline
		}
	}

	if deadline.IsZero() {
		return maxWait
	}

	deadline = deadline.Add(-slack)
	if deadline.Before(now) {
		return time.Nanosecond // can't return 0
	}

	wait := deadline.Sub(now)
	if wait > maxWait {
		wait = maxWait
	}

	return wait
}

func (b *PreCommitBatcher) processBatch(notif, after bool) (*cid.Cid, error) {
	b.lk.Lock()
	defer b.lk.Unlock()
	params := miner5.PreCommitSectorBatchParams{}

	total := len(b.todo)
	if total == 0 {
		return nil, nil // nothing to do
	}

	cfg, err := b.getConfig()
	if err != nil {
		return nil, xerrors.Errorf("getting config: %w", err)
	}

	if notif && total < cfg.MaxPreCommitBatch {
		return nil, nil
	}

	if after && total < cfg.MinPreCommitBatch {
		return nil, nil
	}

	for _, p := range b.todo {
		params.Sectors = append(params.Sectors, p)
	}

	enc := new(bytes.Buffer)
	if err := params.MarshalCBOR(enc); err != nil {
		return nil, xerrors.Errorf("couldn't serialize PreCommitSectorBatchParams: %w", err)
	}

	mi, err := b.api.StateMinerInfo(b.mctx, b.maddr, nil)
	if err != nil {
		return nil, xerrors.Errorf("couldn't get miner info: %w", err)
	}

	from, _, err := b.addrSel(b.mctx, mi, api.PreCommitAddr, b.feeCfg.MaxPreCommitGasFee, b.feeCfg.MaxPreCommitGasFee)
	if err != nil {
		return nil, xerrors.Errorf("no good address found: %w", err)
	}

	mcid, err := b.api.SendMsg(b.mctx, from, b.maddr, miner.Methods.PreCommitSectorBatch, big.Zero(), b.feeCfg.MaxPreCommitGasFee, enc.Bytes())
	if err != nil {
		return nil, xerrors.Errorf("sending message failed: %w", err)
	}

	log.Infow("Sent ProveCommitAggregate message", "cid", mcid, "from", from, "sectors", total)

	for _, sector := range params.Sectors {
		sn := sector.SectorNumber

		for _, ch := range b.waiting[sn] {
			ch <- mcid // buffered
		}
		delete(b.waiting, sn)
		delete(b.todo, sn)
		delete(b.deadlines, sn)
	}

	return &mcid, nil
}

// register PreCommit, wait for batch message, return message CID
func (b *PreCommitBatcher) AddPreCommit(ctx context.Context, s SectorInfo, in *miner0.SectorPreCommitInfo) (mcid cid.Cid, err error) {
	_, curEpoch, err := b.api.ChainHead(b.mctx)
	if err != nil {
		log.Errorf("getting chain head: %s", err)
		return cid.Undef, nil
	}

	sn := s.SectorNumber

	b.lk.Lock()
	b.deadlines[sn] = getSectorDeadline(curEpoch, s)
	b.todo[sn] = in

	sent := make(chan cid.Cid, 1)
	b.waiting[sn] = append(b.waiting[sn], sent)

	select {
	case b.notify <- struct{}{}:
	default: // already have a pending notification, don't need more
	}
	b.lk.Unlock()

	select {
	case c := <-sent:
		return c, nil
	case <-ctx.Done():
		return cid.Undef, ctx.Err()
	}
}

func (b *PreCommitBatcher) Flush(ctx context.Context) (*cid.Cid, error) {
	resCh := make(chan *cid.Cid, 1)
	select {
	case b.force <- resCh:
		select {
		case res := <-resCh:
			return res, nil
		case <-ctx.Done():
			return nil, ctx.Err()
		}
	case <-ctx.Done():
		return nil, ctx.Err()
	}
}

func (b *PreCommitBatcher) Pending(ctx context.Context) ([]abi.SectorID, error) {
	b.lk.Lock()
	defer b.lk.Unlock()

	mid, err := address.IDFromAddress(b.maddr)
	if err != nil {
		return nil, err
	}

	res := make([]abi.SectorID, 0)
	for _, s := range b.todo {
		res = append(res, abi.SectorID{
			Miner:  abi.ActorID(mid),
			Number: s.SectorNumber,
		})
	}

	sort.Slice(res, func(i, j int) bool {
		if res[i].Miner != res[j].Miner {
			return res[i].Miner < res[j].Miner
		}

		return res[i].Number < res[j].Number
	})

	return res, nil
}

func (b *PreCommitBatcher) Stop(ctx context.Context) error {
	close(b.stop)

	select {
	case <-b.stopped:
		return nil
	case <-ctx.Done():
		return ctx.Err()
	}
}