package gateway

import (
	"context"
	"fmt"
	"time"

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

	"github.com/filecoin-project/go-address"
	"github.com/filecoin-project/go-bitfield"
	"github.com/filecoin-project/go-state-types/abi"
	"github.com/filecoin-project/go-state-types/crypto"
	"github.com/filecoin-project/go-state-types/dline"
	"github.com/filecoin-project/go-state-types/network"
	"github.com/filecoin-project/lotus/api"
	"github.com/filecoin-project/lotus/build"
	"github.com/filecoin-project/lotus/chain/actors/builtin/miner"
	"github.com/filecoin-project/lotus/chain/types"
	"github.com/filecoin-project/lotus/lib/sigs"
	_ "github.com/filecoin-project/lotus/lib/sigs/bls"
	_ "github.com/filecoin-project/lotus/lib/sigs/secp"
	"github.com/filecoin-project/lotus/node/impl/full"
)

const (
	DefaultLookbackCap            = time.Hour * 24
	DefaultStateWaitLookbackLimit = abi.ChainEpoch(20)
)

// TargetAPI defines the API methods that the Node depends on
// (to make it easy to mock for tests)
type TargetAPI interface {
	Version(context.Context) (api.APIVersion, error)
	ChainGetBlockMessages(context.Context, cid.Cid) (*api.BlockMessages, error)
	ChainGetMessage(ctx context.Context, mc cid.Cid) (*types.Message, error)
	ChainGetNode(ctx context.Context, p string) (*api.IpldObject, error)
	ChainGetTipSet(ctx context.Context, tsk types.TipSetKey) (*types.TipSet, error)
	ChainGetTipSetByHeight(ctx context.Context, h abi.ChainEpoch, tsk types.TipSetKey) (*types.TipSet, error)
	ChainGetTipSetAfterHeight(ctx context.Context, h abi.ChainEpoch, tsk types.TipSetKey) (*types.TipSet, error)
	ChainHasObj(context.Context, cid.Cid) (bool, error)
	ChainHead(ctx context.Context) (*types.TipSet, error)
	ChainNotify(context.Context) (<-chan []*api.HeadChange, error)
	ChainGetPath(ctx context.Context, from, to types.TipSetKey) ([]*api.HeadChange, error)
	ChainReadObj(context.Context, cid.Cid) ([]byte, error)
	GasEstimateMessageGas(ctx context.Context, msg *types.Message, spec *api.MessageSendSpec, tsk types.TipSetKey) (*types.Message, error)
	MpoolPushUntrusted(ctx context.Context, sm *types.SignedMessage) (cid.Cid, error)
	MsigGetAvailableBalance(ctx context.Context, addr address.Address, tsk types.TipSetKey) (types.BigInt, error)
	MsigGetVested(ctx context.Context, addr address.Address, start types.TipSetKey, end types.TipSetKey) (types.BigInt, error)
	MsigGetPending(ctx context.Context, addr address.Address, ts types.TipSetKey) ([]*api.MsigTransaction, error)
	StateAccountKey(ctx context.Context, addr address.Address, tsk types.TipSetKey) (address.Address, error)
	StateDealProviderCollateralBounds(ctx context.Context, size abi.PaddedPieceSize, verified bool, tsk types.TipSetKey) (api.DealCollateralBounds, error)
	StateGetActor(ctx context.Context, actor address.Address, ts types.TipSetKey) (*types.Actor, error)
	StateLookupID(ctx context.Context, addr address.Address, tsk types.TipSetKey) (address.Address, error)
	StateListMiners(ctx context.Context, tsk types.TipSetKey) ([]address.Address, error)
	StateMarketBalance(ctx context.Context, addr address.Address, tsk types.TipSetKey) (api.MarketBalance, error)
	StateMarketStorageDeal(ctx context.Context, dealId abi.DealID, tsk types.TipSetKey) (*api.MarketDeal, error)
	StateNetworkVersion(context.Context, types.TipSetKey) (network.Version, error)
	StateSearchMsg(ctx context.Context, from types.TipSetKey, msg cid.Cid, limit abi.ChainEpoch, allowReplaced bool) (*api.MsgLookup, error)
	StateWaitMsg(ctx context.Context, cid cid.Cid, confidence uint64, limit abi.ChainEpoch, allowReplaced bool) (*api.MsgLookup, error)
	StateReadState(ctx context.Context, actor address.Address, tsk types.TipSetKey) (*api.ActorState, error)
	StateMinerPower(context.Context, address.Address, types.TipSetKey) (*api.MinerPower, error)
	StateMinerFaults(context.Context, address.Address, types.TipSetKey) (bitfield.BitField, error)
	StateMinerRecoveries(context.Context, address.Address, types.TipSetKey) (bitfield.BitField, error)
	StateMinerInfo(context.Context, address.Address, types.TipSetKey) (miner.MinerInfo, error)
	StateMinerDeadlines(context.Context, address.Address, types.TipSetKey) ([]api.Deadline, error)
	StateMinerAvailableBalance(context.Context, address.Address, types.TipSetKey) (types.BigInt, error)
	StateMinerProvingDeadline(context.Context, address.Address, types.TipSetKey) (*dline.Info, error)
	StateCirculatingSupply(context.Context, types.TipSetKey) (abi.TokenAmount, error)
	StateSectorGetInfo(ctx context.Context, maddr address.Address, n abi.SectorNumber, tsk types.TipSetKey) (*miner.SectorOnChainInfo, error)
	StateVerifiedClientStatus(ctx context.Context, addr address.Address, tsk types.TipSetKey) (*abi.StoragePower, error)
	StateVMCirculatingSupplyInternal(context.Context, types.TipSetKey) (api.CirculatingSupply, error)
	WalletBalance(context.Context, address.Address) (types.BigInt, error) //perm:read
}

var _ TargetAPI = *new(api.FullNode) // gateway depends on latest

type Node struct {
	target                 TargetAPI
	lookbackCap            time.Duration
	stateWaitLookbackLimit abi.ChainEpoch
	errLookback            error
}

var (
	_ api.Gateway         = (*Node)(nil)
	_ full.ChainModuleAPI = (*Node)(nil)
	_ full.GasModuleAPI   = (*Node)(nil)
	_ full.MpoolModuleAPI = (*Node)(nil)
	_ full.StateModuleAPI = (*Node)(nil)
)

// NewNode creates a new gateway node.
func NewNode(api TargetAPI, lookbackCap time.Duration, stateWaitLookbackLimit abi.ChainEpoch) *Node {
	return &Node{
		target:                 api,
		lookbackCap:            lookbackCap,
		stateWaitLookbackLimit: stateWaitLookbackLimit,
		errLookback:            fmt.Errorf("lookbacks of more than %s are disallowed", lookbackCap),
	}
}

func (gw *Node) checkTipsetKey(ctx context.Context, tsk types.TipSetKey) error {
	if tsk.IsEmpty() {
		return nil
	}

	ts, err := gw.target.ChainGetTipSet(ctx, tsk)
	if err != nil {
		return err
	}

	return gw.checkTipset(ts)
}

func (gw *Node) checkTipset(ts *types.TipSet) error {
	at := time.Unix(int64(ts.Blocks()[0].Timestamp), 0)
	if err := gw.checkTimestamp(at); err != nil {
		return fmt.Errorf("bad tipset: %w", err)
	}
	return nil
}

func (gw *Node) checkTipsetHeight(ts *types.TipSet, h abi.ChainEpoch) error {
	tsBlock := ts.Blocks()[0]
	heightDelta := time.Duration(uint64(tsBlock.Height-h)*build.BlockDelaySecs) * time.Second
	timeAtHeight := time.Unix(int64(tsBlock.Timestamp), 0).Add(-heightDelta)

	if err := gw.checkTimestamp(timeAtHeight); err != nil {
		return fmt.Errorf("bad tipset height: %w", err)
	}
	return nil
}

func (gw *Node) checkTimestamp(at time.Time) error {
	if time.Since(at) > gw.lookbackCap {
		return gw.errLookback
	}
	return nil
}

func (gw *Node) Version(ctx context.Context) (api.APIVersion, error) {
	return gw.target.Version(ctx)
}

func (gw *Node) ChainGetBlockMessages(ctx context.Context, c cid.Cid) (*api.BlockMessages, error) {
	return gw.target.ChainGetBlockMessages(ctx, c)
}

func (gw *Node) ChainHasObj(ctx context.Context, c cid.Cid) (bool, error) {
	return gw.target.ChainHasObj(ctx, c)
}

func (gw *Node) ChainHead(ctx context.Context) (*types.TipSet, error) {
	// TODO: cache and invalidate cache when timestamp is up (or have internal ChainNotify)

	return gw.target.ChainHead(ctx)
}

func (gw *Node) ChainGetMessage(ctx context.Context, mc cid.Cid) (*types.Message, error) {
	return gw.target.ChainGetMessage(ctx, mc)
}

func (gw *Node) ChainGetTipSet(ctx context.Context, tsk types.TipSetKey) (*types.TipSet, error) {
	return gw.target.ChainGetTipSet(ctx, tsk)
}

func (gw *Node) ChainGetTipSetByHeight(ctx context.Context, h abi.ChainEpoch, tsk types.TipSetKey) (*types.TipSet, error) {
	if err := gw.checkTipSetHeight(ctx, h, tsk); err != nil {
		return nil, err
	}

	return gw.target.ChainGetTipSetByHeight(ctx, h, tsk)
}

func (gw *Node) ChainGetTipSetAfterHeight(ctx context.Context, h abi.ChainEpoch, tsk types.TipSetKey) (*types.TipSet, error) {
	if err := gw.checkTipSetHeight(ctx, h, tsk); err != nil {
		return nil, err
	}

	return gw.target.ChainGetTipSetAfterHeight(ctx, h, tsk)
}

func (gw *Node) checkTipSetHeight(ctx context.Context, h abi.ChainEpoch, tsk types.TipSetKey) error {
	var ts *types.TipSet
	if tsk.IsEmpty() {
		head, err := gw.target.ChainHead(ctx)
		if err != nil {
			return err
		}
		ts = head
	} else {
		gts, err := gw.target.ChainGetTipSet(ctx, tsk)
		if err != nil {
			return err
		}
		ts = gts
	}

	// Check if the tipset key refers to gw tipset that's too far in the past
	if err := gw.checkTipset(ts); err != nil {
		return err
	}

	// Check if the height is too far in the past
	if err := gw.checkTipsetHeight(ts, h); err != nil {
		return err
	}

	return nil
}

func (gw *Node) ChainGetNode(ctx context.Context, p string) (*api.IpldObject, error) {
	return gw.target.ChainGetNode(ctx, p)
}

func (gw *Node) ChainNotify(ctx context.Context) (<-chan []*api.HeadChange, error) {
	return gw.target.ChainNotify(ctx)
}

func (gw *Node) ChainGetPath(ctx context.Context, from, to types.TipSetKey) ([]*api.HeadChange, error) {
	if err := gw.checkTipsetKey(ctx, from); err != nil {
		return nil, xerrors.Errorf("gateway: checking 'from' tipset: %w", err)
	}

	if err := gw.checkTipsetKey(ctx, to); err != nil {
		return nil, xerrors.Errorf("gateway: checking 'to' tipset: %w", err)
	}

	return gw.target.ChainGetPath(ctx, from, to)
}

func (gw *Node) ChainReadObj(ctx context.Context, c cid.Cid) ([]byte, error) {
	return gw.target.ChainReadObj(ctx, c)
}

func (gw *Node) GasEstimateMessageGas(ctx context.Context, msg *types.Message, spec *api.MessageSendSpec, tsk types.TipSetKey) (*types.Message, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}

	return gw.target.GasEstimateMessageGas(ctx, msg, spec, tsk)
}

func (gw *Node) MpoolPush(ctx context.Context, sm *types.SignedMessage) (cid.Cid, error) {
	// TODO: additional anti-spam checks
	return gw.target.MpoolPushUntrusted(ctx, sm)
}

func (gw *Node) MsigGetAvailableBalance(ctx context.Context, addr address.Address, tsk types.TipSetKey) (types.BigInt, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return types.NewInt(0), err
	}

	return gw.target.MsigGetAvailableBalance(ctx, addr, tsk)
}

func (gw *Node) MsigGetVested(ctx context.Context, addr address.Address, start types.TipSetKey, end types.TipSetKey) (types.BigInt, error) {
	if err := gw.checkTipsetKey(ctx, start); err != nil {
		return types.NewInt(0), err
	}
	if err := gw.checkTipsetKey(ctx, end); err != nil {
		return types.NewInt(0), err
	}

	return gw.target.MsigGetVested(ctx, addr, start, end)
}

func (gw *Node) MsigGetPending(ctx context.Context, addr address.Address, tsk types.TipSetKey) ([]*api.MsigTransaction, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}

	return gw.target.MsigGetPending(ctx, addr, tsk)
}

func (gw *Node) StateAccountKey(ctx context.Context, addr address.Address, tsk types.TipSetKey) (address.Address, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return address.Undef, err
	}

	return gw.target.StateAccountKey(ctx, addr, tsk)
}

func (gw *Node) StateDealProviderCollateralBounds(ctx context.Context, size abi.PaddedPieceSize, verified bool, tsk types.TipSetKey) (api.DealCollateralBounds, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return api.DealCollateralBounds{}, err
	}

	return gw.target.StateDealProviderCollateralBounds(ctx, size, verified, tsk)
}

func (gw *Node) StateGetActor(ctx context.Context, actor address.Address, tsk types.TipSetKey) (*types.Actor, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}

	return gw.target.StateGetActor(ctx, actor, tsk)
}

func (gw *Node) StateListMiners(ctx context.Context, tsk types.TipSetKey) ([]address.Address, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}

	return gw.target.StateListMiners(ctx, tsk)
}

func (gw *Node) StateLookupID(ctx context.Context, addr address.Address, tsk types.TipSetKey) (address.Address, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return address.Undef, err
	}

	return gw.target.StateLookupID(ctx, addr, tsk)
}

func (gw *Node) StateMarketBalance(ctx context.Context, addr address.Address, tsk types.TipSetKey) (api.MarketBalance, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return api.MarketBalance{}, err
	}

	return gw.target.StateMarketBalance(ctx, addr, tsk)
}

func (gw *Node) StateMarketStorageDeal(ctx context.Context, dealId abi.DealID, tsk types.TipSetKey) (*api.MarketDeal, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}

	return gw.target.StateMarketStorageDeal(ctx, dealId, tsk)
}

func (gw *Node) StateNetworkVersion(ctx context.Context, tsk types.TipSetKey) (network.Version, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return network.VersionMax, err
	}

	return gw.target.StateNetworkVersion(ctx, tsk)
}

func (gw *Node) StateSearchMsg(ctx context.Context, from types.TipSetKey, msg cid.Cid, limit abi.ChainEpoch, allowReplaced bool) (*api.MsgLookup, error) {
	if limit == api.LookbackNoLimit {
		limit = gw.stateWaitLookbackLimit
	}
	if gw.stateWaitLookbackLimit != api.LookbackNoLimit && limit > gw.stateWaitLookbackLimit {
		limit = gw.stateWaitLookbackLimit
	}
	if err := gw.checkTipsetKey(ctx, from); err != nil {
		return nil, err
	}

	return gw.target.StateSearchMsg(ctx, from, msg, limit, allowReplaced)
}

func (gw *Node) StateWaitMsg(ctx context.Context, msg cid.Cid, confidence uint64, limit abi.ChainEpoch, allowReplaced bool) (*api.MsgLookup, error) {
	if limit == api.LookbackNoLimit {
		limit = gw.stateWaitLookbackLimit
	}
	if gw.stateWaitLookbackLimit != api.LookbackNoLimit && limit > gw.stateWaitLookbackLimit {
		limit = gw.stateWaitLookbackLimit
	}

	return gw.target.StateWaitMsg(ctx, msg, confidence, limit, allowReplaced)
}

func (gw *Node) StateReadState(ctx context.Context, actor address.Address, tsk types.TipSetKey) (*api.ActorState, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}
	return gw.target.StateReadState(ctx, actor, tsk)
}

func (gw *Node) StateMinerPower(ctx context.Context, m address.Address, tsk types.TipSetKey) (*api.MinerPower, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}
	return gw.target.StateMinerPower(ctx, m, tsk)
}

func (gw *Node) StateMinerFaults(ctx context.Context, m address.Address, tsk types.TipSetKey) (bitfield.BitField, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return bitfield.BitField{}, err
	}
	return gw.target.StateMinerFaults(ctx, m, tsk)
}
func (gw *Node) StateMinerRecoveries(ctx context.Context, m address.Address, tsk types.TipSetKey) (bitfield.BitField, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return bitfield.BitField{}, err
	}
	return gw.target.StateMinerRecoveries(ctx, m, tsk)
}

func (gw *Node) StateMinerInfo(ctx context.Context, m address.Address, tsk types.TipSetKey) (miner.MinerInfo, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return miner.MinerInfo{}, err
	}
	return gw.target.StateMinerInfo(ctx, m, tsk)
}

func (gw *Node) StateMinerDeadlines(ctx context.Context, m address.Address, tsk types.TipSetKey) ([]api.Deadline, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}
	return gw.target.StateMinerDeadlines(ctx, m, tsk)
}

func (gw *Node) StateMinerAvailableBalance(ctx context.Context, m address.Address, tsk types.TipSetKey) (types.BigInt, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return types.BigInt{}, err
	}
	return gw.target.StateMinerAvailableBalance(ctx, m, tsk)
}

func (gw *Node) StateMinerProvingDeadline(ctx context.Context, m address.Address, tsk types.TipSetKey) (*dline.Info, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}
	return gw.target.StateMinerProvingDeadline(ctx, m, tsk)
}

func (gw *Node) StateCirculatingSupply(ctx context.Context, tsk types.TipSetKey) (abi.TokenAmount, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return types.BigInt{}, err
	}
	return gw.target.StateCirculatingSupply(ctx, tsk)
}

func (gw *Node) StateSectorGetInfo(ctx context.Context, maddr address.Address, n abi.SectorNumber, tsk types.TipSetKey) (*miner.SectorOnChainInfo, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}
	return gw.target.StateSectorGetInfo(ctx, maddr, n, tsk)
}

func (gw *Node) StateVerifiedClientStatus(ctx context.Context, addr address.Address, tsk types.TipSetKey) (*abi.StoragePower, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return nil, err
	}
	return gw.target.StateVerifiedClientStatus(ctx, addr, tsk)
}

func (gw *Node) StateVMCirculatingSupplyInternal(ctx context.Context, tsk types.TipSetKey) (api.CirculatingSupply, error) {
	if err := gw.checkTipsetKey(ctx, tsk); err != nil {
		return api.CirculatingSupply{}, err
	}
	return gw.target.StateVMCirculatingSupplyInternal(ctx, tsk)
}

func (gw *Node) WalletVerify(ctx context.Context, k address.Address, msg []byte, sig *crypto.Signature) (bool, error) {
	return sigs.Verify(sig, k, msg) == nil, nil
}

func (gw *Node) WalletBalance(ctx context.Context, k address.Address) (types.BigInt, error) {
	return gw.target.WalletBalance(ctx, k)
}
