package keeper

import (
	"fmt"

	sdk "github.com/cosmos/cosmos-sdk/types"
	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
	"github.com/cosmos/cosmos-sdk/x/ibc/02-client/exported"
	"github.com/cosmos/cosmos-sdk/x/ibc/02-client/types"
	tendermint "github.com/cosmos/cosmos-sdk/x/ibc/07-tendermint"
	ibctmtypes "github.com/cosmos/cosmos-sdk/x/ibc/07-tendermint/types"
	localhosttypes "github.com/cosmos/cosmos-sdk/x/ibc/09-localhost/types"
)

// CreateClient creates a new client state and populates it with a given consensus
// state as defined in https://github.com/cosmos/ics/tree/master/spec/ics-002-client-semantics#create
//
// CONTRACT: ClientState was constructed correctly from given initial consensusState
func (k Keeper) CreateClient(
	ctx sdk.Context, clientID string, clientState exported.ClientState, consensusState exported.ConsensusState,
) (exported.ClientState, error) {
	_, found := k.GetClientState(ctx, clientID)
	if found {
		return nil, sdkerrors.Wrapf(types.ErrClientExists, "cannot create client with ID %s", clientID)
	}

	_, found = k.GetClientType(ctx, clientID)
	if found {
		panic(fmt.Sprintf("client type is already defined for client %s", clientID))
	}

	if consensusState != nil {
		k.SetClientConsensusState(ctx, clientID, consensusState.GetHeight(), consensusState)
	}

	k.SetClientState(ctx, clientID, clientState)
	k.SetClientType(ctx, clientID, clientState.ClientType())
	k.Logger(ctx).Info(fmt.Sprintf("client %s created at height %d", clientID, clientState.GetLatestHeight()))

	return clientState, nil
}

// UpdateClient updates the consensus state and the state root from a provided header
func (k Keeper) UpdateClient(ctx sdk.Context, clientID string, header exported.Header) (exported.ClientState, error) {
	clientType, found := k.GetClientType(ctx, clientID)
	if !found {
		return nil, sdkerrors.Wrapf(types.ErrClientTypeNotFound, "cannot update client with ID %s", clientID)
	}

	// check that the header consensus matches the client one
	// NOTE: not checked for localhost client
	if header != nil && clientType != exported.Localhost && header.ClientType() != clientType {
		return nil, sdkerrors.Wrapf(types.ErrInvalidHeader, "header client type (%s) does not match expected client type (%s) for client with ID %s", header.ClientType(), clientType, clientID)
	}

	clientState, found := k.GetClientState(ctx, clientID)
	if !found {
		return nil, sdkerrors.Wrapf(types.ErrClientNotFound, "cannot update client with ID %s", clientID)
	}

	// prevent update if the client is frozen before or at header height
	if clientState.IsFrozen() && clientState.GetFrozenHeight() <= header.GetHeight() {
		return nil, sdkerrors.Wrapf(types.ErrClientFrozen, "cannot update client with ID %s", clientID)
	}

	var (
		consensusState  exported.ConsensusState
		consensusHeight uint64
		err             error
	)

	switch clientType {
	case exported.Tendermint:
		tmHeader, ok := header.(ibctmtypes.Header)
		if !ok {
			err = sdkerrors.Wrapf(types.ErrInvalidHeader, "expected tendermint header: %T, got header type: %T", ibctmtypes.Header{}, header)
			break
		}
		// Get the consensus state at the trusted height of header
		trustedConsState, found := k.GetClientConsensusState(ctx, clientID, tmHeader.TrustedHeight)
		if !found {
			return nil, sdkerrors.Wrapf(types.ErrConsensusStateNotFound, "could not find consensus state for trusted header height: %d to verify header against for clientID: %s", tmHeader.TrustedHeight, clientID)
		}
		clientState, consensusState, err = tendermint.CheckValidityAndUpdateState(
			clientState, trustedConsState, header, ctx.BlockTime(),
		)
		if err != nil {
			err = sdkerrors.Wrapf(err, "failed to update client using trusted consensus state height %d", trustedConsState.GetHeight())
		}
	case exported.Localhost:
		// override client state and update the block height
		clientState = localhosttypes.NewClientState(
			ctx.ChainID(), // use the chain ID from context since the client is from the running chain (i.e self).
			ctx.BlockHeight(),
		)
		consensusHeight = uint64(ctx.BlockHeight())
	default:
		err = types.ErrInvalidClientType
	}

	if err != nil {
		return nil, sdkerrors.Wrapf(err, "cannot update client with ID %s", clientID)
	}

	k.SetClientState(ctx, clientID, clientState)

	// we don't set consensus state for localhost client
	if header != nil && clientType != exported.Localhost {
		k.SetClientConsensusState(ctx, clientID, header.GetHeight(), consensusState)
		consensusHeight = consensusState.GetHeight()
	}

	k.Logger(ctx).Info(fmt.Sprintf("client %s updated to height %d", clientID, clientState.GetLatestHeight()))

	// emitting events in the keeper emits for both begin block and handler client updates
	ctx.EventManager().EmitEvent(
		sdk.NewEvent(
			types.EventTypeUpdateClient,
			sdk.NewAttribute(types.AttributeKeyClientID, clientID),
			sdk.NewAttribute(types.AttributeKeyClientType, clientType.String()),
			sdk.NewAttribute(types.AttributeKeyConsensusHeight, fmt.Sprintf("%d", consensusHeight)),
		),
	)

	return clientState, nil
}

// CheckMisbehaviourAndUpdateState checks for client misbehaviour and freezes the
// client if so.
func (k Keeper) CheckMisbehaviourAndUpdateState(ctx sdk.Context, misbehaviour exported.Misbehaviour) error {
	clientState, found := k.GetClientState(ctx, misbehaviour.GetClientID())
	if !found {
		return sdkerrors.Wrapf(types.ErrClientNotFound, "cannot check misbehaviour for client with ID %s", misbehaviour.GetClientID())
	}

	var err error
	switch e := misbehaviour.(type) {
	case ibctmtypes.Evidence:
		// Get ConsensusState at TrustedHeight
		consensusState, found := k.GetClientConsensusState(ctx, misbehaviour.GetClientID(), e.Header1.TrustedHeight)
		if !found {
			return sdkerrors.Wrapf(types.ErrConsensusStateNotFound, "cannot check misbehaviour for client with ID %s", misbehaviour.GetClientID())
		}

		clientState, err = tendermint.CheckMisbehaviourAndUpdateState(
			clientState, consensusState, misbehaviour, consensusState.GetHeight(), ctx.BlockTime(), ctx.ConsensusParams(),
		)

	default:
		err = sdkerrors.Wrapf(sdkerrors.ErrUnknownRequest, "unrecognized IBC client evidence type: %T", e)
	}

	if err != nil {
		return err
	}

	k.SetClientState(ctx, misbehaviour.GetClientID(), clientState)
	k.Logger(ctx).Info(fmt.Sprintf("client %s frozen due to misbehaviour", misbehaviour.GetClientID()))

	return nil
}