package types

import (
	"bytes"
	"fmt"

	"github.com/filecoin-project/lotus/build"
	"github.com/filecoin-project/specs-actors/actors/abi"
	"github.com/filecoin-project/specs-actors/actors/abi/big"
	block "github.com/ipfs/go-block-format"
	"github.com/ipfs/go-cid"
	xerrors "golang.org/x/xerrors"

	"github.com/filecoin-project/go-address"
)

const MessageVersion = 0

type ChainMsg interface {
	Cid() cid.Cid
	VMMessage() *Message
	ToStorageBlock() (block.Block, error)
	// FIXME: This is the *message* length, this name is misleading.
	ChainLength() int
}

type Message struct {
	Version int64

	To   address.Address
	From address.Address

	Nonce uint64

	Value BigInt

	GasPrice BigInt
	GasLimit int64

	Method abi.MethodNum
	Params []byte
}

func (m *Message) Caller() address.Address {
	return m.From
}

func (m *Message) Receiver() address.Address {
	return m.To
}

func (m *Message) ValueReceived() abi.TokenAmount {
	return m.Value
}

func DecodeMessage(b []byte) (*Message, error) {
	var msg Message
	if err := msg.UnmarshalCBOR(bytes.NewReader(b)); err != nil {
		return nil, err
	}

	if msg.Version != MessageVersion {
		return nil, fmt.Errorf("decoded message had incorrect version (%d)", msg.Version)
	}

	return &msg, nil
}

func (m *Message) Serialize() ([]byte, error) {
	buf := new(bytes.Buffer)
	if err := m.MarshalCBOR(buf); err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

func (m *Message) ChainLength() int {
	ser, err := m.Serialize()
	if err != nil {
		panic(err)
	}
	return len(ser)
}

func (m *Message) ToStorageBlock() (block.Block, error) {
	data, err := m.Serialize()
	if err != nil {
		return nil, err
	}

	c, err := abi.CidBuilder.Sum(data)
	if err != nil {
		return nil, err
	}

	return block.NewBlockWithCid(data, c)
}

func (m *Message) Cid() cid.Cid {
	b, err := m.ToStorageBlock()
	if err != nil {
		panic(fmt.Sprintf("failed to marshal message: %s", err)) // I think this is maybe sketchy, what happens if we try to serialize a message with an undefined address in it?
	}

	return b.Cid()
}

func (m *Message) RequiredFunds() BigInt {
	return BigAdd(
		m.Value,
		BigMul(m.GasPrice, NewInt(uint64(m.GasLimit))),
	)
}

func (m *Message) VMMessage() *Message {
	return m
}

func (m *Message) Equals(o *Message) bool {
	return m.Cid() == o.Cid()
}

func (m *Message) ValidForBlockInclusion(minGas int64) error {
	if m.Version != 0 {
		return xerrors.New("'Version' unsupported")
	}

	if m.To == address.Undef {
		return xerrors.New("'To' address cannot be empty")
	}

	if m.From == address.Undef {
		return xerrors.New("'From' address cannot be empty")
	}

	if m.Value.LessThan(big.Zero()) {
		return xerrors.New("'Value' field cannot be negative")
	}

	if m.Value.GreaterThan(TotalFilecoinInt) {
		return xerrors.New("'Value' field cannot be greater than total filecoin supply")
	}

	if m.GasPrice.LessThan(big.Zero()) {
		return xerrors.New("'GasPrice' field cannot be negative")
	}

	if m.GasLimit > build.BlockGasLimit {
		return xerrors.New("'GasLimit' field cannot be greater than a block's gas limit")
	}

	// since prices might vary with time, this is technically semantic validation
	if m.GasLimit < minGas {
		return xerrors.New("'GasLimit' field cannot be less than the cost of storing a message on chain")
	}

	return nil
}

const TestGasLimit = 100e6