package evm

import (
	"context"
	"math/big"

	"git.lehouerou.net/laurent/evm/contracts"
	"github.com/ethereum/go-ethereum/accounts/abi/bind"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/pkg/errors"
	"github.com/shopspring/decimal"
)

type Token interface {
	Address() common.Address
	Name() string
	Symbol() string
	Decimals() uint8
	TotalSupply() (decimal.Decimal, error)
	BalanceOf(common.Address) (decimal.Decimal, error)
	Balance() (decimal.Decimal, error)
	Allowance(owner common.Address, spender common.Address) (decimal.Decimal, error)
	Approve(ctx context.Context, spender common.Address, value decimal.Decimal, opts ...ExecutionOption) (Transaction, error)
	Transfer(ctx context.Context, to common.Address, value decimal.Decimal, opts ...ExecutionOption) (Transaction, error)

	ValueToBigInt(value decimal.Decimal) *big.Int
	ValueFromBigInt(value *big.Int) decimal.Decimal
}

type baseToken struct {
	client   Client
	contract *contracts.Token

	address  common.Address
	name     string
	symbol   string
	decimals uint8
}

func NewToken(client Client, address common.Address) (Token, error) {
	contract, err := contracts.NewToken(address, client)
	if err != nil {
		return nil, errors.WithStack(err)
	}
	name, err := contract.Name(&bind.CallOpts{})
	if err != nil {
		return nil, errors.WithStack(err)
	}
	symbol, err := contract.Symbol(&bind.CallOpts{})
	if err != nil {
		return nil, errors.WithStack(err)
	}
	decimals, err := contract.Decimals(&bind.CallOpts{})
	if err != nil {
		return nil, errors.WithStack(err)
	}
	return &baseToken{
		address:  address,
		name:     name,
		symbol:   symbol,
		decimals: decimals,
		client:   client,
		contract: contract,
	}, nil
}

func (t *baseToken) TotalSupply() (decimal.Decimal, error) {
	s, err := t.contract.TotalSupply(&bind.CallOpts{})
	if err != nil {
		return decimal.Zero, errors.Wrap(err, "calling contract")
	}
	return t.ValueFromBigInt(s), nil
}

func (t *baseToken) BalanceOf(address common.Address) (decimal.Decimal, error) {
	b, err := t.contract.BalanceOf(&bind.CallOpts{}, address)
	if err != nil {
		return decimal.Zero, errors.Wrap(err, "getting balance from contract")
	}
	return t.ValueFromBigInt(b), nil
}

func (t *baseToken) Allowance(owner common.Address, spender common.Address) (decimal.Decimal, error) {
	a, err := t.contract.Allowance(&bind.CallOpts{}, owner, spender)
	if err != nil {
		return decimal.Zero, errors.Wrap(err, "calling contract")
	}
	return t.ValueFromBigInt(a), nil
}

func (t *baseToken) Approve(ctx context.Context, spender common.Address, value decimal.Decimal, opts ...ExecutionOption) (Transaction, error) {
	return t.client.Execute(ctx, func(ctx context.Context, options *TransactOpts) (*types.Transaction, error) {
		return t.contract.Approve(options.TransactOpts, spender, t.ValueToBigInt(value))
	}, opts...)
}

func (t *baseToken) Transfer(ctx context.Context, to common.Address, value decimal.Decimal, opts ...ExecutionOption) (Transaction, error) {
	return t.client.Execute(ctx, func(ctx context.Context, options *TransactOpts) (*types.Transaction, error) {
		return t.contract.Transfer(options.TransactOpts, to, t.ValueToBigInt(value))
	}, opts...)
}

func (t *baseToken) Address() common.Address {
	return t.address
}

func (t *baseToken) Name() string {
	return t.name
}

func (t *baseToken) Symbol() string {
	return t.symbol
}

func (t *baseToken) Decimals() uint8 {
	return t.decimals
}

func (t *baseToken) DecimalsAsInt32() int32 {
	return int32(t.decimals)
}

func (t *baseToken) ValueFromBigInt(val *big.Int) decimal.Decimal {
	return decimal.NewFromBigInt(val, -t.DecimalsAsInt32())
}

func (t *baseToken) ValueToBigInt(val decimal.Decimal) *big.Int {
	return val.Shift(t.DecimalsAsInt32()).BigInt()
}

func (t *baseToken) Balance() (decimal.Decimal, error) {
	return t.BalanceOf(t.client.PublicAddress())
}