package hmyapi

import (
	"context"
	"fmt"

	"math/big"
	"time"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/ethereum/go-ethereum/common/math"
	"github.com/ethereum/go-ethereum/params"
	"github.com/ethereum/go-ethereum/rpc"
	"github.com/harmony-one/harmony/core"
	"github.com/harmony-one/harmony/core/types"
	"github.com/harmony-one/harmony/core/vm"
	"github.com/harmony-one/harmony/internal/utils"
)

const (
	defaultGasPrice = params.GWei
)

// PublicBlockChainAPI provides an API to access the Harmony blockchain.
// It offers only methods that operate on public data that is freely available to anyone.
type PublicBlockChainAPI struct {
	b Backend
}

// NewPublicBlockChainAPI creates a new Harmony blockchain API.
func NewPublicBlockChainAPI(b Backend) *PublicBlockChainAPI {
	return &PublicBlockChainAPI{b}
}

// GetBlockByNumber returns the requested block. When blockNr is -1 the chain head is returned. When fullTx is true all
// transactions in the block are returned in full detail, otherwise only the transaction hash is returned.
func (s *PublicBlockChainAPI) GetBlockByNumber(ctx context.Context, blockNr rpc.BlockNumber, fullTx bool) (map[string]interface{}, error) {
	block, err := s.b.BlockByNumber(ctx, blockNr)
	if block != nil {
		response, err := RPCMarshalBlock(block, true, fullTx)
		if err == nil && blockNr == rpc.PendingBlockNumber {
			// Pending blocks need to nil out a few fields
			for _, field := range []string{"hash", "nonce", "miner"} {
				response[field] = nil
			}
		}
		return response, err
	}
	return nil, err
}

// GetBlockByHash returns the requested block. When fullTx is true all transactions in the block are returned in full
// detail, otherwise only the transaction hash is returned.
func (s *PublicBlockChainAPI) GetBlockByHash(ctx context.Context, blockHash common.Hash, fullTx bool) (map[string]interface{}, error) {
	block, err := s.b.GetBlock(ctx, blockHash)
	if block != nil {
		return RPCMarshalBlock(block, false, false)
	}
	return nil, err
}

// GetCode returns the code stored at the given address in the state for the given block number.
func (s *PublicBlockChainAPI) GetCode(ctx context.Context, address common.Address, blockNr rpc.BlockNumber) (hexutil.Bytes, error) {
	state, _, err := s.b.StateAndHeaderByNumber(ctx, blockNr)
	if state == nil || err != nil {
		return nil, err
	}
	code := state.GetCode(address)
	return code, state.Error()
}

// GetStorageAt returns the storage from the state at the given address, key and
// block number. The rpc.LatestBlockNumber and rpc.PendingBlockNumber meta block
// numbers are also allowed.
func (s *PublicBlockChainAPI) GetStorageAt(ctx context.Context, address common.Address, key string, blockNr rpc.BlockNumber) (hexutil.Bytes, error) {
	state, _, err := s.b.StateAndHeaderByNumber(ctx, blockNr)
	if state == nil || err != nil {
		return nil, err
	}
	res := state.GetState(address, common.HexToHash(key))
	return res[:], state.Error()
}

// GetBalance returns the amount of Nano for the given address in the state of the
// given block number. The rpc.LatestBlockNumber and rpc.PendingBlockNumber meta
// block numbers are also allowed.
func (s *PublicBlockChainAPI) GetBalance(ctx context.Context, address common.Address, blockNr rpc.BlockNumber) (*hexutil.Big, error) {
	// TODO: currently only get latest balance. Will add complete logic later.
	return s.b.GetBalance(address)
}

// BlockNumber returns the block number of the chain head.
func (s *PublicBlockChainAPI) BlockNumber() hexutil.Uint64 {
	header, _ := s.b.HeaderByNumber(context.Background(), rpc.LatestBlockNumber) // latest header should always be available
	return hexutil.Uint64(header.Number.Uint64())
}

// Call executes the given transaction on the state for the given block number.
// It doesn't make and changes in the state/blockchain and is useful to execute and retrieve values.
func (s *PublicBlockChainAPI) Call(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber) (hexutil.Bytes, error) {
	result, _, _, err := doCall(ctx, s.b, args, blockNr, vm.Config{}, 5*time.Second, s.b.RPCGasCap())
	return (hexutil.Bytes)(result), err
}

func doCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumber, vmCfg vm.Config, timeout time.Duration, globalGasCap *big.Int) ([]byte, uint64, bool, error) {
	defer func(start time.Time) {
		utils.GetLogInstance().Debug("Executing EVM call finished", "runtime", time.Since(start))
	}(time.Now())

	state, header, err := b.StateAndHeaderByNumber(ctx, blockNr)
	if state == nil || err != nil {
		return nil, 0, false, err
	}
	// Set sender address or use a default if none specified
	var addr common.Address
	if args.From == nil {
		// TODO(ricl): this logic was borrowed from [go-ethereum](https://github.com/ethereum/go-ethereum/blob/f578d41ee6b3087f8021fd561a0b5665aea3dba6/internal/ethapi/api.go#L738)
		// [question](https://ethereum.stackexchange.com/questions/72979/why-does-the-docall-function-use-the-first-account-by-default)
		// Might need to reconsider the logic
		if wallets := b.AccountManager().Wallets(); len(wallets) > 0 {
			if accounts := wallets[0].Accounts(); len(accounts) > 0 {
				addr = accounts[0].Address
			}
		}
	} else {
		addr = *args.From
	}
	// Set default gas & gas price if none were set
	gas := uint64(math.MaxUint64 / 2)
	if args.Gas != nil {
		gas = uint64(*args.Gas)
	}
	if globalGasCap != nil && globalGasCap.Uint64() < gas {
		utils.GetLogInstance().Warn("Caller gas above allowance, capping", "requested", gas, "cap", globalGasCap)
		gas = globalGasCap.Uint64()
	}
	gasPrice := new(big.Int).SetUint64(defaultGasPrice)
	if args.GasPrice != nil {
		gasPrice = args.GasPrice.ToInt()
	}

	value := new(big.Int)
	if args.Value != nil {
		value = args.Value.ToInt()
	}

	var data []byte
	if args.Data != nil {
		data = []byte(*args.Data)
	}

	// Create new call message
	msg := types.NewMessage(addr, args.To, 0, value, gas, gasPrice, data, false)

	// Setup context so it may be cancelled the call has completed
	// or, in case of unmetered gas, setup a context with a timeout.
	var cancel context.CancelFunc
	if timeout > 0 {
		ctx, cancel = context.WithTimeout(ctx, timeout)
	} else {
		ctx, cancel = context.WithCancel(ctx)
	}
	// Make sure the context is cancelled when the call has completed
	// this makes sure resources are cleaned up.
	defer cancel()

	// Get a new instance of the EVM.
	evm, vmError, err := b.GetEVM(ctx, msg, state, header)
	if err != nil {
		return nil, 0, false, err
	}
	// Wait for the context to be done and cancel the evm. Even if the
	// EVM has finished, cancelling may be done (repeatedly)
	go func() {
		<-ctx.Done()
		evm.Cancel()
	}()

	// Setup the gas pool (also for unmetered requests)
	// and apply the message.
	gp := new(core.GasPool).AddGas(math.MaxUint64)
	res, gas, failed, err := core.ApplyMessage(evm, msg, gp)
	if err := vmError(); err != nil {
		return nil, 0, false, err
	}
	// If the timer caused an abort, return an appropriate error message
	if evm.Cancelled() {
		return nil, 0, false, fmt.Errorf("execution aborted (timeout = %v)", timeout)
	}
	return res, gas, failed, err
}