package rpc

import (
	"context"
	"errors"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethdb"
	"github.com/harmony-one/harmony/core"
	"github.com/harmony-one/harmony/core/state"
	"github.com/harmony-one/harmony/core/types"
)

// HmyAPIBackend ...
type HmyAPIBackend struct {
	blockchain *core.BlockChain
	txPool     *core.TxPool
}

// NewBackend ...
func NewBackend(blockchain *core.BlockChain, txPool *core.TxPool) *HmyAPIBackend {
	return &HmyAPIBackend{blockchain, txPool}
}

// ChainDb ...
func (b *HmyAPIBackend) ChainDb() ethdb.Database {
	return b.blockchain.ChainDb()
}

// GetBlock ...
func (b *HmyAPIBackend) GetBlock(ctx context.Context, hash common.Hash) (*types.Block, error) {
	return b.blockchain.GetBlockByHash(hash), nil
}

// GetPoolTransaction ...
func (b *HmyAPIBackend) GetPoolTransaction(hash common.Hash) *types.Transaction {
	return b.txPool.Get(hash)
}

// BlockByNumber ...
func (b *HmyAPIBackend) BlockByNumber(ctx context.Context, blockNr BlockNumber) (*types.Block, error) {
	// Pending block is only known by the miner
	if blockNr == PendingBlockNumber {
		return nil, errors.New("not implemented")
	}
	// Otherwise resolve and return the block
	if blockNr == latestBlockNumber {
		return b.blockchain.CurrentBlock(), nil
	}
	return b.blockchain.GetBlockByNumber(uint64(blockNr)), nil
}

// StateAndHeaderByNumber ...
func (b *HmyAPIBackend) StateAndHeaderByNumber(ctx context.Context, blockNr BlockNumber) (*state.DB, *types.Header, error) {
	// Pending state is only known by the miner
	if blockNr == PendingBlockNumber {
		return nil, nil, errors.New("not implemented")
	}
	// Otherwise resolve the block number and return its state
	header, err := b.HeaderByNumber(ctx, blockNr)
	if header == nil || err != nil {
		return nil, nil, err
	}
	stateDb, err := b.blockchain.StateAt(header.Root)
	return stateDb, header, err
}

// HeaderByNumber ...
func (b *HmyAPIBackend) HeaderByNumber(ctx context.Context, blockNr BlockNumber) (*types.Header, error) {
	// Pending block is only known by the miner
	if blockNr == PendingBlockNumber {
		return nil, errors.New("not implemented")
	}
	// Otherwise resolve and return the block
	if blockNr == latestBlockNumber {
		return b.blockchain.CurrentBlock().Header(), nil
	}
	return b.blockchain.GetHeaderByNumber(uint64(blockNr)), nil
}

// GetPoolNonce ...
func (b *HmyAPIBackend) GetPoolNonce(ctx context.Context, addr common.Address) (uint64, error) {
	return b.txPool.State().GetNonce(addr), nil
}