package actions

import (
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/consensus/misc"
	"github.com/ethereum/go-ethereum/core"
	"github.com/ethereum/go-ethereum/core/state"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/log"
	"github.com/ethereum/go-ethereum/trie"
)

// L1Miner wraps a L1Replica with instrumented block building ability.
type L1Miner struct {
	L1Replica

	// L1 block building preferences
	prefCoinbase common.Address

	// L1 block building data
	l1BuildingHeader *types.Header             // block header that we add txs to for block building
	l1BuildingState  *state.StateDB            // state used for block building
	l1GasPool        *core.GasPool             // track gas used of ongoing building
	pendingIndices   map[common.Address]uint64 // per account, how many txs from the pool were already included in the block, since the pool is lagging behind block mining.
	l1Transactions   []*types.Transaction      // collects txs that were successfully included into current block build
	l1Receipts       []*types.Receipt          // collect receipts of ongoing building
	l1Building       bool
	l1TxFailed       []*types.Transaction // log of failed transactions which could not be included
}

// NewL1Miner creates a new L1Replica that can also build blocks.
func NewL1Miner(t Testing, log log.Logger, genesis *core.Genesis) *L1Miner {
	rep := NewL1Replica(t, log, genesis)
	return &L1Miner{
		L1Replica: *rep,
	}
}

// ActL1StartBlock returns an action to build a new L1 block on top of the head block,
// with timeDelta added to the head block time.
func (s *L1Miner) ActL1StartBlock(timeDelta uint64) Action {
	return func(t Testing) {
		if s.l1Building {
			t.InvalidAction("not valid if we already started building a block")
		}
		if timeDelta == 0 {
			t.Fatalf("invalid time delta: %d", timeDelta)
		}

		parent := s.l1Chain.CurrentHeader()
		parentHash := parent.Hash()
		statedb, err := state.New(parent.Root, state.NewDatabase(s.l1Database), nil)
		if err != nil {
			t.Fatalf("failed to init state db around block %s (state %s): %w", parentHash, parent.Root, err)
		}
		header := &types.Header{
			ParentHash: parentHash,
			Coinbase:   s.prefCoinbase,
			Difficulty: common.Big0,
			Number:     new(big.Int).Add(parent.Number, common.Big1),
			GasLimit:   parent.GasLimit,
			Time:       parent.Time + timeDelta,
			Extra:      []byte("L1 was here"),
			MixDigest:  common.Hash{}, // TODO: maybe randomize this (prev-randao value)
		}
		if s.l1Cfg.Config.IsLondon(header.Number) {
			header.BaseFee = misc.CalcBaseFee(s.l1Cfg.Config, parent)
			// At the transition, double the gas limit so the gas target is equal to the old gas limit.
			if !s.l1Cfg.Config.IsLondon(parent.Number) {
				header.GasLimit = parent.GasLimit * s.l1Cfg.Config.ElasticityMultiplier()
			}
		}

		s.l1Building = true
		s.l1BuildingHeader = header
		s.l1BuildingState = statedb
		s.l1Receipts = make([]*types.Receipt, 0)
		s.l1Transactions = make([]*types.Transaction, 0)
		s.pendingIndices = make(map[common.Address]uint64)

		s.l1GasPool = new(core.GasPool).AddGas(header.GasLimit)
	}
}

// ActL1IncludeTx includes the next tx from L1 tx pool from the given account
func (s *L1Miner) ActL1IncludeTx(from common.Address) Action {
	return func(t Testing) {
		if !s.l1Building {
			t.InvalidAction("no tx inclusion when not building l1 block")
			return
		}
		i := s.pendingIndices[from]
		txs, q := s.eth.TxPool().ContentFrom(from)
		if uint64(len(txs)) <= i {
			t.Fatalf("no pending txs from %s, and have %d unprocessable queued txs from this account", from, len(q))
		}
		tx := txs[i]
		if tx.Gas() > s.l1BuildingHeader.GasLimit {
			t.Fatalf("tx consumes %d gas, more than available in L1 block %d", tx.Gas(), s.l1BuildingHeader.GasLimit)
		}
		if tx.Gas() > uint64(*s.l1GasPool) {
			t.InvalidAction("action takes too much gas: %d, only have %d", tx.Gas(), uint64(*s.l1GasPool))
			return
		}
		s.pendingIndices[from] = i + 1 // won't retry the tx
		s.l1BuildingState.Prepare(tx.Hash(), len(s.l1Transactions))
		receipt, err := core.ApplyTransaction(s.l1Cfg.Config, s.l1Chain, &s.l1BuildingHeader.Coinbase,
			s.l1GasPool, s.l1BuildingState, s.l1BuildingHeader, tx, &s.l1BuildingHeader.GasUsed, *s.l1Chain.GetVMConfig())
		if err != nil {
			s.l1TxFailed = append(s.l1TxFailed, tx)
			t.Fatalf("failed to apply transaction to L1 block (tx %d): %w", len(s.l1Transactions), err)
		}
		s.l1Receipts = append(s.l1Receipts, receipt)
		s.l1Transactions = append(s.l1Transactions, tx)
	}
}

func (s *L1Miner) ActL1SetFeeRecipient(coinbase common.Address) {
	s.prefCoinbase = coinbase
	if s.l1Building {
		s.l1BuildingHeader.Coinbase = coinbase
	}
}

// ActL1EndBlock finishes the new L1 block, and applies it to the chain as unsafe block
func (s *L1Miner) ActL1EndBlock(t Testing) {
	if !s.l1Building {
		t.InvalidAction("cannot end L1 block when not building block")
		return
	}

	s.l1Building = false
	s.l1BuildingHeader.GasUsed = s.l1BuildingHeader.GasLimit - uint64(*s.l1GasPool)
	s.l1BuildingHeader.Root = s.l1BuildingState.IntermediateRoot(s.l1Cfg.Config.IsEIP158(s.l1BuildingHeader.Number))
	block := types.NewBlock(s.l1BuildingHeader, s.l1Transactions, nil, s.l1Receipts, trie.NewStackTrie(nil))

	// Write state changes to db
	root, err := s.l1BuildingState.Commit(s.l1Cfg.Config.IsEIP158(s.l1BuildingHeader.Number))
	if err != nil {
		t.Fatalf("l1 state write error: %v", err)
	}
	if err := s.l1BuildingState.Database().TrieDB().Commit(root, false, nil); err != nil {
		t.Fatalf("l1 trie write error: %v", err)
	}

	_, err = s.l1Chain.InsertChain(types.Blocks{block})
	if err != nil {
		t.Fatalf("failed to insert block into l1 chain")
	}
}

func (s *L1Miner) ActEmptyBlock(t Testing) {
	s.ActL1StartBlock(12)(t)
	s.ActL1EndBlock(t)
}

func (s *L1Miner) Close() error {
	return s.L1Replica.Close()
}
