// Copyright (C) 2019-2025, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.

package interfaces

import (
	"context"
	"errors"
	"math/big"

	"github.com/ava-labs/libevm/common"
	"github.com/ava-labs/libevm/core/types"

	ethereum "github.com/ava-labs/libevm"
)

// ErrNotFound is returned by API methods if the requested item does not exist.
var ErrNotFound = errors.New("not found")

// Subscription represents an event subscription where events are
// delivered on a data channel.
type Subscription interface {
	// Unsubscribe cancels the sending of events to the data channel
	// and closes the error channel.
	Unsubscribe()
	// Err returns the subscription error channel. The error channel receives
	// a value if there is an issue with the subscription (e.g. the network connection
	// delivering the events has been closed). Only one value will ever be sent.
	// The error channel is closed by Unsubscribe.
	Err() <-chan error
}

// ChainReader provides access to the blockchain. The methods in this interface access raw
// data from either the canonical chain (when requesting by block number) or any
// blockchain fork that was previously downloaded and processed by the node. The block
// number argument can be nil to select the latest canonical block. Reading block headers
// should be preferred over full blocks whenever possible.
//
// The returned error is NotFound if the requested item does not exist.
type ChainReader interface {
	BlockByHash(ctx context.Context, hash common.Hash) (*types.Block, error)
	BlockByNumber(ctx context.Context, number *big.Int) (*types.Block, error)
	HeaderByHash(ctx context.Context, hash common.Hash) (*types.Header, error)
	HeaderByNumber(ctx context.Context, number *big.Int) (*types.Header, error)
	TransactionCount(ctx context.Context, blockHash common.Hash) (uint, error)
	TransactionInBlock(ctx context.Context, blockHash common.Hash, index uint) (*types.Transaction, error)

	// This method subscribes to notifications about changes of the head block of
	// the canonical chain.
	SubscribeNewHead(ctx context.Context, ch chan<- *types.Header) (Subscription, error)
}

// TransactionReader provides access to past transactions and their receipts.
// Implementations may impose arbitrary restrictions on the transactions and receipts that
// can be retrieved. Historic transactions may not be available.
//
// Avoid relying on this interface if possible. Contract logs (through the LogFilterer
// interface) are more reliable and usually safer in the presence of chain
// reorganisations.
//
// The returned error is NotFound if the requested item does not exist.
type TransactionReader interface {
	// TransactionByHash checks the pool of pending transactions in addition to the
	// blockchain. The isPending return value indicates whether the transaction has been
	// mined yet. Note that the transaction may not be part of the canonical chain even if
	// it's not pending.
	TransactionByHash(ctx context.Context, txHash common.Hash) (tx *types.Transaction, isPending bool, err error)
	// TransactionReceipt returns the receipt of a mined transaction. Note that the
	// transaction may not be included in the current canonical chain even if a receipt
	// exists.
	TransactionReceipt(ctx context.Context, txHash common.Hash) (*types.Receipt, error)
}

// ChainStateReader wraps access to the state trie of the canonical blockchain. Note that
// implementations of the interface may be unable to return state values for old blocks.
// In many cases, using CallContract can be preferable to reading raw contract storage.
type ChainStateReader interface {
	BalanceAt(ctx context.Context, account common.Address, blockNumber *big.Int) (*big.Int, error)
	StorageAt(ctx context.Context, account common.Address, key common.Hash, blockNumber *big.Int) ([]byte, error)
	CodeAt(ctx context.Context, account common.Address, blockNumber *big.Int) ([]byte, error)
	NonceAt(ctx context.Context, account common.Address, blockNumber *big.Int) (uint64, error)
}

// SyncProgress gives progress indications when the node is synchronising with
// the Ethereum network.
type SyncProgress = ethereum.SyncProgress

// CallMsg contains parameters for contract calls.
type CallMsg struct {
	From      common.Address  // the sender of the 'transaction'
	To        *common.Address // the destination contract (nil for contract creation)
	Gas       uint64          // if 0, the call executes with near-infinite gas
	GasPrice  *big.Int        // wei <-> gas exchange ratio
	GasFeeCap *big.Int        // EIP-1559 fee cap per gas.
	GasTipCap *big.Int        // EIP-1559 tip per gas.
	Value     *big.Int        // amount of wei sent along with the call
	Data      []byte          // input data, usually an ABI-encoded contract method invocation

	AccessList types.AccessList // EIP-2930 access list.

	// For BlobTxType
	BlobGasFeeCap *big.Int
	BlobHashes    []common.Hash
}

// A ContractCaller provides contract calls, essentially transactions that are executed by
// the EVM but not mined into the blockchain. ContractCall is a low-level method to
// execute such calls. For applications which are structured around specific contracts,
// the abigen tool provides a nicer, properly typed way to perform calls.
type ContractCaller interface {
	CallContract(ctx context.Context, call CallMsg, blockNumber *big.Int) ([]byte, error)
}

// FilterQuery contains options for contract log filtering.
type FilterQuery struct {
	BlockHash *common.Hash     // used by eth_getLogs, return logs only from block with this hash
	FromBlock *big.Int         // beginning of the queried range, nil means genesis block
	ToBlock   *big.Int         // end of the range, nil means latest block
	Addresses []common.Address // restricts matches to events created by specific contracts

	// The Topic list restricts matches to particular event topics. Each event has a list
	// of topics. Topics matches a prefix of that list. An empty element slice matches any
	// topic. Non-empty elements represent an alternative that matches any of the
	// contained topics.
	//
	// Examples:
	// {} or nil          matches any topic list
	// {{A}}              matches topic A in first position
	// {{}, {B}}          matches any topic in first position AND B in second position
	// {{A}, {B}}         matches topic A in first position AND B in second position
	// {{A, B}, {C, D}}   matches topic (A OR B) in first position AND (C OR D) in second position
	Topics [][]common.Hash
}

// LogFilterer provides access to contract log events using a one-off query or continuous
// event subscription.
//
// Logs received through a streaming query subscription may have Removed set to true,
// indicating that the log was reverted due to a chain reorganisation.
type LogFilterer interface {
	FilterLogs(ctx context.Context, q FilterQuery) ([]types.Log, error)
	SubscribeFilterLogs(ctx context.Context, q FilterQuery, ch chan<- types.Log) (Subscription, error)
}

// TransactionSender wraps transaction sending. The SendTransaction method injects a
// signed transaction into the pending transaction pool for execution. If the transaction
// was a contract creation, the TransactionReceipt method can be used to retrieve the
// contract address after the transaction has been mined.
//
// The transaction must be signed and have a valid nonce to be included. Consumers of the
// API can use package accounts to maintain local private keys and need can retrieve the
// next available nonce using AcceptedNonceAt.
type TransactionSender interface {
	SendTransaction(ctx context.Context, tx *types.Transaction) error
}

// GasPricer wraps the gas price oracle, which monitors the blockchain to determine the
// optimal gas price given current fee market conditions.
type GasPricer interface {
	SuggestGasPrice(ctx context.Context) (*big.Int, error)
}

// GasPricer1559 provides access to the EIP-1559 gas price oracle.
type GasPricer1559 interface {
	SuggestGasTipCap(ctx context.Context) (*big.Int, error)
}

// FeeHistoryReader provides access to the fee history oracle.
type FeeHistoryReader interface {
	FeeHistory(ctx context.Context, blockCount uint64, lastBlock *big.Int, rewardPercentiles []float64) (*FeeHistory, error)
}

// FeeHistory provides recent fee market data that consumers can use to determine
// a reasonable maxPriorityFeePerGas value.
type FeeHistory struct {
	OldestBlock  *big.Int     // block corresponding to first response value
	Reward       [][]*big.Int // list every txs priority fee per block
	BaseFee      []*big.Int   // list of each block's base fee
	GasUsedRatio []float64    // ratio of gas used out of the total available limit
}

// An AcceptedStateReceiver provides access to the accepted state ie. the state of the
// most recently accepted block.
type AcceptedStateReader interface {
	AcceptedCodeAt(ctx context.Context, account common.Address) ([]byte, error)
	AcceptedNonceAt(ctx context.Context, account common.Address) (uint64, error)
}

// AcceptedContractCaller can be used to perform calls against the accepted state.
type AcceptedContractCaller interface {
	AcceptedCallContract(ctx context.Context, call ethereum.CallMsg) ([]byte, error)
}
