ethers.js/src.ts/transaction/transaction.ts

import { getAddress } from "../address/index.js";
import { ZeroAddress } from "../constants/addresses.js";
import { keccak256, Signature, SigningKey } from "../crypto/index.js";
import {
    concat, decodeRlp, encodeRlp, getBytes, getBigInt, getNumber, hexlify,
    assert, assertArgument, isHexString, toBeArray, zeroPadValue
} from "../utils/index.js";

import { accessListify } from "./accesslist.js";
import { recoverAddress } from "./address.js";

import type { BigNumberish, BytesLike } from "../utils/index.js";
import type { SignatureLike } from "../crypto/index.js";

import type { AccessList, AccessListish } from "./index.js";


const BN_0 = BigInt(0);
const BN_2 = BigInt(2);
const BN_27 = BigInt(27)
const BN_28 = BigInt(28)
const BN_35 = BigInt(35);
const BN_MAX_UINT = BigInt("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff");


/**
 *  A **TransactionLike** is an object which is appropriate as a loose
 *  input for many operations which will populate missing properties of
 *  a transaction.
 */
export interface TransactionLike<A = string> {
    /**
     *  The type.
     */
    type?: null | number;

    /**
     *  The recipient address or ``null`` for an ``init`` transaction.
     */
    to?: null | A;

    /**
     *  The sender.
     */
    from?: null | A;

    /**
     *  The nonce.
     */
    nonce?: null | number;

    /**
     *  The maximum amount of gas that can be used.
     */
    gasLimit?: null | BigNumberish;

    /**
     *  The gas price for legacy and berlin transactions.
     */
    gasPrice?: null | BigNumberish;

    /**
     *  The maximum priority fee per gas for london transactions.
     */
    maxPriorityFeePerGas?: null | BigNumberish;

    /**
     *  The maximum total fee per gas for london transactions.
     */
    maxFeePerGas?: null | BigNumberish;

    /**
     *  The data.
     */
    data?: null | string;

    /**
     *  The value (in wei) to send.
     */
    value?: null | BigNumberish;

    /**
     *  The chain ID the transaction is valid on.
     */
    chainId?: null | BigNumberish;

    /**
     *  The transaction hash.
     */
    hash?: null | string;

    /**
     *  The signature provided by the sender.
     */
    signature?: null | SignatureLike;

    /**
     *  The access list for berlin and london transactions.
     */
    accessList?: null | AccessListish;

    /**
     *  The maximum fee per blob gas (see [[link-eip-4844]]).
     */
    maxFeePerBlobGas?: null | BigNumberish;

    /**
     *  The versioned hashes (see [[link-eip-4844]]).
     */
    blobVersionedHashes?: null | Array<string>;
}

function handleAddress(value: string): null | string {
    if (value === "0x") { return null; }
    return getAddress(value);
}

function handleAccessList(value: any, param: string): AccessList {
    try {
        return accessListify(value);
    } catch (error: any) {
        assertArgument(false, error.message, param, value);
    }
}

function handleNumber(_value: string, param: string): number {
    if (_value === "0x") { return 0; }
    return getNumber(_value, param);
}

function handleUint(_value: string, param: string): bigint {
    if (_value === "0x") { return BN_0; }
    const value = getBigInt(_value, param);
    assertArgument(value <= BN_MAX_UINT, "value exceeds uint size", param, value);
    return value;
}

function formatNumber(_value: BigNumberish, name: string): Uint8Array {
    const value = getBigInt(_value, "value");
    const result = toBeArray(value);
    assertArgument(result.length <= 32, `value too large`, `tx.${ name }`, value);
    return result;
}

function formatAccessList(value: AccessListish): Array<[ string, Array<string> ]> {
    return accessListify(value).map((set) => [ set.address, set.storageKeys ]);
}

function formatHashes(value: Array<string>, param: string): Array<string> {
    assertArgument(Array.isArray(value), `invalid ${ param }`, "value", value);
    for (let i = 0; i < value.length; i++) {
        assertArgument(isHexString(value[i], 32), "invalid ${ param } hash", `value[${ i }]`, value[i]);
    }
    return value;
}

function _parseLegacy(data: Uint8Array): TransactionLike {
    const fields: any = decodeRlp(data);

    assertArgument(Array.isArray(fields) && (fields.length === 9 || fields.length === 6),
        "invalid field count for legacy transaction", "data", data);

    const tx: TransactionLike = {
        type:     0,
        nonce:    handleNumber(fields[0], "nonce"),
        gasPrice: handleUint(fields[1], "gasPrice"),
        gasLimit: handleUint(fields[2], "gasLimit"),
        to:       handleAddress(fields[3]),
        value:    handleUint(fields[4], "value"),
        data:     hexlify(fields[5]),
        chainId:  BN_0
    };

    // Legacy unsigned transaction
    if (fields.length === 6) { return tx; }

    const v = handleUint(fields[6], "v");
    const r = handleUint(fields[7], "r");
    const s = handleUint(fields[8], "s");

    if (r === BN_0 && s === BN_0) {
        // EIP-155 unsigned transaction
        tx.chainId = v;

    } else {

        // Compute the EIP-155 chain ID (or 0 for legacy)
        let chainId = (v - BN_35) / BN_2;
        if (chainId < BN_0) { chainId = BN_0; }
        tx.chainId = chainId

        // Signed Legacy Transaction
        assertArgument(chainId !== BN_0 || (v === BN_27 || v === BN_28), "non-canonical legacy v", "v", fields[6]);

        tx.signature = Signature.from({
            r: zeroPadValue(fields[7], 32),
            s: zeroPadValue(fields[8], 32),
            v
        });

        tx.hash = keccak256(data);
    }

    return tx;
}

function _serializeLegacy(tx: Transaction, sig?: Signature): string {
    const fields: Array<any> = [
        formatNumber(tx.nonce, "nonce"),
        formatNumber(tx.gasPrice || 0, "gasPrice"),
        formatNumber(tx.gasLimit, "gasLimit"),
        (tx.to || "0x"),
        formatNumber(tx.value, "value"),
        tx.data,
    ];

    let chainId = BN_0;
    if (tx.chainId != BN_0) {
        // A chainId was provided; if non-zero we'll use EIP-155
        chainId = getBigInt(tx.chainId, "tx.chainId");

        // We have a chainId in the tx and an EIP-155 v in the signature,
        // make sure they agree with each other
        assertArgument(!sig || sig.networkV == null || sig.legacyChainId === chainId,
             "tx.chainId/sig.v mismatch", "sig", sig);

    } else if (tx.signature) {
        // No explicit chainId, but EIP-155 have a derived implicit chainId
        const legacy = tx.signature.legacyChainId;
        if (legacy != null) { chainId = legacy; }
    }

    // Requesting an unsigned transaction
    if (!sig) {
        // We have an EIP-155 transaction (chainId was specified and non-zero)
        if (chainId !== BN_0) {
            fields.push(toBeArray(chainId));
            fields.push("0x");
            fields.push("0x");
        }

        return encodeRlp(fields);
    }

    // @TODO: We should probably check that tx.signature, chainId, and sig
    //        match but that logic could break existing code, so schedule
    //        this for the next major bump.

    // Compute the EIP-155 v
    let v = BigInt(27 + sig.yParity);
    if (chainId !== BN_0) {
        v = Signature.getChainIdV(chainId, sig.v);
    } else if (BigInt(sig.v) !== v) {
        assertArgument(false, "tx.chainId/sig.v mismatch", "sig", sig);
    }

    // Add the signature
    fields.push(toBeArray(v));
    fields.push(toBeArray(sig.r));
    fields.push(toBeArray(sig.s));

    return encodeRlp(fields);
}

function _parseEipSignature(tx: TransactionLike, fields: Array<string>): void {
    let yParity: number;
    try {
        yParity = handleNumber(fields[0], "yParity");
        if (yParity !== 0 && yParity !== 1) { throw new Error("bad yParity"); }
    } catch (error) {
        assertArgument(false, "invalid yParity", "yParity", fields[0]);
    }

    const r = zeroPadValue(fields[1], 32);
    const s = zeroPadValue(fields[2], 32);

    const signature = Signature.from({ r, s, yParity });
    tx.signature = signature;
}

function _parseEip1559(data: Uint8Array): TransactionLike {
    const fields: any = decodeRlp(getBytes(data).slice(1));

    assertArgument(Array.isArray(fields) && (fields.length === 9 || fields.length === 12),
        "invalid field count for transaction type: 2", "data", hexlify(data));

    const tx: TransactionLike = {
        type:                  2,
        chainId:               handleUint(fields[0], "chainId"),
        nonce:                 handleNumber(fields[1], "nonce"),
        maxPriorityFeePerGas:  handleUint(fields[2], "maxPriorityFeePerGas"),
        maxFeePerGas:          handleUint(fields[3], "maxFeePerGas"),
        gasPrice:              null,
        gasLimit:              handleUint(fields[4], "gasLimit"),
        to:                    handleAddress(fields[5]),
        value:                 handleUint(fields[6], "value"),
        data:                  hexlify(fields[7]),
        accessList:            handleAccessList(fields[8], "accessList"),
    };

    // Unsigned EIP-1559 Transaction
    if (fields.length === 9) { return tx; }

    tx.hash = keccak256(data);

    _parseEipSignature(tx, fields.slice(9));

    return tx;
}

function _serializeEip1559(tx: Transaction, sig?: Signature): string {
    const fields: Array<any> = [
        formatNumber(tx.chainId, "chainId"),
        formatNumber(tx.nonce, "nonce"),
        formatNumber(tx.maxPriorityFeePerGas || 0, "maxPriorityFeePerGas"),
        formatNumber(tx.maxFeePerGas || 0, "maxFeePerGas"),
        formatNumber(tx.gasLimit, "gasLimit"),
        (tx.to || "0x"),
        formatNumber(tx.value, "value"),
        tx.data,
        formatAccessList(tx.accessList || [ ])
    ];

    if (sig) {
        fields.push(formatNumber(sig.yParity, "yParity"));
        fields.push(toBeArray(sig.r));
        fields.push(toBeArray(sig.s));
    }

    return concat([ "0x02", encodeRlp(fields)]);
}

function _parseEip2930(data: Uint8Array): TransactionLike {
    const fields: any = decodeRlp(getBytes(data).slice(1));

    assertArgument(Array.isArray(fields) && (fields.length === 8 || fields.length === 11),
        "invalid field count for transaction type: 1", "data", hexlify(data));

    const tx: TransactionLike = {
        type:       1,
        chainId:    handleUint(fields[0], "chainId"),
        nonce:      handleNumber(fields[1], "nonce"),
        gasPrice:   handleUint(fields[2], "gasPrice"),
        gasLimit:   handleUint(fields[3], "gasLimit"),
        to:         handleAddress(fields[4]),
        value:      handleUint(fields[5], "value"),
        data:       hexlify(fields[6]),
        accessList: handleAccessList(fields[7], "accessList")
    };

    // Unsigned EIP-2930 Transaction
    if (fields.length === 8) { return tx; }

    tx.hash = keccak256(data);

    _parseEipSignature(tx, fields.slice(8));

    return tx;
}

function _serializeEip2930(tx: Transaction, sig?: Signature): string {
    const fields: any = [
        formatNumber(tx.chainId, "chainId"),
        formatNumber(tx.nonce, "nonce"),
        formatNumber(tx.gasPrice || 0, "gasPrice"),
        formatNumber(tx.gasLimit, "gasLimit"),
        (tx.to || "0x"),
        formatNumber(tx.value, "value"),
        tx.data,
        formatAccessList(tx.accessList || [ ])
    ];

    if (sig) {
        fields.push(formatNumber(sig.yParity, "recoveryParam"));
        fields.push(toBeArray(sig.r));
        fields.push(toBeArray(sig.s));
    }

    return concat([ "0x01", encodeRlp(fields)]);
}

function _parseEip4844(data: Uint8Array): TransactionLike {
    const fields: any = decodeRlp(getBytes(data).slice(1));

    assertArgument(Array.isArray(fields) && (fields.length === 11 || fields.length === 14),
        "invalid field count for transaction type: 3", "data", hexlify(data));

    const tx: TransactionLike = {
        type:                  3,
        chainId:               handleUint(fields[0], "chainId"),
        nonce:                 handleNumber(fields[1], "nonce"),
        maxPriorityFeePerGas:  handleUint(fields[2], "maxPriorityFeePerGas"),
        maxFeePerGas:          handleUint(fields[3], "maxFeePerGas"),
        gasPrice:              null,
        gasLimit:              handleUint(fields[4], "gasLimit"),
        to:                    handleAddress(fields[5]),
        value:                 handleUint(fields[6], "value"),
        data:                  hexlify(fields[7]),
        accessList:            handleAccessList(fields[8], "accessList"),
        maxFeePerBlobGas:      handleUint(fields[9], "maxFeePerBlobGas"),
        blobVersionedHashes:   fields[10]
    };

    assertArgument(tx.to != null, "invalid address for transaction type: 3", "data", data);

    assertArgument(Array.isArray(tx.blobVersionedHashes), "invalid blobVersionedHashes: must be an array", "data", data);
    for (let i = 0; i < tx.blobVersionedHashes.length; i++) {
        assertArgument(isHexString(tx.blobVersionedHashes[i], 32), `invalid blobVersionedHash at index ${ i }: must be length 32`, "data", data);
    }

    // Unsigned EIP-4844 Transaction
    if (fields.length === 11) { return tx; }

    tx.hash = keccak256(data);

    _parseEipSignature(tx, fields.slice(11));

    return tx;
}

function _serializeEip4844(tx: Transaction, sig?: Signature): string {
    const fields: Array<any> = [
        formatNumber(tx.chainId, "chainId"),
        formatNumber(tx.nonce, "nonce"),
        formatNumber(tx.maxPriorityFeePerGas || 0, "maxPriorityFeePerGas"),
        formatNumber(tx.maxFeePerGas || 0, "maxFeePerGas"),
        formatNumber(tx.gasLimit, "gasLimit"),
        (tx.to || ZeroAddress),
        formatNumber(tx.value, "value"),
        tx.data,
        formatAccessList(tx.accessList || [ ]),
        formatNumber(tx.maxFeePerBlobGas || 0, "maxFeePerBlobGas"),
        formatHashes(tx.blobVersionedHashes || [ ], "blobVersionedHashes")
    ];

    if (sig) {
        fields.push(formatNumber(sig.yParity, "yParity"));
        fields.push(toBeArray(sig.r));
        fields.push(toBeArray(sig.s));
    }

    return concat([ "0x03", encodeRlp(fields)]);
}

/**
 *  A **Transaction** describes an operation to be executed on
 *  Ethereum by an Externally Owned Account (EOA). It includes
 *  who (the [[to]] address), what (the [[data]]) and how much (the
 *  [[value]] in ether) the operation should entail.
 *
 *  @example:
 *    tx = new Transaction()
 *    //_result:
 *
 *    tx.data = "0x1234";
 *    //_result:
 */
export class Transaction implements TransactionLike<string> {
    #type: null | number;
    #to: null | string;
    #data: string;
    #nonce: number;
    #gasLimit: bigint;
    #gasPrice: null | bigint;
    #maxPriorityFeePerGas: null | bigint;
    #maxFeePerGas: null | bigint;
    #value: bigint;
    #chainId: bigint;
    #sig: null | Signature;
    #accessList: null | AccessList;
    #maxFeePerBlobGas: null | bigint;
    #blobVersionedHashes: null | Array<string>;

    /**
     *  The transaction type.
     *
     *  If null, the type will be automatically inferred based on
     *  explicit properties.
     */
    get type(): null | number { return this.#type; }
    set type(value: null | number | string) {
        switch (value) {
            case null:
                this.#type = null;
                break;
            case 0: case "legacy":
                this.#type = 0;
                break;
            case 1: case "berlin": case "eip-2930":
                this.#type = 1;
                break;
            case 2: case "london": case "eip-1559":
                this.#type = 2;
                break;
            case 3: case "cancun": case "eip-4844":
                this.#type = 3;
                break;
            default:
                assertArgument(false, "unsupported transaction type", "type", value);
        }
    }

    /**
     *  The name of the transaction type.
     */
    get typeName(): null | string {
        switch (this.type) {
            case 0: return "legacy";
            case 1: return "eip-2930";
            case 2: return "eip-1559";
            case 3: return "eip-4844";
        }

        return null;
    }

    /**
     *  The ``to`` address for the transaction or ``null`` if the
     *  transaction is an ``init`` transaction.
     */
    get to(): null | string {
        const value = this.#to;
        if (value == null && this.type === 3) { return ZeroAddress; }
        return value;
    }
    set to(value: null | string) {
        this.#to = (value == null) ? null: getAddress(value);
    }

    /**
     *  The transaction nonce.
     */
    get nonce(): number { return this.#nonce; }
    set nonce(value: BigNumberish) { this.#nonce = getNumber(value, "value"); }

    /**
     *  The gas limit.
     */
    get gasLimit(): bigint { return this.#gasLimit; }
    set gasLimit(value: BigNumberish) { this.#gasLimit = getBigInt(value); }

    /**
     *  The gas price.
     *
     *  On legacy networks this defines the fee that will be paid. On
     *  EIP-1559 networks, this should be ``null``.
     */
    get gasPrice(): null | bigint {
        const value = this.#gasPrice;
        if (value == null && (this.type === 0 || this.type === 1)) { return BN_0; }
        return value;
    }
    set gasPrice(value: null | BigNumberish) {
        this.#gasPrice = (value == null) ? null: getBigInt(value, "gasPrice");
    }

    /**
     *  The maximum priority fee per unit of gas to pay. On legacy
     *  networks this should be ``null``.
     */
    get maxPriorityFeePerGas(): null | bigint {
        const value = this.#maxPriorityFeePerGas;
        if (value == null) {
            if (this.type === 2 || this.type === 3) { return BN_0; }
            return null;
        }
        return value;
    }
    set maxPriorityFeePerGas(value: null | BigNumberish) {
        this.#maxPriorityFeePerGas = (value == null) ? null: getBigInt(value, "maxPriorityFeePerGas");
    }

    /**
     *  The maximum total fee per unit of gas to pay. On legacy
     *  networks this should be ``null``.
     */
    get maxFeePerGas(): null | bigint {
        const value = this.#maxFeePerGas;
        if (value == null) {
            if (this.type === 2 || this.type === 3) { return BN_0; }
            return null;
        }
        return value;
    }
    set maxFeePerGas(value: null | BigNumberish) {
        this.#maxFeePerGas = (value == null) ? null: getBigInt(value, "maxFeePerGas");
    }

    /**
     *  The transaction data. For ``init`` transactions this is the
     *  deployment code.
     */
    get data(): string { return this.#data; }
    set data(value: BytesLike) { this.#data = hexlify(value); }

    /**
     *  The amount of ether (in wei) to send in this transactions.
     */
    get value(): bigint { return this.#value; }
    set value(value: BigNumberish) {
        this.#value = getBigInt(value, "value");
    }

    /**
     *  The chain ID this transaction is valid on.
     */
    get chainId(): bigint { return this.#chainId; }
    set chainId(value: BigNumberish) { this.#chainId = getBigInt(value); }

    /**
     *  If signed, the signature for this transaction.
     */
    get signature(): null | Signature { return this.#sig || null; }
    set signature(value: null | SignatureLike) {
        this.#sig = (value == null) ? null: Signature.from(value);
    }

    /**
     *  The access list.
     *
     *  An access list permits discounted (but pre-paid) access to
     *  bytecode and state variable access within contract execution.
     */
    get accessList(): null | AccessList {
        const value = this.#accessList || null;
        if (value == null) {
            if (this.type === 1 || this.type === 2 || this.type === 3) {
                // @TODO: in v7, this should assign the value or become
                // a live object itself, otherwise mutation is inconsistent
                return [ ];
            }
            return null;
        }
        return value;
    }
    set accessList(value: null | AccessListish) {
        this.#accessList = (value == null) ? null: accessListify(value);
    }

    /**
     *  The max fee per blob gas for Cancun transactions.
     */
    get maxFeePerBlobGas(): null | bigint {
        const value = this.#maxFeePerBlobGas;
        if (value == null && this.type === 3) { return BN_0; }
        return value;
    }
    set maxFeePerBlobGas(value: null | BigNumberish) {
        this.#maxFeePerBlobGas = (value == null) ? null: getBigInt(value, "maxFeePerBlobGas");
    }

    /**
     *  The BLOB versioned hashes for Cancun transactions.
     */
    get blobVersionedHashes(): null | Array<string> {
        // @TODO: Mutation is inconsistent; if unset, the returned value
        // cannot mutate the object, if set it can
        let value = this.#blobVersionedHashes;
        if (value == null && this.type === 3) { return [ ]; }
        return value;
    }
    set blobVersionedHashes(value: null | Array<string>) {
        if (value != null) {
            assertArgument(Array.isArray(value), "blobVersionedHashes must be an Array", "value", value);
            value = value.slice();
            for (let i = 0; i < value.length; i++) {
                assertArgument(isHexString(value[i], 32), "invalid blobVersionedHash", `value[${ i }]`, value[i]);
            }
        }
        this.#blobVersionedHashes = value;
    }

    /**
     *  Creates a new Transaction with default values.
     */
    constructor() {
        this.#type = null;
        this.#to = null;
        this.#nonce = 0;
        this.#gasLimit = BN_0;
        this.#gasPrice = null;
        this.#maxPriorityFeePerGas = null;
        this.#maxFeePerGas = null;
        this.#data = "0x";
        this.#value = BN_0;
        this.#chainId = BN_0;
        this.#sig = null;
        this.#accessList = null;
        this.#maxFeePerBlobGas = null;
        this.#blobVersionedHashes = null;
    }

    /**
     *  The transaction hash, if signed. Otherwise, ``null``.
     */
    get hash(): null | string {
        if (this.signature == null) { return null; }
        return keccak256(this.serialized);
    }

    /**
     *  The pre-image hash of this transaction.
     *
     *  This is the digest that a [[Signer]] must sign to authorize
     *  this transaction.
     */
    get unsignedHash(): string {
        return keccak256(this.unsignedSerialized);
    }

    /**
     *  The sending address, if signed. Otherwise, ``null``.
     */
    get from(): null | string {
        if (this.signature == null) { return null; }
        return recoverAddress(this.unsignedHash, this.signature);
    }

    /**
     *  The public key of the sender, if signed. Otherwise, ``null``.
     */
    get fromPublicKey(): null | string {
        if (this.signature == null) { return null; }
        return SigningKey.recoverPublicKey(this.unsignedHash, this.signature);
    }

    /**
     *  Returns true if signed.
     *
     *  This provides a Type Guard that properties requiring a signed
     *  transaction are non-null.
     */
    isSigned(): this is (Transaction & { type: number, typeName: string, from: string, signature: Signature }) {
        return this.signature != null;
    }

    /**
     *  The serialized transaction.
     *
     *  This throws if the transaction is unsigned. For the pre-image,
     *  use [[unsignedSerialized]].
     */
    get serialized(): string {
        assert(this.signature != null, "cannot serialize unsigned transaction; maybe you meant .unsignedSerialized", "UNSUPPORTED_OPERATION", { operation: ".serialized"});

        switch (this.inferType()) {
            case 0:
                return _serializeLegacy(this, this.signature);
            case 1:
                return _serializeEip2930(this, this.signature);
            case 2:
                return _serializeEip1559(this, this.signature);
            case 3:
                return _serializeEip4844(this, this.signature);
        }

        assert(false, "unsupported transaction type", "UNSUPPORTED_OPERATION", { operation: ".serialized" });
    }

    /**
     *  The transaction pre-image.
     *
     *  The hash of this is the digest which needs to be signed to
     *  authorize this transaction.
     */
    get unsignedSerialized(): string {
        switch (this.inferType()) {
            case 0:
                return _serializeLegacy(this);
            case 1:
                return _serializeEip2930(this);
            case 2:
                return _serializeEip1559(this);
            case 3:
                return _serializeEip4844(this);
        }

        assert(false, "unsupported transaction type", "UNSUPPORTED_OPERATION", { operation: ".unsignedSerialized" });
    }

    /**
     *  Return the most "likely" type; currently the highest
     *  supported transaction type.
     */
    inferType(): number {
        const types = this.inferTypes();

        // Prefer London (EIP-1559) over Cancun (BLOb)
        if (types.indexOf(2) >= 0) { return 2; }

        // Return the highest inferred type
        return <number>(types.pop());
    }

    /**
     *  Validates the explicit properties and returns a list of compatible
     *  transaction types.
     */
    inferTypes(): Array<number> {

        // Checks that there are no conflicting properties set
        const hasGasPrice = this.gasPrice != null;
        const hasFee = (this.maxFeePerGas != null || this.maxPriorityFeePerGas != null);
        const hasAccessList = (this.accessList != null);
        const hasBlob = (this.#maxFeePerBlobGas != null || this.#blobVersionedHashes);

        //if (hasGasPrice && hasFee) {
        //    throw new Error("transaction cannot have gasPrice and maxFeePerGas");
        //}

        if (this.maxFeePerGas != null && this.maxPriorityFeePerGas != null) {
            assert(this.maxFeePerGas >= this.maxPriorityFeePerGas, "priorityFee cannot be more than maxFee", "BAD_DATA", { value: this });
        }

        //if (this.type === 2 && hasGasPrice) {
        //    throw new Error("eip-1559 transaction cannot have gasPrice");
        //}

        assert(!hasFee || (this.type !== 0 && this.type !== 1), "transaction type cannot have maxFeePerGas or maxPriorityFeePerGas", "BAD_DATA", { value: this });
        assert(this.type !== 0 || !hasAccessList, "legacy transaction cannot have accessList", "BAD_DATA", { value: this })

        const types: Array<number> = [ ];

        // Explicit type
        if (this.type != null) {
            types.push(this.type);

        } else {
            if (hasFee) {
                types.push(2);
            } else if (hasGasPrice) {
                types.push(1);
                if (!hasAccessList) { types.push(0); }
            } else if (hasAccessList) {
                types.push(1);
                types.push(2);
            } else if (hasBlob && this.to) {
                types.push(3);
            } else {
                types.push(0);
                types.push(1);
                types.push(2);
                types.push(3);
            }
        }

        types.sort();

        return types;
    }

    /**
     *  Returns true if this transaction is a legacy transaction (i.e.
     *  ``type === 0``).
     *
     *  This provides a Type Guard that the related properties are
     *  non-null.
     */
    isLegacy(): this is (Transaction & { type: 0, gasPrice: bigint }) {
        return (this.type === 0);
    }

    /**
     *  Returns true if this transaction is berlin hardform transaction (i.e.
     *  ``type === 1``).
     *
     *  This provides a Type Guard that the related properties are
     *  non-null.
     */
    isBerlin(): this is (Transaction & { type: 1, gasPrice: bigint, accessList: AccessList }) {
        return (this.type === 1);
    }

    /**
     *  Returns true if this transaction is london hardform transaction (i.e.
     *  ``type === 2``).
     *
     *  This provides a Type Guard that the related properties are
     *  non-null.
     */
    isLondon(): this is (Transaction & { type: 2, accessList: AccessList, maxFeePerGas: bigint, maxPriorityFeePerGas: bigint }) {
        return (this.type === 2);
    }

    /**
     *  Returns true if this transaction is an [[link-eip-4844]] BLOB
     *  transaction.
     *
     *  This provides a Type Guard that the related properties are
     *  non-null.
     */
    isCancun(): this is (Transaction & { type: 3, to: string, accessList: AccessList, maxFeePerGas: bigint, maxPriorityFeePerGas: bigint, maxFeePerBlobGas: bigint, blobVersionedHashes: Array<string> }) {
        return (this.type === 3);
    }

    /**
     *  Create a copy of this transaciton.
     */
    clone(): Transaction {
        return Transaction.from(this);
    }

    /**
     *  Return a JSON-friendly object.
     */
    toJSON(): any {
        const s = (v: null | bigint) => {
            if (v == null) { return null; }
            return v.toString();
        };

        return {
            type: this.type,
            to: this.to,
//            from: this.from,
            data: this.data,
            nonce: this.nonce,
            gasLimit: s(this.gasLimit),
            gasPrice: s(this.gasPrice),
            maxPriorityFeePerGas: s(this.maxPriorityFeePerGas),
            maxFeePerGas: s(this.maxFeePerGas),
            value: s(this.value),
            chainId: s(this.chainId),
            sig: this.signature ? this.signature.toJSON(): null,
            accessList: this.accessList
        };
    }

    /**
     *  Create a **Transaction** from a serialized transaction or a
     *  Transaction-like object.
     */
    static from(tx?: string | TransactionLike<string>): Transaction {
        if (tx == null) { return new Transaction(); }

        if (typeof(tx) === "string") {
            const payload = getBytes(tx);

            if (payload[0] >= 0x7f) { // @TODO: > vs >= ??
                return Transaction.from(_parseLegacy(payload));
            }

            switch(payload[0]) {
                case 1: return Transaction.from(_parseEip2930(payload));
                case 2: return Transaction.from(_parseEip1559(payload));
                case 3: return Transaction.from(_parseEip4844(payload));
            }
            assert(false, "unsupported transaction type", "UNSUPPORTED_OPERATION", { operation: "from" });
        }

        const result = new Transaction();
        if (tx.type != null) { result.type = tx.type; }
        if (tx.to != null) { result.to = tx.to; }
        if (tx.nonce != null) { result.nonce = tx.nonce; }
        if (tx.gasLimit != null) { result.gasLimit = tx.gasLimit; }
        if (tx.gasPrice != null) { result.gasPrice = tx.gasPrice; }
        if (tx.maxPriorityFeePerGas != null) { result.maxPriorityFeePerGas = tx.maxPriorityFeePerGas; }
        if (tx.maxFeePerGas != null) { result.maxFeePerGas = tx.maxFeePerGas; }
        if (tx.maxFeePerBlobGas != null) { result.maxFeePerBlobGas = tx.maxFeePerBlobGas; }
        if (tx.data != null) { result.data = tx.data; }
        if (tx.value != null) { result.value = tx.value; }
        if (tx.chainId != null) { result.chainId = tx.chainId; }
        if (tx.signature != null) { result.signature = Signature.from(tx.signature); }
        if (tx.accessList != null) { result.accessList = tx.accessList; }
        if (tx.blobVersionedHashes != null) { result.blobVersionedHashes = tx.blobVersionedHashes; }

        if (tx.hash != null) {
            assertArgument(result.isSigned(), "unsigned transaction cannot define hash", "tx", tx);
            assertArgument(result.hash === tx.hash, "hash mismatch", "tx", tx);
        }

        if (tx.from != null) {
            assertArgument(result.isSigned(), "unsigned transaction cannot define from", "tx", tx);
            assertArgument(result.from.toLowerCase() === (tx.from || "").toLowerCase(), "from mismatch", "tx", tx);
        }

        return result;
    }
}