BlocksService.ts

import { ApiPromise } from '@polkadot/api';
import { Struct } from '@polkadot/types';
import { GenericCall } from '@polkadot/types';
import {
	AccountId,
	Block,
	BlockHash,
	Digest,
	DispatchInfo,
	EventRecord,
	Hash,
} from '@polkadot/types/interfaces';
import { AnyJson, Codec } from '@polkadot/types/types';
import { u8aToHex } from '@polkadot/util';
import { blake2AsU8a } from '@polkadot/util-crypto';
import { CalcFee } from '@substrate/calc';

import {
	IBlock,
	IExtrinsic,
	ISanitizedCall,
	ISanitizedEvent,
} from '../../types/responses';
import { isPaysFee } from '../../types/util';
import { AbstractService } from '../AbstractService';

/**
 * Event methods that we check for.
 */
enum Event {
	success = 'system.ExtrinsicSuccess',
	failure = 'system.ExtrinsicFailed',
}

export class BlocksService extends AbstractService {
	/**
	 * Fetch a block enhanced with augmented and derived values.
	 *
	 * @param hash `BlockHash` of the block to fetch.
	 */
	async fetchBlock(hash: BlockHash): Promise<IBlock> {
		const api = await this.ensureMeta(hash);
		const [{ block }, events, validators] = await Promise.all([
			api.rpc.chain.getBlock(hash),
			this.fetchEvents(api, hash),
			api.query.session.validators.at(hash),
		]);

		const {
			parentHash,
			number,
			stateRoot,
			extrinsicsRoot,
			digest,
		} = block.header;

		const authorId = this.extractAuthor(validators, digest);

		const logs = digest.logs.map((log) => {
			const { type, index, value } = log;

			return { type, index, value };
		});

		const nonSanitizedExtrinsics = this.extractExtrinsics(block, events);

		const { extrinsics, onInitialize, onFinalize } = this.sanitizeEvents(
			events,
			nonSanitizedExtrinsics,
			hash
		);

		// The genesis block is a special case with little information associated with it.
		if (parentHash.every((byte) => !byte)) {
			return {
				number,
				hash,
				parentHash,
				stateRoot,
				extrinsicsRoot,
				authorId,
				logs,
				onInitialize,
				extrinsics,
				onFinalize,
			};
		}

		const { calcFee, specName, specVersion } = await this.createCalcFee(
			api,
			parentHash,
			block
		);

		for (let idx = 0; idx < block.extrinsics.length; ++idx) {
			if (!extrinsics[idx].paysFee || !block.extrinsics[idx].isSigned) {
				continue;
			}

			if (calcFee === null || calcFee === undefined) {
				extrinsics[idx].info = {
					error: `Fee calculation not supported for ${specName}#${specVersion}`,
				};
				continue;
			}

			try {
				const xtEvents = extrinsics[idx].events;
				const completedEvent = xtEvents.find(
					({ method }) =>
						method === Event.success || method === Event.failure
				);
				if (!completedEvent) {
					extrinsics[idx].info = {
						error:
							'Unable to find success or failure event for extrinsic',
					};

					continue;
				}

				const completedData = completedEvent.data;
				if (!completedData) {
					extrinsics[idx].info = {
						error:
							'Success or failure event for extrinsic does not contain expected data',
					};

					continue;
				}

				// both ExtrinsicSuccess and ExtrinsicFailed events have DispatchInfo
				// types as their final arg
				const weightInfo = completedData[
					completedData.length - 1
				] as DispatchInfo;
				if (!weightInfo.weight) {
					extrinsics[idx].info = {
						error:
							'Success or failure event for extrinsic does not specify weight',
					};

					continue;
				}

				const len = block.extrinsics[idx].encodedLength;
				const weight = weightInfo.weight;

				const partialFee = calcFee.calc_fee(
					BigInt(weight.toString()),
					len
				);

				extrinsics[idx].info = api.createType('RuntimeDispatchInfo', {
					weight,
					class: weightInfo.class,
					partialFee: partialFee,
				});
			} catch (err) {
				console.error(err);
				extrinsics[idx].info = { error: 'Unable to fetch fee info' };
			}
		}

		return {
			number,
			hash,
			parentHash,
			stateRoot,
			extrinsicsRoot,
			authorId,
			logs,
			onInitialize,
			extrinsics,
			onFinalize,
		};
	}

	/**
	 * Extract extrinsics from a block.
	 *
	 * @param block Block
	 * @param events events fetched by `fetchEvents`
	 */
	private extractExtrinsics(block: Block, events: EventRecord[] | string) {
		const defaultSuccess = typeof events === 'string' ? events : false;

		return block.extrinsics.map((extrinsic) => {
			const {
				method,
				nonce,
				signature,
				signer,
				isSigned,
				tip,
			} = extrinsic;
			const hash = u8aToHex(blake2AsU8a(extrinsic.toU8a(), 256));

			return {
				method: {
					pallet: method.sectionName,
					methodName: method.methodName,
				},
				signature: isSigned ? { signature, signer } : null,
				nonce,
				args: this.parseGenericCall(method).args,
				tip,
				hash,
				info: {},
				events: [] as ISanitizedEvent[],
				success: defaultSuccess,
				// paysFee overrides to bool if `system.ExtrinsicSuccess|ExtrinsicFailed` event is present
				paysFee: null as null | boolean,
			};
		});
	}

	/**
	 * Sanitize events and attribute them to an extrinsic, onInitialize, or
	 * onFinalize.
	 *
	 * @param events events from `fetchEvents`
	 * @param extrinsics extrinsics from
	 * @param hash hash of the block the events are from
	 */
	private sanitizeEvents(
		events: EventRecord[] | string,
		extrinsics: IExtrinsic[],
		hash: BlockHash
	) {
		const onInitialize = { events: [] as ISanitizedEvent[] };
		const onFinalize = { events: [] as ISanitizedEvent[] };

		if (Array.isArray(events)) {
			for (const record of events) {
				const { event, phase } = record;
				const sanitizedEvent = {
					method: `${event.section}.${event.method}`,
					data: event.data,
				};

				if (phase.isApplyExtrinsic) {
					const extrinsicIdx = phase.asApplyExtrinsic.toNumber();
					const extrinsic = extrinsics[extrinsicIdx];

					if (!extrinsic) {
						throw new Error(
							`Missing extrinsic ${extrinsicIdx} in block ${hash.toString()}`
						);
					}

					const method = `${event.section}.${event.method}`;

					if (method === Event.success) {
						extrinsic.success = true;
					}

					if (method === Event.success || method === Event.failure) {
						const sanitizedData = event.data.toJSON() as AnyJson[];

						for (const data of sanitizedData) {
							if (isPaysFee(data)) {
								extrinsic.paysFee =
									data.paysFee === true ||
									data.paysFee === 'Yes';

								break;
							}
						}
					}

					extrinsic.events.push(sanitizedEvent);
				} else if (phase.isFinalization) {
					onFinalize.events.push(sanitizedEvent);
				} else if (phase.isInitialization) {
					onInitialize.events.push(sanitizedEvent);
				}
			}
		}

		return {
			extrinsics,
			onInitialize,
			onFinalize,
		};
	}

	/**
	 * Create calcFee from params.
	 *
	 * @param api ApiPromise
	 * @param parentHash Hash of the parent block
	 * @param block Block which the extrinsic is from
	 */
	private async createCalcFee(
		api: ApiPromise,
		parentHash: Hash,
		block: Block
	) {
		let parentParentHash: Hash;
		if (block.header.number.toNumber() > 1) {
			parentParentHash = (await api.rpc.chain.getHeader(parentHash))
				.parentHash;
		} else {
			parentParentHash = parentHash;
		}

		const perByte = api.consts.transactionPayment.transactionByteFee;
		const extrinsicBaseWeight = api.consts.system.extrinsicBaseWeight;
		const multiplier = await api.query.transactionPayment.nextFeeMultiplier.at(
			parentHash
		);
		// The block where the runtime is deployed falsely proclaims it would
		// be already using the new runtime. This workaround therefore uses the
		// parent of the parent in order to determine the correct runtime under which
		// this block was produced.
		const version = await api.rpc.state.getRuntimeVersion(parentParentHash);
		const specName = version.specName.toString();
		const specVersion = version.specVersion.toNumber();
		const coefficients = api.consts.transactionPayment.weightToFee.map(
			(c) => {
				return {
					coeffInteger: c.coeffInteger.toString(),
					coeffFrac: c.coeffFrac,
					degree: c.degree,
					negative: c.negative,
				};
			}
		);

		return {
			calcFee: CalcFee.from_params(
				coefficients,
				BigInt(extrinsicBaseWeight.toString()),
				multiplier.toString(),
				perByte.toString(),
				specName,
				specVersion
			),
			specName,
			specVersion,
		};
	}

	/**
	 * Fetch events for the specified block.
	 *
	 * @param api ApiPromise to use for query
	 * @param hash `BlockHash` to make query at
	 */
	private async fetchEvents(
		api: ApiPromise,
		hash: BlockHash
	): Promise<EventRecord[] | string> {
		try {
			return await api.query.system.events.at(hash);
		} catch {
			return 'Unable to fetch Events, cannot confirm extrinsic status. Check pruning settings on the node.';
		}
	}

	/**
	 * Helper function for `parseGenericCall`.
	 *
	 * @param argsArray array of `Codec` values
	 */
	private parseArrayGenericCalls(
		argsArray: Codec[]
	): (Codec | ISanitizedCall)[] {
		return argsArray.map((argument) => {
			if (argument instanceof GenericCall) {
				return this.parseGenericCall(argument);
			}

			return argument;
		});
	}

	/**
	 * Recursively parse a `GenericCall` in order to label its arguments with
	 * their param names and give a human friendly method name (opposed to just a
	 * call index). Parses `GenericCall`s that are nested as arguments.
	 *
	 * @param genericCall `GenericCall`
	 */
	private parseGenericCall(genericCall: GenericCall): ISanitizedCall {
		const { sectionName, methodName } = genericCall;
		const newArgs = {};

		// Pull out the struct of arguments to this call
		const callArgs = genericCall.get('args') as Struct;

		// Make sure callArgs exists and we can access its keys
		if (callArgs && callArgs.defKeys) {
			// paramName is a string
			for (const paramName of callArgs.defKeys) {
				const argument = callArgs.get(paramName);

				if (Array.isArray(argument)) {
					newArgs[paramName] = this.parseArrayGenericCalls(argument);
				} else if (argument instanceof GenericCall) {
					newArgs[paramName] = this.parseGenericCall(argument);
				} else if (
					paramName === 'call' &&
					argument?.toRawType() === 'Bytes'
				) {
					// multiSig.asMulti.args.call is an OpaqueCall (Vec<u8>) that we
					// serialize to a polkadot-js Call and parse so it is not a hex blob.
					const call = this.api.createType('Call', argument.toHex());
					newArgs[paramName] = this.parseGenericCall(call);
				} else {
					newArgs[paramName] = argument;
				}
			}
		}

		return {
			method: `${sectionName}.${methodName}`,
			args: newArgs,
		};
	}

	// Almost exact mimic of https://github.com/polkadot-js/api/blob/master/packages/api-derive/src/chain/getHeader.ts#L27
	// but we save a call to `getHeader` by hardcoding the logic here and using the digest from the blocks header.
	private extractAuthor(
		sessionValidators: AccountId[],
		digest: Digest
	): AccountId | undefined {
		const [pitem] = digest.logs.filter(({ type }) => type === 'PreRuntime');

		// extract from the substrate 2.0 PreRuntime digest
		if (pitem) {
			const [engine, data] = pitem.asPreRuntime;

			return engine.extractAuthor(data, sessionValidators);
		} else {
			const [citem] = digest.logs.filter(
				({ type }) => type === 'Consensus'
			);

			// extract author from the consensus (substrate 1.0, digest)
			if (citem) {
				const [engine, data] = citem.asConsensus;

				return engine.extractAuthor(data, sessionValidators);
			}
		}

		return undefined;
	}
}