import {
	DataAndSlot,
	BufferAndSlot,
	AccountSubscriber,
	ResubOpts,
} from './types';
import { AnchorProvider } from '../isomorphic/anchor';
import { AccountInfo, Commitment, Context, PublicKey } from '@solana/web3.js';
import { DriftProgram } from '../config';
import * as Buffer from 'buffer';

export class WebSocketAccountSubscriber<T> implements AccountSubscriber<T> {
	dataAndSlot?: DataAndSlot<T>;
	bufferAndSlot?: BufferAndSlot;
	accountName: string;
	logAccountName: string;
	program: DriftProgram;
	accountPublicKey: PublicKey;
	decodeBufferFn: (buffer: Buffer) => T;
	onChange: (data: T) => void;
	listenerId?: number;

	resubOpts?: ResubOpts;

	commitment?: Commitment;
	isUnsubscribing = false;

	timeoutId?: ReturnType<typeof setTimeout>;

	receivingData: boolean;

	public constructor(
		accountName: string,
		program: DriftProgram,
		accountPublicKey: PublicKey,
		decodeBuffer?: (buffer: Buffer) => T,
		resubOpts?: ResubOpts,
		commitment?: Commitment
	) {
		this.accountName = accountName;
		this.logAccountName = `${accountName}-${accountPublicKey.toBase58()}`;
		this.program = program;
		this.accountPublicKey = accountPublicKey;
		this.decodeBufferFn = decodeBuffer;
		this.resubOpts = resubOpts;
		if (this.resubOpts?.resubTimeoutMs < 1000) {
			console.log(
				`resubTimeoutMs should be at least 1000ms to avoid spamming resub ${this.logAccountName}`
			);
		}
		this.receivingData = false;
		this.commitment =
			commitment ?? (this.program.provider as AnchorProvider).opts.commitment;
	}

	async subscribe(onChange: (data: T) => void): Promise<void> {
		if (this.listenerId != null || this.isUnsubscribing) {
			if (this.resubOpts?.logResubMessages) {
				console.log(
					`[${this.logAccountName}] Subscribe returning early - listenerId=${this.listenerId}, isUnsubscribing=${this.isUnsubscribing}`
				);
			}
			return;
		}

		this.onChange = onChange;
		if (!this.dataAndSlot) {
			await this.fetch();
		}

		this.listenerId = this.program.provider.connection.onAccountChange(
			this.accountPublicKey,
			(accountInfo, context) => {
				if (this.resubOpts?.resubTimeoutMs) {
					this.receivingData = true;
					clearTimeout(this.timeoutId);
					this.handleRpcResponse(context, accountInfo);
					this.setTimeout();
				} else {
					this.handleRpcResponse(context, accountInfo);
				}
			},
			this.commitment
		);

		if (this.resubOpts?.resubTimeoutMs) {
			this.receivingData = true;
			this.setTimeout();
		}
	}

	setData(data: T, slot?: number): void {
		const newSlot = slot || 0;
		if (this.dataAndSlot && this.dataAndSlot.slot > newSlot) {
			return;
		}

		this.dataAndSlot = {
			data,
			slot,
		};
	}

	protected setTimeout(): void {
		if (!this.onChange) {
			throw new Error('onChange callback function must be set');
		}
		this.timeoutId = setTimeout(
			async () => {
				if (this.isUnsubscribing) {
					// If we are in the process of unsubscribing, do not attempt to resubscribe
					if (this.resubOpts?.logResubMessages) {
						console.log(
							`[${this.logAccountName}] Timeout fired but isUnsubscribing=true, skipping resubscribe`
						);
					}
					return;
				}

				if (this.receivingData) {
					if (this.resubOpts?.logResubMessages) {
						console.log(
							`No ws data from ${this.logAccountName} in ${this.resubOpts.resubTimeoutMs}ms, resubscribing - listenerId=${this.listenerId}, isUnsubscribing=${this.isUnsubscribing}`
						);
					}
					await this.unsubscribe(true);
					this.receivingData = false;
					await this.subscribe(this.onChange);
					if (this.resubOpts?.logResubMessages) {
						console.log(
							`[${this.logAccountName}] Resubscribe completed - receivingData=${this.receivingData}, listenerId=${this.listenerId}, isUnsubscribing=${this.isUnsubscribing}`
						);
					}
				} else {
					if (this.resubOpts?.logResubMessages) {
						console.log(
							`[${this.logAccountName}] Timeout fired but receivingData=false, skipping resubscribe`
						);
					}
				}
			},
			this.resubOpts?.resubTimeoutMs
		);
	}

	async fetch(): Promise<void> {
		const rpcResponse =
			await this.program.provider.connection.getAccountInfoAndContext(
				this.accountPublicKey,
				(this.program.provider as AnchorProvider).opts.commitment
			);
		this.handleRpcResponse(rpcResponse.context, rpcResponse?.value);
	}

	handleRpcResponse(context: Context, accountInfo?: AccountInfo<Buffer>): void {
		const newSlot = context.slot;
		let newBuffer: Buffer | undefined = undefined;
		if (accountInfo) {
			newBuffer = accountInfo.data;
		}

		if (!this.bufferAndSlot) {
			this.bufferAndSlot = {
				buffer: newBuffer,
				slot: newSlot,
			};
			if (newBuffer) {
				const account = this.decodeBuffer(newBuffer);
				this.dataAndSlot = {
					data: account,
					slot: newSlot,
				};
				this.onChange(account);
			}
			return;
		}

		if (newSlot < this.bufferAndSlot.slot) {
			return;
		}

		const oldBuffer = this.bufferAndSlot.buffer;
		if (newBuffer && (!oldBuffer || !newBuffer.equals(oldBuffer))) {
			this.bufferAndSlot = {
				buffer: newBuffer,
				slot: newSlot,
			};
			const account = this.decodeBuffer(newBuffer);
			this.dataAndSlot = {
				data: account,
				slot: newSlot,
			};
			this.onChange(account);
		}
	}

	decodeBuffer(buffer: Buffer): T {
		if (this.decodeBufferFn) {
			return this.decodeBufferFn(buffer);
		} else {
			return this.program.account[this.accountName].coder.accounts.decode(
				this.accountName,
				buffer
			);
		}
	}

	unsubscribe(onResub = false): Promise<void> {
		if (!onResub && this.resubOpts) {
			this.resubOpts.resubTimeoutMs = undefined;
		}
		this.isUnsubscribing = true;
		clearTimeout(this.timeoutId);
		this.timeoutId = undefined;

		if (this.listenerId != null) {
			const promise = Promise.race([
				this.program.provider.connection.removeAccountChangeListener(
					this.listenerId
				),
				new Promise((_, reject) =>
					setTimeout(
						() =>
							reject(
								new Error(
									`Unsubscribe timeout for account ${this.logAccountName}`
								)
							),
						10000
					)
				),
			])
				.then(() => {
					this.listenerId = undefined;
					this.isUnsubscribing = false;
				})
				.catch((error) => {
					console.error(
						`[${this.logAccountName}] Unsubscribe failed, forcing cleanup - listenerId=${this.listenerId}, isUnsubscribing=${this.isUnsubscribing}`,
						error
					);
					this.listenerId = undefined;
					this.isUnsubscribing = false;
				});
			return promise;
		} else {
			this.isUnsubscribing = false;
		}
	}
}