/**
 * Battle Simulator runner.
 * Pokemon Showdown - http://pokemonshowdown.com/
 *
 * @license MIT
 */

import { strict as assert } from 'assert';
import * as fs from 'fs';

import { Dex } from '..';
import { type ObjectReadWriteStream } from '../../lib/streams';
import { Battle } from '../battle';
import * as BattleStreams from '../battle-stream';
import { State } from '../state';
import { PRNG, type PRNGSeed } from '../prng';
import { RandomPlayerAI } from './random-player-ai';

export interface AIOptions {
	createAI: (stream: ObjectReadWriteStream<string>, options: AIOptions) => RandomPlayerAI;
	move?: number;
	mega?: number;
	seed?: PRNG | PRNGSeed | null;
	team?: PokemonSet[];
}

export interface RunnerOptions {
	format: string;
	prng?: PRNG | PRNGSeed | null;
	p1options?: AIOptions;
	p2options?: AIOptions;
	p3options?: AIOptions;
	p4options?: AIOptions;
	input?: boolean;
	output?: boolean;
	error?: boolean;
	dual?: boolean | 'debug';
}

export class Runner {
	static readonly AI_OPTIONS: AIOptions = {
		createAI: (s: ObjectReadWriteStream<string>, o: AIOptions) => new RandomPlayerAI(s, o),
		move: 0.7,
		mega: 0.6,
	};

	private readonly prng: PRNG;
	private readonly p1options: AIOptions;
	private readonly p2options: AIOptions;
	private readonly p3options: AIOptions;
	private readonly p4options: AIOptions;
	private readonly format: string;
	private readonly input: boolean;
	private readonly output: boolean;
	private readonly error: boolean;
	private readonly dual: boolean | 'debug';

	constructor(options: RunnerOptions) {
		this.format = options.format;

		this.prng = PRNG.get(options.prng);
		this.p1options = { ...Runner.AI_OPTIONS, ...options.p1options };
		this.p2options = { ...Runner.AI_OPTIONS, ...options.p2options };
		this.p3options = { ...Runner.AI_OPTIONS, ...options.p3options };
		this.p4options = { ...Runner.AI_OPTIONS, ...options.p4options };

		this.input = !!options.input;
		this.output = !!options.output;
		this.error = !!options.error;
		this.dual = options.dual || false;
	}

	async run() {
		const battleStream = this.dual ?
			new DualStream(this.input, this.dual === 'debug') :
			new RawBattleStream(this.input);
		const game = this.runGame(this.format, battleStream);
		if (!this.error) return game;
		return game.catch(err => {
			console.log(`\n${battleStream.rawInputLog.join('\n')}\n`);
			throw err;
		});
	}

	private async runGame(format: string, battleStream: RawBattleStream | DualStream) {
		// @ts-expect-error - DualStream implements everything relevant from BattleStream.
		const streams = BattleStreams.getPlayerStreams(battleStream);
		const spec = { formatid: format, seed: this.prng.getSeed() };
		const is4P = Dex.formats.get(format).playerCount > 2;
		const p1spec = this.getPlayerSpec("Bot 1", this.p1options);
		const p2spec = this.getPlayerSpec("Bot 2", this.p2options);
		let p3spec: typeof p1spec, p4spec: typeof p1spec;
		if (is4P) {
			p3spec = this.getPlayerSpec("Bot 3", this.p3options);
			p4spec = this.getPlayerSpec("Bot 4", this.p4options);
		}

		const p1 = this.p1options.createAI(
			streams.p1, { seed: this.newSeed(), ...this.p1options }
		);
		const p2 = this.p2options.createAI(
			streams.p2, { seed: this.newSeed(), ...this.p2options }
		);
		let p3: RandomPlayerAI, p4: RandomPlayerAI;
		if (is4P) {
			p3 = this.p4options.createAI(
				streams.p3, { seed: this.newSeed(), ...this.p3options }
			);
			p4 = this.p4options.createAI(
				streams.p4, { seed: this.newSeed(), ...this.p4options }
			);
		}
		// TODO: Use `await Promise.race([streams.omniscient.read(), p1, p2])` to avoid
		// leaving these promises dangling once it no longer causes memory leaks (v8#9069).
		void p1.start();
		void p2.start();
		if (is4P) {
			void p3!.start();
			void p4!.start();
		}

		let initMessage = `>start ${JSON.stringify(spec)}\n` +
			`>player p1 ${JSON.stringify(p1spec)}\n` +
			`>player p2 ${JSON.stringify(p2spec)}`;
		if (is4P) {
			initMessage += `\n` +
				`>player p3 ${JSON.stringify(p3spec!)}\n` +
				`>player p4 ${JSON.stringify(p4spec!)}`;
		}
		void streams.omniscient.write(initMessage);

		for await (const chunk of streams.omniscient) {
			if (this.output) console.log(chunk);
		}
		return streams.omniscient.writeEnd();
	}

	// Same as PRNG#generatedSeed, only deterministic.
	// NOTE: advances this.prng's seed by 4.
	private newSeed(): PRNGSeed {
		return [
			this.prng.random(2 ** 16),
			this.prng.random(2 ** 16),
			this.prng.random(2 ** 16),
			this.prng.random(2 ** 16),
		].join(',') as PRNGSeed;
	}

	private getPlayerSpec(name: string, options: AIOptions) {
		if (options.team) return { name, team: options.team };
		return { name, seed: this.newSeed() };
	}
}

class RawBattleStream extends BattleStreams.BattleStream {
	readonly rawInputLog: string[];

	private readonly input: boolean;

	constructor(input: boolean) {
		super();
		this.input = !!input;
		this.rawInputLog = [];
	}

	_write(message: string) {
		if (this.input) console.log(message);
		this.rawInputLog.push(message);
		super._write(message);
	}
}

class DualStream {
	private debug: boolean;
	private readonly control: RawBattleStream;
	private test: RawBattleStream;

	constructor(input: boolean, debug: boolean) {
		this.debug = debug;
		// The input to both streams should be the same, so to satisfy the
		// input flag we only need to track the raw input of one stream.
		this.control = new RawBattleStream(input);
		this.test = new RawBattleStream(false);
	}

	get rawInputLog() {
		const control = this.control.rawInputLog;
		const test = this.test.rawInputLog;
		assert.deepEqual(test, control);
		return control;
	}

	async read() {
		const control = await this.control.read();
		const test = await this.test.read();
		// In debug mode, wait to catch this as a difference in the inputLog
		// and error there so we get the full battle state dumped instead.
		if (!this.debug) assert.equal(State.normalizeLog(test), State.normalizeLog(control));
		return control;
	}

	write(message: string) {
		this.control._write(message);
		this.test._write(message);
		this.compare();
	}

	writeEnd() {
		// We need to compare first because _writeEnd() destroys the battle object.
		this.compare(true);
		this.control._writeEnd();
		this.test._writeEnd();
	}

	compare(end?: boolean) {
		if (!this.control.battle || !this.test.battle) return;

		const control = this.control.battle.toJSON();
		const test = this.test.battle.toJSON();
		try {
			assert.deepEqual(State.normalize(test), State.normalize(control));
		} catch (err: any) {
			if (this.debug) {
				// NOTE: diffing these directly won't work because the key ordering isn't stable.
				fs.writeFileSync('logs/control.json', JSON.stringify(control, null, 2));
				fs.writeFileSync('logs/test.json', JSON.stringify(test, null, 2));
			}
			throw new Error(err.message);
		}

		if (end) return;
		const send = this.test.battle.send;
		this.test.battle = Battle.fromJSON(test);
		this.test.battle.restart(send);
	}
}