ai.ts

// Copyright 2023 The Nakama Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

const aiUserId = "ai-user-id";
const tfServingAddress: string= "http://tf:8501/v1/models/ttt:predict";

let aiPresence: nkruntime.Presence = {
	userId: aiUserId,
	sessionId: "",
	username: aiUserId,
	node: "",
}

function aiMessage(code: OpCode, data: ArrayBuffer): nkruntime.MatchMessage {
	return {
		sender: aiPresence,
		persistence: true,
		status: "",
		opCode: code,
		data: data,
		reliable: true,
		receiveTimeMs: Date.now(),
	}
}

type cell = number[];
type row = cell[];
type board = row[];

function aiTurn(state: State, logger: nkruntime.Logger, nk: nkruntime.Nakama) {
	let aiCell = [1, 0];
	let playerCell = [0, 1];
	let undefCell = [0, 0];

	// Convert board state into expected model format
	let b: board = [
		[undefCell, undefCell, undefCell],
		[undefCell, undefCell, undefCell],
		[undefCell, undefCell, undefCell],
	];

	state.board.forEach((mark, idx) => {
		const rowIdx = Math.floor(idx / 3);
		const cellIdx = idx % 3;

		if(mark === state.marks[aiUserId])
			b[rowIdx][cellIdx] = aiCell;
		else if(mark === null || mark === Mark.UNDEFINED)
			b[rowIdx][cellIdx] = undefCell;
		else
			b[rowIdx][cellIdx] = playerCell;
	});

	// Send the vectors to TF
	let headers = { 'Accept': 'application/json' };

	let resp = nk.httpRequest(
		tfServingAddress, 'post', headers, JSON.stringify({ instances: [b] }));

	let body = JSON.parse(resp.body);

	let predictions: number[] = [];
	try {
		predictions = body.predictions[0]
	} catch (error) {
		logger.error("received unexpected TF response: %v: %v", error, body)
		return;
	}

	// Find the index with the highest predicted value
	let maxVal = -Infinity;
	let aiMovePos = -1
	predictions.forEach((val, idx) => {
		if(val > maxVal) {
			maxVal = val;
			aiMovePos = idx;
		}
	});

	// Append message to m.messages to be consumed by the next loop run
	if(aiMovePos > -1) {
		let move = nk.stringToBinary(
			JSON.stringify({position: aiMovePos}));

		state.aiMessage = aiMessage(OpCode.MOVE, move);
	}
}