feat: add support for multiple followers (with option for stack/chain) (

#170)

adds support for multiple followers, with an option for whether to stack (keep all followers one step behind player) or chain (keep followers one step behind the follower ahead of them in the list of active followers)

also fixes an issue in the hack options injection regex in the test code

BREAKING CHANGE: this changes the `follower` export to `followers`, since it's now a list

src/follower.js

@@ -57,15 +57,25 @@ import {
 
 export var hackOptions = {
 	allowFollowerCollision: false, // if true, the player can walk into the follower and talk to them (possible to get stuck this way)
-	follower: 'a', // id or name of sprite to be the follower; use '' to start without a follower
+	followers: ['a'], // ids or names of sprites to be followers; use [] to start without a follower
 	delay: 200, // delay between each follower step (0 is immediate, 400 is twice as slow as normal)
+	stack: false, // if true, followers stack on top of each other; otherwise, they will form a chain
 };
 
-export var follower;
+export var followers = [];
 var paths = {};
 
 function setFollower(followerName) {
-	follower = followerName && getImage(followerName, bitsy.sprite);
+	var follower = followerName && getImage(followerName, bitsy.sprite);
+	if (!follower) {
+		throw new Error('Failed to find sprite with id/name "' + followerName + '"');
+	}
+	var idx = followers.indexOf(follower);
+	if (idx > 0) {
+		followers.splice(idx, 1);
+	} else {
+		followers.push(follower);
+	}
 	paths[follower.id] = paths[follower.id] || [];
 	takeStep();
 }
@@ -78,22 +88,28 @@ function takeStep() {
 	}
 	walking = true;
 	setTimeout(() => {
-		var path = paths[follower.id];
-		var point = path.shift();
-		if (point) {
-			follower.x = point.x;
-			follower.y = point.y;
-			follower.room = point.room;
-		}
-		walking = false;
-		if (path.length) {
+		let takeAnother = false;
+		followers.forEach(function (follower) {
+			var path = paths[follower.id];
+			var point = path.shift();
+			if (point) {
+				follower.x = point.x;
+				follower.y = point.y;
+				follower.room = point.room;
+			}
+			walking = false;
+			if (path.length) {
+				takeAnother = true;
+			}
+		});
+		if (takeAnother) {
 			takeStep();
 		}
 	}, hackOptions.delay);
 }
 
 after('startExportedGame', function () {
-	setFollower(hackOptions.follower);
+	hackOptions.followers.forEach(setFollower);
 
 	// remove + add player to sprite list to force rendering them on top of follower
 	var p = bitsy.sprite[bitsy.playerId];
@@ -119,7 +135,7 @@ after('update', function () {
 		return;
 	}
 
-	if (!follower) {
+	if (!followers.length) {
 		return;
 	}
 
@@ -146,25 +162,41 @@ after('update', function () {
 	default:
 		break;
 	}
-	paths[follower.id].push(step);
+	followers.forEach(function (follower, idx) {
+		if (idx === 0 || hackOptions.stack) {
+			paths[follower.id].push(step);
+		} else {
+			var prevFollower = followers[idx - 1];
+			var prev = paths[prevFollower.id];
+			paths[follower.id].push(prev[prev.length - 2] || {
+				x: prevFollower.x,
+				y: prevFollower.y,
+				room: prevFollower.room,
+			});
+		}
+	});
 	takeStep();
 });
 
 // make follower walk "through" exits
 before('movePlayerThroughExit', function (exit) {
-	if (follower) {
+	if (followers.length) {
 		movedFollower = true;
-		paths[follower.id].push({
-			x: exit.dest.x,
-			y: exit.dest.y,
-			room: exit.dest.room,
+		followers.forEach(function (follower) {
+			paths[follower.id].push({
+				x: exit.dest.x,
+				y: exit.dest.y,
+				room: exit.dest.room,
+			});
 		});
 		takeStep();
 	}
 });
 
 function filterFollowing(id) {
-	return follower === bitsy.sprite[id] ? null : id;
+	return followers.some(function (follower) {
+		return follower.id === id;
+	}) ? null : id;
 }
 
 var originalGetSpriteLeft;
@@ -221,13 +253,13 @@ addDualDialogTag('followerDelay', function (environment, parameters) {
 	hackOptions.delay = parseInt(parameters[0], 10);
 });
 addDualDialogTag('followerSync', function () {
-	if (follower) {
-		var player = bitsy.player();
+	var player = bitsy.player();
+	followers.forEach(function (follower) {
 		follower.room = player.room;
 		follower.x = player.x;
 		follower.y = player.y;
 		paths[follower.id].length = 0;
-	}
+	});
 });
 
 before('moveSprites', function () {

src/follower.test.js

@@ -6,6 +6,83 @@ import {
 	delay,
 } from './test/bitsy';
 
+		snapshot, start
+	} from './test/bitsy';
+
+const multiple = `
+
+# BITSY VERSION 7.2
+
+! ROOM_FORMAT 1
+
+PAL 0
+0,82,204
+128,159,255
+255,255,255
+
+ROOM 0
+0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
+0,a,a,a,a,a,a,a,a,a,a,a,a,a,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,0,0,0,0,0,0,0,0,0,0,0,0,a,0
+0,a,a,a,a,a,a,a,a,a,a,a,a,a,a,0
+0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
+PAL 0
+
+TIL a
+11111111
+10000001
+10000001
+10011001
+10011001
+10000001
+10000001
+11111111
+
+SPR A
+00011000
+00011000
+00011000
+00111100
+01111110
+10111101
+00100100
+00100100
+POS 0 4,12
+
+SPR a
+00000000
+00000000
+00001000
+00011000
+00001000
+00001000
+00011100
+00000000
+POS 0 6,12
+
+SPR b
+00000000
+00000000
+00011000
+00100100
+00001000
+00010000
+00111100
+00000000
+POS 0 8,12
+`;
+
 test('follower', async () => {
 	await start({
 		hacks: ['follower'],
@@ -19,3 +96,36 @@ test('follower', async () => {
 	await snapshot();
 	await end();
 });
+
+test('multiple followers (chain)', async () => {
+	await start({
+		hacks: [['follower', {
+			allowFollowerCollision: false,
+			followers: ['a', 'b'],
+			delay: 1,
+		}]],
+		gamedata: multiple,
+	});
+	await press('ArrowLeft');
+	await snapshot();
+	await press('ArrowLeft');
+	await snapshot();
+	await end();
+});
+
+test('multiple followers (stack)', async () => {
+	await start({
+		hacks: [['follower', {
+			allowFollowerCollision: false,
+			followers: ['a', 'b'],
+			delay: 1,
+			stack: true,
+		}]],
+		gamedata: multiple,
+	});
+	await press('ArrowLeft');
+	await snapshot();
+	await press('ArrowLeft');
+	await snapshot();
+	await end();
+});

src/test/bitsy.js

@@ -48,7 +48,7 @@ export function delay(ms) {
 	return new Promise((r) => setTimeout(r, ms));
 }
 
-// start pupeteer
+// start puppeteer
 // and configure it for testing a bitsy game
 export async function start({
 	gamedata = '',
@@ -80,7 +80,7 @@ export async function start({
 					return `<script>${hackDist[hack.replace(/\s/g, '-')].replace(/\$([0-9]+)/g, '$$$$$1')}</script>`;
 				}
 				const [hackStr, options] = hack;
-				return `<script>${hackDist[hackStr.replace(/\s/g, '-')].replace(/(var hackOptions.*=)[^]*?;/m, `$1 ${JSON.stringify(options, undefined, '\t')};`).replace(/\$([0-9]+)/g, '$$$$$1')}</script>`;
+				return `<script>${hackDist[hackStr.replace(/\s/g, '-')].replace(/(var hackOptions.*=)[^]*?;$/m, `$1 ${JSON.stringify(options, undefined, '\t')};`).replace(/\$([0-9]+)/g, '$$$$$1')}</script>`;
 			}).join('\n')
 		}$2`);
 	}