From c31cd2b30abec479054931e6240a74eec9a1ac97 Mon Sep 17 00:00:00 2001
From: Arne van Iterson <arne@arnweb.nl>
Date: Mon, 23 Mar 2020 19:18:30 +0100
Subject: [PATCH] Added some utilites for collision detection

---
 lib/TileMap.js               | 14 ++++++++++
 lib/movement/deadInTracks.js | 16 +++++++++++
 lib/movement/wallslide.js    | 51 ++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+)
 create mode 100644 lib/movement/deadInTracks.js
 create mode 100644 lib/movement/wallslide.js

diff --git a/lib/TileMap.js b/lib/TileMap.js
index 7900999..5fd50ca 100644
--- a/lib/TileMap.js
+++ b/lib/TileMap.js
@@ -54,6 +54,20 @@ class TileMap extends Container {
 	setFrameAtPixelPos(pos, frame) {
 		return this.setFrameAtMapPos(this.pixelToMapPos(pos), frame);
 	}
+
+	tilesAtCorners(bounds, xo = 0, yo = 0) {
+		return [
+			[bounds.x, bounds.y], // Top-left
+			[bounds.x + bounds.w, bounds.y], // Top-right
+			[bounds.x, bounds.y + bounds.h], // Bottom-left
+			[bounds.x + bounds.w, bounds.y + bounds.h] // Bottom-right
+		].map(([x, y]) =>
+			this.tileAtPixelPos({
+				x: x + xo,
+				y: y + yo
+			})
+		);
+	}
 }
 
 module.exports = TileMap;
\ No newline at end of file
diff --git a/lib/movement/deadInTracks.js b/lib/movement/deadInTracks.js
new file mode 100644
index 0000000..cc51fbf
--- /dev/null
+++ b/lib/movement/deadInTracks.js
@@ -0,0 +1,16 @@
+const entity = require("../utilities/entity");
+
+function deadInTracks(ent, map, x = 0, y = 0) {
+	const bounds = entity.bounds(ent);
+	const tiles = map.tilesAtCorners(bounds, x, y);
+	const walks = tiles.map(t => t && t.frame.walkable);
+	const blocked = walks.some(w => !w);
+	if (blocked) {
+		x = 0,
+		y = 0;
+	}
+	return { x, y };
+}
+module.exports = {
+	deadInTracks
+};
\ No newline at end of file
diff --git a/lib/movement/wallslide.js b/lib/movement/wallslide.js
new file mode 100644
index 0000000..ad00cab
--- /dev/null
+++ b/lib/movement/wallslide.js
@@ -0,0 +1,51 @@
+const entity = require("../utils/entity.js");
+
+function wallslide(ent, map, x = 0, y = 0) {
+	let tiles;
+	let tileEdge;
+	const bounds = entity.bounds(ent);
+
+	// Final amounts of movement to allow
+	let xo = x;
+	let yo = y;
+
+	// Check vertical movement
+	if (y !== 0) {
+		tiles = map.tilesAtCorners(bounds, 0, yo);
+		const [tl, tr, bl, br] = tiles.map(t => t && t.frame.walkable);
+
+		// Hit your head
+		if (y < 0 && !(tl && tr)) {
+			tileEdge = tiles[0].pos.y + tiles[0].h;
+			yo = tileEdge - bounds.y;
+		}
+		// Hit your feet
+		if (y > 0 && !(bl && br)) {
+			tileEdge = tiles[2].pos.y - 1;
+			yo = tileEdge - (bounds.y + bounds.h);
+		}
+	}
+
+	// Check horizontal movement
+	if (x !== 0) {
+		tiles = map.tilesAtCorners(bounds, xo, yo);
+		const [tl, tr, bl, br] = tiles.map(t => t && t.frame.walkable);
+
+		// Hit left edge
+		if (x < 0 && !(tl && bl)) {
+			tileEdge = tiles[0].pos.x + tiles[0].w;
+			xo = tileEdge - bounds.x;
+		}
+		// Hit right edge
+		if (x > 0 && !(tr && br)) {
+			tileEdge = tiles[1].pos.x - 1;
+			xo = tileEdge - (bounds.x + bounds.w);
+		}
+	}
+	// xo & yo contain the amount we're allowed to move by.
+	return { x: xo, y: yo };
+}
+
+module.exports = {
+	wallslide
+};
\ No newline at end of file