From 3f1326ebd006e21a66c438a4515e4d83f85c8c52 Mon Sep 17 00:00:00 2001
From: "Timothy J. Warren" <tim@timshome.page>
Date: Fri, 10 Nov 2023 19:17:36 -0500
Subject: [PATCH] Add PageUp, PageDown, Home, and End input handling

---
 src/common/editor/ansi.ts   |  4 ++++
 src/common/editor/editor.ts | 38 +++++++++++++++++++++++++++++++++----
 src/scroll.ts               | 30 ++++++++++++++++++++++++++++-
 3 files changed, 67 insertions(+), 5 deletions(-)

diff --git a/src/common/editor/ansi.ts b/src/common/editor/ansi.ts
index 5520a32..f46f649 100644
--- a/src/common/editor/ansi.ts
+++ b/src/common/editor/ansi.ts
@@ -12,6 +12,10 @@ export enum KeyCommand {
 	ArrowDown = `${ANSI_PREFIX}B`,
 	ArrowRight = `${ANSI_PREFIX}C`,
 	ArrowLeft = `${ANSI_PREFIX}D`,
+	PageUp = `${ANSI_PREFIX}5~`,
+	PageDown = `${ANSI_PREFIX}6~`,
+	Home = 'LineHome',
+	End = 'LineEnd',
 }
 
 export const Ansi = {
diff --git a/src/common/editor/editor.ts b/src/common/editor/editor.ts
index da5c76e..e2288ed 100644
--- a/src/common/editor/editor.ts
+++ b/src/common/editor/editor.ts
@@ -29,6 +29,28 @@ export class Editor {
 				this.clearScreen().then(() => {});
 				return false;
 
+			case KeyCommand.Home:
+				this.#cursor.x = 0;
+				break;
+
+			case KeyCommand.End:
+				this.#cursor.x = this.#screen.cols - 1;
+				break;
+
+			case KeyCommand.PageUp:
+			case KeyCommand.PageDown:
+				{
+					let times = this.#screen.rows;
+					while (times--) {
+						this.moveCursor(
+							input === KeyCommand.PageUp
+								? KeyCommand.ArrowUp
+								: KeyCommand.ArrowDown,
+						);
+					}
+				}
+				break;
+
 			case KeyCommand.ArrowUp:
 			case KeyCommand.ArrowDown:
 			case KeyCommand.ArrowRight:
@@ -43,16 +65,24 @@ export class Editor {
 	private moveCursor(char: string): void {
 		switch (char) {
 			case KeyCommand.ArrowLeft:
-				this.#cursor.x--;
+				if (this.#cursor.x > 0) {
+					this.#cursor.x--;
+				}
 				break;
 			case KeyCommand.ArrowRight:
-				this.#cursor.x++;
+				if (this.#cursor.x < this.#screen.cols) {
+					this.#cursor.x++;
+				}
 				break;
 			case KeyCommand.ArrowUp:
-				this.#cursor.y--;
+				if (this.#cursor.y > 0) {
+					this.#cursor.y--;
+				}
 				break;
 			case KeyCommand.ArrowDown:
-				this.#cursor.y++;
+				if (this.#cursor.y < this.#screen.rows) {
+					this.#cursor.y++;
+				}
 				break;
 		}
 	}
diff --git a/src/scroll.ts b/src/scroll.ts
index 9c6f5de..0101a56 100644
--- a/src/scroll.ts
+++ b/src/scroll.ts
@@ -2,9 +2,37 @@
  * The starting point for running scroll
  */
 import { Editor, getRuntime, getTermios } from './common/mod.ts';
+import { KeyCommand } from './common/editor/ansi.ts';
 
 const decoder = new TextDecoder();
 
+function readKey(raw: Uint8Array): string {
+	const parsed = decoder.decode(raw);
+
+	// Return the input if it's unambiguous
+	if (parsed in KeyCommand) {
+		return parsed;
+	}
+
+	// Some keycodes have multiple potential inputs
+	switch (parsed) {
+		case '\x1bOH':
+		case '\x1b[7~':
+		case '\x1b[1~':
+		case '\x1b[H':
+			return KeyCommand.Home;
+
+		case '\x1bOF':
+		case '\x1b[8~':
+		case '\x1b[4~':
+		case '\x1b[F':
+			return KeyCommand.End;
+
+		default:
+			return parsed;
+	}
+}
+
 export async function main() {
 	const runTime = await getRuntime();
 	const { io, onExit } = runTime;
@@ -25,7 +53,7 @@ export async function main() {
 	// The main event loop
 	for await (const chunk of io.inputLoop()) {
 		// Process input
-		const char = String(decoder.decode(chunk));
+		const char = readKey(chunk);
 		const shouldLoop = editor.processKeyPress(char);
 		if (!shouldLoop) {
 			return 0;