From 6d0d434d8cf63f3c7840e589241a08f58f3d20f2 Mon Sep 17 00:00:00 2001
From: Mario Zechner <badlogicgames@gmail.com>
Date: Sat, 24 Jan 2026 00:35:33 +0100
Subject: [PATCH] Add /diff extension for VS Code diff view

---
 .pi/extensions/diff.ts | 167 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 167 insertions(+)
 create mode 100644 .pi/extensions/diff.ts

diff --git a/.pi/extensions/diff.ts b/.pi/extensions/diff.ts
new file mode 100644
index 00000000..cdda4762
--- /dev/null
+++ b/.pi/extensions/diff.ts
@@ -0,0 +1,167 @@
+/**
+ * Diff Extension
+ *
+ * /diff command shows modified/deleted/new files from git status and opens
+ * the selected file in VS Code's diff view.
+ */
+
+import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";
+import { DynamicBorder } from "@mariozechner/pi-coding-agent";
+import { Container, Key, matchesKey, type SelectItem, SelectList, Text } from "@mariozechner/pi-tui";
+
+interface FileInfo {
+	status: string;
+	statusLabel: string;
+	file: string;
+}
+
+export default function (pi: ExtensionAPI) {
+	pi.registerCommand("diff", {
+		description: "Show git changes and open in VS Code diff view",
+		handler: async (_args, ctx) => {
+			if (!ctx.hasUI) {
+				ctx.ui.notify("No UI available", "error");
+				return;
+			}
+
+			// Get changed files from git status
+			const result = await pi.exec("git", ["status", "--porcelain"], { cwd: ctx.cwd });
+
+			if (result.code !== 0) {
+				ctx.ui.notify(`git status failed: ${result.stderr}`, "error");
+				return;
+			}
+
+			if (!result.stdout || !result.stdout.trim()) {
+				ctx.ui.notify("No changes in working tree", "info");
+				return;
+			}
+
+			// Parse git status output
+			// Format: XY filename (where XY is two-letter status, then space, then filename)
+			const lines = result.stdout.split("\n");
+			const files: FileInfo[] = [];
+
+			for (const line of lines) {
+				if (line.length < 4) continue; // Need at least "XY f"
+
+				const status = line.slice(0, 2);
+				const file = line.slice(2).trimStart();
+
+				// Translate status codes to short labels
+				let statusLabel: string;
+				if (status.includes("M")) statusLabel = "M";
+				else if (status.includes("A")) statusLabel = "A";
+				else if (status.includes("D")) statusLabel = "D";
+				else if (status.includes("?")) statusLabel = "?";
+				else if (status.includes("R")) statusLabel = "R";
+				else if (status.includes("C")) statusLabel = "C";
+				else statusLabel = status.trim() || "~";
+
+				files.push({ status: statusLabel, statusLabel, file });
+			}
+
+			if (files.length === 0) {
+				ctx.ui.notify("No changes found", "info");
+				return;
+			}
+
+			// Show file picker with SelectList
+			const selected = await ctx.ui.custom<FileInfo | null>((tui, theme, _kb, done) => {
+				const container = new Container();
+
+				// Top border
+				container.addChild(new DynamicBorder((s: string) => theme.fg("accent", s)));
+
+				// Title
+				container.addChild(new Text(theme.fg("accent", theme.bold(" Select file to diff")), 0, 0));
+
+				// Build select items with colored status
+				const items: SelectItem[] = files.map((f) => {
+					let statusColor: string;
+					switch (f.status) {
+						case "M":
+							statusColor = theme.fg("warning", f.status);
+							break;
+						case "A":
+							statusColor = theme.fg("success", f.status);
+							break;
+						case "D":
+							statusColor = theme.fg("error", f.status);
+							break;
+						case "?":
+							statusColor = theme.fg("muted", f.status);
+							break;
+						default:
+							statusColor = theme.fg("dim", f.status);
+					}
+					return {
+						value: f,
+						label: `${statusColor} ${f.file}`,
+					};
+				});
+
+				const visibleRows = Math.min(files.length, 15);
+				let currentIndex = 0;
+
+				const selectList = new SelectList(items, visibleRows, {
+					selectedPrefix: (t) => theme.fg("accent", t),
+					selectedText: (t) => t, // Keep existing colors
+					description: (t) => theme.fg("muted", t),
+					scrollInfo: (t) => theme.fg("dim", t),
+					noMatch: (t) => theme.fg("warning", t),
+				});
+				selectList.onSelect = (item) => done(item.value as FileInfo);
+				selectList.onCancel = () => done(null);
+				selectList.onSelectionChange = (item) => {
+					currentIndex = items.indexOf(item);
+				};
+				container.addChild(selectList);
+
+				// Help text
+				container.addChild(
+					new Text(theme.fg("dim", " ↑↓ navigate • ←→ page • enter select • esc cancel"), 0, 0),
+				);
+
+				// Bottom border
+				container.addChild(new DynamicBorder((s: string) => theme.fg("accent", s)));
+
+				return {
+					render: (w) => container.render(w),
+					invalidate: () => container.invalidate(),
+					handleInput: (data) => {
+						// Add paging with left/right
+						if (matchesKey(data, Key.left)) {
+							// Page up - clamp to 0
+							currentIndex = Math.max(0, currentIndex - visibleRows);
+							selectList.setSelectedIndex(currentIndex);
+						} else if (matchesKey(data, Key.right)) {
+							// Page down - clamp to last
+							currentIndex = Math.min(items.length - 1, currentIndex + visibleRows);
+							selectList.setSelectedIndex(currentIndex);
+						} else {
+							selectList.handleInput(data);
+						}
+						tui.requestRender();
+					},
+				};
+			});
+
+			if (!selected) return;
+
+			// Open in VS Code diff view (this will block until VS Code is closed)
+			// For untracked files, git difftool won't work, so fall back to just opening the file
+			if (selected.status === "?") {
+				await pi.exec("code", ["-g", selected.file], { cwd: ctx.cwd });
+			} else {
+				const diffResult = await pi.exec("git", ["difftool", "-y", "--tool=vscode", selected.file], {
+					cwd: ctx.cwd,
+				});
+				// Fallback if difftool fails
+				if (diffResult.code !== 0) {
+					await pi.exec("code", ["-g", selected.file], { cwd: ctx.cwd });
+				}
+			}
+		},
+	});
+}