From ff423fe3ba1d65c1ae637fb586b168b9e29d8d13 Mon Sep 17 00:00:00 2001
From: Dave <david.els1@outlook.com>
Date: Wed, 16 Sep 2026 11:45:15 +0200
Subject: [PATCH] feat(git): strict conventional-commit parsing

---
 src/lib/git/conventional.test.ts | 88 ++++++++++++++++++++++++++++++++
 src/lib/git/conventional.ts      | 53 +++++++++++++++++++
 2 files changed, 141 insertions(+)
 create mode 100644 src/lib/git/conventional.test.ts
 create mode 100644 src/lib/git/conventional.ts

diff --git a/src/lib/git/conventional.test.ts b/src/lib/git/conventional.test.ts
new file mode 100644
index 0000000..7aa5523
--- /dev/null
+++ b/src/lib/git/conventional.test.ts
@@ -0,0 +1,88 @@
+import { describe, it, expect } from "vitest";
+import { parseCommitMessage } from "@/lib/git/conventional";
+
+describe("parseCommitMessage", () => {
+  it("pulls out type, scope and subject", () => {
+    expect(parseCommitMessage("feat(stock): inline qty editing")).toEqual({
+      type: "feat",
+      scope: "stock",
+      subject: "inline qty editing",
+      breaking: false,
+    });
+  });
+
+  it("handles a missing scope", () => {
+    expect(parseCommitMessage("fix: correct the total")).toEqual({
+      type: "fix",
+      scope: "",
+      subject: "correct the total",
+      breaking: false,
+    });
+  });
+
+  it("flags a breaking change with and without a scope", () => {
+    expect(parseCommitMessage("feat!: drop v1 API").breaking).toBe(true);
+    expect(parseCommitMessage("feat(api)!: drop v1").breaking).toBe(true);
+    expect(parseCommitMessage("feat(api)!: drop v1").scope).toBe("api");
+  });
+
+  it("reads only the first line", () => {
+    const message =
+      "feat(customers): lift the toggle\n\nA long body that\nmentions fix(other): things\n";
+    expect(parseCommitMessage(message)).toEqual({
+      type: "feat",
+      scope: "customers",
+      subject: "lift the toggle",
+      breaking: false,
+    });
+  });
+
+  it("lowercases the type and the scope", () => {
+    const parsed = parseCommitMessage("Feat(Stock): thing");
+    expect(parsed.type).toBe("feat");
+    expect(parsed.scope).toBe("stock");
+  });
+
+  it("classifies an unparseable message as other, keeping the subject", () => {
+    expect(parseCommitMessage("just some words")).toEqual({
+      type: "other",
+      scope: "",
+      subject: "just some words",
+      breaking: false,
+    });
+  });
+
+  it("does not accept a space before the parenthesis", () => {
+    // "feat (stock): x" is not a conventional commit. Accepting it would make
+    // the scope breakdown depend on invisible whitespace.
+    expect(parseCommitMessage("feat (stock): x").type).toBe("other");
+  });
+
+  it("accepts any single lowercase word as a type, but not a phrase", () => {
+    // "note" is not a conventional type, but the parser cannot tell an unknown
+    // type from prose shaped like one, and it must not police a whitelist —
+    // see the note after Step 4.
+    expect(parseCommitMessage("note: this is not conventional").type).toBe("note");
+    // A space before the colon means it is a sentence, not a prefix.
+    expect(parseCommitMessage("TODO tomorrow: finish").type).toBe("other");
+  });
+
+  it("rejects a type containing non-letters", () => {
+    expect(parseCommitMessage("feat2(x): thing").type).toBe("other");
+  });
+
+  it("trims and caps an over-long subject", () => {
+    const parsed = parseCommitMessage(`feat(x):    ${"s".repeat(400)}`);
+    expect(parsed.subject).toHaveLength(200);
+  });
+
+  it("returns other for an empty message", () => {
+    expect(parseCommitMessage("").type).toBe("other");
+    expect(parseCommitMessage("   \n  ").subject).toBe("");
+  });
+
+  it("handles a scope containing a hyphen or slash", () => {
+    expect(parseCommitMessage("fix(delivery-notes): x").scope).toBe("delivery-notes");
+    expect(parseCommitMessage("fix(api/v1): x").scope).toBe("api/v1");
+  });
+});
\ No newline at end of file
diff --git a/src/lib/git/conventional.ts b/src/lib/git/conventional.ts
new file mode 100644
index 0000000..0bbb3f4
--- /dev/null
+++ b/src/lib/git/conventional.ts
@@ -0,0 +1,53 @@
+/**
+ * Conventional-commit parsing.
+ *
+ * Two dashboard figures depend on this — the type breakdown and the feature
+ * areas by scope — and Plan 2b links commits to cards by scope. So the rule
+ * has to be strict and predictable rather than forgiving: a parser that
+ * sometimes accepts "feat (stock):" makes the scope chart depend on invisible
+ * whitespace, and nobody would ever find that.
+ *
+ * Anything that does not match is type "other" and is counted, never dropped.
+ * A silently shrinking denominator is worse than an untidy bar.
+ */
+
+export interface ParsedCommit {
+  /** Lowercased conventional type, or "other". */
+  type: string;
+  /** Lowercased scope, or "" when absent. */
+  scope: string;
+  /** First line after the prefix, trimmed and capped. */
+  subject: string;
+  breaking: boolean;
+}
+
+export const MAX_SUBJECT_LENGTH = 200;
+
+/**
+ * type, optional (scope), optional !, colon, space.
+ * The type is letters only — "feat2" is not a type, it is prose.
+ */
+const CONVENTIONAL = /^([a-zA-Z]+)(?:\(([^)]+)\))?(!?):\s+(.*)$/;
+
+export function parseCommitMessage(message: string): ParsedCommit {
+  const firstLine = (message ?? "").split("\n")[0].trim();
+
+  const match = CONVENTIONAL.exec(firstLine);
+  if (!match) {
+    return {
+      type: "other",
+      scope: "",
+      subject: firstLine.slice(0, MAX_SUBJECT_LENGTH),
+      breaking: false,
+    };
+  }
+
+  const [, type, scope, bang, subject] = match;
+
+  return {
+    type: type.toLowerCase(),
+    scope: (scope ?? "").toLowerCase().trim(),
+    subject: subject.trim().slice(0, MAX_SUBJECT_LENGTH),
+    breaking: bang === "!",
+  };
+}
\ No newline at end of file