Meta: improve GitHub URL parser (#3138)

1 files changed, 71 insertions, 0 deletions

diff --git a/source/github-helpers/github-url.ts b/source/github-helpers/github-url.ts
new file mode 100644
index 00000000..395723d4
--- /dev/null
+++ b/source/github-helpers/github-url.ts
@@ -0,0 +1,71 @@
+import {getCurrentBranch} from '.';
+
+function disambiguateReference(ambiguousReference: string[]): {branch: string; filePath: string} {
+	const branch = ambiguousReference[0];
+	const filePath = ambiguousReference.slice(1).join('/');
+
+	const currentBranch = getCurrentBranch();
+	const currentBranchSections = currentBranch.split('/');
+	if (
+		ambiguousReference.length === 1 || // Ref has no slashes
+		currentBranchSections.length === 1 || // Current branch has no slashes
+		/\^|~|@{/.test(branch) // Ref is an extended revision #3137 https://git-scm.com/docs/git-rev-parse#_specifying_revisions
+	) {
+		// Then the reference is not ambiguous
+		return {branch, filePath};
+	}
+
+	for (const [i, section] of currentBranchSections.entries()) {
+		if (ambiguousReference[i] !== section) {
+			console.warn(`The supplied path (${ambiguousReference.join('/')}) is ambiguous (current reference is \`${currentBranch}\`)`);
+			return {branch, filePath};
+		}
+	}
+
+	return {
+		branch: currentBranch,
+		filePath: ambiguousReference.slice(currentBranchSections.length).join('/')
+	};
+}
+
+export default class GitHubURL extends URL {
+	// @ts-ignore https://github.com/microsoft/TypeScript/issues/26792
+	user: string;
+	// @ts-ignore
+	repository: string;
+	// @ts-ignore
+	route: string;
+	// @ts-ignore
+	branch: string;
+	// @ts-ignore
+	filePath: string;
+	constructor(url: string) {
+		super(url);
+		this.pathname = super.pathname;
+	}
+
+	assign(replacements: Partial<GitHubURL>): this {
+		Object.assign(this, replacements);
+		return this;
+	}
+
+	get pathname() {
+		return `/${this.user}/${this.repository}/${this.route}/${this.branch}/${this.filePath}`.replace(/\/+$/, '');
+	}
+
+	set pathname(pathname) {
+		const [user, repository, route, ...ambiguousReference] = pathname.replace(/^\/|\/$/g, '').split('/');
+		const {branch, filePath} = disambiguateReference(ambiguousReference);
+		this.assign({user, repository, route, branch, filePath});
+	}
+
+	get href() {
+		// Update the actual underlying URL
+		super.pathname = this.pathname;
+		return super.href;
+	}
+
+	toString() {
+		return this.href;
+	}
+}