1 files changed, 121 insertions, 0 deletions
diff --git a/packages/internal-helpers/src/path.ts b/packages/internal-helpers/src/path.ts
new file mode 100644
index 000000000..c7dda9d89
--- /dev/null
+++ b/packages/internal-helpers/src/path.ts
@@ -0,0 +1,121 @@
+/**
+ * A set of common path utilities commonly used through the Astro core and integration
+ * projects. These do things like ensure a forward slash prepends paths.
+ */
+
+export function appendExtension(path: string, extension: string) {
+	return path + '.' + extension;
+}
+
+export function appendForwardSlash(path: string) {
+	return path.endsWith('/') ? path : path + '/';
+}
+
+export function prependForwardSlash(path: string) {
+	return path[0] === '/' ? path : '/' + path;
+}
+
+export function collapseDuplicateSlashes(path: string) {
+	return path.replace(/(?<!:)\/{2,}/g, '/');
+}
+
+export const MANY_TRAILING_SLASHES = /\/{2,}$/g;
+
+export function collapseDuplicateTrailingSlashes(path: string, trailingSlash: boolean) {
+	if (!path) {
+		return path;
+	}
+	return path.replace(MANY_TRAILING_SLASHES, trailingSlash ? '/' : '') || '/';
+}
+
+export function removeTrailingForwardSlash(path: string) {
+	return path.endsWith('/') ? path.slice(0, path.length - 1) : path;
+}
+
+export function removeLeadingForwardSlash(path: string) {
+	return path.startsWith('/') ? path.substring(1) : path;
+}
+
+export function removeLeadingForwardSlashWindows(path: string) {
+	return path.startsWith('/') && path[2] === ':' ? path.substring(1) : path;
+}
+
+export function trimSlashes(path: string) {
+	return path.replace(/^\/|\/$/g, '');
+}
+
+export function startsWithForwardSlash(path: string) {
+	return path[0] === '/';
+}
+
+export function startsWithDotDotSlash(path: string) {
+	const c1 = path[0];
+	const c2 = path[1];
+	const c3 = path[2];
+	return c1 === '.' && c2 === '.' && c3 === '/';
+}
+
+export function startsWithDotSlash(path: string) {
+	const c1 = path[0];
+	const c2 = path[1];
+	return c1 === '.' && c2 === '/';
+}
+
+export function isRelativePath(path: string) {
+	return startsWithDotDotSlash(path) || startsWithDotSlash(path);
+}
+
+function isString(path: unknown): path is string {
+	return typeof path === 'string' || path instanceof String;
+}
+
+export function joinPaths(...paths: (string | undefined)[]) {
+	return paths
+		.filter(isString)
+		.map((path, i) => {
+			if (i === 0) {
+				return removeTrailingForwardSlash(path);
+			} else if (i === paths.length - 1) {
+				return removeLeadingForwardSlash(path);
+			} else {
+				return trimSlashes(path);
+			}
+		})
+		.join('/');
+}
+
+export function removeFileExtension(path: string) {
+	let idx = path.lastIndexOf('.');
+	return idx === -1 ? path : path.slice(0, idx);
+}
+
+export function removeQueryString(path: string) {
+	const index = path.lastIndexOf('?');
+	return index > 0 ? path.substring(0, index) : path;
+}
+
+export function isRemotePath(src: string) {
+	return /^(?:http|ftp|https|ws):?\/\//.test(src) || src.startsWith('data:');
+}
+
+export function slash(path: string) {
+	return path.replace(/\\/g, '/');
+}
+
+export function fileExtension(path: string) {
+	const ext = path.split('.').pop();
+	return ext !== path ? `.${ext}` : '';
+}
+
+export function removeBase(path: string, base: string) {
+	if (path.startsWith(base)) {
+		return path.slice(removeTrailingForwardSlash(base).length);
+	}
+	return path;
+}
+
+const WITH_FILE_EXT = /\/[^/]+\.\w+$/;
+
+export function hasFileExtension(path: string) {
+	return WITH_FILE_EXT.test(path);
+}