Initial pass

src/version.js

@@ -0,0 +1,96 @@
+const semver = require("semver");
+const fetch = require("node-fetch");
+
+const GIT_HASH_RE = /^[0-9a-fA-F]{40}$/;
+
+/** 
+ * @typedef VersionRange
+ * @property {string} range
+ * @property {boolean} isCanary
+ */
+
+/** 
+ * @typedef Version
+ * @property {string} version
+ * @property {boolean} isCanary
+ */
+
+/**
+ * Parses the version from the user into a structure.
+ * 
+ * @param {string | undefined} version
+ * @returns {VersionRange | null}
+ */
+function parseVersionRange(version) {
+  version = String(version) || "1.x";
+  version = version.trim();
+
+  if (version == "canary") {
+    return { range: "latest", isCanary: true };
+  }
+
+  if (GIT_HASH_RE.test(version)) {
+    return { range: version, isCanary: true };
+  }
+
+  const range = semver.validRange(version);
+  if (range !== null) {
+    return { range, isCanary: false };
+  }
+
+  return null;
+}
+
+/**
+ * @param {VersionRange} range
+ * @returns {Promise<Version | null>}
+ */
+async function resolveVersion({ range, isCanary }) {
+  if (isCanary) {
+    if (range === "latest") {
+      const res = await fetch("https://dl.deno.land/canary-latest.txt");
+      if (res.status !== 200) {
+        throw new Error(
+          "Failed to fetch canary version info from dl.deno.land. Please try again later.",
+        );
+      }
+      const version = (await res.text()).trim();
+      return { version, isCanary: true };
+    }
+    return { version: range, isCanary: true };
+  }
+
+  const res = await fetch(
+    "https://raw.githubusercontent.com/denoland/deno_website2/main/versions.json",
+  );
+  if (res.status !== 200) {
+    throw new Error(
+      "Failed to fetch stable version info from raw.githubusercontent.com. Please try again later.",
+    );
+  }
+  const versionJson = await res.json();
+  if (!("cli" in versionJson)) {
+    throw new Error("Fetched stable version info is invalid.");
+  }
+  /** @type {string[]} */
+  const versions = versionJson.cli;
+  if (!Array.isArray(versions)) {
+    throw new Error("Fetched stable version info is invalid.");
+  }
+
+  let version = semver.maxSatisfying(versions, range);
+  if (version === null) {
+    return null;
+  }
+  version = semver.clean(version);
+  if (version === null) {
+    return null;
+  }
+
+  return { version, isCanary: false };
+}
+
+module.exports = {
+  parseVersionRange,
+  resolveVersion,
+};