feat(handlers): add npm

Author: boywithkeyboard

handlers/npm.ts

@@ -0,0 +1,145 @@
+import semver from 'semver'
+import { respondWithError } from '../respondWithError.ts'
+import { rewriteContent } from '../rewriteContent.ts'
+import { Handler, HandlerContext } from '../types.ts'
+
+function parseUrl(url: URL) {
+  const pieces = url.pathname.split('/').slice(2)
+  const isScoped = pieces[0].startsWith('@')
+
+  let name: string
+  let version: string | null = null
+  let submodulePath: string
+
+  if (isScoped) {
+    const includesVersion = pieces[1].includes('@')
+
+    if (includesVersion) {
+      version = pieces[1].split('@')[1]
+      pieces[1] = pieces[1].split('@')[0]
+      name = pieces.slice(0, 2).join('/')
+    } else {
+      name = pieces.slice(0, 2).join('/')
+    }
+
+    submodulePath = '/' + pieces.slice(2).join('/')
+  } else {
+    const includesVersion = pieces[0].includes('@')
+
+    if (includesVersion) {
+      name = pieces[0].split('@')[0]
+      version = pieces[0].split('@')[1]
+    } else {
+      name = pieces[0]
+    }
+
+    submodulePath = '/' + pieces.slice(1).join('/')
+  }
+
+  return {
+    name,
+    version,
+    submodulePath,
+  }
+}
+
+async function fetchVersions(
+  ctx: HandlerContext,
+  data: ReturnType<typeof parseUrl>,
+): Promise<string[]> {
+  const cachedVersions = await ctx.versionCache.get(`npm:${data.name}`)
+
+  if (cachedVersions) {
+    return cachedVersions
+  }
+
+  const res = await fetch(`https://registry.npmjs.org/${data.name}`)
+
+  if (!res.ok) {
+    return []
+  }
+
+  let { versions } = await res.json() as { versions: string[] }
+
+  versions = Object.keys(versions)
+
+  await ctx.versionCache.set(`npm:${data.name}`, versions)
+
+  return versions.filter((version) => semver.valid(version))
+}
+
+export const handle: Handler = async (ctx) => {
+  const data = parseUrl(ctx.url)
+
+  // if there's no version tag
+  if (data.version === null) {
+    const versions = await fetchVersions(ctx, data)
+
+    if (versions.length === 0) {
+      return respondWithError('BAD_MODULE')
+    }
+
+    data.version = semver.rsort(versions)[0]
+    // if there's an invalid version tag or range
+  } else if (semver.valid(data.version) === null) {
+    if (semver.validRange(data.version) === null) {
+      return respondWithError('BAD_VERSION')
+    }
+
+    const versions = await fetchVersions(ctx, data)
+
+    if (versions.length === 0) {
+      return respondWithError('BAD_MODULE')
+    }
+
+    const suggestedVersion = semver.maxSatisfying(versions, data.version)
+
+    if (suggestedVersion === null) {
+      return respondWithError('BAD_VERSION')
+    }
+
+    data.version = suggestedVersion
+  }
+
+  if (ctx.url.searchParams.has('tgz') || ctx.url.searchParams.has('tar.gz')) {
+    return Response.redirect(
+      `https://registry.npmjs.org/${data.name}/-/${data.name}-${data.version}.tgz`,
+      307,
+    )
+  }
+
+  const res = await fetch(
+    `https://cdn.jsdelivr.net/npm/${data.name}@${data.version}${
+      data.submodulePath === '/' ? '' : data.submodulePath
+    }/+esm`,
+  )
+
+  if (!res.ok) {
+    return respondWithError('UNINDEXED_MODULE')
+  }
+
+  let content = await res.text()
+
+  content = rewriteContent(content, ({ url }) => {
+    // e.g. /npm/[email protected]/+esm
+    if (/^\/npm(\/[^\/]+)+\/\+esm$/.test(url)) {
+      url = url.replace(
+        '/npm',
+        ctx.url.protocol + '//' + ctx.url.hostname + '/npm',
+      )
+      url = url.slice(0, -5) // remove /+esm
+    }
+
+    return url
+  })
+
+  return new Response(content, {
+    headers: {
+      'cache-control': `public, max-age=${ctx.cacheDurationInHours * 3600}`,
+      'content-type': 'text/javascript; charset=utf-8',
+      'x-typescript-types': `https://esm.sh/${data.name}@${data.version}${
+        data.submodulePath === '/' ? '' : data.submodulePath
+      }?target=es2022`,
+    },
+  })
+}