add tests and docs

src/deny.ts

@@ -0,0 +1,42 @@
+import {Change} from './schemas'
+import * as core from '@actions/core'
+
+export async function getDeniedChanges(
+  changes: Change[],
+  deniedPackages: string[],
+  deniedGroups: string[]
+): Promise<Change[]> {
+  const changesDenied: Change[] = []
+
+  let failed = false
+  for (const change of changes) {
+    change.name = change.name.toLowerCase()
+    change.package_url = change.package_url.toLowerCase()
+
+    if (deniedPackages) {
+      for (const denied of deniedPackages) {
+        if (change.name === denied.toLowerCase()) {
+          changesDenied.push(change)
+          failed = true
+        }
+      }
+    }
+
+    if (deniedGroups) {
+      for (const denied of deniedGroups) {
+        if (change.name.startsWith(denied.toLowerCase())) {
+          changesDenied.push(change)
+          failed = true
+        }
+      }
+    }
+  }
+
+  if (failed) {
+    core.setFailed('Dependency review detected denied packages.')
+  } else {
+    core.info('Dependency review did not detect any denied packages')
+  }
+
+  return changesDenied
+}