centralize collection of action inputs (#72)

Signed-off-by: Brian DeHamer <bdehamer@github.com>

src/predicate.ts

@@ -1,26 +1,32 @@
-import * as core from '@actions/core'
 import fs from 'fs'
 
 import type { Predicate } from '@actions/attest'
 
+export type PredicateInputs = {
+  predicateType: string
+  predicate: string
+  predicatePath: string
+}
 // Returns the predicate specified by the action's inputs. The predicate value
 // may be specified as a path to a file or as a string.
-export const predicateFromInputs = (): Predicate => {
-  const predicateType = core.getInput('predicate-type', { required: true })
-  const predicateStr = core.getInput('predicate', { required: false })
-  const predicatePath = core.getInput('predicate-path', { required: false })
+export const predicateFromInputs = (inputs: PredicateInputs): Predicate => {
+  const { predicateType, predicate, predicatePath } = inputs
 
-  if (!predicatePath && !predicateStr) {
+  if (!predicateType) {
+    throw new Error('predicate-type must be provided')
+  }
+
+  if (!predicatePath && !predicate) {
     throw new Error('One of predicate-path or predicate must be provided')
   }
 
-  if (predicatePath && predicateStr) {
+  if (predicatePath && predicate) {
     throw new Error('Only one of predicate-path or predicate may be provided')
   }
 
   const params = predicatePath
     ? fs.readFileSync(predicatePath, 'utf-8')
-    : predicateStr
+    : predicate
 
   return { type: predicateType, params: JSON.parse(params) }
 }