feat: add Key.asKey method (#41)

`instanceOf` is unreliable across EJS/CSM but also across different bundles loaded in the browser.

Add a `Key.asKey` method we can use as a more reliable `instanceOf` check.

packages/interface-datastore/src/key.js

@@ -109,6 +109,23 @@ export class Key {
     return new Key(nanoid().replace(/-/g, ''))
   }
 
+  /**
+   * @param {*} other
+   */
+  static asKey (other) {
+    if (other instanceof Uint8Array || typeof other === 'string') {
+      // we can create a key from this
+      return new Key(other)
+    }
+
+    if (other.uint8Array) {
+      // this is an older version or may have crossed the esm/cjs boundary
+      return new Key(other.uint8Array())
+    }
+
+    return null
+  }
+
   /**
    * Cleanup the current key
    *

packages/interface-datastore/test/key.spec.js

@@ -2,6 +2,7 @@
 
 import { expect } from 'aegir/utils/chai.js'
 import { Key } from '../src/key.js'
+import { fromString as uint8ArrayFromString } from 'uint8arrays'
 
 const pathSep = '/'
 
@@ -205,4 +206,37 @@ describe('Key', () => {
     // should be a view on the original buffer
     expect(buf.buffer).to.equal(arrWithSlashes.buffer)
   })
+
+  it('should turn a string into a key', () => {
+    const str = '/foo/bar'
+    const key = Key.asKey(str)
+
+    expect(`${key}`).to.equal(str)
+  })
+
+  it('should turn a key into a key', () => {
+    const str = '/foo/bar'
+    const key = Key.asKey(new Key(str))
+
+    expect(`${key}`).to.equal(str)
+  })
+
+  it('should turn a uint8array into a key', () => {
+    const str = '/foo/bar'
+    const key = Key.asKey(uint8ArrayFromString(str))
+
+    expect(`${key}`).to.equal(str)
+  })
+
+  it('should not turn a falsy value into a key', () => {
+    const key = Key.asKey(false)
+
+    expect(key).to.be.null()
+  })
+
+  it('should not turn an invalid value into a key', () => {
+    expect(Key.asKey({})).to.be.null()
+    expect(Key.asKey(5)).to.be.null()
+    expect(Key.asKey(() => {})).to.be.null()
+  })
 })