data: Track.withAlbum: refactor for clarity

Utilizes availability checks instead of manual null comparisons and
empty() calls, extracts track lists using withPropertyFromList,
operates on index instead of unique album object where possible
(including found / not found check).

1 files changed, 71 insertions, 27 deletions

diff --git a/src/data/composite/things/track/withAlbum.js b/src/data/composite/things/track/withAlbum.js
index 0e85cee..9c974cd 100644
--- a/src/data/composite/things/track/withAlbum.js
+++ b/src/data/composite/things/track/withAlbum.js
@@ -4,9 +4,12 @@
 // exit instead.
 
 import {input, templateCompositeFrom} from '#composite';
-import {empty} from '#sugar';
 import {is} from '#validators';
 
+import {exitWithoutDependency, withResultOfAvailabilityCheck}
+  from '#composite/control-flow';
+import {withPropertyFromList} from '#composite/data';
+
 export default templateCompositeFrom({
   annotation: `withAlbum`,
 
@@ -20,43 +23,84 @@ export default templateCompositeFrom({
   outputs: ['#album'],
 
   steps: () => [
+    // null albumData is always an early exit.
+
+    exitWithoutDependency({
+      dependency: 'albumData',
+      mode: input.value('null'),
+    }),
+
+    // empty albumData conditionally exits early or outputs null.
+
+    withResultOfAvailabilityCheck({
+      from: 'albumData',
+      mode: input.value('empty'),
+    }).outputs({
+      '#availability': '#albumDataAvailability',
+    }),
+
     {
-      dependencies: [input('notFoundMode'), 'albumData'],
-      compute: (continuation, {
+      dependencies: [input('notFoundMode'), '#albumDataAvailability'],
+      compute(continuation, {
         [input('notFoundMode')]: notFoundMode,
-        ['albumData']: albumData,
-      }) =>
-        (albumData === null
-          ? continuation.exit(null)
-       : empty(albumData)
-          ? (notFoundMode === 'exit'
-              ? continuation.exit(null)
-              : continuation.raiseOutput({'#album': null}))
-          : continuation()),
+        ['#albumDataAvailability']: albumDataIsAvailable,
+      }) {
+        if (albumDataIsAvailable) return continuation();
+        switch (notFoundMode) {
+          case 'exit': return continuation.exit(null);
+          case 'null': return continuation.raiseOutput({'#album': null});
+        }
+      },
     },
 
+    withPropertyFromList({
+      list: 'albumData',
+      property: input.value('tracks'),
+    }),
+
     {
-      dependencies: [input.myself(), 'albumData'],
+      dependencies: [input.myself(), '#albumData.tracks'],
       compute: (continuation, {
         [input.myself()]: track,
-        ['albumData']: albumData,
-      }) =>
-        continuation({
-          ['#album']:
-            albumData.find(album => album.tracks.includes(track))
-              ?? null,
-        }),
+        ['#albumData.tracks']: trackLists,
+      }) => continuation({
+        ['#albumIndex']:
+          trackLists.findIndex(tracks => tracks.includes(track)),
+      }),
     },
 
+    // album not found conditionally exits or outputs null.
+
+    withResultOfAvailabilityCheck({
+      from: '#albumIndex',
+      mode: input.value('index'),
+    }).outputs({
+      '#availability': '#albumAvailability',
+    }),
+
     {
-      dependencies: [input('notFoundMode'), '#album'],
-      compute: (continuation, {
+      dependencies: [input('notFoundMode'), '#albumAvailability'],
+      compute(continuation, {
         [input('notFoundMode')]: notFoundMode,
-        ['#album']: album,
-      }) =>
-        ((album === null && notFoundMode === 'exit')
-          ? continuation.exit(null)
-          : continuation.raiseOutput({'#album': album})),
+        ['#albumAvailability']: albumIsAvailable,
+      }) {
+        if (albumIsAvailable) return continuation();
+        switch (notFoundMode) {
+          case 'exit': return continuation.exit(null);
+          case 'null': return continuation.raiseOutput({'#album': null});
+        }
+      },
+    },
+
+    {
+      dependencies: ['albumData', '#albumIndex'],
+      compute: (continuation, {
+        ['albumData']: albumData,
+        ['#albumIndex']: albumIndex,
+      }) => continuation.raiseOutput({
+        ['#album']:
+          albumData[albumIndex],
+      }),
     },
   ],
 });