4 files changed, 142 insertions, 0 deletions
diff --git a/src/data/composite/data/index.js b/src/data/composite/data/index.js
index 256c0490..0a47c43c 100644
--- a/src/data/composite/data/index.js
+++ b/src/data/composite/data/index.js
@@ -13,5 +13,6 @@ export {default as withPropertiesFromObject} from './withPropertiesFromObject.js
 export {default as withPropertyFromList} from './withPropertyFromList.js';
 export {default as withPropertyFromObject} from './withPropertyFromObject.js';
 export {default as withSortedList} from './withSortedList.js';
+export {default as withSum} from './withSum.js';
 export {default as withUnflattenedList} from './withUnflattenedList.js';
 export {default as withUniqueItemsOnly} from './withUniqueItemsOnly.js';
diff --git a/src/data/composite/data/withSum.js b/src/data/composite/data/withSum.js
new file mode 100644
index 00000000..484e9906
--- /dev/null
+++ b/src/data/composite/data/withSum.js
@@ -0,0 +1,33 @@
+// Gets the numeric total of adding all the values in a list together.
+// Values that are false, null, or undefined are skipped over.
+
+import {input, templateCompositeFrom} from '#composite';
+import {isNumber, sparseArrayOf} from '#validators';
+
+export default templateCompositeFrom({
+  annotation: `withSum`,
+
+  inputs: {
+    values: input({
+      validate: sparseArrayOf(isNumber),
+    }),
+  },
+
+  outputs: ['#sum'],
+
+  steps: () => [
+    {
+      dependencies: [input('values')],
+      compute: (continuation, {
+        [input('values')]: values,
+      }) => continuation({
+        ['#sum']:
+          values
+            .filter(item => typeof item === 'number')
+            .reduce(
+              (accumulator, value) => accumulator + value,
+              0),
+      }),
+    },
+  ],
+});
diff --git a/src/data/composite/wiki-data/index.js b/src/data/composite/wiki-data/index.js
index a0a6be7f..9a9a5fa2 100644
--- a/src/data/composite/wiki-data/index.js
+++ b/src/data/composite/wiki-data/index.js
@@ -6,6 +6,7 @@
 
 export {default as exitWithoutContribs} from './exitWithoutContribs.js';
 export {default as inputWikiData} from './inputWikiData.js';
+export {default as withContributionListSums} from './withContributionListSums.js';
 export {default as withDirectory} from './withDirectory.js';
 export {default as withDirectoryFromName} from './withDirectoryFromName.js';
 export {default as withParsedCommentaryEntries} from './withParsedCommentaryEntries.js';
diff --git a/src/data/composite/wiki-data/withContributionListSums.js b/src/data/composite/wiki-data/withContributionListSums.js
new file mode 100644
index 00000000..cc37177e
--- /dev/null
+++ b/src/data/composite/wiki-data/withContributionListSums.js
@@ -0,0 +1,107 @@
+// Gets the total duration and contribution count from a list of contributions,
+// respecting their `countInContributionTotals` and `countInDurationTotals`
+// flags.
+
+import {input, templateCompositeFrom} from '#composite';
+
+import {
+  withFilteredList,
+  withPropertiesFromList,
+  withPropertyFromList,
+  withSum,
+  withUniqueItemsOnly,
+} from '#composite/data';
+
+export default templateCompositeFrom({
+  annotation: `withContributionListSums`,
+
+  inputs: {
+    list: input({type: 'array'}),
+  },
+
+  outputs: [
+    '#contributionListCount',
+    '#contributionListDuration',
+  ],
+
+  steps: () => [
+    withPropertiesFromList({
+      list: input('list'),
+      properties: input.value([
+        'countInContributionTotals',
+        'countInDurationTotals',
+      ]),
+    }),
+
+    withFilteredList({
+      list: input('list'),
+      filter: '#list.countInContributionTotals',
+    }).outputs({
+      '#filteredList': '#contributionsForCounting',
+    }),
+
+    withFilteredList({
+      list: input('list'),
+      filter: '#list.countInDurationTotals',
+    }).outputs({
+      '#filteredList': '#contributionsForDuration',
+    }),
+
+    {
+      dependencies: ['#contributionsForCounting'],
+      compute: (continuation, {
+        ['#contributionsForCounting']: contributionsForCounting,
+      }) => continuation({
+        ['#count']:
+          contributionsForCounting.length,
+      }),
+    },
+
+    withPropertyFromList({
+      list: '#contributionsForDuration',
+      property: input.value('thing'),
+    }),
+
+    // Don't double-up the durations for a track where the artist has multiple
+    // contributions.
+    withUniqueItemsOnly({
+      list: '#contributionsForDuration.thing',
+    }),
+
+    withPropertyFromList({
+      list: '#contributionsForDuration.thing',
+      property: input.value('duration'),
+    }).outputs({
+      '#contributionsForDuration.thing.duration': '#durationValues',
+    }),
+
+    {
+      dependencies: [
+        input('list'),
+        '#contributionsForDuration.thing',
+        '#durationValues',
+      ],
+      compute: (continuation, opts) => {
+        console.log(opts);
+        return continuation();
+      },
+    },
+
+    withSum({
+      values: '#durationValues',
+    }).outputs({
+      '#sum': '#duration',
+    }),
+
+    {
+      dependencies: ['#count', '#duration'],
+      compute: (continuation, {
+        ['#count']: count,
+        ['#duration']: duration,
+      }) => continuation({
+        ['#contributionListCount']: count,
+        ['#contributionListDuration']: duration,
+      }),
+    },
+  ],
+});