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hsmusic-wiki - HSMusic - static wiki software cataloguing collaborative creation
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-rw-r--r--src/data/things/thing.js994
1 files changed, 661 insertions, 333 deletions
diff --git a/src/data/things/thing.js b/src/data/things/thing.js
index 5705ee7e..f1302e17 100644
--- a/src/data/things/thing.js
+++ b/src/data/things/thing.js
@@ -3,419 +3,747 @@
 
 import {inspect} from 'node:util';
 
-import {color} from '#cli';
+import {colors} from '#cli';
 import find from '#find';
-import {empty} from '#sugar';
-import {getKebabCase} from '#wiki-data';
+import {stitchArrays, unique} from '#sugar';
+import {filterMultipleArrays, getKebabCase} from '#wiki-data';
+import {is} from '#validators';
+
+import {
+  compositeFrom,
+  exitWithoutDependency,
+  exposeConstant,
+  exposeDependency,
+  exposeDependencyOrContinue,
+  input,
+  raiseOutputWithoutDependency,
+  templateCompositeFrom,
+  withResultOfAvailabilityCheck,
+  withPropertiesFromList,
+} from '#composite';
 
 import {
   isAdditionalFileList,
   isBoolean,
-  isCommentary,
   isColor,
+  isCommentary,
   isContributionList,
   isDate,
+  isDimensions,
   isDirectory,
+  isDuration,
   isFileExtension,
   isName,
   isString,
+  isType,
   isURL,
   validateArrayItems,
   validateInstanceOf,
   validateReference,
   validateReferenceList,
+  validateWikiData,
 } from '#validators';
 
 import CacheableObject from './cacheable-object.js';
 
 export default class Thing extends CacheableObject {
-  static referenceType = Symbol('Thing.referenceType');
+  static referenceType = Symbol.for('Thing.referenceType');
 
   static getPropertyDescriptors = Symbol('Thing.getPropertyDescriptors');
   static getSerializeDescriptors = Symbol('Thing.getSerializeDescriptors');
 
-  // Regularly reused property descriptors, for ease of access and generally
-  // duplicating less code across wiki data types. These are specialized utility
-  // functions, so check each for how its own arguments behave!
-  static common = {
-    name: (defaultName) => ({
-      flags: {update: true, expose: true},
-      update: {validate: isName, default: defaultName},
-    }),
+  // Default custom inspect function, which may be overridden by Thing
+  // subclasses. This will be used when displaying aggregate errors and other
+  // command-line logging - it's the place to provide information useful in
+  // identifying the Thing being presented.
+  [inspect.custom]() {
+    const cname = this.constructor.name;
 
-    color: () => ({
-      flags: {update: true, expose: true},
-      update: {validate: isColor},
-    }),
+    return (
+      (this.name ? `${cname} ${colors.green(`"${this.name}"`)}` : `${cname}`) +
+      (this.directory ? ` (${colors.blue(Thing.getReference(this))})` : '')
+    );
+  }
 
-    directory: () => ({
-      flags: {update: true, expose: true},
-      update: {validate: isDirectory},
-      expose: {
-        dependencies: ['name'],
-        transform(directory, {name}) {
-          if (directory === null && name === null) return null;
-          else if (directory === null) return getKebabCase(name);
-          else return directory;
-        },
+  static getReference(thing) {
+    if (!thing.constructor[Thing.referenceType]) {
+      throw TypeError(`Passed Thing is ${thing.constructor.name}, which provides no [Thing.referenceType]`);
+    }
+
+    if (!thing.directory) {
+      throw TypeError(`Passed ${thing.constructor.name} is missing its directory`);
+    }
+
+    return `${thing.constructor[Thing.referenceType]}:${thing.directory}`;
+  }
+}
+
+// Property descriptor templates
+//
+// Regularly reused property descriptors, for ease of access and generally
+// duplicating less code across wiki data types. These are specialized utility
+// functions, so check each for how its own arguments behave!
+
+export function name(defaultName) {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isName, default: defaultName},
+  };
+}
+
+export function color() {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isColor},
+  };
+}
+
+export function directory() {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isDirectory},
+    expose: {
+      dependencies: ['name'],
+      transform(directory, {name}) {
+        if (directory === null && name === null) return null;
+        else if (directory === null) return getKebabCase(name);
+        else return directory;
       },
-    }),
+    },
+  };
+}
 
-    urls: () => ({
-      flags: {update: true, expose: true},
-      update: {validate: validateArrayItems(isURL)},
-      expose: {transform: (value) => value ?? []},
-    }),
+export function urls() {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: validateArrayItems(isURL)},
+    expose: {transform: (value) => value ?? []},
+  };
+}
 
-    // A file extension! Or the default, if provided when calling this.
-    fileExtension: (defaultFileExtension = null) => ({
-      flags: {update: true, expose: true},
-      update: {validate: isFileExtension},
-      expose: {transform: (value) => value ?? defaultFileExtension},
-    }),
+// A file extension! Or the default, if provided when calling this.
+export function fileExtension(defaultFileExtension = null) {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isFileExtension},
+    expose: {transform: (value) => value ?? defaultFileExtension},
+  };
+}
+
+// Plain ol' image dimensions. This is a two-item array of positive integers,
+// corresponding to width and height respectively.
+export function dimensions() {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isDimensions},
+  };
+}
+
+// Duration! This is a number of seconds, possibly floating point, always
+// at minimum zero.
+export function duration() {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isDuration},
+  };
+}
+
+// Straightforward flag descriptor for a variety of property purposes.
+// Provide a default value, true or false!
+export function flag(defaultValue = false) {
+  // TODO:                        ^ Are you actually kidding me
+  if (typeof defaultValue !== 'boolean') {
+    throw new TypeError(`Always set explicit defaults for flags!`);
+  }
+
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isBoolean, default: defaultValue},
+  };
+}
+
+// General date type, used as the descriptor for a bunch of properties.
+// This isn't dynamic though - it won't inherit from a date stored on
+// another object, for example.
+export function simpleDate() {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isDate},
+  };
+}
+
+// General string type. This should probably generally be avoided in favor
+// of more specific validation, but using it makes it easy to find where we
+// might want to improve later, and it's a useful shorthand meanwhile.
+export function simpleString() {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isString},
+  };
+}
+
+// External function. These should only be used as dependencies for other
+// properties, so they're left unexposed.
+export function externalFunction() {
+  return {
+    flags: {update: true},
+    update: {validate: (t) => typeof t === 'function'},
+  };
+}
+
+// Strong 'n sturdy contribution list, rolling a list of references (provided
+// as this property's update value) and the resolved results (as get exposed)
+// into one property. Update value will look something like this:
+//
+//   [
+//     {who: 'Artist Name', what: 'Viola'},
+//     {who: 'artist:john-cena', what: null},
+//     ...
+//   ]
+//
+// ...typically as processed from YAML, spreadsheet, or elsewhere.
+// Exposes as the same, but with the "who" replaced with matches found in
+// artistData - which means this always depends on an `artistData` property
+// also existing on this object!
+//
+export function contributionList() {
+  return compositeFrom({
+    annotation: `contributionList`,
+
+    compose: false,
+
+    update: {validate: isContributionList},
+
+    steps: [
+      withResolvedContribs({from: input.updateValue()}),
+      exposeDependencyOrContinue({dependency: '#resolvedContribs'}),
+      exposeConstant({value: input.value([])}),
+    ],
+  });
+}
 
-    // Straightforward flag descriptor for a variety of property purposes.
-    // Provide a default value, true or false!
-    flag: (defaultValue = false) => {
-      if (typeof defaultValue !== 'boolean') {
-        throw new TypeError(`Always set explicit defaults for flags!`);
-      }
-
-      return {
-        flags: {update: true, expose: true},
-        update: {validate: isBoolean, default: defaultValue},
-      };
+// Artist commentary! Generally present on tracks and albums.
+export function commentary() {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isCommentary},
+  };
+}
+
+// This is a somewhat more involved data structure - it's for additional
+// or "bonus" files associated with albums or tracks (or anything else).
+// It's got this form:
+//
+//     [
+//         {title: 'Booklet', files: ['Booklet.pdf']},
+//         {
+//             title: 'Wallpaper',
+//             description: 'Cool Wallpaper!',
+//             files: ['1440x900.png', '1920x1080.png']
+//         },
+//         {title: 'Alternate Covers', description: null, files: [...]},
+//         ...
+//     ]
+//
+export function additionalFiles() {
+  return {
+    flags: {update: true, expose: true},
+    update: {validate: isAdditionalFileList},
+    expose: {
+      transform: (additionalFiles) =>
+        additionalFiles ?? [],
     },
+  };
+}
 
-    // General date type, used as the descriptor for a bunch of properties.
-    // This isn't dynamic though - it won't inherit from a date stored on
-    // another object, for example.
-    simpleDate: () => ({
-      flags: {update: true, expose: true},
-      update: {validate: isDate},
-    }),
+const thingClassInput = {
+  validate(thingClass) {
+    isType(thingClass, 'function');
+
+    if (!Object.hasOwn(thingClass, Thing.referenceType)) {
+      throw new TypeError(`Expected a Thing constructor, missing Thing.referenceType`);
+    }
 
-    // General string type. This should probably generally be avoided in favor
-    // of more specific validation, but using it makes it easy to find where we
-    // might want to improve later, and it's a useful shorthand meanwhile.
-    simpleString: () => ({
-      flags: {update: true, expose: true},
-      update: {validate: isString},
+    return true;
+  },
+};
+
+// A reference list! Keep in mind this is for general references to wiki
+// objects of (usually) other Thing subclasses, not specifically leitmotif
+// references in tracks (although that property uses referenceList too!).
+//
+// The underlying function validateReferenceList expects a string like
+// 'artist' or 'track', but this utility keeps from having to hard-code the
+// string in multiple places by referencing the value saved on the class
+// instead.
+export const referenceList = templateCompositeFrom({
+  annotation: `referenceList`,
+
+  compose: false,
+
+  inputs: {
+    class: input.staticValue(thingClassInput),
+
+    data: inputWikiData({allowMixedTypes: false}),
+    find: input({type: 'function'}),
+  },
+
+  update: ({
+    [input.staticValue('class')]: thingClass,
+  }) => {
+    const {[Thing.referenceType]: referenceType} = thingClass;
+    return {validate: validateReferenceList(referenceType)};
+  },
+
+  steps: () => [
+    withResolvedReferenceList({
+      list: input.updateValue(),
+      data: input('data'),
+      find: input('find'),
     }),
 
-    // External function. These should only be used as dependencies for other
-    // properties, so they're left unexposed.
-    externalFunction: ({expose = false} = {}) => ({
-      flags: {update: true, expose},
-      update: {validate: (t) => typeof t === 'function'},
+    exposeDependency({dependency: '#resolvedReferenceList'}),
+  ],
+});
+
+// Corresponding function for a single reference.
+export const singleReference = templateCompositeFrom({
+  annotation: `singleReference`,
+
+  compose: false,
+
+  inputs: {
+    class: input(thingClassInput),
+    find: input({type: 'function'}),
+    data: inputWikiData({allowMixedTypes: false}),
+  },
+
+  update: ({
+    [input.staticValue('class')]: thingClass,
+  }) => {
+    const {[Thing.referenceType]: referenceType} = thingClass;
+    return {validate: validateReference(referenceType)};
+  },
+
+  steps: () => [
+    withResolvedReference({
+      ref: input.updateValue(),
+      data: input('data'),
+      find: input('find'),
     }),
 
-    // Super simple "contributions by reference" list, used for a variety of
-    // properties (Artists, Cover Artists, etc). This is the property which is
-    // externally provided, in the form:
-    //
-    //     [
-    //         {who: 'Artist Name', what: 'Viola'},
-    //         {who: 'artist:john-cena', what: null},
-    //         ...
-    //     ]
-    //
-    // ...processed from YAML, spreadsheet, or any other kind of input.
-    contribsByRef: () => ({
-      flags: {update: true, expose: true},
-      update: {validate: isContributionList},
+    exposeDependency({dependency: '#resolvedReference'}),
+  ],
+});
+
+// Nice 'n simple shorthand for an exposed-only flag which is true when any
+// contributions are present in the specified property.
+export const contribsPresent = templateCompositeFrom({
+  annotation: `contribsPresent`,
+
+  compose: false,
+
+  inputs: {
+    contribs: input.staticDependency({
+      validate: isContributionList,
+      acceptsNull: true,
     }),
+  },
 
-    // Artist commentary! Generally present on tracks and albums.
-    commentary: () => ({
-      flags: {update: true, expose: true},
-      update: {validate: isCommentary},
+  steps: () => [
+    withResultOfAvailabilityCheck({
+      from: input('contribs'),
+      mode: input.value('empty'),
     }),
 
-    // This is a somewhat more involved data structure - it's for additional
-    // or "bonus" files associated with albums or tracks (or anything else).
-    // It's got this form:
-    //
-    //     [
-    //         {title: 'Booklet', files: ['Booklet.pdf']},
-    //         {
-    //             title: 'Wallpaper',
-    //             description: 'Cool Wallpaper!',
-    //             files: ['1440x900.png', '1920x1080.png']
-    //         },
-    //         {title: 'Alternate Covers', description: null, files: [...]},
-    //         ...
-    //     ]
-    //
-    additionalFiles: () => ({
-      flags: {update: true, expose: true},
-      update: {validate: isAdditionalFileList},
-      expose: {
-        transform: (additionalFiles) =>
-          additionalFiles ?? [],
-      },
+    exposeDependency({dependency: '#availability'}),
+  ],
+});
+
+// Neat little shortcut for "reversing" the reference lists stored on other
+// things - for example, tracks specify a "referenced tracks" property, and
+// you would use this to compute a corresponding "referenced *by* tracks"
+// property. Naturally, the passed ref list property is of the things in the
+// wiki data provided, not the requesting Thing itself.
+export const reverseReferenceList = templateCompositeFrom({
+  annotation: `reverseReferenceList`,
+
+  compose: false,
+
+  inputs: {
+    data: inputWikiData({allowMixedTypes: false}),
+    list: input({type: 'string'}),
+  },
+
+  steps: () => [
+    withReverseReferenceList({
+      data: input('data'),
+      list: input('list'),
     }),
 
-    // A reference list! Keep in mind this is for general references to wiki
-    // objects of (usually) other Thing subclasses, not specifically leitmotif
-    // references in tracks (although that property uses referenceList too!).
-    //
-    // The underlying function validateReferenceList expects a string like
-    // 'artist' or 'track', but this utility keeps from having to hard-code the
-    // string in multiple places by referencing the value saved on the class
-    // instead.
-    referenceList: (thingClass) => {
-      const {[Thing.referenceType]: referenceType} = thingClass;
-      if (!referenceType) {
-        throw new Error(`The passed constructor ${thingClass.name} doesn't define Thing.referenceType!`);
-      }
-
-      return {
-        flags: {update: true, expose: true},
-        update: {validate: validateReferenceList(referenceType)},
-      };
+    exposeDependency({dependency: '#reverseReferenceList'}),
+  ],
+});
+
+// General purpose wiki data constructor, for properties like artistData,
+// trackData, etc.
+export function wikiData(thingClass) {
+  return {
+    flags: {update: true},
+    update: {
+      validate: validateArrayItems(validateInstanceOf(thingClass)),
     },
+  };
+}
+
+// This one's kinda tricky: it parses artist "references" from the
+// commentary content, and finds the matching artist for each reference.
+// This is mostly useful for credits and listings on artist pages.
+export const commentatorArtists = templateCompositeFrom({
+  annotation: `commentatorArtists`,
+
+  compose: false,
+
+  steps: () => [
+    exitWithoutDependency({
+      dependency: 'commentary',
+      mode: input.value('falsy'),
+      value: input.value([]),
+    }),
 
-    // Corresponding function for a single reference.
-    singleReference: (thingClass) => {
-      const {[Thing.referenceType]: referenceType} = thingClass;
-      if (!referenceType) {
-        throw new Error(`The passed constructor ${thingClass.name} doesn't define Thing.referenceType!`);
-      }
-
-      return {
-        flags: {update: true, expose: true},
-        update: {validate: validateReference(referenceType)},
-      };
+    {
+      dependencies: ['commentary'],
+      compute: (continuation, {commentary}) =>
+        continuation({
+          '#artistRefs':
+            Array.from(
+              commentary
+                .replace(/<\/?b>/g, '')
+                .matchAll(/<i>(?<who>.*?):<\/i>/g))
+              .map(({groups: {who}}) => who),
+        }),
     },
 
-    // Corresponding dynamic property to referenceList, which takes the values
-    // in the provided property and searches the specified wiki data for
-    // matching actual Thing-subclass objects.
-    dynamicThingsFromReferenceList: (
-      referenceListProperty,
-      thingDataProperty,
-      findFn
-    ) => ({
+    withResolvedReferenceList({
+      list: '#artistRefs',
+      data: 'artistData',
+      find: input.value(find.artist),
+    }).outputs({
+      '#resolvedReferenceList': '#artists',
+    }),
+
+    {
       flags: {expose: true},
 
       expose: {
-        dependencies: [referenceListProperty, thingDataProperty],
-        compute: ({
-          [referenceListProperty]: refs,
-          [thingDataProperty]: thingData,
-        }) =>
-          refs && thingData
-            ? refs
-                .map((ref) => findFn(ref, thingData, {mode: 'quiet'}))
-                .filter(Boolean)
-            : [],
+        dependencies: ['#artists'],
+        compute: ({'#artists': artists}) =>
+          unique(artists),
       },
+    },
+  ],
+});
+
+// Compositional utilities
+
+// TODO: This doesn't access a class's own ThingSubclass[Thing.referenceType]
+// value because classes aren't initialized by when templateCompositeFrom gets
+// called (see: circular imports). So the reference types have to be hard-coded,
+// which somewhat defeats the point of storing them on the class in the first
+// place...
+export function inputWikiData({
+  referenceType = '',
+  allowMixedTypes = false,
+} = {}) {
+  return input({
+    validate: validateWikiData({referenceType, allowMixedTypes}),
+    acceptsNull: true,
+  });
+}
+
+// Resolves the contribsByRef contained in the provided dependency,
+// providing (named by the second argument) the result. "Resolving"
+// means mapping the "who" reference of each contribution to an artist
+// object, and filtering out those whose "who" doesn't match any artist.
+export const withResolvedContribs = templateCompositeFrom({
+  annotation: `withResolvedContribs`,
+
+  inputs: {
+    from: input({
+      validate: isContributionList,
+      acceptsNull: true,
     }),
 
-    // Corresponding function for a single reference.
-    dynamicThingFromSingleReference: (
-      singleReferenceProperty,
-      thingDataProperty,
-      findFn
-    ) => ({
-      flags: {expose: true},
+    notFoundMode: input({
+      validate: is('exit', 'filter', 'null'),
+      defaultValue: 'null',
+    }),
+  },
 
-      expose: {
-        dependencies: [singleReferenceProperty, thingDataProperty],
-        compute: ({
-          [singleReferenceProperty]: ref,
-          [thingDataProperty]: thingData,
-        }) => (ref && thingData ? findFn(ref, thingData, {mode: 'quiet'}) : null),
-      },
+  outputs: ['#resolvedContribs'],
+
+  steps: () => [
+    raiseOutputWithoutDependency({
+      dependency: input('from'),
+      mode: input.value('empty'),
+      output: input.value({
+        ['#resolvedContribs']: [],
+      }),
     }),
 
-    // Corresponding dynamic property to contribsByRef, which takes the values
-    // in the provided property and searches the object's artistData for
-    // matching actual Artist objects. The computed structure has the same form
-    // as contribsByRef, but with Artist objects instead of string references:
-    //
-    //     [
-    //         {who: (an Artist), what: 'Viola'},
-    //         {who: (an Artist), what: null},
-    //         ...
-    //     ]
-    //
-    // Contributions whose "who" values don't match anything in artistData are
-    // filtered out. (So if the list is all empty, chances are that either the
-    // reference list is somehow messed up, or artistData isn't being provided
-    // properly.)
-    dynamicContribs: (contribsByRefProperty) => ({
-      flags: {expose: true},
-      expose: {
-        dependencies: ['artistData', contribsByRefProperty],
-        compute: ({artistData, [contribsByRefProperty]: contribsByRef}) =>
-          contribsByRef && artistData
-            ? contribsByRef
-                .map(({who: ref, what}) => ({
-                  who: find.artist(ref, artistData),
-                  what,
-                }))
-                .filter(({who}) => who)
-            : [],
-      },
+    withPropertiesFromList({
+      list: input('from'),
+      properties: input.value(['who', 'what']),
+      prefix: input.value('#contribs'),
     }),
 
-    // Dynamically inherit a contribution list from some other object, if it
-    // hasn't been overridden on this object. This is handy for solo albums
-    // where all tracks have the same artist, for example.
-    dynamicInheritContribs: (
-      // If this property is explicitly false, the contribution list returned
-      // will always be empty.
-      nullerProperty,
-
-      // Property holding contributions on the current object.
-      contribsByRefProperty,
-
-      // Property holding corresponding "default" contributions on the parent
-      // object, which will fallen back to if the object doesn't have its own
-      // contribs.
-      parentContribsByRefProperty,
-
-      // Data array to search in and "find" function to locate parent object
-      // (which will be passed the child object and the wiki data array).
-      thingDataProperty,
-      findFn
-    ) => ({
-      flags: {expose: true},
-      expose: {
-        dependencies: [
-          contribsByRefProperty,
-          thingDataProperty,
-          nullerProperty,
-          'artistData',
-        ].filter(Boolean),
-
-        compute({
-          [Thing.instance]: thing,
-          [nullerProperty]: nuller,
-          [contribsByRefProperty]: contribsByRef,
-          [thingDataProperty]: thingData,
-          artistData,
-        }) {
-          if (!artistData) return [];
-          if (nuller === false) return [];
-          const refs =
-            contribsByRef ??
-            findFn(thing, thingData, {mode: 'quiet'})?.[parentContribsByRefProperty];
-          if (!refs) return [];
-          return refs
-            .map(({who: ref, what}) => ({
-              who: find.artist(ref, artistData),
-              what,
-            }))
-            .filter(({who}) => who);
-        },
+    withResolvedReferenceList({
+      list: '#contribs.who',
+      data: 'artistData',
+      find: input.value(find.artist),
+      notFoundMode: input('notFoundMode'),
+    }).outputs({
+      ['#resolvedReferenceList']: '#contribs.who',
+    }),
+
+    {
+      dependencies: ['#contribs.who', '#contribs.what'],
+
+      compute(continuation, {
+        ['#contribs.who']: who,
+        ['#contribs.what']: what,
+      }) {
+        filterMultipleArrays(who, what, (who, _what) => who);
+        return continuation({
+          ['#resolvedContribs']: stitchArrays({who, what}),
+        });
       },
+    },
+  ],
+});
+
+// Shorthand for exiting if the contribution list (usually a property's update
+// value) resolves to empty - ensuring that the later computed results are only
+// returned if these contributions are present.
+export const exitWithoutContribs = templateCompositeFrom({
+  annotation: `exitWithoutContribs`,
+
+  inputs: {
+    contribs: input({
+      validate: isContributionList,
+      acceptsNull: true,
     }),
 
-    // Nice 'n simple shorthand for an exposed-only flag which is true when any
-    // contributions are present in the specified property.
-    contribsPresent: (contribsByRefProperty) => ({
-      flags: {expose: true},
-      expose: {
-        dependencies: [contribsByRefProperty],
-        compute({
-          [contribsByRefProperty]: contribsByRef,
-        }) {
-          return !empty(contribsByRef);
-        },
-      }
+    value: input({defaultValue: null}),
+  },
+
+  steps: () => [
+    withResolvedContribs({
+      from: input('contribs'),
     }),
 
-    // Neat little shortcut for "reversing" the reference lists stored on other
-    // things - for example, tracks specify a "referenced tracks" property, and
-    // you would use this to compute a corresponding "referenced *by* tracks"
-    // property. Naturally, the passed ref list property is of the things in the
-    // wiki data provided, not the requesting Thing itself.
-    reverseReferenceList: (thingDataProperty, referencerRefListProperty) => ({
-      flags: {expose: true},
+    withResultOfAvailabilityCheck({
+      from: '#resolvedContribs',
+      mode: input.value('empty'),
+    }),
 
-      expose: {
-        dependencies: [thingDataProperty],
+    {
+      dependencies: ['#availability', input('value')],
+      compute: (continuation, {
+        ['#availability']: availability,
+        [input('value')]: value,
+      }) =>
+        (availability
+          ? continuation()
+          : continuation.exit(value)),
+    },
+  ],
+});
+
+// Resolves a reference by using the provided find function to match it
+// within the provided thingData dependency. This will early exit if the
+// data dependency is null, or, if notFoundMode is set to 'exit', if the find
+// function doesn't match anything for the reference. Otherwise, the data
+// object is provided on the output dependency; or null, if the reference
+// doesn't match anything or itself was null to begin with.
+export const withResolvedReference = templateCompositeFrom({
+  annotation: `withResolvedReference`,
+
+  inputs: {
+    ref: input({type: 'string', acceptsNull: true}),
+
+    data: inputWikiData({allowMixedTypes: false}),
+    find: input({type: 'function'}),
+
+    notFoundMode: input({
+      validate: is('null', 'exit'),
+      defaultValue: 'null',
+    }),
+  },
+
+  outputs: ['#resolvedReference'],
+
+  steps: () => [
+    raiseOutputWithoutDependency({
+      dependency: input('ref'),
+      output: input.value({
+        ['#resolvedReference']: null,
+      }),
+    }),
 
-        compute: ({[thingDataProperty]: thingData, [Thing.instance]: thing}) =>
-          thingData?.filter(t => t[referencerRefListProperty].includes(thing)) ?? [],
+    exitWithoutDependency({
+      dependency: input('data'),
+    }),
+
+    {
+      dependencies: [
+        input('ref'),
+        input('data'),
+        input('find'),
+        input('notFoundMode'),
+      ],
+
+      compute(continuation, {
+        [input('ref')]: ref,
+        [input('data')]: data,
+        [input('find')]: findFunction,
+        [input('notFoundMode')]: notFoundMode,
+      }) {
+        const match = findFunction(ref, data, {mode: 'quiet'});
+
+        if (match === null && notFoundMode === 'exit') {
+          return continuation.exit(null);
+        }
+
+        return continuation.raiseOutput({
+          ['#resolvedReference']: match ?? null,
+        });
       },
+    },
+  ],
+});
+
+// Resolves a list of references, with each reference matched with provided
+// data in the same way as withResolvedReference. This will early exit if the
+// data dependency is null (even if the reference list is empty). By default
+// it will filter out references which don't match, but this can be changed
+// to early exit ({notFoundMode: 'exit'}) or leave null in place ('null').
+export const withResolvedReferenceList = templateCompositeFrom({
+  annotation: `withResolvedReferenceList`,
+
+  inputs: {
+    list: input({
+      validate: validateArrayItems(isString),
+      acceptsNull: true,
     }),
 
-    // Corresponding function for single references. Note that the return value
-    // is still a list - this is for matching all the objects whose single
-    // reference (in the given property) matches this Thing.
-    reverseSingleReference: (thingDataProperty, referencerRefListProperty) => ({
-      flags: {expose: true},
+    data: inputWikiData({allowMixedTypes: false}),
+    find: input({type: 'function'}),
 
-      expose: {
-        dependencies: [thingDataProperty],
+    notFoundMode: input({
+      validate: is('exit', 'filter', 'null'),
+      defaultValue: 'filter',
+    }),
+  },
 
-        compute: ({[thingDataProperty]: thingData, [Thing.instance]: thing}) =>
-          thingData?.filter((t) => t[referencerRefListProperty] === thing) ?? [],
-      },
+  outputs: ['#resolvedReferenceList'],
+
+  steps: () => [
+    exitWithoutDependency({
+      dependency: input('data'),
+      value: input.value([]),
     }),
 
-    // General purpose wiki data constructor, for properties like artistData,
-    // trackData, etc.
-    wikiData: (thingClass) => ({
-      flags: {update: true},
-      update: {
-        validate: validateArrayItems(validateInstanceOf(thingClass)),
-      },
+    raiseOutputWithoutDependency({
+      dependency: input('list'),
+      mode: input.value('empty'),
+      output: input.value({
+        ['#resolvedReferenceList']: [],
+      }),
     }),
 
-    // This one's kinda tricky: it parses artist "references" from the
-    // commentary content, and finds the matching artist for each reference.
-    // This is mostly useful for credits and listings on artist pages.
-    commentatorArtists: () => ({
-      flags: {expose: true},
+    {
+      dependencies: [input('list'), input('data'), input('find')],
+      compute: (continuation, {
+        [input('list')]: list,
+        [input('data')]: data,
+        [input('find')]: findFunction,
+      }) =>
+        continuation({
+          '#matches': list.map(ref => findFunction(ref, data, {mode: 'quiet'})),
+        }),
+    },
 
-      expose: {
-        dependencies: ['artistData', 'commentary'],
-
-        compute: ({artistData, commentary}) =>
-          artistData && commentary
-            ? Array.from(
-                new Set(
-                  Array.from(
-                    commentary
-                      .replace(/<\/?b>/g, '')
-                      .matchAll(/<i>(?<who>.*?):<\/i>/g)
-                  ).map(({groups: {who}}) =>
-                    find.artist(who, artistData, {mode: 'quiet'})
-                  )
-                )
-              )
-            : [],
+    {
+      dependencies: ['#matches'],
+      compute: (continuation, {'#matches': matches}) =>
+        (matches.every(match => match)
+          ? continuation.raiseOutput({
+              ['#resolvedReferenceList']: matches,
+            })
+          : continuation()),
+    },
+
+    {
+      dependencies: ['#matches', input('notFoundMode')],
+      compute(continuation, {
+        ['#matches']: matches,
+        [input('notFoundMode')]: notFoundMode,
+      }) {
+        switch (notFoundMode) {
+          case 'exit':
+            return continuation.exit([]);
+
+          case 'filter':
+            return continuation.raiseOutput({
+              ['#resolvedReferenceList']:
+                matches.filter(match => match),
+            });
+
+          case 'null':
+            return continuation.raiseOutput({
+              ['#resolvedReferenceList']:
+                matches.map(match => match ?? null),
+            });
+
+          default:
+            throw new TypeError(`Expected notFoundMode to be exit, filter, or null`);
+        }
       },
-    }),
-  };
+    },
+  ],
+});
 
-  // Default custom inspect function, which may be overridden by Thing
-  // subclasses. This will be used when displaying aggregate errors and other
-  // command-line logging - it's the place to provide information useful in
-  // identifying the Thing being presented.
-  [inspect.custom]() {
-    const cname = this.constructor.name;
+// Check out the info on reverseReferenceList!
+// This is its composable form.
+export const withReverseReferenceList = templateCompositeFrom({
+  annotation: `withReverseReferenceList`,
 
-    return (
-      (this.name ? `${cname} ${color.green(`"${this.name}"`)}` : `${cname}`) +
-      (this.directory ? ` (${color.blue(Thing.getReference(this))})` : '')
-    );
-  }
+  inputs: {
+    data: inputWikiData({allowMixedTypes: false}),
+    list: input({type: 'string'}),
+  },
 
-  static getReference(thing) {
-    if (!thing.constructor[Thing.referenceType]) {
-      throw TypeError(`Passed Thing is ${thing.constructor.name}, which provides no [Thing.referenceType]`);
-    }
+  outputs: ['#reverseReferenceList'],
 
-    if (!thing.directory) {
-      throw TypeError(`Passed ${thing.constructor.name} is missing its directory`);
-    }
+  steps: () => [
+    exitWithoutDependency({
+      dependency: input('data'),
+      value: input.value([]),
+    }),
 
-    return `${thing.constructor[Thing.referenceType]}:${thing.directory}`;
-  }
-}
+    {
+      dependencies: [input.myself(), input('data'), input('list')],
+
+      compute: (continuation, {
+        [input.myself()]: thisThing,
+        [input('data')]: data,
+        [input('list')]: refListProperty,
+      }) =>
+        continuation({
+          ['#reverseReferenceList']:
+            data.filter(thing => thing[refListProperty].includes(thisThing)),
+        }),
+    },
+  ],
+});