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// Baseline implementation shared by or underlying reverse lists.
//
// This is a very rudimentary "these compositions have basically the same
// shape but slightly different guts midway through" kind of solution,
// and should use compositional subroutines instead, once those are ready.
//
// But, until then, this has the same effect of avoiding code duplication
// and clearly identifying differences.
//
// ---
//
// This implementation uses a global cache (via WeakMap) to attempt to speed
// up subsequent similar accesses.
//
// This has absolutely not been rigorously tested with altering properties of
// data objects in a wiki data array which is reused. If a new wiki data array
// is used, a fresh cache will always be created.
//
import {input, templateCompositeFrom} from '#composite';
import {sortByDate} from '#sort';
import {stitchArrays} from '#sugar';
import {exitWithoutDependency, raiseOutputWithoutDependency}
from '#composite/control-flow';
import {withFlattenedList, withMappedList} from '#composite/data';
import inputWikiData from '../inputWikiData.js';
export default function withReverseList_template({
annotation,
propertyInputName,
outputName,
customCompositionSteps,
}) {
// Mapping of reference list property to WeakMap.
// Each WeakMap maps a wiki data array to another weak map,
// which in turn maps each referenced thing to an array of
// things referencing it.
const caches = new Map();
return templateCompositeFrom({
annotation,
inputs: {
data: inputWikiData({
allowMixedTypes: true,
}),
[propertyInputName]: input({
type: 'string',
}),
},
outputs: [outputName],
steps: () => [
// Early exit with an empty array if the data list isn't available.
exitWithoutDependency({
dependency: input('data'),
value: input.value([]),
}),
// Raise an empty array (don't early exit) if the data list is empty.
raiseOutputWithoutDependency({
dependency: input('data'),
mode: input.value('empty'),
output: input.value({[outputName]: []}),
}),
// Check for an existing cache record which corresponds to this
// property input and input('data'). If it exists, query it for the
// current thing, and raise that; if it doesn't, create it, put it
// where it needs to be, and provide it so the next steps can fill
// it in.
{
dependencies: [input(propertyInputName), input('data'), input.myself()],
compute: (continuation, {
[input(propertyInputName)]: property,
[input('data')]: data,
[input.myself()]: myself,
}) => {
if (!caches.has(property)) {
const cache = new WeakMap();
caches.set(property, cache);
const cacheRecord = new WeakMap();
cache.set(data, cacheRecord);
return continuation({
['#cacheRecord']: cacheRecord,
});
}
const cache = caches.get(property);
if (!cache.has(data)) {
const cacheRecord = new WeakMap();
cache.set(data, cacheRecord);
return continuation({
['#cacheRecord']: cacheRecord,
});
}
return continuation.raiseOutput({
[outputName]:
cache.get(data).get(myself) ?? [],
});
},
},
...customCompositionSteps(),
// Actually fill in the cache record. Since we're building up a *reverse*
// reference list, track connections in terms of the referenced thing.
// Although we gather all referenced things into a set and provide that
// for sorting purposes in the next step, we *don't* reprovide the cache
// record, because we're mutating that in-place - we'll just reuse its
// existing '#cacheRecord' dependency.
{
dependencies: ['#cacheRecord', '#referencingThings', '#referencedThings'],
compute: (continuation, {
['#cacheRecord']: cacheRecord,
['#referencingThings']: referencingThings,
['#referencedThings']: referencedThings,
}) => {
const allReferencedThings = new Set();
stitchArrays({
referencingThing: referencingThings,
referencedThings: referencedThings,
}).forEach(({referencingThing, referencedThings}) => {
for (const referencedThing of referencedThings) {
if (cacheRecord.has(referencedThing)) {
cacheRecord.get(referencedThing).push(referencingThing);
} else {
cacheRecord.set(referencedThing, [referencingThing]);
allReferencedThings.add(referencedThing);
}
}
});
return continuation({
['#allReferencedThings']:
allReferencedThings,
});
},
},
// Sort the entries in the cache records, too, just by date - the rest of
// sorting should be handled outside of this composition, either preceding
// (changing the 'data' input) or following (sorting the output).
// Again we're mutating in place, so no need to reprovide '#cacheRecord'
// here.
{
dependencies: ['#cacheRecord', '#allReferencedThings'],
compute: (continuation, {
['#cacheRecord']: cacheRecord,
['#allReferencedThings']: allReferencedThings,
}) => {
for (const referencedThing of allReferencedThings) {
if (cacheRecord.has(referencedThing)) {
const referencingThings = cacheRecord.get(referencedThing);
sortByDate(referencingThings);
}
}
return continuation();
},
},
// Then just pluck out the current object from the now-filled cache record!
{
dependencies: ['#cacheRecord', input.myself()],
compute: (continuation, {
['#cacheRecord']: cacheRecord,
[input.myself()]: myself,
}) => continuation({
[outputName]:
cacheRecord.get(myself) ?? [],
}),
},
],
});
}
|
