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Diffstat (limited to 'src/data/composite/data/withUnflattenedList.js')
-rw-r--r-- | src/data/composite/data/withUnflattenedList.js | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/src/data/composite/data/withUnflattenedList.js b/src/data/composite/data/withUnflattenedList.js new file mode 100644 index 0000000..39a666d --- /dev/null +++ b/src/data/composite/data/withUnflattenedList.js @@ -0,0 +1,72 @@ +// After mapping the contents of a flattened array in-place (being careful to +// retain the original indices by replacing unmatched results with null instead +// of filtering them out), this function allows for recombining them. It will +// filter out null and undefined items by default (pass {filter: false} to +// disable this). +// +// See also: +// - withFlattenedList +// +// More list utilities: +// - excludeFromList +// - fillMissingListItems +// - withFilteredList, withMappedList, withSortedList +// - withPropertyFromList, withPropertiesFromList +// + +import {input, templateCompositeFrom} from '#composite'; +import {isWholeNumber, validateArrayItems} from '#validators'; + +export default templateCompositeFrom({ + annotation: `withUnflattenedList`, + + inputs: { + list: input({ + type: 'array', + defaultDependency: '#flattenedList', + }), + + indices: input({ + validate: validateArrayItems(isWholeNumber), + defaultDependency: '#flattenedIndices', + }), + + filter: input({ + type: 'boolean', + defaultValue: true, + }), + }, + + outputs: ['#unflattenedList'], + + steps: () => [ + { + dependencies: [input('list'), input('indices'), input('filter')], + compute(continuation, { + [input('list')]: list, + [input('indices')]: indices, + [input('filter')]: filter, + }) { + const unflattenedList = []; + + for (let i = 0; i < indices.length; i++) { + const startIndex = indices[i]; + const endIndex = + (i === indices.length - 1 + ? list.length + : indices[i + 1]); + + const values = list.slice(startIndex, endIndex); + unflattenedList.push( + (filter + ? values.filter(value => value !== null && value !== undefined) + : values)); + } + + return continuation({ + ['#unflattenedList']: unflattenedList, + }); + }, + }, + ], +}); |