diff options
author | (quasar) nebula <qznebula@protonmail.com> | 2023-09-08 12:19:49 -0300 |
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committer | (quasar) nebula <qznebula@protonmail.com> | 2023-09-08 12:19:49 -0300 |
commit | 65260d7fc2790ece0c13820ba18bc821163f164e (patch) | |
tree | 020770a2a45a095b059c87f01f0ec904d55bdf54 | |
parent | bf0be010c9d9b860ad42762fc2e373130c7535eb (diff) |
data: new withFlattenedArray, withUnflattenedArray utilities
-rw-r--r-- | src/data/things/composite.js | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/src/data/things/composite.js b/src/data/things/composite.js index 96abf4af..1f6482f6 100644 --- a/src/data/things/composite.js +++ b/src/data/things/composite.js @@ -1072,6 +1072,8 @@ export function raiseWithoutUpdateValue({ ]); } +// Turns an updating property's update value into a dependency, so it can be +// conveniently passed to other functions. export function withUpdateValueAsDependency({ into = '#updateValue', } = {}) { @@ -1086,3 +1088,76 @@ export function withUpdateValueAsDependency({ }, }; } + +// Flattens an array with one level of nested arrays, providing as dependencies +// both the flattened array as well as the original starting indices of each +// successive source array. +export function withFlattenedArray({ + from, + into = '#flattenedArray', + intoIndices = '#flattenedIndices', +}) { + return { + annotation: `withFlattenedArray`, + flags: {expose: true, compose: true}, + + expose: { + mapDependencies: {from}, + mapContinuation: {into, intoIndices}, + + compute({from: sourceArray}, continuation) { + const into = sourceArray.flat(); + const intoIndices = []; + + let lastEndIndex = 0; + for (const {length} of sourceArray) { + intoIndices.push(lastEndIndex); + lastEndIndex += length; + } + + return continuation({into, intoIndices}); + }, + }, + }; +} + +// 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). +export function withUnflattenedArray({ + from, + fromIndices = '#flattenedIndices', + into = '#unflattenedArray', + filter = true, +}) { + return { + annotation: `withUnflattenedArray`, + flags: {expose: true, compose: true}, + + expose: { + mapDependencies: {from, fromIndices}, + mapContinuation: {into}, + compute({from, fromIndices}, continuation) { + const arrays = []; + + for (let i = 0; i < fromIndices.length; i++) { + const startIndex = fromIndices[i]; + const endIndex = + (i === fromIndices.length - 1 + ? from.length + : fromIndices[i + 1]); + + const values = from.slice(startIndex, endIndex); + arrays.push( + (filter + ? values.filter(value => value !== null && value !== undefined) + : values)); + } + + return continuation({into: arrays}); + }, + }, + }; +} |