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Diffstat (limited to 'alarm/node_modules/graphql/jsutils/suggestionList.js.flow')
-rw-r--r-- | alarm/node_modules/graphql/jsutils/suggestionList.js.flow | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/alarm/node_modules/graphql/jsutils/suggestionList.js.flow b/alarm/node_modules/graphql/jsutils/suggestionList.js.flow new file mode 100644 index 0000000..017e779 --- /dev/null +++ b/alarm/node_modules/graphql/jsutils/suggestionList.js.flow @@ -0,0 +1,138 @@ +// @flow strict +import naturalCompare from './naturalCompare'; + +/** + * Given an invalid input string and a list of valid options, returns a filtered + * list of valid options sorted based on their similarity with the input. + */ +export default function suggestionList( + input: string, + options: $ReadOnlyArray<string>, +): Array<string> { + const optionsByDistance = Object.create(null); + const lexicalDistance = new LexicalDistance(input); + + const threshold = Math.floor(input.length * 0.4) + 1; + for (const option of options) { + const distance = lexicalDistance.measure(option, threshold); + if (distance !== undefined) { + optionsByDistance[option] = distance; + } + } + + return Object.keys(optionsByDistance).sort((a, b) => { + const distanceDiff = optionsByDistance[a] - optionsByDistance[b]; + return distanceDiff !== 0 ? distanceDiff : naturalCompare(a, b); + }); +} + +/** + * Computes the lexical distance between strings A and B. + * + * The "distance" between two strings is given by counting the minimum number + * of edits needed to transform string A into string B. An edit can be an + * insertion, deletion, or substitution of a single character, or a swap of two + * adjacent characters. + * + * Includes a custom alteration from Damerau-Levenshtein to treat case changes + * as a single edit which helps identify mis-cased values with an edit distance + * of 1. + * + * This distance can be useful for detecting typos in input or sorting + */ +class LexicalDistance { + _input: string; + _inputLowerCase: string; + _inputArray: Array<number>; + _rows: [Array<number>, Array<number>, Array<number>]; + + constructor(input: string) { + this._input = input; + this._inputLowerCase = input.toLowerCase(); + this._inputArray = stringToArray(this._inputLowerCase); + + this._rows = [ + new Array(input.length + 1).fill(0), + new Array(input.length + 1).fill(0), + new Array(input.length + 1).fill(0), + ]; + } + + measure(option: string, threshold: number): number | void { + if (this._input === option) { + return 0; + } + + const optionLowerCase = option.toLowerCase(); + + // Any case change counts as a single edit + if (this._inputLowerCase === optionLowerCase) { + return 1; + } + + let a = stringToArray(optionLowerCase); + let b = this._inputArray; + + if (a.length < b.length) { + const tmp = a; + a = b; + b = tmp; + } + const aLength = a.length; + const bLength = b.length; + + if (aLength - bLength > threshold) { + return undefined; + } + + const rows = this._rows; + for (let j = 0; j <= bLength; j++) { + rows[0][j] = j; + } + + for (let i = 1; i <= aLength; i++) { + const upRow = rows[(i - 1) % 3]; + const currentRow = rows[i % 3]; + + let smallestCell = (currentRow[0] = i); + for (let j = 1; j <= bLength; j++) { + const cost = a[i - 1] === b[j - 1] ? 0 : 1; + + let currentCell = Math.min( + upRow[j] + 1, // delete + currentRow[j - 1] + 1, // insert + upRow[j - 1] + cost, // substitute + ); + + if (i > 1 && j > 1 && a[i - 1] === b[j - 2] && a[i - 2] === b[j - 1]) { + // transposition + const doubleDiagonalCell = rows[(i - 2) % 3][j - 2]; + currentCell = Math.min(currentCell, doubleDiagonalCell + 1); + } + + if (currentCell < smallestCell) { + smallestCell = currentCell; + } + + currentRow[j] = currentCell; + } + + // Early exit, since distance can't go smaller than smallest element of the previous row. + if (smallestCell > threshold) { + return undefined; + } + } + + const distance = rows[aLength % 3][bLength]; + return distance <= threshold ? distance : undefined; + } +} + +function stringToArray(str: string): Array<number> { + const strLength = str.length; + const array = new Array(strLength); + for (let i = 0; i < strLength; ++i) { + array[i] = str.charCodeAt(i); + } + return array; +} |