Commit 5744d55a authored by Alejandro Celaya's avatar Alejandro Celaya Committed by Alejandro Celaya

Migrate match-quote module to TS

parent 7ab7c23d
import approxSearch from 'approx-string-match';
import type { Match as StringMatch } from 'approx-string-match';
/**
* @typedef {import('approx-string-match').Match} StringMatch
*/
type Match = {
/** Start offset of match in text */
start: number;
/** End offset of match in text */
end: number;
/**
* @typedef Match
* @prop {number} start - Start offset of match in text
* @prop {number} end - End offset of match in text
* @prop {number} score -
/**
* Score for the match between 0 and 1.0, where 1.0 indicates a perfect match
* for the quote and context.
*/
score: number;
};
/**
* Find the best approximate matches for `str` in `text` allowing up to `maxErrors` errors.
*
* @param {string} text
* @param {string} str
* @param {number} maxErrors
* @return {StringMatch[]}
* Find the best approximate matches for `str` in `text` allowing up to
* `maxErrors` errors.
*/
function search(text, str, maxErrors) {
function search(text: string, str: string, maxErrors: number): StringMatch[] {
// Do a fast search for exact matches. The `approx-string-match` library
// doesn't currently incorporate this optimization itself.
let matchPos = 0;
let exactMatches = [];
const exactMatches: StringMatch[] = [];
while (matchPos !== -1) {
matchPos = text.indexOf(str, matchPos);
if (matchPos !== -1) {
......@@ -48,11 +45,8 @@ function search(text, str, maxErrors) {
/**
* Compute a score between 0 and 1.0 for the similarity between `text` and `str`.
*
* @param {string} text
* @param {string} str
*/
function textMatchScore(text, str) {
function textMatchScore(text: string, str: string) {
// `search` will return no matches if either the text or pattern is empty,
// otherwise it will return at least one match if the max allowed error count
// is at least `str.length`.
......@@ -66,22 +60,29 @@ function textMatchScore(text, str) {
return 1 - (matches[0].errors / str.length);
}
type Context = {
/** Expected text before the quote */
prefix?: string;
/** Expected text after the quote */
suffix?: string;
/** Expected offset of match within text */
hint?: number;
};
/**
* Find the best approximate match for `quote` in `text`.
*
* Returns `null` if no match exceeding the minimum quality threshold was found.
*
* @param {string} text - Document text to search
* @param {string} quote - String to find within `text`
* @param {object} context -
* Context in which the quote originally appeared. This is used to choose the
* best match.
* @param {string} [context.prefix] - Expected text before the quote
* @param {string} [context.suffix] - Expected text after the quote
* @param {number} [context.hint] - Expected offset of match within text
* @return {Match|null}
* @param text - Document text to search
* @param quote - String to find within `text`
* @param context - Context in which the quote originally appeared. This is
* used to choose the best match.
* @return `null` if no match exceeding the minimum quality threshold was found.
*/
export function matchQuote(text, quote, context = {}) {
export function matchQuote(
text: string,
quote: string,
context: Context = {}
): Match | null {
if (quote.length === 0) {
return null;
}
......@@ -97,7 +98,7 @@ export function matchQuote(text, quote, context = {}) {
// `O((maxErrors / 32) * text.length)`. See `approx-string-match` docs.
const maxErrors = Math.min(256, quote.length / 2);
// Find closest matches for `quote` in `text` based on edit distance.
// Find the closest matches for `quote` in `text` based on edit distance.
const matches = search(text, quote, maxErrors);
if (matches.length === 0) {
......@@ -106,10 +107,8 @@ export function matchQuote(text, quote, context = {}) {
/**
* Compute a score between 0 and 1.0 for a match candidate.
*
* @param {StringMatch} match
*/
const scoreMatch = match => {
const scoreMatch = (match: StringMatch) => {
const quoteWeight = 50; // Similarity of matched text to quote.
const prefixWeight = 20; // Similarity of text before matched text to `context.prefix`.
const suffixWeight = 20; // Similarity of text after matched text to `context.suffix`.
......@@ -158,7 +157,7 @@ export function matchQuote(text, quote, context = {}) {
score: scoreMatch(m),
}));
// Choose match with highest score.
// Choose match with the highest score.
scoredMatches.sort((a, b) => b.score - a.score);
return scoredMatches[0];
}
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