Added 'Fuzzy Match' operation

src/core/lib/FuzzyMatch.mjs

@@ -0,0 +1,253 @@
+/**
+ * LICENSE
+ *
+ *   This software is dual-licensed to the public domain and under the following
+ *   license: you are granted a perpetual, irrevocable license to copy, modify,
+ *   publish, and distribute this file as you see fit.
+ *
+ * VERSION
+ *   0.1.0  (2016-03-28)  Initial release
+ *
+ * AUTHOR
+ *   Forrest Smith
+ *
+ * CONTRIBUTORS
+ *   J<EFBFBD>rgen Tjern<EFBFBD> - async helper
+ *   Anurag Awasthi - updated to 0.2.0
+ */
+
+export const DEFAULT_WEIGHTS = {
+    sequentialBonus: 15, // bonus for adjacent matches
+    separatorBonus: 30, // bonus if match occurs after a separator
+    camelBonus: 30, // bonus if match is uppercase and prev is lower
+    firstLetterBonus: 15, // bonus if the first letter is matched
+
+    leadingLetterPenalty: -5, // penalty applied for every letter in str before the first match
+    maxLeadingLetterPenalty: -15, // maximum penalty for leading letters
+    unmatchedLetterPenalty: -1
+};
+
+/**
+ * Does a fuzzy search to find pattern inside a string.
+ * @param {string} pattern        pattern to search for
+ * @param {string} str            string which is being searched
+ * @param {boolean} global        whether to search for all matches or just one
+ * @returns [boolean, number]       a boolean which tells if pattern was
+ *                                  found or not and a search score
+ */
+export function fuzzyMatch(pattern, str, global=false, weights=DEFAULT_WEIGHTS) {
+    const recursionCount = 0;
+    const recursionLimit = 10;
+    const matches = [];
+    const maxMatches = 256;
+
+    if (!global) {
+        return fuzzyMatchRecursive(
+            pattern,
+            str,
+            0 /* patternCurIndex */,
+            0 /* strCurrIndex */,
+            null /* srcMatches */,
+            matches,
+            maxMatches,
+            0 /* nextMatch */,
+            recursionCount,
+            recursionLimit,
+            weights
+        );
+    }
+
+    // Return all matches
+    let foundMatch = true,
+        score,
+        idxs,
+        strCurrIndex = 0;
+    const results = [];
+
+    while (foundMatch) {
+        [foundMatch, score, idxs] = fuzzyMatchRecursive(
+            pattern,
+            str,
+            0 /* patternCurIndex */,
+            strCurrIndex,
+            null /* srcMatches */,
+            matches,
+            maxMatches,
+            0 /* nextMatch */,
+            recursionCount,
+            recursionLimit,
+            weights
+        );
+        if (foundMatch) results.push([foundMatch, score, [...idxs]]);
+        strCurrIndex = idxs[idxs.length - 1] + 1;
+    }
+    return results;
+}
+
+/**
+ * Recursive helper function
+ */
+function fuzzyMatchRecursive(
+    pattern,
+    str,
+    patternCurIndex,
+    strCurrIndex,
+    srcMatches,
+    matches,
+    maxMatches,
+    nextMatch,
+    recursionCount,
+    recursionLimit,
+    weights
+) {
+    let outScore = 0;
+
+    // Return if recursion limit is reached.
+    if (++recursionCount >= recursionLimit) {
+        return [false, outScore, []];
+    }
+
+    // Return if we reached ends of strings.
+    if (patternCurIndex === pattern.length || strCurrIndex === str.length) {
+        return [false, outScore, []];
+    }
+
+    // Recursion params
+    let recursiveMatch = false;
+    let bestRecursiveMatches = [];
+    let bestRecursiveScore = 0;
+
+    // Loop through pattern and str looking for a match.
+    let firstMatch = true;
+    while (patternCurIndex < pattern.length && strCurrIndex < str.length) {
+        // Match found.
+        if (
+            pattern[patternCurIndex].toLowerCase() === str[strCurrIndex].toLowerCase()
+        ) {
+            if (nextMatch >= maxMatches) {
+                return [false, outScore, []];
+            }
+
+            if (firstMatch && srcMatches) {
+                matches = [...srcMatches];
+                firstMatch = false;
+            }
+
+            const [matched, recursiveScore, recursiveMatches] = fuzzyMatchRecursive(
+                pattern,
+                str,
+                patternCurIndex,
+                strCurrIndex + 1,
+                matches,
+                recursiveMatches,
+                maxMatches,
+                nextMatch,
+                recursionCount,
+                recursionLimit,
+                weights
+            );
+
+            if (matched) {
+                // Pick best recursive score.
+                if (!recursiveMatch || recursiveScore > bestRecursiveScore) {
+                    bestRecursiveMatches = [...recursiveMatches];
+                    bestRecursiveScore = recursiveScore;
+                }
+                recursiveMatch = true;
+            }
+
+            matches[nextMatch++] = strCurrIndex;
+            ++patternCurIndex;
+        }
+        ++strCurrIndex;
+    }
+
+    const matched = patternCurIndex === pattern.length;
+
+    if (matched) {
+        outScore = 100;
+
+        // Apply leading letter penalty
+        let penalty = weights.leadingLetterPenalty * matches[0];
+        penalty =
+            penalty < weights.maxLeadingLetterPenalty ?
+                weights.maxLeadingLetterPenalty :
+                penalty;
+        outScore += penalty;
+
+        // Apply unmatched penalty
+        const unmatched = str.length - nextMatch;
+        outScore += weights.unmatchedLetterPenalty * unmatched;
+
+        // Apply ordering bonuses
+        for (let i = 0; i < nextMatch; i++) {
+            const currIdx = matches[i];
+
+            if (i > 0) {
+                const prevIdx = matches[i - 1];
+                if (currIdx === prevIdx + 1) {
+                    outScore += weights.sequentialBonus;
+                }
+            }
+
+            // Check for bonuses based on neighbor character value.
+            if (currIdx > 0) {
+                // Camel case
+                const neighbor = str[currIdx - 1];
+                const curr = str[currIdx];
+                if (
+                    neighbor !== neighbor.toUpperCase() &&
+                    curr !== curr.toLowerCase()
+                ) {
+                    outScore += weights.camelBonus;
+                }
+                const isNeighbourSeparator = neighbor === "_" || neighbor === " ";
+                if (isNeighbourSeparator) {
+                    outScore += weights.separatorBonus;
+                }
+            } else {
+                // First letter
+                outScore += weights.firstLetterBonus;
+            }
+        }
+
+        // Return best result
+        if (recursiveMatch && (!matched || bestRecursiveScore > outScore)) {
+            // Recursive score is better than "this"
+            matches = bestRecursiveMatches;
+            outScore = bestRecursiveScore;
+            return [true, outScore, matches];
+        } else if (matched) {
+            // "this" score is better than recursive
+            return [true, outScore, matches];
+        } else {
+            return [false, outScore, matches];
+        }
+    }
+    return [false, outScore, matches];
+}
+
+/**
+ * Turns a list of match indexes into a list of match ranges
+ *
+ * @author n1474335 [n1474335@gmail.com]
+ * @param [number] matches
+ * @returns [[number]]
+ */
+export function calcMatchRanges(matches) {
+    const ranges = [];
+    let start = matches[0],
+        curr = start;
+
+    matches.forEach(m => {
+        if (m === curr || m === curr + 1) curr = m;
+        else {
+            ranges.push([start, curr - start + 1]);
+            start = m;
+            curr = m;
+        }
+    });
+
+    ranges.push([start, curr - start + 1]);
+    return ranges;
+}