+/* string-lerp - progressively turn one string into another
+ Copyright 2014 Joe Wreschnig
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+*/
+
+/* @license Copyright 2014 Joe Wreschnig - GNU GPL v2 or later */
+
(function (exports) {
"use strict";
var MAX_MATRIX_SIZE = 256 * 256;
- function levenshteinMatrix(s, t) {
- /** Calculate the Levenshtein edit distance matrix for two strings
+ function costMatrix(source, target, ins, del, sub) {
+ /** Calculate the Levenshtein cost matrix for source and target
+
+ If source and target are strings, they cannot contain any
+ astral or combining codepoints. Such data must be passed
+ as arrays of strings with one element per glyph.
+
+ ins, del, and sub are the costs for insertion, deletion,
+ and substition respectively. Their default value is 1. If
+ only ins is passed, del and sub are set to the same cost.
+ If ins and del are passed, sub is set to the more
+ expensive of the two.
+
+ The matrix is returned as a flat typed array.
- The matrix is returned as a flat unsigned typed array.
-
Following http://en.wikipedia.org/wiki/Levenshtein_distance
*/
- var m = s.length + 1;
- var n = t.length + 1;
+ ins = ins === undefined ? 1 : (ins | 0);
+ del = (del | 0) || ins;
+ sub = (sub | 0) || Math.max(ins, del);
+ var m = source.length + 1;
+ var n = target.length + 1;
var d = new Uint32Array(m * n);
var i, j;
for (i = 1; i < m; ++i)
d[j] = j;
for (j = 1; j < n; ++j)
for (i = 1; i < m; ++i)
- if (s[i - 1] === t[j - 1])
+ if (source[i - 1] === target[j - 1])
d[n * i + j] = d[n * (i - 1) + j - 1];
else
- d[n * i + j] = 1 + Math.min(d[n * (i - 1) + j ],
- d[n * i + j - 1],
- d[n * (i - 1) + j - 1]);
+ d[n * i + j] = Math.min(del + d[n * (i - 1) + j ],
+ ins + d[n * i + j - 1],
+ sub + d[n * (i - 1) + j - 1]);
return d;
}
- function editPath(d, t) {
- /** Given a Levenshtein matrix and target, create an edit list */
- var path = []
- var j = t.length;
+ // First, note that deletion is just substition with nothing, so
+ // any DEL operation can be replaced by a SUB. Second, the
+ // operation code *is* the necessary slice offset for applying the
+ // diff.
+ var INS = 0, SUB = 1;
+
+ function editPath(costs, target) {
+ /** Given a cost matrix and a target, create an edit list */
+ var path = [];
+ var j = target.length;
var n = j + 1;
- var i = d.length / n - 1;
+ var i = costs.length / n - 1;
while (i || j) {
- var sub = (i && j) ? d[n * (i - 1) + j - 1] : Infinity;
- var del = i ? d[n * (i - 1) + j] : Infinity;
- var ins = j ? d[n * i + j - 1] : Infinity;
+ var sub = (i && j) ? costs[n * (i - 1) + j - 1] : Infinity;
+ var del = i ? costs[n * (i - 1) + j] : Infinity;
+ var ins = j ? costs[n * i + j - 1] : Infinity;
if (sub <= ins && sub <= del) {
- if (d[n * i + j] !== d[n * (i - 1) + j - 1])
- path.push(["sub", i - 1, t[j - 1]]);
+ if (costs[n * i + j] !== costs[n * (i - 1) + j - 1])
+ path.push([SUB, i - 1, target[j - 1]]);
--i; --j;
} else if (ins <= del) {
- path.push(["ins", i, t[j - 1]]);
+ path.push([INS, i, target[j - 1]]);
--j;
} else {
- path.push(["del", i - 1]);
+ path.push([SUB, i - 1, ""]);
--i;
}
}
return path;
}
- function diff(s, t) {
- /** Create a diff between string s and t */
- return editPath(levenshteinMatrix(s, t), t);
+ function diff(source, target, ins, del, sub) {
+ /** Create a diff between string source and target
+
+ ins, del, and sub are as passed to levenshtein
+ */
+ return editPath(costMatrix(source, target, ins, del, sub), target);
}
- function patch(edits, s) {
+ function patch(diff, source) {
/** Apply the list of edits to s */
+ var edit;
var i;
- for (i = 0; i < edits.length; ++i) {
- var edit = edits[i];
- switch (edit[0]) {
- case "sub":
- s = s.slice(0, edit[1]) + edit[2] + s.slice(edit[1] + 1);
- break;
- case "ins":
- s = s.slice(0, edit[1]) + edit[2] + s.slice(edit[1]);
- break;
- case "del":
- s = s.slice(0, edit[1]) + s.slice(edit[1] + 1);
- break;
+
+ if (Array.isArray(source)) {
+ for (i = 0; i < diff.length; ++i) {
+ edit = diff[i];
+ source.splice(edit[1], edit[0], edit[2]);
+ }
+ } else {
+ for (i = 0; i < diff.length; ++i) {
+ edit = diff[i];
+ var head = source.slice(0, edit[1]);
+ var tail = source.slice(edit[1] + edit[0]);
+ source = head + edit[2] + tail;
}
}
- return s;
+ return source;
}
+ var MULTI = /[\uD800-\uDBFF][\uDC00-\uDFFF]|[\u0300-\u036F\u1DC0-\u1DFF\u20D0-\u20FF\uFE20-\uFE2F]/;
+
+ var GLYPH = /([\0-\u02FF\u0370-\u1DBF\u1E00-\u20CF\u2100-\uD7FF\uDC00-\uFE1F\uFE30-\uFFFF]|[\uD800-\uDBFF][\uDC00-\uDFFF]|[\uD800-\uDBFF])([\u0300-\u036F\u1DC0-\u1DFF\u20D0-\u20FF\uFE20-\uFE2F]*)/g;
+
function diffLerp(a, b, p) {
- /** Interpolate between two strings based on edit distance
+ /** Interpolate between two strings based on edit operations
This interpolation algorithm applys a partial edit of one
string into the other. This produces nice looking results,
compute the edits. It is not recommended for strings
longer than a few hundred characters.
*/
- var edits = diff(a, b);
- var partial = edits.slice(0, Math.round(p * edits.length));
- return patch(partial, a);
+
+ // If given strings with astral codepoints or combining
+ // characters, split them into arrays of "glyphs" first,
+ // do the edit on the list of "glyphs", and rejoin them.
+ //
+ // This split is not perfect for all languages, but at least
+ // it won't create invalid surrogate pairs or orphaned
+ // combining characters.
+ if (a.match && a.match(MULTI) || b.match && b.match(MULTI)) {
+ var ca = a.match(GLYPH) || [];
+ var cb = b.match(GLYPH) || [];
+ return diffLerp(ca, cb, p).join("");
+ }
+
+ // The edit path works from the string end, forwards, because
+ // that's how Levenshtein edits work. To match LTR reading
+ // direction (and the behavior of fastLerp), swap the strings
+ // and invert the parameter when editing.
+ var edits = diff(b, a, 2, 2, 3);
+ var partial = edits.slice(0, Math.round((1 - p) * edits.length));
+ return patch(partial, b);
}
- var NUMBERS = /(-?\d+(?:\.\d+)?)/g
+ var NUMBERS = /(-?\d+(?:\.\d+)?)/g;
function areNumericTwins(a, b) {
/** Check if a and b differ only in numerals
is clamped to an integer.
For example, numericLerp("0.0", "100", 0.123) === "12.3"
- because the "." in "0.0" is intepreted as a decimal point.
- But numericLerp("0.", "100.", 0.123) === "12." because the
- strings are interpreted as integers followed by a full
- stop.
+ because the "." in "0.0" is interpreted as a decimal
+ point. But numericLerp("0.", "100.", 0.123) === "12."
+ because the strings are interpreted as integers followed
+ by a full stop.
Calling this functions on strings that differ in more than
numerals gives undefined results.
var aParts = a.split(NUMBERS);
var bParts = b.split(NUMBERS);
for (var i = 1; i < aParts.length; i += 2) {
- var part = nlerp(+aParts[i], +bParts[i], p)
+ var part = nlerp(+aParts[i], +bParts[i], p);
if (aParts[i].indexOf(".") === -1 && bParts[i].indexOf(".") === -1)
part = Math.round(part);
aParts[i] = part.toString();
front of one string with another. This approach is fast
but does not look good when the strings are similar.
*/
- var alen = Math.round(a.length * p);
- var blen = Math.round(b.length * p);
- return b.substring(0, blen) + a.substring(alen, a.length);
+
+ // TODO: Consider fast-pathing this even more for very large
+ // strings, e.g. in the megabyte range. These are large enough
+ // that
+ if (a.match(MULTI) || b.match(MULTI)) {
+ var ca = a.match(GLYPH) || [];
+ var cb = b.match(GLYPH) || [];
+ var calen = Math.round(ca.length * p);
+ var cblen = Math.round(cb.length * p);
+ var r = cb.slice(0, cblen);
+ r.push.apply(r, ca.slice(calen, ca.length));
+ return r.join("");
+ } else {
+ var alen = Math.round(a.length * p);
+ var blen = Math.round(b.length * p);
+ return b.substring(0, blen) + a.substring(alen, a.length);
+ }
}
function lerp(a, b, p) {
if (p === 1) return b;
if (areNumericTwins(a, b))
- return numericLerp(a, b, p)
+ return numericLerp(a, b, p);
// Numeric lerps should over- and under-shoot when fed numbers
// outside 0 to 1, but other types cannot.
if (p > 1) return b;
var n = a.length * b.length;
- return (n && n < MAX_MATRIX_SIZE)
- ? diffLerp(a, b, p)
- : fastLerp(a, b, p);
+ return ((n && n < MAX_MATRIX_SIZE) ? diffLerp : fastLerp)(a, b, p);
}
- exports.levenshteinMatrix = levenshteinMatrix;
+ exports.costMatrix = costMatrix;
exports.patch = patch;
exports.diff = diff;
exports.fastLerp = fastLerp;