| 18 | * character differences are not appropriate for this line pairing. |
| 19 | */ |
| 20 | export function computeCharacterDiffs( |
| 21 | beforeText: string, |
| 22 | afterText: string, |
| 23 | ): [CharacterDiff[], CharacterDiff[]] | null { |
| 24 | const beforeWords = splitIntoWords(beforeText); |
| 25 | const afterWords = splitIntoWords(afterText); |
| 26 | const diffs = Diff.diffArrays(beforeWords, afterWords); |
| 27 | |
| 28 | // Suppress char-by-char diffs if there's less than 50% character overlap. |
| 29 | // The one exception is pure whitespace diffs, which should always be shown. |
| 30 | const minEqualFrac = 0.5; |
| 31 | let equalCount = 0; |
| 32 | let charCount = 0; |
| 33 | let beforeAllWhitespace = true; |
| 34 | let afterAllWhitespace = true; |
| 35 | for (const diff of diffs) { |
| 36 | const len = strArrayLen(diff.value); |
| 37 | if (diff.added) { |
| 38 | afterAllWhitespace &&= diff.value.every(allWhitespace); |
| 39 | charCount += len; |
| 40 | } else if (diff.removed) { |
| 41 | beforeAllWhitespace &&= diff.value.every(allWhitespace); |
| 42 | charCount += len; |
| 43 | } else { |
| 44 | // equal |
| 45 | equalCount += 2 * len; |
| 46 | charCount += 2 * len; |
| 47 | if (beforeAllWhitespace || afterAllWhitespace) { |
| 48 | const allSpace = diff.value.every(allWhitespace); |
| 49 | beforeAllWhitespace &&= allSpace; |
| 50 | afterAllWhitespace &&= allSpace; |
| 51 | } |
| 52 | } |
| 53 | } |
| 54 | if (equalCount < minEqualFrac * charCount && !(beforeAllWhitespace && afterAllWhitespace)) { |
| 55 | return null; |
| 56 | } |
| 57 | |
| 58 | let beforeOut: CharacterDiff[] = []; |
| 59 | let afterOut: CharacterDiff[] = []; // (span class, start, end) triples |
| 60 | let beforeIdx = 0; |
| 61 | let afterIdx = 0; |
| 62 | for (const diff of diffs) { |
| 63 | const len = strArrayLen(diff.value); |
| 64 | if (diff.added) { |
| 65 | afterOut.push(['insert', afterIdx, afterIdx + len]); |
| 66 | afterIdx += len; |
| 67 | } else if (diff.removed) { |
| 68 | beforeOut.push(['delete', beforeIdx, beforeIdx + len]); |
| 69 | beforeIdx += len; |
| 70 | } else { |
| 71 | beforeOut.push([null, beforeIdx, beforeIdx + len]); |
| 72 | afterOut.push([null, afterIdx, afterIdx + len]); |
| 73 | beforeIdx += len; |
| 74 | afterIdx += len; |
| 75 | } |
| 76 | } |
| 77 | beforeOut = simplifyCodes(beforeOut); |