oppi.li
source dump of claude code
1import {
2 type AnsiCode,
3 ansiCodesToString,
4 reduceAnsiCodes,
5 tokenize,
6 undoAnsiCodes,
7} from '@alcalzone/ansi-tokenize'
8import { stringWidth } from '../ink/stringWidth.js'
9
10// A code is an "end code" if its code equals its endCode (e.g., hyperlink close)
11function isEndCode(code: AnsiCode): boolean {
12 return code.code === code.endCode
13}
14
15// Filter to only include "start codes" (not end codes)
16function filterStartCodes(codes: AnsiCode[]): AnsiCode[] {
17 return codes.filter(c => !isEndCode(c))
18}
19
20/**
21 * Slice a string containing ANSI escape codes.
22 *
23 * Unlike the slice-ansi package, this properly handles OSC 8 hyperlink
24 * sequences because @alcalzone/ansi-tokenize tokenizes them correctly.
25 */
26export default function sliceAnsi(
27 str: string,
28 start: number,
29 end?: number,
30): string {
31 // Don't pass `end` to tokenize — it counts code units, not display cells,
32 // so it drops tokens early for text with zero-width combining marks.
33 const tokens = tokenize(str)
34 let activeCodes: AnsiCode[] = []
35 let position = 0
36 let result = ''
37 let include = false
38
39 for (const token of tokens) {
40 // Advance by display width, not code units. Combining marks (Devanagari
41 // matras, virama, diacritics) are width 0 — counting them via .length
42 // advanced position past `end` early and truncated the slice. Callers
43 // pass start/end in display cells (via stringWidth), so position must
44 // track the same units.
45 const width =
46 token.type === 'ansi' ? 0 : token.fullWidth ? 2 : stringWidth(token.value)
47
48 // Break AFTER trailing zero-width marks — a combining mark attaches to
49 // the preceding base char, so "भा" (भ + ा, 1 display cell) sliced at
50 // end=1 must include the ा. Breaking on position >= end BEFORE the
51 // zero-width check would drop it and render भ bare. ANSI codes are
52 // width 0 but must NOT be included past end (they open new style runs
53 // that leak into the undo sequence), so gate on char type too. The
54 // !include guard ensures empty slices (start===end) stay empty even
55 // when the string starts with a zero-width char (BOM, ZWJ).
56 if (end !== undefined && position >= end) {
57 if (token.type === 'ansi' || width > 0 || !include) break
58 }
59
60 if (token.type === 'ansi') {
61 activeCodes.push(token)
62 if (include) {
63 // Emit all ANSI codes during the slice
64 result += token.code
65 }
66 } else {
67 if (!include && position >= start) {
68 // Skip leading zero-width marks at the start boundary — they belong
69 // to the preceding base char in the left half. Without this, the
70 // mark appears in BOTH halves: left+right ≠ original. Only applies
71 // when start > 0 (otherwise there's no preceding char to own it).
72 if (start > 0 && width === 0) continue
73 include = true
74 // Reduce and filter to only active start codes
75 activeCodes = filterStartCodes(reduceAnsiCodes(activeCodes))
76 result = ansiCodesToString(activeCodes)
77 }
78
79 if (include) {
80 result += token.value
81 }
82
83 position += width
84 }
85 }
86
87 // Only undo start codes that are still active
88 const activeStartCodes = filterStartCodes(reduceAnsiCodes(activeCodes))
89 result += ansiCodesToString(undoAnsiCodes(activeStartCodes))
90 return result
91}