init claude-code

utils/sliceAnsi.ts

@@ -0,0 +1,91 @@
+import {
+  type AnsiCode,
+  ansiCodesToString,
+  reduceAnsiCodes,
+  tokenize,
+  undoAnsiCodes,
+} from '@alcalzone/ansi-tokenize'
+import { stringWidth } from '../ink/stringWidth.js'
+
+// A code is an "end code" if its code equals its endCode (e.g., hyperlink close)
+function isEndCode(code: AnsiCode): boolean {
+  return code.code === code.endCode
+}
+
+// Filter to only include "start codes" (not end codes)
+function filterStartCodes(codes: AnsiCode[]): AnsiCode[] {
+  return codes.filter(c => !isEndCode(c))
+}
+
+/**
+ * Slice a string containing ANSI escape codes.
+ *
+ * Unlike the slice-ansi package, this properly handles OSC 8 hyperlink
+ * sequences because @alcalzone/ansi-tokenize tokenizes them correctly.
+ */
+export default function sliceAnsi(
+  str: string,
+  start: number,
+  end?: number,
+): string {
+  // Don't pass `end` to tokenize — it counts code units, not display cells,
+  // so it drops tokens early for text with zero-width combining marks.
+  const tokens = tokenize(str)
+  let activeCodes: AnsiCode[] = []
+  let position = 0
+  let result = ''
+  let include = false
+
+  for (const token of tokens) {
+    // Advance by display width, not code units. Combining marks (Devanagari
+    // matras, virama, diacritics) are width 0 — counting them via .length
+    // advanced position past `end` early and truncated the slice. Callers
+    // pass start/end in display cells (via stringWidth), so position must
+    // track the same units.
+    const width =
+      token.type === 'ansi' ? 0 : token.fullWidth ? 2 : stringWidth(token.value)
+
+    // Break AFTER trailing zero-width marks — a combining mark attaches to
+    // the preceding base char, so "भा" (भ + ा, 1 display cell) sliced at
+    // end=1 must include the ा. Breaking on position >= end BEFORE the
+    // zero-width check would drop it and render भ bare. ANSI codes are
+    // width 0 but must NOT be included past end (they open new style runs
+    // that leak into the undo sequence), so gate on char type too. The
+    // !include guard ensures empty slices (start===end) stay empty even
+    // when the string starts with a zero-width char (BOM, ZWJ).
+    if (end !== undefined && position >= end) {
+      if (token.type === 'ansi' || width > 0 || !include) break
+    }
+
+    if (token.type === 'ansi') {
+      activeCodes.push(token)
+      if (include) {
+        // Emit all ANSI codes during the slice
+        result += token.code
+      }
+    } else {
+      if (!include && position >= start) {
+        // Skip leading zero-width marks at the start boundary — they belong
+        // to the preceding base char in the left half. Without this, the
+        // mark appears in BOTH halves: left+right ≠ original. Only applies
+        // when start > 0 (otherwise there's no preceding char to own it).
+        if (start > 0 && width === 0) continue
+        include = true
+        // Reduce and filter to only active start codes
+        activeCodes = filterStartCodes(reduceAnsiCodes(activeCodes))
+        result = ansiCodesToString(activeCodes)
+      }
+
+      if (include) {
+        result += token.value
+      }
+
+      position += width
+    }
+  }
+
+  // Only undo start codes that are still active
+  const activeStartCodes = filterStartCodes(reduceAnsiCodes(activeCodes))
+  result += ansiCodesToString(undoAnsiCodes(activeStartCodes))
+  return result
+}