hermes-agent/ui-tui/packages/hermes-ink/src/ink/wrap-text.ts

import sliceAnsi from '../utils/sliceAnsi.js'

import { stringWidth } from './stringWidth.js'
import type { Styles } from './styles.js'
import { wrapAnsi } from './wrapAnsi.js'

const ELLIPSIS = '…'

// sliceAnsi may include a boundary-spanning wide char (e.g. CJK at position
// end-1 with width 2 overshoots by 1). Retry with a tighter bound once.
function sliceFit(text: string, start: number, end: number): string {
  const s = sliceAnsi(text, start, end)

  return stringWidth(s) > end - start ? sliceAnsi(text, start, end - 1) : s
}

function truncate(text: string, columns: number, position: 'start' | 'middle' | 'end'): string {
  if (columns < 1) {
    return ''
  }

  if (columns === 1) {
    return ELLIPSIS
  }

  const length = stringWidth(text)

  if (length <= columns) {
    return text
  }

  if (position === 'start') {
    return ELLIPSIS + sliceFit(text, length - columns + 1, length)
  }

  if (position === 'middle') {
    const half = Math.floor(columns / 2)

    return sliceFit(text, 0, half) + ELLIPSIS + sliceFit(text, length - (columns - half) + 1, length)
  }

  return sliceFit(text, 0, columns - 1) + ELLIPSIS
}

export default function wrapText(text: string, maxWidth: number, wrapType: Styles['textWrap']): string {
  if (wrapType === 'wrap') {
    return wrapAnsi(text, maxWidth, {
      trim: false,
      hard: true
    })
  }

  if (wrapType === 'wrap-trim') {
    return wrapAnsi(text, maxWidth, {
      trim: true,
      hard: true
    })
  }

  if (wrapType!.startsWith('truncate')) {
    let position: 'end' | 'middle' | 'start' = 'end'

    if (wrapType === 'truncate-middle') {
      position = 'middle'
    }

    if (wrapType === 'truncate-start') {
      position = 'start'
    }

    return truncate(text, maxWidth, position)
  }

  return text
}