Function findPlainTextUrlAt

src/ink/selection.ts:272–359

(
  screen: Screen,
  col: number,
  row: number,
)

 * cell has no OSC 8 hyperlink.
 */
export function findPlainTextUrlAt(
  screen: Screen,
  col: number,
  row: number,
): string | undefined {
  if (row < 0 || row >= screen.height) return undefined
  const width = screen.width
  const noSelect = screen.noSelect
  const rowOff = row * width

  let c = col
  if (c > 0) {
    const cell = cellAt(screen, c, row)
    if (cell && cell.width === CellWidth.SpacerTail) c -= 1
  }
  if (c < 0 || c >= width || noSelect[rowOff + c] === 1) return undefined

  const startCell = cellAt(screen, c, row)
  if (!startCell || !isUrlChar(startCell.char)) return undefined

  // Expand left/right to the bounds of the URL-char run. URLs are ASCII
  // (CellWidth.Narrow, 1 codeunit), so hitting a non-ASCII/wide/spacer
  // cell is a boundary — no need to step over spacers like wordBoundsAt.
  let lo = c
  while (lo > 0) {
    const prev = lo - 1
    if (noSelect[rowOff + prev] === 1) break
    const pc = cellAt(screen, prev, row)
    if (!pc || pc.width !== CellWidth.Narrow || !isUrlChar(pc.char)) break
    lo = prev
  }
  let hi = c
  while (hi < width - 1) {
    const next = hi + 1
    if (noSelect[rowOff + next] === 1) break
    const nc = cellAt(screen, next, row)
    if (!nc || nc.width !== CellWidth.Narrow || !isUrlChar(nc.char)) break
    hi = next
  }

  let token = ''
  for (let i = lo; i <= hi; i++) token += cellAt(screen, i, row)!.char

  // 1 cell = 1 char across [lo, hi] (ASCII-only run), so string index =
  // column offset. Find the last scheme anchor at or before the click —
  // a run like `https://a.com,https://b.com` has two, and clicking the
  // second should return the second URL, not the greedy match of both.
  const clickIdx = c - lo
  const schemeRe = /(?:https?|file):\/\//g
  let urlStart = -1
  let urlEnd = token.length
  for (let m; (m = schemeRe.exec(token)); ) {
    if (m.index > clickIdx) {
      urlEnd = m.index
      break
    }
    urlStart = m.index
  }