Function setTaskDueAtIndex

packages/shared-domain/src/tasklists.ts:198–218

(
  markdown: string,
  taskIndex: number,
  due: string | null
)

/** Replace, insert, or remove the `due:YYYY-MM-DD` token on the task
 *  line at `taskIndex`. Pass `null` to clear. */
export function setTaskDueAtIndex(
  markdown: string,
  taskIndex: number,
  due: string | null
): string {
  return editTaskAtIndex(markdown, taskIndex, (match) => {
    const prefix = match[1]
    const checkChar = match[2]
    const tailWithBracket = match[3]
    if (!tailWithBracket.startsWith(']')) return null
    const tail = tailWithBracket.slice(1)
    const cleaned = tail.replace(DUE_TOKEN_RE, '$1').replace(/\s{2,}/g, ' ')
    let nextTail: string
    if (due) {
      nextTail = `${cleaned.replace(/\s+$/u, '')} due:${due}`
    } else {
      nextTail = cleaned.replace(/\s+$/u, '')
    }
    return `${prefix}${checkChar}]${nextTail}`
  })
}

/** Replace everything after the checkbox on the task line at `taskIndex` with
 *  `text` (verbatim — the caller owns any `due:`/`!priority` tokens). Used by