feat: repeat tasks after completion

frontend/src/lib/task-utils.ts

@@ -173,6 +173,33 @@ export function parseTaskRrule(rrule = ''): TaskRepeatConfig {
   }
 }
 
+export type TaskRepeatOption = 'none' | 'daily' | 'weekly' | 'monthly' | 'yearly' | 'after_completion' | 'custom'
+export type TaskRecurrenceRecord = { rrule?: string | null; trigger_mode?: 'scheduled' | 'after_completion'; after_completion_days?: number | null }
+
+export function buildTaskRecurrencePayload(option: TaskRepeatOption, values: { afterCompletionDays: string | number; repeatConfig?: TaskRepeatConfig }) {
+  if (option === 'none') return {}
+  if (option === 'after_completion') {
+    const raw = String(values.afterCompletionDays).trim()
+    const days = Number(raw)
+    if (!/^\d+$/.test(raw) || !Number.isInteger(days) || days < 1 || days > 3650) throw new Error('请输入 1 到 3650 的整数天数')
+    return { trigger_mode: 'after_completion' as const, after_completion_days: days }
+  }
+  const rrule = option === 'custom'
+    ? buildTaskRrule(values.repeatConfig ?? { frequency: 'daily', interval: 1, endMode: 'never' })
+    : `FREQ=${option.toUpperCase()}`
+  return { trigger_mode: 'scheduled' as const, rrule }
+}
+
+export function parseTaskRecurrence(recurrence?: TaskRecurrenceRecord | null) {
+  if (!recurrence) return { option: 'none' as TaskRepeatOption, afterCompletionDays: 1 }
+  if (recurrence.trigger_mode === 'after_completion') {
+    return { option: 'after_completion' as TaskRepeatOption, afterCompletionDays: recurrence.after_completion_days ?? 1 }
+  }
+  const parsed = parseTaskRrule(recurrence.rrule ?? '')
+  const simple = parsed.interval === 1 && !parsed.weekdays?.length && !parsed.monthDays?.length && parsed.endMode === 'never'
+  return { option: (simple ? parsed.frequency : 'custom') as TaskRepeatOption, afterCompletionDays: 1 }
+}
+
 export function defaultTaskDueAt(now = new Date()) {
   const year = now.getFullYear()
   const month = `${now.getMonth() + 1}`.padStart(2, '0')