import type { MessageBlock, RoutineEventBlock } from "@rakazo/contracts";
import { formatCron, isOneShotRoutineCrons } from "./cron.js";

/** A message that is only timeline lines, shown without a speaker, bubble or reactions. */
export function isRoutineEventMessage(blocks: readonly MessageBlock[]): boolean {
  return (
    blocks.length > 0 &&
    blocks.every((block) => block.kind === "event" || block.kind === "autopilot")
  );
}

/** The blocks with every line about `routineId` marked removed, or null when nothing changes. */
export function markRoutineEventsRemoved(
  blocks: readonly MessageBlock[],
  routineId: string,
): MessageBlock[] | null {
  let changed = false;
  const next = blocks.map((block) => {
    if (block.kind !== "event" || block.routineId !== routineId || block.removed) return block;
    changed = true;
    return { ...block, removed: true };
  });
  return changed ? next : null;
}

/** How a later turn reads the line, so the bot knows what it set up and what is gone. */
export function routineEventHistoryText(block: RoutineEventBlock): string {
  if (block.removed) return `[routine removed: ${block.name}]`;
  const verb = block.event === "routine.updated" ? "updated" : "set up";
  const schedule = isOneShotRoutineCrons(block.crons)
    ? `once at ${block.nextRunAt ?? "an unknown time"}`
    : `${block.crons.map(formatCron).join(", ")}, ${block.timezone}`;
  return `[routine ${verb}: ${block.name} (${schedule})]`;
}

/** The parts of a routine schedule a one-line summary needs; clients word it in their locale. */
export type RoutineScheduleShape =
  | { kind: "once" }
  | { kind: "hourly" }
  | { kind: "minutes" | "hours"; every: number }
  | { kind: "daily" | "weekdays"; hour: number; minute: number }
  | { kind: "weekly"; weekday: number; hour: number; minute: number }
  | { kind: "monthly"; day: number; hour: number; minute: number }
  | { kind: "other" };

const CLOCK_FIELD = /^\d{1,2}$/;

export function routineScheduleShape(crons: readonly string[]): RoutineScheduleShape {
  if (isOneShotRoutineCrons([...crons])) return { kind: "once" };
  if (crons.length !== 1) return { kind: "other" };
  const parts = crons[0]!.trim().split(/\s+/);
  if (parts.length !== 5) return { kind: "other" };
  const [minute, hour, day, month, weekday] = parts as [string, string, string, string, string];
  if (month !== "*") return { kind: "other" };
  const step = (field: string) => /^\*\/(\d+)$/.exec(field)?.[1];
  if (day === "*" && weekday === "*") {
    if (minute === "0" && hour === "*") return { kind: "hourly" };
    const minuteStep = step(minute);
    if (minuteStep && hour === "*") return { kind: "minutes", every: Number(minuteStep) };
    const hourStep = step(hour);
    if (minute === "0" && hourStep) return { kind: "hours", every: Number(hourStep) };
  }
  if (!CLOCK_FIELD.test(minute) || !CLOCK_FIELD.test(hour)) return { kind: "other" };
  const clock = { hour: Number(hour), minute: Number(minute) };
  if (clock.hour > 23 || clock.minute > 59) return { kind: "other" };
  if (day === "*" && weekday === "*") return { kind: "daily", ...clock };
  if (day === "*" && weekday === "1-5") return { kind: "weekdays", ...clock };
  if (day === "*" && /^[0-7]$/.test(weekday)) {
    return { kind: "weekly", weekday: Number(weekday) % 7, ...clock };
  }
  if (weekday === "*" && /^([1-9]|[12]\d|3[01])$/.test(day)) {
    return { kind: "monthly", day: Number(day), ...clock };
  }
  return { kind: "other" };
}