"use client";

import { CalendarDays, Clock3 } from "lucide-react";

/** 发帖截止时间：快捷天数 + 指定时刻（分栏 + 快捷芯片） */

export type DeadlineMode = "preset" | "custom";

function pad2(n: number) {
  return String(n).padStart(2, "0");
}

/** datetime-local 值（本地时区） */
export function toLocalInputValue(d: Date): string {
  return `${d.getFullYear()}-${pad2(d.getMonth() + 1)}-${pad2(d.getDate())}T${pad2(d.getHours())}:${pad2(d.getMinutes())}`;
}

/** 默认自定义：从现在起 +N 天 */
export function defaultCustomLocal(days = 7): string {
  const d = new Date();
  d.setDate(d.getDate() + days);
  d.setHours(18, 0, 0, 0);
  return toLocalInputValue(d);
}

/** 本地 datetime-local → RFC3339（UTC） */
export function localInputToRFC3339(local: string): string | null {
  const t = Date.parse(local);
  if (!Number.isFinite(t)) return null;
  return new Date(t).toISOString().replace(/\.\d{3}Z$/, "Z");
}

export function formatLocalPreview(local: string): string {
  const t = Date.parse(local);
  if (!Number.isFinite(t)) return "";
  try {
    return new Date(t).toLocaleString("zh-CN", {
      year: "numeric",
      month: "long",
      day: "numeric",
      weekday: "short",
      hour: "2-digit",
      minute: "2-digit",
      hour12: false,
    });
  } catch {
    return local;
  }
}

function splitLocal(v: string): { date: string; time: string } {
  const [date = "", rawTime = ""] = (v || "").split("T");
  const time = (rawTime || "18:00").slice(0, 5);
  return { date, time: /^\d{2}:\d{2}$/.test(time) ? time : "18:00" };
}

function joinLocal(date: string, time: string): string {
  if (!date) return "";
  const t = /^\d{2}:\d{2}$/.test(time) ? time : "18:00";
  return `${date}T${t}`;
}

function startOfDay(d: Date): Date {
  const x = new Date(d);
  x.setHours(0, 0, 0, 0);
  return x;
}

function withTime(base: Date, hours: number, minutes: number): Date {
  const d = new Date(base);
  d.setHours(hours, minutes, 0, 0);
  return d;
}

/** 至少晚于当前 1 小时；不满足则推到合法时刻 */
function ensureMinLead(d: Date): Date {
  const min = new Date(Date.now() + 60 * 60 * 1000);
  min.setSeconds(0, 0);
  return d.getTime() < min.getTime() ? min : d;
}

type QuickSet = { id: string; label: string; build: () => Date };

function buildQuickSets(): QuickSet[] {
  const now = new Date();
  return [
    {
      id: "tonight",
      label: "今晚 22:00",
      build: () => ensureMinLead(withTime(now, 22, 0)),
    },
    {
      id: "tomorrow-noon",
      label: "明天中午",
      build: () => {
        const d = new Date(now);
        d.setDate(d.getDate() + 1);
        return withTime(d, 12, 0);
      },
    },
    {
      id: "plus3-eve",
      label: "3 天后晚",
      build: () => {
        const d = new Date(now);
        d.setDate(d.getDate() + 3);
        return withTime(d, 21, 0);
      },
    },
    {
      id: "sunday-eve",
      label: "本周日晚",
      build: () => {
        const d = startOfDay(now);
        const day = d.getDay(); // 0=日
        const add = day === 0 ? 7 : 7 - day;
        d.setDate(d.getDate() + add);
        return ensureMinLead(withTime(d, 21, 0));
      },
    },
  ];
}

const TIME_CHIPS = ["09:00", "12:00", "18:00", "21:00", "22:00", "23:59"] as const;

export default function DeadlinePicker({
  label = "截止时间",
  presets,
  mode,
  onModeChange,
  days,
  onDaysChange,
  customLocal,
  onCustomLocalChange,
  disabled,
  hint,
}: {
  label?: string;
  presets: readonly number[];
  mode: DeadlineMode;
  onModeChange: (m: DeadlineMode) => void;
  days: number;
  onDaysChange: (d: number) => void;
  customLocal: string;
  onCustomLocalChange: (v: string) => void;
  disabled?: boolean;
  hint?: string;
}) {
  const minDate = toLocalInputValue(new Date()).slice(0, 10);
  const maxDate = toLocalInputValue(new Date(Date.now() + 90 * 24 * 60 * 60 * 1000)).slice(0, 10);
  const { date, time } = splitLocal(customLocal);
  const quickSets = buildQuickSets();

  const applyCustom = (next: Date) => {
    onCustomLocalChange(toLocalInputValue(ensureMinLead(next)));
  };

  const patchDate = (nextDate: string) => {
    onCustomLocalChange(joinLocal(nextDate, time || "18:00"));
  };

  const patchTime = (nextTime: string) => {
    const baseDate = date || toLocalInputValue(new Date()).slice(0, 10);
    onCustomLocalChange(joinLocal(baseDate, nextTime));
  };

  const enterCustom = () => {
    onModeChange("custom");
    if (!customLocal) onCustomLocalChange(defaultCustomLocal(days || 7));
  };

  return (
    <div className="j13-deadline-picker">
      <div className="j13-deadline-picker-head">
        <div className="j13-deadline-picker-label">{label}</div>
        <div className="j13-deadline-picker-modes" role="tablist" aria-label={label}>
          <button
            type="button"
            role="tab"
            aria-selected={mode === "preset"}
            className={`j13-deadline-mode${mode === "preset" ? " is-on" : ""}`}
            disabled={disabled}
            onClick={() => onModeChange("preset")}
          >
            快捷时长
          </button>
          <button
            type="button"
            role="tab"
            aria-selected={mode === "custom"}
            className={`j13-deadline-mode${mode === "custom" ? " is-on" : ""}`}
            disabled={disabled}
            onClick={enterCustom}
          >
            指定时刻
          </button>
        </div>
      </div>

      {mode === "preset" ? (
        <div className="j13-deadline-presets" role="group" aria-label="快捷天数">
          {presets.map((d) => (
            <button
              key={d}
              type="button"
              className={`j13-deadline-chip${days === d ? " is-on" : ""}`}
              disabled={disabled}
              aria-pressed={days === d}
              onClick={() => onDaysChange(d)}
            >
              {d} 天
            </button>
          ))}
        </div>
      ) : (
        <div className="j13-deadline-custom">
          <div className="j13-deadline-fields">
            <label className="j13-deadline-field">
              <span className="j13-deadline-field-icon" aria-hidden>
                <CalendarDays size={15} strokeWidth={2} />
              </span>
              <span className="j13-deadline-field-meta">
                <span className="j13-deadline-field-label">日期</span>
                <input
                  type="date"
                  className="j13-deadline-field-input"
                  value={date}
                  min={minDate}
                  max={maxDate}
                  disabled={disabled}
                  onChange={(e) => patchDate(e.target.value)}
                  aria-label="截止日期"
                />
              </span>
            </label>
            <label className="j13-deadline-field">
              <span className="j13-deadline-field-icon" aria-hidden>
                <Clock3 size={15} strokeWidth={2} />
              </span>
              <span className="j13-deadline-field-meta">
                <span className="j13-deadline-field-label">时刻</span>
                <input
                  type="time"
                  className="j13-deadline-field-input"
                  value={time}
                  disabled={disabled}
                  onChange={(e) => patchTime(e.target.value)}
                  aria-label="截止时刻"
                />
              </span>
            </label>
          </div>

          <div className="j13-deadline-quick" role="group" aria-label="快捷设到">
            <span className="j13-deadline-quick-label">快捷</span>
            <div className="j13-deadline-quick-chips">
              {quickSets.map((q) => (
                <button
                  key={q.id}
                  type="button"
                  className="j13-deadline-chip j13-deadline-chip-sm"
                  disabled={disabled}
                  onClick={() => applyCustom(q.build())}
                >
                  {q.label}
                </button>
              ))}
            </div>
          </div>

          <div className="j13-deadline-quick" role="group" aria-label="常用时刻">
            <span className="j13-deadline-quick-label">时刻</span>
            <div className="j13-deadline-quick-chips">
              {TIME_CHIPS.map((t) => (
                <button
                  key={t}
                  type="button"
                  className={`j13-deadline-chip j13-deadline-chip-sm${time === t ? " is-on" : ""}`}
                  disabled={disabled || !date}
                  aria-pressed={time === t}
                  onClick={() => patchTime(t)}
                >
                  {t}
                </button>
              ))}
            </div>
          </div>

          {customLocal ? (
            <p className="j13-deadline-preview">
              将于 <strong>{formatLocalPreview(customLocal)}</strong> 截止
            </p>
          ) : null}
        </div>
      )}
      {hint ? <p className="j13-deadline-hint">{hint}</p> : null}
    </div>
  );
}