/**
 * DeepSeek Peak Pricing Hours Extension
 *
 * Visual indicator for DeepSeek API peak pricing (Beijing Time UTC+8).
 * Shows a dot + bar in the footer, preserving the original footer info.
 *
 * Peak Hours: 9:00–12:00 & 14:00–18:00 Beijing Time (UTC+8)
 * Weekends (Saturday & Sunday, Beijing Time): the peak/off-peak division
 * doesn't apply — all calls bill uniformly at the off-peak rate.
 */

import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";

// ── Peak window definitions (Beijing Time UTC+8) ──────────────────────────
interface PeakWindow {
  startHour: number; // inclusive
  endHour: number; // exclusive
}

const PEAK_WINDOWS: PeakWindow[] = [
  { startHour: 9, endHour: 12 },
  { startHour: 14, endHour: 18 },
];

// ── Time helpers ──────────────────────────────────────────────────────────

const BJ_OFFSET_MS = 8 * 60 * 60 * 1000;
const WEEKDAY_SHORT = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"] as const;

/** Beijing wall clock as a shifted UTC date — read fields with getters. */
function beijingShifted(t: number): Date {
  return new Date(t + BJ_OFFSET_MS);
}

/** Beijing weekday of an instant (0 = Sunday … 6 = Saturday). */
function beijingWeekdayAt(t: number): number {
  return beijingShifted(t).getUTCDay();
}

/** Get current day/hour/minute in Beijing time (UTC+8) */
function getBeijingNow(): { day: number; hour: number; minute: number } {
  const bj = beijingShifted(Date.now());
  return { day: bj.getUTCDay(), hour: bj.getUTCHours(), minute: bj.getUTCMinutes() };
}

/** Whether the instant is a Beijing weekend — flat off-peak all day. */
function isBeijingWeekend(t: number = Date.now()): boolean {
  const day = beijingWeekdayAt(t);
  return day === 0 || day === 6;
}

/** Whether a Beijing wall hour falls inside a peak window (weekday terms). */
function isPeakHour(hour: number): boolean {
  return PEAK_WINDOWS.some((w) => hour >= w.startHour && hour < w.endHour);
}

/**
 * Given a Beijing hour, return a local Date for that time today
 * (or tomorrow if the hour has already passed in Beijing).
 */
function beijingHourToLocal(hour: number, minute?: number): Date {
  const now = new Date();
  const bjNow = getBeijingNow();

  // Which UTC date the target Beijing hour falls on
  const utcHour = (hour - 8 + 24) % 24;
  let targetDate = new Date(Date.UTC(
    now.getUTCFullYear(),
    now.getUTCMonth(),
    now.getUTCDate(),
    utcHour,
    minute ?? 0,
  ));

  // If already past in Beijing time, push to tomorrow
  const bjTargetHour = (targetDate.getUTCHours() + 8) % 24;
  const bjTargetMin = targetDate.getUTCMinutes();
  if (
    bjTargetHour < bjNow.hour ||
    (bjTargetHour === bjNow.hour && bjTargetMin <= bjNow.minute)
  ) {
    targetDate = new Date(targetDate.getTime() + 24 * 60 * 60 * 1000);
  }

  return targetDate;
}

/**
 * The next local `Date` at which peak billing begins: the earliest peak-window
 * start on a Beijing weekday. Weekends never qualify, so e.g. a Friday
 * evening rolls forward to Monday 09:00 Beijing.
 */
function nextPeakStart(): Date {
  const now = Date.now();
  const base = new Date(now);
  for (let addDays = 0; addDays < 8; addDays++) {
    const dayStart = Date.UTC(
      base.getUTCFullYear(),
      base.getUTCMonth(),
      base.getUTCDate() + addDays,
      0,
      0,
      0,
      0,
    );
    const bjDay = beijingWeekdayAt(dayStart);
    if (bjDay === 0 || bjDay === 6) continue; // weekend: flat off-peak all day
    for (const w of PEAK_WINDOWS) {
      const utcOffsetMs = ((w.startHour - 8 + 24) % 24) * 3_600_000;
      const t = dayStart + utcOffsetMs;
      if (t > now) return new Date(t);
    }
  }
  return new Date(now + 7 * 86_400_000); // unreachable within an 8-day scan
}

/** Format a Date as a short local time string like "09:00" or "14:00" */
function formatLocalTime(d: Date): string {
  const h = String(d.getHours()).padStart(2, "0");
  const m = String(d.getMinutes()).padStart(2, "0");
  return `${h}:${m}`;
}

interface PeakInfo {
  isPeak: boolean;
  currentHour: number;
  currentMinute: number;
  /** True when today (Beijing) is a weekend: flat off-peak, windows ignored. */
  weekend: boolean;
  label: string;
  nextTransition: string; // in local time
}

function getPeakInfo(): PeakInfo {
  const { day, hour, minute } = getBeijingNow();
  const weekend = day === 0 || day === 6;
  const isPeak = !weekend && isPeakHour(hour);

  let transitionLabel: string;
  if (isPeak) {
    const window = PEAK_WINDOWS.find((w) => hour >= w.startHour && hour < w.endHour)!;
    transitionLabel = `until ${formatLocalTime(beijingHourToLocal(window.endHour))}`;
  } else {
    const next = nextPeakStart();
    const aheadMs = next.getTime() - Date.now();
    // Tag the weekday whenever the transition is a day or more away, so a
    // Friday night / weekend reads "next Mon 09:00" instead of implying today.
    const dayTag =
      aheadMs >= 24 * 3_600_000 ? `${WEEKDAY_SHORT[beijingWeekdayAt(next.getTime())]} ` : "";
    transitionLabel = `next ${dayTag}${formatLocalTime(next)}`;
  }

  return {
    isPeak,
    currentHour: hour,
    currentMinute: minute,
    weekend,
    label: isPeak ? "PEAK" : "Off-Peak",
    nextTransition: transitionLabel,
  };
}

// ── Visual bar renderer ───────────────────────────────────────────────────
//
// 24-hour bar in Beijing time. Each column = 1 hour.
// Peak █ (warning), Off-peak ░ (dim), current peak ◆ (bright/bold),
// current off-peak ◇ (accent).
// On Beijing weekends every column renders off-peak.
// Collapses 2h-per-char when width < 26.

const BLOCK_FULL = "█";
const BLOCK_OFF = "░";
const BLOCK_CURRENT_PEAK = "◆";
const BLOCK_CURRENT_OFF = "◇";

function renderBar(peakInfo: PeakInfo, barWidth: number): string {
  const cols: { isPeak: boolean; isCurrent: boolean }[] = [];
  for (let h = 0; h < 24; h++) {
    cols.push({
      isPeak: !peakInfo.weekend && isPeakHour(h),
      isCurrent: h === peakInfo.currentHour,
    });
  }

  if (barWidth >= 26) {
    const chars = cols.map((c) => {
      if (c.isCurrent) return c.isPeak ? BLOCK_CURRENT_PEAK : BLOCK_CURRENT_OFF;
      return c.isPeak ? BLOCK_FULL : BLOCK_OFF;
    });
    return `[${chars.join("")}]`;
  } else if (barWidth >= 14) {
    const merged: string[] = [];
    for (let i = 0; i < 24; i += 2) {
      const a = cols[i]!;
      const b = cols[i + 1]!;
      if (a.isCurrent || b.isCurrent) {
        const current = a.isCurrent ? a : b;
        merged.push(current.isPeak ? BLOCK_CURRENT_PEAK : BLOCK_CURRENT_OFF);
      } else if (a.isPeak || b.isPeak) {
        merged.push(BLOCK_FULL);
      } else {
        merged.push(BLOCK_OFF);
      }
    }
    return `[${merged.join("")}]`;
  }
  return "";
}

// ── Extension ─────────────────────────────────────────────────────────────

export default function (pi: ExtensionAPI) {
  let refreshTimer: ReturnType<typeof setInterval> | null = null;
  let widgetActive = false;

  function stopTimer() {
    if (refreshTimer !== null) {
      clearInterval(refreshTimer);
      refreshTimer = null;
    }
  }

  function startTimer(tui: any) {
    stopTimer();
    refreshTimer = setInterval(() => {
      tui.requestRender();
    }, 30_000);
  }

  // ── Visual bar widget (below the editor) ──────────────────────────
  function showWidget(ctx: { ui: { setWidget: (k: string, v: any, opts?: any) => void; theme: any } }) {
    widgetActive = true;
    ctx.ui.setWidget(
      "deepseek-bar",
      (_tui: any, theme: any) => {
        startTimer(_tui);
        return {
          invalidate() {},
          render() {
            const info = getPeakInfo();

            // Status marker + transition
            const dotColor = info.isPeak ? "error" : "success";
            const statusGlyph = info.isPeak ? BLOCK_CURRENT_PEAK : BLOCK_CURRENT_OFF;
            const dot = theme.fg(
              dotColor,
              info.isPeak ? theme.bold(statusGlyph) : statusGlyph,
            );
            const label = theme.fg(dotColor, theme.bold(` DeepSeek ${info.label} `));

            // Build the bar (estimate ~50 cols available for the widget area)
            const rawBar = renderBar(info, 48);
            const barColored = rawBar
              .split("")
              .map((ch: string) => {
                if (ch === BLOCK_CURRENT_PEAK) return theme.fg("error", theme.bold(ch));
                if (ch === BLOCK_CURRENT_OFF) return theme.fg("accent", ch);
                if (ch === BLOCK_FULL) return theme.fg("muted", ch);
                return theme.fg("dim", ch);
              })
              .join("");

            const transition = theme.fg("dim", ` ${info.nextTransition} local`);
            return [dot + label + barColored + transition];
          },
        };
      },
      { placement: "belowEditor" },
    );
  }

  function hideWidget(ctx: { ui: { setWidget: (k: string, v: undefined) => void } }) {
    widgetActive = false;
    ctx.ui.setWidget("deepseek-bar", undefined);
    stopTimer();
  }

  // ── Command ───────────────────────────────────────────────────────
  pi.registerCommand("ds-peak", {
    description: "Toggle DeepSeek peak pricing indicator",
    handler: async (_args, ctx) => {
      if (!ctx.hasUI) {
        const info = getPeakInfo();
        console.log(
          `DeepSeek peak pricing: ${info.isPeak ? "PEAK NOW" : "Off-Peak"}${info.weekend ? " (weekend rate)" : ""} (${info.nextTransition} local)`,
        );
        return;
      }

      if (widgetActive) {
        hideWidget(ctx);
        ctx.ui.notify("DeepSeek peak indicator hidden", "info");
      } else {
        showWidget(ctx);
        ctx.ui.notify("DeepSeek peak indicator shown", "info");
      }
    },
  });

  // ── Lifecycle ─────────────────────────────────────────────────────
  pi.on("session_start", async (_event, ctx) => {
    stopTimer();
    if (ctx.hasUI) {
      showWidget(ctx);
    }
  });

  pi.on("session_shutdown", () => {
    stopTimer();
  });
}