/**
 * Pi Nudge Extension
 *
 * Sends native terminal notifications when pi needs attention and the
 * terminal is not focused. Suppresses notifications when you're already
 * looking at the terminal.
 *
 * Other extensions can trigger notifications via pi.events:
 *   pi.events.emit("nudge", { title: "Pi", body: "Needs approval" });
 *
 * Notification protocols:
 * - OSC 9: Ghostty, iTerm2
 * - OSC 99: Kitty
 * - OSC 777: WezTerm, rxvt-unicode (fallback)
 * - tmux passthrough wrapper
 */

import type { ExtensionAPI, ExtensionUIContext } from "@mariozechner/pi-coding-agent";

// ---------------------------------------------------------------------------
// Focus tracking compatibility
// ---------------------------------------------------------------------------

type FocusAwareUI = ExtensionUIContext & { isTerminalFocused(): boolean };

function hasFocusTracking(ui: ExtensionUIContext): ui is FocusAwareUI {
  return typeof (ui as Partial<FocusAwareUI>).isTerminalFocused === "function";
}

// ---------------------------------------------------------------------------
// Notification transport
// ---------------------------------------------------------------------------

type EncodeNotification = (title: string, body: string) => string[];

const encoders: Record<string, EncodeNotification> = {
  ghostty: osc9,
  iterm2: osc9,
  kitty: osc99,
  default: osc777,
};

// OSC 9 has no title field; the terminal provides its own header (at least in Ghostty).
function osc9(_title: string, body: string): string[] {
  return [`\x1b]9;${body}\x07`];
}

function osc99(title: string, body: string): string[] {
  return [
    `\x1b]99;i=1:d=0;${title}\x1b\\`,
    `\x1b]99;i=1:p=body;${body}\x1b\\`,
  ];
}

function osc777(title: string, body: string): string[] {
  return [`\x1b]777;notify;${title};${body}\x07`];
}

function detectTerminal(): string {
  if (process.env.KITTY_WINDOW_ID) return "kitty";
  if (process.env.TERM_PROGRAM === "ghostty") return "ghostty";
  if (process.env.TERM_PROGRAM === "iTerm.app" || process.env.ITERM_SESSION_ID) return "iterm2";
  return "default";
}

function tmuxPassthrough(sequence: string): string {
  if (!process.env.TMUX) return sequence;
  const escaped = sequence.split("\x1b").join("\x1b\x1b");
  return `\x1bPtmux;${escaped}\x1b\\`;
}

// ---------------------------------------------------------------------------
// Extension
// ---------------------------------------------------------------------------

const TITLE = "π";

interface NudgeEvent {
  title?: string;
  body?: string;
}

export default function (pi: ExtensionAPI) {
  let isTerminalFocused: (() => boolean) | undefined;

  const terminal = detectTerminal();
  const encode = encoders[terminal] ?? encoders.default!;

  function nudge(title: string, body: string): void {
    if (isTerminalFocused?.()) return;
    for (const sequence of encode(title, body)) {
      process.stdout.write(tmuxPassthrough(sequence));
    }
  }

  // Detect focus tracking support on session start
  pi.on("session_start", async (_event, ctx) => {
    if (!ctx.hasUI) return;

    if (hasFocusTracking(ctx.ui)) {
      const ui = ctx.ui;
      isTerminalFocused = () => ui.isTerminalFocused();
    } else {
      ctx.ui.notify(
        "[pi-nudge] Terminal focus detection is unavailable in this pi build. Notifications will always be sent, but your terminal may suppress them if focused.",
        "info"
      );
    }
  });

  // Notify when agent finishes a turn
  pi.on("agent_end", async (_event, ctx) => {
    if (!ctx.hasUI) return;
    nudge(TITLE, "Ready for input");
  });

  // Allow other extensions to trigger notifications via pi.events
  pi.events.on("nudge", (data: unknown) => {
    const event = (data ?? {}) as NudgeEvent;
    nudge(event.title ?? TITLE, event.body ?? "Needs attention");
  });
}