/**
 * KHAELOR
 * File: src/tui/renderer/terminal.ts
 * Description: Terminal session guard — raw mode + bracketed paste on mount, guaranteed restore on exit and on crash.
 *
 * Author: Simon-Pierre Boucher
 * Contact: contact@spboucher.ai
 */

import {
  BRACKETED_PASTE_OFF,
  BRACKETED_PASTE_ON,
  SHOW_CURSOR,
  SYNC_OFF,
} from "./ansi.js";

export interface TerminalSession {
  /** Restore the terminal to its pre-mount state. Idempotent. */
  restore(): void;
}

/**
 * Enter KHAELOR's terminal state: raw mode, bracketed paste. Installs
 * process-level handlers so the terminal is restored on normal exit, on
 * SIGTERM/SIGHUP, and on crash (uncaughtException / unhandledRejection) —
 * a dead KHAELOR must never leave the user's shell in raw mode with a
 * hidden cursor (CLAUDE.md §14).
 */
export function enterTerminal(
  stdin: NodeJS.ReadStream,
  stdout: NodeJS.WriteStream,
): TerminalSession {
  const wasRaw = stdin.isTTY ? stdin.isRaw : false;
  if (stdin.isTTY) stdin.setRawMode(true);
  stdin.resume();
  stdout.write(BRACKETED_PASTE_ON);

  let restored = false;
  const restore = (): void => {
    if (restored) return;
    restored = true;
    // Undo everything a paint could have left half-done.
    stdout.write(SYNC_OFF + SHOW_CURSOR + BRACKETED_PASTE_OFF);
    if (stdin.isTTY) stdin.setRawMode(wasRaw);
    stdin.pause();
    process.off("exit", onExit);
    process.off("SIGTERM", onSignal);
    process.off("SIGHUP", onSignal);
    process.off("uncaughtException", onFatal);
    process.off("unhandledRejection", onFatal);
  };

  const onExit = (): void => {
    restore();
  };
  const onSignal = (): void => {
    restore();
    process.exit(1);
  };
  const onFatal = (error: unknown): void => {
    restore();
    const message = error instanceof Error ? (error.stack ?? error.message) : String(error);
    process.stderr.write(`\nkhaelor: fatal error\n${message}\n`);
    process.exit(1);
  };

  process.on("exit", onExit);
  process.on("SIGTERM", onSignal);
  process.on("SIGHUP", onSignal);
  process.on("uncaughtException", onFatal);
  process.on("unhandledRejection", onFatal);

  return { restore };
}