/**
 * tmux capture-pane snapshot.
 *
 * Returns a plain-text snapshot of a pane's visible content.
 * Used by the snapshot route (T-1.5) and the /thumbnail endpoint (T-1.6).
 *
 * Owner: T-1.1
 */

import { execFile } from "node:child_process";
import { promisify } from "node:util";

const execFileAsync = promisify(execFile);

export interface SnapshotOptions {
  /** tmux session name */
  session: string;
  /** pane index within session (default "0.0") */
  pane?: string;
  /** capture width (default: actual pane width) */
  width?: number;
  /** capture height (default: actual pane height) */
  height?: number;
  /** include escape sequences for colour/style (default: false = plain text) */
  escapes?: boolean;
}

/**
 * Capture a plain-text (or escape-annotated) snapshot of a tmux pane.
 * Returns raw text as a string.
 */
export async function capturePane(opts: SnapshotOptions): Promise<string> {
  const { session, pane, escapes = false } = opts;
  // Target just the session when no pane specified — avoids base-index issues.
  const target = pane ? `${session}:${pane}` : session;

  const args = ["capture-pane", "-t", target, "-p"];
  if (escapes) args.push("-e"); // include escape sequences
  // Note: -S/-E (start/end line) omitted — captures current visible content

  const { stdout } = await execFileAsync("tmux", args);
  return stdout;
}

/**
 * Capture a thumbnail-sized snapshot (40×12) for the REST thumbnail endpoint.
 * Returns plain text, trimmed.
 */
export async function captureThumbnail(
  session: string,
  pane?: string,
): Promise<string> {
  // tmux can't resize the capture directly via capture-pane flags, so we
  // capture full content and truncate to 40-char wide × 12 lines.
  const raw = await capturePane({ session, pane, escapes: false });
  const lines = raw.split("\n").slice(0, 12);
  return lines.map((l) => l.slice(0, 40)).join("\n");
}