import { execFile } from "node:child_process";

function execFileAsync(
  file: string,
  args: readonly string[],
  timeout: number,
): Promise<{ stdout: string }> {
  return new Promise((resolve, reject) => {
    execFile(file, args, { timeout }, (error, stdout) => {
      if (error) {
        reject(error);
        return;
      }
      resolve({ stdout });
    });
  });
}

export const DEFAULT_WINDOW_TITLE_LENGTH = 36;

export type TmuxEnvironment = Readonly<{
  TMUX?: string;
  TMUX_PANE?: string;
}>;

export type SetPaneTitleOptions = Readonly<{
  env?: TmuxEnvironment;
  tmuxBin?: string;
  timeoutMs?: number;
  windowTitleLength?: number;
}>;

export type PaneTitleSynchronizer = Readonly<{
  synchronize(name: string | undefined): Promise<boolean>;
  reset(): void;
}>;

export function normalizeSessionName(name: string | undefined): string | undefined {
  const normalized = name?.trim();
  return normalized ? normalized : undefined;
}

export function truncateTitle(title: string, maxLength: number): string {
  const characters = [...title];
  if (maxLength <= 0 || characters.length <= maxLength) {
    return title;
  }
  if (maxLength === 1) {
    return "…";
  }
  return `${characters.slice(0, maxLength - 1).join("")}…`;
}

export function paneTitleArguments(paneId: string, title: string): readonly string[] {
  return ["select-pane", "-t", paneId, "-T", title];
}

export function paneCountArguments(paneId: string): readonly string[] {
  return ["display-message", "-p", "-t", paneId, "#{window_panes}"];
}

export function windowTitleArguments(paneId: string, title: string): readonly string[] {
  return ["rename-window", "-t", paneId, title];
}

export async function setPaneTitle(
  name: string | undefined,
  options: SetPaneTitleOptions = {},
): Promise<boolean> {
  const title = normalizeSessionName(name);
  const env = options.env ?? process.env;
  const paneId = env.TMUX_PANE;
  if (!title || !env.TMUX || !paneId) {
    return false;
  }

  const tmuxBin = options.tmuxBin ?? process.env.PI_TMUX_PANE_TITLE_TMUX_BIN ?? "tmux";
  const timeout = options.timeoutMs ?? 1000;

  try {
    await execFileAsync(tmuxBin, paneTitleArguments(paneId, title), timeout);
  } catch {
    return false;
  }

  try {
    const { stdout } = await execFileAsync(tmuxBin, paneCountArguments(paneId), timeout);
    if (stdout.trim() === "1") {
      const windowTitle = truncateTitle(
        title,
        options.windowTitleLength ?? DEFAULT_WINDOW_TITLE_LENGTH,
      );
      await execFileAsync(tmuxBin, windowTitleArguments(paneId, windowTitle), timeout);
    }
  } catch {
    // The pane title is still useful when window inspection or renaming fails.
  }

  return true;
}

export function createPaneTitleSynchronizer(
  options: SetPaneTitleOptions = {},
): PaneTitleSynchronizer {
  let lastPaneId: string | undefined;
  let lastTitle: string | undefined;

  return {
    async synchronize(name: string | undefined): Promise<boolean> {
      const title = normalizeSessionName(name);
      const env = options.env ?? process.env;
      const paneId = env.TMUX_PANE;
      if (!title || !env.TMUX || !paneId) {
        return false;
      }
      if (paneId === lastPaneId && title === lastTitle) {
        return true;
      }
      const synchronized = await setPaneTitle(title, options);
      if (synchronized) {
        lastPaneId = paneId;
        lastTitle = title;
      }
      return synchronized;
    },
    reset(): void {
      lastPaneId = undefined;
      lastTitle = undefined;
    },
  };
}