import { writeFile } from 'node:fs/promises';
import { dialog, ipcMain, type BrowserWindow } from 'electron';

interface TranscriptSaveRequest {
  defaultPath?: unknown;
  markdown?: unknown;
}

const MAX_TRANSCRIPT_MARKDOWN_BYTES = 10 * 1024 * 1024;

function safeDefaultPath(value: unknown): string {
  if (typeof value !== 'string') return 'chat-transcript.md';
  const fileName = value.split(/[\\/]/).filter(Boolean).at(-1)?.trim();
  if (!fileName) return 'chat-transcript.md';
  return fileName.toLowerCase().endsWith('.md') ? fileName : `${fileName}.md`;
}

export function registerTranscriptExportHandler(mainWindow: BrowserWindow): void {
  ipcMain.handle('transcript:save', async (_event, request: TranscriptSaveRequest) => {
    if (typeof request?.markdown !== 'string') {
      throw new Error('Invalid transcript markdown');
    }
    if (Buffer.byteLength(request.markdown, 'utf8') > MAX_TRANSCRIPT_MARKDOWN_BYTES) {
      throw new Error('Transcript is too large');
    }

    let selected: Electron.SaveDialogReturnValue;
    try {
      selected = await dialog.showSaveDialog(mainWindow, {
        defaultPath: safeDefaultPath(request.defaultPath),
        filters: [{ name: 'Markdown', extensions: ['md'] }],
      });
    } catch {
      throw new Error('Failed to save transcript');
    }
    if (selected.canceled || !selected.filePath) return { status: 'cancelled' as const };

    try {
      await writeFile(selected.filePath, request.markdown, 'utf8');
    } catch {
      throw new Error('Failed to save transcript');
    }
    return { status: 'saved' as const };
  });
}