/**
 * .docx Import module for Atmosphere Docs.
 *
 * Uses mammoth.js to convert .docx files to HTML, then feeds the result
 * into the TipTap editor.
 */
import type { Editor } from '@tiptap/core';
import type { DocxConvertResult, DocxMessage } from './types.js';

/**
 * Convert a .docx ArrayBuffer to HTML using mammoth.js.
 * Pure async function — testable without DOM.
 */
export async function convertDocxToHtml(arrayBuffer: ArrayBuffer): Promise<DocxConvertResult> {
  const mammoth = await import('mammoth');

  // mammoth accepts { arrayBuffer } in the browser and { buffer } in Node.js.
  // Detect environment and pass the right input format.
  const isNode = typeof process !== 'undefined' && process.versions?.node;
  const input = isNode ? { buffer: Buffer.from(arrayBuffer) } : { arrayBuffer };

  const options = {
    styleMap: [
      "p[style-name='Heading 1'] => h1:fresh",
      "p[style-name='Heading 2'] => h2:fresh",
      "p[style-name='Heading 3'] => h3:fresh",
      "p[style-name='Heading 4'] => h4:fresh",
      "p[style-name='Heading 5'] => h5:fresh",
      "p[style-name='Heading 6'] => h6:fresh",
    ],
  };

  const result = await mammoth.convertToHtml(input, options);
  return {
    html: result.value,
    messages: (result.messages || []) as DocxMessage[],
  };
}

/**
 * Validate that the given ArrayBuffer looks like a valid .docx file.
 * A .docx is a ZIP file, so it starts with the PK signature (0x504B0304).
 */
export function isValidDocx(arrayBuffer: ArrayBuffer): boolean {
  if (!arrayBuffer || arrayBuffer.byteLength < 4) return false;
  const view = new Uint8Array(arrayBuffer);
  return view[0] === 0x50 && view[1] === 0x4B && view[2] === 0x03 && view[3] === 0x04;
}

/**
 * Import a .docx File object into the TipTap editor.
 * DOM-coupled entry point — not unit-testable.
 */
export async function importDocx(
  file: File,
  editor: Editor,
  showToast: (message: string, duration: number) => void,
): Promise<void> {
  try {
    const arrayBuffer = await file.arrayBuffer();

    if (!isValidDocx(arrayBuffer)) {
      showToast('Invalid .docx file — the file appears to be corrupt', 5000);
      return;
    }

    const { html, messages } = await convertDocxToHtml(arrayBuffer);

    if (!html || html.trim() === '') {
      showToast('The .docx file appears to be empty', 3000);
      return;
    }

    editor.commands.setContent(html);

    const warnings = messages.filter((m: DocxMessage) => m.type === 'warning');
    if (warnings.length > 0) {
      showToast(`Imported "${file.name}" with ${warnings.length} warning(s)`, 4000);
    } else {
      showToast(`Imported "${file.name}" successfully`, 3000);
    }
  } catch (err) {
    console.error('docx import error:', err);
    showToast('Failed to import .docx file — it may be corrupt or unsupported', 5000);
  }
}