/**
 * ObsiGate — File & Folder Upload & Drag-and-Drop Core Module (#89).
 *
 * Provides utilities for:
 * - Traversing recursive directories and files from DataTransfer / FileSystem API
 * - Reading files into base64 / text payloads
 * - Batch uploading to `/api/vault/{vault}/batch-upload`
 * - Managing drop progress modals and confirmation dialogs
 */

import { api } from './auth.js';
import { t } from './i18n.js';
import { showToast } from './ui.js';
import { refreshSidebarTreePreservingState } from './sidebar.js';

/**
 * Recursively read all FileSystemEntry items (files and directories) from DataTransferItemList.
 * Falls back to plain File objects if FileSystem API is unavailable.
 *
 * @param {DataTransferItemList|FileList|File[]} items - DataTransfer items or files
 * @returns {Promise<Array<{ path: string, file?: File, isDir?: boolean }>>}
 */
export async function readDataTransferEntries(items) {
  const results = [];
  if (!items) return results;

  // Check if items support webkitGetAsEntry
  const entries = [];
  if (items.length && typeof items[0].webkitGetAsEntry === 'function') {
    for (let i = 0; i < items.length; i++) {
      const entry = items[i].webkitGetAsEntry();
      if (entry) entries.push(entry);
    }
  }

  if (entries.length > 0) {
    // Traverse entries recursively
    for (const entry of entries) {
      await traverseFileSystemEntry(entry, '', results);
    }
  } else {
    // Plain FileList or files
    for (let i = 0; i < items.length; i++) {
      const file = items[i] instanceof File ? items[i] : items[i].getAsFile ? items[i].getAsFile() : null;
      if (file) {
        const relPath = file.webkitRelativePath || file.name;
        results.push({
          path: relPath.replace(/\\/g, '/'),
          file,
          isDir: false,
        });
      }
    }
  }

  return results;
}

/**
 * Traverse a single FileSystemEntry recursively.
 */
async function traverseFileSystemEntry(entry, parentPath, results) {
  const currentPath = parentPath ? `${parentPath}/${entry.name}` : entry.name;

  if (entry.isFile) {
    const file = await new Promise((resolve, reject) => {
      entry.file(resolve, reject);
    });
    results.push({
      path: currentPath.replace(/\\/g, '/'),
      file,
      isDir: false,
    });
  } else if (entry.isDirectory) {
    results.push({
      path: currentPath.replace(/\\/g, '/'),
      isDir: true,
    });
    const dirReader = entry.createReader();
    const readAllEntries = async () => {
      const childEntries = await new Promise((resolve, reject) => {
        dirReader.readEntries(resolve, reject);
      });
      if (childEntries.length > 0) {
        for (const child of childEntries) {
          await traverseFileSystemEntry(child, currentPath, results);
        }
        await readAllEntries(); // Read next batch (readEntries returns max 100 at a time)
      }
    };
    await readAllEntries();
  }
}

/**
 * Convert a File object to base64 data string.
 * @param {File} file
 * @returns {Promise<string>}
 */
export function fileToBase64(file) {
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.onload = () => {
      const res = reader.result;
      if (typeof res === 'string') {
        resolve(res);
      } else {
        reject(new Error('Failed to read file as base64 string'));
      }
    };
    reader.onerror = (err) => reject(err);
    reader.readAsDataURL(file);
  });
}

/**
 * Upload a batch of extracted items into a vault and target folder.
 *
 * @param {string} vault - Target vault name
 * @param {string} targetDir - Target relative directory (empty for root)
 * @param {Array<{ path: string, file?: File, isDir?: boolean }>} items - Extracted items
 * @param {Object} [options]
 * @param {boolean} [options.overwrite=true]
 * @param {Function} [options.onProgress] - Callback (current, total)
 * @returns {Promise<{ success: boolean, uploaded: string[], created_dirs: string[], errors: any[] }>}
 */
export async function uploadBatch(vault, targetDir, items, options = {}) {
  if (!vault || !items || !items.length) {
    return { success: true, uploaded: [], created_dirs: [], errors: [], total_files: 0 };
  }

  const { overwrite = true, onProgress = null } = options;
  const payloadFiles = [];
  const total = items.length;

  for (let i = 0; i < total; i++) {
    const item = items[i];
    if (onProgress) onProgress(i, total, item.path);

    if (item.isDir) {
      payloadFiles.push({
        path: item.path,
        is_dir: true,
      });
    } else if (item.file) {
      try {
        const b64 = await fileToBase64(item.file);
        payloadFiles.push({
          path: item.path,
          content: b64,
          is_dir: false,
        });
      } catch (err) {
        console.warn(`Failed to encode file ${item.path}:`, err);
      }
    }
  }

  if (onProgress) onProgress(total, total, 'Sending payload...');

  const response = await api(`/api/vault/${encodeURIComponent(vault)}/batch-upload`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      target_dir: targetDir || '',
      files: payloadFiles,
      overwrite,
    }),
  });

  return response;
}

/**
 * Show a simple upload modal / toast and execute the upload.
 *
 * @param {string} vault
 * @param {string} targetDir
 * @param {Array<{ path: string, file?: File, isDir?: boolean }>} items
 */
export async function handleVaultDropUpload(vault, targetDir, items) {
  if (!items || !items.length) return;

  const fileCount = items.filter((x) => !x.isDir).length;
  const dirCount = items.filter((x) => x.isDir).length;
  const destName = targetDir ? `${vault}/${targetDir}` : vault;

  showToast(`${t('upload.uploading', { count: fileCount }) || `Uploading ${fileCount} file(s) to ${destName}...`}`, 'info');

  try {
    const res = await uploadBatch(vault, targetDir, items);
    if (res && res.success) {
      showToast(t('upload.success', { count: res.uploaded.length }) || `Imported ${res.uploaded.length} file(s) successfully`, 'success');
    } else if (res && res.uploaded && res.uploaded.length > 0) {
      showToast(t('upload.partial', { count: res.uploaded.length, errors: res.errors.length }) || `Imported ${res.uploaded.length} file(s) (${res.errors.length} errors)`, 'warning');
    } else {
      const errDetail = res?.errors?.[0]?.error || 'Unknown error';
      showToast(`${t('upload.error') || 'Upload failed'}: ${errDetail}`, 'error');
    }
    await refreshSidebarTreePreservingState();
  } catch (err) {
    console.error('Batch upload error:', err);
    showToast(`${t('upload.error') || 'Upload failed'}: ${err.message || err}`, 'error');
  }
}