import type { File, CreateFileData, Result } from './types';
import type { FileDatabase } from './db';
import { compressFiles, decompressFiles, filesToShareUrl, filesFromShareUrl } from './compression';
import { loadSystemFiles, isSystemFileId, getSystemFile } from './system-files';

async function wrapResult<T>(fn: () => Promise<T>, errorMsg: string): Promise<Result<T>> {
  try {
    const data = await fn();
    return { success: true, data };
  } catch (error) {
    return {
      success: false,
      error: error instanceof Error ? error : new Error(errorMsg),
    };
  }
}

/**
 * Generate a unique ID
 */
function generateId(): string {
  return `${Date.now()}-${Math.random().toString(36).substr(2, 9)}`;
}

type FileChangeListener = () => void;

/**
 * File Manager - Main API for managing files
 */
export class FileManager {
  private db: FileDatabase;
  private changeListeners: Set<FileChangeListener> = new Set();

  constructor(db: FileDatabase) {
    this.db = db;
  }

  /**
   * Subscribe to file changes
   */
  onFilesChanged(listener: FileChangeListener): () => void {
    this.changeListeners.add(listener);
    return () => this.changeListeners.delete(listener);
  }

  /**
   * Notify all listeners that files have changed
   */
  private notifyChange(): void {
    this.changeListeners.forEach(listener => listener());
  }

  /**
   * Initialize the file manager (initializes database)
   */
  async init(): Promise<void> {
    await this.db.init();
  }

  /**
   * Create a new file
   */
  async createFile(data: CreateFileData): Promise<Result<File>> {
    try {
      const file: File = {
        id: generateId(),
        title: data.title,
        content: data.content || '',
      };

      await this.db.put(file);
      this.notifyChange();

      return { success: true, data: file };
    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error : new Error('Failed to create file'),
      };
    }
  }

  /**
   * Get a file by ID (checks both user and system files)
   */
  async getFile(id: string): Promise<Result<File>> {
    try {
      if (isSystemFileId(id)) {
        const systemFile = getSystemFile(id);
        if (systemFile) {
          return { success: true, data: systemFile };
        }
      }

      const file = await this.db.get(id);

      if (!file) {
        return {
          success: false,
          error: new Error(`File not found: ${id}`),
        };
      }

      return { success: true, data: file };
    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error : new Error('Failed to get file'),
      };
    }
  }

  /**
   * Get all files (user files + system files)
   */
  async getAllFiles(): Promise<Result<File[]>> {
    try {
      const userFiles = await this.db.getAll();
      const systemFiles = await loadSystemFiles();

      return {
        success: true,
        data: [...systemFiles, ...userFiles],
      };
    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error : new Error('Failed to get files'),
      };
    }
  }

  /**
   * Update a file (system files cannot be updated directly)
   */
  async updateFile(id: string, updates: Partial<Pick<File, 'title' | 'content'>>): Promise<Result<File>> {
    try {
      if (isSystemFileId(id)) {
        return {
          success: false,
          error: new Error('Cannot update system files directly. Use "Save As" to create a copy.'),
        };
      }

      const existingFile = await this.db.get(id);

      if (!existingFile) {
        return {
          success: false,
          error: new Error(`File not found: ${id}`),
        };
      }

      const updatedFile: File = {
        ...existingFile,
        ...(updates.title !== undefined && { title: updates.title }),
        ...(updates.content !== undefined && { content: updates.content }),
      };

      await this.db.put(updatedFile);
      this.notifyChange();

      return { success: true, data: updatedFile };
    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error : new Error('Failed to update file'),
      };
    }
  }

  /**
   * Delete a file (system files cannot be deleted)
   */
  async deleteFile(id: string): Promise<Result<void>> {
    if (isSystemFileId(id)) {
      return {
        success: false,
        error: new Error('Cannot delete system files'),
      };
    }

    const result = await wrapResult(() => this.db.delete(id), 'Failed to delete file');
    if (result.success) {
      this.notifyChange();
    }
    return result;
  }

  /**
   * Duplicate a file (works with both user and system files)
   */
  async duplicateFile(id: string): Promise<Result<File>> {
    try {
      const result = await this.getFile(id);

      if (!result.success) {
        return result;
      }

      const originalFile = result.data;
      const duplicatedFile: File = {
        id: generateId(),
        title: `${originalFile.title} (copy)`,
        content: originalFile.content,
      };

      await this.db.put(duplicatedFile);
      this.notifyChange();

      return { success: true, data: duplicatedFile };
    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error : new Error('Failed to duplicate file'),
      };
    }
  }

  /**
   * Generate unique untitled filename
   */
  async generateUntitledFilename(): Promise<string> {
    const result = await this.getAllFiles();
    if (!result.success) {
      return 'Untitled-1.orc';
    }

    const files = result.data;
    const untitledPattern = /^Untitled-(\d+)\.orc$/;
    let maxNum = 0;

    files.forEach(file => {
      const match = file.title.match(untitledPattern);
      if (match) {
        const num = parseInt(match[1], 10);
        if (num > maxNum) {
          maxNum = num;
        }
      }
    });

    return `Untitled-${maxNum + 1}.orc`;
  }

  /**
   * Export files to a shareable URL
   */
  async exportFilesToUrl(fileIds: string[], baseUrl?: string): Promise<Result<string>> {
    try {
      const files: File[] = [];

      for (const id of fileIds) {
        const file = await this.db.get(id);
        if (file) {
          files.push(file);
        }
      }

      if (files.length === 0) {
        return {
          success: false,
          error: new Error('No files to export'),
        };
      }

      const url = filesToShareUrl(files, baseUrl);

      return { success: true, data: url };
    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error : new Error('Failed to export files'),
      };
    }
  }

  /**
   * Import files from a URL
   */
  async importFilesFromUrl(url: string): Promise<Result<File[]>> {
    try {
      const files = filesFromShareUrl(url);

      // Generate new IDs for imported files
      const importedFiles = files.map(file => ({
        ...file,
        id: generateId(),
      }));

      for (const file of importedFiles) {
        await this.db.put(file);
      }

      this.notifyChange();

      return { success: true, data: importedFiles };
    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error : new Error('Failed to import files'),
      };
    }
  }

  /**
   * Clear all files (use with caution!)
   */
  async clearAllFiles(): Promise<Result<void>> {
    const result = await wrapResult(() => this.db.clear(), 'Failed to clear files');
    if (result.success) {
      this.notifyChange();
    }
    return result;
  }
}