/**
 * FolderService - Gestión de carpetas de almacenamiento
 *
 * Servicio para CRUD de carpetas, estructura jerárquica y operaciones de movimiento.
 *
 * @module Storage
 */

import { Repository, IsNull, Not, In } from 'typeorm';
import { StorageFolder } from '../entities/folder.entity';
import { StorageBucket } from '../entities/bucket.entity';
import { StorageFile } from '../entities/file.entity';

export interface CreateFolderDto {
  bucketId: string;
  parentId?: string;
  name: string;
  description?: string;
  color?: string;
  icon?: string;
  isPrivate?: boolean;
}

export interface UpdateFolderDto {
  name?: string;
  description?: string;
  color?: string;
  icon?: string;
  isPrivate?: boolean;
}

export interface FolderFilters {
  bucketId?: string;
  parentId?: string | null;
  isPrivate?: boolean;
  ownerId?: string;
  search?: string;
  page?: number;
  limit?: number;
}

export interface FolderTreeNode {
  id: string;
  name: string;
  path: string;
  depth: number;
  fileCount: number;
  totalSizeBytes: number;
  children: FolderTreeNode[];
}

export interface PaginatedResult<T> {
  data: T[];
  total: number;
  page: number;
  limit: number;
  totalPages: number;
}

export class FolderService {
  constructor(
    private readonly folderRepository: Repository<StorageFolder>,
    private readonly bucketRepository: Repository<StorageBucket>,
    private readonly fileRepository: Repository<StorageFile>,
  ) {}

  /**
   * Create a new folder
   */
  async create(
    tenantId: string,
    dto: CreateFolderDto,
    userId?: string,
  ): Promise<StorageFolder> {
    // Validate bucket exists
    const bucket = await this.bucketRepository.findOne({
      where: { id: dto.bucketId, isActive: true },
    });
    if (!bucket) {
      throw new Error('Bucket no encontrado o inactivo');
    }

    // Calculate path and depth
    let parentPath = '';
    let depth = 0;

    if (dto.parentId) {
      const parent = await this.folderRepository.findOne({
        where: { id: dto.parentId, tenantId, bucketId: dto.bucketId },
      });
      if (!parent) {
        throw new Error('Carpeta padre no encontrada');
      }
      parentPath = parent.path;
      depth = parent.depth + 1;
    }

    const folderPath = parentPath ? `${parentPath}/${dto.name}` : dto.name;

    // Check if folder with same path already exists
    const existing = await this.folderRepository.findOne({
      where: { tenantId, bucketId: dto.bucketId, path: folderPath },
    });
    if (existing) {
      throw new Error('Ya existe una carpeta con ese nombre en esta ubicación');
    }

    const folder = this.folderRepository.create({
      tenantId,
      bucketId: dto.bucketId,
      parentId: dto.parentId,
      name: dto.name,
      path: folderPath,
      depth,
      description: dto.description,
      color: dto.color,
      icon: dto.icon,
      isPrivate: dto.isPrivate || false,
      ownerId: dto.isPrivate ? userId : undefined,
      createdBy: userId,
    });

    return this.folderRepository.save(folder);
  }

  /**
   * Find folder by ID
   */
  async findById(tenantId: string, id: string): Promise<StorageFolder | null> {
    return this.folderRepository.findOne({
      where: { id, tenantId },
      relations: ['bucket', 'parent'],
    });
  }

  /**
   * Find folder by path
   */
  async findByPath(
    tenantId: string,
    bucketId: string,
    path: string,
  ): Promise<StorageFolder | null> {
    return this.folderRepository.findOne({
      where: { tenantId, bucketId, path },
      relations: ['bucket', 'parent'],
    });
  }

  /**
   * Find all folders with filters
   */
  async findAll(
    tenantId: string,
    filters: FolderFilters = {},
  ): Promise<PaginatedResult<StorageFolder>> {
    const page = filters.page || 1;
    const limit = Math.min(filters.limit || 50, 200);
    const skip = (page - 1) * limit;

    const qb = this.folderRepository
      .createQueryBuilder('f')
      .leftJoinAndSelect('f.bucket', 'bucket')
      .leftJoinAndSelect('f.parent', 'parent')
      .where('f.tenant_id = :tenantId', { tenantId });

    if (filters.bucketId) {
      qb.andWhere('f.bucket_id = :bucketId', { bucketId: filters.bucketId });
    }

    if (filters.parentId === null) {
      qb.andWhere('f.parent_id IS NULL');
    } else if (filters.parentId) {
      qb.andWhere('f.parent_id = :parentId', { parentId: filters.parentId });
    }

    if (filters.isPrivate !== undefined) {
      qb.andWhere('f.is_private = :isPrivate', { isPrivate: filters.isPrivate });
    }

    if (filters.ownerId) {
      qb.andWhere('f.owner_id = :ownerId', { ownerId: filters.ownerId });
    }

    if (filters.search) {
      qb.andWhere('(f.name ILIKE :search OR f.description ILIKE :search)', {
        search: `%${filters.search}%`,
      });
    }

    qb.orderBy('f.name', 'ASC').skip(skip).take(limit);

    const [data, total] = await qb.getManyAndCount();

    return {
      data,
      total,
      page,
      limit,
      totalPages: Math.ceil(total / limit),
    };
  }

  /**
   * Get root folders (no parent) for a bucket
   */
  async getRootFolders(
    tenantId: string,
    bucketId: string,
  ): Promise<StorageFolder[]> {
    return this.folderRepository.find({
      where: { tenantId, bucketId, parentId: IsNull() },
      order: { name: 'ASC' },
    });
  }

  /**
   * Get children of a folder
   */
  async getChildren(
    tenantId: string,
    folderId: string,
  ): Promise<StorageFolder[]> {
    return this.folderRepository.find({
      where: { tenantId, parentId: folderId },
      order: { name: 'ASC' },
    });
  }

  /**
   * Get full folder tree for a bucket
   */
  async getTree(
    tenantId: string,
    bucketId: string,
    rootFolderId?: string,
  ): Promise<FolderTreeNode[]> {
    // Get all folders in the bucket
    const allFolders = await this.folderRepository.find({
      where: { tenantId, bucketId },
      order: { path: 'ASC' },
    });

    // Build tree structure
    const folderMap = new Map<string, FolderTreeNode>();
    const rootNodes: FolderTreeNode[] = [];

    // First pass: create all nodes
    for (const folder of allFolders) {
      folderMap.set(folder.id, {
        id: folder.id,
        name: folder.name,
        path: folder.path,
        depth: folder.depth,
        fileCount: folder.fileCount,
        totalSizeBytes: Number(folder.totalSizeBytes),
        children: [],
      });
    }

    // Second pass: build hierarchy
    for (const folder of allFolders) {
      const node = folderMap.get(folder.id);
      if (!node) continue;

      if (rootFolderId) {
        // If we have a root folder ID, start from there
        if (folder.id === rootFolderId) {
          rootNodes.push(node);
        } else if (folder.parentId) {
          const parentNode = folderMap.get(folder.parentId);
          if (parentNode) {
            parentNode.children.push(node);
          }
        }
      } else {
        // No root folder, start from top-level folders
        if (!folder.parentId) {
          rootNodes.push(node);
        } else {
          const parentNode = folderMap.get(folder.parentId);
          if (parentNode) {
            parentNode.children.push(node);
          }
        }
      }
    }

    return rootNodes;
  }

  /**
   * Get folder breadcrumb (path from root to folder)
   */
  async getBreadcrumb(
    tenantId: string,
    folderId: string,
  ): Promise<{ id: string; name: string; path: string }[]> {
    const folder = await this.findById(tenantId, folderId);
    if (!folder) {
      return [];
    }

    const breadcrumb: { id: string; name: string; path: string }[] = [];
    let currentFolder: StorageFolder | null = folder;

    while (currentFolder) {
      breadcrumb.unshift({
        id: currentFolder.id,
        name: currentFolder.name,
        path: currentFolder.path,
      });

      if (currentFolder.parentId) {
        currentFolder = await this.folderRepository.findOne({
          where: { id: currentFolder.parentId, tenantId },
        });
      } else {
        currentFolder = null;
      }
    }

    return breadcrumb;
  }

  /**
   * Update folder
   */
  async update(
    tenantId: string,
    id: string,
    dto: UpdateFolderDto,
  ): Promise<StorageFolder | null> {
    const folder = await this.findById(tenantId, id);
    if (!folder) {
      return null;
    }

    // If renaming, update path and all descendant paths
    if (dto.name && dto.name !== folder.name) {
      const oldPath = folder.path;
      const newPath = folder.parentId
        ? `${folder.path.substring(0, folder.path.lastIndexOf('/'))}/${dto.name}`
        : dto.name;

      // Update all descendant paths
      await this.updateDescendantPaths(tenantId, oldPath, newPath);

      folder.path = newPath;
    }

    Object.assign(folder, dto);
    return this.folderRepository.save(folder);
  }

  /**
   * Move folder to a new parent
   */
  async move(
    tenantId: string,
    folderId: string,
    newParentId: string | null,
  ): Promise<StorageFolder | null> {
    const folder = await this.findById(tenantId, folderId);
    if (!folder) {
      return null;
    }

    // Prevent moving to self
    if (newParentId === folderId) {
      throw new Error('No se puede mover una carpeta a sí misma');
    }

    // Validate new parent if provided
    let newParent: StorageFolder | null = null;
    if (newParentId) {
      newParent = await this.folderRepository.findOne({
        where: { id: newParentId, tenantId, bucketId: folder.bucketId },
      });
      if (!newParent) {
        throw new Error('Carpeta destino no encontrada');
      }

      // Prevent moving to a descendant
      if (newParent.path.startsWith(folder.path + '/')) {
        throw new Error('No se puede mover una carpeta a una de sus subcarpetas');
      }
    }

    const oldPath = folder.path;
    const newPath = newParent
      ? `${newParent.path}/${folder.name}`
      : folder.name;
    const newDepth = newParent ? newParent.depth + 1 : 0;

    // Check if folder with same name already exists in new location
    const existing = await this.folderRepository.findOne({
      where: {
        tenantId,
        bucketId: folder.bucketId,
        path: newPath,
        id: Not(folderId),
      },
    });
    if (existing) {
      throw new Error('Ya existe una carpeta con ese nombre en el destino');
    }

    // Update all descendant paths
    await this.updateDescendantPaths(tenantId, oldPath, newPath);

    // Update folder
    folder.parentId = newParentId;
    folder.path = newPath;
    folder.depth = newDepth;

    return this.folderRepository.save(folder);
  }

  /**
   * Delete folder and optionally its contents
   */
  async delete(
    tenantId: string,
    id: string,
    deleteContents: boolean = false,
  ): Promise<boolean> {
    const folder = await this.findById(tenantId, id);
    if (!folder) {
      return false;
    }

    // Check if folder has contents
    const hasFiles = await this.fileRepository.count({
      where: { tenantId, folderId: id, status: 'active' },
    });
    const hasSubfolders = await this.folderRepository.count({
      where: { tenantId, parentId: id },
    });

    if ((hasFiles > 0 || hasSubfolders > 0) && !deleteContents) {
      throw new Error(
        'La carpeta no está vacía. Use deleteContents=true para eliminar con contenido.',
      );
    }

    if (deleteContents) {
      // Soft delete all files in folder and subfolders
      const descendantFolderIds = await this.getDescendantIds(tenantId, id);
      const allFolderIds = [id, ...descendantFolderIds];

      await this.fileRepository.update(
        { tenantId, folderId: In(allFolderIds), status: 'active' },
        { status: 'deleted', deletedAt: new Date() },
      );

      // Delete subfolders
      for (const folderId of descendantFolderIds.reverse()) {
        await this.folderRepository.delete({ id: folderId, tenantId });
      }
    }

    // Delete the folder
    await this.folderRepository.delete({ id, tenantId });

    return true;
  }

  /**
   * Get folder statistics
   */
  async getStats(
    tenantId: string,
    folderId: string,
  ): Promise<{
    fileCount: number;
    subfolderCount: number;
    totalSizeBytes: number;
    filesByCategory: Record<string, number>;
  }> {
    const folder = await this.findById(tenantId, folderId);
    if (!folder) {
      throw new Error('Carpeta no encontrada');
    }

    // Get all descendant folder IDs including current
    const descendantIds = await this.getDescendantIds(tenantId, folderId);
    const allFolderIds = [folderId, ...descendantIds];

    const [fileStats, categoryStats] = await Promise.all([
      this.fileRepository
        .createQueryBuilder('f')
        .select('COUNT(*)', 'count')
        .addSelect('COALESCE(SUM(f.size_bytes), 0)', 'totalSize')
        .where('f.tenant_id = :tenantId', { tenantId })
        .andWhere('f.folder_id IN (:...folderIds)', { folderIds: allFolderIds })
        .andWhere('f.status = :status', { status: 'active' })
        .getRawOne(),
      this.fileRepository
        .createQueryBuilder('f')
        .select('f.category', 'category')
        .addSelect('COUNT(*)', 'count')
        .where('f.tenant_id = :tenantId', { tenantId })
        .andWhere('f.folder_id IN (:...folderIds)', { folderIds: allFolderIds })
        .andWhere('f.status = :status', { status: 'active' })
        .groupBy('f.category')
        .getRawMany(),
    ]);

    const filesByCategory: Record<string, number> = {};
    for (const row of categoryStats) {
      filesByCategory[row.category || 'other'] = parseInt(row.count, 10);
    }

    return {
      fileCount: parseInt(fileStats.count, 10),
      subfolderCount: descendantIds.length,
      totalSizeBytes: parseInt(fileStats.totalSize, 10),
      filesByCategory,
    };
  }

  // ============ Private Helper Methods ============

  private async updateDescendantPaths(
    tenantId: string,
    oldPath: string,
    newPath: string,
  ): Promise<void> {
    // Update all folders that start with the old path
    await this.folderRepository
      .createQueryBuilder()
      .update(StorageFolder)
      .set({
        path: () => `REPLACE(path, '${oldPath}', '${newPath}')`,
        depth: () =>
          `depth + ${newPath.split('/').length - oldPath.split('/').length}`,
      })
      .where('tenant_id = :tenantId', { tenantId })
      .andWhere('path LIKE :pathPattern', { pathPattern: `${oldPath}/%` })
      .execute();
  }

  private async getDescendantIds(
    tenantId: string,
    folderId: string,
  ): Promise<string[]> {
    const folder = await this.findById(tenantId, folderId);
    if (!folder) {
      return [];
    }

    const descendants = await this.folderRepository.find({
      where: { tenantId, bucketId: folder.bucketId },
      select: ['id', 'path'],
    });

    return descendants
      .filter((d) => d.path.startsWith(folder.path + '/'))
      .map((d) => d.id);
  }
}