/**
 * SimpleNote Web - Document Service
 * Document CRUD with markdown storage
 * Supports both legacy libraries/ and new projects/ structure
 */

import { join } from 'path';
import { existsSync, readFileSync, writeFileSync } from 'fs';
import config from '../config/index.js';
import { ensureDir, readJSON, writeJSON, pathExists, deletePath, listDir, isDirectory } from '../utils/fsHelper.js';
import { generateId } from '../utils/uuid.js';
import { parseMarkdown, serializeMarkdown, buildDefaultContent } from '../utils/markdown.js';
import { NotFoundError, ValidationError } from '../utils/errors.js';
import { getTagIndexer } from '../indexers/tagIndexer.js';
import { getLibraryService } from './libraryService.js';
import { getProjectService } from './projectService.js';
import { getFolderService } from './folderService.js';

const LIBRARIES_DIR = 'libraries';
const PROJECTS_DIR = 'projects';
const FOLDERS_DIR = 'folders';

export class DocumentService {
  constructor(dataRoot = config.dataRoot) {
    this.dataRoot = dataRoot;
    this.librariesPath = join(dataRoot, LIBRARIES_DIR);
    this.projectsPath = join(dataRoot, PROJECTS_DIR);
    this.tagIndexer = getTagIndexer(dataRoot);
  }

  // ===== Legacy Libraries Paths =====

  _docPath(libId, docId) {
    return join(this.librariesPath, libId, 'documents', docId);
  }

  _docIndexPath(libId, docId) {
    return join(this._docPath(libId, docId), 'index.md');
  }

  _docMetaPath(libId, docId) {
    return join(this._docPath(libId, docId), '.meta.json');
  }

  // ===== New Projects/Folders Paths =====

  _projectDocPath(projectId, docId) {
    return join(this.projectsPath, projectId, 'documents', docId);
  }

  _projectDocIndexPath(projectId, docId) {
    return join(this._projectDocPath(projectId, docId), 'index.md');
  }

  _projectDocMetaPath(projectId, docId) {
    return join(this._projectDocPath(projectId, docId), '.meta.json');
  }

  _folderDocPath(projectId, folderId, docId) {
    return join(this.projectsPath, projectId, FOLDERS_DIR, folderId, 'documents', docId);
  }

  _folderDocIndexPath(projectId, folderId, docId) {
    return join(this._folderDocPath(projectId, folderId, docId), 'index.md');
  }

  _folderDocMetaPath(projectId, folderId, docId) {
    return join(this._folderDocPath(projectId, folderId, docId), '.meta.json');
  }

  // ===== Find Methods =====

  _findDocInLibrary(libId, docId) {
    const metaPath = this._docMetaPath(libId, docId);
    if (pathExists(metaPath)) {
      return { docId, libId, metaPath, indexPath: this._docIndexPath(libId, docId), storageType: 'library' };
    }
    return null;
  }

  _findDocInProject(projectId, docId) {
    const metaPath = this._projectDocMetaPath(projectId, docId);
    if (pathExists(metaPath)) {
      return { docId, projectId, metaPath, indexPath: this._projectDocIndexPath(projectId, docId), storageType: 'project' };
    }
    return null;
  }

  _findDocInFolder(projectId, folderId, docId) {
    const metaPath = this._folderDocMetaPath(projectId, folderId, docId);
    if (pathExists(metaPath)) {
      return { docId, projectId, folderId, metaPath, indexPath: this._folderDocIndexPath(projectId, folderId, docId), storageType: 'folder' };
    }
    return null;
  }

  _findInSubLibs(subLibsPath, docId, libEntry) {
    if (!pathExists(subLibsPath)) return null;

    const entries = listDir(subLibsPath);
    for (const entry of entries) {
      const entryPath = join(subLibsPath, entry);
      if (!isDirectory(entryPath)) continue;

      // Check if doc is here
      const metaPath = join(entryPath, 'documents', docId, '.meta.json');
      if (pathExists(metaPath)) {
        return { docId, libId: entry, metaPath, indexPath: join(entryPath, 'documents', docId, 'index.md'), storageType: 'library' };
      }

      // Recurse into sub-sub-libraries
      const subSubLibsPath = join(entryPath, 'sub-libraries');
      const found = this._findInSubLibs(subSubLibsPath, docId, entry);
      if (found) return found;
    }
    return null;
  }

  _findDocById(docId) {
    // First check new projects structure
    if (pathExists(this.projectsPath)) {
      const projectEntries = listDir(this.projectsPath);
      for (const projectEntry of projectEntries) {
        const projectPath = join(this.projectsPath, projectEntry);
        if (!isDirectory(projectPath)) continue;

        // Direct doc in project root
        const found = this._findDocInProject(projectEntry, docId);
        if (found) return found;

        // Doc in folders (search recursively)
        const foldersPath = join(projectPath, FOLDERS_DIR);
        if (pathExists(foldersPath)) {
          const foundInFolder = this._findDocInProjectFolders(foldersPath, projectEntry, docId);
          if (foundInFolder) return foundInFolder;
        }
      }
    }

    // Fallback: search legacy libraries structure
    if (!pathExists(this.librariesPath)) return null;

    const libEntries = listDir(this.librariesPath);
    for (const libEntry of libEntries) {
      const libPath = join(this.librariesPath, libEntry);
      if (!isDirectory(libPath)) continue;

      // Direct doc
      const found = this._findDocInLibrary(libEntry, docId);
      if (found) return found;

      // Sub-libraries (recursive)
      const subLibsPath = join(libPath, 'sub-libraries');
      if (pathExists(subLibsPath)) {
        const foundSub = this._findInSubLibs(subLibsPath, docId, libEntry);
        if (foundSub) return foundSub;
      }
    }
    return null;
  }

  _findDocInProjectFolders(foldersPath, projectId, docId) {
    if (!pathExists(foldersPath)) return null;

    const folderEntries = listDir(foldersPath);
    for (const folderEntry of folderEntries) {
      const folderPath = join(foldersPath, folderEntry);
      if (!isDirectory(folderPath)) continue;

      // Check if doc is directly in this folder
      const found = this._findDocInFolder(projectId, folderEntry, docId);
      if (found) return found;

      // Recurse into sub-folders
      const subFoldersPath = join(folderPath, 'sub-folders');
      const foundSub = this._findDocInProjectFolders(subFoldersPath, projectId, docId);
      if (foundSub) return foundSub;
    }
    return null;
  }

  _readDocRaw(docId) {
    const found = this._findDocById(docId);
    if (!found) return null;

    const meta = readJSON(found.metaPath);
    let content = '';
    if (pathExists(found.indexPath)) {
      content = readFileSync(found.indexPath, 'utf-8');
    }

    return { meta, content, found };
  }

  // ===== CRUD Operations =====

  /**
   * Create a document.
   * Supports both legacy libraryId (backwards compat) and new projectId/folderId.
   * @param {Object} params
   * @param {string} params.title - Document title
   * @param {string} [params.libraryId] - Legacy library ID (backwards compat)
   * @param {string} [params.projectId] - Project ID (new structure)
   * @param {string} [params.folderId] - Folder ID within project (new structure)
   * @param {string} [params.content] - Document content
   * @param {string[]} [params.tags] - Tags
   * @param {string} [params.type] - Document type
   * @param {string} [params.priority] - Priority
   * @param {string} [params.status] - Status
   * @param {string} [params.createdBy] - Creator
   */
  async createDocument({ title, libraryId, projectId, folderId, content, tags = [], type = 'general', priority = 'medium', status = 'draft', createdBy = null }) {
    if (!title || !title.trim()) {
      throw new ValidationError('Title is required');
    }

    // Determine storage location: prefer new project/folder structure, fallback to legacy library
    let effectiveProjectId = projectId;
    let effectiveFolderId = folderId || null;
    let effectiveLibraryId = libraryId;

    if (effectiveProjectId) {
      // New structure: verify project exists
      const projectService = getProjectService(this.dataRoot);
      await projectService.getProject(effectiveProjectId);

      // If folderId provided, verify folder exists
      if (effectiveFolderId) {
        const folderService = getFolderService(this.dataRoot);
        await folderService.getFolder(effectiveFolderId);
      }

      // Backwards compat: set libraryId = projectId for legacy code
      effectiveLibraryId = effectiveProjectId;
    } else if (effectiveLibraryId) {
      // Legacy structure: verify library exists
      const libService = getLibraryService(this.dataRoot);
      await libService.getLibrary(effectiveLibraryId);

      // Backwards compat: for old docs, projectId = libraryId
      effectiveProjectId = effectiveLibraryId;
    } else {
      throw new ValidationError('Either libraryId or projectId is required');
    }

    const docId = generateId();
    const now = new Date().toISOString();

    let docPath, metaPath, indexPath;

    if (effectiveFolderId) {
      // Store in folder
      docPath = this._folderDocPath(effectiveProjectId, effectiveFolderId, docId);
      metaPath = this._folderDocMetaPath(effectiveProjectId, effectiveFolderId, docId);
      indexPath = this._folderDocIndexPath(effectiveProjectId, effectiveFolderId, docId);
      ensureDir(docPath);
    } else if (effectiveProjectId) {
      // Store in project root
      docPath = this._projectDocPath(effectiveProjectId, docId);
      metaPath = this._projectDocMetaPath(effectiveProjectId, docId);
      indexPath = this._projectDocIndexPath(effectiveProjectId, docId);
      ensureDir(docPath);
    } else {
      // Legacy: store in library
      docPath = this._docPath(effectiveLibraryId, docId);
      metaPath = this._docMetaPath(effectiveLibraryId, docId);
      indexPath = this._docIndexPath(effectiveLibraryId, docId);
      ensureDir(docPath);
    }

    const metadata = {
      id: docId,
      title: title.trim(),
      tags: tags.filter(t => t),
      type,
      priority,
      status,
      // New fields
      projectId: effectiveProjectId,
      folderId: effectiveFolderId,
      // Legacy field (backwards compat - same as projectId)
      libraryId: effectiveLibraryId,
      createdBy,
      createdAt: now,
      updatedAt: now,
    };

    const body = content || buildDefaultContent(title, type);
    const markdown = serializeMarkdown(metadata, body);

    writeJSON(metaPath, metadata);
    writeFileSync(indexPath, markdown, 'utf-8');

    // Update tag index
    this.tagIndexer.addDocument(docId, metadata.tags);

    return {
      ...metadata,
      path: this._getDocPathForResponse(metadata),
      content: body,
    };
  }

  _getDocPathForResponse(metadata) {
    if (metadata.folderId) {
      return `/${PROJECTS_DIR}/${metadata.projectId}/${FOLDERS_DIR}/${metadata.folderId}/documents/${metadata.id}/index.md`;
    } else if (metadata.projectId) {
      return `/${PROJECTS_DIR}/${metadata.projectId}/documents/${metadata.id}/index.md`;
    } else {
      return `/${LIBRARIES_DIR}/${metadata.libraryId}/documents/${metadata.id}/index.md`;
    }
  }

  async listDocuments({ tag, library, project, folder, type, status, limit = 50, offset = 0 } = {}) {
    let allDocs = [];

    // Collect from projects structure (new)
    if (pathExists(this.projectsPath)) {
      await this._collectDocsFromProjects(allDocs);
    }

    // Collect from legacy libraries structure
    if (pathExists(this.librariesPath)) {
      await this._collectDocs(this.librariesPath, allDocs);
    }

    // Filter by project
    if (project) {
      allDocs = allDocs.filter(d => d.projectId === project);
    }

    // Filter by folder
    if (folder) {
      allDocs = allDocs.filter(d => d.folderId === folder);
    }

    // Filter by library (backwards compat)
    if (library) {
      allDocs = allDocs.filter(d => d.libraryId === library || d.projectId === library);
    }

    // Filter by tag
    if (tag) {
      const docIds = this.tagIndexer.getDocIdsForTag(tag);
      allDocs = allDocs.filter(d => docIds.includes(d.id));
    }

    // Filter by type
    if (type) {
      allDocs = allDocs.filter(d => d.type === type);
    }

    // Filter by status
    if (status) {
      allDocs = allDocs.filter(d => d.status === status);
    }

    const total = allDocs.length;
    const paginated = allDocs.slice(offset, offset + limit);

    // Enrich with content for each doc
    const enriched = paginated.map(doc => {
      const { meta } = this._readDocRaw(doc.id) || { meta: doc };
      return { ...doc, content: meta.content || '' };
    });

    return { documents: enriched, total, limit, offset };
  }

  async _collectDocsFromProjects(results) {
    if (!pathExists(this.projectsPath)) return;

    const projectEntries = listDir(this.projectsPath);
    for (const projectEntry of projectEntries) {
      const projectPath = join(this.projectsPath, projectEntry);
      if (!isDirectory(projectPath)) continue;

      // Collect from project root documents
      const docsPath = join(projectPath, 'documents');
      await this._collectDocsAtPath(docsPath, results);

      // Collect from folders recursively
      const foldersPath = join(projectPath, FOLDERS_DIR);
      if (pathExists(foldersPath)) {
        await this._collectDocsFromFolders(foldersPath, projectEntry, results);
      }
    }
  }

  async _collectDocsFromFolders(foldersPath, projectId, results) {
    if (!pathExists(foldersPath)) return;

    const folderEntries = listDir(foldersPath);
    for (const folderEntry of folderEntries) {
      const folderPath = join(foldersPath, folderEntry);
      if (!isDirectory(folderPath)) continue;

      // Collect documents in this folder
      const docsPath = join(folderPath, 'documents');
      await this._collectDocsAtPath(docsPath, results);

      // Recurse into sub-folders
      const subFoldersPath = join(folderPath, 'sub-folders');
      await this._collectDocsFromFolders(subFoldersPath, projectId, results);
    }
  }

  async _collectDocsAtPath(docsPath, results) {
    if (!pathExists(docsPath)) return;

    const docEntries = listDir(docsPath);
    for (const docEntry of docEntries) {
      const docMetaPath = join(docsPath, docEntry, '.meta.json');
      if (pathExists(docMetaPath)) {
        const meta = readJSON(docMetaPath);
        if (meta?.id) {
          results.push(meta);
        }
      }
    }
  }

  async _collectDocs(path, results) {
    if (!pathExists(path)) return;

    const entries = listDir(path);
    for (const entry of entries) {
      const entryPath = join(path, entry);
      const metaPath = join(entryPath, '.meta.json');

      if (pathExists(metaPath)) {
        const meta = readJSON(metaPath);
        if (meta?.id) {
          // Ensure backwards compat fields
          if (!meta.projectId && meta.libraryId) {
            meta.projectId = meta.libraryId;
          }
          results.push(meta);
        }
      } else if (isDirectory(entryPath)) {
        // Could be a library or documents dir
        const docsDir = join(entryPath, 'documents');
        const subLibsDir = join(entryPath, 'sub-libraries');
        if (pathExists(docsDir)) {
          await this._collectDocs(docsDir, results);
        }
        if (pathExists(subLibsDir)) {
          await this._collectDocs(subLibsDir, results);
        }
      }
    }
  }

  async getDocument(docId) {
    const found = this._findDocById(docId);
    if (!found) {
      throw new NotFoundError('Document');
    }

    const meta = readJSON(found.metaPath);
    const indexPath = found.indexPath;
    const content = pathExists(indexPath) ? readFileSync(indexPath, 'utf-8') : '';
    const { body } = parseMarkdown(content);

    return {
      ...meta,
      content: body,
      path: this._getDocPathForResponse(meta),
    };
  }

  async updateDocument(docId, { title, content, tags, type, priority, status, folderId }) {
    const found = this._findDocById(docId);
    if (!found) {
      throw new NotFoundError('Document');
    }

    const meta = readJSON(found.metaPath);
    const oldTags = [...(meta.tags || [])];
    const now = new Date().toISOString();

    if (title !== undefined) meta.title = title.trim();
    if (type !== undefined) meta.type = type;
    if (priority !== undefined) meta.priority = priority;
    if (status !== undefined) meta.status = status;
    if (tags !== undefined) meta.tags = tags.filter(t => t);
    if (folderId !== undefined) meta.folderId = folderId;
    meta.updatedAt = now;

    // Rewrite markdown file
    const currentContent = pathExists(found.indexPath) ? readFileSync(found.indexPath, 'utf-8') : '';
    const { body: existingBody } = parseMarkdown(currentContent);
    const newBody = content !== undefined ? content : existingBody;
    const markdown = serializeMarkdown(meta, newBody);

    writeJSON(found.metaPath, meta);
    writeFileSync(found.indexPath, markdown, 'utf-8');

    // Update tag index if tags changed
    if (tags !== undefined) {
      this.tagIndexer.updateDocumentTags(docId, oldTags, meta.tags);
    }

    return { ...meta, content: newBody };
  }

  async deleteDocument(docId) {
    const found = this._findDocById(docId);
    if (!found) {
      throw new NotFoundError('Document');
    }

    const meta = readJSON(found.metaPath);

    // Delete based on storage type
    if (found.storageType === 'folder') {
      deletePath(this._folderDocPath(found.projectId, found.folderId, docId));
    } else if (found.storageType === 'project') {
      deletePath(this._projectDocPath(found.projectId, docId));
    } else {
      deletePath(this._docPath(found.libId, docId));
    }

    this.tagIndexer.removeDocument(docId);

    return { deleted: true, id: docId };
  }

  async exportDocument(docId) {
    const found = this._findDocById(docId);
    if (!found) {
      throw new NotFoundError('Document');
    }

    const meta = readJSON(found.metaPath);
    const content = pathExists(found.indexPath) ? readFileSync(found.indexPath, 'utf-8') : '';

    return {
      id: docId,
      markdown: content,
    };
  }

  async addTagsToDocument(docId, tags) {
    const found = this._findDocById(docId);
    if (!found) {
      throw new NotFoundError('Document');
    }

    const meta = readJSON(found.metaPath);
    const oldTags = [...(meta.tags || [])];
    const newTags = [...new Set([...oldTags, ...tags.filter(t => t)])];
    meta.tags = newTags;
    meta.updatedAt = new Date().toISOString();

    writeJSON(found.metaPath, meta);

    // Update tag index
    this.tagIndexer.updateDocumentTags(docId, oldTags, newTags);

    return meta;
  }
}

let globalDocumentService = null;

export function getDocumentService(dataRoot = config.dataRoot) {
  if (!globalDocumentService) {
    globalDocumentService = new DocumentService(dataRoot);
  }
  return globalDocumentService;
}

export default DocumentService;