const ItemChange = require('lib/models/ItemChange');
const NoteResource = require('lib/models/NoteResource');
const Note = require('lib/models/Note');
const Resource = require('lib/models/Resource');
const BaseModel = require('lib/BaseModel');
const BaseService = require('lib/services/BaseService');
const Setting = require('lib/models/Setting');
const { shim } = require('lib/shim');

class ResourceService extends BaseService {

	async indexNoteResources() {
		this.logger().info('ResourceService::indexNoteResources: Start');

		await ItemChange.waitForAllSaved();

		while (true) {
			const changes = await ItemChange.modelSelectAll(`
				SELECT id, item_id, type
				FROM item_changes
				WHERE item_type = ?
				AND id > ?
				ORDER BY id ASC
				LIMIT 100
			`, [BaseModel.TYPE_NOTE, Setting.value('resourceService.lastProcessedChangeId')]);

			if (!changes.length) break;

			const noteIds = changes.map(a => a.item_id);
			const notes = await Note.modelSelectAll('SELECT id, title, body FROM notes WHERE id IN ("' + noteIds.join('","') + '")');

			const noteById = (noteId) => {
				for (let i = 0; i < notes.length; i++) {
					if (notes[i].id === noteId) return notes[i];
				}
				// The note may have been deleted since the change was recorded. For example in this case:
				// - Note created (Some Change object is recorded)
				// - Note is deleted
				// - ResourceService indexer runs.
				// In that case, there will be a change for the note, but the note will be gone.
				return null;
			}

			for (let i = 0; i < changes.length; i++) {
				const change = changes[i];

				if (change.type === ItemChange.TYPE_CREATE || change.type === ItemChange.TYPE_UPDATE) {
					const note = noteById(change.item_id);
					if (note) {
						const resourceIds = await Note.linkedResourceIds(note.body);
						await NoteResource.setAssociatedResources(note.id, resourceIds);
					} else {
						this.logger().warn('ResourceService::indexNoteResources: A change was recorded for a note that has been deleted: ' + change.item_id);
					}
				} else if (change.type === ItemChange.TYPE_DELETE) {
					await NoteResource.remove(change.item_id);
				} else {
					throw new Error('Invalid change type: ' + change.type);
				}

				Setting.setValue('resourceService.lastProcessedChangeId', change.id);
			}
		}

		await Setting.saveAll();

		await NoteResource.addOrphanedResources();

		this.logger().info('ResourceService::indexNoteResources: Completed');
	}

	async deleteOrphanResources(expiryDelay = null) {
		const resourceIds = await NoteResource.orphanResources(expiryDelay);
		this.logger().info('ResourceService::deleteOrphanResources:', resourceIds);
		for (let i = 0; i < resourceIds.length; i++) {
			await Resource.delete(resourceIds[i]);
		}
	}

	async maintenance() {
		await this.indexNoteResources();
		await this.deleteOrphanResources();
	}

	static runInBackground() {
		if (this.isRunningInBackground_) return;

		this.isRunningInBackground_ = true;
		const service = new ResourceService();

		setTimeout(() => {
			service.maintenance();
		}, 1000 * 30);
		
		shim.setInterval(() => {
			service.maintenance();
		}, 1000 * 60 * 60 * 4);
	}

}

module.exports = ResourceService;