import { toIso639 } from '../../locale';
import Resource from '../../models/Resource';
import Setting from '../../models/Setting';
import shim from '../../shim';
import { ResourceEntity, ResourceOcrStatus } from '../database/types';
import OcrDriverBase from './OcrDriverBase';
import { RecognizeResult } from './utils/types';
import { Minute } from '@joplin/utils/time';
import Logger from '@joplin/utils/Logger';
import filterOcrText from './utils/filterOcrText';
import TaskQueue from '../../TaskQueue';
import eventManager, { EventName } from '../../eventManager';

const logger = Logger.create('OcrService');

// From: https://github.com/naptha/tesseract.js/blob/master/docs/image-format.md
export const supportedMimeTypes = [
	'application/pdf',
	'image/bmp',
	'image/jpeg',
	'image/jpg',
	'image/png',
	'image/webp',
	'image/x-portable-bitmap',
];

const resourceInfo = (resource: ResourceEntity) => {
	return `${resource.id} (type ${resource.mime})`;
};

export default class OcrService {

	private driver_: OcrDriverBase;
	private isRunningInBackground_ = false;
	private maintenanceTimer_: any = null;
	private pdfExtractDir_: string = null;
	private isProcessingResources_ = false;
	private recognizeQueue_: TaskQueue = null;

	public constructor(driver: OcrDriverBase) {
		this.driver_ = driver;
		this.recognizeQueue_ = new TaskQueue('recognize', logger);
		this.recognizeQueue_.setConcurrency(5);
		this.recognizeQueue_.keepTaskResults = false;
	}

	private async pdfExtractDir(): Promise<string> {
		if (this.pdfExtractDir_ !== null) return this.pdfExtractDir_;
		const p = `${Setting.value('tempDir')}/ocr_pdf_extract`;
		await shim.fsDriver().mkdir(p);
		this.pdfExtractDir_ = p;
		return this.pdfExtractDir_;
	}

	public get running() {
		return this.runInBackground;
	}

	private async recognize(language: string, resource: ResourceEntity): Promise<RecognizeResult> {
		if (resource.encryption_applied) throw new Error(`Cannot OCR encrypted resource: ${resource.id}`);

		const resourceFilePath = Resource.fullPath(resource);

		if (resource.mime === 'application/pdf') {
			// OCR can be slow for large PDFs.
			// Skip it if the PDF already includes text.
			const pageTexts = await shim.pdfExtractEmbeddedText(resourceFilePath);
			const pagesWithText = pageTexts.filter(text => !!text.trim().length);

			if (pagesWithText.length > 0) {
				return {
					text: pageTexts.join('\n'),
				};
			}

			const imageFilePaths = await shim.pdfToImages(resourceFilePath, await this.pdfExtractDir());
			const results: RecognizeResult[] = [];

			let pageIndex = 0;
			for (const imageFilePath of imageFilePaths) {
				logger.info(`Recognize: ${resourceInfo(resource)}: Processing PDF page ${pageIndex + 1} / ${imageFilePaths.length}...`);
				results.push(await this.driver_.recognize(language, imageFilePath));
				pageIndex++;
			}

			for (const imageFilePath of imageFilePaths) {
				await shim.fsDriver().remove(imageFilePath);
			}

			return {
				text: results.map(r => r.text).join('\n'),
			};
		} else {
			return this.driver_.recognize(language, resourceFilePath);
		}
	}

	public async dispose() {
		await this.driver_.dispose();
	}

	public async processResources() {
		if (this.isProcessingResources_) return;

		this.isProcessingResources_ = true;

		const totalResourcesToProcess = await Resource.needOcrCount(supportedMimeTypes);
		const inProcessResourceIds: string[] = [];
		const skippedResourceIds: string[] = [];

		logger.info(`Found ${totalResourcesToProcess} resources to process...`);

		const makeQueueAction = (totalProcessed: number, language: string, resource: ResourceEntity) => {
			return async () => {
				logger.info(`Processing resource ${totalProcessed + 1} / ${totalResourcesToProcess}: ${resourceInfo(resource)}...`);

				const toSave: ResourceEntity = {
					id: resource.id,
				};

				try {
					const fetchStatus = await Resource.localState(resource.id);

					if (fetchStatus.fetch_status === Resource.FETCH_STATUS_ERROR) {
						throw new Error(`Cannot process resource ${resourceInfo(resource)} because it cannot be fetched from the server: ${fetchStatus.fetch_error}`);
					}

					if (fetchStatus.fetch_status !== Resource.FETCH_STATUS_DONE) {
						skippedResourceIds.push(resource.id);
						logger.info(`Skipping resource ${resourceInfo(resource)} because it has not been downloaded yet`);
						return;
					}

					const result = await this.recognize(language, resource);
					toSave.ocr_status = ResourceOcrStatus.Done;
					toSave.ocr_text = filterOcrText(result.text);
					toSave.ocr_details = Resource.serializeOcrDetails(result.lines),
					toSave.ocr_error = '';
				} catch (error) {
					const errorMessage = typeof error === 'string' ? error : error?.message;
					logger.warn(`Could not process resource ${resourceInfo(resource)}`, error);
					toSave.ocr_status = ResourceOcrStatus.Error;
					toSave.ocr_text = '';
					toSave.ocr_details = '';
					toSave.ocr_error = errorMessage || 'Unknown error';
				}

				await Resource.save(toSave);
			};
		};

		try {
			const language = toIso639(Setting.value('locale'));

			let totalProcessed = 0;

			while (true) {
				const resources = await Resource.needOcr(supportedMimeTypes, skippedResourceIds.concat(inProcessResourceIds), 100, {
					fields: [
						'id',
						'mime',
						'file_extension',
						'encryption_applied',
					],
				});

				if (!resources.length) break;

				for (const resource of resources) {
					inProcessResourceIds.push(resource.id);
					await this.recognizeQueue_.pushAsync(resource.id, makeQueueAction(totalProcessed++, language, resource));
				}
			}

			await this.recognizeQueue_.waitForAll();

			if (totalProcessed) {
				eventManager.emit(EventName.OcrServiceResourcesProcessed);
			}

			logger.info(`${totalProcessed} resources have been processed.`);
		} finally {
			this.isProcessingResources_ = false;
		}
	}

	public async maintenance() {
		await this.processResources();
	}

	public async runInBackground() {
		if (this.isRunningInBackground_) return;

		this.isRunningInBackground_ = true;

		if (this.maintenanceTimer_) return;

		logger.info('Starting background service...');

		await this.maintenance();

		this.maintenanceTimer_ = shim.setInterval(async () => {
			await this.maintenance();
			this.maintenanceTimer_ = null;
		}, 5 * Minute);
	}

	public async stopRunInBackground() {
		logger.info('Stopping background service...');

		if (this.maintenanceTimer_) shim.clearInterval(this.maintenanceTimer_);
		this.maintenanceTimer_ = null;
		this.isRunningInBackground_ = false;
		await this.recognizeQueue_.stop();
	}

}