"use strict";

import path from 'path';
import fs from 'fs';

import tf from '@tensorflow/tfjs-node';
// import tf from '@tensorflow/tfjs-node-gpu';
// import tf from '@tensorflow/tfjs';

import genres from './Genres.mjs';

class FilmPredictor {
	constructor(settings) {
		this.settings = settings;
		
		this.genres = genres.length;
		
		this.batch_size = 32;
		this.prefetch = 4;
	}
	
	async init(dirpath = null) {
		if(dirpath !== null)
			await this.load_model(dirpath);
		else {
			if(!fs.existsSync(this.settings.output))
				await fs.promises.mkdir(this.settings.output, { recursive: true, mode: 0o755 });
			this.dir_checkpoints = path.join(this.settings.output, "checkpoints");
			if(!fs.existsSync(this.dir_checkpoints))
				await fs.promises.mkdir(this.dir_checkpoints, { recursive: true, mode: 0o755 });
			
			this.make_model();
			
			this.model.summary();
		}
	}
	
	async load_model(dirpath) {
		if(!fs.existsSync(dirpath))
			throw new Error(`Error: The directory ${dirpath} doesn't exist.`);
		console.error(`>>> Loading model from '${dirpath}'`);
		this.model = await tf.loadLayersModel(`file://${path.resolve(dirpath, "model.json")}`);
		console.error(`>>> Model loading complete`);
	}
	
	make_model() {
		console.error(`>>> Creating new model`);
		this.model = tf.sequential();
		
		this.model.add(tf.layers.conv2d({
			name: "conv2d_1",
			dataFormat: "channelsLast",
			inputShape: [ 256, 256, 3 ],
			kernelSize: 5,
			filters: 3,
			strides: 2,
			activation: "relu"
		}));
		this.model.add(tf.layers.conv2d({
			name: "conv2d_2",
			dataFormat: "channelsLast",
			kernelSize: 5,
			filters: 3,
			strides: 2,
			activation: "relu"
		}));
		this.model.add(tf.layers.conv2d({
			name: "conv2d_3",
			dataFormat: "channelsLast",
			kernelSize: 5,
			filters: 3,
			strides: 2,
			activation: "relu"
		}));
		
		// Reshape and flatten
		let cnn_stack_output_shape = this.model.getLayer("conv2d_3").outputShape;
		this.model.add(tf.layers.reshape({
			name: "reshape",
			targetShape: [
				cnn_stack_output_shape[1] * cnn_stack_output_shape[2] * cnn_stack_output_shape[3]
			]
		}));
		this.model.add(tf.layers.dense({
			name: "dense",
			units: this.genres,
			activation: "sigmoid" // If you're only predicting a single label at a time, then choose "softmax" instead
		}));
		
		this.model.compile({
			optimizer: tf.train.adam(),
			loss: "meanSquaredError", // we want the root mean squared error, but Tensorflow.js doesn't have an option for that so we'll do it in post when graphing with jq
			metrics: [ "mse" /* meanSquaredError */ ]
		});
	}
	
	
	async train(dataset_train, dataset_validate) {
		dataset_train = dataset_train.batch(this.batch_size).prefetch(this.prefetch);
		dataset_validate = dataset_validate.batch(this.batch_size).prefetch(this.prefetch);
		
		await this.model.fitDataset(dataset_train, {
			epochs: 50,
			verbose: 1,
			validationData: dataset_validate,
			yieldEvery: "batch",
			shuffle: false,
			callbacks: {
				onEpochEnd: async (epoch, metrics) => {
					console.error(`>>> Epoch ${epoch} complete, metrics:`, metrics);
					let dir_output_checkpoint = `file://${path.join(this.dir_checkpoints, `${epoch.toString()}`)}`;
					await Promise.all([
						this.model.save(dir_output_checkpoint),
						fs.promises.appendFile(
							path.join(this.settings.output, `metrics.stream.json`), JSON.stringify(metrics) + "\n"
						)
					]);
				}
			}
		})
	}
	
	async predict(imagefilepath) {
		if(!fs.existsSync(imagefilepath))
			throw new Error(`Error: No file exists at '${imagefilepath}'`);
		
		let image_data = await fs.promises.readFile(imagefilepath);
		
		let imagetensor = tf.tidy(() => {
			let image = tf.node.decodeImage(
				image_data,
				3 // channels
			);
			return image.reshape([1, ...image.shape ]);
		})
		let result_array = (await this.model.predict(imagetensor).array())[0];
		return this.array2genres(result_array);
	}
	
	array2genres(arr) {
		let result = [];
		for(let i = 0; i < arr.length; i++) {
			if(arr[i] < 0.5)
				continue;
			result.push(genres[i]);
		}
		return result;
	}
}

export default FilmPredictor;