///<reference types="node"/>

import {createHash} from "crypto";
import {pathExistsSync, readFile, readFileSync, writeFile, writeFileSync} from "fs-extra";

function md5(data: Buffer|string, charset?: 'utf8') {
	return createHash('md5')
		.update(data, charset)
		.digest('hex')
}

export class FileChange {
	public readonly fileExists: boolean;
	private knownMd5: string;
	private fileBuffer: Buffer;
	private md5Value: string;
	
	constructor(private file: string, private md5File: string) {
		this.fileExists = pathExistsSync(this.file);
		if (pathExistsSync(this.md5File)) {
			this.knownMd5 = readFileSync(this.md5File, {encoding: 'utf8'})
		} else {
			this.knownMd5 = null;
		}
	}
	
	public get changed() {
		// console.log(this.fileExists, this.knownMd5, this.md5, this.knownMd5);
		return !(
			this.fileExists &&
			this.knownMd5 &&
			this.md5 === this.knownMd5
		);
	}
	
	public get md5(): string {
		if (!this.md5Value) {
			this.md5Value = md5(this.readFileSync());
		}
		return this.md5Value;
	}
	
	public readFileSync() {
		if (!this.fileBuffer) {
			this.fileBuffer = readFileSync(this.file);
		}
		return this.fileBuffer;
	}
	
	public async readFile(): Promise<Buffer> {
		if (!this.fileBuffer) {
			this.fileBuffer = await readFile(this.file);
		}
		return this.fileBuffer;
	}
	
	public writeFileSync(newContent: string) {
		const newMd5 = md5(newContent, 'utf8');
		if (newMd5 !== this.knownMd5) {
			writeFileSync(this.file, newContent, 'utf8');
			this.md5Value = newMd5;
			this.fileBuffer = new Buffer(newContent, 'utf8');
		}
	}
	
	public async writeFile(newContent: string): Promise<void> {
		const newMd5 = md5(newContent, 'utf8');
		if (newMd5 !== this.knownMd5) {
			await writeFile(this.file, newContent, {encoding: 'utf8'});
			this.md5Value = newMd5;
			this.fileBuffer = new Buffer(newContent, 'utf8');
		}
	}
	
	store() {
		this.knownMd5 = md5(this.readFileSync());
		this.writeMd5Sync();
	}
	
	private writeMd5(): Promise<void> {
		return writeFile(this.md5File, this.knownMd5);
	}
	
	private writeMd5Sync(): void {
		writeFileSync(this.md5File, this.knownMd5);
	}
}