type GameState = 'running' | 'paused' | 'not-started' | 'finished';

const nope = (x: never): void => {};

type PieceCell = 0 | 1;
type PieceLayout = PieceCell[][];

interface UIElement {
	render(context: CanvasRenderingContext2D, options: UIElementRenderOptions): void;
}

interface Dimensions {
	width: number;
	height: number;
}

interface GlobalUIOptions {
	pixelSize: number;
	padding: number;
	canvas: HTMLCanvasElement;
	context: CanvasRenderingContext2D;
	gridLines: false | number;
	borderWidth: number;
	hud: Dimensions;
	playArea: Dimensions;
}

interface UIElementRenderOptions extends GlobalUIOptions {
	x: number;
	y: number;
}

interface PieceTranslation {
	xDelta: number;
	yDelta: number;
}

interface TetrissimoCoordinates {
	x: number;
	y: number;
}

interface RectangleCoordinates extends TetrissimoCoordinates, Dimensions {}

type PieceActionType =
	'moveLeft' |
	'moveRight' |
	'moveDown' |
	'rotateLeft' |
	'rotateRight';

interface PieceAction {
	type: PieceActionType;
}

const getSize = (value: number, options: Pick<GlobalUIOptions, 'pixelSize'>): number => value * options.pixelSize;

const drawBorderedRect = (
	position: Dimensions & TetrissimoCoordinates,
	context: CanvasRenderingContext2D,
	options: UIElementRenderOptions,
): void => {
	const borderWidth = options.borderWidth;
	if (!borderWidth) {
		return;
	}

	const actualLineWidth = getSize(borderWidth, options);
	context.lineWidth = actualLineWidth;
	context.strokeStyle = 'white';
	context.strokeRect(
		getSize(position.x, options) - Math.round(actualLineWidth / 2),
		getSize(position.y, options) - Math.round(actualLineWidth / 2),
		getSize(position.width, options) + actualLineWidth,
		getSize(position.height, options) + actualLineWidth,
	);
};

class TetrissimoLevel {
	public readonly order: number;
	public readonly movementsPerSecond: number;

	public static readonly level1 = new TetrissimoLevel(1, 0.5);
	public static readonly level2 = new TetrissimoLevel(2, 0.75);
	public static readonly level3 = new TetrissimoLevel(2, 1);
	public static readonly level4 = new TetrissimoLevel(2, 1.5);
	public static readonly level5 = new TetrissimoLevel(2, 2);
	public static readonly level6 = new TetrissimoLevel(2, 3);
	public static readonly level7 = new TetrissimoLevel(2, 4);
	public static readonly level8 = new TetrissimoLevel(2, 6);
	public static readonly level9 = new TetrissimoLevel(2, 8);
	public static readonly level10 = new TetrissimoLevel(2, 10);

	public constructor(order: number, speed: number) {
		this.order = order;
		this.movementsPerSecond = speed;
	}
}

class TetrissimoGame {
	private startedAt: Date | null = null;
	private pausedAt: Date | null = null;
	private finishedAt: Date | null = null;
	private state: GameState = 'not-started';
	private fps = 60;
	private readonly ui: TetrissimoUI;
	private lastFrameTimes: number[] = [];
	private readonly pieces: TetrissimoPiece[] = [];
	public currentLevel: TetrissimoLevel = TetrissimoLevel.level1;
	private msUntilNextTick = 0;
	private lastTick = new Date();
	private lastUpdate = new Date();

	public constructor(ui: TetrissimoUI) {
		this.ui = ui;
	}

	public getState(): GameState {
		return this.state;
	}

	public setTargetFps(fps: number) {
		this.fps = fps;
	}

	public setLevel(level: TetrissimoLevel) {
		this.currentLevel = level;
	}

	public getCurrentFps(): number {
		switch (this.state) {
			case 'running':
				if (this.lastFrameTimes.length <= 1) {
					return 0;
				}

				const firstFrame = this.lastFrameTimes[0];
				const lastFrame = this.lastFrameTimes[this.lastFrameTimes.length - 1];
				const elapsedMs = lastFrame - firstFrame;
				const avgMsPerFrame = (elapsedMs / this.lastFrameTimes.length);
				return 1000 / avgMsPerFrame;
			case 'paused':
			case 'not-started':
			case 'finished':
				return 0;
			default:
				nope(this.state);
				throw new Error(`Invalid game state "${this.state}"`);
		}
	}

	public performPieceAction(action: PieceAction) {
		if (this.state !== 'running') {
			return;
		}

		const piece = this.pieces.filter(piece => piece.state === 'in-play')[0];
		if (!piece) {
			// nothing to do, no pieces in play
			return;
		}

		const movementIncrement = 1;

		switch (action.type) {
			case 'moveLeft':
				this.moveIfValid(piece, -movementIncrement, 0);
				break;
			case 'moveRight':
				this.moveIfValid(piece, movementIncrement, 0);
				break;
			case 'moveDown':
				if (!this.moveIfValid(piece, 0, movementIncrement)) {
					// make fixed to bottom of play area
					piece.setFixed();
				}
				break;
			case 'rotateLeft':
				// TODO ensure it's a valid move
				piece.rotateLeft();
				break;
			case 'rotateRight':
				piece.rotateRight();
				break;
			default:
				nope(action.type);
				throw new Error(`invalid action "${action.type}"`);
		}
	}

	public start() {
		this.pausedAt = null;

		switch (this.state) {
			case 'running':
				// no-op
				break;
			case 'paused':
			case 'not-started':
				this.lastTick = new Date();
				this.lastUpdate = new Date();
				this.startedAt = new Date();
				this.state = 'running';
				this.update();
				break;
			case 'finished':
				throw new Error('Cannot start a finished game');
			default:
				nope(this.state);
				throw new Error(`Invalid game state "${this.state}"`);
		}
	}

	public pause() {
		switch (this.state) {
			case 'running':
			case 'paused':
				this.pausedAt = new Date();
				this.state = 'paused';
				this.lastFrameTimes = [];
				break;
			case 'not-started':
			case 'finished':
				throw new Error(`Cannot pause game while it's in state "${this.state}"`);
			default:
				nope(this.state);
				throw new Error(`Invalid game state "${this.state}"`);
		}
	}

	public update(): void {
		const tickStart = Date.now();
		this.lastFrameTimes.push(tickStart);
		if (this.lastFrameTimes.length > 20) {
			this.lastFrameTimes.shift();
		}

		switch (this.state) {
			case 'running':
				this.performUpdate();
				break;
			case 'paused':
			case 'not-started':
			case 'finished':
				throw new Error(`Cannot advance game while in state "${this.state}"`);
			default:
				nope(this.state);
				throw new Error(`Invalid game state "${this.state}"`);
		}

		const elapsed = Date.now() - tickStart;
		const nextTickTimeout = Math.max(0, (1000 / this.fps) - elapsed);
		setTimeout(() => {
			switch (this.state) {
				case 'running':
					this.update();
					break;
				case 'paused':
				case 'not-started':
				case 'finished':
					break;
				default:
					nope(this.state);
					throw new Error(`Invalid game state "${this.state}"`);
			}
		}, nextTickTimeout);
	}

	private performUpdate(): void {
		const sinceLastUpdate = Date.now() - this.lastUpdate.getTime();
		this.msUntilNextTick -= sinceLastUpdate;
		this.lastUpdate = new Date();

		if (this.msUntilNextTick <= 0) {
			this.tick();
		}

		// detect collision
		// is every column filled? remove column
		// is every row filled? end game

		ui.update();
	}

	private moveIfValid(piece: TetrissimoPiece, xDelta: number, yDelta: number): boolean {
		const translation: PieceTranslation = {
			xDelta,
			yDelta,
		};
		if (this.ui.canMovePiece(piece, translation)) {
			piece.move(translation);
			return true;
		}

		return false;
	};

	private tick(): void {
		const inPlayPieces = this.pieces.filter(piece => piece.state === 'in-play');
		if (!inPlayPieces.length) {
			const newPiece = TetrissimoPiece.T.clone();
			newPiece.state = 'in-play';
			this.pieces.push(newPiece);
			this.ui.addPiece(newPiece);
		} else {
			inPlayPieces.forEach((piece) => {
				if (!this.moveIfValid(piece, 0, 1)) {
					piece.setFixed();
				}
			});
		}

		this.msUntilNextTick = Math.round(1000 / this.currentLevel.movementsPerSecond);
		this.lastTick = new Date();
	}
}

class TetrissimoUI {
	public readonly playArea: TetrissimoPlayArea;
	private readonly pieces: Array<Readonly<TetrissimoPiece>> = [];
	public readonly nextBox: TetrissimoNextBox;
	public readonly hud: TetrissimoHUD;
	public readonly options: GlobalUIOptions;

	public constructor(
		canvas: HTMLCanvasElement,
		playArea: TetrissimoPlayArea,
		// nextBox: TetrissimoNextBox,
		hud: TetrissimoHUD,
	) {
		this.playArea = playArea;
		// this.nextBox = nextBox;
		this.hud = hud;

		const context = canvas.getContext('2d');
		if (!context) {
			throw new Error('failed to get 2d context');
		}
		this.options = {
			borderWidth: 1,
			canvas: canvas,
			context,
			gridLines: 4,
			hud: {
				width: 32,
				height: 12,
			},
			playArea: {
				width: 68,
				height: 128,
			},
			padding: 2,
			pixelSize: 4,
		};
	}

	public setOptions(options: Omit<GlobalUIOptions, 'canvas' | 'context'>) {
		Object.keys(options).forEach((key) => {
			this.options[key] = options[key];
		});
	}

	public addPiece(piece: TetrissimoPiece) {
		this.pieces.push(piece);
	}

	private getPiecePosition(piece: Readonly<TetrissimoPiece>): TetrissimoCoordinates {
		const origin = this.getPieceOrigin(piece);
		const offset = piece.getOffset();

		return {
			x: origin.x + offset.x,
			y: origin.y + offset.y,
		};
	}

	public canMovePiece(piece: Readonly<TetrissimoPiece>, delta: PieceTranslation): boolean {
		// check each block in layout's edge to see if it's in a valid area?s

		const layout = piece.getLayout();
		const position = this.getPiecePosition(piece);

		for (let i = 0; i < layout.length; i++) {
			const blockTopEdge = position.y + (i * TetrissimoPiece.blockLength) + (delta.yDelta * TetrissimoPiece.blockLength);
			for (let j = 0; j < layout[i].length; j++) {
				if (layout[i][j] === 0) {
					continue;
				}

				const blockLeftEdge = position.x + (j * TetrissimoPiece.blockLength) + (delta.xDelta * TetrissimoPiece.blockLength);

				const isCollision = this.hasCollision({
					x: blockLeftEdge,
					y: blockTopEdge,
					width: TetrissimoPiece.blockLength,
					height: TetrissimoPiece.blockLength,
				});

				if (isCollision) {
					return false;
				}
			}
		}

		return true;
	}

	private hasCollision(rect: RectangleCoordinates): boolean {
		const playAreaLeftEdge = this.options.padding;
		const playAreaRightEdge = playAreaLeftEdge + this.options.playArea.width;
		const playAreaTopEdge = this.options.padding;
		const playAreaBottomEdge = playAreaTopEdge + this.options.playArea.height;

		const leftEdge = rect.x;
		const rightEdge = rect.x + rect.width;
		const topEdge = rect.y;
		const bottomEdge = rect.y + rect.height;

		const isInPlayArea =
			leftEdge >= playAreaLeftEdge &&
			rightEdge <= playAreaRightEdge &&
			bottomEdge <= playAreaBottomEdge &&
			topEdge >= playAreaTopEdge;

		if (!isInPlayArea) {
			return true;
		}

		const fixedPieces = this.pieces.filter(piece => piece.state === 'fixed');
		for (const piece of fixedPieces) {
			const position = this.getPiecePosition(piece);
			const layout = piece.getLayout();
			for (let i = 0; i < layout.length; i++) {
				const blockTopEdge = position.y + (i * TetrissimoPiece.blockLength);
				const blockBottomEdge = blockTopEdge + TetrissimoPiece.blockLength;
				for (let j = 0; j < layout[i].length; j++) {
					if (layout[i][j] === 0) {
						continue;
					}

					const blockLeftEdge = position.x + (j * TetrissimoPiece.blockLength);
					const blockRightEdge = blockLeftEdge + TetrissimoPiece.blockLength;

					const isCollision =
						leftEdge >= blockLeftEdge &&
						rightEdge <= blockRightEdge &&
						bottomEdge <= blockBottomEdge &&
						topEdge >= blockTopEdge;

					if (isCollision) {
						return true;
					}
				}
			}
		}

		return false;
	}

	public update() {
		const options = this.options;
		const context = this.options.context;

		context.clearRect(0, 0, canvas.width, canvas.height);

		// fill background
		context.fillStyle = 'rgb(224,158,107)';
		context.fillRect(0, 0, canvas.width, canvas.height);

		// draw some grid lines
		if (typeof(options.gridLines) === 'number') {
			context.strokeStyle = 'rgba(255, 255, 255, 0.25)';
			context.lineWidth = 1;
			const increment = options.pixelSize * options.gridLines;
			for (let i = 0; i < options.canvas.width; i += increment) {
				// draw vertical line
				context.beginPath();
				context.moveTo(i, 0);
				context.lineTo(i, options.canvas.height);
				context.stroke();
			}
			for (let i = 0; i < options.canvas.height; i += increment) {
				// draw horizontal lines
				context.beginPath();
				context.moveTo(0, i);
				context.lineTo(options.canvas.width, i);
				context.stroke();
			}
		}

		const totalWidth = Math.floor(canvas.width / options.pixelSize);
		const padding = options.padding;

		// draw HUD in top right corner
		this.hud.render(context, {
			...options,
			x: totalWidth - padding - options.hud.width,
			y: padding,
		});

		// draw play area
		this.playArea.render(context, {
			...options,
			x: padding,
			y: padding,
		});

		this.pieces.forEach((piece, i) => {
			piece.render(context, {
				...options,
				...this.getPieceOrigin(piece),
			});
		});
	}

	private getPieceOrigin(piece: Readonly<TetrissimoPiece>): TetrissimoCoordinates {
		const length = TetrissimoPiece.blockLength;
		// TODO rotation will cause problems, need a "PieceDefinition" or something with a static layout
		let translateX = Math.floor((piece.getBlockWidth() * length) / 2);

		// we can only perform movements in multiples of the blockLength, so we must clamp it
		// to ensure it's not offset
		translateX -= (translateX % length);
		const padding = this.options.padding;
		return {
			x: padding + Math.round(this.options.playArea.width / 2) - translateX,
			y: padding,
		};
	}
}

class TetrissimoNextBox implements UIElement {
	public render(context: CanvasRenderingContext2D, options: UIElementRenderOptions) {

	}
}

class TetrissimoHUD implements UIElement {
	public render(context: CanvasRenderingContext2D, options: UIElementRenderOptions) {
		const position = {
			x: options.x,
			y: options.y,
			width: options.hud.width,
			height: options.hud.height,
		};
		drawBorderedRect(position, context, options);
	}
}

class TetrissimoPlayArea implements UIElement {
	public render(context: CanvasRenderingContext2D, options: UIElementRenderOptions) {
		const position = {
			x: options.x,
			y: options.y,
			width: options.playArea.width,
			height: options.playArea.height,
		};
		drawBorderedRect(position, context, options);
	}
}

type PieceState = 'in-play' | 'fixed';

class TetrissimoPiece implements UIElement {
	public readonly name: string;
	private readonly originalLayout: Readonly<PieceLayout>;
	private layout: PieceLayout;
	private offset: TetrissimoCoordinates = { x: 0, y: 0 };
	private readonly color: string;
	public static readonly blockLength = 4;
	public state: PieceState = 'in-play';

	public static readonly J = new TetrissimoPiece(
		'J',
		[
			[0, 1],
			[0, 1],
			[1, 1],
		],
		'black',
	);
	public static readonly S: TetrissimoPiece = new TetrissimoPiece(
		'S',
		[
			[0, 1, 1],
			[1, 1, 0],
		],
		'green',
	);
	public static readonly T: TetrissimoPiece = new TetrissimoPiece(
		'T',
		[
			[1, 1, 1],
			[0, 1, 0],
		],
		'blue',
	);
	public static readonly Z: TetrissimoPiece = new TetrissimoPiece(
		'Z',
		[
			[1, 1, 0,],
			[0, 1, 1,],
		],
		'yellow',
	);
	public static readonly I: TetrissimoPiece = new TetrissimoPiece(
		'I',
		[
			[1, 1, 1, 1],
		],
		'magenta',
	);
	public static readonly L: TetrissimoPiece = new TetrissimoPiece(
		'L',
		[
			[1],
			[1],
			[1, 1],
		],
		'cyan',
	);
	public static readonly O: TetrissimoPiece = new TetrissimoPiece(
		'O',
		[
			[1, 1],
			[1, 1],
		],
		'red',
	);

	public constructor(name: string, layout: PieceLayout, color: string) {
		this.name = name;
		this.originalLayout = layout.map(row => row.concat([]));
		this.layout = layout.concat([]);
		this.color = color;
	}

	public getOffset(): Readonly<TetrissimoCoordinates> {
		return this.offset;
	}

	public getLayout(): Readonly<PieceLayout> {
		return this.layout;
	}

	public move(translation: PieceTranslation) {
		if (this.state !== 'in-play') {
			return;
		}

		this.offset.x += (translation.xDelta * TetrissimoPiece.blockLength);
		this.offset.y += (translation.yDelta * TetrissimoPiece.blockLength);
	}

	public rotateLeft() {
		if (this.state !== 'in-play') {
			return;
		}

		// clockwise turn
		const newLayout: PieceLayout = [];
		for (let i = 0; i < this.layout.length; i++) {
			const col = this.layout.length - 1 - i;
			for (let j = 0; j < this.layout[i].length; j++) {
				const row = j;
				if (!newLayout[row]) {
					newLayout[row] = [];
				}
				newLayout[row][col] = this.layout[i][j];
			}
		}

		this.layout = newLayout;
	}

	public rotateRight() {
		if (this.state !== 'in-play') {
			return;
		}

		const newLayout: PieceLayout = [];
		for (let i = 0; i < this.layout.length; i++) {
			const col = i;
			for (let j = 0; j < this.layout[i].length; j++) {
				const row = this.layout[i].length - 1 - j;
				if (!newLayout[row]) {
					newLayout[row] = [];
				}
				newLayout[row][col] = this.layout[i][j];
			}
		}

		this.layout = newLayout;
	}

	public setFixed() {
		this.state = 'fixed';
	}

	public getBlockWidth(): number {
		return this.layout
			.map(arr => arr.filter(value => value === 1).length)
			.reduce((max, len) => Math.max(max, len), 0);
	}

	public getBlockHeight(): number {
		const cols: PieceCell[][] = [];
		for (let i = 0; i < this.layout.length; i++) {
			for (let j = 0; j < this.layout[i].length; j++) {
				if (!cols[j]) {
					cols[j] = [];
				}
				cols[j].push(this.layout[i][j]);
			}
		}

		return cols
			.map(arr => arr.filter(value => value === 1).length)
			.reduce((max, len) => Math.max(max, len), 0);
	}

	public clone(): TetrissimoPiece {
		return new TetrissimoPiece(this.name, this.layout, this.color);
	}

	public render(context: CanvasRenderingContext2D, options: UIElementRenderOptions) {
		this.layout.forEach((columns, rowNum) => {
			columns.forEach((value, colNum) => {
				switch (value) {
					case 0:
						break;
					case 1:
						context.fillStyle = this.color;
						const length = TetrissimoPiece.blockLength;
						const offsetX = this.offset.x;
						const offsetY = this.offset.y;

						const x = options.x + offsetX + (colNum * length);
						const y = options.y + offsetY + (rowNum * length);
						const actualLength = getSize(length, options);
						context.fillRect(getSize(x, options), getSize(y, options), actualLength, actualLength);
						break;
					default:
						nope(value);
						throw new Error(`Invalid piece cell value "${value}"`);
				}
			});
		});
	}
}

// ---------------------------------------------

const hud = new TetrissimoHUD();
const playArea = new TetrissimoPlayArea();

const canvas = document.getElementsByTagName('canvas')[0];
if (!canvas) {
	throw new Error('no canvas');
}

const ui = new TetrissimoUI(canvas, playArea, hud);
const game = new TetrissimoGame(ui);