import { el, sleep, wait_for_dom_refresh } from "./tools";

class Word {
	private dom_root: HTMLParagraphElement;

	private inner: string;
	private is_visible: boolean;

	private static ANIMATION_DURATION: number = 20;

	public constructor(inner: string, initially_visible: boolean = false) {
		this.inner = inner;
		this.is_visible = initially_visible;
		this.dom_root = el.p(this.inner, ["word"]);

		if (!this.is_visible) {
			this.dom_root.style.opacity = "0";
			this.dom_root.style.transform = "scale(0)";
		}
	}

	public set text(new_value: string) {
		this.inner = new_value;
		this.dom_root.innerText = this.inner;
	}

	public get text(): string {
		return this.inner;
	}

	public async show(): Promise<void> {
		if (this.is_visible) { return; }
		this.dom_root.style.opacity = "1";
		this.dom_root.style.transform = "scale(100%)";
		this.is_visible = true;
		await sleep(Word.ANIMATION_DURATION);
	}

	public get visible(): boolean {
		return this.is_visible;
	}

	public get dom(): HTMLDivElement {
		return this.dom_root;
	}
}

class Paragraph {
	private dom_root: HTMLDivElement;
	private words: Word[];

	private height: number;
	private height_current: boolean;
	private visible: boolean;
	private vertical_position: number;

	private static SUBTLE_COLOR: string = "gray";
	private static ACTIVE_COLOR: string = "white";
	private static WORD_ANIM_POST_WAIT: number = 180;

	public constructor(initial_text: string | null) {
		this.dom_root = el.div([], ["paragraph"]);
		this.set_color(Paragraph.ACTIVE_COLOR);
		this.words = [];
		this.visible = true;
		this.height = 0;
		this.height_current = true;
		this.vertical_position = 0;
		this.set_initial_text(initial_text);
	}

	private set_initial_text(text: string | null): void {
		if (text === null) { return; }
		this.visible = false;
		this.height_current = false;
		this.dom_root.style.opacity = "0";
		const initial_words = text.split(" ");
		for (const word of initial_words) {
			const cur_word = new Word(word, true);
			this.words.push(cur_word);
			this.dom_root.appendChild(cur_word.dom);
		}
	}

	private set_color(new_color: string): void {
		this.dom_root.style.color = new_color;
	}

	private trim_words(target_length: number): void {
		if (this.words.length == 0 || target_length < 0) { return; }
		if (this.words.length != target_length) { this.invalidate_height(); }
		for (let i = this.words.length - 1; i >= target_length; --i) {
			const current_pop = this.words.pop();
			if (current_pop === undefined) { continue; }
			this.dom_root.removeChild(current_pop.dom);
		}
	}

	private invalidate_height(): void {
		this.height_current = false;
	}

	public set_text(new_text: string): void {
		const new_words = new_text.split(" ");
		if (new_words.length < this.words.length) { this.trim_words(new_words.length); }
		for (let i = 0; i < new_words.length; ++i) {
			const new_word = new_words[i];
			if (this.words.length <= i) {
				const cur_word = new Word(new_word);
				this.words.push(cur_word);
				this.dom_root.appendChild(cur_word.dom);
				this.invalidate_height();
				continue;
			}
			if (this.words[i].text != new_word) {
				this.words[i].text = new_word;
				this.invalidate_height();
			}
		}
	}

	public async animate(): Promise<void> {
		for (const word of this.words) {
			await word.show();
		}
		await sleep(Paragraph.WORD_ANIM_POST_WAIT);
	}

	private calculate_height(): void {
		this.height = this.dom_root.getBoundingClientRect().height;
	}

	public get real_height(): number {
		if (!this.height_current) {
			this.calculate_height();
			this.height_current = true;
		}
		return this.height;
	}

	public subtleize(): Promise<void> {
		this.set_color(Paragraph.SUBTLE_COLOR);
		return sleep(500);
	}

	public async show(): Promise<void> {
		if (this.visible) { return; }
		this.dom_root.style.opacity = "1";
		return sleep(500);
	}

	public set translate_y(value: number) {
		this.vertical_position = value;
		this.dom_root.style.transform = `translateY(${value}px)`;
	}

	public get translate_y(): number {
		return this.vertical_position;
	}

	public get dom(): HTMLDivElement {
		return this.dom_root;
	}
}

export class ScrollingTextBox {
	private dom_root: HTMLDivElement;

	private paragraphs: Paragraph[];

	private static MAX_HEIGHT: number = 650;
	private static CENTER_HEIGHT: number = 350;
	private static VERTICAL_MARGIN: number = 10;

	public constructor() {
		this.dom_root = el.div([], ["scrolling-textbox"]);
		this.paragraphs = [];
	}

	private add_paragraph(initial_text: string | null): void {
		const new_paragraph = new Paragraph(initial_text);
		new_paragraph.translate_y = ScrollingTextBox.CENTER_HEIGHT;
		this.paragraphs.push(new_paragraph);
		this.dom_root.appendChild(new_paragraph.dom);
	}

	private add_paragraph_bottom(initial_text: string): void {
		if (this.paragraphs.length == 0) {
			this.add_paragraph(initial_text);
			return;
		}
		const most_bottom = this.paragraphs[this.paragraphs.length - 1];
		const offset = most_bottom.translate_y + most_bottom.real_height;
		const new_paragraph = new Paragraph(initial_text);
		new_paragraph.translate_y = offset;
		this.paragraphs.push(new_paragraph);
		this.dom_root.appendChild(new_paragraph.dom);
	}

	/**
	 * Remove all paragraphs up to (not including) a certain index.
	*/
	private trim_to(exclusive_end: number): void {
		const spliced = this.paragraphs.splice(0, exclusive_end);
		for (const item of spliced) {
			this.dom_root.removeChild(item.dom);
		}
	}

	/**
	 * Run scroll animation on the first element and then pop it off of the DOM.
	 */
	private async scroll_trim(offset: number): Promise<void> {
		const to_trim = this.paragraphs.shift();
		if (to_trim === undefined) { return; }
		to_trim.translate_y = offset;
		await sleep(500);
		this.dom_root.removeChild(to_trim.dom);
	}

	/**
	 * Update elements DOM scrolls and wait for animations to complete.
	 *
	 * Note that this will remove any paragraphs that aren't visible anymore.
	*/
	private async update_scroll(): Promise<void> {
		if (this.paragraphs.length == 0) { return; }
		const last = this.paragraphs[this.paragraphs.length - 1];
		let offset = Math.min(
			ScrollingTextBox.MAX_HEIGHT - last.real_height, ScrollingTextBox.CENTER_HEIGHT
		);
		last.translate_y = offset;
		if (this.paragraphs.length == 1) { return; }
		for (let i = this.paragraphs.length - 2; i >= 0; --i) {
			offset -= ScrollingTextBox.VERTICAL_MARGIN;
			const cur = this.paragraphs[i];
			if (offset <= 0) {
				this.trim_to(i);
				this.scroll_trim(offset - cur.real_height);
				break;
			}
			offset -= cur.real_height;
			cur.translate_y = offset;
		}
		await sleep(500);
	}

	public async update_current(text: string): Promise<void> {
		if (this.paragraphs.length == 0) {
			this.add_paragraph(null);
			this.update_scroll();
		}
		const current = this.paragraphs[this.paragraphs.length - 1];
		current.set_text(text);
		await wait_for_dom_refresh();
		await Promise.all([this.update_scroll(), current.animate()]);
	}

	public async finish_current(text: string): Promise<void> {
		if (this.paragraphs.length == 0) {
			this.add_paragraph(text);
		}
		const current = this.paragraphs[this.paragraphs.length - 1];
		current.set_text(text);
		this.add_paragraph(null);
		await Promise.all([this.update_scroll(), current.subtleize(), current.animate()]);
	}

	public async add_line(text: string): Promise<void> {
		if (this.paragraphs.length != 0) {
			this.paragraphs[this.paragraphs.length - 1].subtleize();
		}
		this.add_paragraph_bottom(text);
		await wait_for_dom_refresh();
		await Promise.all([
			this.update_scroll(),
			this.paragraphs[this.paragraphs.length - 1].show(),
		]);
	}

	public get dom(): HTMLDivElement {
		return this.dom_root;
	}
}