import Row from './row.ts';
import { getRuntime } from './runtime.ts';
import { Position } from './mod.ts';

export class Document {
	#filename: string | null;
	#rows: Row[];
	dirty: boolean;

	private constructor() {
		this.#rows = [];
		this.#filename = null;
		this.dirty = false;
	}

	get numRows(): number {
		return this.#rows.length;
	}

	public static empty(): Document {
		return new Document();
	}

	public isEmpty(): boolean {
		return this.#rows.length === 0;
	}

	public async open(filename: string): Promise<Document> {
		const { file } = await getRuntime();

		// Clear any existing rows
		if (!this.isEmpty()) {
			this.#rows = [];
		}

		const rawFile = await file.openFile(filename);
		rawFile.split(/\r?\n/)
			.forEach((row) => this.appendRow(row));

		this.#filename = filename;
		this.dirty = false;

		return this;
	}

	public async save() {
		if (this.#filename === null) {
			return;
		}

		const { file } = await getRuntime();

		await file.saveFile(this.#filename, this.rowsToString());

		this.dirty = false;
	}

	public insert(at: Position, c: string): void {
		if (at.y === this.numRows) {
			this.appendRow(c);
		} else {
			this.#rows[at.y].insertChar(at.x, c);
			this.#rows[at.y].updateRender();
		}

		this.dirty = true;
	}

	public delete(at: Position): void {
		const len = this.numRows;
		if (at.y >= len) {
			return;
		}

		const row = this.row(at.y)!;
		const mergeNextRow = at.x === row.size - 1 && at.y < len - 1;
		const mergeIntoPrevRow = at.x === 0 && at.y > 0;

		// If we are at the end of a line, and press delete,
		// add the contents of the next row, and delete
		// the merged row object
		if (mergeNextRow) {
			// At the end of a line, pressing delete will merge
			// the next line into the current on
			const rowToAppend = this.#rows.at(at.y + 1)!.toString();
			row.append(rowToAppend);
			this.deleteRow(at.y + 1);
		} else if (mergeIntoPrevRow) {
			// At the beginning of a line, merge the current line
			// into the previous Row
			const rowToAppend = row.toString();
			this.#rows[at.y - 1].append(rowToAppend);
			this.deleteRow(at.y);
		} else {
			row.delete(at.x);
		}

		row.updateRender();

		this.dirty = true;
	}

	public row(i: number): Row | null {
		return this.#rows[i] ?? null;
	}

	public appendRow(s: string): void {
		const at = this.numRows;
		this.#rows[at] = new Row(s);
		this.#rows[at].updateRender();

		this.dirty = true;
	}

	/**
	 * Delete the specified row
	 * @param at - the index of the row to delete
	 * @private
	 */
	private deleteRow(at: number): void {
		this.#rows.splice(at, 1);
	}

	private rowsToString(): string {
		return this.#rows.map((r) => r.toString()).join('\n');
	}
}

export default Document;