import Row from './row.ts';
import { arrayInsert, maxAdd, minSub } from './fns.ts';
import Option, { None, Some } from './option.ts';
import { getRuntime } from './runtime.ts';
import { Position, SearchDirection } from './types.ts';

export class Document {
	#rows: Row[];

	/**
	 * Has the document been modified?
	 */
	public dirty: boolean;

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

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

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

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

	/**
	 * Open a file for editing
	 */
	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.insertRow(this.numRows, row));

		this.dirty = false;

		return this;
	}

	/**
	 * Save the current document
	 */
	public async save(filename: string): Promise<void> {
		const { file } = await getRuntime();

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

		this.dirty = false;
	}

	public find(
		q: string,
		at: Position,
		direction: SearchDirection = SearchDirection.Forward,
	): Option<Position> {
		if (at.y >= this.numRows) {
			return None;
		}

		const position = Position.from(at);

		const start = (direction === SearchDirection.Forward) ? at.y : 0;
		const end = (direction === SearchDirection.Forward)
			? this.numRows
			: maxAdd(at.y, 1, this.numRows);

		for (let y = start; y < end; y++) {
			if (this.row(position.y).isNone()) {
				return None;
			}

			const maybeMatch = this.#rows[y].find(q, position.x, direction);
			if (maybeMatch.isSome()) {
				position.x = maybeMatch.unwrap();
				return Some(position);
			}

			if (direction === SearchDirection.Forward) {
				position.y = maxAdd(position.y, 1, this.numRows - 1);
				position.x = 0;
			} else {
				position.y = minSub(position.y, 1, 0);

				console.assert(position.y < this.numRows);

				position.x = this.#rows[position.y].size - 1;
			}
		}

		return None;
	}

	public insert(at: Position, c: string): void {
		if (at.y === this.numRows) {
			this.insertRow(this.numRows, c);
		} else {
			this.#rows[at.y].insertChar(at.x, c);
			this.#rows[at.y].update(None);
		}

		this.dirty = true;
	}

	/**
	 * Insert a new line, splitting and/or creating a new row as needed
	 */
	public insertNewline(at: Position): void {
		if (at.y > this.numRows) {
			return;
		}

		// Just add a simple blank line
		if (at.y === this.numRows) {
			this.#rows.push(Row.default());
			this.dirty = true;
			return;
		}

		// Split the current row, and insert a new
		// row with the leftovers
		const newRow = this.#rows[at.y].split(at.x);
		newRow.update(None);
		this.#rows = arrayInsert(this.#rows, at.y + 1, newRow);

		this.dirty = true;
	}

	/**
	 * Remove a character from the document, merging
	 * adjacent lines if necessary
	 */
	public delete(at: Position): void {
		const len = this.numRows;
		if (at.y >= len) {
			return;
		}

		const maybeRow = this.row(at.y);
		if (maybeRow.isNone()) {
			return;
		}

		const row = maybeRow.unwrap();

		const mergeNextRow = at.x === row.size && at.y + 1 < len;
		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.update(None);

		this.dirty = true;
	}

	public row(i: number): Option<Row> {
		if (i >= this.numRows) {
			return None;
		}

		return Option.from(this.#rows[i]);
	}

	public insertRow(at: number = this.numRows, s: string = ''): void {
		this.#rows = arrayInsert(this.#rows, at, Row.from(s));
		this.#rows[at].update(None);

		this.dirty = true;
	}

	public highlight(searchMatch: Option<string>): void {
		this.#rows.forEach((row) => {
			row.update(searchMatch);
		});
	}

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

	/**
	 * Convert the array of row objects into one string
	 * @private
	 */
	private rowsToString(): string {
		return this.#rows.map((r) => r.toString()).join('\n');
	}
}

export default Document;