import Row from './row.ts';
import { arrayInsert } from './fns.ts';
import { getRuntime } from './runtime.ts';
import { Position, SearchDirection } from './types.ts';
import { KeyCommand } from './ansi.ts';

class Search {
	public lastMatch: number = -1;
	public current: number = -1;
	public direction: SearchDirection = SearchDirection.Forward;

	public parseInput(key: string) {
		switch (key) {
			case KeyCommand.ArrowRight:
			case KeyCommand.ArrowDown:
				this.direction = SearchDirection.Forward;
				break;

			case KeyCommand.ArrowLeft:
			case KeyCommand.ArrowUp:
				this.direction = SearchDirection.Backward;
				break;

			default:
				this.lastMatch = -1;
				this.direction = SearchDirection.Forward;
		}

		if (this.lastMatch === -1) {
			this.direction = SearchDirection.Forward;
		}

		this.current = this.lastMatch;
	}

	public getNextRow(rowCount: number): number {
		this.current += this.direction;
		if (this.current === -1) {
			this.current = rowCount - 1;
		} else if (this.current === rowCount) {
			this.current = 0;
		}

		return this.current;
	}
}

export class Document {
	#rows: Row[];
	#search: Search;

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

	private constructor() {
		this.#rows = [];
		this.#search = new Search();
		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) {
		const { file } = await getRuntime();

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

		this.dirty = false;
	}

	public resetFind() {
		this.#search = new Search();
	}

	public find(
		q: string,
		key: string,
	): Position | null {
		this.#search.parseInput(key);

		let i = 0;
		for (; i < this.numRows; i++) {
			const current = this.#search.getNextRow(this.numRows);

			const possible = this.#rows[current].find(q);
			if (possible !== null) {
				this.#search.lastMatch = current;
				return Position.at(possible, current);
			}
		}

		return null;
	}

	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].updateRender();
		}

		this.dirty = true;
	}

	public insertNewline(at: Position): void {
		if (at.y > this.numRows) {
			return;
		}

		if (at.y === this.numRows) {
			this.#rows.push(Row.default());
			return;
		}

		const newRow = this.#rows[at.y].split(at.x);
		newRow.updateRender();
		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 row = this.row(at.y)!;
		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.updateRender();

		this.dirty = true;
	}

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

	public insertRow(at: number = this.numRows, s: string = ''): void {
		this.#rows = arrayInsert(this.#rows, at, Row.from(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);
	}

	/**
	 * 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;