import os from 'os';
import chalk from 'chalk';

/**
 * string and color to be passed to terminal
 */
export type TerminalLine = {
  renderString: string;
  color: string;
};

const ESC = '\u001b';
const BUFFER_LENGTH = 10;

const cursorUp = (n: number): string => {
  const dy = typeof n === 'number' ? n : 1;
  return dy > 0 ? `${ESC}[${dy}A` : '';
};

const clearLine = (): string => `${ESC}[K`;
const SHOW_CURSOR = '\x1b[?25h';
const HIDE_CURSOR = '\x1b[?25l';

const getColoredLine = (line: string, color: string): string => {
  if (color) {
    return chalk.keyword(color)(line);
  }
  return line;
};

/**
 * Amplify Terminal instance (Re writable block)
 */
export class AmplifyTerminal {
  private lastHeight: number;
  private trailingEmptyLines: number;
  private readonly stream: NodeJS.WriteStream;

  constructor() {
    this.lastHeight = 0;
    this.trailingEmptyLines = 0;
    this.stream = process.stdout;
  }

  /**
   * Checks if the environment is tty
   */
  isTTY(): boolean {
    return this.stream.isTTY;
  }

  /**
   * Width of terminal
   */
  private get width(): number {
    return this.stream.columns;
  }

  /**
   * Height of last printed block
   */
  public getLastHeight(): number {
    return this.lastHeight;
  }

  /**
   * Height of terminal
   */
  private get height(): number {
    return this.stream.rows;
  }

  /**
   * Write array of lines into block.
   */
  public writeLines(lines: TerminalLine[]): void {
    // Go back to beginning of last written block
    this.stream.write(cursorUp(this.lastHeight));

    lines.forEach((line) => {
      // Truncating to width-2 of terminal
      const { renderString, color } = line;
      let truncatedLine = renderString.substring(0, Math.min(renderString.length, this.width - BUFFER_LENGTH));
      if (truncatedLine.length) {
        truncatedLine = getColoredLine(truncatedLine, color);
      }
      this.stream.write(`${clearLine()}${truncatedLine}${os.EOL}`);
    });

    this.trailingEmptyLines = Math.max(0, this.lastHeight - lines.length);

    // Clear trailing lines if last written block has more height.
    for (let i = 0; i < this.trailingEmptyLines; i++) {
      this.stream.write(`${clearLine()}${os.EOL}`);
    }
    this.lastHeight = lines.length;
  }

  /**
   * Hide/Show cursor. Only for a tty console.
   */
  public cursor(enabled: boolean): void {
    if (!this.isTTY()) {
      return;
    }
    if (enabled) {
      this.stream.write(SHOW_CURSOR);
    } else {
      this.stream.write(HIDE_CURSOR);
    }
  }

  /**
   * Write a new line
   */
  public newLine(): void {
    this.stream.write(os.EOL);
  }
}