/**
 * Copyright (c) 2017 The xterm.js authors. All rights reserved.
 * @license MIT
 */

import type { Terminal, ITerminalAddon, IRenderDimensions } from '@xterm/xterm';
import type { FitAddon as IFitApi } from '@xterm/addon-fit';
import { ViewportConstants } from 'browser/shared/Constants';

interface ITerminalDimensions {
  /**
   * The number of rows in the terminal.
   */
  rows: number;

  /**
   * The number of columns in the terminal.
   */
  cols: number;
}

const enum Constants {
  MINIMUM_COLS = 2,
  MINIMUM_ROWS = 1
}

function getWindow(e: Node): Window {
  if (e?.ownerDocument?.defaultView) {
    return e.ownerDocument.defaultView;
  }

  return window;
}
function _getComputedStyle(el: HTMLElement): CSSStyleDeclaration {
  return getWindow(el).getComputedStyle(el, null);
}

export class FitAddon implements ITerminalAddon, IFitApi {
  private _terminal: Terminal | undefined;

  public activate(terminal: Terminal): void {
    this._terminal = terminal;
  }

  public dispose(): void {}

  public fit(): void {
    const dims = this.proposeDimensions();
    if (!dims || !this._terminal || isNaN(dims.cols) || isNaN(dims.rows)) {
      return;
    }

    this._terminal.resize(dims.cols, dims.rows);
  }

  public proposeDimensions(): ITerminalDimensions | undefined {
    if (!this._terminal) {
      return undefined;
    }

    if (!this._terminal.element || !this._terminal.element.parentElement) {
      return undefined;
    }

    const dims: IRenderDimensions | undefined = this._terminal.dimensions;

    if (!dims || dims.css.cell.width === 0 || dims.css.cell.height === 0) {
      return undefined;
    }

    const showScrollbar = this._terminal.options.scrollbar?.showScrollbar ?? true;
    const scrollbarWidth = (this._terminal.options.scrollback === 0 || !showScrollbar
      ? 0
      : (this._terminal.options.scrollbar?.width ?? ViewportConstants.DEFAULT_SCROLL_BAR_WIDTH));

    const parentElementStyle = _getComputedStyle(this._terminal.element.parentElement);
    const parentElementHeight = Math.max(0, parseInt(parentElementStyle.getPropertyValue('height'), 10) || 0);
    const parentElementWidth = Math.max(0, parseInt(parentElementStyle.getPropertyValue('width'), 10) || 0);
    const elementStyle = _getComputedStyle(this._terminal.element);
    const elementPadding = {
      top: parseInt(elementStyle.getPropertyValue('padding-top'), 10) || 0,
      bottom: parseInt(elementStyle.getPropertyValue('padding-bottom'), 10) || 0,
      right: parseInt(elementStyle.getPropertyValue('padding-right'), 10) || 0,
      left: parseInt(elementStyle.getPropertyValue('padding-left'), 10) || 0
    };
    const elementPaddingVer = elementPadding.top + elementPadding.bottom;
    const elementPaddingHor = elementPadding.right + elementPadding.left;
    const availableHeight = parentElementHeight - elementPaddingVer;
    const availableWidth = parentElementWidth - elementPaddingHor - scrollbarWidth;
    const geometry = {
      cols: Math.max(Constants.MINIMUM_COLS, Math.floor(availableWidth / dims.css.cell.width)),
      rows: Math.max(Constants.MINIMUM_ROWS, Math.floor(availableHeight / dims.css.cell.height))
    };
    return geometry;
  }
}