import { GetWindow } from './window.helper';
import { DOCUMENT } from '@angular/common';
import { Inject, Injectable } from '@angular/core';

/**
 * A utility service for working with colors in Angular applications.
 *
 * This service provides methods to retrieve CSS variable values and to lighten or darken colors.
 *
 * @example
 * // Inject the ColorsHelper service and use its methods:
 * constructor(private colorsHelper: ColorsHelper) { }
 *
 * // Or instance a new class
 * const colorsHelper = new ColorsHelper()
 *
 * const mainColor = this.colorsHelper.getCssVariableValue('--main-color');
 * const lighterColor = this.colorsHelper.lightenDarkenColor('#FF5733', 20);
 */
@Injectable({
  providedIn: 'root',
})
export class ColorsHelper {
  /**
   * Initializes a new instance of the `ColorsHelper` class.
   * @constructor
   * @param {Document} document - The injected DOCUMENT to get a reference to the window object in a way that's safe for SSR.
   * @param {GetWindow} getWindow - The injected GetWindow service to get the window object.
   */
  constructor(
    @Inject(DOCUMENT) private document: Document,
    public getWindow: GetWindow
  ) {}

  /**
   * Get the value of a CSS variable.
   *
   * @param {string} variableName - The name of the CSS variable (e.g., '--main-color').
   * @returns {string} The value of the CSS variable or the variableName if not found.
   */
  getCssVariableValue(variableName: string): string {
    if (this.document?.documentElement) {
      const clearVar = variableName?.replace('var(', '')?.replace(')', '')?.trim();
      return (
        this.getWindow.window()?.getComputedStyle(this.document?.documentElement).getPropertyValue(clearVar) ||
        variableName
      );
    }
    return variableName;
  }

  /**
   * Lighten or darken a color by a specified amount.
   *
   * @param {string} color - The color to be adjusted (e.g., '#FF5733' or 'var(--main-color)').
   * @param {number} amount - The amount to lighten or darken the color (positive for lighten, negative for darken).
   * @returns {string} The adjusted color in hexadecimal format (e.g., '#FF5733').
   */
  lightenDarkenColor(color: string, amount: number): string {
    color = color?.trim();
    let colorWithoutHash = color?.replace('var(', '')?.replace(')', '')?.replace('#', '');
    if (colorWithoutHash?.length === 3) {
      colorWithoutHash = colorWithoutHash
        .split('')
        .map(c => `${c}${c}`)
        .join('');
    }

    const isHexColor = (value: string): boolean => {
      const hexColorRegex = /^([a-fA-F0-9]{3}|[a-fA-F0-9]{6})$/;
      return hexColorRegex.test(value);
    };

    if (!isHexColor(colorWithoutHash)) {
      return colorWithoutHash;
    }

    const getColorChannel = (substring: string): string => {
      let colorChannel = Math.max(Math.min(255, parseInt(substring, 16) + amount), 0).toString(16);
      if (colorChannel?.length < 2) {
        colorChannel = `0${colorChannel}`;
      }
      return colorChannel;
    };

    const colorChannelRed = getColorChannel(colorWithoutHash?.substring(0, 2));
    const colorChannelGreen = getColorChannel(colorWithoutHash?.substring(2, 4));
    const colorChannelBlue = getColorChannel(colorWithoutHash?.substring(4, 6));

    return `#${colorChannelRed}${colorChannelGreen}${colorChannelBlue}`;
  }
}