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

import { IColorManager, IColorSet, IColorContrastCache } from 'browser/Types';
import { ITheme } from 'common/services/Services';
import { channels, color, css } from 'common/Color';
import { ColorContrastCache } from 'browser/ColorContrastCache';
import { ColorIndex, IColor } from 'common/Types';


interface IRestoreColorSet {
  foreground: IColor;
  background: IColor;
  cursor: IColor;
  ansi: IColor[];
}


const DEFAULT_FOREGROUND = css.toColor('#ffffff');
const DEFAULT_BACKGROUND = css.toColor('#000000');
const DEFAULT_CURSOR = css.toColor('#ffffff');
const DEFAULT_CURSOR_ACCENT = css.toColor('#000000');
const DEFAULT_SELECTION = {
  css: 'rgba(255, 255, 255, 0.3)',
  rgba: 0xFFFFFF4D
};

// An IIFE to generate DEFAULT_ANSI_COLORS.
export const DEFAULT_ANSI_COLORS = Object.freeze((() => {
  const colors = [
    // dark:
    css.toColor('#2e3436'),
    css.toColor('#cc0000'),
    css.toColor('#4e9a06'),
    css.toColor('#c4a000'),
    css.toColor('#3465a4'),
    css.toColor('#75507b'),
    css.toColor('#06989a'),
    css.toColor('#d3d7cf'),
    // bright:
    css.toColor('#555753'),
    css.toColor('#ef2929'),
    css.toColor('#8ae234'),
    css.toColor('#fce94f'),
    css.toColor('#729fcf'),
    css.toColor('#ad7fa8'),
    css.toColor('#34e2e2'),
    css.toColor('#eeeeec')
  ];

  // Fill in the remaining 240 ANSI colors.
  // Generate colors (16-231)
  const v = [0x00, 0x5f, 0x87, 0xaf, 0xd7, 0xff];
  for (let i = 0; i < 216; i++) {
    const r = v[(i / 36) % 6 | 0];
    const g = v[(i / 6) % 6 | 0];
    const b = v[i % 6];
    colors.push({
      css: channels.toCss(r, g, b),
      rgba: channels.toRgba(r, g, b)
    });
  }

  // Generate greys (232-255)
  for (let i = 0; i < 24; i++) {
    const c = 8 + i * 10;
    colors.push({
      css: channels.toCss(c, c, c),
      rgba: channels.toRgba(c, c, c)
    });
  }

  return colors;
})());

/**
 * Manages the source of truth for a terminal's colors.
 */
export class ColorManager implements IColorManager {
  public colors: IColorSet;
  private _ctx: CanvasRenderingContext2D;
  private _litmusColor: CanvasGradient;
  private _contrastCache: IColorContrastCache;
  private _restoreColors!: IRestoreColorSet;

  constructor(document: Document, public allowTransparency: boolean) {
    const canvas = document.createElement('canvas');
    canvas.width = 1;
    canvas.height = 1;
    const ctx = canvas.getContext('2d');
    if (!ctx) {
      throw new Error('Could not get rendering context');
    }
    this._ctx = ctx;
    this._ctx.globalCompositeOperation = 'copy';
    this._litmusColor = this._ctx.createLinearGradient(0, 0, 1, 1);
    this._contrastCache = new ColorContrastCache();
    this.colors = {
      foreground: DEFAULT_FOREGROUND,
      background: DEFAULT_BACKGROUND,
      cursor: DEFAULT_CURSOR,
      cursorAccent: DEFAULT_CURSOR_ACCENT,
      selectionTransparent: DEFAULT_SELECTION,
      selectionOpaque: color.blend(DEFAULT_BACKGROUND, DEFAULT_SELECTION),
      selectionForeground: undefined,
      ansi: DEFAULT_ANSI_COLORS.slice(),
      contrastCache: this._contrastCache
    };
    this._updateRestoreColors();
  }

  public onOptionsChange(key: string): void {
    if (key === 'minimumContrastRatio') {
      this._contrastCache.clear();
    }
  }

  /**
   * Sets the terminal's theme.
   * @param theme The  theme to use. If a partial theme is provided then default
   * colors will be used where colors are not defined.
   */
  public setTheme(theme: ITheme = {}): void {
    this.colors.foreground = this._parseColor(theme.foreground, DEFAULT_FOREGROUND);
    this.colors.background = this._parseColor(theme.background, DEFAULT_BACKGROUND);
    this.colors.cursor = this._parseColor(theme.cursor, DEFAULT_CURSOR, true);
    this.colors.cursorAccent = this._parseColor(theme.cursorAccent, DEFAULT_CURSOR_ACCENT, true);
    this.colors.selectionTransparent = this._parseColor(theme.selection, DEFAULT_SELECTION, true);
    this.colors.selectionOpaque = color.blend(this.colors.background, this.colors.selectionTransparent);
    const nullColor: IColor = {
      css: '',
      rgba: 0
    };
    this.colors.selectionForeground = theme.selectionForeground ? this._parseColor(theme.selectionForeground, nullColor) : undefined;
    if (this.colors.selectionForeground === nullColor) {
      this.colors.selectionForeground = undefined;
    }

    /**
     * If selection color is opaque, blend it with background with 0.3 opacity
     * Issue #2737
     */
    if (color.isOpaque(this.colors.selectionTransparent)) {
      const opacity = 0.3;
      this.colors.selectionTransparent = color.opacity(this.colors.selectionTransparent, opacity);
    }
    this.colors.ansi[0] = this._parseColor(theme.black, DEFAULT_ANSI_COLORS[0]);
    this.colors.ansi[1] = this._parseColor(theme.red, DEFAULT_ANSI_COLORS[1]);
    this.colors.ansi[2] = this._parseColor(theme.green, DEFAULT_ANSI_COLORS[2]);
    this.colors.ansi[3] = this._parseColor(theme.yellow, DEFAULT_ANSI_COLORS[3]);
    this.colors.ansi[4] = this._parseColor(theme.blue, DEFAULT_ANSI_COLORS[4]);
    this.colors.ansi[5] = this._parseColor(theme.magenta, DEFAULT_ANSI_COLORS[5]);
    this.colors.ansi[6] = this._parseColor(theme.cyan, DEFAULT_ANSI_COLORS[6]);
    this.colors.ansi[7] = this._parseColor(theme.white, DEFAULT_ANSI_COLORS[7]);
    this.colors.ansi[8] = this._parseColor(theme.brightBlack, DEFAULT_ANSI_COLORS[8]);
    this.colors.ansi[9] = this._parseColor(theme.brightRed, DEFAULT_ANSI_COLORS[9]);
    this.colors.ansi[10] = this._parseColor(theme.brightGreen, DEFAULT_ANSI_COLORS[10]);
    this.colors.ansi[11] = this._parseColor(theme.brightYellow, DEFAULT_ANSI_COLORS[11]);
    this.colors.ansi[12] = this._parseColor(theme.brightBlue, DEFAULT_ANSI_COLORS[12]);
    this.colors.ansi[13] = this._parseColor(theme.brightMagenta, DEFAULT_ANSI_COLORS[13]);
    this.colors.ansi[14] = this._parseColor(theme.brightCyan, DEFAULT_ANSI_COLORS[14]);
    this.colors.ansi[15] = this._parseColor(theme.brightWhite, DEFAULT_ANSI_COLORS[15]);
    // Clear our the cache
    this._contrastCache.clear();
    this._updateRestoreColors();
  }

  public restoreColor(slot?: ColorIndex): void {
    // unset slot restores all ansi colors
    if (slot === undefined) {
      for (let i = 0; i < this._restoreColors.ansi.length; ++i) {
        this.colors.ansi[i] = this._restoreColors.ansi[i];
      }
      return;
    }
    switch (slot) {
      case ColorIndex.FOREGROUND:
        this.colors.foreground = this._restoreColors.foreground;
        break;
      case ColorIndex.BACKGROUND:
        this.colors.background = this._restoreColors.background;
        break;
      case ColorIndex.CURSOR:
        this.colors.cursor = this._restoreColors.cursor;
        break;
      default:
        this.colors.ansi[slot] = this._restoreColors.ansi[slot];
    }
  }

  private _updateRestoreColors(): void {
    this._restoreColors = {
      foreground: this.colors.foreground,
      background: this.colors.background,
      cursor: this.colors.cursor,
      ansi: this.colors.ansi.slice()
    };
  }

  private _parseColor(
    css: string | undefined,
    fallback: IColor,
    allowTransparency: boolean = this.allowTransparency
  ): IColor {
    if (css === undefined) {
      return fallback;
    }

    // If parsing the value results in failure, then it must be ignored, and the attribute must
    // retain its previous value.
    // -- https://html.spec.whatwg.org/multipage/canvas.html#fill-and-stroke-styles
    this._ctx.fillStyle = this._litmusColor;
    this._ctx.fillStyle = css;
    if (typeof this._ctx.fillStyle !== 'string') {
      console.warn(`Color: ${css} is invalid using fallback ${fallback.css}`);
      return fallback;
    }

    this._ctx.fillRect(0, 0, 1, 1);
    const data = this._ctx.getImageData(0, 0, 1, 1).data;

    // Check if the printed color was transparent
    if (data[3] !== 0xFF) {
      if (!allowTransparency) {
        // Ideally we'd just ignore the alpha channel, but...
        //
        // Browsers may not give back exactly the same RGB values we put in, because most/all
        // convert the color to a pre-multiplied representation. getImageData converts that back to
        // a un-premultipled representation, but the precision loss may make the RGB channels unuable
        // on their own.
        //
        // E.g. In Chrome #12345610 turns into #10305010, and in the extreme case, 0xFFFFFF00 turns
        // into 0x00000000.
        //
        // "Note: Due to the lossy nature of converting to and from premultiplied alpha color values,
        // pixels that have just been set using putImageData() might be returned to an equivalent
        // getImageData() as different values."
        // -- https://html.spec.whatwg.org/multipage/canvas.html#pixel-manipulation
        //
        // So let's just use the fallback color in this case instead.
        console.warn(
          `Color: ${css} is using transparency, but allowTransparency is false. ` +
          `Using fallback ${fallback.css}.`
        );
        return fallback;
      }

      // https://html.spec.whatwg.org/multipage/canvas.html#serialisation-of-a-color
      // the color value has alpha less than 1.0, and the string is the color value in the CSS rgba()
      const [r, g, b, a] = this._ctx.fillStyle.substring(5, this._ctx.fillStyle.length - 1).split(',').map(component => Number(component));
      const alpha = Math.round(a * 255);
      const rgba: number = channels.toRgba(r, g, b, alpha);
      return {
        rgba,
        css
      };
    }

    return {
      // https://html.spec.whatwg.org/multipage/canvas.html#serialisation-of-a-color
      // if it has alpha equal to 1.0, then the string is a lowercase six-digit hex value, prefixed with a "#" character
      css: this._ctx.fillStyle,
      rgba: channels.toRgba(data[0], data[1], data[2], data[3])
    };
  }
}