import { HDRImage } from "./HDRImage";
import { isSafari } from "./browser";

import type { HDRHTMLCanvasElement, CanvasRenderingContext2DHDRSettings, CanvasRenderingContext2DHDR } from "./types/HDRCanvas.d.ts";

/**
 * Gets a `CanvasRenderingContext2DSettings` object configured for HDR.
 * This function detects the browser version to determine the appropriate `colorType` for HDR support.
 *
 * @returns {CanvasRenderingContext2DHDRSettings} An options object for creating an HDR canvas context.
 */
export function getHdrOptions(): CanvasRenderingContext2DHDRSettings {
  const hdrOptions: CanvasRenderingContext2DHDRSettings = {
    colorSpace: HDRImage.DEFAULT_COLORSPACE,
    colorType: "float16",
    toneMapping: { mode: "extended" }
  };
  if (isSafari()) {
    hdrOptions["colorSpace"] = "display-p3";
  }

  return hdrOptions;
}

/**
 * Initializes a given `HTMLCanvasElement` for HDR and returns its 2D rendering context.
 * It first configures the canvas for high dynamic range and then gets the 2D context with HDR options.
 *
 * @param {HDRHTMLCanvasElement} canvas - The canvas element to initialize.
 * @returns {CanvasRenderingContext2DHDR | null} The 2D rendering context, or `null` if the context cannot be created. Can be cast down to `CanvasRenderingContext2D` or `RenderingContext`
 */
export function initHDRCanvas(canvas: HDRHTMLCanvasElement): CanvasRenderingContext2DHDR | null {
  const ctx = canvas.getContext("2d", getHdrOptions());
  return ctx as CanvasRenderingContext2DHDR;
}

/**
 * Patches the `getContext` method of `HTMLCanvasElement` to default to HDR settings.
 * This allows all subsequent calls to `getContext('2d')` to be HDR-enabled without
 * explicitly passing the HDR options.
 *
 * @remarks
 * This function modifies the global `HTMLCanvasElement.prototype` and should be used with caution.
 * Calling it multiple times has no additional effect. Contexts other than `2d` are passed
 * through unmodified.
 */
/* eslint-disable  @typescript-eslint/no-explicit-any */
export function defaultGetContextHDR() {
  const prototype = HTMLCanvasElement.prototype as HDRHTMLCanvasElement;
  if (typeof prototype._getContext === "function") {
    return;
  }
  prototype._getContext = HTMLCanvasElement.prototype.getContext;
  (HTMLCanvasElement.prototype as any).getContext = function (type: string, options?: object) {
    if (type === "2d") {
      if (options !== undefined) {
        options = Object.assign({}, options, getHdrOptions());
      } else {
        options = getHdrOptions();
      }
    }
    return (this as HDRHTMLCanvasElement)._getContext(type, options);
  };
}

/**
 * Resets the `getContext` method of `HTMLCanvasElement` to its original behavior.
 * This reverses the changes made by `defaultGetContextHDR`.
 *
 * @remarks
 * This function only works if `defaultGetContextHDR` has been previously called.
 */
/* eslint-disable  @typescript-eslint/no-explicit-any */
export function resetGetContext() {
  const prototype = HTMLCanvasElement.prototype as HDRHTMLCanvasElement;
  if (typeof prototype._getContext === "function") {
    HTMLCanvasElement.prototype.getContext = prototype._getContext as typeof HTMLCanvasElement.prototype.getContext;
    delete (prototype as any)._getContext;
  }
}