import defaultValue from "../Core/defaultValue.js";
import defined from "../Core/defined.js";
import DeveloperError from "../Core/DeveloperError.js";
import Appearance from "./Appearance.js";

/**
 * Visualizes a vertex attribute by displaying it as a color for debugging.
 * <p>
 * Components for well-known unit-length vectors, i.e., <code>normal</code>,
 * <code>tangent</code>, and <code>bitangent</code>, are scaled and biased
 * from [-1.0, 1.0] to (-1.0, 1.0).
 * </p>
 *
 * @alias DebugAppearance
 * @constructor
 *
 * @param {object} options Object with the following properties:
 * @param {string} options.attributeName The name of the attribute to visualize.
 * @param {boolean} [options.perInstanceAttribute=false] Boolean that determines whether this attribute is a per-instance geometry attribute.
 * @param {string} [options.glslDatatype='vec3'] The GLSL datatype of the attribute.  Supported datatypes are <code>float</code>, <code>vec2</code>, <code>vec3</code>, and <code>vec4</code>.
 * @param {string} [options.vertexShaderSource] Optional GLSL vertex shader source to override the default vertex shader.
 * @param {string} [options.fragmentShaderSource] Optional GLSL fragment shader source to override the default fragment shader.
 * @param {object} [options.renderState] Optional render state to override the default render state.
 *
 * @exception {DeveloperError} options.glslDatatype must be float, vec2, vec3, or vec4.
 *
 * @example
 * const primitive = new Cesium.Primitive({
 *   geometryInstances : // ...
 *   appearance : new Cesium.DebugAppearance({
 *     attributeName : 'normal'
 *   })
 * });
 */
function DebugAppearance(options) {
  options = defaultValue(options, defaultValue.EMPTY_OBJECT);
  const attributeName = options.attributeName;
  let perInstanceAttribute = options.perInstanceAttribute;

  //>>includeStart('debug', pragmas.debug);
  if (!defined(attributeName)) {
    throw new DeveloperError("options.attributeName is required.");
  }
  //>>includeEnd('debug');

  if (!defined(perInstanceAttribute)) {
    perInstanceAttribute = false;
  }

  let glslDatatype = defaultValue(options.glslDatatype, "vec3");
  const varyingName = `v_${attributeName}`;
  let getColor;

  // Well-known normalized vector attributes in VertexFormat
  if (
    attributeName === "normal" ||
    attributeName === "tangent" ||
    attributeName === "bitangent"
  ) {
    getColor = `vec4 getColor() { return vec4((${varyingName} + vec3(1.0)) * 0.5, 1.0); }\n`;
  } else {
    // All other attributes, both well-known and custom
    if (attributeName === "st") {
      glslDatatype = "vec2";
    }

    switch (glslDatatype) {
      case "float":
        getColor = `vec4 getColor() { return vec4(vec3(${varyingName}), 1.0); }\n`;
        break;
      case "vec2":
        getColor = `vec4 getColor() { return vec4(${varyingName}, 0.0, 1.0); }\n`;
        break;
      case "vec3":
        getColor = `vec4 getColor() { return vec4(${varyingName}, 1.0); }\n`;
        break;
      case "vec4":
        getColor = `vec4 getColor() { return ${varyingName}; }\n`;
        break;
      //>>includeStart('debug', pragmas.debug);
      default:
        throw new DeveloperError(
          "options.glslDatatype must be float, vec2, vec3, or vec4."
        );
      //>>includeEnd('debug');
    }
  }

  const vs =
    `${
      "in vec3 position3DHigh;\n" +
      "in vec3 position3DLow;\n" +
      "in float batchId;\n"
    }${
      perInstanceAttribute ? "" : `in ${glslDatatype} ${attributeName};\n`
    }out ${glslDatatype} ${varyingName};\n` +
    `void main()\n` +
    `{\n` +
    `vec4 p = czm_translateRelativeToEye(position3DHigh, position3DLow);\n${
      perInstanceAttribute
        ? `${varyingName} = czm_batchTable_${attributeName}(batchId);\n`
        : `${varyingName} = ${attributeName};\n`
    }gl_Position = czm_modelViewProjectionRelativeToEye * p;\n` +
    `}`;
  const fs =
    `in ${glslDatatype} ${varyingName};\n${getColor}\n` +
    `void main()\n` +
    `{\n` +
    `out_FragColor = getColor();\n` +
    `}`;

  /**
   * This property is part of the {@link Appearance} interface, but is not
   * used by {@link DebugAppearance} since a fully custom fragment shader is used.
   *
   * @type Material
   *
   * @default undefined
   */
  this.material = undefined;

  /**
   * When <code>true</code>, the geometry is expected to appear translucent.
   *
   * @type {boolean}
   *
   * @default false
   */
  this.translucent = defaultValue(options.translucent, false);

  this._vertexShaderSource = defaultValue(options.vertexShaderSource, vs);
  this._fragmentShaderSource = defaultValue(options.fragmentShaderSource, fs);
  this._renderState = Appearance.getDefaultRenderState(
    false,
    false,
    options.renderState
  );
  this._closed = defaultValue(options.closed, false);

  // Non-derived members

  this._attributeName = attributeName;
  this._glslDatatype = glslDatatype;
}

Object.defineProperties(DebugAppearance.prototype, {
  /**
   * The GLSL source code for the vertex shader.
   *
   * @memberof DebugAppearance.prototype
   *
   * @type {string}
   * @readonly
   */
  vertexShaderSource: {
    get: function () {
      return this._vertexShaderSource;
    },
  },

  /**
   * The GLSL source code for the fragment shader.  The full fragment shader
   * source is built procedurally taking into account the {@link DebugAppearance#material}.
   * Use {@link DebugAppearance#getFragmentShaderSource} to get the full source.
   *
   * @memberof DebugAppearance.prototype
   *
   * @type {string}
   * @readonly
   */
  fragmentShaderSource: {
    get: function () {
      return this._fragmentShaderSource;
    },
  },

  /**
   * The WebGL fixed-function state to use when rendering the geometry.
   *
   * @memberof DebugAppearance.prototype
   *
   * @type {object}
   * @readonly
   */
  renderState: {
    get: function () {
      return this._renderState;
    },
  },

  /**
   * When <code>true</code>, the geometry is expected to be closed.
   *
   * @memberof DebugAppearance.prototype
   *
   * @type {boolean}
   * @readonly
   *
   * @default false
   */
  closed: {
    get: function () {
      return this._closed;
    },
  },

  /**
   * The name of the attribute being visualized.
   *
   * @memberof DebugAppearance.prototype
   *
   * @type {string}
   * @readonly
   */
  attributeName: {
    get: function () {
      return this._attributeName;
    },
  },

  /**
   * The GLSL datatype of the attribute being visualized.
   *
   * @memberof DebugAppearance.prototype
   *
   * @type {string}
   * @readonly
   */
  glslDatatype: {
    get: function () {
      return this._glslDatatype;
    },
  },
});

/**
 * Returns the full GLSL fragment shader source, which for {@link DebugAppearance} is just
 * {@link DebugAppearance#fragmentShaderSource}.
 *
 * @function
 *
 * @returns {string} The full GLSL fragment shader source.
 */
DebugAppearance.prototype.getFragmentShaderSource =
  Appearance.prototype.getFragmentShaderSource;

/**
 * Determines if the geometry is translucent based on {@link DebugAppearance#translucent}.
 *
 * @function
 *
 * @returns {boolean} <code>true</code> if the appearance is translucent.
 */
DebugAppearance.prototype.isTranslucent = Appearance.prototype.isTranslucent;

/**
 * Creates a render state.  This is not the final render state instance; instead,
 * it can contain a subset of render state properties identical to the render state
 * created in the context.
 *
 * @function
 *
 * @returns {object} The render state.
 */
DebugAppearance.prototype.getRenderState = Appearance.prototype.getRenderState;
export default DebugAppearance;