import defined from "../Core/defined.js";
import DrawCommand from "../Renderer/DrawCommand.js";
import RenderState from "../Renderer/RenderState.js";
import ShaderSource from "../Renderer/ShaderSource.js";

/**
 * @private
 */
function DerivedCommand() {}

const fragDepthRegex = /\bgl_FragDepthEXT\b/;
const discardRegex = /\bdiscard\b/;

function getDepthOnlyShaderProgram(context, shaderProgram) {
  let shader = context.shaderCache.getDerivedShaderProgram(
    shaderProgram,
    "depthOnly"
  );
  if (!defined(shader)) {
    const attributeLocations = shaderProgram._attributeLocations;
    let fs = shaderProgram.fragmentShaderSource;

    let i;
    let writesDepthOrDiscards = false;
    const sources = fs.sources;
    let length = sources.length;
    for (i = 0; i < length; ++i) {
      if (fragDepthRegex.test(sources[i]) || discardRegex.test(sources[i])) {
        writesDepthOrDiscards = true;
        break;
      }
    }

    let usesLogDepth = false;
    const defines = fs.defines;
    length = defines.length;
    for (i = 0; i < length; ++i) {
      if (defines[i] === "LOG_DEPTH") {
        usesLogDepth = true;
        break;
      }
    }

    let source;
    if (!writesDepthOrDiscards && !usesLogDepth) {
      source =
        "void main() \n" + "{ \n" + "    gl_FragColor = vec4(1.0); \n" + "} \n";
      fs = new ShaderSource({
        sources: [source],
      });
    } else if (!writesDepthOrDiscards && usesLogDepth) {
      source =
        "#ifdef GL_EXT_frag_depth \n" +
        "#extension GL_EXT_frag_depth : enable \n" +
        "#endif \n\n" +
        "void main() \n" +
        "{ \n" +
        "    gl_FragColor = vec4(1.0); \n" +
        "    czm_writeLogDepth(); \n" +
        "} \n";
      fs = new ShaderSource({
        defines: ["LOG_DEPTH"],
        sources: [source],
      });
    }

    shader = context.shaderCache.createDerivedShaderProgram(
      shaderProgram,
      "depthOnly",
      {
        vertexShaderSource: shaderProgram.vertexShaderSource,
        fragmentShaderSource: fs,
        attributeLocations: attributeLocations,
      }
    );
  }

  return shader;
}

function getDepthOnlyRenderState(scene, renderState) {
  const cache = scene._depthOnlyRenderStateCache;
  let depthOnlyState = cache[renderState.id];
  if (!defined(depthOnlyState)) {
    const rs = RenderState.getState(renderState);
    rs.depthMask = true;
    rs.colorMask = {
      red: false,
      green: false,
      blue: false,
      alpha: false,
    };

    depthOnlyState = RenderState.fromCache(rs);
    cache[renderState.id] = depthOnlyState;
  }

  return depthOnlyState;
}

DerivedCommand.createDepthOnlyDerivedCommand = function (
  scene,
  command,
  context,
  result
) {
  // For a depth only pass, we bind a framebuffer with only a depth attachment (no color attachments),
  // do not write color, and write depth. If the fragment shader doesn't modify the fragment depth
  // or discard, the driver can replace the fragment shader with a pass-through shader. We're unsure if this
  // actually happens so we modify the shader to use a pass-through fragment shader.

  if (!defined(result)) {
    result = {};
  }

  let shader;
  let renderState;
  if (defined(result.depthOnlyCommand)) {
    shader = result.depthOnlyCommand.shaderProgram;
    renderState = result.depthOnlyCommand.renderState;
  }

  result.depthOnlyCommand = DrawCommand.shallowClone(
    command,
    result.depthOnlyCommand
  );

  if (!defined(shader) || result.shaderProgramId !== command.shaderProgram.id) {
    result.depthOnlyCommand.shaderProgram = getDepthOnlyShaderProgram(
      context,
      command.shaderProgram
    );
    result.depthOnlyCommand.renderState = getDepthOnlyRenderState(
      scene,
      command.renderState
    );
    result.shaderProgramId = command.shaderProgram.id;
  } else {
    result.depthOnlyCommand.shaderProgram = shader;
    result.depthOnlyCommand.renderState = renderState;
  }

  return result;
};

const writeLogDepthRegex = /\s+czm_writeLogDepth\(/;
const vertexlogDepthRegex = /\s+czm_vertexLogDepth\(/;
const extensionRegex = /\s*#extension\s+GL_EXT_frag_depth\s*:\s*enable/;

function getLogDepthShaderProgram(context, shaderProgram) {
  let shader = context.shaderCache.getDerivedShaderProgram(
    shaderProgram,
    "logDepth"
  );
  if (!defined(shader)) {
    const attributeLocations = shaderProgram._attributeLocations;
    const vs = shaderProgram.vertexShaderSource.clone();
    const fs = shaderProgram.fragmentShaderSource.clone();

    vs.defines = defined(vs.defines) ? vs.defines.slice(0) : [];
    vs.defines.push("LOG_DEPTH");
    fs.defines = defined(fs.defines) ? fs.defines.slice(0) : [];
    fs.defines.push("LOG_DEPTH");

    let i;
    let logMain;
    let writesLogDepth = false;
    let sources = vs.sources;
    let length = sources.length;
    for (i = 0; i < length; ++i) {
      if (vertexlogDepthRegex.test(sources[i])) {
        writesLogDepth = true;
        break;
      }
    }

    if (!writesLogDepth) {
      for (i = 0; i < length; ++i) {
        sources[i] = ShaderSource.replaceMain(sources[i], "czm_log_depth_main");
      }

      logMain =
        "\n\n" +
        "void main() \n" +
        "{ \n" +
        "    czm_log_depth_main(); \n" +
        "    czm_vertexLogDepth(); \n" +
        "} \n";
      sources.push(logMain);
    }

    sources = fs.sources;
    length = sources.length;

    writesLogDepth = false;
    for (i = 0; i < length; ++i) {
      if (writeLogDepthRegex.test(sources[i])) {
        writesLogDepth = true;
      }
    }
    // This define indicates that a log depth value is written by the shader but doesn't use czm_writeLogDepth.
    if (fs.defines.indexOf("LOG_DEPTH_WRITE") !== -1) {
      writesLogDepth = true;
    }

    let addExtension = true;
    for (i = 0; i < length; ++i) {
      if (extensionRegex.test(sources[i])) {
        addExtension = false;
      }
    }

    let logSource = "";
    if (addExtension) {
      logSource +=
        "#ifdef GL_EXT_frag_depth \n" +
        "#extension GL_EXT_frag_depth : enable \n" +
        "#endif \n\n";
    }

    if (!writesLogDepth) {
      for (i = 0; i < length; i++) {
        sources[i] = ShaderSource.replaceMain(sources[i], "czm_log_depth_main");
      }

      logSource +=
        "\n" +
        "void main() \n" +
        "{ \n" +
        "    czm_log_depth_main(); \n" +
        "    czm_writeLogDepth(); \n" +
        "} \n";
    }

    sources.push(logSource);

    shader = context.shaderCache.createDerivedShaderProgram(
      shaderProgram,
      "logDepth",
      {
        vertexShaderSource: vs,
        fragmentShaderSource: fs,
        attributeLocations: attributeLocations,
      }
    );
  }

  return shader;
}

DerivedCommand.createLogDepthCommand = function (command, context, result) {
  if (!defined(result)) {
    result = {};
  }

  let shader;
  if (defined(result.command)) {
    shader = result.command.shaderProgram;
  }

  result.command = DrawCommand.shallowClone(command, result.command);

  if (!defined(shader) || result.shaderProgramId !== command.shaderProgram.id) {
    result.command.shaderProgram = getLogDepthShaderProgram(
      context,
      command.shaderProgram
    );
    result.shaderProgramId = command.shaderProgram.id;
  } else {
    result.command.shaderProgram = shader;
  }

  return result;
};

function getPickShaderProgram(context, shaderProgram, pickId) {
  let shader = context.shaderCache.getDerivedShaderProgram(
    shaderProgram,
    "pick"
  );
  if (!defined(shader)) {
    const attributeLocations = shaderProgram._attributeLocations;
    let fs = shaderProgram.fragmentShaderSource;

    const sources = fs.sources;
    const length = sources.length;

    const newMain =
      `${
        "void main() \n" +
        "{ \n" +
        "    czm_non_pick_main(); \n" +
        "    if (gl_FragColor.a == 0.0) { \n" +
        "        discard; \n" +
        "    } \n" +
        "    gl_FragColor = "
      }${pickId}; \n` + `} \n`;
    const newSources = new Array(length + 1);
    for (let i = 0; i < length; ++i) {
      newSources[i] = ShaderSource.replaceMain(sources[i], "czm_non_pick_main");
    }
    newSources[length] = newMain;
    fs = new ShaderSource({
      sources: newSources,
      defines: fs.defines,
    });
    shader = context.shaderCache.createDerivedShaderProgram(
      shaderProgram,
      "pick",
      {
        vertexShaderSource: shaderProgram.vertexShaderSource,
        fragmentShaderSource: fs,
        attributeLocations: attributeLocations,
      }
    );
  }

  return shader;
}

function getPickRenderState(scene, renderState) {
  const cache = scene.picking.pickRenderStateCache;
  let pickState = cache[renderState.id];
  if (!defined(pickState)) {
    const rs = RenderState.getState(renderState);
    rs.blending.enabled = false;

    // Turns on depth writing for opaque and translucent passes
    // Overlapping translucent geometry on the globe surface may exhibit z-fighting
    // during the pick pass which may not match the rendered scene. Once
    // terrain is on by default and ground primitives are used instead
    // this will become less of a problem.
    rs.depthMask = true;

    pickState = RenderState.fromCache(rs);
    cache[renderState.id] = pickState;
  }

  return pickState;
}

DerivedCommand.createPickDerivedCommand = function (
  scene,
  command,
  context,
  result
) {
  if (!defined(result)) {
    result = {};
  }

  let shader;
  let renderState;
  if (defined(result.pickCommand)) {
    shader = result.pickCommand.shaderProgram;
    renderState = result.pickCommand.renderState;
  }

  result.pickCommand = DrawCommand.shallowClone(command, result.pickCommand);

  if (!defined(shader) || result.shaderProgramId !== command.shaderProgram.id) {
    result.pickCommand.shaderProgram = getPickShaderProgram(
      context,
      command.shaderProgram,
      command.pickId
    );
    result.pickCommand.renderState = getPickRenderState(
      scene,
      command.renderState
    );
    result.shaderProgramId = command.shaderProgram.id;
  } else {
    result.pickCommand.shaderProgram = shader;
    result.pickCommand.renderState = renderState;
  }

  return result;
};

function getHdrShaderProgram(context, shaderProgram) {
  let shader = context.shaderCache.getDerivedShaderProgram(
    shaderProgram,
    "HDR"
  );
  if (!defined(shader)) {
    const attributeLocations = shaderProgram._attributeLocations;
    const vs = shaderProgram.vertexShaderSource.clone();
    const fs = shaderProgram.fragmentShaderSource.clone();

    vs.defines = defined(vs.defines) ? vs.defines.slice(0) : [];
    vs.defines.push("HDR");
    fs.defines = defined(fs.defines) ? fs.defines.slice(0) : [];
    fs.defines.push("HDR");

    shader = context.shaderCache.createDerivedShaderProgram(
      shaderProgram,
      "HDR",
      {
        vertexShaderSource: vs,
        fragmentShaderSource: fs,
        attributeLocations: attributeLocations,
      }
    );
  }

  return shader;
}

DerivedCommand.createHdrCommand = function (command, context, result) {
  if (!defined(result)) {
    result = {};
  }

  let shader;
  if (defined(result.command)) {
    shader = result.command.shaderProgram;
  }

  result.command = DrawCommand.shallowClone(command, result.command);

  if (!defined(shader) || result.shaderProgramId !== command.shaderProgram.id) {
    result.command.shaderProgram = getHdrShaderProgram(
      context,
      command.shaderProgram
    );
    result.shaderProgramId = command.shaderProgram.id;
  } else {
    result.command.shaderProgram = shader;
  }

  return result;
};
export default DerivedCommand;