const Constants  = require("./constants.js");
const Commons    = require("./commons.js");
const Cloudevent = require("../../cloudevent.js");
const Spec02     = require("../../specs/spec_0_2.js");

const JSONParser = require("../../formats/json/parser.js");

const {
  isDefinedOrThrow,
  isStringOrObjectOrThrow
} = require("../../utils/fun.js");

const parserByType = {};
parserByType[Constants.MIME_JSON] = new JSONParser();
parserByType[Constants.MIME_OCTET_STREAM] = {
  parse(payload) { return payload; }
};

const allowedContentTypes = [];
allowedContentTypes.push(Constants.MIME_JSON);
allowedContentTypes.push(Constants.MIME_OCTET_STREAM);

const requiredHeaders = [];
requiredHeaders.push(Constants.BINARY_HEADERS_02.TYPE);
requiredHeaders.push(Constants.BINARY_HEADERS_02.SPEC_VERSION);
requiredHeaders.push(Constants.BINARY_HEADERS_02.SOURCE);
requiredHeaders.push(Constants.BINARY_HEADERS_02.ID);

const setterByHeader = {};
setterByHeader[Constants.BINARY_HEADERS_02.TYPE] = {
  name : "type",
  parser : (v) => v
};
setterByHeader[Constants.BINARY_HEADERS_02.SPEC_VERSION] = {
  name : "specversion",
  parser : (v) => "0.2"
};
setterByHeader[Constants.BINARY_HEADERS_02.SOURCE] = {
  name : "source",
  parser: (v) => v
};
setterByHeader[Constants.BINARY_HEADERS_02.ID] = {
  name : "id",
  parser : (v) => v
};
setterByHeader[Constants.BINARY_HEADERS_02.TIME] = {
  name : "time",
  parser : (v) => new Date(Date.parse(v))
};
setterByHeader[Constants.BINARY_HEADERS_02.SCHEMA_URL] = {
  name: "schemaurl",
  parser: (v) => v
};
setterByHeader[Constants.HEADER_CONTENT_TYPE] = {
  name: "contenttype",
  parser: (v) => v
};

function validateArgs(payload, attributes) {

  Array.of(payload)
    .filter((p) => isDefinedOrThrow(p,
              {message: "payload is null or undefined"}))
    .filter((p) => isStringOrObjectOrThrow(p,
              {message: "payload must be an object or a string"}))
    .shift();

  Array.of(attributes)
    .filter((a) => isDefinedOrThrow(a,
                {message: "attributes is null or undefined"}))
    .shift();
}

function Receiver(configuration) {

}

Receiver.prototype.check = function(payload, headers) {
  // Validation Level 0
  validateArgs(payload, headers);

  // Clone and low case all headers names
  var sanityHeaders = Commons.sanityAndClone(headers);

  // Validation Level 1
  if(!allowedContentTypes
      .includes(sanityHeaders[Constants.HEADER_CONTENT_TYPE])){
        throw {
          message: "invalid content type",
          errors: [sanityHeaders[Constants.HEADER_CONTENT_TYPE]]
        };
  }

  requiredHeaders
    .filter((required) => !sanityHeaders[required])
    .forEach((required) => {
      throw {message: "header '" + required + "' not found"};
    });

  if(sanityHeaders[Constants.BINARY_HEADERS_02.SPEC_VERSION] !== "0.2"){
    throw {
      message: "invalid spec version",
      errors: [sanityHeaders[Constants.BINARY_HEADERS_02.SPEC_VERSION]]
    };
  }

  // No erros! Its contains the minimum required attributes
};

Receiver.prototype.parse = function(payload, headers) {
  this.check(payload, headers);

  // Clone and low case all headers names
  var sanityHeaders = Commons.sanityAndClone(headers);

  var processedHeaders = [];
  var cloudevent = new Cloudevent(Spec02);

  // dont worry, check() have seen what was required or not
  Array.from(Object.keys(setterByHeader))
    .filter((header) => sanityHeaders[header])
    .forEach((header) => {
      var setterName = setterByHeader[header].name;
      var parserFun   = setterByHeader[header].parser;

      // invoke the setter function
      cloudevent[setterName](parserFun(sanityHeaders[header]));

      // to use ahead, for extensions processing
      processedHeaders.push(header);
    });

  // Parses the payload
  var parsedPayload =
    parserByType[sanityHeaders[Constants.HEADER_CONTENT_TYPE]]
      .parse(payload);

  // Every unprocessed header can be an extension
  Array.from(Object.keys(sanityHeaders))
  .filter((value) => !processedHeaders.includes(value))
  .filter((value) =>
    value.startsWith(Constants.BINARY_HEADERS_02.EXTENSIONS_PREFIX))
  .map((extension) =>
    extension.substring(Constants.BINARY_HEADERS_02.EXTENSIONS_PREFIX.length)
  ).forEach((extension) =>
    cloudevent.addExtension(extension,
      sanityHeaders[Constants.BINARY_HEADERS_02.EXTENSIONS_PREFIX+extension])
  );

  // Sets the data
  cloudevent.data(parsedPayload);

  // Checks the event spec
  cloudevent.format();

  // return the result
  return cloudevent;
};

module.exports = Receiver;