"use strict";

/**
 * Retrieve the datastream ID that corresponds to a particular building
 * @param {Number | String} buildingNumber Integer representing the building ID
 * @param {String} phenomenon String representing the phenomenon of interest
 * @param {String} samplingRate String representing the sampling rate of the observations
 * @returns {Number} Datastream corresponding to the input building
 */
const getDatastreamIdFromBuildingNumber = function (
  buildingNumber,
  phenomenon,
  samplingRate
) {
  const buildingToDatastreamMapping = {
    101: {
      vl: { "15min": "69", "60min": "75" },
      rl: { "15min": "81", "60min": "87" },

      // These Datastreams do not yet have Observations
      // flow: { "15min": "93", "60min": "99" },
      // power: { "15min": "105", "60min": "111" },
      // energy: { "15min": "117", "60min": "123" },
      // energy_verb: { "15min": "129", "60min": "135" },
    },

    102: {
      vl: { "15min": "70", "60min": "76" },
      rl: { "15min": "82", "60min": "88" },

      // These Datastreams do not yet have Observations
      // flow: { "15min": "94", "60min": "100" },
      // power: { "15min": "106", "60min": "112" },
      // energy: { "15min": "118", "60min": "124" },
      // energy_verb: { "15min": "130", "60min": "136" },
    },

    107: {
      vl: { "15min": "71", "60min": "77" },
      rl: { "15min": "83", "60min": "89" },

      // These Datastreams do not yet have Observations
      // flow: { "15min": "95", "60min": "101" },
      // power: { "15min": "107", "60min": "113" },
      // energy: { "15min": "119", "60min": "125" },
      // energy_verb: { "15min": "131", "60min": "137" },
    },

    "112, 118": {
      vl: { "15min": "72", "60min": "78" },
      rl: { "15min": "84", "60min": "90" },

      // These Datastreams do not yet have Observations
      // flow: { "15min": "96", "60min": "102" },
      // power: { "15min": "108", "60min": "114" },
      // energy: { "15min": "120", "60min": "126" },
      // energy_verb: { "15min": "132", "60min": "138" },
    },

    125: {
      vl: { "15min": "73", "60min": "79" },
      rl: { "15min": "85", "60min": "91" },

      // These Datastreams do not yet have Observations
      // flow: { "15min": "97", "60min": "103" },
      // power: { "15min": "109", "60min": "115" },
      // energy: { "15min": "121", "60min": "127" },
      // energy_verb: { "15min": "133", "60min": "139" },
    },

    225: {
      vl: { "15min": "74", "60min": "80" },
      rl: { "15min": "86", "60min": "92" },
      flow: { "15min": "98", "60min": "104" },
      power: { "15min": "110", "60min": "116" },
      energy: { "15min": "122", "60min": "128" },
      energy_verb: { "15min": "134", "60min": "140" },
    },

    weather_station_521: {
      outside_temp: { "15min": "141", "60min": "142" },
    },
  };

  if (
    buildingToDatastreamMapping?.[buildingNumber]?.[phenomenon]?.[
      samplingRate
    ] === undefined
  )
    return;

  return Number(
    buildingToDatastreamMapping[buildingNumber][phenomenon][samplingRate]
  );
};

/**
 * Create URL to fetch the details of single Datastream
 * @param {String} baseUrl Base URL of the STA server
 * @param {Number} datastreamID Integer representing the Datastream ID
 * @returns {String} URL string for fetching a single Datastream
 */
const createDatastreamUrl = function (baseUrl, datastreamID) {
  if (!datastreamID) return;
  return `${baseUrl}/Datastreams(${datastreamID})`;
};

/**
 * Create URL to fetch Observations
 * @param {String} baseUrl Base URL of the STA server
 * @param {Number} datastreamID Integer representing the Datastream ID
 * @returns {String} URL string for fetching Observations
 */
const createObservationsUrl = function (baseUrl, datastreamID) {
  if (!datastreamID) return;
  return `${baseUrl}/Datastreams(${datastreamID})/Observations`;
};

/**
 * Perform a GET request using the Axios library
 * @param {String} urlObservations A URL that fetches Observations from an STA instance
 * @param {Object} urlParamObj The URL parameters to be sent together with the GET request
 * @returns {Promise} A promise that contains the first page of results when fulfilled
 */
const performGetRequestUsingAxios = function (urlObservations, urlParamObj) {
  return axios.get(urlObservations, {
    params: urlParamObj,
  });
};

/**
 * Retrieve the metadata for a single datastream
 * @async
 * @param {String} urlDatastream A URL that fetches a Datastream from an STA instance
 * @returns {Promise} A promise that contains a metadata object for a Datastream when fulfilled
 */
const getMetadataFromSingleDatastream = async function (urlDatastream) {
  try {
    // Extract properties of interest
    const {
      data: { description, name, unitOfMeasurement },
    } = await performGetRequestUsingAxios(urlDatastream);

    return { description, name, unitOfMeasurement };
  } catch (err) {
    console.error(err);
  }
};

/**
 * Retrieve metadata from multiple datastreams
 * @async
 * @param {Array} datastreamsUrlArr An array that contains N Datastream URL strings
 * @returns {Promise} A promise that contains an array of N Datastream metadata objects when fulfilled
 */
const getMetadataFromMultipleDatastreams = async function (datastreamsUrlArr) {
  try {
    // Array to store our final result
    const datastreamMetadataArr = [];

    // Use for/of loop - we need to maintain the order of execution of the async operations
    for (const datastreamUrl of datastreamsUrlArr) {
      // Metadata from a single Datastream
      const datastreamMetadata = await getMetadataFromSingleDatastream(
        datastreamUrl
      );
      datastreamMetadataArr.push(datastreamMetadata);
    }

    return datastreamMetadataArr;
  } catch (err) {
    console.error(err);
  }
};

/**
 * Match the unitOfMeasurement's string representation of a symbol to an actual symbol, where necessary
 * @param {String} unitOfMeasurementSymbolString String representation of the unitOfMeasurement's symbol
 * @returns {String} The unitOfMeasurement's symbol
 */
const matchUnitOfMeasurementSymbolStringToSymbol = function (
  unitOfMeasurementSymbolString
) {
  const unicodeCodePointDegreeSymbol = "\u00B0";
  const unicodeCodePointSuperscriptThree = "\u00B3";

  if (unitOfMeasurementSymbolString === "degC")
    return `${unicodeCodePointDegreeSymbol}C`;

  if (unitOfMeasurementSymbolString === "m3/h")
    return `m${unicodeCodePointSuperscriptThree}/h`;

  // If no symbol exists
  return unitOfMeasurementSymbolString;
};

/**
 * Extract the phenomenon name from a Datastream's name
 * @param {String} datastreamName A string representing the Datastream's name
 * @returns {String} The extracted phenomenon name
 */
const extractPhenomenonNameFromDatastreamName = function (datastreamName) {
  const regex = /\/ (.*) DS/;
  return datastreamName.match(regex)[1]; // use second element in array
};

/**
 * Format the response containing a Datastream's metadata from Sensorthings API
 * @param {Object} datastreamMetadata An object containing a Datastream's metadata
 * @returns {Object} An object containing the formatted metadata that is suitable for use in a line chart or heatmap
 */
const formatDatastreamMetadataForChart = function (datastreamMetadata) {
  const {
    description: datastreamDescription,
    name: datastreamName,
    unitOfMeasurement,
  } = datastreamMetadata;

  // Extract phenomenon name from Datastream name
  const phenomenonName =
    extractPhenomenonNameFromDatastreamName(datastreamName);

  // Get the unitOfMeasurement's symbol
  const unitOfMeasurementSymbol = matchUnitOfMeasurementSymbolStringToSymbol(
    unitOfMeasurement.symbol
  );

  return {
    datastreamDescription,
    datastreamName,
    phenomenonName,
    unitOfMeasurementSymbol,
  };
};

/**
 * Extract the properties that make up the formatted datastream metadata object(s)
 * @param {Array} formattedDatastreamsMetadataArr An array of formatted metadata object(s) from one or more datastreams
 * @returns {Object} An object that contains array(s) of formatted datastream metadata properties
 */
const extractPropertiesFromFormattedDatastreamMetadata = function (
  formattedDatastreamsMetadataArr
) {
  // Create arrays from the properties of the formatted datastream metadata
  const datastreamDescriptionsArr = formattedDatastreamsMetadataArr.map(
    (datastreamMetadata) => datastreamMetadata.datastreamDescription
  );

  const datastreamNamesArr = formattedDatastreamsMetadataArr.map(
    (datastreamMetadata) => datastreamMetadata.datastreamName
  );

  const phenomenonNamesArr = formattedDatastreamsMetadataArr.map(
    (datastreamMetadata) => datastreamMetadata.phenomenonName
  );

  const unitOfMeasurementSymbolsArr = formattedDatastreamsMetadataArr.map(
    (datastreamMetadata) => datastreamMetadata.unitOfMeasurementSymbol
  );

  return {
    datastreamDescriptionsArr,
    datastreamNamesArr,
    phenomenonNamesArr,
    unitOfMeasurementSymbolsArr,
  };
};

/**
 * Traverses all the pages that make up the response from a SensorThingsAPI instance. The link to the next page, if present, is denoted by the presence of a "@iot.nextLink" property in the response object. This function concatenates all the values so that the complete results are returned in one array.
 * @async
 * @param {Promise} httpGetRequestPromise Promise object resulting from an Axios GET request
 * @returns {Promise} A promise that contains an object containing results from all the pages when fulfilled
 */
const combineResultsFromAllPages = async function (httpGetRequestPromise) {
  try {
    if (!httpGetRequestPromise) return;

    const lastSuccess = await httpGetRequestPromise;

    // The "success" objects contain a "data" object which in turn has a "value" property
    // If the "data" object in turn has a "@iot.nextLink" property, then a next page exists
    if (lastSuccess.data["@iot.nextLink"]) {
      const nextLinkSuccess = await combineResultsFromAllPages(
        axios.get(lastSuccess.data["@iot.nextLink"])
      );
      // The "data" object in turn has a "value" property
      // The "value" property's value is an array
      nextLinkSuccess.data.value = lastSuccess.data.value.concat(
        nextLinkSuccess.data.value
      );
      return nextLinkSuccess;
    } else {
      return lastSuccess;
    }
  } catch (err) {
    console.error(err);
  }
};

/**
 * Traverses all the pages that make up the response from a SensorThingsAPI instance and extracts the combined Observations
 * @async
 * @param {Promise} httpGetRequestPromise Promise object resulting from an Axios GET request
 * @returns {Promise} A promise that contains an array of Observations when fulfilled
 */
const extractCombinedObservationsFromAllPages = async function (
  httpGetRequestPromise
) {
  try {
    const successResponse = await combineResultsFromAllPages(
      httpGetRequestPromise
    );

    // Extract value array from the success response object
    const {
      data,
      data: { value: valueArr },
    } = successResponse;

    // Array that will hold the combined observations
    const combinedObservations = [];

    valueArr.forEach((val) => {
      // Each page of results will have a dataArray that holds the observations
      const { dataArray } = val;
      combinedObservations.push(...dataArray);
    });

    return new Promise((resolve, reject) => {
      resolve(combinedObservations);
    });
  } catch (err) {
    console.error(err);
  }
};

/**
 * Retrieve all the Observations from an array of Observations promises
 * @async
 * @param {Promise} observationPromiseArray An array that contains N observation promises
 * @returns {Promise} A promise that contains an array of Observations from multiple Datastreams when fulfilled
 */
const getObservationsFromMultipleDatastreams = async function (
  observationPromiseArray
) {
  try {
    // Array to store our final result
    const observationsAllDatastreamsArr = [];

    // Use for/of loop - we need to maintain the order of execution of the async operations
    for (const observationPromise of observationPromiseArray) {
      // Observations from a single Datastream
      const observations = await observationPromise;
      observationsAllDatastreamsArr.push(observations);
    }

    return observationsAllDatastreamsArr;
  } catch (err) {
    console.error(err);
  }
};

/**
 * Retrieve the metadata from a single Datastream or multiple Datastreams and the Observations corresponding to the Datastream(s)
 * @param {String} baseUrl Base URL of the STA server
 * @param {Object} urlParamObj The URL parameters to be sent together with the GET request
 * @param {Array} bldgSensorSamplingRateNestedArr A N*1 array (where N >= 1) containing a nested array of buildings, sensors & sampling rates as strings, i.e. [["101", "rl", "15min"]] or [["101", "rl", "15min"], ["102", "vl", "60min"]] or [["101", "rl", "15min"], ["102", "vl", "60min"], ["225", "vl", "60min"]], etc
 * @returns {Promise} A promise that contains a 1*2 array (the first element is an array that contans N Observations arrays; and the second element is an array of N Datastream metadata objects) when fulfilled
 */
const getMetadataPlusObservationsFromSingleOrMultipleDatastreams =
  async function (baseUrl, urlParamObj, bldgSensorSamplingRateNestedArr) {
    try {
      if (!bldgSensorSamplingRateNestedArr) return;

      // Datastreams IDs
      const datastreamsIdsArr = bldgSensorSamplingRateNestedArr.map(
        (bldgSensorSamplingRateArr) =>
          getDatastreamIdFromBuildingNumber(...bldgSensorSamplingRateArr)
      );

      // Observations URLs
      const observationsUrlArr = datastreamsIdsArr.map((datastreamId) =>
        createObservationsUrl(baseUrl, datastreamId)
      );

      // Datastreams URLs
      const datastreamsUrlArr = datastreamsIdsArr.map((datastreamId) =>
        createDatastreamUrl(baseUrl, datastreamId)
      );

      // Promise objects - Observations
      const observationsPromisesArr = observationsUrlArr.map((obsUrl) =>
        extractCombinedObservationsFromAllPages(
          performGetRequestUsingAxios(obsUrl, urlParamObj)
        )
      );

      // Observations array
      const observationsArr = await getObservationsFromMultipleDatastreams(
        observationsPromisesArr
      );

      // Metadata array
      const metadataArr = await getMetadataFromMultipleDatastreams(
        datastreamsUrlArr
      );

      return [observationsArr, metadataArr];
    } catch (err) {
      console.error(err);
    }
  };

/**
 * Calculate the temperature difference, dT, between Vorlauf temperature [VL] and Rücklauf temperature [RL] (i.e., dT = VL - RL)
 * @param {String} baseUrl Base URL of the STA server
 * @param {Object} urlParams The URL parameters to be sent together with the GET request
 * @param {String} buildingId The building ID as a string
 * @param {String} samplingRate The sampling rate as a string
 * @returns {Promise} A promise that contains an array (that is made up of a temperature difference array and a metadata object) when fulfilled
 */
const calculateVorlaufMinusRuecklaufTemperature = async function (
  baseUrl,
  urlParams,
  buildingId,
  samplingRate
) {
  try {
    const bldgSensorSamplingRateNestedArr = [
      [buildingId, "vl", samplingRate],
      [buildingId, "rl", samplingRate],
    ];

    const BUILDING_ID = buildingId;
    const SAMPLING_RATE = samplingRate;

    const observationsPlusMetadata =
      await getMetadataPlusObservationsFromSingleOrMultipleDatastreams(
        baseUrl,
        urlParams,
        bldgSensorSamplingRateNestedArr
      );

    // Extract Vorlauf temperature, Ruecklauf temperature and metadata
    const [
      [vorlaufTemperatureObsArr, ruecklaufTemperatureObsArr],
      [metadataVorlauf, metadataRuecklauf],
    ] = observationsPlusMetadata;

    // Extract the temperature values
    const vorlaufTemperatureValues = vorlaufTemperatureObsArr.map(
      (vlTempObs) => vlTempObs[1]
    );
    const ruecklaufTemperatureValues = ruecklaufTemperatureObsArr.map(
      (rlTempObs) => rlTempObs[1]
    );

    // The arrays have equal length, we need only use one of them for looping
    // Resulting array contains the following pairs (timestamp + dT)
    const vorlaufMinusRuecklaufTemperatureObs = vorlaufTemperatureObsArr.map(
      (vlTempObs, i) => [
        vlTempObs[0], // timestamp
        vorlaufTemperatureValues[i] - ruecklaufTemperatureValues[i],
      ]
    );

    // From Vorlauf metadata, extract `name` and `unitOfMeasurement`
    const {
      name: datastreamNameVorlauf,
      unitOfMeasurement: unitOfMeasurementVorlauf,
    } = metadataVorlauf;

    // From Ruecklauf metadata, extract `name`
    const { name: datastreamNameRuecklauf } = metadataRuecklauf;

    // Extract the phenomenon names from the Datastream names
    const phenomenonNameVorlauf = extractPhenomenonNameFromDatastreamName(
      datastreamNameVorlauf
    );
    const phenomenonNameRuecklauf = extractPhenomenonNameFromDatastreamName(
      datastreamNameRuecklauf
    );

    // Create our custom datastream description text
    // The resulting datastream description string has two `temperature` substrings;
    // replace the first occurence with an empty string
    const descriptionTempDifference =
      `Computed dT: ${phenomenonNameVorlauf} minus ${phenomenonNameRuecklauf}`.replace(
        "temperature",
        ""
      );

    // Create our custom datastream name text
    const nameTempDifference = `BOSCH_${BUILDING_ID} / dT Temperature difference (VL-RL) DS:${SAMPLING_RATE}`;

    // The datastream object that we return needs to have these property names
    const description = descriptionTempDifference;
    const name = nameTempDifference;
    const unitOfMeasurement = unitOfMeasurementVorlauf;

    return [
      vorlaufMinusRuecklaufTemperatureObs,
      {
        description,
        name,
        unitOfMeasurement,
      },
    ];
  } catch (err) {
    console.error(err);
  }
};

export {
  formatDatastreamMetadataForChart,
  extractPropertiesFromFormattedDatastreamMetadata,
  getMetadataPlusObservationsFromSingleOrMultipleDatastreams,
  calculateVorlaufMinusRuecklaufTemperature,
};