/**
  * Utils for looking up postcodes from addresses
  */
'use strict';

const debug = require('debug')('utils:postcodes');
const Q = require('q');

const config = require(global.configFile);
const idealPostcodes = require('ideal-postcodes')(config.idealPostcodesKey);
const UkClearAddressing = require('uk-clear-addressing');

const ERRORS = {
    UNSPECIFIED: 'Unspecified error'
};

module.exports = {
    ERRORS,
    postcodeLookup
};

/**
 * Runs a postcode lookup and returns a list of addresses that could match that
 * postcode.
 *
 * @param {string} postcode     - the postcode to lookup addresses for
 * @returns {Promise}           - promise for array of addressses
 */
function postcodeLookup(postcode) {
    debug('Postcode Lookup: ', postcode);

    return Q.ninvoke(
        idealPostcodes,
        'lookupPostcode',
        postcode
    ).then((addresses) => {
        const formatted = [];
        for (let i = 0; i < addresses.length; ++i) {
            formatted.push(pafToBridgeAddress(addresses[i]));
        }
        debug('Formatted:', formatted);

        return formatted;
    }).catch(() => {
        //
        // The API doesn't really make it possible to differentatiate errors at
        // this time.
        //
        const newError = ERRORS.UNSPECIFIED;
        return Q.reject(newError);
    });
}

/**
 * Converst a PAF (Royal Mail Postcode Address File) format address to a
 * Bridge style one.
 *
 * @param {Object} pafAddr  - the address is PAF format
 * @returns {Object}        - the address in Bridge format
 */
function pafToBridgeAddress(pafAddr) {
    //
    // Use the uk-clear-addressing module to do most of the work for us
    //
    const clearAddr = new UkClearAddressing(pafAddr).formattedAddress();

    // Disable the variable case error because uk-clear-addressing uses snake case
    // jshint -W106
    const bridgeAddress = {
        Town: clearAddr.post_town,
        PostCode: clearAddr.postcode,
        Country: 'United Kingdom'
    };
    if (clearAddr.line_3) {
        //
        // The address has 3 lines, so put the first one in BuildingNameFlat
        //
        bridgeAddress.BuildingNameFlat = clearAddr.line_1;
        bridgeAddress.Address1 = clearAddr.line_2;
        bridgeAddress.Address2 = clearAddr.line_3;
    } else if (clearAddr.line_1 === pafAddr.sub_building_name) {
        //
        // We differentiate between "BuildingNameFlat" and Address1, whereas
        // UkClearAddressing doesn't.  So if line_1 is just the sub building name,
        // then put that in flat, and move line 2 up.
        //
        bridgeAddress.BuildingNameFlat = clearAddr.line_1;
        bridgeAddress.Address1 = clearAddr.line_2;
    } else {
        //
        // This address has at most 2 lines, so just use the main fields.
        //
        bridgeAddress.Address1 = clearAddr.line_1;
        bridgeAddress.Address2 = clearAddr.line_2;
    }

    //
    // Convert the fields accross to our names for them.
    //
    return bridgeAddress;
}