const axios = require('axios');
const createError = require('http-errors');
const config = require('../config');
const { getBusToken, createBusRequest } = require('../utils/busAuth');
const { searchPatient } = require('../services/patient');
const { postDocumentReference, fetchDocumentReference } = require('../services/documentReference');
const { logger } = require('../utils/logger');
const { v4: uuidv4 } = require('uuid');


const DOCUMENT_REFERENCE_RESOURCE_TYPE = "DocumentReference";
const IPS_DOCUMENT_RESOURCE_TYPE = 'Bundle';
const PATIENT_RESOURCE_TYPE = 'Patient';
const LIST_RESOURCE_TYPE = 'List';


const NATIONAL_ID_SYSTEM = 'https://federador.msal.gob.ar/patient-id';
const DNI_SYSTEM = 'http://www.renaper.gob.ar/dni';
const CUSTODIAN_ID_SYSTEM = 'https://federador.msal.gob.ar/uri';
const MASTER_ID_SYSTEM = ''

/**
 * Procesa una transacción y devuelve los recursos persistidos en el servidor HAPI FHIR
 * @param {*} transactionBundle 
 * @returns 
 */
async function processTransaction(transactionBundle) {
    const response = await axios.post(`${config.fhir.url}`, transactionBundle, {
        headers: { 'Content-Type': 'application/fhir+json' },
    });
    if (response.status !== 200) {
        throw createError(response.status, response.data.issue.diagnostics);
    }
    const processed = response.data;
    const resources = [];
    const responses = processed.entry.map(e => e.response);
    for (i = 0; i < responses.length; i++) {
        const resource = await axios.get(`${config.fhir.url}/${responses[i].location}`)
        resources.push(resource);
    }
    return Promise.resolve(resources);
}

function extractResource(resources, resourceType) {
    return resources.map(r => r.data).filter(r => r.resourceType === resourceType)[0];
}

function extractLocalIdentifier(patient) {
    return patient.identifier.filter(i => {
        return i.system !== NATIONAL_ID_SYSTEM && ((!!i.use && i.use === 'official') || (!i.use))
    })[0];
}

/**
 * 
 * @param {*} documentReference 
 * @returns 
 */
async function getBusCustodianIdentifier() {
    return Promise.resolve({ system: CUSTODIAN_ID_SYSTEM, value: config.bus.issuer });
}

async function getBusPatientReference(patient, token) {
    const localIdentifier = extractLocalIdentifier(patient);
    const nationalPatientResponse = await searchPatient(token, { identifier: `${localIdentifier.system}|${localIdentifier.value}` });
    const nationalPatientBundle = nationalPatientResponse.data;
    if (nationalPatientBundle.total == 0) {
        throw createError(404, 'Patient does not exists');
    }
    // NOTE:La siguiente consulta no debería traer mas de un resultado.
    return Promise.resolve(nationalPatientBundle.entry[0].fullUrl);
}

async function getLocalIPSDocumentReference(localIPSDocument) {
    return Promise.resolve(`${config.baseURL}/fhir/Bundle/${localIPSDocument.id}`);
}

/**
 * Crea un nuevo document refrence en el bus
 * @param {*} token 
 * @param {*} localIPSDocument 
 * @param {*} localPatient 
 * @param {*} localDocumentReference 
 * @returns 
 */
async function createBusDocumentReference(token, localIPSDocument, localPatient) {
    const busCustodianIdentifier = await getBusCustodianIdentifier();
    const busPatientReference = await getBusPatientReference(localPatient, token);
    const localIPSDocumentReference = await getLocalIPSDocumentReference(localIPSDocument);
    const busDocumentReference = {
        resourceType: 'DocumentReference',
        status: 'current',
        masterIdentifier: {
            system: 'urn:ietf:rfc:3986',
            value: `urn:uuid:${uuidv4()}`
        },
        type: {
            coding: [
                {
                    system: 'http://loinc.org',
                    code: '60591-5',
                    display: 'Patient Summary Document',
                },
            ],
        },
        subject: {
            reference: busPatientReference
        },
        custodian: {
            identifier: busCustodianIdentifier,
        },
        content: [
            {
                attachment: {
                    url: localIPSDocumentReference,
                },
            },
        ],
    };
    const response = await postDocumentReference(token, busDocumentReference);
    const created = await fetchDocumentReference(token, response.headers['location']);
    return created.data;
}

/**
 * ITI-65: Provide Document Bundle (MHD)
 *
 * POST /fhir/Bundle
 *
 * Flow:
 *   1. Store the IPS Bundle in HAPI FHIR.
 *   2. Resolve the patient national identifier via Bus $match.
 *   3. Register a DocumentReference in the Bus pointing to the stored Bundle.
 *
 * Required header:
 *   x-custodian-id  — Efector identifier value in the Federador MSAL system.
 */
async function provideDocumentBundle(req, res, next) {
    try {
        const transaction = req.body;
        const token = await getBusToken(
            config.bus.url,
            config.bus.jwtSecret,
            config.bus.issuer,
            [config.bus.mpiScope, config.bus.documentRegistryScope].join(',')
        );

        // Paso 1: Ejecuto la transcción en el servidor hapi subyacente
        const resources = await processTransaction(transaction);
        // Paso 2: Obtengo el paciente local (tal como se guardo en la trasnaccion)
        const localPatient = extractResource(resources, PATIENT_RESOURCE_TYPE);
        // Paso 3: Obtengo el documento IPS local (tal como se guardo en la transacción)
        const localIPSDocument = extractResource(resources, IPS_DOCUMENT_RESOURCE_TYPE)
        // Paso 4: Creo el document reference en el indice de atenciones
        const busDocumentReference = await createBusDocumentReference(token, localIPSDocument, localPatient);

        return status(200).json(busDocumentReference);

    } catch (err) {
        next(err);
    }
}

module.exports = { provideDocumentBundle };