const fs = require('node:fs');
const fsPromises = require('node:fs/promises');
const path = require('node:path');
const { execFile } = require('node:child_process');
const { promisify } = require('node:util');

const execFileAsync = promisify(execFile);

const ROOT_DIRECTORY = path.join(__dirname, '..');
const DATA_DIRECTORY = process.env.DATA_DIRECTORY
    ? path.resolve(process.env.DATA_DIRECTORY)
    : path.join(ROOT_DIRECTORY, 'data');
const LOGS_DIRECTORY = process.env.LOGS_DIRECTORY
    ? path.resolve(process.env.LOGS_DIRECTORY)
    : path.join(ROOT_DIRECTORY, 'logs');
const RUNTIME_CONFIG_FILE = process.env.RUNTIME_CONFIG_FILE
    ? path.resolve(process.env.RUNTIME_CONFIG_FILE)
    : path.join(ROOT_DIRECTORY, 'config', 'runtime.json');
const ACQUISITION_HELPER = process.env.EZO_ACQUIRE_HELPER
    ? path.resolve(process.env.EZO_ACQUIRE_HELPER)
    : path.join(ROOT_DIRECTORY, 'sensors', 'EZOCommand', 'EZO_ACQUIRE');

const SENSOR_FILES = {
    temperature: {
        json: 'EZORTD.json',
        csv: 'temperature.csv',
        key: 'temperature'
    },
    ph: { json: 'EZOPH.json', csv: 'ph.csv', key: 'ph' },
    do: { json: 'EZODO.json', csv: 'do.csv', key: 'do' },
    ec: { json: 'EZOEC.json', csv: 'ec.csv', key: 'ec' }
};

const ALLOWED_LOGGING_RATES = new Set([1, 5, 10, 60]);

async function atomicWriteFile(filePath, content) {
    await fsPromises.mkdir(path.dirname(filePath), { recursive: true });
    const temporaryPath = `${filePath}.${process.pid}.${Date.now()}.tmp`;
    await fsPromises.writeFile(temporaryPath, content, 'utf8');
    await fsPromises.rename(temporaryPath, filePath);
}

async function readRuntimeConfig() {
    try {
        const rawConfig = await fsPromises.readFile(RUNTIME_CONFIG_FILE, 'utf8');
        const config = JSON.parse(rawConfig);
        const rate = Number(config.loggingRateSeconds);

        return {
            loggingRateSeconds: ALLOWED_LOGGING_RATES.has(rate) ? rate : 1
        };
    } catch {
        return { loggingRateSeconds: 1 };
    }
}

async function writeRuntimeConfig(rate) {
    const numericRate = Number(rate);

    if (!ALLOWED_LOGGING_RATES.has(numericRate)) {
        const error = new Error('Frecuencia no válida.');
        error.status = 400;
        throw error;
    }

    const config = {
        loggingRateSeconds: numericRate,
        updatedAt: new Date().toISOString()
    };
    await atomicWriteFile(
        RUNTIME_CONFIG_FILE,
        `${JSON.stringify(config, null, 2)}\n`
    );
    return config;
}

function detectAcquisitionMode() {
    const requestedMode = String(process.env.EZO_MODE || 'auto').toLowerCase();
    const hardwareReady = process.platform === 'linux' &&
        fs.existsSync('/dev/i2c-1') &&
        fs.existsSync(ACQUISITION_HELPER);

    if (requestedMode === 'hardware' && !hardwareReady) {
        return {
            mode: 'unavailable',
            message: 'Se solicitó hardware, pero /dev/i2c-1 o EZO_ACQUIRE no está disponible.'
        };
    }

    if (requestedMode === 'hardware' || (requestedMode === 'auto' && hardwareReady)) {
        return { mode: 'hardware', message: 'Adquisición I2C real activa.' };
    }

    return { mode: 'demo', message: 'Adquisición de demostración activa.' };
}

function buildDemoReadings() {
    return {
        temperature: Number((25 + Math.random() * 0.1 - 0.05).toFixed(3)),
        ph: Number((7.2 + Math.random() * 0.04 - 0.02).toFixed(3)),
        do: Number((8.5 + Math.random() * 0.1 - 0.05).toFixed(3)),
        ec: Number((1050 + Math.random() * 10 - 5).toFixed(1))
    };
}

async function readHardwareSensors() {
    const { stdout } = await execFileAsync(
        ACQUISITION_HELPER,
        ['/dev/i2c-1'],
        { timeout: 5000, windowsHide: true }
    );
    const readings = JSON.parse(stdout.trim());

    if (!readings || typeof readings !== 'object') {
        throw new Error('EZO_ACQUIRE devolvió una respuesta inválida.');
    }

    return readings;
}

async function appendReading(filePath, timestamp, value) {
    await fsPromises.mkdir(path.dirname(filePath), { recursive: true });
    let needsHeader = false;

    try {
        const stats = await fsPromises.stat(filePath);
        needsHeader = stats.size === 0;
    } catch (error) {
        if (error.code !== 'ENOENT') throw error;
        needsHeader = true;
    }

    const row = `${timestamp},${value}\n`;
    await fsPromises.appendFile(
        filePath,
        `${needsHeader ? 'timestamp,value\n' : ''}${row}`,
        'utf8'
    );
}

async function publishReading(sensorId, rawValue, timestamp, mode) {
    const sensor = SENSOR_FILES[sensorId];
    const jsonPath = path.join(DATA_DIRECTORY, sensor.json);
    const hasReading = rawValue !== null &&
        rawValue !== undefined &&
        rawValue !== '';
    const value = hasReading ? Number(rawValue) : NaN;

    if (!Number.isFinite(value)) {
        await atomicWriteFile(jsonPath, `${JSON.stringify({
            online: false,
            timestamp,
            error: 'Lectura no disponible'
        })}\n`);
        return false;
    }

    await Promise.all([
        atomicWriteFile(jsonPath, `${JSON.stringify({
            [sensor.key]: value,
            online: true,
            timestamp,
            mode
        })}\n`),
        appendReading(path.join(LOGS_DIRECTORY, sensor.csv), timestamp, value)
    ]);
    return true;
}

async function collectReadings() {
    const modeInfo = detectAcquisitionMode();

    if (modeInfo.mode === 'unavailable') {
        throw new Error(modeInfo.message);
    }

    const readings = modeInfo.mode === 'hardware'
        ? await readHardwareSensors()
        : buildDemoReadings();
    const timestamp = new Date().toISOString();
    const results = await Promise.all(
        Object.keys(SENSOR_FILES).map(async (sensorId) => ({
            sensorId,
            online: await publishReading(
                sensorId,
                readings[sensorId],
                timestamp,
                modeInfo.mode
            )
        }))
    );

    return { mode: modeInfo.mode, timestamp, results };
}

async function publishAllOffline(error) {
    const timestamp = new Date().toISOString();
    const message = error instanceof Error ? error.message : String(error);

    await Promise.all(
        Object.values(SENSOR_FILES).map((sensor) =>
            atomicWriteFile(
                path.join(DATA_DIRECTORY, sensor.json),
                `${JSON.stringify({
                    online: false,
                    timestamp,
                    error: message
                })}\n`
            )
        )
    );
}

module.exports = {
    ACQUISITION_HELPER,
    ALLOWED_LOGGING_RATES,
    RUNTIME_CONFIG_FILE,
    SENSOR_FILES,
    atomicWriteFile,
    collectReadings,
    detectAcquisitionMode,
    publishAllOffline,
    publishReading,
    readRuntimeConfig,
    writeRuntimeConfig
};