const states = global.get('homeassistant.homeAssistant.states')
const temp_F = states['sensor.home_tempest_temperature'].state
const elevation_ft = 693

// Get the pressure from the payload
let pressure_inHg = msg.payload

if (isNaN(pressure_inHg)) {
    node.error("Invalid pressure value in msg.payload: " + msg.payload)
    msg.payload = null
    return null
}

// Convert pressure from inHg to hPa
let pressure_hPa = pressure_inHg * 33.8639

// Convert temperature to °C
let temp_C = (temp_F - 32) * (5 / 9)

// Convert elevation from feet to meters
let elevation_m = elevation_ft / 3.28084

// Apply the barometric formula
let slp = pressure_hPa * Math.pow(
    1 - ((0.0065 * elevation_m) / (temp_C + (0.0065 * elevation_m) + 273.15)),
    -5.257
)

// Optional: Convert back to inHg
let slp_inHg = slp / 33.8639

// Round both values
slp = Math.round(slp * 100) / 100
slp_inHg = Math.round(slp_inHg * 100) / 100

// Return the SLP value
msg.payload = slp_inHg

node.status({fill:'Success',shape:'dot',text:'green'})

return msg