import numpy as np
import pandas as pd

# Constants
V = 0.5  # Balloon volume in m³
R = 285  # Specific gas constant for air in J/(kg·K)
Cv = 715  # Specific heat capacity of air in J/(kg·K)
P_initial = 5 * 1e5  # Initial pressure in Pa (5 bar)
T_initial = 293.15  # Initial temperature in K (20°C)
n = 500  # Total simulation duration in seconds
dt = 20  # Time step in seconds
A = 3  # Balloon surface area in m²
h = 3  # Heat loss coefficient in W/m²/K
T_ext = 300  # External temperature in K

# Functions to calculate tau, mair, and Tair as a function of pressure (in bar)
def tau(x):
    return 0.0019 * x**3 - 0.0485 * x**2 + 0.5328 * x + 1.2794

def mair(x):
    return -0.0006 * x + 0.0149

def Tair(x):
    return 0.1135 * x**3 - 2.2814 * x**2 + 17.361 * x + 16.564

# Initialization
P = P_initial
T = T_initial
m = (P * V) / (R * T)  # Initial mass of air in the balloon
W_cumule = 0  # Initial cumulative work

# List to store results
results = []

# Simulation loop
for t in range(0, n + dt, dt):
    x = P / 1e5  # Convert pressure to bar
    current_mair = mair(x)
    current_Tair = Tair(x) + 273.15  # Convert to Kelvin
    current_tau = tau(x)

    # Mass of air injected during dt
    m_injected = current_mair * dt

    # Heat losses
    Q_pertes = h * A * (T - T_ext) * dt

    # Thermal balance to calculate final temperature
    T_final = (m * Cv * T + m_injected * Cv * current_Tair - Q_pertes) / ((m + m_injected) * Cv)

    # Update mass and temperature
    m += m_injected
    T = T_final

    # Update pressure using the ideal gas law
    P = (m * R * T) / V

    # Update cumulative work
    W_cumule += current_tau * dt

    # Store results
    results.append({
        "Time (s)": t,
        "Pressure (Pa)": P,
        "Temperature (K)": T,
        "Mass (kg)": m,
        "Power (tau)": current_tau,
        "Flow rate (mair)": current_mair,
        "Injected air temperature (Tair)": current_Tair,
        "Cumulative work (J)": W_cumule,
        "Heat losses (J)": Q_pertes
    })

# Create a DataFrame and export to TSV
df = pd.DataFrame(results)
df.to_csv("thermal_loss_filling_simulation.tsv", sep="\t", index=False)

print("Simulation complete. Results exported to 'thermal_loss_filling_simulation.tsv'.")