"""
AC Analysis Example

This example demonstrates using the pyngspice Python extension
to perform AC analysis (frequency sweep) on an RC filter.
"""

try:
    from pyngspice import SimRunner, RawRead
except ImportError:
    print("pyngspice extension not installed. Run: pip install -e .")
    exit(1)

import numpy as np
import os

# RC filter netlist with AC analysis
netlist_content = """
* RC Low-Pass Filter - AC Analysis
* Shows magnitude and phase response

V1 in 0 AC 1
R1 in out 1k
C1 out 0 100n

.ac dec 100 1 100k
.end
"""

def main():
    output_dir = "./output"
    os.makedirs(output_dir, exist_ok=True)

    netlist_file = os.path.join(output_dir, "ac_filter.net")
    with open(netlist_file, "w") as f:
        f.write(netlist_content)

    print("Running AC analysis...")
    runner = SimRunner(output_folder=output_dir)
    raw_file, log_file = runner.run_now(netlist_file)

    raw = RawRead(raw_file)
    print(f"Analysis type: {raw.analysis_type}")
    print(f"Complex data: {raw.is_complex}")
    print(f"\nTraces: {raw.get_trace_names()}")

    # Get frequency and output voltage (complex)
    freq = raw.get_trace("frequency").get_wave(0)
    v_out_complex = raw.get_trace("V(out)").get_wave_complex(0)

    # Calculate magnitude in dB and phase in degrees
    magnitude_db = 20 * np.log10(np.abs(v_out_complex))
    phase_deg = np.angle(v_out_complex, deg=True)

    # Find -3dB cutoff frequency
    idx_3db = np.argmin(np.abs(magnitude_db - (-3)))
    f_cutoff = freq[idx_3db]

    print(f"\n-3dB cutoff frequency: {f_cutoff:.2f} Hz")
    print(f"Theoretical: {1/(2*np.pi*1e3*100e-9):.2f} Hz")

    # Plot if matplotlib available
    try:
        import matplotlib.pyplot as plt

        fig, (ax1, ax2) = plt.subplots(2, 1, figsize=(10, 8), sharex=True)

        ax1.semilogx(freq, magnitude_db)
        ax1.axhline(-3, color='r', linestyle='--', alpha=0.5, label='-3dB')
        ax1.axvline(f_cutoff, color='r', linestyle='--', alpha=0.5)
        ax1.set_ylabel('Magnitude (dB)')
        ax1.set_title('RC Low-Pass Filter Frequency Response')
        ax1.legend()
        ax1.grid(True, which='both', alpha=0.3)

        ax2.semilogx(freq, phase_deg)
        ax2.axhline(-45, color='r', linestyle='--', alpha=0.5, label='-45°')
        ax2.set_xlabel('Frequency (Hz)')
        ax2.set_ylabel('Phase (degrees)')
        ax2.legend()
        ax2.grid(True, which='both', alpha=0.3)

        plt.tight_layout()
        plot_file = os.path.join(output_dir, "ac_filter.png")
        plt.savefig(plot_file, dpi=150)
        print(f"\nPlot saved to: {plot_file}")
        plt.show()

    except ImportError:
        print("\nInstall matplotlib for plotting: pip install matplotlib")

if __name__ == "__main__":
    main()