import math

def bell202_fsk_modulate(bits, sample_rate=8000, baud_rate=1200):
    """
    Modulates a list of bits into a Bell 202 FSK continuous-phase audio signal.
    
    Bell 202 Standards:
    - Mark (1): 1200 Hz
    - Space (0): 2200 Hz
    - Transmission speed: 1200 baud
    """
    MARK_FREQ = 1200   # Frequency for '1'
    SPACE_FREQ = 2200  # Frequency for '0'
    
    # Calculate how many audio samples represent a single bit
    samples_per_bit = sample_rate / baud_rate
    
    signal = []
    phase = 0.0
    
    # Process each bit sequentially
    for bit in bits:
        # 1. Assign the target frequency based on the bit value
        freq = MARK_FREQ if bit == 1 else SPACE_FREQ
        
        # 2. Determine the exact integer sample count for this bit duration
        num_samples = int(round(samples_per_bit))
        
        # 3. Generate sine wave samples for this bit's duration
        for _ in range(num_samples):
            sample = math.sin(phase)
            signal.append(sample)
            
            # Increment phase relative to the current frequency
            phase += 2 * math.pi * freq / sample_rate
            
        # Keep phase bounded between 0 and 2*pi to avoid floating-point drift
        phase = phase % (2 * math.pi)
        
    return signal


# --- Example Usage ---
if __name__ == "__main__":
    # Example bitstream (e.g., standard testing sequence)
    binary_data = [1, 0, 1, 1, 0, 0, 1]
    
    # Generate the signal using standard 8000 Hz telephone sample rate
    fs = 8000
    fsk_signal = bell202_fsk_modulate(binary_data, sample_rate=fs)
    
    print(f"Successfully modulated {len(binary_data)} bits!")
    print(f"Total audio samples generated: {len(fsk_signal)}")
    print(f"First 10 raw sample floating-point values:")
    print([round(sample, 4) for sample in fsk_signal[:10]])