// Copyright (c) 2025-2026 G & R Associates LLC
// SPDX-License-Identifier: MIT OR Apache-2.0

use crate::core::{Block, WorkReport};
use num_complex::Complex32 as C32;

#[derive(Debug, Clone)]
pub struct CwEnvelopeDemod {
    alpha: f32, // one-pole LP smoothing factor
    y: f32,     // LP state
    gain: f32,
}

impl CwEnvelopeDemod {
    pub fn new(sample_rate: f32, _tone_hz: f32, env_bw_hz: f32) -> Self {
        // One-pole LP: alpha = exp(-2π fc / fs). Larger fc → faster tracking.
        let fc = env_bw_hz.max(1.0);
        let alpha = (-std::f32::consts::TAU * fc / sample_rate).exp();
        Self {
            alpha,
            y: 0.0,
            gain: 1.0,
        }
    }
    pub fn set_gain(&mut self, g: f32) {
        self.gain = g;
    }
}

impl Block for CwEnvelopeDemod {
    type In = C32;
    type Out = f32;

    fn process(&mut self, input: &[Self::In], output: &mut [Self::Out]) -> WorkReport {
        let n = input.len().min(output.len());
        let a = self.alpha;
        for i in 0..n {
            let mag = (input[i].re * input[i].re + input[i].im * input[i].im).sqrt();
            self.y = a * self.y + (1.0 - a) * mag;
            output[i] = self.y * self.gain;
        }
        WorkReport {
            in_read: n,
            out_written: n,
        }
    }
}
