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

// src/modulate/bpsk.rs
use crate::core::{Block, WorkReport};
use crate::dsp::Rotator;
use num_complex::Complex32 as C32;

/// BPSK constellation mapper: u8 bit (LSB) → C32 symbol.
/// bit 0 → (+1, 0),  bit 1 → (−1, 0)
#[derive(Debug, Clone, Copy, Default)]
pub struct BpskMapper;

impl BpskMapper {
    pub fn new() -> Self {
        Self
    }
}

impl Block for BpskMapper {
    type In = u8;
    type Out = C32;

    #[inline(always)]
    fn process(&mut self, input: &[u8], output: &mut [C32]) -> WorkReport {
        let n = input.len().min(output.len());
        let mut i = 0;
        let nn = n & !3;
        while i < nn {
            output[i] = C32::new(if (input[i] & 1) == 0 { 1.0 } else { -1.0 }, 0.0);
            output[i + 1] = C32::new(if (input[i + 1] & 1) == 0 { 1.0 } else { -1.0 }, 0.0);
            output[i + 2] = C32::new(if (input[i + 2] & 1) == 0 { 1.0 } else { -1.0 }, 0.0);
            output[i + 3] = C32::new(if (input[i + 3] & 1) == 0 { 1.0 } else { -1.0 }, 0.0);
            i += 4;
        }
        while i < n {
            output[i] = C32::new(if (input[i] & 1) == 0 { 1.0 } else { -1.0 }, 0.0);
            i += 1;
        }
        WorkReport {
            in_read: n,
            out_written: n,
        }
    }
}

/// BPSK waveform stage: C32 symbols → C32 IQ.
/// rf_hz = 0.0 → baseband passthrough with gain.
/// rf_hz != 0.0 → rotate symbols onto carrier via Rotator.
#[derive(Debug, Clone)]
pub struct BpskMod {
    gain: f32,
    rot: Rotator,
}

impl BpskMod {
    pub fn new(fs: f32, rf_hz: f32, gain: f32) -> Self {
        Self {
            gain,
            rot: Rotator::new(rf_hz, fs),
        }
    }
    pub fn set_gain(&mut self, g: f32) {
        self.gain = g;
    }
}

impl Block for BpskMod {
    type In = C32;
    type Out = C32;

    #[inline(always)]
    fn process(&mut self, input: &[C32], output: &mut [C32]) -> WorkReport {
        let n = input.len().min(output.len());
        let g = self.gain;
        let mut i = 0;
        let nn = n & !3;
        while i < nn {
            let s0 = input[i];
            let r0 = self.rot.next();
            let s1 = input[i + 1];
            let r1 = self.rot.next();
            let s2 = input[i + 2];
            let r2 = self.rot.next();
            let s3 = input[i + 3];
            let r3 = self.rot.next();
            output[i] = C32::new(
                g * s0.re.mul_add(r0.re, -s0.im * r0.im),
                g * s0.im.mul_add(r0.re, s0.re * r0.im),
            );
            output[i + 1] = C32::new(
                g * s1.re.mul_add(r1.re, -s1.im * r1.im),
                g * s1.im.mul_add(r1.re, s1.re * r1.im),
            );
            output[i + 2] = C32::new(
                g * s2.re.mul_add(r2.re, -s2.im * r2.im),
                g * s2.im.mul_add(r2.re, s2.re * r2.im),
            );
            output[i + 3] = C32::new(
                g * s3.re.mul_add(r3.re, -s3.im * r3.im),
                g * s3.im.mul_add(r3.re, s3.re * r3.im),
            );
            i += 4;
        }
        while i < n {
            let s = input[i];
            let r = self.rot.next();
            output[i] = C32::new(
                g * s.re.mul_add(r.re, -s.im * r.im),
                g * s.im.mul_add(r.re, s.re * r.im),
            );
            i += 1;
        }
        WorkReport {
            in_read: n,
            out_written: n,
        }
    }
}
