//! Microphone capture.

use std::time::Instant;

use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
use cpal::{Sample, SampleFormat, SupportedStreamConfig};
use crossbeam_channel::Sender;

use asist_core::config::AudioConfig;
use asist_core::error::{Error, Result};

use crate::{describe, ASR_SAMPLE_RATE};

/// Format the device was actually opened with.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct InputFormat {
    pub sample_rate: usize,
    pub channels: usize,
}

/// A block as it comes out of the callback, with the timestamp that later
/// lets us measure how far the pipeline lags behind the voice.
#[derive(Debug)]
pub struct CaptureBlock {
    pub samples: Vec<f32>,
    pub at: Instant,
}

pub struct Capture {
    stream: cpal::Stream,
    pub format: InputFormat,
    pub device_name: String,
}

impl Capture {
    /// Opens the input and starts pushing blocks through `tx`.
    ///
    /// It prefers 16 kHz mono because that is exactly what the model wants: if
    /// the device accepts it, there is no resampling anywhere on the path.
    pub fn open(config: &AudioConfig, tx: Sender<CaptureBlock>) -> Result<Self> {
        let host = cpal::default_host();
        let device = select_device(&host, &config.input_device)?;
        let device_name = describe(&device);

        let supported = preferred_config(&device)?;
        let format = InputFormat {
            sample_rate: supported.sample_rate() as usize,
            channels: supported.channels() as usize,
        };
        let stream_config: cpal::StreamConfig = supported.clone().into();
        let on_error = |err| tracing::error!(target: "audio", %err, "input stream");

        // Inside the callback: convert to f32, send and leave. `send` on an
        // unbounded channel does not block, which is the only property that
        // matters here.
        macro_rules! build {
            ($sample:ty) => {
                device
                    .build_input_stream(
                        &stream_config,
                        move |data: &[$sample], _: &_| {
                            let samples = data.iter().map(|s| f32::from_sample(*s)).collect();
                            let _ = tx.send(CaptureBlock {
                                samples,
                                at: Instant::now(),
                            });
                        },
                        on_error,
                        None,
                    )
                    .map_err(|e| Error::Audio(format!("could not open the input: {e}")))?
            };
        }

        let stream = match supported.sample_format() {
            SampleFormat::F32 => build!(f32),
            SampleFormat::I16 => build!(i16),
            SampleFormat::U16 => build!(u16),
            other => {
                return Err(Error::Audio(format!(
                    "unsupported sample format: {other:?}"
                )))
            }
        };
        stream
            .play()
            .map_err(|e| Error::Audio(format!("could not start the input: {e}")))?;

        tracing::info!(
            target: "audio",
            device = %device_name,
            hz = format.sample_rate,
            channels = format.channels,
            resampling = format.sample_rate != ASR_SAMPLE_RATE as usize || format.channels != 1,
            "entrada abierta"
        );

        Ok(Self {
            stream,
            format,
            device_name,
        })
    }

    /// Closes the device. Dropping the sender makes the chain of threads
    /// take itself apart from top to bottom.
    pub fn stop(self) {
        drop(self.stream);
    }
}

fn select_device(host: &cpal::Host, wanted: &str) -> Result<cpal::Device> {
    if wanted.is_empty() {
        return host
            .default_input_device()
            .ok_or_else(|| Error::Audio("no input device".into()));
    }
    let wanted_lower = wanted.to_lowercase();
    let devices = host
        .input_devices()
        .map_err(|e| Error::Audio(format!("could not list the inputs: {e}")))?;
    let mut seen = Vec::new();
    for device in devices {
        let name = describe(&device);
        if name.to_lowercase().contains(&wanted_lower) {
            return Ok(device);
        }
        seen.push(name);
    }
    Err(Error::Audio(format!(
        "no input matches «{wanted}». Available: {}",
        seen.join(", ")
    )))
}

fn preferred_config(device: &cpal::Device) -> Result<SupportedStreamConfig> {
    let native = device
        .supported_input_configs()
        .map_err(|e| Error::Audio(format!("could not query the input: {e}")))?
        .filter(|range| range.channels() == 1)
        .filter(|range| {
            range.min_sample_rate() <= ASR_SAMPLE_RATE && ASR_SAMPLE_RATE <= range.max_sample_rate()
        })
        .find(|range| range.sample_format() == SampleFormat::F32)
        .map(|range| range.with_sample_rate(ASR_SAMPLE_RATE));

    match native {
        Some(config) => Ok(config),
        None => device
            .default_input_config()
            .map_err(|e| Error::Audio(format!("no input configuration: {e}"))),
    }
}