#[macro_use]
extern crate gstreamer as gst;
use gst::prelude::*;
extern crate gstreamer_app as gst_app;
extern crate gstreamer_audio as gst_audio;

extern crate glib;

extern crate byte_slice_cast;
use byte_slice_cast::*;

use std::error::Error as StdError;
use std::i16;
use std::i32;

extern crate failure;
use failure::Error;

#[macro_use]
extern crate failure_derive;

#[path = "../examples-common.rs"]
mod examples_common;

#[derive(Debug, Fail)]
#[fail(display = "Missing element {}", _0)]
struct MissingElement(&'static str);

#[derive(Debug, Fail)]
#[fail(display = "Received error from {}: {} (debug: {:?})", src, error, debug)]
struct ErrorMessage {
    src: String,
    error: String,
    debug: Option<String>,
    #[cause]
    cause: glib::Error,
}

fn create_pipeline() -> Result<gst::Pipeline, Error> {
    gst::init()?;

    let pipeline = gst::Pipeline::new(None);
    let src =
        gst::ElementFactory::make("audiotestsrc", None).ok_or(MissingElement("audiotestsrc"))?;
    let sink = gst::ElementFactory::make("appsink", None).ok_or(MissingElement("appsink"))?;

    pipeline.add_many(&[&src, &sink])?;
    src.link(&sink)?;

    let appsink = sink.clone()
        .dynamic_cast::<gst_app::AppSink>()
        .expect("Sink element is expected to be an appsink!");

    appsink.set_caps(&gst::Caps::new_simple(
        "audio/x-raw",
        &[
            ("format", &gst_audio::AUDIO_FORMAT_S16.to_string()),
            ("layout", &"interleaved"),
            ("channels", &(1i32)),
            ("rate", &gst::IntRange::<i32>::new(1, i32::MAX)),
        ],
    ));

    appsink.set_callbacks(
        gst_app::AppSinkCallbacks::new()
            .new_sample(|appsink| {
                let sample = match appsink.pull_sample() {
                    None => return gst::FlowReturn::Eos,
                    Some(sample) => sample,
                };

                let buffer = if let Some(buffer) = sample.get_buffer() {
                    buffer
                } else {
                    gst_element_error!(
                        appsink,
                        gst::ResourceError::Failed,
                        ("Failed to get buffer from appsink")
                    );

                    return gst::FlowReturn::Error;
                };

                let map = if let Some(map) = buffer.map_readable() {
                    map
                } else {
                    gst_element_error!(
                        appsink,
                        gst::ResourceError::Failed,
                        ("Failed to map buffer readable")
                    );

                    return gst::FlowReturn::Error;
                };

                let samples = if let Ok(samples) = map.as_slice_of::<i16>() {
                    samples
                } else {
                    gst_element_error!(
                        appsink,
                        gst::ResourceError::Failed,
                        ("Failed to interprete buffer as S16 PCM")
                    );

                    return gst::FlowReturn::Error;
                };

                let sum: f64 = samples
                    .iter()
                    .map(|sample| {
                        let f = f64::from(*sample) / f64::from(i16::MAX);
                        f * f
                    })
                    .sum();
                let rms = (sum / (samples.len() as f64)).sqrt();
                println!("rms: {}", rms);

                gst::FlowReturn::Ok
            })
            .build(),
    );

    Ok(pipeline)
}

fn main_loop(pipeline: gst::Pipeline) -> Result<(), Error> {
    pipeline.set_state(gst::State::Playing).into_result()?;

    let bus = pipeline
        .get_bus()
        .expect("Pipeline without bus. Shouldn't happen!");

    while let Some(msg) = bus.timed_pop(gst::CLOCK_TIME_NONE) {
        use gst::MessageView;

        match msg.view() {
            MessageView::Eos(..) => break,
            MessageView::Error(err) => {
                pipeline.set_state(gst::State::Null).into_result()?;
                Err(ErrorMessage {
                    src: err.get_src()
                        .map(|s| s.get_path_string())
                        .unwrap_or_else(|| String::from("None")),
                    error: err.get_error().description().into(),
                    debug: err.get_debug(),
                    cause: err.get_error(),
                })?;
            }
            _ => (),
        }
    }

    pipeline.set_state(gst::State::Null).into_result()?;

    Ok(())
}

fn example_main() {
    match create_pipeline().and_then(main_loop) {
        Ok(r) => r,
        Err(e) => eprintln!("Error! {}", e),
    }
}

fn main() {
    // tutorials_common::run is only required to set up the application environent on macOS
    // (but not necessary in normal Cocoa applications where this is set up autmatically)
    examples_common::run(example_main);
}