use iced_video_player::gst::prelude::*;
use iced_video_player::{Video, gst, gst_app, gst_pbutils};

use cosmic::action;
use cosmic::app::Task;

const SUSPICIOUS_AUDIO_GAP_DURATION: gst::ClockTime = gst::ClockTime::SECOND;

fn is_suspicious_audio_gap(duration: Option<gst::ClockTime>) -> bool {
    duration.is_some_and(|duration| duration >= SUSPICIOUS_AUDIO_GAP_DURATION)
}

fn suppress_suspicious_audio_gaps(audio_filter: &gst::Element) {
    let Some(src_pad) = audio_filter.static_pad("src") else {
        log::warn!("audio filter has no source pad; malformed audio gaps will not be suppressed");
        return;
    };

    let _ = src_pad.add_probe(gst::PadProbeType::EVENT_DOWNSTREAM, |_, info| {
        let Some(event) = info.event() else {
            return gst::PadProbeReturn::Ok;
        };
        let gst::EventView::Gap(gap) = event.view() else {
            return gst::PadProbeReturn::Ok;
        };
        let (timestamp, duration) = gap.get();
        if !is_suspicious_audio_gap(duration) {
            return gst::PadProbeReturn::Ok;
        }

        // Some malformed MP4 edit lists cause streamsynchronizer to emit a
        // long GAP before almost every audio buffer. The next buffer's PTS is
        // still continuous, so forwarding those events makes audio sinks
        // repeatedly wait or resynchronise and produces choppy playback.
        log::debug!("suppressing audio GAP at {timestamp} with duration {duration:?}");
        drop(info.take_event());
        gst::PadProbeReturn::Handled
    });
}

#[derive(Debug, Default)]
pub struct VideoSettings {
    pub mute: bool,
}

pub fn new_video(
    url: &url::Url,
    settings: VideoSettings,
) -> Result<Video, cosmic::Task<cosmic::Action<super::Message>>> {
    //TODO: this code came from iced_video_player::Video::new and has been modified to stop the pipeline on error
    //TODO: remove unwraps and enable playback of files with only audio.
    gst::init().unwrap();
    disable_broken_hardware_decoders();

    let pipeline = format!(
        "playbin uri=\"{}\"{}{} video-sink=\"videoscale ! videoconvert ! videoflip method=automatic ! appsink name=iced_video drop=true caps=video/x-raw,format=NV12,pixel-aspect-ratio=1/1\"",
        url.as_str(),
        if settings.mute { " mute=true" } else { "" },
        if settings.mute {
            " audio-sink=fakesink"
        } else {
            ""
        }
    );
    let pipeline = gst::parse::launch(pipeline.as_ref())
        .unwrap()
        .downcast::<gst::Pipeline>()
        .map_err(|_| iced_video_player::Error::Cast)
        .unwrap();
    let audio_filter = gst::ElementFactory::make("scaletempo")
        .build()
        .unwrap_or_else(|_| {
            log::warn!("scaletempo element not available; speed changes will affect pitch");
            gst::ElementFactory::make("identity").build().unwrap()
        });
    suppress_suspicious_audio_gaps(&audio_filter);
    pipeline.set_property("audio-filter", &audio_filter);
    pipeline.connect("element-setup", false, |vals| {
        let Ok(elem) = vals[1].get::<gst::Element>() else {
            return None;
        };
        if let Some(factory) = elem.factory()
            && factory.name() == "souphttpsrc"
        {
            elem.set_property(
                "user-agent",
                "Mozilla/5.0 (X11; Linux x86_64; rv:142.0) Gecko/20100101 Firefox/142.0",
            );
        }
        None
    });
    let video_sink: gst::Element = pipeline.property("video-sink");
    let pad = video_sink.pads().first().cloned().unwrap();
    let pad = pad.dynamic_cast::<gst::GhostPad>().unwrap();
    let bin = pad
        .parent_element()
        .unwrap()
        .downcast::<gst::Bin>()
        .unwrap();
    let video_sink = bin.by_name("iced_video").unwrap();
    let video_sink = video_sink.downcast::<gst_app::AppSink>().unwrap();

    match Video::from_gst_pipeline(pipeline.clone(), video_sink, None) {
        Ok(ok) => Ok(ok),
        Err(err) => {
            log::warn!("failed to open {}: {err}", url);
            // Handle codecs required before the file can play
            let mut commands = Vec::new();
            while let Some(msg) = pipeline
                .bus()
                .unwrap()
                .pop_filtered(&[gst::MessageType::Element])
            {
                if let gst::MessageView::Element(element) = msg.view()
                    && gst_pbutils::MissingPluginMessage::is(element)
                {
                    commands.push(Task::perform(
                        async { action::app(super::Message::MissingPlugin(msg)) },
                        |x| x,
                    ));
                    // Do one codec install at a time
                    break;
                }
            }
            pipeline.set_state(gst::State::Null).unwrap();
            Err(Task::batch(commands))
        }
    }
}

fn disable_broken_hardware_decoders() {
    let registry = gst::Registry::get();
    for decoder in [
        "nvav1dec",
        "nvh264dec",
        "nvh265dec",
        "nvjpegdec",
        "nvmpeg2videodec",
        "nvmpeg4videodec",
        "nvmpegvideodec",
        "nvvp8dec",
        "nvvp9dec",
    ] {
        if let Some(feature) = registry.lookup_feature(decoder) {
            let rank = feature.rank();
            feature.set_rank(gst::Rank::NONE);
            log::debug!("disabled GStreamer decoder {decoder} with rank {rank:?}");
        }
    }
}

#[cfg(test)]
mod tests {
    use super::is_suspicious_audio_gap;
    use iced_video_player::gst;

    #[test]
    fn long_audio_gap_is_suspicious() {
        assert!(is_suspicious_audio_gap(Some(gst::ClockTime::SECOND)));
        assert!(is_suspicious_audio_gap(Some(
            gst::ClockTime::from_seconds(3)
        )));
    }

    #[test]
    fn short_or_unknown_audio_gap_is_preserved() {
        assert!(!is_suspicious_audio_gap(Some(
            gst::ClockTime::from_mseconds(999)
        )));
        assert!(!is_suspicious_audio_gap(None));
    }
}