// SPDX-License-Identifier: MPL-2.0

use crate::streamproducer::InterStreamProducer;
use anyhow::Error;
use gst::glib;
use gst::prelude::*;
use gst::subclass::prelude::*;

use std::sync::Mutex;

use once_cell::sync::Lazy;

const DEFAULT_PRODUCER_NAME: &str = "default";

#[derive(Debug)]
struct Settings {
    producer_name: String,
}

impl Default for Settings {
    fn default() -> Self {
        Settings {
            producer_name: DEFAULT_PRODUCER_NAME.to_string(),
        }
    }
}

struct State {
    appsink: gst_app::AppSink,
    sinkpad: gst::GhostPad,
}

/* Locking order is field order */
pub struct InterSink {
    settings: Mutex<Settings>,
    state: Mutex<State>,
}

impl InterSink {
    fn prepare(&self) -> Result<(), Error> {
        let settings = self.settings.lock().unwrap();
        let state = self.state.lock().unwrap();

        InterStreamProducer::acquire(&settings.producer_name, &state.appsink)?;

        Ok(())
    }

    fn unprepare(&self) {
        let settings = self.settings.lock().unwrap();
        InterStreamProducer::release(&settings.producer_name);
    }
}

static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
    gst::DebugCategory::new(
        "intersink",
        gst::DebugColorFlags::empty(),
        Some("Inter Sink"),
    )
});

#[glib::object_subclass]
impl ObjectSubclass for InterSink {
    const NAME: &'static str = "GstInterSink";
    type Type = super::InterSink;
    type ParentType = gst::Bin;

    fn with_class(klass: &Self::Class) -> Self {
        let templ = klass.pad_template("sink").unwrap();
        let sinkpad = gst::GhostPad::from_template(&templ);

        Self {
            settings: Mutex::new(Default::default()),
            state: Mutex::new(State {
                appsink: gst_app::AppSink::builder().name("appsink").build(),
                sinkpad: sinkpad.upcast(),
            }),
        }
    }
}

impl ObjectImpl for InterSink {
    fn properties() -> &'static [glib::ParamSpec] {
        static PROPERTIES: Lazy<Vec<glib::ParamSpec>> = Lazy::new(|| {
            vec![glib::ParamSpecString::builder("producer-name")
                .nick("Producer Name")
                .blurb("Producer Name to use")
                .doc_show_default()
                .mutable_playing()
                .build()]
        });

        PROPERTIES.as_ref()
    }

    fn set_property(&self, _id: usize, value: &glib::Value, pspec: &glib::ParamSpec) {
        match pspec.name() {
            "producer-name" => {
                let mut settings = self.settings.lock().unwrap();
                let old_producer_name = settings.producer_name.clone();
                settings.producer_name = value
                    .get::<String>()
                    .unwrap_or_else(|_| DEFAULT_PRODUCER_NAME.to_string());

                if let Some(appsink) = InterStreamProducer::release(&old_producer_name) {
                    if let Err(err) =
                        InterStreamProducer::acquire(&settings.producer_name, &appsink)
                    {
                        drop(settings);
                        gst::error!(CAT, imp: self, "{err}");
                        self.post_error_message(gst::error_msg!(
                            gst::StreamError::Failed,
                            ["{err}"]
                        ))
                    } else {
                        drop(settings);
                        // This is required because StreamProducer obtains the latency
                        // it needs to forward from Latency events, and we need to let the
                        // application know it should recalculate latency to get the event
                        // to travel upstream again
                        self.post_message(gst::message::Latency::new());
                    }
                }
            }
            _ => unimplemented!(),
        };
    }

    fn property(&self, _id: usize, pspec: &glib::ParamSpec) -> glib::Value {
        match pspec.name() {
            "producer-name" => {
                let settings = self.settings.lock().unwrap();
                settings.producer_name.to_value()
            }
            _ => unimplemented!(),
        }
    }

    fn constructed(&self) {
        self.parent_constructed();
        let obj = self.obj();

        obj.set_suppressed_flags(gst::ElementFlags::SINK | gst::ElementFlags::SOURCE);
        obj.set_element_flags(gst::ElementFlags::SINK);

        let state = self.state.lock().unwrap();
        obj.add(&state.appsink).unwrap();
        obj.add_pad(&state.sinkpad).unwrap();
        state
            .sinkpad
            .set_target(Some(&state.appsink.static_pad("sink").unwrap()))
            .unwrap();
    }
}

impl GstObjectImpl for InterSink {}

impl ElementImpl for InterSink {
    fn metadata() -> Option<&'static gst::subclass::ElementMetadata> {
        static ELEMENT_METADATA: Lazy<gst::subclass::ElementMetadata> = Lazy::new(|| {
            gst::subclass::ElementMetadata::new(
                "Inter Sink",
                "Generic/Sink",
                "Inter Sink",
                "Mathieu Duponchelle <mathieu@centricular.com>",
            )
        });

        Some(&*ELEMENT_METADATA)
    }

    fn pad_templates() -> &'static [gst::PadTemplate] {
        static PAD_TEMPLATES: Lazy<Vec<gst::PadTemplate>> = Lazy::new(|| {
            let caps = gst::Caps::new_any();

            let sink_pad_template = gst::PadTemplate::new(
                "sink",
                gst::PadDirection::Sink,
                gst::PadPresence::Always,
                &caps,
            )
            .unwrap();
            vec![sink_pad_template]
        });

        PAD_TEMPLATES.as_ref()
    }

    fn change_state(
        &self,
        transition: gst::StateChange,
    ) -> Result<gst::StateChangeSuccess, gst::StateChangeError> {
        gst::trace!(CAT, imp: self, "Changing state {:?}", transition);

        if transition == gst::StateChange::ReadyToPaused {
            if let Err(err) = self.prepare() {
                gst::element_error!(
                    self.obj(),
                    gst::StreamError::Failed,
                    ["Failed to prepare: {}", err]
                );
                return Err(gst::StateChangeError);
            }
        }

        let ret = self.parent_change_state(transition)?;

        if transition == gst::StateChange::PausedToReady {
            self.unprepare();
        }

        Ok(ret)
    }
}

impl BinImpl for InterSink {}