// Take a look at the license at the top of the repository in the LICENSE file.

use std::borrow::Cow;

use glib::{prelude::*, subclass::prelude::*, translate::*};

use super::prelude::*;
use crate::{ffi, Device, DeviceProvider, LoggableError};

#[derive(Debug, Clone)]
pub struct DeviceProviderMetadata {
    long_name: Cow<'static, str>,
    classification: Cow<'static, str>,
    description: Cow<'static, str>,
    author: Cow<'static, str>,
    additional: Cow<'static, [(Cow<'static, str>, Cow<'static, str>)]>,
}

impl DeviceProviderMetadata {
    pub fn new(long_name: &str, classification: &str, description: &str, author: &str) -> Self {
        Self {
            long_name: Cow::Owned(long_name.into()),
            classification: Cow::Owned(classification.into()),
            description: Cow::Owned(description.into()),
            author: Cow::Owned(author.into()),
            additional: Cow::Borrowed(&[]),
        }
    }

    pub fn with_additional(
        long_name: &str,
        classification: &str,
        description: &str,
        author: &str,
        additional: &[(&str, &str)],
    ) -> Self {
        Self {
            long_name: Cow::Owned(long_name.into()),
            classification: Cow::Owned(classification.into()),
            description: Cow::Owned(description.into()),
            author: Cow::Owned(author.into()),
            additional: additional
                .iter()
                .copied()
                .map(|(key, value)| (Cow::Owned(key.into()), Cow::Owned(value.into())))
                .collect(),
        }
    }

    pub const fn with_cow(
        long_name: Cow<'static, str>,
        classification: Cow<'static, str>,
        description: Cow<'static, str>,
        author: Cow<'static, str>,
        additional: Cow<'static, [(Cow<'static, str>, Cow<'static, str>)]>,
    ) -> Self {
        Self {
            long_name,
            classification,
            description,
            author,
            additional,
        }
    }
}

pub trait DeviceProviderImpl: DeviceProviderImplExt + GstObjectImpl + Send + Sync {
    fn metadata() -> Option<&'static DeviceProviderMetadata> {
        None
    }

    /// Returns a list of devices that are currently available.
    ///  This should never block. The devices should not have a parent and should
    ///  be floating.
    fn probe(&self) -> Vec<Device> {
        self.parent_probe()
    }

    /// Starts providering the devices. This will cause `GST_MESSAGE_DEVICE_ADDED`
    /// and `GST_MESSAGE_DEVICE_REMOVED` messages to be posted on the provider's bus
    /// when devices are added or removed from the system.
    ///
    /// Since the [`DeviceProvider`][crate::DeviceProvider] is a singleton,
    /// [`DeviceProviderExt::start()`][crate::prelude::DeviceProviderExt::start()] may already have been called by another
    /// user of the object, [`DeviceProviderExt::stop()`][crate::prelude::DeviceProviderExt::stop()] needs to be called the same
    /// number of times.
    ///
    /// After this function has been called, [`DeviceProviderExtManual::devices()`][crate::prelude::DeviceProviderExtManual::devices()] will
    /// return the same objects that have been received from the
    /// `GST_MESSAGE_DEVICE_ADDED` messages and will no longer probe.
    ///
    /// # Returns
    ///
    /// [`true`] if the device providering could be started
    fn start(&self) -> Result<(), LoggableError> {
        self.parent_start()
    }

    /// Decreases the use-count by one. If the use count reaches zero, this
    /// [`DeviceProvider`][crate::DeviceProvider] will stop providering the devices. This needs to be
    /// called the same number of times that [`DeviceProviderExt::start()`][crate::prelude::DeviceProviderExt::start()] was called.
    fn stop(&self) {
        self.parent_stop()
    }
}

mod sealed {
    pub trait Sealed {}
    impl<T: super::DeviceProviderImplExt> Sealed for T {}
}

pub trait DeviceProviderImplExt: sealed::Sealed + ObjectSubclass {
    fn parent_probe(&self) -> Vec<Device> {
        unsafe {
            let data = Self::type_data();
            let parent_class = data.as_ref().parent_class() as *mut ffi::GstDeviceProviderClass;
            if let Some(f) = (*parent_class).probe {
                FromGlibPtrContainer::from_glib_full(f(self
                    .obj()
                    .unsafe_cast_ref::<DeviceProvider>()
                    .to_glib_none()
                    .0))
            } else {
                Vec::new()
            }
        }
    }

    fn parent_start(&self) -> Result<(), LoggableError> {
        unsafe {
            let data = Self::type_data();
            let parent_class = data.as_ref().parent_class() as *mut ffi::GstDeviceProviderClass;
            let f = (*parent_class).start.ok_or_else(|| {
                loggable_error!(crate::CAT_RUST, "Parent function `start` is not defined")
            })?;
            result_from_gboolean!(
                f(self
                    .obj()
                    .unsafe_cast_ref::<DeviceProvider>()
                    .to_glib_none()
                    .0),
                crate::CAT_RUST,
                "Failed to start the device provider using the parent function"
            )
        }
    }

    fn parent_stop(&self) {
        unsafe {
            let data = Self::type_data();
            let parent_class = data.as_ref().parent_class() as *mut ffi::GstDeviceProviderClass;
            if let Some(f) = (*parent_class).stop {
                f(self
                    .obj()
                    .unsafe_cast_ref::<DeviceProvider>()
                    .to_glib_none()
                    .0);
            }
        }
    }
}

impl<T: DeviceProviderImpl> DeviceProviderImplExt for T {}

unsafe impl<T: DeviceProviderImpl> IsSubclassable<T> for DeviceProvider {
    fn class_init(klass: &mut glib::Class<Self>) {
        Self::parent_class_init::<T>(klass);
        let klass = klass.as_mut();
        klass.probe = Some(device_provider_probe::<T>);
        klass.start = Some(device_provider_start::<T>);
        klass.stop = Some(device_provider_stop::<T>);

        unsafe {
            if let Some(metadata) = T::metadata() {
                ffi::gst_device_provider_class_set_metadata(
                    klass,
                    metadata.long_name.to_glib_none().0,
                    metadata.classification.to_glib_none().0,
                    metadata.description.to_glib_none().0,
                    metadata.author.to_glib_none().0,
                );

                for (key, value) in metadata.additional.iter() {
                    ffi::gst_device_provider_class_add_metadata(
                        klass,
                        key.to_glib_none().0,
                        value.to_glib_none().0,
                    );
                }
            }
        }
    }
}

unsafe extern "C" fn device_provider_probe<T: DeviceProviderImpl>(
    ptr: *mut ffi::GstDeviceProvider,
) -> *mut glib::ffi::GList {
    let instance = &*(ptr as *mut T::Instance);
    let imp = instance.imp();

    imp.probe().to_glib_full()
}

unsafe extern "C" fn device_provider_start<T: DeviceProviderImpl>(
    ptr: *mut ffi::GstDeviceProvider,
) -> glib::ffi::gboolean {
    let instance = &*(ptr as *mut T::Instance);
    let imp = instance.imp();

    match imp.start() {
        Ok(()) => true,
        Err(err) => {
            err.log_with_imp(imp);
            false
        }
    }
    .into_glib()
}

unsafe extern "C" fn device_provider_stop<T: DeviceProviderImpl>(ptr: *mut ffi::GstDeviceProvider) {
    let instance = &*(ptr as *mut T::Instance);
    let imp = instance.imp();

    imp.stop();
}