use std::mem::transmute;
use std::ptr;

use anyhow::Error;
use ffmpeg_sys_next::{
    av_buffer_ref, av_packet_alloc, av_packet_free, AVBufferRef,
    AVCodec, avcodec_alloc_context3, avcodec_find_encoder, avcodec_open2, avcodec_receive_packet,
    avcodec_send_frame, AVCodecContext, AVERROR, AVFrame, AVStream,
};
use libc::EAGAIN;
use tokio::sync::mpsc::UnboundedSender;

use crate::encode::set_encoded_pkt_timing;
use crate::ipc::Rx;
use crate::pipeline::{PipelinePayload, PipelineProcessor};
use crate::utils::{get_ffmpeg_error_msg, id_ref_to_uuid, video_variant_id_ref};
use crate::variant::{VariantStreamType, VideoVariant};

pub struct VideoEncoder<T> {
    variant: VideoVariant,
    ctx: *mut AVCodecContext,
    codec: *const AVCodec,
    chan_in: T,
    chan_out: UnboundedSender<PipelinePayload>,
    var_id_ref: *mut AVBufferRef,
    pts: i64,
}

unsafe impl<T> Send for VideoEncoder<T> {}

unsafe impl<T> Sync for VideoEncoder<T> {}

impl<TRecv> VideoEncoder<TRecv>
where
    TRecv: Rx<PipelinePayload>,
{
    pub fn new(
        chan_in: TRecv,
        chan_out: UnboundedSender<PipelinePayload>,
        variant: VideoVariant,
    ) -> Self {
        let id_ref = video_variant_id_ref(&variant);
        Self {
            ctx: ptr::null_mut(),
            codec: ptr::null(),
            variant,
            chan_in,
            chan_out,
            var_id_ref: id_ref,
            pts: 0,
        }
    }

    unsafe fn setup_encoder(&mut self, frame: *mut AVFrame) -> Result<(), Error> {
        if self.ctx.is_null() {
            let codec = self.variant.codec;
            let encoder = avcodec_find_encoder(transmute(codec as i32));
            if encoder.is_null() {
                return Err(Error::msg("Encoder not found"));
            }

            let ctx = avcodec_alloc_context3(encoder);
            if ctx.is_null() {
                return Err(Error::msg("Failed to allocate encoder context"));
            }

            self.variant.to_codec_context(ctx);

            let ret = avcodec_open2(ctx, encoder, ptr::null_mut());
            if ret < 0 {
                return Err(Error::msg(get_ffmpeg_error_msg(ret)));
            }

            self.ctx = ctx;
            self.codec = encoder;
        }
        Ok(())
    }

    unsafe fn process_frame(&mut self, frame: *mut AVFrame) -> Result<(), Error> {
        let var_id = id_ref_to_uuid((*frame).opaque_ref)?;
        assert_eq!(var_id, self.variant.id);
        self.setup_encoder(frame)?;
        let in_stream = (*frame).opaque as *mut AVStream;

        let mut ret = avcodec_send_frame(self.ctx, frame);
        if ret < 0 && ret != AVERROR(EAGAIN) {
            return Err(Error::msg(get_ffmpeg_error_msg(ret)));
        }

        while ret > 0 || ret == AVERROR(EAGAIN) {
            let mut pkt = av_packet_alloc();
            ret = avcodec_receive_packet(self.ctx, pkt);
            if ret != 0 {
                av_packet_free(&mut pkt);
                if ret == AVERROR(EAGAIN) {
                    return Ok(());
                }
                return Err(Error::msg(get_ffmpeg_error_msg(ret)));
            }

            set_encoded_pkt_timing(self.ctx, pkt, in_stream, &mut self.pts, &self.variant);
            (*pkt).opaque = self.ctx as *mut libc::c_void;
            (*pkt).opaque_ref = av_buffer_ref(self.var_id_ref);
            assert_ne!((*pkt).data, ptr::null_mut());
            self.chan_out.send(PipelinePayload::AvPacket(
                "Video Encoder packet".to_owned(),
                pkt,
            ))?;
        }

        Ok(())
    }
}

impl<TRecv> PipelineProcessor for VideoEncoder<TRecv>
where
    TRecv: Rx<PipelinePayload>,
{
    fn process(&mut self) -> Result<(), Error> {
        while let Ok(pkg) = self.chan_in.try_recv_next() {
            match pkg {
                PipelinePayload::AvFrame(_, frm, idx) => unsafe {
                    if self.variant.src_index == idx {
                        self.process_frame(frm)?;
                    }
                },
                _ => return Err(Error::msg("Payload not supported")),
            }
        }
        Ok(())
    }
}