use std::collections::HashMap;
use std::{ptr, slice};

use crate::{bail_ffmpeg, get_ffmpeg_error_msg, options_to_dict};
use anyhow::{bail, Error};
use ffmpeg_sys_the_third::{
    av_channel_layout_default, av_d2q, av_inv_q, av_packet_alloc, av_packet_free,
    avcodec_alloc_context3, avcodec_find_encoder, avcodec_free_context,
    avcodec_get_supported_config, avcodec_open2, avcodec_receive_packet, avcodec_send_frame,
    AVChannelLayout, AVCodec, AVCodecConfig, AVCodecContext, AVCodecID, AVFrame, AVPacket,
    AVPixelFormat, AVRational, AVSampleFormat, AVERROR, AVERROR_EOF,
};
use libc::EAGAIN;

pub struct Encoder {
    ctx: *mut AVCodecContext,
    codec: *const AVCodec,
    dst_stream_index: Option<i32>,
}

impl Drop for Encoder {
    fn drop(&mut self) {
        unsafe {
            if !self.ctx.is_null() {
                avcodec_free_context(&mut self.ctx);
            }
        }
    }
}

impl Encoder {
    /// Create a new encoder with the specified codec
    pub fn new(codec: AVCodecID) -> Result<Self, Error> {
        unsafe {
            let codec = avcodec_find_encoder(codec);
            if codec.is_null() {
                bail!("codec not found");
            }
            let ctx = avcodec_alloc_context3(codec);
            if ctx.is_null() {
                bail!("context allocation failed");
            }
            // set some defaults
            (*ctx).time_base = AVRational { num: 1, den: 1 };
            Ok(Self {
                ctx,
                codec,
                dst_stream_index: None,
            })
        }
    }

    /// Get the codec
    pub fn codec(&self) -> *const AVCodec {
        self.codec
    }

    /// Get the codec context
    pub fn codec_context(&self) -> *const AVCodecContext {
        self.ctx
    }

    /// List supported configs (see [avcodec_get_supported_config])
    pub unsafe fn list_configs<'a, T>(&mut self, cfg: AVCodecConfig) -> Result<&'a [T], Error> {
        let mut dst = ptr::null_mut();
        let mut num_dst = 0;
        let ret = avcodec_get_supported_config(
            self.ctx,
            self.codec,
            cfg,
            0,
            ptr::addr_of_mut!(dst) as _,
            &mut num_dst,
        );
        bail_ffmpeg!(ret);
        Ok(slice::from_raw_parts(dst, num_dst as usize))
    }

    /// Store the destination stream index along with the encoder
    /// AVPacket's created by this encoder will have stream_index assigned to this value
    pub unsafe fn with_stream_index(mut self, index: i32) -> Self {
        self.dst_stream_index = Some(index);
        self
    }

    /// Set the encoder bitrate
    pub unsafe fn with_bitrate(self, bitrate: i64) -> Self {
        (*self.ctx).bit_rate = bitrate;
        self
    }

    /// Set the encoder sample rate (audio)
    pub unsafe fn with_sample_rate(self, fmt: i32) -> Self {
        (*self.ctx).sample_rate = fmt;
        self
    }

    /// Set the encoder width in pixels
    pub unsafe fn with_width(self, width: i32) -> Self {
        (*self.ctx).width = width;
        self
    }

    /// Set the encoder height in pixels
    pub unsafe fn with_height(self, height: i32) -> Self {
        (*self.ctx).height = height;
        self
    }

    /// Set the encoder level (see AV_LEVEL_*)
    pub unsafe fn with_level(self, level: i32) -> Self {
        (*self.ctx).level = level;
        self
    }

    /// Set the encoder profile (see AV_PROFILE_*)
    pub unsafe fn with_profile(self, profile: i32) -> Self {
        (*self.ctx).profile = profile;
        self
    }

    /// Set the encoder framerate
    pub unsafe fn with_framerate(self, fps: f32) -> Self {
        let q = av_d2q(fps as f64, 90_000);
        (*self.ctx).framerate = q;
        (*self.ctx).time_base = av_inv_q(q);
        self
    }

    /// Set the encoder pixel format
    pub unsafe fn with_pix_fmt(self, fmt: AVPixelFormat) -> Self {
        (*self.ctx).pix_fmt = fmt;
        self
    }

    /// Set the encoder sample format (audio)
    pub unsafe fn with_sample_format(self, fmt: AVSampleFormat) -> Self {
        (*self.ctx).sample_fmt = fmt;
        self
    }

    /// Set the encoder channel layout (audio)
    pub unsafe fn with_channel_layout(self, layout: AVChannelLayout) -> Self {
        (*self.ctx).ch_layout = layout;
        self
    }

    /// Set the encoder channel layout using number of channels (audio)
    pub unsafe fn with_default_channel_layout(self, channels: i32) -> Self {
        let mut layout = AVChannelLayout::empty();
        av_channel_layout_default(&mut layout, channels);
        (*self.ctx).ch_layout = layout;
        self
    }

    /// Apply options to context
    pub unsafe fn with_options<F>(self, fx: F) -> Self
    where
        F: FnOnce(*mut AVCodecContext),
    {
        fx(self.ctx);
        self
    }

    /// Open the encoder so that you can start encoding frames (see [avcodec_open2])
    pub unsafe fn open(self, options: Option<HashMap<String, String>>) -> Result<Self, Error> {
        assert!(!self.ctx.is_null());

        let mut options = if let Some(options) = options {
            options_to_dict(options)?
        } else {
            ptr::null_mut()
        };
        let ret = avcodec_open2(self.ctx, self.codec, &mut options);
        bail_ffmpeg!(ret);
        Ok(self)
    }

    /// Encode a frame, returning a number of [AVPacket]
    pub unsafe fn encode_frame(
        &mut self,
        frame: *mut AVFrame,
    ) -> Result<Vec<*mut AVPacket>, Error> {
        let mut pkgs = Vec::new();

        let mut ret = avcodec_send_frame(self.ctx, frame);
        if ret < 0 && ret != AVERROR(EAGAIN) {
            bail!(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) || ret == AVERROR_EOF {
                    break;
                }
                bail!(get_ffmpeg_error_msg(ret));
            }
            (*pkt).time_base = (*self.ctx).time_base;
            if let Some(idx) = self.dst_stream_index {
                (*pkt).stream_index = idx;
            }
            pkgs.push(pkt);
        }

        Ok(pkgs)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::generate_test_frame;
    use std::io::Write;

    #[test]
    fn test_encode_png() -> Result<(), Error> {
        unsafe {
            let frame = generate_test_frame();
            let mut encoder = Encoder::new(AVCodecID::AV_CODEC_ID_PNG)?
                .with_width((*frame).width)
                .with_height((*frame).height);

            let pix_fmts: &[AVPixelFormat] =
                encoder.list_configs(AVCodecConfig::AV_CODEC_CONFIG_PIX_FORMAT)?;
            encoder = encoder.with_pix_fmt(pix_fmts[0]).open(None)?;

            std::fs::create_dir_all("test_output")?;
            let mut test_file = std::fs::File::create("test_output/test.png")?;
            let mut pkts = encoder.encode_frame(frame)?;
            let flush_pkts = encoder.encode_frame(ptr::null_mut())?;
            pkts.extend(flush_pkts);
            for pkt in pkts {
                test_file.write(slice::from_raw_parts((*pkt).data, (*pkt).size as usize))?;
            }
        }
        Ok(())
    }
}