/*
 gifski pngquant-based GIF encoder
 © 2017 Kornel Lesiński

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU Affero General Public License as
 published by the Free Software Foundation, either version 3 of the
 License, or (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU Affero General Public License for more details.

 You should have received a copy of the GNU Affero General Public License
 along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
#![doc(html_logo_url = "https://gif.ski/icon.png")]

#[macro_use] extern crate quick_error;

use imagequant::*;
use imgref::*;
use rgb::*;

mod error;
pub use crate::error::*;
mod ordqueue;
use crate::ordqueue::*;
pub mod progress;
use crate::progress::*;
pub mod c_api;
mod encoderust;

#[cfg(feature = "gifsicle")]
mod encodegifsicle;

use std::io::prelude::*;
use std::path::PathBuf;
use std::sync::Arc;
use crossbeam_channel::{Sender, Receiver};
use std::thread;

type DecodedImage = CatResult<(ImgVec<RGBA8>, f64)>;

/// Encoding settings for the `new()` function
#[derive(Copy, Clone, Default)]
pub struct Settings {
    /// Resize to max this width if set
    pub width: Option<u32>,
    /// Resize to max this height if width is set. Note that aspect ratio is not preserved.
    pub height: Option<u32>,
    /// 1-100
    pub quality: u8,
    /// If true, looping is disabled
    pub once: bool,
    /// Lower quality, but faster encode
    pub fast: bool,
}

impl Settings {
    #[cfg(not(feature = "gifsicle"))]
    pub(crate) fn color_quality(&self) -> u8 {
        self.quality
    }

    #[cfg(feature = "gifsicle")]
    pub(crate) fn color_quality(&self) -> u8 {
        (self.quality * 2).min(100)
    }

    /// add_frame is going to resize the images to this size.
    pub fn dimensions_for_image(&self, width: usize, height: usize) -> (usize, usize) {
        dimensions_for_image((width, height), (self.width, self.height))
    }
}

/// Collect frames that will be encoded
///
/// Note that writing will finish only when the collector is dropped.
/// Collect frames on another thread, or call `drop(collector)` before calling `writer.write()`!
pub struct Collector {
    width: Option<u32>,
    height: Option<u32>,
    queue: OrdQueue<DecodedImage>,
}

/// Perform GIF writing
pub struct Writer {
    /// Input frame decoder results
    queue_iter: Option<OrdQueueIter<DecodedImage>>,
    settings: Settings,
}

struct GIFFrame {
    left: u16,
    top: u16,
    image: ImgVec<u8>,
    pal: Vec<RGBA8>,
    dispose: gif::DisposalMethod,
}

trait Encoder {
    fn write_frame(&mut self, frame: &GIFFrame, delay: u16, settings: &Settings) -> CatResult<()>;
    fn finish(&mut self) -> CatResult<()> {
        Ok(())
    }
}

/// Frame before quantization
struct DiffMessage {
    /// 1..
    ordinal_frame_number: usize,
    image: ImgVec<RGBA8>,
    importance_map: Vec<u8>,
    dispose: gif::DisposalMethod,
    pts: f64,
}

/// Frame post quantization
struct FrameMessage {
    /// 1..
    ordinal_frame_number: usize,
    frame: Arc<GIFFrame>,
    pts: f64,
}


/// Start new encoding
///
/// Encoding is multi-threaded, and the `Collector` and `Writer`
/// can be used on sepate threads.
///
/// You feed input frames to the `Collector`, and ask the `Writer` to
/// start writing the GIF.
pub fn new(settings: Settings) -> CatResult<(Collector, Writer)> {
    let (queue, queue_iter) = ordqueue::new(4);

    Ok((
        Collector {
            queue,
            width: settings.width,
            height: settings.height,
        },
        Writer {
            queue_iter: Some(queue_iter),
            settings,
        },
    ))
}

impl Collector {
    /// Frame index starts at 0.
    ///
    /// Set each frame (index) only once, but you can set them in any order.
    ///
    /// Presentation timestamp is time in seconds (since file start at 0) when this frame is to be displayed.
    ///
    /// If the first frame doesn't start at pts=0, the delay will be used for the last frame.
    pub fn add_frame_rgba(&mut self, frame_index: usize, image: ImgVec<RGBA8>, presentation_timestamp: f64) -> CatResult<()> {
        self.queue.push(frame_index, Ok((Self::resized_binary_alpha(image, self.width, self.height), presentation_timestamp)))
    }

    /// Read and decode a PNG file from disk.
    ///
    /// Frame index starts at 0.
    ///
    /// Presentation timestamp is time in seconds (since file start at 0) when this frame is to be displayed.
    ///
    /// If the first frame doesn't start at pts=0, the delay will be used for the last frame.
    pub fn add_frame_png_file(&mut self, frame_index: usize, path: PathBuf, presentation_timestamp: f64) -> CatResult<()> {
        let width = self.width;
        let height = self.height;
        let image = lodepng::decode32_file(&path)
            .map_err(|err| Error::PNG(format!("Can't load {}: {}", path.display(), err)))?;

        self.queue.push(frame_index, Ok((Self::resized_binary_alpha(ImgVec::new(image.buffer, image.width, image.height), width, height), presentation_timestamp)))
    }

    fn resized_binary_alpha(mut image: ImgVec<RGBA8>, width: Option<u32>, height: Option<u32>) -> ImgVec<RGBA8> {
        let (width, height) = dimensions_for_image((image.width(), image.height()), (width, height));

        if width != image.width() || height != image.height() {
            let (buf, img_width, img_height) = image.into_contiguous_buf();
            assert_eq!(buf.len(), img_width * img_height);

            let mut r = resize::new(img_width, img_height, width, height, resize::Pixel::RGBA, resize::Type::Lanczos3);
            let mut dst = vec![RGBA::new(0, 0, 0, 0); width * height];
            r.resize(buf.as_bytes(), dst.as_bytes_mut());
            image = ImgVec::new(dst, width, height)
        }

        const DITHER: [u8; 64] = [
         0*2+8,48*2+8,12*2+8,60*2+8, 3*2+8,51*2+8,15*2+8,63*2+8,
        32*2+8,16*2+8,44*2+8,28*2+8,35*2+8,19*2+8,47*2+8,31*2+8,
         8*2+8,56*2+8, 4*2+8,52*2+8,11*2+8,59*2+8, 7*2+8,55*2+8,
        40*2+8,24*2+8,36*2+8,20*2+8,43*2+8,27*2+8,39*2+8,23*2+8,
         2*2+8,50*2+8,14*2+8,62*2+8, 1*2+8,49*2+8,13*2+8,61*2+8,
        34*2+8,18*2+8,46*2+8,30*2+8,33*2+8,17*2+8,45*2+8,29*2+8,
        10*2+8,58*2+8, 6*2+8,54*2+8, 9*2+8,57*2+8, 5*2+8,53*2+8,
        42*2+8,26*2+8,38*2+8,22*2+8,41*2+8,25*2+8,37*2+8,21*2+8];

        // Make transparency binary
        for (y, row) in image.rows_mut().enumerate() {
            for (x, px) in row.iter_mut().enumerate() {
                if px.a < 255 {
                    px.a = if px.a < DITHER[(y & 7) * 8 + (x & 7)] { 0 } else { 255 };
                }
            }
        }
        image
    }
}

/// add_frame is going to resize the image to this size.
/// The `Option` args are user-specified max width and max height
fn dimensions_for_image((img_w, img_h): (usize, usize), resize_to: (Option<u32>, Option<u32>)) -> (usize, usize) {
    match resize_to {
        (None, None) => {
            let factor = (img_w * img_h + 800*600) / (800*600);
            if factor > 1 {
                (img_w / factor, img_h / factor)
            } else {
                (img_w, img_h)
            }
        },
        (Some(w), Some(h)) => {
            ((w as usize).min(img_w), (h as usize).min(img_h))
        },
        (Some(w), None) => {
            let w = (w as usize).min(img_w);
            (w, img_h * w / img_w)
        }
        (None, Some(h)) => {
            let h = (h as usize).min(img_h);
            (img_w * h / img_h, h)
        },
    }
}

/// Encode collected frames
impl Writer {
    /// `importance_map` is computed from previous and next frame.
    /// Improves quality of pixels visible for longer.
    /// Avoids wasting palette on pixels identical to the background.
    ///
    /// `background` is the previous frame.
    fn quantize(image: ImgRef<'_, RGBA8>, importance_map: &[u8], background: Option<ImgRef<'_, RGBA8>>, settings: &Settings) -> CatResult<(ImgVec<u8>, Vec<RGBA8>)> {
        let mut liq = Attributes::new();
        if settings.fast {
            liq.set_speed(10);
        }
        let quality = if background.is_some() { // not first frame
            settings.color_quality().into()
        } else {
            100 // the first frame is too important to ruin it
        };
        liq.set_quality(0, quality);
        let mut img = liq.new_image_stride(image.buf(), image.width(), image.height(), image.stride(), 0.)?;
        img.set_importance_map(importance_map)?;
        if let Some(bg) = background {
            assert_eq!(bg.width(), bg.stride());
            img.set_background(liq.new_image(bg.buf(), bg.width(), bg.height(), 0.)?)?;
        }
        img.add_fixed_color(RGBA8::new(0, 0, 0, 0));
        let mut res = liq.quantize(&img)?;
        res.set_dithering_level(0.5);

        let (pal, pal_img) = res.remapped(&mut img)?;
        debug_assert_eq!(img.width() * img.height(), pal_img.len());

        Ok((Img::new(pal_img, img.width(), img.height()), pal))
    }

    fn write_frames(write_queue: Receiver<FrameMessage>, enc: &mut dyn Encoder, settings: &Settings, reporter: &mut dyn ProgressReporter) -> CatResult<()> {
        let mut write_queue = write_queue
            .into_iter()
            .peekable();

        let mut previous_frame_delay = 3;
        let mut last_frame_delay_s = None;
        let mut pts_in_delay_units = 0_u64;

        if let Some(&FrameMessage {pts, ..}) = write_queue.peek() {
            // If the first frame doesn't start at 0 (or actually with 1/100th because that's min delay)
            // interpret it as the delay between (looped) the last and the first frame.
            if pts >= 1./100. {
                last_frame_delay_s = Some(pts);
                // Shift all frames by this pts so that frame 0 always starts at 0
                pts_in_delay_units = (100. * pts).floor() as _;
            }
            }

        let mut n_done = 0;
        while let Some(FrameMessage {frame, ordinal_frame_number, ..}) = write_queue.next() {
            let next_frame = write_queue.peek();

            // To convert PTS to delay it's necessary to know when the next frame is to be displayed
            let delay = if let Some(next_pts) = next_frame.as_ref().map(|m| m.pts).or_else(|| {
                    last_frame_delay_s.map(|s| pts_in_delay_units as f64 / 100.0 + s)
                }) {
                let next_pts_in_delay_units = (next_pts * 100.0).round() as u64;
                next_pts_in_delay_units.saturating_sub(pts_in_delay_units).min(10000) as u16
            } else {
                // for the last frame just assume constant framerate
                previous_frame_delay
            };
            pts_in_delay_units += u64::from(delay);
            previous_frame_delay = delay;

            // skip frames with bad pts
            if delay != 0 {
                enc.write_frame(&frame, delay, settings)?;
            }

            // loop to report skipped frames too
            while n_done < ordinal_frame_number {
                n_done += 1;
                if !reporter.increase() {
                    return Err(Error::Aborted.into());
                }
            }
        }
        enc.finish()?;
        Ok(())
    }

    /// Start writing frames. This function will not return until `Collector` is dropped.
    ///
    /// `outfile` can be any writer, such as `File` or `&mut Vec`.
    ///
    /// `ProgressReporter.increase()` is called each time a new frame is being written.
    #[allow(unused_mut)]
    pub fn write<W: Write>(self, mut writer: W, reporter: &mut dyn ProgressReporter) -> CatResult<()> {

        #[cfg(feature = "gifsicle")]
        {
            let encoder: &mut dyn Encoder;
            let mut gifsicle;
            let mut rustgif;
            if self.settings.quality < 100 {
                let loss = (100 - self.settings.quality as u32) * 6;
                gifsicle = encodegifsicle::Gifsicle::new(loss, &mut writer);
                encoder = &mut gifsicle;
            } else {
                rustgif = encoderust::RustEncoder::new(writer);
                encoder = &mut rustgif;
            }
            self.write_with_encoder(encoder, reporter)
        }
        #[cfg(not(feature = "gifsicle"))]
        {
            self.write_with_encoder(&mut encoderust::RustEncoder::new(writer), reporter)
        }
    }

    fn write_with_encoder(mut self, encoder: &mut dyn Encoder, reporter: &mut dyn ProgressReporter) -> CatResult<()> {
        let decode_queue_recv = self.queue_iter.take().expect("queue");
        let (quant_queue, quant_queue_recv) = crossbeam_channel::bounded(4);
        let settings = self.settings;
        let diff_thread = thread::spawn(move || {
            Self::make_diffs(decode_queue_recv, quant_queue, &settings)
        });
        let (write_queue, write_queue_recv) = crossbeam_channel::bounded(4);
        let quant_thread = thread::spawn(move || {
            Self::quantize_frames(quant_queue_recv, write_queue, &settings)
        });
        Self::write_frames(write_queue_recv, encoder, &self.settings, reporter)?;
        diff_thread.join().map_err(|_| Error::ThreadSend)??;
        quant_thread.join().map_err(|_| Error::ThreadSend)??;
        Ok(())
    }

    fn make_diffs(mut inputs: OrdQueueIter<DecodedImage>, quant_queue: Sender<DiffMessage>, _settings: &Settings) -> CatResult<()> {
        let mut next_frame = inputs.next().transpose()?;

        let mut ordinal_frame_number = 0;
        while let Some((image, pts)) = {
            // that's not the while loop, that block gets the next element
            let curr_frame = next_frame.take();
            next_frame = inputs.next().transpose()?;
            curr_frame
        } {
            ordinal_frame_number += 1;

            let mut dispose = gif::DisposalMethod::Keep;
            let importance_map = if let Some((next, _)) = &next_frame {
                if next.width() != image.width() || next.height() != image.height() {
                    return Err(Error::WrongSize(format!("Frame {} has wrong size ({}×{}, expected {}×{})", ordinal_frame_number,
                        next.width(), next.height(), image.width(), image.height())));
                }

                // Skip identical frames
                if next.as_ref() == image.as_ref() {
                    continue;
                }

                let mut importance_map = Vec::with_capacity(image.width() * image.height());
                importance_map.extend(next.rows().zip(image.rows()).flat_map(|(n, curr)| n.iter().copied().zip(curr.iter().copied())).map(|(n, curr)| {
                    if n.a < curr.a {
                        dispose = gif::DisposalMethod::Background;
                    }
                    // Even if next frame completely overwrites it, it's still somewhat important to display current one
                    // but pixels that will stay unchanged should have higher quality
                    255 - (colordiff(n, curr) / (255 * 255 * 6 / 170)) as u8
                }));
                importance_map
            } else {
                // Last frame should reset to background to avoid breaking transparent looped anims
                dispose = gif::DisposalMethod::Background;
                // Dunno? Maybe compare with the first frame?
                vec![255; image.width() * image.height()]
            };

            quant_queue.send(DiffMessage {
                dispose,
                importance_map,
                ordinal_frame_number,
                image,
                pts,
            })?;
        }

        Ok(())
    }

    fn quantize_frames(inputs: Receiver<DiffMessage>, write_queue: Sender<FrameMessage>, settings: &Settings) -> CatResult<()> {
        let mut screen = None;
        let next_frame = inputs.recv().map_err(|_| Error::NoFrames)?;

        let mut next_frame = Some(next_frame);

        let mut previous_frame_dispose = gif::DisposalMethod::Background;
        let mut frames_written = 0;
        while let Some(DiffMessage {image, pts, dispose, ordinal_frame_number, mut importance_map}) = {
            // that's not the while loop, that block gets the next element
            let curr_frame = next_frame.take();
            next_frame = inputs.recv().ok();
            curr_frame
        } {

            let screen = screen.get_or_insert_with(|| gif_dispose::Screen::new(image.width(), image.height(), RGBA8::new(0, 0, 0, 0), None));

            let has_prev_frame = frames_written > 0 && previous_frame_dispose == gif::DisposalMethod::Keep;
            if has_prev_frame {
                let q = 100 - u32::from(settings.color_quality());
                let min_diff = 80 + q * q;
                debug_assert_eq!(image.width(), screen.pixels.width());
                importance_map
                    .chunks_exact_mut(image.width())
                    .zip(screen.pixels.rows().zip(image.rows()))
                    .flat_map(|(imp, (bg, px))| {
                        imp.iter_mut().zip(bg.iter().copied().zip(px.iter().copied()))
                    })
                    .for_each(|(imp, (bg, px))| {
                        // TODO: try comparing with max-quality dithered non-transparent frame, but at half res to avoid dithering confusing the results
                        // and pick pixels/areas that are better left transparent?

                        let diff = colordiff(bg, px);
                        // if pixels are close or identical, no weight on them
                        *imp = if diff < min_diff {
                            0
                        } else {
                            // clip max value, since if something's different it doesn't matter how much, it has to be displayed anyway
                            // but multiply by previous map last, since it already decided non-max value
                            let t = diff / 32;
                            ((t * t).min(256) as u16 * u16::from(*imp) / 256) as u8
                        }
                    });
            }
            previous_frame_dispose = dispose;

            let (image8, image8_pal) = {
                let bg = if has_prev_frame { Some(screen.pixels.as_ref()) } else { None };
                Self::quantize(image.as_ref(), &importance_map, bg, settings)?
            };

            drop(image);

            let transparent_index = image8_pal.iter().position(|p| p.a == 0).map(|i| i as u8);

            let (left, top, image8) = match trim_image(image8, &image8_pal, transparent_index, screen.pixels.as_ref()) {
                Some(trimmed) => trimmed,
                None => continue, // no pixels left
            };

            let frame = Arc::new(GIFFrame {
                left,
                top,
                image: image8,
                pal: image8_pal,
                dispose,
            });

            write_queue.send(FrameMessage {
                ordinal_frame_number,
                pts,
                frame: frame.clone()
            })?;
            frames_written += 1;
            screen.blit(Some(&frame.pal), dispose, left, top as _, frame.image.as_ref(), transparent_index)?;
        }

        Ok(())
    }
}

fn trim_image(mut image8: ImgVec<u8>, image8_pal: &[RGBA8], transparent_index: Option<u8>, screen: ImgRef<RGBA8>) -> Option<(u16, u16, ImgVec<u8>)> {
    let mut image_trimmed = image8.as_ref();

    let bottom = image_trimmed.rows().zip(screen.rows()).rev()
        .take_while(|(img_row, screen_row)| {
            img_row.iter().copied().zip(screen_row.iter().copied())
                .all(|(px, bg)| {
                    Some(px) == transparent_index || image8_pal.get(px as usize) == Some(&bg)
                })
        })
        .count();

    if bottom > 0 {
        if bottom == image_trimmed.height() {
            return None;
        }
        image_trimmed = image_trimmed.sub_image(0, 0, image_trimmed.width(), image_trimmed.height() - bottom);
    }

    let top = image_trimmed.rows().zip(screen.rows())
        .take_while(|(img_row, screen_row)| {
            img_row.iter().copied().zip(screen_row.iter().copied())
                .all(|(px, bg)| {
                    Some(px) == transparent_index || image8_pal.get(px as usize) == Some(&bg)
                })
        })
        .count();

    if top > 0 {
        image_trimmed = image_trimmed.sub_image(0, top, image_trimmed.width(), image_trimmed.height() - top);
    }

    if image_trimmed.height() != image8.height() {
        let (buf, width, height) = image_trimmed.to_contiguous_buf();
        image8 = Img::new(buf.into_owned(), width, height);
    }

    Some((0, top as _, image8))
}

#[inline]
fn colordiff(a: RGBA8, b: RGBA8) -> u32 {
    if a.a == 0 || b.a == 0 {
        return 255 * 255 * 6;
    }
    (i32::from(i16::from(a.r) - i16::from(b.r)) * i32::from(i16::from(a.r) - i16::from(b.r))) as u32 * 2 +
    (i32::from(i16::from(a.g) - i16::from(b.g)) * i32::from(i16::from(a.g) - i16::from(b.g))) as u32 * 3 +
    (i32::from(i16::from(a.b) - i16::from(b.b)) * i32::from(i16::from(a.b) - i16::from(b.b))) as u32
}