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use anyhow::Result;
use image::{imageops::FilterType, DynamicImage};
use libc::{
    c_void, ioctl, poll, pollfd, read, tcgetattr, tcsetattr, termios, winsize, ECHO, ICANON,
    POLLIN, STDIN_FILENO, STDOUT_FILENO, TCSANOW, TIOCGWINSZ,
};
use std::io::{stdout, Write};
use std::time::Instant;

pub struct KittyBackend {}

impl KittyBackend {
    pub fn new() -> Self {
        Self {}
    }

    pub fn supported() -> bool {
        // save terminal attributes and disable canonical input processing mode
        let old_attributes = unsafe {
            let mut old_attributes: termios = std::mem::zeroed();
            tcgetattr(STDIN_FILENO, &mut old_attributes);

            let mut new_attributes = old_attributes;
            new_attributes.c_lflag &= !ICANON;
            new_attributes.c_lflag &= !ECHO;
            tcsetattr(STDIN_FILENO, TCSANOW, &new_attributes);
            old_attributes
        };

        // generate red rgba test image
        let mut test_image = Vec::<u8>::with_capacity(32 * 32 * 4);
        test_image.extend(
            std::iter::repeat([255, 0, 0, 255].iter())
                .take(32 * 32)
                .flatten(),
        );

        // print the test image with the action set to query
        print!(
            "\x1B_Gi=1,f=32,s=32,v=32,a=q;{}\x1B\\",
            base64::encode(&test_image)
        );
        stdout().flush().unwrap();

        let start_time = Instant::now();
        let mut stdin_pollfd = pollfd {
            fd: STDIN_FILENO,
            events: POLLIN,
            revents: 0,
        };
        let allowed_bytes = [0x1B, b'_', b'G', b'\\'];
        let mut buf = Vec::<u8>::new();
        loop {
            // check for timeout while polling to avoid blocking the main thread
            while unsafe { poll(&mut stdin_pollfd, 1, 0) < 1 } {
                if start_time.elapsed().as_millis() > 50 {
                    unsafe {
                        tcsetattr(STDIN_FILENO, TCSANOW, &old_attributes);
                    }
                    return false;
                }
            }
            let mut byte = 0;
            unsafe {
                read(STDIN_FILENO, &mut byte as *mut _ as *mut c_void, 1);
            }
            if allowed_bytes.contains(&byte) {
                buf.push(byte);
            }
            if buf.starts_with(&[0x1B, b'_', b'G']) && buf.ends_with(&[0x1B, b'\\']) {
                unsafe {
                    tcsetattr(STDIN_FILENO, TCSANOW, &old_attributes);
                }
                return true;
            }
        }
    }
}

impl Default for KittyBackend {
    fn default() -> Self {
        Self::new()
    }
}

impl super::ImageBackend for KittyBackend {
    fn add_image(
        &self,
        lines: Vec<String>,
        image: &DynamicImage,
        _colors: usize,
    ) -> Result<String> {
        let tty_size = unsafe {
            let tty_size: winsize = std::mem::zeroed();
            ioctl(STDOUT_FILENO, TIOCGWINSZ, &tty_size);
            tty_size
        };
        let width_ratio = f64::from(tty_size.ws_col) / f64::from(tty_size.ws_xpixel);
        let height_ratio = f64::from(tty_size.ws_row) / f64::from(tty_size.ws_ypixel);

        // resize image to fit the text height with the Lanczos3 algorithm
        let image = image.resize(
            u32::max_value(),
            (lines.len() as f64 / height_ratio) as u32,
            FilterType::Lanczos3,
        );
        let _image_columns = width_ratio * f64::from(image.width());
        let image_rows = height_ratio * f64::from(image.height());

        // convert the image to rgba samples
        let rgba_image = image.to_rgba8();
        let flat_samples = rgba_image.as_flat_samples();
        let raw_image = flat_samples
            .image_slice()
            .expect("Conversion from image to rgba samples failed");
        assert_eq!(
            image.width() as usize * image.height() as usize * 4,
            raw_image.len()
        );

        let encoded_image = base64::encode(raw_image); // image data is base64 encoded
        let mut image_data = Vec::<u8>::new();
        for chunk in encoded_image.as_bytes().chunks(4096) {
            // send a 4096 byte chunk of base64 encoded rgba image data
            image_data.extend(
                format!(
                    "\x1B_Gf=32,s={},v={},m=1,a=T;",
                    image.width(),
                    image.height()
                )
                .as_bytes(),
            );
            image_data.extend(chunk);
            image_data.extend(b"\x1B\\");
        }
        image_data.extend(b"\x1B_Gm=0;\x1B\\"); // write empty last chunk
        image_data.extend(format!("\x1B[{}A", image_rows as u32 - 1).as_bytes()); // move cursor to start of image
        let mut i = 0;
        for line in &lines {
            image_data.extend(format!("\x1B[s{}\x1B[u\x1B[1B", line).as_bytes());
            i += 1;
        }
        image_data
            .extend(format!("\n\x1B[{}B", lines.len().max(image_rows as usize) - i).as_bytes()); // move cursor to end of image

        Ok(String::from_utf8(image_data)?)
    }
}