use libc::ioctl;
use std::{convert::TryFrom,
          fmt,
          io::{self, BufWriter, Error, Write},
          path::{Path, PathBuf}};

pub type Fd = libc::c_int;

const PALETTE_SIZE: usize = 16;
const PALETTE_BYTES: usize = PALETTE_SIZE * 3; /* 16 * sizeof(int) */

/* XXX: can we get these into ``libc``? */
pub const KDGKBTYPE: libc::c_ulong = 0x4b33; /* kd.h */
const GIO_CMAP: libc::c_ulong = 0x00004B70; /* kd.h */
const PIO_CMAP: libc::c_ulong = 0x00004B71; /* kd.h */
pub const KB_101: libc::c_char = 0x0002; /* kd.h */

const RAW_COLEXPR_SIZE: usize = 6; /* e. g. 0xBADF00 */
pub type RawPalette<'a> = [&'a str; PALETTE_SIZE];

#[derive(Debug)]
pub enum Color
{
    Black(bool),
    Red(bool),
    Green(bool),
    Yellow(bool),
    Blue(bool),
    Magenta(bool),
    Cyan(bool),
    White(bool),
}

impl TryFrom<u8> for Color
{
    type Error = io::Error;

    fn try_from(val: u8) -> io::Result<Self>
    {
        match val {
            0x00 => Ok(Color::Black(false)),
            0x01 => Ok(Color::Red(false)),
            0x02 => Ok(Color::Green(false)),
            0x03 => Ok(Color::Yellow(false)),
            0x04 => Ok(Color::Blue(false)),
            0x05 => Ok(Color::Magenta(false)),
            0x06 => Ok(Color::Cyan(false)),
            0x07 => Ok(Color::White(false)),

            0x08 => Ok(Color::Black(true)),
            0x09 => Ok(Color::Red(true)),
            0x0a => Ok(Color::Green(true)),
            0x0b => Ok(Color::Yellow(true)),
            0x0c => Ok(Color::Blue(true)),
            0x0d => Ok(Color::Magenta(true)),
            0x0e => Ok(Color::Cyan(true)),
            0x0f => Ok(Color::White(true)),

            _ =>
                Err(io::Error::new(
                    io::ErrorKind::Other,
                    format!("invalid color value: {}", val),
                )),
        }
    }
} /* [impl TryFrom<u8> for Color] */

impl Color
{
    fn format_brightness(b: bool, s: &str) -> String
    {
        if b {
            "bright ".to_string() + s
        } else {
            s.to_string()
        }
    }
} /* [impl Color] */

impl fmt::Display for Color
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result
    {
        let c = match *self {
            Color::Black(b) => Color::format_brightness(b, "black"),
            Color::Red(b) => Color::format_brightness(b, "red"),
            Color::Green(b) => Color::format_brightness(b, "green"),
            Color::Yellow(b) => Color::format_brightness(b, "yellow"),
            Color::Blue(b) => Color::format_brightness(b, "blue"),
            Color::Magenta(b) => Color::format_brightness(b, "magenta"),
            Color::Cyan(b) => Color::format_brightness(b, "cyan"),
            Color::White(b) => Color::format_brightness(b, "white"),
        };

        write!(f, "{}", c)
    }
} /* [impl fmt::Display for Color] */

#[derive(Debug, Clone)]
pub struct Builtin
{
    names:   &'static [&'static str],
    palette: &'static RawPalette<'static>,
}

/** Vanilla Linux colors. */
const DEFAULT_COLORS: RawPalette = [
    "000000", "aa0000", "00aa00", "aa5500", "0000aa", "aa00aa", "00aaaa",
    "aaaaaa", "555555", "ff5555", "55ff55", "ffff55", "5555ff", "ff55ff",
    "55ffff", "ffffff",
];

/** The dark (default) version of the Solarized scheme. */
const SOLARIZED_COLORS_DARK: RawPalette = [
    "002b36", "dc322f", "859900", "b58900", "268bd2", "d33682", "2aa198",
    "eee8d5", "002b36", "cb4b16", "586e75", "657b83", "839496", "6c71c4",
    "93a1a1", "fdf6e3",
];

/** The light version of the Solarized theme. */
const SOLARIZED_COLORS_LIGHT: RawPalette = [
    "eee8d5", "dc322f", "859900", "b58900", "268bd2", "d33682", "2aa198",
    "073642", "fdf6e3", "cb4b16", "93a1a1", "839496", "657b83", "6c71c4",
    "586e75", "002b36",
];

/** Bright green monochrome terminal. */
const MONOCHROME_PHOSPHOR: RawPalette = [
    "000000", "68fc68", "68fc68", "68fc68", "68fc68", "68fc68", "68fc68",
    "68fc68", "68fc68", "68fc68", "68fc68", "68fc68", "68fc68", "68fc68",
    "68fc68", "68fc68",
];

const DUMMY_COLORS: RawPalette = [
    "000000", "ffffff", "000000", "ffffff", "000000", "ffffff", "000000",
    "ffffff", "000000", "ffffff", "000000", "ffffff", "000000", "ffffff",
    "000000", "ffffff",
];

pub const BUILTIN_SCHEMES: &[Builtin] = &[
    Builtin::solarized(),
    Builtin::solarized_light(),
    Builtin::default(),
    Builtin::phosphor(),
];

impl Builtin
{
    pub fn name(&self) -> &'static str { self.names.iter().next().unwrap() }

    pub fn palette(&self) -> &RawPalette { self.palette }

    const fn solarized() -> Self
    {
        Self {
            names:   &["solarized", "solarized_dark", "sd"],
            palette: &SOLARIZED_COLORS_DARK,
        }
    }

    const fn solarized_light() -> Self
    {
        Self {
            names:   &["solarized_light", "sl"],
            palette: &SOLARIZED_COLORS_LIGHT,
        }
    }

    const fn default() -> Self
    {
        Self {
            names:   &["default", "normal", "linux"],
            palette: &DEFAULT_COLORS,
        }
    }

    const fn phosphor() -> Self
    {
        Self { names: &["phosphor", "matrix"], palette: &MONOCHROME_PHOSPHOR }
    }
}

impl TryFrom<&str> for Builtin
{
    type Error = io::Error;

    fn try_from(name: &str) -> Result<Self, Self::Error>
    {
        for b in BUILTIN_SCHEMES {
            if b.names.contains(&name) {
                return Ok(b.clone());
            }
        }

        Err(io::Error::new(
            io::ErrorKind::Other,
            format!("no such builtin scheme: {}", name),
        ))
    }
}

impl<'a> fmt::Display for Builtin
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result
    {
        write!(f, "{}", self.name())
    }
}

#[derive(Debug)]
pub enum Scheme
{
    /** One of the predefined schemes. */
    Builtin(Builtin),
    /** Custom ``Palette``. */
    Palette(Palette),
    /** Load from file. */
    Custom(Option<PathBuf>),
}

impl<'a> fmt::Display for Scheme
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result
    {
        match self {
            Self::Builtin(b) => write!(f, "{}", b),
            Self::Custom(None) => write!(f, "<read stdin>"),
            Self::Custom(Some(fname)) => write!(f, "{}", fname.display()),
            Self::Palette(pal) => write!(f, "palette: {}", pal),
        }
    }
} /* [impl fmt::String for Scheme] */

impl Scheme
{
    pub fn from_stdin() -> Self { Self::Custom(None) }

    pub fn from_path<P: AsRef<Path>>(path: P) -> Self
    {
        Self::Custom(Some(path.as_ref().into()))
    }
} /* [impl Scheme] */

/** Try to select one of the predefined schemes; if that fails,
interpret the argument as a path. */
impl From<&str> for Scheme
{
    fn from(name: &str) -> Scheme
    {
        Builtin::try_from(name)
            .map(Self::Builtin)
            .unwrap_or_else(|_| Self::from_path(name))
    }
}

/** Try to match the palette against one of the predefined schemes. */
impl From<Palette> for Scheme
{
    fn from(pal: Palette) -> Scheme
    {
        if pal == Palette::from(&DEFAULT_COLORS) {
            return Self::Builtin(Builtin::default());
        }
        if pal == Palette::from(&SOLARIZED_COLORS_DARK) {
            return Self::Builtin(Builtin::solarized());
        }
        if pal == Palette::from(&SOLARIZED_COLORS_LIGHT) {
            return Self::Builtin(Builtin::solarized_light());
        }
        if pal == Palette::from(&MONOCHROME_PHOSPHOR) {
            return Self::Builtin(Builtin::phosphor());
        }

        Self::Palette(pal)
    }
}

fn nibble_of_char(chr: u8) -> u8
{
    match chr {
        b'0'..=b'9' => chr - b'0',
        b'a'..=b'f' => chr - b'a' + 10,
        b'A'..=b'F' => chr - b'A' + 10,
        _ => 0,
    }
}

macro_rules! byte_of_hex {
    ($ar:ident, $off:expr) => {
        (nibble_of_char($ar[$off])) << 4 | nibble_of_char($ar[$off + 1]) as u8
    };
}

fn rgb_of_hex_triplet(def: &str) -> (u8, u8, u8)
{
    let bytes = def.as_bytes();
    let r: u8 = byte_of_hex!(bytes, 0);
    let g: u8 = byte_of_hex!(bytes, 2);
    let b: u8 = byte_of_hex!(bytes, 4);
    (r, g, b)
}

#[derive(Eq, PartialEq, Clone)]
pub struct Palette([u8; PALETTE_BYTES]);

impl Palette
{
    /** Construct an all-zero ``Palette``. */
    pub fn new() -> Self { Self([0u8; PALETTE_BYTES]) }

    pub fn dummy() -> Self { Self::from(&DUMMY_COLORS) }

    pub fn from_buffered_reader(reader: &mut dyn std::io::BufRead) -> Self
    {
        let mut pal_idx: usize = 0;
        let mut pal: [u8; PALETTE_BYTES] = [0; PALETTE_BYTES];
        let mut line: String = String::new();

        while reader.read_line(&mut line).is_ok() {
            let len = line.len();
            if len == 0 {
                break;
            } else if len >= 8 {
                if let Some(off) = line.find('#') {
                    if off != 0 {
                        /* Palette index specified, number prepended */
                        let parse_res: Result<usize, _> =
                            std::str::FromStr::from_str(&line[0..off]);
                        if let Ok(new_idx) = parse_res {
                            if new_idx < PALETTE_SIZE {
                                pal_idx = new_idx * 3;
                            }
                        }
                    }
                    let off = off + 1;
                    if off > len - 6 {
                        /* no room left for color definition after '#' char */
                        panic!("invalid color definition: {}", line);
                    }
                    let col = &line[off..(off + RAW_COLEXPR_SIZE)];

                    let (r, g, b) = rgb_of_hex_triplet(col);
                    pal[pal_idx] = r;
                    pal[pal_idx + 1] = g;
                    pal[pal_idx + 2] = b;
                    pal_idx = (pal_idx + 3) % PALETTE_BYTES;
                }
            }
            line.truncate(0);
        }

        Self(pal)
    }

    #[allow(rustdoc::invalid_rust_codeblocks)]
    /** Print palette in a text format that can be re-read back in.
    Basically we print one hex rgb code per line prefixed with color
    indices and the canonical names on the right:

        00  #002B36  black
        01  #DC322F  red
        02  #859900  green
        03  #B58900  yellow
        04  #268BD2  blue
        …
    */
    pub fn dump(&self, out: &mut BufWriter<io::Stdout>) -> io::Result<()>
    {
        let mut buf: [u8; 3] = [0u8, 0u8, 0u8];
        for (i, col) in self.0.iter().enumerate() {
            let idx: usize = i % 3;
            buf[idx] = *col;
            if idx == 2 {
                let col = Color::try_from((i / 3) as u8)?;
                out.write_all(
                    format!(
                        "{:02}  #{:02.X}{:02.X}{:02.X}  {}\n",
                        i / 3,
                        buf[0],
                        buf[1],
                        buf[2],
                        col,
                    )
                    .as_bytes(),
                )?;
            }
        }

        Ok(())
    }

    pub fn from_file(fname: &Path) -> Self
    {
        /* Check if file exists
         */
        let file = match std::fs::File::open(&fname) {
            Err(e) => {
                panic!("failed to open {} as file ({})", fname.display(), e)
            },
            Ok(f) => f,
        };
        let mut reader = std::io::BufReader::new(file);

        /* Parse scheme file
         */
        Self::from_buffered_reader(&mut reader)
    }

    /* [Palette::from_file] */

    pub fn from_stdin() -> Self
    {
        let mut reader = std::io::BufReader::new(std::io::stdin());

        /* Parse scheme file
         */
        Self::from_buffered_reader(&mut reader)
    } /* [Palette::from_stdin] */
} /* [impl Palette] */

impl fmt::Display for Palette
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result
    {
        let mut i = 0;
        while i < PALETTE_BYTES {
            let _ = write!(f, "{}", if i == 0 { "(" } else { "\n " });
            let r = self.0[i];
            let g = self.0[i + 1];
            let b = self.0[i + 2];
            let _ = write!(
                f,
                "((r 0x{:02.X}) (g 0x{:02.X}) (b 0x{:02.x}))",
                r, g, b
            );
            i += 3;
        }
        writeln!(f, ")")
    }
} /* [impl fmt::Display for Palette] */

impl fmt::Debug for Palette
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result
    {
        let mut i: u8 = 0_u8;
        while (i as usize) < PALETTE_BYTES {
            let r = self.0[i as usize];
            let g = self.0[i as usize + 1];
            let b = self.0[i as usize + 2];
            let col = Color::try_from((i / 3) as u8)
                .map(|c| format!("{}", c))
                .unwrap_or_else(|_| "??".into());
            let _ = writeln!(f, "{} => 0x{:02.X}{:02.X}{:02.X}", col, r, g, b);
            i += 3_u8;
        }
        std::result::Result::Ok(())
    }
} /* [impl fmt::Debug for Palette] */

/** Obtain a ``Palette`` from a ``Scheme``. */
impl From<&Scheme> for Palette
{
    fn from(scm: &Scheme) -> Self
    {
        match scm {
            Scheme::Builtin(Builtin { palette, .. }) => Self::from(*palette),
            Scheme::Custom(None) => Self::from_stdin(),
            Scheme::Custom(Some(ref fname)) => Self::from_file(fname),
            Scheme::Palette(pal) => pal.clone(),
        }
    }
}

/** Obtain a ``Palette`` from a ``RawPalette``. */
impl From<&RawPalette<'_>> for Palette
{
    fn from(colors: &RawPalette<'_>) -> Self
    {
        let mut idx: usize = 0;
        let mut pal: [u8; PALETTE_BYTES] = [0; PALETTE_BYTES];

        for def in colors.iter() {
            let (r, g, b) = rgb_of_hex_triplet(*def);
            pal[idx] = r;
            pal[idx + 1] = g;
            pal[idx + 2] = b;
            //println!(">> {} -> {:X} {:X} {:X}", def, r, g, b);
            idx += 3;
        }

        Self(pal)
    }
}

pub fn ioctl_pio_cmap(fd: Fd, pal: &Palette) -> io::Result<()>
{
    if unsafe {
        ioctl(
            fd,
            PIO_CMAP,
            std::mem::transmute::<&Palette, *const libc::c_void>(&pal),
        )
    } < 0
    {
        Err(Error::last_os_error())
    } else {
        Ok(())
    }
}

pub fn ioctl_gio_cmap(fd: Fd) -> io::Result<Palette>
{
    let mut pal = Palette::new();

    if unsafe {
        ioctl(
            fd,
            GIO_CMAP,
            std::mem::transmute::<&mut Palette, *mut libc::c_void>(&mut pal),
        )
    } < 0
    {
        Err(Error::last_os_error())
    } else {
        Ok(pal)
    }
}