use std::{fmt,
          path::{Path, PathBuf},
          sync::atomic::{AtomicBool, Ordering}};

type Fd = libc::c_int;

static VERBOSITY: AtomicBool = AtomicBool::new(false);

macro_rules! vrb {
    ( $( $e:expr ),* ) => {(
            if VERBOSITY.load(Ordering::SeqCst) { println!( $( $e ),* ) }
    )}
}

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

const RAW_COLEXPR_SIZE: usize = 6; // e. g. 0xBADF00

type RawPalette<'a> = [&'a str; PALETTE_SIZE];

const KDGKBTYPE: libc::c_int = 0x4b33; /* kd.h */
const PIO_CMAP: libc::c_int = 0x00004B71; /* kd.h */
const KB_101: libc::c_char = 0x0002; /* kd.h */
const O_NOCTTY: libc::c_int = 0o0400; /* fcntl.h */

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

impl Color
{
    fn of_value(val: u8) -> Color
    {
        match val {
            0x00_u8 => Color::Black(false),
            0x01_u8 => Color::Red(false),
            0x02_u8 => Color::Green(false),
            0x03_u8 => Color::Yellow(false),
            0x04_u8 => Color::Blue(false),
            0x05_u8 => Color::Magenta(false),
            0x06_u8 => Color::Cyan(false),
            0x07_u8 => Color::White(false),

            0x08_u8 => Color::Black(true),
            0x09_u8 => Color::Red(true),
            0x0a_u8 => Color::Green(true),
            0x0b_u8 => Color::Yellow(true),
            0x0c_u8 => Color::Blue(true),
            0x0d_u8 => Color::Magenta(true),
            0x0e_u8 => Color::Cyan(true),
            0x0f_u8 => Color::White(true),

            _ => panic!("invalid color value: {}", val),
        }
    }

    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)]
enum Scheme
{
    Default,
    SolarizedDark,
    SolarizedLight,
    Custom(Option<PathBuf>),
}

impl<'a> fmt::Display for Scheme
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result
    {
        match self {
            Scheme::Default => write!(f, "default"),
            Scheme::SolarizedDark => write!(f, "solarized_dark"),
            Scheme::SolarizedLight => write!(f, "solarized_light"),
            Scheme::Custom(None) => write!(f, "<read stdin>"),
            Scheme::Custom(Some(fname)) => write!(f, "{}", fname.display()),
        }
    }
} /* [impl fmt::String for Scheme] */

/* struct Job -- Runtime parameters.
 */
#[derive(Debug)]
struct Job
{
    scheme: Scheme, /* The color scheme to switch to. */
}

impl<'a> Job
{
    pub fn from_argv() -> Job
    {
        use clap::{App, Arg};

        let matches = App::new(clap::crate_name!())
            .version(clap::crate_version!())
            .author(clap::crate_authors!())
            .about(clap::crate_description!())
            .arg(
                Arg::with_name("scheme")
                    .short("s")
                    .long("scheme")
                    .value_name("NAME")
                    .help("predefined color scheme")
                    .takes_value(true),
            )
            .arg(
                Arg::with_name("dump")
                    .short("d")
                    .long("dump")
                    .value_name("NAME")
                    .help("dump predefined scheme")
                    .takes_value(true),
            )
            .arg(
                Arg::with_name("file")
                    .short("f")
                    .long("file")
                    .value_name("PATH")
                    .help("apply scheme from file")
                    .takes_value(true),
            )
            .arg(
                Arg::with_name("verbose")
                    .short("v")
                    .long("verbose")
                    .help("enable extra diagnostics")
                    .takes_value(false),
            )
            .arg(
                Arg::with_name("list")
                    .short("l")
                    .long("list")
                    .help("list available color schemes")
                    .takes_value(false),
            )
            .arg(
                Arg::with_name("help")
                    .short("h")
                    .long("help")
                    .help("print this message")
                    .takes_value(false),
            )
            .get_matches();

        if matches.is_present("v") {
            VERBOSITY.store(true, Ordering::SeqCst);
        }

        if matches.is_present("l") {
            Job::schemes();
            std::process::exit(0);
        };

        if let Some(name) = matches.value_of("dump") {
            let scm = Job::pick_scheme(name);
            Job::dump(scm);
            std::process::exit(0);
        }

        let scheme = match matches.value_of("file") {
            Some("-") => Job::scheme_from_stdin(),
            Some(fname) => Scheme::Custom(Some(PathBuf::from(fname))),
            None =>
                match matches.value_of("scheme") {
                    Some("-") | None => Job::scheme_from_stdin(),
                    Some(name) => Job::pick_scheme(name),
                },
        };

        Job { scheme }
    }

    fn pick_scheme(name: &str) -> Scheme
    {
        match name {
            "solarized" | "solarized_dark" | "sd" => Scheme::SolarizedDark,
            "solarized_light" | "sl" => Scheme::SolarizedLight,
            "default" | "normal" => Scheme::Default,
            _any => Scheme::Custom(Some(PathBuf::from(name))),
        }
    }

    fn scheme_from_stdin() -> Scheme { Scheme::Custom(None) }

    fn schemes()
    {
        println!("Available color schemes:");
        println!("      · solarized_dark");
        println!("      · solarized_light");
        println!("      · default");
    }

    fn dump(scm: Scheme)
    {
        vrb!("Dumping color scheme {}", scm);
        match scm {
            Scheme::Default => Job::dump_scheme(&DEFAULT_COLORS),
            Scheme::SolarizedDark => Job::dump_scheme(&SOLARIZED_COLORS_DARK),
            Scheme::SolarizedLight => Job::dump_scheme(&SOLARIZED_COLORS_LIGHT),
            Scheme::Custom(None) => Job::dump_palette(Palette::from_stdin()),
            Scheme::Custom(Some(fname)) =>
                Job::dump_palette(Palette::from_file(&fname)),
        }
    }

    fn dump_scheme(colors: &[&str; PALETTE_SIZE])
    {
        let pal: Palette = Palette::new(colors);
        pal.dump()
    }

    fn dump_palette(pal: Palette) { pal.dump() }
} /* [impl Job] */

/* Rust appears to come with two wrappers for ``ioctl(2)``, but neither can be utilized for our
 * purposes. The one in ``sys`` is part of a private (seriously‽) whereas the one in the
 * ``libc`` module is defined as taking variable arguments and therefore cannot be called from
 * Rust. Wrapping C is still a bit awkward, as it seems.
 */
extern "C" {
    pub fn ioctl(
        d: libc::c_int,
        request: libc::c_int,
        data: *mut libc::c_void,
    ) -> libc::c_int;
}

static CONSOLE_PATHS: [&str; 6] = [
    "/proc/self/fd/0",
    "/dev/tty",
    "/dev/tty0",
    "/dev/vc/0",
    "/dev/systty",
    "/dev/console",
];

static DEFAULT_COLORS: RawPalette = [
    "000000", "aa0000", "00aa00", "aa5500", "0000aa", "aa00aa", "00aaaa",
    "aaaaaa", "555555", "ff5555", "55ff55", "ffff55", "5555ff", "ff55ff",
    "55ffff", "ffffff",
];

static SOLARIZED_COLORS_DARK: RawPalette = [
    "002b36", "dc322f", "859900", "b58900", "268bd2", "d33682", "2aa198",
    "eee8d5", "002b36", "cb4b16", "586e75", "657b83", "839496", "6c71c4",
    "93a1a1", "fdf6e3",
];

static SOLARIZED_COLORS_LIGHT: RawPalette = [
    "eee8d5", "dc322f", "859900", "b58900", "268bd2", "d33682", "2aa198",
    "073642", "fdf6e3", "cb4b16", "93a1a1", "839496", "657b83", "6c71c4",
    "586e75", "002b36",
];

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

pub struct Palette
{
    colors: [u8; PALETTE_BYTES],
}

impl Palette
{
    fn dump(&self)
    {
        let mut buf: [u8; 3] = [0u8, 0u8, 0u8];
        for (i, col) in self.colors.iter().enumerate() {
            let idx: usize = i % 3;
            buf[idx] = *col;
            if idx == 2 {
                println!(
                    "{:>15} => 0x{:02.X}{:02.X}{:02.X}",
                    Color::of_value((i / 3) as u8).to_string(),
                    buf[0],
                    buf[1],
                    buf[2]
                );
            }
        }
    }
} /* [impl Palette] */

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)
}

impl Palette
{
    pub fn new(colors: &[&str; PALETTE_SIZE]) -> Palette
    {
        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;
        }

        Palette { colors: pal }
    }

    /* [Palette::new] */

    pub fn dummy() -> Palette { Palette::new(&DUMMY_COLORS) }

    /* [Palette::dummy] */

    pub fn from_buffered_reader(reader: &mut dyn std::io::BufRead) -> Palette
    {
        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);
        }

        Palette { colors: pal }
    }

    /* [Palette::from_buffered_reader] */

    pub fn from_file(fname: &Path) -> Palette
    {
        /* 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
         */
        Palette::from_buffered_reader(&mut reader)
    }

    /* [Palette::from_file] */

    pub fn from_stdin() -> Palette
    {
        vrb!("Go ahead, type your color scheme …");
        vrb!("vtcol>");
        let mut reader = std::io::BufReader::new(std::io::stdin());

        /* Parse scheme file
         */
        Palette::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.colors[i];
            let g = self.colors[i + 1];
            let b = self.colors[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.colors[i as usize];
            let g = self.colors[i as usize + 1];
            let b = self.colors[i as usize + 2];
            let _ = writeln!(
                f,
                "{} => 0x{:02.X}{:02.X}{:02.X}",
                Color::of_value(i),
                r,
                g,
                b
            );
            i += 3_u8;
        }
        std::result::Result::Ok(())
    }
} /* [impl fmt::Debug for Palette] */

fn fd_of_path(path: &std::path::Path) -> Option<Fd>
{
    let p = std::ffi::CString::new(path.to_str().unwrap()).unwrap();
    match unsafe { libc::open(p.as_ptr(), libc::O_RDWR | O_NOCTTY, 0) } {
        -1 => None,
        fd => {
            vrb!("  *> got fd");
            if unsafe { libc::isatty(fd) } == 0 {
                vrb!("  *> not a tty");
                return None;
            }

            let mut tty_type: libc::c_char = 0;

            let res = unsafe {
                ioctl(
                    fd,
                    KDGKBTYPE as libc::c_int,
                    std::mem::transmute(&mut tty_type),
                )
            };
            if res < 0 {
                vrb!("  *> ioctl failed");
                return None;
            }

            if tty_type != KB_101 {
                return None;
            }

            Some(fd)
        },
    }
}

fn get_console_fd(path: Option<&str>) -> Option<Fd>
{
    match path {
        Some(path) => {
            let path = std::path::Path::new(path);
            match fd_of_path(path) {
                Some(fd) => Some(fd),
                None => panic!("cannot open {:?} as a tty", path),
            }
        },
        None => {
            for path in CONSOLE_PATHS.iter() {
                vrb!("trying path: {:?}", path);
                let path = std::path::Path::new(path);
                if let Some(fd) = fd_of_path(path) {
                    vrb!(" * Success!");
                    return Some(fd);
                }
            }
            vrb!("could not retrieve fd for any of the search paths");
            None
        },
    }
}

fn write_to_term(fd: Fd, buf: &str)
{
    let len = buf.len() as libc::size_t;
    let raw = std::ffi::CString::new(buf.as_bytes()).unwrap();
    unsafe { libc::write(fd, raw.as_ptr() as *const libc::c_void, len) };
}

fn clear_term(fd: Fd)
{
    let clear: &str = "\x1b[2J";
    let cursor: &str = "\x1b[1;1H";
    write_to_term(fd, clear);
    write_to_term(fd, cursor);
}

fn main()
{
    let job = Job::from_argv();
    vrb!("job parms: {:?}", job);
    let mut pal: Palette = match job.scheme {
        Scheme::Default => Palette::new(&DEFAULT_COLORS),
        Scheme::SolarizedDark => Palette::new(&SOLARIZED_COLORS_DARK),
        Scheme::SolarizedLight => Palette::new(&SOLARIZED_COLORS_LIGHT),
        Scheme::Custom(None) => Palette::from_stdin(),
        Scheme::Custom(Some(ref fname)) => Palette::from_file(fname),
    };
    vrb!("Using palette:");
    vrb!("{}", pal);
    let fd = get_console_fd(None).unwrap();
    vrb!("fd: {}", fd);

    if unsafe { ioctl(fd, PIO_CMAP, std::mem::transmute(&mut pal)) } < 0 {
        panic!("PIO_CMAP, ioctl failed to insert new palette")
    }
    clear_term(fd);
    vrb!("terminated from job {:?}", job);
}