use std::cmp::{min, max};
use std::io;
use std::io::{Seek, SeekFrom};
use std::fs;
use std::fmt::Write;
use std::io::Read;
use std::env;
//use std::path::Path;

extern crate termios;
use termios::{Termios, TCSANOW, ECHO, ICANON, tcsetattr};

extern crate termion;
use termion::{color, input};
use termion::input::TermRead;
use termion::event::{Event, Key};

fn main() {
    println!("hello");
    match termion::terminal_size() {
        Ok((w, h)) => {
            if let Some(arg1) = env::args().nth(1) {
                println!("You would like to work with {}.", arg1);
                launch_interface(w, h, arg1.clone());
            } else {
                usage();
            }
        }
        Err(e) => {
            println!("{}", e);
        }
    }
}

fn usage() {
    println!("usage: this_thing filename");
}

struct Program {
    filename: String,
    filelen: u64,
    width: u16,
    row_size: u16,
    height: u16,
    seek: u64,
    cursor: u64,
    old_term: Termios,
    new_term: Termios,
    buf: Vec<u8>
}

impl Program {
    fn inc_cursor(&mut self, amount: u64) {
        if self.filelen - self.cursor < amount {
            self.cursor = self.filelen - 1;
        } else {
            self.cursor += amount;
        }
        self.recalculate_seek();
    }
    fn dec_cursor(&mut self, amount: u64) {
        if self.cursor < amount {
            self.cursor = 0;
        } else {
            self.cursor -= amount;
        }
        self.recalculate_seek();
    }
    fn recalculate_seek(&mut self) {
        let old_seek = self.seek;
        let bufsize = self.height as u64 * self.width as u64;
        let render_lim = (self.row_size as u64) * (self.height as u64 - 1); // this shouldn't be decided here...
        if self.cursor + render_lim > self.seek + bufsize { // know a priori that buf size is height * width. TODO: fix.
            println!("aaaa");
            // we've sought past the end, so reset seek to what would have been the start of this
            // display and it'll all work out from here.
            self.seek = self.cursor - (self.cursor % self.row_size as u64);
        } else if self.cursor < self.seek {
            println!("bbbb");
            // we've sought before the start, so reset seek to just before. ideally, populate a
            // buffer for like 1k before, but lazy.
            self.seek = self.cursor - (self.cursor % self.row_size as u64);
        }

        // repopulate buf..
        if self.seek != old_seek {
            self.buf = populate_buf(&self.filename, self.seek, bufsize);
        }
    }
}

fn launch_interface(w: u16, h: u16, filename: String) {
    match fs::metadata(&filename) {
        Ok(fs_meta) => {
            println!("{} is {} bytes, and is it readable? {}", filename, fs_meta.len(), true);
            let termios = Termios::from_fd(0).unwrap();

            let mut new_termios = termios.clone();

            // fix terminal to not echo, thanks
            new_termios.c_lflag &= !(ICANON | ECHO);

            let initial_buf = populate_buf(&filename, 0, w as u64 * h as u64);

            let mut state = Program {
                filename: filename,
                filelen: fs_meta.len(),
                width: w,
    // let col_width = 4;
    // w = 10 + 1 + 1 + 4 * 3 * x + x + 1 + 4 * x
    // w = 13 + 17 * x
    // w - 13 / 17 = x
                row_size: ((w - 13) / 17) * 4,
                height: h,
                old_term: termios,
                new_term: new_termios,
                cursor: 0,
                seek: 0,
                buf: initial_buf
            };

            tcsetattr(0, TCSANOW, &state.new_term).unwrap();

            interface_loop(&mut state);

            tcsetattr(0, TCSANOW, &state.old_term).unwrap();
        },
        Err(e) => 
            println!("{} does not exist. ({})", filename, e),
    }
}

fn interface_loop(state: &mut Program) {
//    let buffer = populate_buf(&state.filename, state.cursor, state.width as u64 * state.height as u64); // sw*h over-estimates by about a factor of.. 4?
    render_interface(state);

    let stdin = io::stdin();

//    for input in KeyboardInput::from_stdin(&stdin.lock().bytes()) {
    for input in stdin.events() {
        match input.unwrap() {
            Event::Key(Key::Up) => {
                let amount = state.row_size; // why can't this be inlined?
                state.dec_cursor(amount as u64);
            }
            Event::Key(Key::Down) => {
                let amount = state.row_size;
                state.inc_cursor(amount as u64);
            }
            Event::Key(Key::Left) => {
                state.dec_cursor(1);
            }
            Event::Key(Key::Right) => {
                state.inc_cursor(1);
            }
            Event::Key(Key::PageDown) => {
                let amount = (state.row_size as u64) * (state.height as u64 - 1);
                state.inc_cursor(amount);
            }
            Event::Key(Key::PageUp) => {
                let amount = (state.row_size as u64) * (state.height as u64 - 1);
                state.dec_cursor(amount);
            }
            u => {
                println!("Got {:?}", u);
                break;
            }
        }
        render_interface(state);
    }
}

/*
struct KeyboardInput {
    
}

impl KeyboardInput {
    fn from_stdin(x: &Iterator<Item = io::Result<u8>>) -> KeyboardInput {
        let x = KeyboardInput { };
        x
    }
}

impl Iterator for KeyboardInput {
    type Item = KeyInfo;
    fn next(&mut self) -> Option<Self::Item> {
        Some(0)
    }
}
*/

fn ascii_or_dot(c: u8) -> u8 {
    let u = c as char;
    if
        u >= 'a' && u <= 'z' ||
        u >= '0' && u <= '9' ||
        u >= 'A' && u <= 'Z' ||
        u == '~' || u == '!' ||
        u == '@' || u == '#' ||
        u == '$' || u == '%' ||
        u == '^' || u == '&' ||
        u == '*' || u == '(' ||
        u == ')' || u == '_' ||
        u == '+' || u == '{' ||
        u == '}' || u == '|' ||
        u == ':' || u == '"' ||
        u == '>' || u == '?' ||
        u == '-' || u == '=' ||
        u == '[' || u == ']' ||
        u == '\\' || u == ';' ||
        u == '\'' || u == '.' ||
        u == '/' || u == '<' ||
        u == ',' || u == '`' {
        c
    } else {
        '.' as u8
    }
}

fn render_interface(state: &Program) {
    println!("Dimensions: {}x{}    Seek: {}, Cursor: {}  - file: {}, {} bytes", state.width, state.height, state.seek, state.cursor, state.filename, state.filelen);
    //let addr_width = 8;
//    let ascii = bytes_width * cols;

    let buffer = &state.buf;

    let start = (state.cursor - state.seek) as usize;
    let mut idx: usize = start;
    let col_width = 4;
    for i in 1..(state.height-1) {
        let mut hex_line = String::new();
        let mut ascii_line = String::new();
        for _ in 0..(state.row_size / 4) {
            for _ in 0..col_width {
                if idx < buffer.len() {
                    let chr = buffer[idx];
                    if idx as u64 + state.seek == state.cursor {
                        write!(&mut hex_line, "\x1b[33m").unwrap();
                        write!(&mut ascii_line, "\x1b[33m").unwrap();
                    }
                    write!(&mut hex_line, "{:02x} ", chr).unwrap();
                    write!(&mut ascii_line, "{}", ascii_or_dot(chr) as char).unwrap();
                    if idx as u64 + state.seek == state.cursor {
                        write!(&mut hex_line, "\x1b[0m").unwrap();
                        write!(&mut ascii_line, "\x1b[0m").unwrap();
                    }
                } else {
                    write!(&mut hex_line, "   ").unwrap();
                    write!(&mut ascii_line, " ").unwrap();
                }
                idx += 1;
            }
            write!(&mut hex_line, " ").unwrap();
        }

        let lineaddr = start as u64 + ((i as u64) - 1) * (state.row_size as u64);
        let addr = if (lineaddr as usize) < buffer.len() {
            format!("0x{:08x}:", lineaddr)
        } else {
            "           ".to_string()
        };
        println!("{} {} {}", addr, hex_line, ascii_line);
    }
}

fn populate_buf(arg: &String, seek: u64, count: u64) -> Vec<u8> {
    match fs::File::open(&arg) {
        Ok(mut fd) => {
            /*..*/
            fd.seek(SeekFrom::Start(seek)).unwrap();
            fd
                .bytes()
                .take(count as usize)
                .map(|r| r.unwrap()) // lazy
                .collect()
        },
        Err(_) =>
        {
            println!("Failed to open {}", arg);
            panic!();
        }
    }
}