//use std::cmp::{min, max};
//use std::io::Write as IoWrite;
use std::collections::HashMap;
use std::fmt::Write as FmtWrite;
use std::io::{Seek, SeekFrom};
use std::fs;
use std::io::Read;
use std::env;
use std::iter::FromIterator;
//use std::path::Path;

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

extern crate termion;
use termion::color;
//use termion::{color, input};
use termion::input::TermRead;
use termion::event::{Event, Key};
use termion::screen::AlternateScreen;
use termion::raw::IntoRawMode;
use termion::clear;
use termion::cursor;

fn main() {
    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 CachingFileView {
    file: std::fs::File,
    filelen: u64,
    cache_seek: u64,
    cache_size: usize,
    cache_len: usize,
    cache: Vec<u8>
}

impl FileView for CachingFileView {
    fn get_bytes(&mut self, offset: u64, len: u64) -> Vec<u8> {
        if len > self.cache_size as u64 {
            panic!("Caching view does not support get_bytes() larger than cache size");
        }
        // check if we have to update the cache
        if offset <= self.cache_seek as u64 || offset + len > self.cache_seek + self.cache_len as u64 {
            // we do...
            self.cache.clear();
            self.cache.resize(self.cache_size as usize, 0);
            // Seek such that the requested bytes are the middle of the cache, if possible
            // theory is this is a decent compromise for not knowing which direction
            // to predict motion towards
            self.cache_seek = std::cmp::max(offset as i64 - (self.cache_size as i64 / 2), 0) as u64;
            self.file.seek(SeekFrom::Start(self.cache_seek)).unwrap();
            self.file.read(&mut self.cache).unwrap();
            self.cache_len = self.cache.len();
        }

        // ok now that's ``cached``...
        let cached_start = (offset - self.cache_seek) as usize;
        let cached_end = cached_start + len as usize;
        Vec::from_iter(self.cache[cached_start..cached_end].iter().cloned())
    }
    fn size(&self) -> u64 { self.filelen }
}

impl CachingFileView {
    fn new(filepath: String) -> Result<CachingFileView, std::io::Error> {
        let f = try!(fs::File::open(&filepath));
        let metadata = try!(f.metadata());
        // modified() is probably how we should check concurrent modifications
        if metadata.permissions().readonly() {
            return Err(std::io::Error::new(std::io::ErrorKind::PermissionDenied, "File is read-only"));
        }

        Ok(CachingFileView {
            file: f,
            filelen: metadata.len(),
            cache_seek: 0,
            cache_size: 64 * 1024,
            cache_len: 0,
            cache: Vec::with_capacity(64 * 1024)
        })
    }
}

/*
struct NoCacheFileView {
    file: std::fs::File,
    filelen: u64
}

impl NoCacheFileView {
    fn new(filepath: String) -> Result<NoCacheFileView, std::io::Error> {
        let f = try!(fs::File::open(&filepath));
        let metadata = try!(f.metadata());
        // modified() is probably how we should check concurrent modifications
        if metadata.permissions().readonly() {
            return Err(std::io::Error::new(std::io::ErrorKind::PermissionDenied, "File is read-only"));
        }

        Ok(NoCacheFileView {
            file: f,
            filelen: metadata.len()
        })
    }
}

impl FileView for NoCacheFileView {
    fn get_bytes(&mut self, offset: u64, len: u64) -> Vec<u8> {
        let mut vec = Vec::with_capacity(len as usize);
        vec.resize(len as usize, 0);
        self.file.seek(SeekFrom::Start(offset)).unwrap();
        self.file.read(&mut vec).unwrap();
        vec
    }
    fn size(&self) -> u64 { self.filelen }
}
*/

trait FileView {
    fn get_bytes(&mut self, offset: u64, len: u64) -> Vec<u8>;
    fn size(&self) -> u64;
}

const MODAL_WIDTH: usize = 24;

// super naive, no idea how to track inserts/deletions yet
struct Edits {
    edit_list: HashMap<u64, u8>
}

impl Edits {
    fn new() -> Edits {
        Edits {
            edit_list: std::collections::HashMap::new()
        }
    }
    // TODO: this should accept the various kinds of edits and
    // positions down to bit-level, then figure it out.
    //
    // consider:
    // Bit(location, value)
    // Base64(location, value)
    // Byte(location, value)
    fn remove(&mut self, cursor: u64) {
        self.edit_list.remove(&cursor);
    }
    fn record(&mut self, cursor: u64, value: u8) {
        self.edit_list.insert(cursor, value);
    }
}

trait EditMode {
    fn render_bytes(&self, cursor: u64, width: u16, start: u64, bytes: std::slice::Iter<u8>) -> String;
    // translates from the width of the display (terminal)
    // to the number of bytes this edit mode can display
    fn element_width(&self, display_width: u16) -> u64;
    fn dec_sub_elem(&mut self, amount: u64);
    fn inc_sub_elem(&mut self, amount: u64);
}

struct BinaryMode {
    sub_elem_idx: u8
}

impl EditMode for BinaryMode {
    fn render_bytes(&self, cursor: u64, width: u16, start: u64, bytes: std::slice::Iter<u8>) -> String {
        let mut text = "".to_owned();
//        let mut ascii_text = "".to_owned();
        let col_size = 1;
        let mut i: usize = 0;
        for b in bytes {
            if cursor == start + i as u64 {
                text.push_str(&format!("{}", color::Fg(color::Yellow)));
//                ascii_text.push_str(&format!("{}", color::Fg(color::Yellow)));
                text.push_str(&format!("{:08b}", b));
//                ascii_text.push_str(&format!("{}", ascii_or_dot(b.to_owned()) as char));
                text.push_str(&format!("{}", color::Fg(color::Reset)));
//                ascii_text.push_str(&format!("{}", color::Fg(color::Reset)));
            } else {
                text.push_str(&format!("{:08b}", b));
//                ascii_text.push_str(&format!("{}", ascii_or_dot(b.to_owned()) as char));
            }
            if i % col_size == (col_size - 1) {
                text.push_str(" ");
            } else {
                text.push_str(" ");
            }
            i = i + 1;
        }
        format!("            {}", text).to_owned()
    }
    fn element_width(&self, display_width: u16) -> u64 {
        // left pad by 12, 9 chars wide per byte
        (display_width as u64 - 12 - 12) / 9
    }
    fn dec_sub_elem(&mut self, amount: u64) {
        self.sub_elem_idx = self.sub_elem_idx - amount as u8;
    }
    fn inc_sub_elem(&mut self, amount: u64) {
        self.sub_elem_idx = self.sub_elem_idx + amount as u8;
    }
}

struct HexMode {
    sub_elem_idx: u8
}

impl EditMode for HexMode {
    fn render_bytes(&self, cursor: u64, width: u16, start: u64, bytes: std::slice::Iter<u8>) -> String {
        let mut text = "".to_owned();
        let mut ascii_text = "".to_owned();
        let col_size = 4;
        let mut i: usize = 0;
        let selected = true;
        for b in bytes {
            if cursor == start + i as u64 {
                text.push_str(&format!("{}", color::Fg(color::Yellow)));
                ascii_text.push_str(&format!("{}", color::Fg(color::Yellow)));
                if selected {
                    text.push_str(&format!("{}", termion::style::Bold));
                }
                text.push_str(&format!("{:02x}", b));
                ascii_text.push_str(&format!("{}", ascii_or_dot(b.to_owned()) as char));
                if selected {
                    text.push_str(&format!("{}", termion::style::Reset));
                }
                text.push_str(&format!("{}", color::Fg(color::Reset)));
                ascii_text.push_str(&format!("{}", color::Fg(color::Reset)));
            } else {
                text.push_str(&format!("{:02x}", b));
                ascii_text.push_str(&format!("{}", ascii_or_dot(b.to_owned()) as char));
            }
            if i % col_size == (col_size - 1) {
                text.push_str("  ");
            } else {
                text.push_str(" ");
            }
            i = i + 1;
        }
        /*
         *                   12 == "<address>: "
         *                        i / col_size for the extra space between columns
         *                                i * 3 for 3 characters per byte
         *                                              + 1 for padding..
         */
        let hex_line_width = 12 + i / col_size + i * 3 + 1;
        let padding = format!("{: >line_width$}", "", line_width = width as usize - hex_line_width - i);
        format!("0x{:08x}: {}{}{}", start, text, padding, ascii_text).to_owned()
    }
    fn element_width(&self, display_width: u16) -> u64 {
        (display_width as u64 - 13) / 17 * 4
    }
    fn dec_sub_elem(&mut self, amount: u64) {
        self.sub_elem_idx = self.sub_elem_idx - amount as u8;
    }
    fn inc_sub_elem(&mut self, amount: u64) {
        self.sub_elem_idx = self.sub_elem_idx + amount as u8;
    }
}

struct Program<'a, 'b> {
    filename: String,
    width: u16,
    height: u16,
    seek: u64,
    cursor: u64,
    old_term: Termios,
    new_term: Termios,
    screen: &'a mut std::io::Write,
    view: &'b mut FileView,
    input_buf: Vec<char>,
    state: Mode,
    edits: Edits,
    status: String,
    edit_views: Vec<&'b mut EditMode>,
    current_edit_idx: usize
    //screen: AlternateScreen<termion::raw::RawTerminal<std::io::Stdout>>
}

impl <'a, 'b> Program<'a, 'b> {
    fn lines_to_draw(&self) -> u64 {
        self.view_byte_height() / self.edit_views.len() as u64
    }
    fn seek_to(&mut self, dest: u64) {
        self.cursor = dest;
        self.recalculate_seek();
    }
    fn inc_cursor(&mut self, amount: u64) {
        if self.view.size() - self.cursor < amount {
            self.cursor = self.view.size() - 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 view_interface_height(&self) -> u64 {
        2
    }

    fn view_byte_height(&self) -> u64 {
        self.height as u64 - self.view_interface_height()
    }

    fn bytes_per_line(&self) -> u64 {
        let mut min = self.width as u64;
        for view in self.edit_views.iter() {
            min = std::cmp::min(min, view.element_width(self.width));
        }
        min
    }

    fn recalculate_seek(&mut self) {
        /*
         *
         * file:
         *  xXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxXxX
         * seek:
         *          |-----------------------|
         * render_lim:               |
         * cursor:             |
         *
         */
        let hex_view_height = self.lines_to_draw();
        let bytes_per_line = self.bytes_per_line();
        let render_lim = bytes_per_line * hex_view_height;
        if self.cursor >= self.seek + render_lim { // know a priori that buf size is height * width. TODO: fix.
            // 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 % bytes_per_line) - render_lim + bytes_per_line;
        } else if self.cursor < self.seek {
            // we've sought before the start, so reset seek to just before.
            self.seek = self.cursor - (self.cursor % bytes_per_line);
        }
    }
}

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 hexmode = HexMode { sub_elem_idx: 0 };
            let mut binmode = BinaryMode { sub_elem_idx: 0 };

            let mut state = Program {
                filename: filename.to_string(),
                width: w,
                height: h,
                old_term: termios,
                new_term: new_termios,
                cursor: 0,
                seek: 0,
//                screen:  &mut std::io::stdout(),
                screen: &mut AlternateScreen::from(std::io::stdout().into_raw_mode().unwrap()),
                view: &mut CachingFileView::new(filename).unwrap(),
                state: Mode::Edit,
                status: "".to_string(),
                input_buf: Vec::with_capacity(0),
                edits: Edits::new(),
                edit_views: vec![
                    &mut hexmode,
                    &mut binmode
                ],
                current_edit_idx: 0
            };

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

            print!("{}", termion::cursor::Hide);
            interface_loop(&mut state);
            print!("{}", termion::cursor::Show);

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

enum Mode {
    Edit,
    ReadAddress
}

fn interface_loop(state: &mut Program) {
    render_interface(state);

    let stdin = std::io::stdin();

    for input in stdin.events() {
        match state.state {
            Mode::Edit => {
                match input.unwrap() {
                    Event::Key(Key::Char('\n')) => {
                        state.state = Mode::ReadAddress;
                    }
                    Event::Key(Key::Up) => {
                        let amount = state.bytes_per_line(); // why can't this be inlined?
                        state.dec_cursor(amount as u64);
                    }
                    Event::Key(Key::Down) => {
                        let amount = state.bytes_per_line();
                        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.bytes_per_line() * state.lines_to_draw();
                        if state.view.size() - state.cursor < amount {
                            state.cursor = state.view.size() - 1;
                            state.seek = std::cmp::min(
                                state.view.size() - (state.view.size() % state.bytes_per_line()),
                                state.seek + amount
                            )
                        } else {
                            state.cursor += amount;
                            state.seek += amount;
                        }
                    }
                    Event::Key(Key::PageUp) => {
                        let amount = state.bytes_per_line() * state.lines_to_draw();
                        if state.cursor < amount {
                            state.cursor = 0;
                            state.seek = 0;
                        } else if state.seek < amount {
                            state.cursor -= amount;
                            state.seek = 0;
                        } else {
                            state.cursor -= amount;
                            state.seek -= amount;
                        }
                    }
                    Event::Key(Key::Char('q')) => {
                        break;
                    }
                    Event::Key(Key::Ctrl('\t')) => {
                        // switch to previous edit mode
                    }
                    Event::Key(Key::Ctrl(x)) => {
                        state.status = format!("ctrl {}", x);
                    }
                    Event::Key(Key::Char('\t')) => {
                        // switch to next edit mode
                    }
                    // would prefer shift+t
                    Event::Unsupported(vec) => {
                        if vec.len() == 3 && vec[0] == 0x1b && vec[1] == 0x4f {
                            match vec[2] {
                                0x41 => {
                                    state.status = "ctrl up".to_owned();
                                    state.edit_views[state.current_edit_idx].inc_sub_elem(1);
                                    /* up */
                                }
                                0x42 => {
                                    state.status = "ctrl down".to_owned();
                                    /* down */
                                }
                                0x43 => {
                                    state.status = "ctrl right".to_owned();
                                    /* right */
                                }
                                0x44 => {
                                    state.status = "ctrl left".to_owned();
                                    /* left */
                                }
                                _ => {
                                    state.status = format!("ctrl? {:?}", vec);
                                }
                            }
                        } else {
                            // thought shift+arrow would end up here, but.. nope
                            state.status = format!("ctrl? {:?}", vec);
                        }
                    }
                    Event::Key(Key::Char(x)) => {
                        // TODO: how does this work on non-US keyboards? keyboards without a-fA-F?
                        if (x >= '0' && x <= '9') || (x >= 'a' && x <= 'f') || (x >= 'A' && x <= 'F') {
                            state.edits.record(state.cursor, x as u8);
                            // edit the nibble under the cursor
                        }
                    }
                    Event::Key(Key::Backspace) => {
                        state.edits.remove(state.cursor);
                        state.dec_cursor(1);
                    }
                    _ => { }
                }
            }
            Mode::ReadAddress => {
                match input.unwrap() {
                    Event::Key(Key::Char('\n')) => {
                        let buf_str = state.input_buf.iter().cloned().collect::<String>();
                        if buf_str.len() == 0 {
                            state.input_buf = Vec::with_capacity(0);
                            state.state = Mode::Edit;
                            state.status = " ".to_string();
                            continue;
                        }
                        let addr_str = u64::from_str_radix(&buf_str, 16);
                        match addr_str {
                            Ok(addr) => {
                                if addr < state.view.size() {
                                    state.seek_to(addr);
                                    state.input_buf = Vec::with_capacity(0);
                                    state.state = Mode::Edit;
                                    state.status = " ".to_string();
                                } else {
                                    state.status = format!("Address out of bounds: 0x{:x}", addr);
                                    state.input_buf = Vec::with_capacity(0);
                                    state.state = Mode::Edit;
                                }
                            }
                            Err(s) => {
                                state.status = format!("Unable to parse address '{}', error: {}", buf_str, s);
                                state.input_buf = Vec::with_capacity(0);
                                state.state = Mode::Edit;
                            }
                        }
                    }
                    Event::Key(Key::Esc) => {
                        state.input_buf = Vec::with_capacity(0);
                        state.state = Mode::Edit;
                    }
                    Event::Key(Key::Backspace) => {
                        if state.input_buf.len() > 0 {
                            state.input_buf.pop();
                        }
                    }
                    Event::Key(Key::Char(x)) => {
                        if (x >= '0' && x <= '9') || (x >= 'a' && x <= 'f') || (x >= 'A' && x <= 'F') {
                            if state.input_buf.len() < MODAL_WIDTH - 6 {
                                state.input_buf.push(x);
                            }
                        }
                    }
                    _ => { }
                }
            }
        }
        render_interface(state);
    }
}

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: &mut Program) {
//    println!("{}", clear::All);
    write!(state.screen, "{}{}", cursor::Goto(1, 1), clear::CurrentLine).unwrap();
    let bufsz = state.lines_to_draw() * state.bytes_per_line();
    writeln!(state.screen, "Dimensions: {}x{}    Seek: 0x{:x}, Cursor: 0x{:x}  - file: {}, 0x{:x} bytes", state.width, state.height, state.seek, state.cursor, state.filename, state.view.size()).unwrap();
    if state.status.len() > 0 {
        writeln!(state.screen, "{}{}  {}", cursor::Goto(1, 2), clear::CurrentLine, state.status).unwrap();
        state.status = "".to_string();
    }

    let buffer = state.view.get_bytes(state.seek, bufsz);

    // buffer is one screen of bytes, starting at seek.

    let start = (state.seek) as usize;

    let mut iface = String::new();

    let width = state.bytes_per_line();

    for i in 0..state.lines_to_draw() {
        for j in 0..state.edit_views.len() {
            let view = &state.edit_views[j];
            let slice_start = width * i;
            let slice_end = slice_start + width;
            write!(iface, "{}", view.render_bytes(state.cursor, state.width, start as u64 + slice_start, buffer[(slice_start as usize)..(slice_end as usize)].iter())).unwrap();
            if i < state.lines_to_draw() - 1 || j < (state.edit_views.len() - 1) {
                write!(iface, "\n").unwrap();
            }
        }
    }
    let height = state.view_interface_height() as u16;
    write!(state.screen, "{}{}", cursor::Goto(1, height + 1), iface).unwrap();
    match state.state {
        Mode::ReadAddress => {
            let xmid = state.width as u16 / 2;
            let ymid = state.height as u16 / 2;
            write!(state.screen, "{}{:-^2$}", cursor::Goto(xmid-12, ymid-2), "", MODAL_WIDTH).unwrap();
            write!(state.screen, "{}|{: ^2$}|", cursor::Goto(xmid-12, ymid-1), "Enter new addresss", MODAL_WIDTH - 2).unwrap();
            write!(state.screen, "{}| >{:_^2$}  |", cursor::Goto(xmid-12, ymid-0), "", MODAL_WIDTH - 6).unwrap();
            write!(state.screen, "{}|{: ^2$}|", cursor::Goto(xmid-12, ymid+1), "", MODAL_WIDTH - 2).unwrap();
            write!(state.screen, "{}{:-^2$}", cursor::Goto(xmid-12, ymid+2), "", MODAL_WIDTH).unwrap();
            write!(state.screen, "{}{}", cursor::Goto(xmid-9, ymid-0), state.input_buf.iter().cloned().collect::<String>()).unwrap();
        }
        _ => {}
    }
    state.screen.flush().unwrap();
}