rs-kilo/src/editor.rs

//! Editor functionality
use crate::helpers::*;

use std::cmp::PartialEq;
use std::io;
use std::io::prelude::*;
use std::io::BufReader;

/// Main structure for the editor
///
/// impl blocks are split similarly to the original C implementation
#[derive(Debug, Default)]
pub struct Editor {
    cursor_x: usize,
    cursor_y: usize,
    screen_cols: usize,
    screen_rows: usize,
    output_buffer: String,
}

#[derive(Copy, Clone, Debug, PartialEq)]
enum EditorKey<T> {
    Escape,
    ArrowLeft,
    ArrowRight,
    ArrowUp,
    ArrowDown,
    DeleteKey,
    HomeKey,
    EndKey,
    PageUp,
    PageDown,
    OtherKey(T),
}

impl EditorKey<char> {
    pub fn unwrap(self) -> char {
        match self {
            self::OtherKey(val) => val,
            _ => panic!("called `EditorKey::unwrap()` on a `None` value"),
        }
    }
}

use self::EditorKey::*;

// init
impl Editor {
    pub fn new() -> Self {
        let mut instance = Self::default();
        let size = instance.get_window_size();
        instance.cursor_x = 0;
        instance.cursor_y = 0;
        instance.screen_cols = size.cols as usize;
        instance.screen_rows = size.rows as usize;

        instance
    }
}

// Terminal
impl Editor {
    fn read_key(&mut self) -> Option<Vec<EditorKey<char>>> {
        let stdin = io::stdin();
        let stdin = stdin.lock();
        let mut in_str = String::new();
        let mut input = BufReader::with_capacity(3, stdin);
        input.read_to_string(&mut in_str).unwrap();

        let mut output: Vec<EditorKey<char>> = vec![];

        for char in in_str.chars() {
            output.push(match char {
                '\x1b' => Escape,
                _ => OtherKey(char),
            });
        }

        if output.len() == 0 {
            return None;
        }

        if output[0].eq(&Escape) {
            if output.len() == 4 {
                if output[3].eq(&OtherKey('~')) {
                    let action = match output[2].unwrap() {
                        '1' => HomeKey,
                        '3' => DeleteKey,
                        '4' => EndKey,
                        '5' => PageUp,
                        '6' => PageDown,
                        '7' => HomeKey,
                        '8' => EndKey,
                        _ => Escape,
                    };

                    return Some(vec![action]);
                }
            }
            if output[1].eq(&OtherKey('[')) {
                let action = match output[2] {
                    OtherKey('A') => ArrowUp,
                    OtherKey('B') => ArrowDown,
                    OtherKey('C') => ArrowRight,
                    OtherKey('D') => ArrowLeft,
                    OtherKey('H') => HomeKey,
                    OtherKey('F') => EndKey,

                    // Eh, just return escape otherwise
                    _ => return Some(vec![Escape]),
                };

                return Some(vec![action]);
            }
            if output[1].eq(&OtherKey('O')) {
                let action = match output[2] {
                    OtherKey('H') => HomeKey,
                    OtherKey('F') => EndKey,
                    _ => Escape,
                };

                return Some(vec![action]);
            }
        }



        return Some(output);
    }

    fn get_window_size(&mut self) -> TermSize {
        match get_term_size() {
            Some(size) => size,
            None => unimplemented!("The easy way usually works")
        }
    }
}

// Input
impl Editor {
    fn move_cursor(&mut self, key: &EditorKey<char>) {
        match key {
            ArrowLeft => {
                if self.cursor_x != 0 {
                    self.cursor_x -= 1;
                }
            },
            ArrowRight => {
                if self.cursor_x != self.screen_cols - 1 {
                    self.cursor_x += 1;
                }
            },
            ArrowUp => {
                if self.cursor_y != 0 {
                    self.cursor_y -= 1;
                }
            },
            ArrowDown => {
                if self.cursor_y != self.screen_rows - 1 {
                    self.cursor_y += 1;
                }
            },
            _ => (),
        };
    }

    /// Route user input to the appropriate handler method
    pub fn process_keypress(&mut self) -> Option<()> {
        let chars = self.read_key();
        if chars.is_none() {
            Some(()) // Continue input loop on empty input
        } else {
            let chars = chars.unwrap();
            // print!("{:?}\r\n", &chars);
            let first = &chars[0];

            match first {
                OtherKey(c) => {
                    if c == &ctrl_key('q') {
                        print!("\x1b[2J");
                        print!("\x1b[H");
                        // Break out of the input loop
                        return None;
                    }
                },
                HomeKey => {
                    self.cursor_x = 0;
                },
                EndKey => {
                    self.cursor_x = self.screen_cols - 1;
                },
                PageUp => self.page_up_or_down(PageUp),
                PageDown => self.page_up_or_down(PageDown),
                ArrowUp => self.move_cursor(&ArrowUp),
                ArrowDown => self.move_cursor(&ArrowDown),
                ArrowLeft => self.move_cursor(&ArrowLeft),
                ArrowRight => self.move_cursor(&ArrowRight),
                _ => (),
            };

            // Continue the main input loop
            Some(())
        }
    }

    fn page_up_or_down(&mut self, key: EditorKey<char>) {
       let mut times = self.screen_rows;

        while times > 1 {
            times -= 1;
            match key {
                PageUp => self.move_cursor(&ArrowUp),
                PageDown => self.move_cursor(&ArrowDown),
                _ => (),
            }
        }
    }
}

// Output
impl Editor {
    /// Equivalent of the abAppend function
    /// in the original tutorial, just appends
    /// to the `output_buffer` String in the
    /// editor struct.
    fn append_out(&mut self, str: &str) {
        self.output_buffer.push_str(str);
    }

    fn draw_rows(&mut self) {
        for y in 0..self.screen_rows {
            if y == (self.screen_rows / 3) {
                let mut welcome = format!("Kilo editor -- version {}", env!("CARGO_PKG_VERSION"));
                if welcome.len() > self.screen_cols {
                    welcome.truncate(self.screen_cols)
                }

                // Center welcome message
                let mut padding = (self.screen_cols - welcome.len()) / 2;
                if padding > 0 {
                    self.append_out("~");
                    padding -= 1;
                }
                while padding > 0 {
                    self.append_out(" ");
                    padding -=1;
                }

                self.append_out(&welcome);
            } else {
                self.append_out("~");
            }

            self.append_out("\x1b[K");
            if y < (self.screen_rows - 1) {
                self.append_out("\r\n");
            }
        }
    }

    pub fn refresh_screen(&mut self) -> io::Result<()> {
        self.output_buffer.clear();

        //  Hide cursor, reposition cursor
        //self.append_out("\x1b[?25l");
        //self.append_out("\x1b[H");

        self.draw_rows();

        // Move cursor to state position
        let cursor_code = format!("\x1b[{};{}H", self.cursor_y + 1, self.cursor_x + 1);
        self.append_out(&cursor_code);

        // Show cursor
        self.append_out("\x1b[?25h");

        let stdout = io::stdout();
        let mut handle = stdout.lock();
        handle.write_all(&self.output_buffer.as_bytes())
    }
}