use std::{path, fs};
use std::fs::File;
use std::io::Read;
use std::io::Write;
use std::collections::HashMap;

#[derive(Debug)]
pub enum Error {
    ConfigNotFound,
    Io(std::io::Error),
    InvalidConfig(ParseError)
}

#[derive(Debug)]
pub enum ParseError {
    UnknownSymbol(u32),
    MissingCommand(u32),
}

impl From<std::io::Error> for Error {
    fn from(val: std::io::Error) -> Self {
        if val.kind() == std::io::ErrorKind::NotFound {
            Error::ConfigNotFound
        } else {
            Error::Io(val)
        }
    }
}

#[derive(Debug)]
pub struct Hotkey {
    keysyms: Vec<evdev::Key>,
    command: String
}

impl Hotkey {
    fn new(keysyms: Vec<evdev::Key>, command: String) -> Self {
        Hotkey {
            keysyms,
            command
        }
    }
}

pub fn load_file_contents(path: path::PathBuf)
    -> Result<String, Error> {
    let mut file = File::open(path)?;
    let mut contents = String::new();
    file.read_to_string(&mut contents)?;
    Ok(contents)
}

pub fn parse_contents(path: path::PathBuf) -> Result<Vec<Hotkey>, Error> {

    // Find file
    let mut file = File::open(path)?;
    let mut contents = String::new();
    file.read_to_string(&mut contents)?;

    let key_to_evdev_key: HashMap<&str, evdev::Key> = HashMap::from([
        ("q", evdev::Key::KEY_Q), ("w", evdev::Key::KEY_W),
        ("e", evdev::Key::KEY_E), ("r", evdev::Key::KEY_R),
        ("t", evdev::Key::KEY_T), ("y", evdev::Key::KEY_Y),
        ("u", evdev::Key::KEY_U), ("i", evdev::Key::KEY_I),
        ("o", evdev::Key::KEY_O), ("p", evdev::Key::KEY_P),

        ("a", evdev::Key::KEY_A), ("s", evdev::Key::KEY_S),
        ("d", evdev::Key::KEY_D), ("f", evdev::Key::KEY_F),
        ("g", evdev::Key::KEY_G), ("h", evdev::Key::KEY_H),
        ("j", evdev::Key::KEY_J), ("k", evdev::Key::KEY_K),
        ("l", evdev::Key::KEY_L),

        ("z", evdev::Key::KEY_Z), ("x", evdev::Key::KEY_X),
        ("c", evdev::Key::KEY_C), ("v", evdev::Key::KEY_V),
        ("b", evdev::Key::KEY_B), ("n", evdev::Key::KEY_N),
        ("m", evdev::Key::KEY_M),

        ("1", evdev::Key::KEY_1), ("2", evdev::Key::KEY_2),
        ("3", evdev::Key::KEY_3), ("4", evdev::Key::KEY_4),
        ("5", evdev::Key::KEY_5), ("6", evdev::Key::KEY_6),
        ("7", evdev::Key::KEY_7), ("8", evdev::Key::KEY_8),
        ("9", evdev::Key::KEY_9), ("0", evdev::Key::KEY_0),
    ]);

    let lines: Vec<&str> = contents.split("\n").collect();
    let mut hotkeys: Vec<Hotkey> = Vec::new();

    let mut lines_to_skip: u32 = 0;

    // Parse file line-by-line
    for i in 0..lines.len() {
        if lines_to_skip > 0 {
            lines_to_skip -= 1;
            continue;
        }

        // Ignore blank lines and comments starting with #
        if lines[i].trim().is_empty() ||
           lines[i].trim().starts_with("#")
           {
            continue;
        }

        // We need to get the real line number for errors
        // because arrays in Rust are zero-index while lines
        // in a file are of course counted from 1
        let real_line_no: u32 = (i + 1).try_into().unwrap();

        let mut key_presses: Vec<evdev::Key> = Vec::new();

        if key_to_evdev_key.contains_key(lines[i].trim()) {

            // If the keybind line is at the very last line,
            // it's impossible for there to be a command
            if i >= lines.len() - 1 {
                return Err(Error::InvalidConfig(
                        ParseError::MissingCommand(real_line_no)));
            }

            // Translate keypress into evdev key
            let key_press = key_to_evdev_key.get(lines[i].trim()).unwrap();

            key_presses.push(*key_press);

            //// Find the command
            if lines[i + 1].trim().is_empty() {
                return Err(Error::InvalidConfig(
                        ParseError::MissingCommand(real_line_no)));
            }

            let command = lines[i + 1].trim();

            // Push a new hotkey to the hotkeys vector
            hotkeys.push(Hotkey::new(key_presses, String::from(command)));

            // Skip trying to parse the next line (command)
            // because we already dealt with it
            lines_to_skip += 1;

        } else {
            return Err(Error::InvalidConfig(
                    ParseError::UnknownSymbol(real_line_no)));
        }
    }


    // If all is ok, return Vec<Hotkeys>
    return Ok(hotkeys);
}

#[cfg(test)]
mod tests {
    use super::*;

    // Implement a struct for a path used in tests
    // so that the test file will be automatically removed
    // no matter how the test goes
    struct TestPath {
        path: path::PathBuf
    }

    impl TestPath {
        fn new(path: &str) -> Self {
            TestPath {
                path: path::PathBuf::from(path)
            }
        }

        // Create a path method for a more succinct way
        // to deal with borrowing the path value
        fn path(&self) -> path::PathBuf {
            self.path.clone()
        }
    }

    impl Drop for TestPath {
        fn drop(self: &mut TestPath) {
            fs::remove_file(self.path());
        }
    }

    #[test]
    fn test_nonexistent_file() {
        let path = path::PathBuf::from(r"This File Doesn't Exist");

        let result = load_file_contents(path);

        assert!(result.is_err());

        match result.unwrap_err() {
            Error::ConfigNotFound => {
                return;
            },
            _ => {
                panic!("Error type for nonexistent file is wrong.");
            }
        }
    }

    #[test]
    fn test_existing_file() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file1");
        // Build a dummy file in /tmp
        let mut f = File::create(setup.path())?;
        f.write_all(b"
x
    dmenu_run

q
    bspc node -q")?;

        let result = load_file_contents(setup.path());
        assert!(result.is_ok());

        Ok(())
    }

    #[test]
    fn test_basic_keybind() -> std::io::Result<()> {
        let contents = "
r
    alacritty
            ";

        let expected_hotkey = Hotkey::new(vec![evdev::Key::KEY_R],
                                            String::from("alacritty"));

        let parse_result = parse_contents(contents);

        assert!(parse_result.is_ok());

        let parse_result = parse_result.unwrap();

        assert_eq!(parse_result[0].keysyms,
                   expected_hotkey.keysyms);

        assert_eq!(parse_result[0].command,
                   expected_hotkey.command);

        Ok(())
    }

    #[test]
    fn test_multiple_keybinds() -> std::io::Result<()> {
        let contents = "
r
    alacritty

w
    kitty

t
    /bin/firefox
        ";

        let hotkey_1 = Hotkey::new(vec![evdev::Key::KEY_R],
                                     String::from("alacritty"));
        let hotkey_2 = Hotkey::new(vec![evdev::Key::KEY_W],
                                     String::from("kitty"));
        let hotkey_3 = Hotkey::new(vec![evdev::Key::KEY_T],
                                     String::from("/bin/firefox"));

        let result = parse_contents(contents);
        assert!(result.is_ok());
        let result = result.unwrap();

        assert_eq!(hotkey_1.keysyms, result[0].keysyms);
        assert_eq!(hotkey_1.command, result[0].command);
        assert_eq!(hotkey_2.keysyms, result[1].keysyms);
        assert_eq!(hotkey_2.command, result[1].command);
        assert_eq!(hotkey_3.keysyms, result[2].keysyms);
        assert_eq!(hotkey_3.command, result[2].command);

        Ok(())
    }

    #[ignore]
    fn test_comments() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file4");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
r
    alacritty

w
    kitty

#t
    #/bin/firefox
        ")?;

        let expected_keybinds = vec![
            Hotkey::new(vec![evdev::Key::KEY_R],
                         String::from("alacritty")),
            Hotkey::new(vec![evdev::Key::KEY_W],
                         String::from("kitty")),
        ];

        let result = parse_contents(setup.path());
        assert!(result.is_ok());
        let result = result.unwrap();

        assert_eq!(result.len(), 2);

        assert_eq!(result[0].keysyms, expected_keybinds[0].keysyms);
        assert_eq!(result[0].command, expected_keybinds[0].command);
        assert_eq!(result[1].keysyms, expected_keybinds[1].keysyms);
        assert_eq!(result[1].command, expected_keybinds[1].command);

        Ok(())
    }

    #[ignore]
    fn test_multiple_keypress() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file5");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
super + 5
    alacritty
        ")?;

        let expected_keybinds = vec![

            // I don't know if the super key is macro or not,
            // please check
            Hotkey::new(vec![evdev::Key::KEY_MACRO, evdev::Key::KEY_5],
                         String::from("alacritty")),
        ];

        let result = parse_contents(setup.path());
        assert!(result.is_ok());
        let result = result.unwrap();

        assert_eq!(result[0].keysyms, expected_keybinds[0].keysyms);
        assert_eq!(result[0].command, expected_keybinds[0].command);

        Ok(())
    }

    #[ignore]
    fn test_command_with_many_spaces() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file6");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
p
    xbacklight -inc 10 -fps 30 -time 200
        ")?;

        let expected_keybinds = vec![
            Hotkey::new(vec![evdev::Key::KEY_P],
                         String::from("xbacklight -inc 10 -fps 30 -time 200")),
        ];

        let result = parse_contents(setup.path());
        assert!(result.is_ok());
        let result = result.unwrap();

        assert_eq!(result[0].keysyms, expected_keybinds[0].keysyms);
        assert_eq!(result[0].command, expected_keybinds[0].command);

        Ok(())
    }

    #[ignore]
    fn test_invalid_keybinding() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file7");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
p
    xbacklight -inc 10 -fps 30 -time 200

pesto
    xterm
                    ")?;

        let result = parse_contents(setup.path());

        assert!(result.is_err());

        let error = result.unwrap_err();

        match error {
            Error::InvalidConfig(parse_err) => match parse_err {
                ParseError::UnknownSymbol(line_nr) => {
                    if line_nr == 5 {
                        return Ok(());
                    } else {
                        panic!("{}", format!("Error line is wrong, expected 4 but actual: {}",
                                       line_nr));
                    }
                },
                _ => {
                    panic!("Error type is not Unknown Symbol");
                }
            },
            _ => {
                panic!("Error type is not InvalidConfig");
            }
        }
    }

    #[ignore]
    fn test_eofed_keybinding() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file8");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
k
    xbacklight -inc 10 -fps 30 -time 200

c ")?;

        assert!(parse_contents(setup.path()).is_err());

        Ok(())
    }

    #[ignore]
    fn test_no_command() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file9");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
k
    xbacklight -inc 10 -fps 30 -time 200

w

                    ")?;

        assert!(parse_contents(setup.path()).is_err());

        Ok(())
    }

    #[ignore]
    fn test_all_alphanumeric() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file10");
        let mut f = File::create(setup.path())?;

        let symbols: [&str; 36] = ["a", "b", "c", "d", "e", "f", "g",
        "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r",
        "s", "t", "u", "v", "w", "x", "y", "z", "0", "1", "2",
        "3", "4", "5", "6", "7", "8", "9"];

        let keysyms: [evdev::Key; 36] = [
            evdev::Key::KEY_A, evdev::Key::KEY_B, evdev::Key::KEY_C,
            evdev::Key::KEY_D, evdev::Key::KEY_E, evdev::Key::KEY_F,
            evdev::Key::KEY_G, evdev::Key::KEY_H, evdev::Key::KEY_I,
            evdev::Key::KEY_J, evdev::Key::KEY_K, evdev::Key::KEY_L,
            evdev::Key::KEY_M, evdev::Key::KEY_N, evdev::Key::KEY_O,
            evdev::Key::KEY_P, evdev::Key::KEY_Q, evdev::Key::KEY_R,
            evdev::Key::KEY_S, evdev::Key::KEY_T, evdev::Key::KEY_U,
            evdev::Key::KEY_V, evdev::Key::KEY_W, evdev::Key::KEY_X,
            evdev::Key::KEY_Y, evdev::Key::KEY_Z, evdev::Key::KEY_0,
            evdev::Key::KEY_1, evdev::Key::KEY_2, evdev::Key::KEY_3,
            evdev::Key::KEY_4, evdev::Key::KEY_5, evdev::Key::KEY_6,
            evdev::Key::KEY_7, evdev::Key::KEY_8, evdev::Key::KEY_9,
        ];

        for symbol in &symbols {
            f.write_all(format!("{}\n    st\n", symbol).as_bytes())?;
        }

        let parse_result = parse_contents(setup.path());

        assert!(parse_result.is_ok());

        let actual_keybinds = parse_result.unwrap();

        assert_eq!(actual_keybinds.len(), 36);

        for i in 0..actual_keybinds.len() {
            assert_eq!(actual_keybinds[i].keysyms.len(), 1);
            assert_eq!(actual_keybinds[i].keysyms[0], keysyms[i]);
            assert_eq!(actual_keybinds[i].command, "st");
        }

        Ok(())
    }

    #[ignore]
    fn test_nonsensical_file() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file11");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
WE WISH YOU A MERRY RUSTMAS

                    ")?;

        assert!(parse_contents(setup.path()).is_err());

        Ok(())
    }

    #[ignore]
    fn test_valid_keybind_but_commented_command() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file12");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
5
    takeshot --now --verbose

p
    #commented out command
                    ")?;

        assert!(parse_contents(setup.path()).is_err());

        Ok(())
    }

    #[ignore]
    fn test_real_config_snippet() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file13");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
# reloads sxhkd configuration:
super + Escape
    pkill -USR1 -x sxhkd ; sxhkd &

# Launch Terminal
super + Return
    alacritty -t \"Terminal\" -e \"$HOME/.config/sxhkd/new_tmux_terminal.sh\"

# terminal emulator (no tmux)
super + shift + Return
    alacritty -t \"Terminal\"

# terminal emulator (new tmux session)
alt + Return
    alacritty -t \"Terminal\" -e \"tmux\"

ctrl + 0
    play-song.sh

super + minus
    play-song.sh album
                    ")?;

        let expected_result: Vec<Hotkey> = vec![
            Hotkey::new(
                vec![evdev::Key::KEY_LEFTMETA,
                     evdev::Key::KEY_ESC],
                     String::from("pkill -USR1 -x sxhkd ; sxhkd &")),
            Hotkey::new(
                vec![evdev::Key::KEY_LEFTMETA,
                     evdev::Key::KEY_ENTER],
                     String::from("alacritty -t \"Terminal\" -e \"$HOME/.config/sxhkd/new_tmux_terminal.sh\"")),
            Hotkey::new(
                vec![evdev::Key::KEY_LEFTMETA,
                     evdev::Key::KEY_LEFTSHIFT,
                     evdev::Key::KEY_ENTER],
                     String::from("alacritty -t \"Terminal\"")),
            Hotkey::new(
                vec![evdev::Key::KEY_LEFTALT,
                     evdev::Key::KEY_ENTER],
                     String::from("alacritty -t \"Terminal\" -e \"tmux\"")),
            Hotkey::new(
                vec![evdev::Key::KEY_LEFTCTRL,
                     evdev::Key::KEY_0],
                     String::from("play-song.sh")),
            Hotkey::new(
                vec![evdev::Key::KEY_LEFTMETA,
                     evdev::Key::KEY_MINUS],
                     String::from("play-song.sh album")),
        ];

        let real_result = parse_contents(setup.path());

        assert!(real_result.is_ok());

        let real_result = real_result.unwrap();

        assert_eq!(real_result.len(), expected_result.len());

        for i in 0..real_result.len() {
            assert_eq!(real_result[i].keysyms,
                       expected_result[i].keysyms);
            assert_eq!(real_result[i].command,
                       expected_result[i].command);
        }

        Ok(())
    }

    #[ignore]
    fn test_multiline_command() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file14");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
k
    mpc ls | dmenu | \\
    sed -i 's/foo/bar/g'
                    ")?;

        let expected_keybind = Hotkey::new(
            vec![evdev::Key::KEY_K],
            String::from("mpc ls | dmenu | sed -i 's/foo/bar/g'")
                                           );

        let real_keybind = parse_contents(setup.path());

        assert!(real_keybind.is_ok());

        let real_keybind = real_keybind.unwrap();

        assert_eq!(real_keybind.len(), 1);

        assert_eq!(real_keybind[0].keysyms, expected_keybind.keysyms);
        assert_eq!(real_keybind[0].command, expected_keybind.command);

        Ok(())
    }

    #[ignore]
    fn test_commented_out_keybind() -> std::io::Result<()> {
        let setup = TestPath::new("/tmp/swhkd-test-file15");
        let mut f = File::create(setup.path())?;
        f.write_all(b"
#w
    gimp
                    ")?;

        assert!(parse_contents(setup.path()).is_err());

        Ok(())
    }

    // TODO: Write these tests as needed.

    #[ignore]
    fn test_homerow_special_keys() -> std::io::Result<()> {Ok(())}

    #[ignore]
    fn test_numrow_special_keys() -> std::io::Result<()> {Ok(())}

    #[ignore]
    fn test_all_modifier_keys() -> std::io::Result<()> {Ok(())}

    #[ignore]
    fn test_mod_keys_after_normal_keys() -> std::io::Result<()> {Ok(())}

    #[ignore]
    fn test_plus_at_start_and_end_of_keybind() -> std::io::Result<()> {Ok(())}

    // Bracket expansion example:
    // `super + ctrl + {h,j,k,l}`
    // `    bspc node -p {westh,south,north,west}`
    #[ignore]
    fn test_bracket_expansion() -> std::io::Result<()> {Ok(())}

    // `super + {1-9}`
    // `    bspc desktop -f '^{1-9}'`
    #[ignore]
    fn test_bracket_expansion_numbers() -> std::io::Result<()> {Ok(())}

    #[ignore]
    fn test_unclosed_bracket_in_binding() -> std::io::Result<()> {Ok(())}

    #[ignore]
    fn test_bracket_in_binding_but_not_in_command()
        -> std::io::Result<()> {Ok(())}

    #[ignore]
    fn test_bracket_non_matching_counts() -> std::io::Result<()> {Ok(())}

    #[ignore]
    fn test_multiple_brackets() -> std::io::Result<()> {Ok(())}

    #[ignore]
    fn test_multiple_brackets_only_one_in_command()
        -> std::io::Result<()> {Ok(())}
}