use std::hint::unreachable_unchecked;
use std::io::Error;
use std::process::Command as Executable;

use crossterm::event::KeyCode;
use tui::layout::Rect;

use crate::command::Command;
use crate::command_output::CommandOutput;
use crate::directory::Directory;
use crate::pane::{Message, Pane};
use crate::terminal::Terminal;

enum Either<T, U> {
    Cmd(T),
    CmdOut(U),
}

pub struct State {
    dir: Directory,
    size: Rect,
    command: Option<Either<Command, CommandOutput>>
}
impl State {
    pub fn new(area: Rect) -> Self {
        let dir = Directory::new("root".into());
        Self {
            dir,
            size: area,
            command: None,
        }
    }

    pub fn render(&self, terminal: &mut Terminal) -> Result<(), Error> {
        let command_size = match &self.command {
            None => 0,
            Some(e) => match e {
                Either::Cmd(c) => c.lines_hint(),
                Either::CmdOut(o) => o.lines_hint(),
            }
        };

        let (dir_area, bottom_area) = if command_size > 0 {
            (Rect {
                height: self.size.height - command_size as u16 - 2,
                ..self.size
            }, Rect {
                y: self.size.height - command_size as u16 - 2,
                height: command_size as u16 + 2,
                ..self.size
            })
        } else {
            (self.size, self.size)
        };
        
        terminal.draw(
            |output| {
                self.dir.display(output, dir_area);
                if let Some(command) = self.command.as_ref() {
                    match command {
                        Either::Cmd(cmd) => cmd.display(output, bottom_area),
                        Either::CmdOut(cmd) => cmd.display(output, bottom_area),
                    }
                }
            }
        )?;

        Ok(())
    }

    const fn current_pane(&self) -> &dyn Pane {
        match self.command.as_ref() {
            None => &self.dir,
            Some(either) => match either {
                Either::Cmd(c) => c,
                Either::CmdOut(o) => o,
            }
        }
    }

    pub fn cursor_position(&self) -> Option<(u16, u16)> {
        let pane = self.current_pane();

        let (x, y) = pane.cursor_position()?;
        let new_x = x + 1;
        let dy = if let Some(Either::Cmd(c)) = &self.command {
            self.size.height - c.lines_hint() as u16 - 2
        } else {
            self.size.y
        };
        let new_y = y + dy + 1;

        Some((new_x, new_y))
    }

    pub fn update(&mut self, key: KeyCode) -> Message {
        match self.command.as_mut() {
            None => self.dir.update(key),
            Some(either) => match either {
                Either::Cmd(c) => c.update(key),
                Either::CmdOut(_) => { self.close_window(); Message::Nothing },
            }
        }
    }

    pub fn begin_command(&mut self) {
        self.command = Some(Either::Cmd(Command::new()));
    }

    pub fn execute_command(&mut self) {
        let Some(Either::Cmd(cmd)) = self.command.take()
        else { unsafe { unreachable_unchecked() } };

        let mut iter = cmd.buf()
            .split(' ');

        let prog_name = iter.next().unwrap();
        let output = Executable::new(prog_name)
            .args(iter)
            .output();

        let command_output = CommandOutput::new(output.map(|o| o.stdout));
        if !command_output.should_display() {
            return;
        }

        self.command = Some(Either::CmdOut(command_output));
    }

    pub fn cancel_command(&mut self) {
        self.command = None;
    }

    pub fn close_window(&mut self) {
        self.command = None;
    }
}