use clap::{App, Arg};
use queues::*;
use std::fs;
use std::io;

/// Struct to store the world.
struct World {
    x: u32,
    y: u32,
    map: Vec<char>,
}

impl World {
    /// Create a new map full of dots.
    fn create(&mut self) {
        self.map = vec!['.'; (self.x * self.y) as usize];
    }
    /// Set robot on the map.
    fn set_robot(&mut self, r: Robot) {
        self.map[(r.p.x * r.p.y) as usize] = match r.o {
            Orientation::N => '↑',
            Orientation::S => '↓',
            Orientation::E => '→',
            Orientation::W => '←',
        }
    }
    /// Check if a position is free.
    fn empty_position(&mut self, p: Position) -> bool {
        self.map[(p.x * p.y) as usize] == '.'
    }
}

/// Struct to store robot position.
struct Position {
    x: i32,
    y: i32,
}

impl Position {
    /// Check if position is in the map.
    fn is_valid(self, w: World) -> Result<(), String> {
        if (self.x, self.y) > (0, 0) && (self.x, self.y) < (w.x as i32, w.y as i32) {
            Ok(())
        } else {
            Err(String::from("Invalid position."))
        }
    }
}

/// A Robot *aka droid* is represented here.
/// Each robot must have a unique id.
struct Robot {
    id: u32,
    o: Orientation,
    p: Position,
    q: Queue<char>,
}

impl Robot {
    /// Create a empty Robot.
    fn new() -> Robot {
        Robot {
            id: 0,
            o: Orientation::N,
            p: Position { x: 0, y: 0 },
            q: queue![],
        }
    }
    /// Initialize a new Robot.
    fn create(&mut self, id: u32, o: Orientation, p: Position, s: String) {
        let mut q: Queue<char> = queue![];
        for c in s.chars() {
            q.add(c);
        }
        self.id = id;
        self.o = o;
        self.p = p;
        self.q = q;
    }
    /// Apply forward instruction to the robot.
    fn move_forward(&mut self) {
        match self.o {
            Orientation::N => self.p.y -= 1,
            Orientation::S => self.p.y += 1,
            Orientation::E => self.p.x += 1,
            Orientation::W => self.p.x -= 1,
        }
    }
    /// Apply right instruction to the robot.
    fn move_right(&mut self) {
        match self.o {
            Orientation::N => self.p.x += 1,
            Orientation::S => self.p.x -= 1,
            Orientation::E => self.p.y += 1,
            Orientation::W => self.p.y -= 1,
        }
    }
    /// Apply left instruction to the robot.
    fn move_left(&mut self) {
        match self.o {
            Orientation::N => self.p.x -= 1,
            Orientation::S => self.p.x += 1,
            Orientation::E => self.p.y -= 1,
            Orientation::W => self.p.y += 1,
        }
    }
    /// Apply North orientation to the robot.
    fn set_north(&mut self) {
        self.o = Orientation::N
    }
    /// Apply South orientation to the robot.
    fn set_south(&mut self) {
        self.o = Orientation::S
    }
    /// Apply East orientation to the robot.
    fn set_east(&mut self) {
        self.o = Orientation::E
    }
    /// Apply West orientation to the robot.
    fn set_west(&mut self) {
        self.o = Orientation::W
    }
}

/// Enum to store all possible orientations.
enum Orientation {
    N,
    E,
    S,
    W,
}

/// Enum to store all possible instructions.
enum Instruction {
    L,
    R,
    F,
}

/// Parse char and return corresponding orientation.
fn parse_orientation(c: char) -> Result<Orientation, &'static str> {
    match c {
        'N' => Ok(Orientation::N),
        'E' => Ok(Orientation::E),
        'S' => Ok(Orientation::S),
        'W' => Ok(Orientation::W),
        _ => Err("Invalid character, does not match any orientations"),
    }
}

/// Parse char and return corresponding instruction.
fn parse_instruction(c: char) -> Result<Instruction, &'static str> {
    match c {
        'L' => Ok(Instruction::L),
        'R' => Ok(Instruction::R),
        'F' => Ok(Instruction::F),
        _ => Err("Invalid character, does not match any instructions"),
    }
}

/// Retrieve the content of a file and return it as a string.
fn open_file(filename: &str) -> io::Result<String> {
    let content = fs::read_to_string(filename)?;
    Ok(content)
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // We handle CLI flags here.
    let matches = App::new("DancingDroids")
        .version("0.1.0")
        .about("When droids dance togethers")
        .arg(
            Arg::with_name("file")
                .short("f")
                .long("file")
                .takes_value(true)
                .help("Configuration file"),
        )
        .get_matches();

    let raw_conf = open_file(matches.value_of("file").unwrap_or("two_robots.txt"))?;

    // We store all the robots inside a pool O_o
    let mut robot_pool: Vec<Robot> = Vec::new();

    Ok(())
}

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

    #[test]
    fn test_parse_orientation() {
        assert!(parse_orientation('N').is_ok());
        assert!(parse_orientation('E').is_ok());
        assert!(parse_orientation('S').is_ok());
        assert!(parse_orientation('W').is_ok());
        assert!(parse_orientation('Z').is_err());
    }

    #[test]
    fn test_parse_instruction() {
        assert!(parse_instruction('L').is_ok());
        assert!(parse_instruction('R').is_ok());
        assert!(parse_instruction('F').is_ok());
        assert!(parse_instruction('Z').is_err());
    }

    #[test]
    fn test_open_file() {
        assert!(open_file("two_robots.txt").is_ok());
        assert!(open_file("test_unexisting_file.extension").is_err());
    }

    #[test]
    fn test_create() {
        let mut w: World = World {
            x: 5,
            y: 5,
            map: Vec::new(),
        };
        w.create();
        assert_eq!(w.map, vec!['.'; 25]);
    }

    #[test]
    fn test_new_robot() {
        let mut r: Robot = Robot::new();
        assert_eq!(r.id, 0);
        assert!(matches!(r.o, Orientation::N));

        assert_eq!(r.p.x, 0);
        assert_eq!(r.p.y, 0);

        assert_eq!(r.q.size(), 0);
    }

    #[test]
    fn test_create_robot() {
        let mut r: Robot = Robot::new();
        r.create(1, Orientation::N, Position { x: 1, y: 1 }, "FF".to_string());
        assert_eq!(r.id, 1);
        assert!(matches!(r.o, Orientation::N));

        assert_eq!(r.p.x, 1);
        assert_eq!(r.p.y, 1);

        assert_eq!(r.q.peek(), Ok('F'));
        assert_eq!(r.q.peek(), Ok('F'));
    }

    #[test]
    fn test_set_robot() {
        let r = Robot {
            id: 0,
            o: Orientation::N,
            p: Position { x: 0, y: 0 },
            q: Queue::new(),
        };
        let mut w: World = World {
            x: 2,
            y: 2,
            map: Vec::new(),
        };
        w.create();
        w.set_robot(r);
        assert_eq!(w.map, vec!['↑', '.', '.', '.']);
    }

    #[test]
    fn test_move_robot() {
        let mut r: Robot = Robot {
            id: 0,
            o: Orientation::N,
            p: Position { x: 1, y: 1 },
            q: Queue::new(),
        };
        r.move_forward();
        assert_eq!(0, r.p.y);
        r.move_right();
        assert_eq!(2, r.p.x);
        r.move_left();
        assert_eq!(1, r.p.x);
    }

    #[test]
    fn test_empty_position() {
        let mut w: World = World {
            x: 2,
            y: 2,
            map: Vec::new(),
        };
        w.create();
        assert!(w.empty_position(Position { x: 0, y: 0 }));
    }
}