// Dancing Droids
// Copyright (C) 2020  Martin HART, Volodymyr PATUTA, Stephane Elias BENABDESLAM
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.

use clap::{App, Arg};
use std::collections::HashMap;
use std::fs;
use std::io;

mod robot;
mod world;

/// Check if the robot is in the map.
fn check_map(r: &robot::Robot, w: &world::World) -> Result<(), String> {
    if r.p.x < 0 || r.p.y < 0 || r.p.x > w.x || r.p.y > w.y {
        Err(format!("The robot {} is off map", r.id))
    } else {
        Ok(())
    }
}

/// Check if the robot collide with another one at the given position.
fn check_collisions(r: &robot::Robot, h: &HashMap<robot::Position, u32>) -> Result<(), String> {
    match h.get(&r.p) {
        Some(&x) => Err(format!(
            "The robot id: {} collided with robot id: {} in position: ({};{}) !",
            &r.id, x, &r.p.x, &r.p.y
        )),
        None => Ok(()),
    }
}

fn create_hash_map(pool: &Vec<robot::Robot>, hash: &mut HashMap<robot::Position, u32>) {
    for r in pool {
        hash.insert(robot::Position { x: r.p.x, y: r.p.y }, r.id);
    }
}

/// Parse the config file, generate the world and robot pool.
fn parse_config(conf: String, pool: &mut Vec<robot::Robot>) -> Result<world::World, String> {
    let mut lines = conf.lines();
    // The first line of the config file should be the World.
    let raw_line: &str = match lines.next() {
        Some(raw) => raw,
        None => {
            return Err(String::from(
                "Could not read the first line of the config file !",
            ))
        }
    };
    let mut tokens = raw_line.split_whitespace();
    let token1 = match tokens.next() {
        Some(raw) => raw,
        None => {
            return Err(String::from(
                "Could not read the first token of the first line !",
            ))
        }
    };
    let token2 = match tokens.next() {
        Some(raw) => raw,
        None => {
            return Err(String::from(
                "Could not read the second token of the first line !",
            ))
        }
    };
    let x: i32 = match token1.parse::<i32>() {
        Ok(x) => x,
        Err(_) => {
            return Err(String::from(
                "Could not convert token one from the first string to i32",
            ))
        }
    };
    let y: i32 = match token2.parse::<i32>() {
        Ok(x) => x,
        Err(_) => {
            return Err(String::from(
                "Could not convert token two from the first string to i32",
            ))
        }
    };
    let w = world::World { x, y };
    let mut r_id: u32 = 0;
    loop {
        r_id += 1;
        // This line should be empty.
        let empty_line = match lines.next() {
            None => break,
            Some(x) => x,
        };
        if !empty_line.is_empty() {
            return Err(String::from("This line should be empty !"));
        }
        let raw_setup = match lines.next() {
            None => return Err(String::from("This line should be the config !")),
            Some(raw) => raw,
        };
        if raw_setup.is_empty() {
            return Err(String::from("This line should not be empty !"));
        }
        let raw_inst = match lines.next() {
            None => return Err(String::from("This line should be the instruction !")),
            Some(raw) => raw,
        };
        if raw_inst.is_empty() {
            return Err(String::from("This line should not be empty !"));
        }
        // Parse the setup line of the robot.
        let mut setup = raw_setup.split_whitespace();
        let pos_x = match setup.next() {
            None => {
                return Err(String::from(
                    "Could not read the first token of the setup line !",
                ))
            }
            Some(raw) => raw,
        };
        let pos_y = match setup.next() {
            None => {
                return Err(String::from(
                    "Could not read the second token of the setup line !",
                ))
            }
            Some(raw) => raw,
        };
        let orientation = match setup.next() {
            None => {
                return Err(String::from(
                    "Could not read the third token of the setup line !",
                ))
            }
            Some(raw) => raw,
        };
        // Convert values of the setup line
        let r_x = match pos_x.parse::<i32>() {
            Err(_) => {
                return Err(String::from(
                    "Could not convert the first token of the setup ligne to i32 !",
                ))
            }
            Ok(raw) => raw,
        };
        let r_y = match pos_y.parse::<i32>() {
            Err(_) => {
                return Err(String::from(
                    "Could not convert the second token of the setup ligne to i32 !",
                ))
            }
            Ok(raw) => raw,
        };
        let r_o = match orientation {
            "N" => robot::Orientation::N,
            "E" => robot::Orientation::E,
            "S" => robot::Orientation::S,
            "W" => robot::Orientation::W,
            _ => {
                return Err(String::from(
                    "The third token of the setup line do not match any orientations !",
                ))
            }
        };

        // Convert instructions line.
        let inst: Vec<char> = raw_inst.chars().rev().collect();
        if !robot::is_instructions(&inst) {
            return Err(String::from("Invalid instructions !"));
        }

        let r = robot::Robot::new(r_id, r_o, robot::Position { x: r_x, y: r_y }, inst);

        // Load robot inside the pool.
        match check_map(&r, &w) {
            Ok(()) => pool.push(r),
            Err(err) => return Err(err),
        }
    }

    Ok(w)
}

/// 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"))?;

    let mut robot_pool: Vec<robot::Robot> = Vec::new();
    let world: world::World = parse_config(raw_conf, &mut robot_pool)?;
    let mut hash: HashMap<robot::Position, u32> = HashMap::new();
    create_hash_map(&robot_pool, &mut hash);

    loop {
        let mut piouff: u32 = 0;
        for mut r in robot_pool {
            if robot::is_piouff(&r) {
                piouff += 1;
            } else {
                r.execute_instruction();
            }
            check_map(&r, &world)?;
            check_collisions(&r, &hash)?;
        }
        if piouff == robot_pool.len() as u32 {
            break;
        }
    }

    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    #[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_check_map() {
        let r = robot::Robot::new(
            0,
            robot::Orientation::N,
            robot::Position { x: 2, y: 3 },
            vec!['F'],
        );
        let w = world::World { x: 10, y: 10 };

        assert!(check_map(&r, &w).is_ok());
    }

    #[test]
    #[should_panic]
    fn test_check_map_fail() {
        let r = robot::Robot::new(
            0,
            robot::Orientation::N,
            robot::Position { x: 2, y: 4 },
            vec!['F'],
        );
        let w = world::World { x: 3, y: 3 };

        assert!(check_map(&r, &w).is_ok());
    }

    #[test]
    #[should_panic]
    fn test_check_collisions() {
        let r = robot::Robot::new(
            0,
            robot::Orientation::N,
            robot::Position { x: 2, y: 3 },
            vec!['F'],
        );

        let mut h: HashMap<robot::Position, u32> = HashMap::new();
        h.insert(robot::Position { x: 2, y: 3 }, 1);
        assert!(check_collisions(&r, &h).is_ok());
    }
}