// 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/>.

extern crate pest;
#[macro_use]
extern crate pest_derive;

use clap::{App, Arg};
use pest::Parser;
use rand::Rng;
use std::collections::HashMap;
use std::fs;
use std::io;

mod robot;
mod world;

#[derive(Parser)]
#[grammar = "../conf.pest"]
pub struct ConfParser;

/// 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(()),
    }
}

/// Creates HashMap of robot position and it's id.
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);
    }
}

fn gen_random_instructions() -> String {
    let mut rng = rand::thread_rng();
    let n = rng.gen_range(5, 10);
    let mut instructions = String::with_capacity(n);
    const CHARSET: &[u8] = b"LRF";
    for _ in 0..n {
        let l = rng.gen_range(0, CHARSET.len());
        instructions.push(CHARSET[l] as char);
    }

    instructions
}

/// 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: Vec<&str> = conf.split('\n').collect();
    let raw_world = match ConfParser::parse(Rule::world, lines.remove(0)) {
        Ok(s) => s.as_str(),
        Err(e) => return Err(format!("{}", e)),
    };
    let mut w: Vec<i32> = Vec::with_capacity(2);
    for n in raw_world.split_whitespace() {
        let v: i32 = match n.parse::<i32>() {
            Ok(x) => x,
            Err(_) => return Err(String::from("World config is broken.")),
        };
        w.push(v);
    }
    let world = world::World { x: w[0], y: w[1] };
    lines.remove(0);
    let mut r_id: u32 = 0;
    loop {
        r_id += 1;
        if lines.len() == 0 {
            break;
        }
        let raw_setup = match ConfParser::parse(Rule::robot_init, lines.remove(0)) {
            Ok(s) => s.as_str(),
            Err(e) => return Err(format!("{}", e)),
        };

        let rand_instructions = gen_random_instructions();
        let l = lines.remove(0);

        let instructions = match ConfParser::parse(Rule::robot_instructions, l) {
            Ok(s) => s.as_str(),
            Err(_) => rand_instructions.as_str(),
        };

        let mut setup = raw_setup.split_whitespace();
        let pos_x = match setup.next() {
            Some(raw) => raw,
            None => {
                return Err(String::from(
                    "Could not read the first token of the setup line !",
                ))
            }
        };
        let pos_y = match setup.next() {
            Some(raw) => raw,
            None => {
                return Err(String::from(
                    "Could not read the second token of the setup line !",
                ))
            }
        };
        let orientation = match setup.next() {
            Some(raw) => raw,
            None => {
                return Err(String::from(
                    "Could not read the third token of the setup line !",
                ))
            }
        };
        // Convert values of the setup line
        let r_x = match pos_x.parse::<i32>() {
            Ok(raw) => raw,
            Err(_) => {
                return Err(String::from(
                    "Could not convert the first token of the setup ligne to i32 !",
                ))
            }
        };
        let r_y = match pos_y.parse::<i32>() {
            Ok(raw) => raw,
            Err(_) => {
                return Err(String::from(
                    "Could not convert the second token of the setup ligne to i32 !",
                ))
            }
        };
        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> = instructions.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, &world) {
            Ok(()) => pool.push(r),
            Err(err) => return Err(err),
        }

        if lines.len() == 0 {
            break;
        }
        if l.len() == 0 {
            continue;
        }
        lines.remove(0);
    }

    Ok(world)
}

/// 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)
}

/// Here we display the grid by looping in every position checking if it exists in the HashMap.
fn display_grid(
    w: &world::World,
    robot_pool: &Vec<robot::Robot>,
    h: &HashMap<robot::Position, u32>,
) {
    for i in (0..w.y).rev() {
        if i < 10 {
            print!("{}  ", i);
        } else {
            print!("{} ", i);
        }
        for j in 0..w.x {
            match h.get(&robot::Position { x: j, y: i }) {
                Some(id) => match robot_pool[(id - 1) as usize].o {
                    robot::Orientation::N => print!("↑  "),
                    robot::Orientation::E => print!("→  "),
                    robot::Orientation::S => print!("↓  "),
                    robot::Orientation::W => print!("←  "),
                },

                None => print!(".  "),
            }
        }
        println!();
    }
    print!("   ");
    for j in 0..w.x {
        if j < 10 {
            print!("{}  ", j);
        } else {
            print!("{} ", j);
        }
    }
    println!();
}

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"),
        )
        .arg(
            Arg::with_name("random-world")
                .long("random-world")
                .takes_value(false)
                .help("Generate random world"),
        )
        .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 = match matches.is_present("random-world") {
        false => parse_config(raw_conf, &mut robot_pool)?,
        true => world::random_world(),
    };

    let mut hash: HashMap<robot::Position, u32> = HashMap::new();
    create_hash_map(&robot_pool, &mut hash);
    println!("World {{ x_max = {}; y_max = {} }}", world.x, world.y);
    robot::print_robots(&robot_pool);
    println!("Initial state");
    println!("==============");
    display_grid(&world, &robot_pool, &hash);
    loop {
        let mut piouff: u32 = 0;
        for r in &mut robot_pool {
            if robot::is_piouff(&r) {
                piouff += 1;
            } else {
                hash.remove(&r.p);
                r.execute_instruction();
                check_map(&r, &world)?;
                check_collisions(&r, &hash)?;
                hash.insert(robot::Position { x: r.p.x, y: r.p.y }, r.id);
            }
        }
        if piouff == robot_pool.len() as u32 {
            break;
        }
    }
    println!("Final state");
    println!("============");
    display_grid(&world, &robot_pool, &hash);
    for r in &robot_pool {
        println!("Robot id: {}: Final position: ({}, {})", r.id, r.p.x, r.p.y);
    }

    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());
    }
}