use crate::exercise::{Exercise, ExerciseList};
use crate::run::run;
use crate::verify::verify;
use argh::FromArgs;
use console::Emoji;
use notify::DebouncedEvent;
use notify::{RecommendedWatcher, RecursiveMode, Watcher};
use std::ffi::OsStr;
use std::fs;
use std::io::{self, prelude::*};
use std::path::Path;
use std::process::{Command, Stdio};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::mpsc::{RecvTimeoutError, channel};
use std::sync::{Arc, Mutex};
use std::thread;
use std::time::Duration;

#[macro_use]
mod ui;

mod exercise;
mod run;
mod verify;

// In sync with crate version
const VERSION: &str = "4.5.0";

#[derive(FromArgs, PartialEq, Debug)]
/// Rustlings is a collection of small exercises to get you used to writing and reading Rust code
struct Args {
    /// show outputs from the test exercises
    #[argh(switch)]
    nocapture: bool,
    /// show the executable version
    #[argh(switch, short = 'v')]
    version: bool,
    #[argh(subcommand)]
    nested: Option<Subcommands>,
}

#[derive(FromArgs, PartialEq, Debug)]
#[argh(subcommand)]
enum Subcommands {
    Verify(VerifyArgs),
    Watch(WatchArgs),
    Run(RunArgs),
    Hint(HintArgs),
    List(ListArgs),
}

#[derive(FromArgs, PartialEq, Debug)]
#[argh(subcommand, name = "verify")]
/// Verifies all exercises according to the recommended order
struct VerifyArgs {}

#[derive(FromArgs, PartialEq, Debug)]
#[argh(subcommand, name = "watch")]
/// Reruns `verify` when files were edited
struct WatchArgs {}

#[derive(FromArgs, PartialEq, Debug)]
#[argh(subcommand, name = "run")]
/// Runs/Tests a single exercise
struct RunArgs {
    #[argh(positional)]
    /// the name of the exercise
    name: String,
}

#[derive(FromArgs, PartialEq, Debug)]
#[argh(subcommand, name = "hint")]
/// Returns a hint for the given exercise
struct HintArgs {
    #[argh(positional)]
    /// the name of the exercise
    name: String,
}

#[derive(FromArgs, PartialEq, Debug)]
#[argh(subcommand, name = "list")]
/// Lists the exercises available in Rustlings
struct ListArgs {
    #[argh(switch, short = 'p')]
    /// show only the paths of the exercises
    paths: bool,
    #[argh(switch, short = 'n')]
    /// show only the names of the exercises
    names: bool,
    #[argh(option, short = 'f')]
    /// provide a string to match exercise names
    /// comma separated patterns are acceptable
    filter: Option<String>,
    #[argh(switch, short = 'u')]
    /// display only exercises not yet solved
    unsolved: bool,
    #[argh(switch, short = 's')]
    /// display only exercises that have been solved
    solved: bool,
}

fn main() {
    let args: Args = argh::from_env();

    if args.version {
        println!("v{}", VERSION);
        std::process::exit(0);
    }

    if args.nested.is_none() {
        println!();
        println!(r#"       welcome to...                      "#);
        println!(r#"                 _   _ _                  "#);
        println!(r#"  _ __ _   _ ___| |_| (_)_ __   __ _ ___  "#);
        println!(r#" | '__| | | / __| __| | | '_ \ / _` / __| "#);
        println!(r#" | |  | |_| \__ \ |_| | | | | | (_| \__ \ "#);
        println!(r#" |_|   \__,_|___/\__|_|_|_| |_|\__, |___/ "#);
        println!(r#"                               |___/      "#);
        println!();
    }

    if !Path::new("info.toml").exists() {
        println!(
            "{} must be run from the rustlings directory",
            std::env::current_exe().unwrap().to_str().unwrap()
        );
        println!("Try `cd rustlings/`!");
        std::process::exit(1);
    }

    if !rustc_exists() {
        println!("We cannot find `rustc`.");
        println!("Try running `rustc --version` to diagnose your problem.");
        println!("For instructions on how to install Rust, check the README.");
        std::process::exit(1);
    }

    let toml_str = &fs::read_to_string("info.toml").unwrap();
    let exercises = toml::from_str::<ExerciseList>(toml_str).unwrap().exercises;
    let verbose = args.nocapture;

    let command = args.nested.unwrap_or_else(|| {
        let text = fs::read_to_string("default_out.txt").unwrap();
        println!("{}", text);
        std::process::exit(0);
    });
    match command {
        Subcommands::List(subargs) => {
            if !subargs.paths && !subargs.names {
                println!("{:<17}\t{:<46}\t{:<7}", "Name", "Path", "Status");
            }
            let mut exercises_done: u16 = 0;
            let filters = subargs.filter.clone().unwrap_or_default().to_lowercase();
            exercises.iter().for_each(|e| {
                let fname = format!("{}", e.path.display());
                let filter_cond = filters
                    .split(',')
                    .filter(|f| !f.trim().is_empty())
                    .any(|f| e.name.contains(&f) || fname.contains(&f));
                let status = if e.looks_done() {
                    exercises_done += 1;
                    "Done"
                } else {
                    "Pending"
                };
                let solve_cond = {
                    (e.looks_done() && subargs.solved)
                        || (!e.looks_done() && subargs.unsolved)
                        || (!subargs.solved && !subargs.unsolved)
                };
                if solve_cond && (filter_cond || subargs.filter.is_none()) {
                    let line = if subargs.paths {
                        format!("{}\n", fname)
                    } else if subargs.names {
                        format!("{}\n", e.name)
                    } else {
                        format!("{:<17}\t{:<46}\t{:<7}\n", e.name, fname, status)
                    };
                    // Somehow using println! leads to the binary panicking
                    // when its output is piped.
                    // So, we're handling a Broken Pipe error and exiting with 0 anyway
                    let stdout = std::io::stdout();
                    {
                        let mut handle = stdout.lock();
                        handle.write_all(line.as_bytes()).unwrap_or_else(|e| {
                            match e.kind() {
                                std::io::ErrorKind::BrokenPipe => std::process::exit(0),
                                _ => std::process::exit(1),
                            };
                        });
                    }
                }
            });
            let percentage_progress = exercises_done as f32 / exercises.len() as f32 * 100.0;
            println!(
                "Progress: You completed {} / {} exercises ({:.2} %).",
                exercises_done,
                exercises.len(),
                percentage_progress
            );
            std::process::exit(0);
        }

        Subcommands::Run(subargs) => {
            let exercise = find_exercise(&subargs.name, &exercises);

            run(exercise, verbose).unwrap_or_else(|_| std::process::exit(1));
        }

        Subcommands::Hint(subargs) => {
            let exercise = find_exercise(&subargs.name, &exercises);

            println!("{}", exercise.hint);
        }

        Subcommands::Verify(_subargs) => {
            verify(&exercises, verbose).unwrap_or_else(|_| std::process::exit(1));
        }

        Subcommands::Watch(_subargs) => {
            match watch(&exercises, verbose) {
                Err(e) => {
                    println!(
                        "Error: Could not watch your progress. Error message was {:?}.",
                        e
                    );
                    println!("Most likely you've run out of disk space or your 'inotify limit' has been reached.");
                    std::process::exit(1);
                }
                Ok(WatchStatus::Finished) => {
                    println!(
                        "{emoji} All exercises completed! {emoji}",
                        emoji = Emoji("🎉", "★")
                    );
                    println!();
                    println!("+----------------------------------------------------+");
                    println!("|          You made it to the Fe-nish line!          |");
                    println!("+--------------------------  ------------------------+");
                    println!("                          \\/                         ");
                    println!("     ▒▒          ▒▒▒▒▒▒▒▒      ▒▒▒▒▒▒▒▒          ▒▒   ");
                    println!("   ▒▒▒▒  ▒▒    ▒▒        ▒▒  ▒▒        ▒▒    ▒▒  ▒▒▒▒ ");
                    println!("   ▒▒▒▒  ▒▒  ▒▒            ▒▒            ▒▒  ▒▒  ▒▒▒▒ ");
                    println!(" ░░▒▒▒▒░░▒▒  ▒▒            ▒▒            ▒▒  ▒▒░░▒▒▒▒ ");
                    println!("   ▓▓▓▓▓▓▓▓  ▓▓      ▓▓██  ▓▓  ▓▓██      ▓▓  ▓▓▓▓▓▓▓▓ ");
                    println!("     ▒▒▒▒    ▒▒      ████  ▒▒  ████      ▒▒░░  ▒▒▒▒   ");
                    println!("       ▒▒  ▒▒▒▒▒▒        ▒▒▒▒▒▒        ▒▒▒▒▒▒  ▒▒     ");
                    println!("         ▒▒▒▒▒▒▒▒▒▒▓▓▓▓▓▓▒▒▒▒▒▒▒▒▓▓▒▒▓▓▒▒▒▒▒▒▒▒       ");
                    println!("           ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒         ");
                    println!("             ▒▒▒▒▒▒▒▒▒▒██▒▒▒▒▒▒██▒▒▒▒▒▒▒▒▒▒           ");
                    println!("           ▒▒  ▒▒▒▒▒▒▒▒▒▒██████▒▒▒▒▒▒▒▒▒▒  ▒▒         ");
                    println!("         ▒▒    ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒    ▒▒       ");
                    println!("       ▒▒    ▒▒    ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒    ▒▒    ▒▒     ");
                    println!("       ▒▒  ▒▒    ▒▒                  ▒▒    ▒▒  ▒▒     ");
                    println!("           ▒▒  ▒▒                      ▒▒  ▒▒         ");
                    println!();
                    println!("We hope you enjoyed learning about the various aspects of Rust!");
                    println!(
                        "If you noticed any issues, please don't hesitate to report them to our repo."
                    );
                    println!("You can also contribute your own exercises to help the greater community!");
                    println!();
                    println!("Before reporting an issue or contributing, please read our guidelines:");
                    println!("https://github.com/rust-lang/rustlings/blob/main/CONTRIBUTING.md");
                }
                Ok(WatchStatus::Unfinished) => {
                    println!("We hope you're enjoying learning about Rust!");
                    println!("If you want to continue working on the exercises at a later point, you can simply run `rustlings watch` again");
                }
            }
        }
    }
}

fn spawn_watch_shell(failed_exercise_hint: &Arc<Mutex<Option<String>>>, should_quit: Arc<AtomicBool>) {
    let failed_exercise_hint = Arc::clone(failed_exercise_hint);
    println!("Welcome to watch mode! You can type 'help' to get an overview of the commands you can use here.");
    thread::spawn(move || loop {
        let mut input = String::new();
        match io::stdin().read_line(&mut input) {
            Ok(_) => {
                let input = input.trim();
                if input == "hint" {
                    if let Some(hint) = &*failed_exercise_hint.lock().unwrap() {
                        println!("{}", hint);
                    }
                } else if input == "clear" {
                    println!("\x1B[2J\x1B[1;1H");
                } else if input.eq("quit") {
                    should_quit.store(true, Ordering::SeqCst);
                    println!("Bye!");
                } else if input.eq("help") {
                    println!("Commands available to you in watch mode:");
                    println!("  hint  - prints the current exercise's hint");
                    println!("  clear - clears the screen");
                    println!("  quit  - quits watch mode");
                    println!("  help  - displays this help message");
                    println!();
                    println!("Watch mode automatically re-evaluates the current exercise");
                    println!("when you edit a file's contents.")
                } else {
                    println!("unknown command: {}", input);
                }
            }
            Err(error) => println!("error reading command: {}", error),
        }
    });
}

fn find_exercise<'a>(name: &str, exercises: &'a [Exercise]) -> &'a Exercise {
    if name.eq("next") {
        exercises
            .iter()
            .find(|e| !e.looks_done())
            .unwrap_or_else(|| {
                println!("🎉 Congratulations! You have done all the exercises!");
                println!("🔚 There are no more exercises to do next!");
                std::process::exit(1)
            })
    } else {
        exercises
            .iter()
            .find(|e| e.name == name)
            .unwrap_or_else(|| {
                println!("No exercise found for '{}'!", name);
                std::process::exit(1)
            })
    }
}

enum WatchStatus {
    Finished,
    Unfinished,
}

fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<WatchStatus> {
    /* Clears the terminal with an ANSI escape code.
    Works in UNIX and newer Windows terminals. */
    fn clear_screen() {
        println!("\x1Bc");
    }

    let (tx, rx) = channel();
    let should_quit = Arc::new(AtomicBool::new(false));

    let mut watcher: RecommendedWatcher = Watcher::new(tx, Duration::from_secs(2))?;
    watcher.watch(Path::new("./exercises"), RecursiveMode::Recursive)?;

    clear_screen();

    let to_owned_hint = |t: &Exercise| t.hint.to_owned();
    let failed_exercise_hint = match verify(exercises.iter(), verbose) {
        Ok(_) => return Ok(WatchStatus::Finished),
        Err(exercise) => Arc::new(Mutex::new(Some(to_owned_hint(exercise)))),
    };
    spawn_watch_shell(&failed_exercise_hint, Arc::clone(&should_quit));
    loop {
        match rx.recv_timeout(Duration::from_secs(1)) {
            Ok(event) => match event {
                DebouncedEvent::Create(b) | DebouncedEvent::Chmod(b) | DebouncedEvent::Write(b) => {
                    if b.extension() == Some(OsStr::new("rs")) && b.exists() {
                        let filepath = b.as_path().canonicalize().unwrap();
                        let pending_exercises = exercises
                            .iter()
                            .skip_while(|e| !filepath.ends_with(&e.path))
                            // .filter(|e| filepath.ends_with(&e.path))
                            .chain(
                                exercises
                                    .iter()
                                    .filter(|e| !e.looks_done() && !filepath.ends_with(&e.path)),
                            );
                        clear_screen();
                        match verify(pending_exercises, verbose) {
                            Ok(_) => return Ok(WatchStatus::Finished),
                            Err(exercise) => {
                                let mut failed_exercise_hint = failed_exercise_hint.lock().unwrap();
                                *failed_exercise_hint = Some(to_owned_hint(exercise));
                            }
                        }
                    }
                }
                _ => {}
            },
            Err(RecvTimeoutError::Timeout) => {
                // the timeout expired, just check the `should_quit` variable below then loop again
            }
            Err(e) => println!("watch error: {:?}", e),
        }
        // Check if we need to exit
        if should_quit.load(Ordering::SeqCst) {
            return Ok(WatchStatus::Unfinished);
        }
    }
}

fn rustc_exists() -> bool {
    Command::new("rustc")
        .args(&["--version"])
        .stdout(Stdio::null())
        .spawn()
        .and_then(|mut child| child.wait())
        .map(|status| status.success())
        .unwrap_or(false)
}