use anyhow::{Context, Result};
use clap::{Parser, Subcommand};
use crossterm::{
    terminal::{Clear, ClearType},
    ExecutableCommand,
};
use std::{
    io::{self, BufRead, Write},
    path::Path,
    process::exit,
};

mod app_state;
mod embedded;
mod exercise;
mod info_file;
mod init;
mod list;
mod progress_bar;
mod run;
mod trust;
mod watch;

use self::{
    app_state::{AppState, StateFileStatus},
    info_file::InfoFile,
    init::init,
    list::list,
    run::run,
    trust::{current_dir_is_trusted, trust_current_dir},
    watch::{watch, WatchExit},
};

/// Rustlings is a collection of small exercises to get you used to writing and reading Rust code
#[derive(Parser)]
#[command(version)]
struct Args {
    #[command(subcommand)]
    command: Option<Subcommands>,
    /// Manually run the current exercise using `r` or `run` in the watch mode.
    /// Only use this if Rustlings fails to detect exercise file changes.
    #[arg(long)]
    manual_run: bool,
}

#[derive(Subcommand)]
enum Subcommands {
    /// Initialize Rustlings
    Init,
    /// Run a single exercise. Runs the next pending exercise if the exercise name is not specified.
    Run {
        /// The name of the exercise
        name: Option<String>,
    },
    /// Reset a single exercise
    Reset {
        /// The name of the exercise
        name: String,
    },
    /// Return a hint for the given exercise
    Hint {
        /// The name of the exercise
        name: String,
    },
    /// Trust the current directory with its exercises.
    ///
    /// You only need to run this if you want to work on third-party exercises or after you moved
    /// the official exercises that were initialized with `rustlings init`.
    Trust,
}

fn main() -> Result<()> {
    let args = Args::parse();

    which::which("cargo").context(CARGO_NOT_FOUND_ERR)?;

    let info_file = InfoFile::parse()?;

    if matches!(args.command, Some(Subcommands::Init)) {
        init(&info_file.exercises).context("Initialization failed")?;
        println!("{POST_INIT_MSG}");
        return Ok(());
    }

    if !Path::new("exercises").is_dir() {
        println!("{PRE_INIT_MSG}");
        exit(1);
    }

    if matches!(args.command, Some(Subcommands::Trust)) {
        trust_current_dir()?;
        println!("{POST_TRUST_MSG}");
        return Ok(());
    }

    if !current_dir_is_trusted()? {
        println!("{NOT_TRUSTED_MSG}");
        exit(1);
    }

    let (mut app_state, state_file_status) = AppState::new(
        info_file.exercises,
        info_file.final_message.unwrap_or_default(),
    );

    if let Some(welcome_message) = info_file.welcome_message {
        match state_file_status {
            StateFileStatus::NotRead => {
                let mut stdout = io::stdout().lock();
                stdout.execute(Clear(ClearType::All))?;

                let welcome_message = welcome_message.trim();
                write!(stdout, "{welcome_message}\n\nPress ENTER to continue ")?;
                stdout.flush()?;

                io::stdin().lock().read_until(b'\n', &mut Vec::new())?;

                stdout.execute(Clear(ClearType::All))?;
            }
            StateFileStatus::Read => (),
        }
    }

    match args.command {
        None => {
            let notify_exercise_paths: Option<&'static [&'static str]> = if args.manual_run {
                None
            } else {
                // For the the notify event handler thread.
                // Leaking is not a problem because the slice lives until the end of the program.
                Some(
                    app_state
                        .exercises()
                        .iter()
                        .map(|exercise| exercise.path)
                        .collect::<Vec<_>>()
                        .leak(),
                )
            };

            loop {
                match watch(&mut app_state, notify_exercise_paths)? {
                    WatchExit::Shutdown => break,
                    // It is much easier to exit the watch mode, launch the list mode and then restart
                    // the watch mode instead of trying to pause the watch threads and correct the
                    // watch state.
                    WatchExit::List => list(&mut app_state)?,
                }
            }
        }
        Some(Subcommands::Run { name }) => {
            if let Some(name) = name {
                app_state.set_current_exercise_by_name(&name)?;
            }
            run(&mut app_state)?;
        }
        Some(Subcommands::Reset { name }) => {
            app_state.set_current_exercise_by_name(&name)?;
            let exercise = app_state.current_exercise();
            exercise.reset()?;
            println!("The exercise {exercise} has been reset!");
            app_state.set_pending(app_state.current_exercise_ind())?;
        }
        Some(Subcommands::Hint { name }) => {
            app_state.set_current_exercise_by_name(&name)?;
            println!("{}", app_state.current_exercise().hint);
        }
        // `Init` and `Trust` are handled above.
        Some(Subcommands::Init | Subcommands::Trust) => (),
    }

    Ok(())
}

const CARGO_NOT_FOUND_ERR: &str = "Failed to find `cargo`.
Did you already install Rust?
Try running `cargo --version` to diagnose the problem.";

const POST_INIT_MSG: &str = "Done initialization!

Run `cd rustlings` to go into the generated directory.
Then run `rustlings` to get started.";

const PRE_INIT_MSG: &str = r"
       Welcome to...
                 _   _ _
  _ __ _   _ ___| |_| (_)_ __   __ _ ___
 | '__| | | / __| __| | | '_ \ / _` / __|
 | |  | |_| \__ \ |_| | | | | | (_| \__ \
 |_|   \__,_|___/\__|_|_|_| |_|\__, |___/
                               |___/

The `exercises` directory wasn't found in the current directory.
If you are just starting with Rustlings, run the command `rustlings init` to initialize it.";

const POST_TRUST_MSG: &str = "You now trust the exercises in the current directory.
Run `rustlings` to start working on them.";

const NOT_TRUSTED_MSG: &str = "It looks like you are trying to work on third-party exercises.
Rustlings supports third-party exercises. But because Rustlings runs the code inside an exercise,
we need to warn you about the possibility of malicious code.
We recommend that you read all the exercise files in the `exercises` directory and check the
dependencies in the `Cargo.toml` file.
If everything looks fine and you want to trust this directory, run `rustlings trust`.

If you you are trying to work on the official exercises that were generated using `rustlings init`,
then you probably moved the directory containing them. In that case, you can run `rustlings trust`
without a problem.";

const FENISH_LINE: &str = "+----------------------------------------------------+
|          You made it to the Fe-nish line!          |
+--------------------------  ------------------------+
                           \\/\x1b[31m
     ▒▒          ▒▒▒▒▒▒▒▒      ▒▒▒▒▒▒▒▒          ▒▒
   ▒▒▒▒  ▒▒    ▒▒        ▒▒  ▒▒        ▒▒    ▒▒  ▒▒▒▒
   ▒▒▒▒  ▒▒  ▒▒            ▒▒            ▒▒  ▒▒  ▒▒▒▒
 ░░▒▒▒▒░░▒▒  ▒▒            ▒▒            ▒▒  ▒▒░░▒▒▒▒
   ▓▓▓▓▓▓▓▓  ▓▓      ▓▓██  ▓▓  ▓▓██      ▓▓  ▓▓▓▓▓▓▓▓
     ▒▒▒▒    ▒▒      ████  ▒▒  ████      ▒▒░░  ▒▒▒▒
       ▒▒  ▒▒▒▒▒▒        ▒▒▒▒▒▒        ▒▒▒▒▒▒  ▒▒
         ▒▒▒▒▒▒▒▒▒▒▓▓▓▓▓▓▒▒▒▒▒▒▒▒▓▓▓▓▓▓▒▒▒▒▒▒▒▒
           ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒
             ▒▒▒▒▒▒▒▒▒▒██▒▒▒▒▒▒██▒▒▒▒▒▒▒▒▒▒
           ▒▒  ▒▒▒▒▒▒▒▒▒▒██████▒▒▒▒▒▒▒▒▒▒  ▒▒
         ▒▒    ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒    ▒▒
       ▒▒    ▒▒    ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒    ▒▒    ▒▒
       ▒▒  ▒▒    ▒▒                  ▒▒    ▒▒  ▒▒
           ▒▒  ▒▒                      ▒▒  ▒▒\x1b[0m

";