use crate::consts::WELCOME;
use crate::embedded::{WriteStrategy, EMBEDDED_FILES};
use crate::exercise::{Exercise, ExerciseList};
use crate::run::run;
use crate::verify::verify;
use anyhow::{bail, Context, Result};
use clap::{Parser, Subcommand};
use state::State;
use std::io::Write;
use std::path::Path;
use std::process::exit;
use verify::VerifyState;

mod consts;
mod embedded;
mod exercise;
mod init;
mod run;
mod state;
mod verify;
mod watch;

/// 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>,
}

#[derive(Subcommand)]
enum Subcommands {
    /// Initialize Rustlings
    Init,
    /// Verify all exercises according to the recommended order
    Verify,
    /// Same as just running `rustlings` without a subcommand.
    Watch,
    /// Run/Test a single exercise
    Run {
        /// The name of the exercise
        name: 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,
    },
    /// List the exercises available in Rustlings
    List {
        /// Show only the paths of the exercises
        #[arg(short, long)]
        paths: bool,
        /// Show only the names of the exercises
        #[arg(short, long)]
        names: bool,
        /// Provide a string to match exercise names.
        /// Comma separated patterns are accepted
        #[arg(short, long)]
        filter: Option<String>,
        /// Display only exercises not yet solved
        #[arg(short, long)]
        unsolved: bool,
        /// Display only exercises that have been solved
        #[arg(short, long)]
        solved: bool,
    },
}

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

    which::which("cargo").context(
        "Failed to find `cargo`.
Did you already install Rust?
Try running `cargo --version` to diagnose the problem.",
    )?;

    let exercises = ExerciseList::parse()?.exercises;

    if matches!(args.command, Some(Subcommands::Init)) {
        init::init_rustlings(&exercises).context("Initialization failed")?;
        println!(
            "\nDone initialization!\n
Run `cd rustlings` to go into the generated directory.
Then run `rustlings` for further instructions on getting started."
        );
        return Ok(());
    } else if !Path::new("exercises").is_dir() {
        println!(
            "
{WELCOME}

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."
        );
        exit(1);
    }

    let state = State::read_or_default(&exercises);

    match args.command {
        None | Some(Subcommands::Watch) => {
            watch::watch(&state, &exercises)?;
        }
        // `Init` is handled above.
        Some(Subcommands::Init) => (),
        Some(Subcommands::List {
            paths,
            names,
            filter,
            unsolved,
            solved,
        }) => {
            if !paths && !names {
                println!("{:<17}\t{:<46}\t{:<7}", "Name", "Path", "Status");
            }
            let mut exercises_done: u16 = 0;
            let lowercase_filter = filter
                .as_ref()
                .map(|s| s.to_lowercase())
                .unwrap_or_default();
            let filters = lowercase_filter
                .split(',')
                .filter_map(|f| {
                    let f = f.trim();
                    if f.is_empty() {
                        None
                    } else {
                        Some(f)
                    }
                })
                .collect::<Vec<_>>();

            for exercise in &exercises {
                let fname = exercise.path.to_string_lossy();
                let filter_cond = filters
                    .iter()
                    .any(|f| exercise.name.contains(f) || fname.contains(f));
                let looks_done = exercise.looks_done()?;
                let status = if looks_done {
                    exercises_done += 1;
                    "Done"
                } else {
                    "Pending"
                };
                let solve_cond =
                    (looks_done && solved) || (!looks_done && unsolved) || (!solved && !unsolved);
                if solve_cond && (filter_cond || filter.is_none()) {
                    let line = if paths {
                        format!("{fname}\n")
                    } else if names {
                        format!("{}\n", exercise.name)
                    } else {
                        format!("{:<17}\t{fname:<46}\t{status:<7}\n", exercise.name)
                    };
                    // 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 => exit(0),
                                _ => exit(1),
                            };
                        });
                    }
                }
            }

            let percentage_progress = exercises_done as f32 / exercises.len() as f32 * 100.0;
            println!(
                "Progress: You completed {} / {} exercises ({:.1} %).",
                exercises_done,
                exercises.len(),
                percentage_progress
            );
            exit(0);
        }
        Some(Subcommands::Run { name }) => {
            let exercise = find_exercise(&name, &exercises)?;
            run(exercise).unwrap_or_else(|_| exit(1));
        }
        Some(Subcommands::Reset { name }) => {
            let exercise = find_exercise(&name, &exercises)?;
            EMBEDDED_FILES
                .write_exercise_to_disk(&exercise.path, WriteStrategy::Overwrite)
                .with_context(|| format!("Failed to reset the exercise {exercise}"))?;
            println!("The file {} has been reset!", exercise.path.display());
        }
        Some(Subcommands::Hint { name }) => {
            let exercise = find_exercise(&name, &exercises)?;
            println!("{}", exercise.hint);
        }
        Some(Subcommands::Verify) => match verify(&exercises, 0)? {
            VerifyState::AllExercisesDone => println!("All exercises done!"),
            VerifyState::Failed(exercise) => bail!("Exercise {exercise} failed"),
        },
    }

    Ok(())
}

fn find_exercise<'a>(name: &str, exercises: &'a [Exercise]) -> Result<&'a Exercise> {
    if name == "next" {
        for exercise in exercises {
            if !exercise.looks_done()? {
                return Ok(exercise);
            }
        }

        println!("🎉 Congratulations! You have done all the exercises!");
        println!("🔚 There are no more exercises to do next!");
        exit(0);
    }

    exercises
        .iter()
        .find(|e| e.name == name)
        .with_context(|| format!("No exercise found for '{name}'!"))
}