use anyhow::{bail, Context, Result};
use crossterm::style::Stylize;
use std::{
    env::set_current_dir,
    fs::{self, create_dir},
    io::ErrorKind,
    path::Path,
    process::{Command, Stdio},
};

use crate::{cargo_toml::updated_cargo_toml, embedded::EMBEDDED_FILES, info_file::InfoFile};

pub fn init() -> Result<()> {
    if Path::new("exercises").is_dir() && Path::new("Cargo.toml").is_file() {
        bail!(PROBABLY_IN_RUSTLINGS_DIR_ERR);
    }

    let rustlings_path = Path::new("rustlings");
    if let Err(e) = create_dir(rustlings_path) {
        if e.kind() == ErrorKind::AlreadyExists {
            bail!(RUSTLINGS_DIR_ALREADY_EXISTS_ERR);
        }
        return Err(e.into());
    }

    set_current_dir("rustlings")
        .context("Failed to change the current directory to `rustlings`")?;

    let info_file = InfoFile::parse()?;
    EMBEDDED_FILES
        .init_exercises_dir(&info_file.exercises)
        .context("Failed to initialize the `rustlings/exercises` directory")?;

    let current_cargo_toml = include_str!("../dev/Cargo.toml");
    // Skip the first line (comment).
    let newline_ind = current_cargo_toml
        .as_bytes()
        .iter()
        .position(|c| *c == b'\n')
        .context("The embedded `Cargo.toml` is empty or contains only one line.")?;
    let current_cargo_toml =
        &current_cargo_toml[(newline_ind + 1).min(current_cargo_toml.len() - 1)..];
    let updated_cargo_toml = updated_cargo_toml(&info_file.exercises, current_cargo_toml, b"")
        .context("Failed to generate `Cargo.toml`")?;
    fs::write("Cargo.toml", updated_cargo_toml)
        .context("Failed to create the file `rustlings/Cargo.toml`")?;

    fs::write(".gitignore", GITIGNORE)
        .context("Failed to create the file `rustlings/.gitignore`")?;

    create_dir(".vscode").context("Failed to create the directory `rustlings/.vscode`")?;
    fs::write(".vscode/extensions.json", VS_CODE_EXTENSIONS_JSON)
        .context("Failed to create the file `rustlings/.vscode/extensions.json`")?;

    // Ignore any Git error because Git initialization is not required.
    let _ = Command::new("git")
        .arg("init")
        .stdin(Stdio::null())
        .stderr(Stdio::null())
        .status();

    println!(
        "\n{}\n\n{}",
        "Initialization done ✓".green(),
        POST_INIT_MSG.bold(),
    );

    Ok(())
}

const GITIGNORE: &[u8] = b".rustlings-state.txt
Cargo.lock
target
.vscode
";

pub const VS_CODE_EXTENSIONS_JSON: &[u8] = br#"{"recommendations":["rust-lang.rust-analyzer"]}"#;

const PROBABLY_IN_RUSTLINGS_DIR_ERR: &str =
    "A directory with the name `exercises` and a file with the name `Cargo.toml` already exist
in the current directory. It looks like Rustlings was already initialized here.
Run `rustlings` for instructions on getting started with the exercises.

If you didn't already initialize Rustlings, please initialize it in another directory.";

const RUSTLINGS_DIR_ALREADY_EXISTS_ERR: &str =
    "A directory with the name `rustlings` already exists in the current directory.
You probably already initialized Rustlings.
Run `cd rustlings`
Then run `rustlings` again";

const POST_INIT_MSG: &str = "Run `cd rustlings` to go into the generated directory.
Then run `rustlings` to get started.";