use std::process;

use yansi::Paint as _;

// ── Help ───────────────────────────────────────────────────────────────────────

pub fn print_help() {
    println!(
        "{} {} — the Flux language compiler\n",
        "fluxc".bold(),
        env!("CARGO_PKG_VERSION").dim(),
    );
    println!("{}", "USAGE:".bold().yellow());
    println!("  fluxc [OPTIONS] <file> [<file> ...]\n");
    println!("{}", "OPTIONS:".bold().yellow());
    println!(
        "  {}, {}    Print this help message",
        "-h".bold(),
        "--help".bold(),
    );
    println!(
        "  {}, {}  Print version information",
        "-V".bold(),
        "--version".bold(),
    );
    println!(
        "  {}              Compile to object file (no `main` required, no linking)",
        "-c".bold(),
    );
    println!(
        "  {}              Emit LLVM IR and stop (implies `-c`)",
        "-S".bold(),
    );
    println!(
        "  {} {}      Write output to <file>",
        "-o".bold(),
        "<file>".bold(),
    );
    println!();
    println!("{}", "ARGS:".bold().yellow());
    println!(
        "  {}    One or more Flux source files to compile",
        "<file>".bold(),
    );
}

pub fn print_version() {
    println!("fluxc {}", env!("CARGO_PKG_VERSION"));
}

// ── Error helpers ─────────────────────────────────────────────────────────────

pub fn fatal(msg: &str) -> ! {
    eprintln!("{}: {}", "error".bold().red(), msg.bold());
    eprintln!("  {} fluxc --help", "hint:".bold().cyan());
    process::exit(1);
}

pub fn io_error(path: &str, err: std::io::Error) -> ! {
    eprintln!(
        "{}: cannot read {}: {}",
        "error".bold().red(),
        path.bold(),
        err,
    );
    process::exit(1);
}

// ── Argument parsing ──────────────────────────────────────────────────────────

pub struct Opts {
    pub files: Vec<String>,
    /// `-c`: compile to object file without requiring a `main` entry point.
    pub no_main: bool,
    /// `-S`: emit LLVM IR text and stop (implies `-c`).
    pub emit_ir: bool,
    /// `-o <file>`: write final output to this path.
    pub output: Option<String>,
}

pub fn parse_args() -> Opts {
    let mut files = Vec::new();
    let mut no_main = false;
    let mut emit_ir = false;
    let mut output: Option<String> = None;
    let mut args = std::env::args().skip(1).peekable();

    while let Some(arg) = args.next() {
        match arg.as_str() {
            "-h" | "--help" => {
                print_help();
                process::exit(0);
            }
            "-V" | "--version" => {
                print_version();
                process::exit(0);
            }
            "-c" => no_main = true,
            "-S" => { emit_ir = true; no_main = true; }
            "-o" => match args.next() {
                Some(path) => output = Some(path),
                None => fatal("option `-o` requires an argument"),
            },
            flag if flag.starts_with('-') => {
                fatal(&format!("unknown option `{flag}`"));
            }
            path => files.push(path.to_owned()),
        }
    }

    if files.is_empty() {
        fatal("no input files — at least one source file is required");
    }

    Opts { files, no_main, emit_ir, output }
}