// This file is part of the uutils coreutils package.
//
// For the full copyright and license information, please view the LICENSE
// file that was distributed with this source code.

use clap::{Arg, ArgAction, Command};
use std::env;
use uucore::{error::UResult, format_usage, help_about, help_usage};

const ABOUT: &str = help_about!("printenv.md");
const USAGE: &str = help_usage!("printenv.md");

static OPT_NULL: &str = "null";

static ARG_VARIABLES: &str = "variables";

#[uucore::main]
pub fn uumain(args: impl uucore::Args) -> UResult<()> {
    let matches = uu_app().get_matches_from(args);

    let variables: Vec<String> = matches
        .get_many::<String>(ARG_VARIABLES)
        .map(|v| v.map(ToString::to_string).collect())
        .unwrap_or_default();

    let separator = if matches.get_flag(OPT_NULL) {
        "\x00"
    } else {
        "\n"
    };

    if variables.is_empty() {
        for (env_var, value) in env::vars() {
            print!("{env_var}={value}{separator}");
        }
        return Ok(());
    }

    let mut error_found = false;
    for env_var in variables {
        // we silently ignore a=b as variable but we trigger an error
        if env_var.contains('=') {
            error_found = true;
            continue;
        }
        if let Ok(var) = env::var(env_var) {
            print!("{var}{separator}");
        } else {
            error_found = true;
        }
    }

    if error_found { Err(1.into()) } else { Ok(()) }
}

pub fn uu_app() -> Command {
    Command::new(uucore::util_name())
        .version(uucore::crate_version!())
        .about(ABOUT)
        .override_usage(format_usage(USAGE))
        .infer_long_args(true)
        .arg(
            Arg::new(OPT_NULL)
                .short('0')
                .long(OPT_NULL)
                .help("end each output line with 0 byte rather than newline")
                .action(ArgAction::SetTrue),
        )
        .arg(
            Arg::new(ARG_VARIABLES)
                .action(ArgAction::Append)
                .num_args(1..),
        )
}
