//! Copyright (C) 2022, Dmitriy Pleshevskiy <dmitriy@ideascup.me>
//!
//! vnetod is free software: you can redistribute it and/or modify
//! it under the terms of the GNU General Public License as published by
//! the Free Software Foundation, either version 3 of the License, or
//! (at your option) any later version.
//!
//! vnetod is distributed in the hope that it will be useful,
//! but WITHOUT ANY WARRANTY; without even the implied warranty of
//! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//! GNU General Public License for more details.
//!
//! You should have received a copy of the GNU General Public License
//! along with vnetod.  If not, see <https://www.gnu.org/licenses/>.
//!

use std::{
    fs::File,
    io::{BufWriter, Write},
};

fn main() -> Result<(), Error> {
    match std::env::args().nth(1) {
        Some(name) => change_env_layout(&name)?,
        _ => print_help(),
    };
    Ok(())
}

fn change_env_layout(name: &str) -> Result<(), Error> {
    let content = std::fs::read_to_string(".env").map_err(|_| Error::OpenFile)?;

    let mut writer = File::create(".env")
        .map_err(|_| Error::OpenFile)
        .map(BufWriter::new)?;

    let mut current_section_name: Option<String> = None;

    for line in content.split_inclusive('\n') {
        let new_line = if is_section_end(line) {
            current_section_name = None;
            line.to_string()
        } else if let Some(section_info) = line.strip_prefix("### ") {
            current_section_name = section_info.split_whitespace().next().map(String::from);
            line.to_string()
        } else if let Some(cur_name) = current_section_name.clone() {
            if cur_name == name {
                String::from(line.trim_start_matches(['#', ' ']))
            } else {
                format!("# {}", line.trim_start_matches(['#', ' ']))
            }
        } else {
            line.to_string()
        };

        writer
            .write_all(new_line.as_bytes())
            .map_err(|_| Error::WriteData)?;
    }

    writer.flush().map_err(|_| Error::WriteData)
}

fn is_section_end(line: &str) -> bool {
    line.trim().is_empty()
}

fn print_help() {
    eprintln!(
        "\
USAGE
vnetod [STATE_NAME] - switch environment variable state by name

---
    vnetod  Copyright (C) 2022  Dmitriy Pleshevskiy <dmitriy@ideascup.me>
    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
    This is free software, and you are welcome to redistribute it
    under certain conditions; type `show c' for details.
"
    )
}

#[derive(Debug)]
enum Error {
    OpenFile,
    WriteData,
}