use super::Cmd;
use clap::{Arg, ArgAction, Command};
use std::{
    fs::File,
    io::{self, BufRead, BufReader, ErrorKind, Write},
};
use termcolor::{Color, ColorChoice, ColorSpec, StandardStream, WriteColor};

#[derive(Debug, Default)]
pub struct Rev;

impl Cmd for Rev {
    fn cli(&self) -> clap::Command {
        Command::new("rev")
            .about("reverse lines characterwise")
            .author("Nathan Fisher")
            .args([
                Arg::new("verbose")
                    .short('v')
                    .long("verbose")
                    .help("print a header between each file")
                    .action(ArgAction::SetTrue),
                Arg::new("color")
                    .short('c')
                    .long("color")
                    .value_parser(["always", "ansi", "auto", "never"]),
                Arg::new("file")
                    .help("if file is '-' read from stdin")
                    .num_args(0..),
            ])
    }

    fn run(&self, matches: Option<&clap::ArgMatches>) -> Result<(), Box<dyn std::error::Error>> {
        let Some(matches) = matches else {
            return Err(Box::new(io::Error::new(ErrorKind::Other, "No input")));
        };
        let files: Vec<_> = match matches.get_many::<String>("file") {
            Some(c) => c.cloned().collect(),
            None => vec![String::from("-")],
        };
        let color = match matches.get_one::<String>("color").map(String::as_str) {
            Some("always") => ColorChoice::Always,
            Some("ansi") => ColorChoice::AlwaysAnsi,
            Some("auto") => {
                if atty::is(atty::Stream::Stdout) {
                    ColorChoice::Auto
                } else {
                    ColorChoice::Never
                }
            }
            _ => ColorChoice::Never,
        };
        for (index, file) in files.into_iter().enumerate() {
            if matches.get_flag("verbose") {
                let mut stdout = StandardStream::stdout(color);
                stdout.set_color(ColorSpec::new().set_fg(Some(Color::Green)))?;
                match index {
                    0 => writeln!(stdout, "===> {file} <==="),
                    _ => writeln!(stdout, "\n===> {file} <==="),
                }?;
                stdout.reset()?;
            }
            rev_file(&file)?;
        }
        Ok(())
    }

    fn path(&self) -> Option<crate::Path> {
        Some(crate::Path::UsrBin)
    }
}

fn rev_file(file: &str) -> Result<(), io::Error> {
    let reader: Box<dyn BufRead> = if file == "-" {
        Box::new(BufReader::new(io::stdin()))
    } else {
        let buf = File::open(file)?;
        Box::new(BufReader::new(buf))
    };
    for line in reader.lines() {
        println!("{}", line.unwrap().chars().rev().collect::<String>());
    }
    Ok(())
}