use super::Cmd;
use clap::{parser::ValuesRef, Arg, ArgAction, ArgGroup, Command};
use std::{
    error::Error,
    fs::File,
    io::{self, BufRead, BufReader, BufWriter, Write},
    ops::{Range, RangeFrom, RangeTo},
    usize, vec,
};

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

impl Cmd for Cut {
    fn cli(&self) -> clap::Command {
        Command::new("cut")
            .about("cut out selected fields of each line of a file")
            .author("Nathan Fisher")
            .version(env!("CARGO_PKG_VERSION"))
            .args([
                Arg::new("bytes")
                    .short('b')
                    .long("bytes")
                    .help("select only these bytes")
                    .num_args(1)
                    .allow_hyphen_values(true)
                    .value_name("LIST")
                    .value_delimiter(','),
                Arg::new("characters")
                    .short('c')
                    .long("characters")
                    .help("select only these characters")
                    .num_args(1)
                    .allow_hyphen_values(true)
                    .value_name("LIST")
                    .value_delimiter(','),
                Arg::new("fields")
                    .short('f')
                    .long("fields")
                    .help("select only these fields")
                    .num_args(1)
                    .allow_hyphen_values(true)
                    .value_name("LIST")
                    .value_delimiter(','),
                Arg::new("delimiter")
                    .short('d')
                    .long("delimiter")
                    .help("use DELIM instead of TAB for field delimiter")
                    .num_args(1)
                    .value_name("DELIM"),
                Arg::new("nosplit").help("ignored").short('n'),
                Arg::new("suppress")
                    .short('s')
                    .long("only-delimited")
                    .requires("fields")
                    .action(ArgAction::SetTrue),
                Arg::new("file").value_name("FILE").num_args(0..),
            ])
            .group(
                ArgGroup::new("flags")
                    .args(["bytes", "characters", "fields"])
                    .required(true),
            )
    }

    fn run(&self, matches: Option<&clap::ArgMatches>) -> Result<(), Box<dyn Error>> {
        let Some(matches) = matches else {
            return Err(Box::new(io::Error::new(io::ErrorKind::Other, "no input")));
        };
        let files: Vec<String> = match matches.get_many::<String>("file") {
            Some(f) => f.cloned().collect(),
            None => vec!["-".to_string()],
        };
        let (ranges, operator) = if let Some(raw_ranges) = matches.get_many::<String>("bytes") {
            (get_ranges(raw_ranges)?, Operator::Bytes)
        } else if let Some(raw_ranges) = matches.get_many::<String>("characters") {
            (get_ranges(raw_ranges)?, Operator::Characters)
        } else if let Some(raw_ranges) = matches.get_many::<String>("fields") {
            (get_ranges(raw_ranges)?, Operator::Fields)
        } else {
            unreachable!()
        };
        for file in files {
            let reader: Box<dyn BufRead> = if file.as_str() == "-" {
                Box::new(BufReader::new(io::stdin()))
            } else {
                let fd = File::open(&file)?;
                Box::new(BufReader::new(fd))
            };
            for line in reader.lines() {
                match operator {
                    Operator::Bytes => print_bytes(&line?, &ranges)?,
                    Operator::Characters => print_chars(&line?, &ranges)?,
                    Operator::Fields => print_fields(
                        &line?,
                        &ranges,
                        matches.get_flag("suppress"),
                        matches.get_one::<String>("delimiter"),
                    )?,
                }
            }
        }
        Ok(())
    }

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

enum Operator {
    Bytes,
    Characters,
    Fields,
}

fn get_ranges(raw_ranges: ValuesRef<String>) -> Result<Vec<ParsedRange>, Box<dyn Error>> {
    let mut ranges = vec![];
    for range in raw_ranges {
        let parsed_range = parse_range(range)?;
        ranges.push(parsed_range);
    }
    Ok(ranges)
}

enum ParsedRange {
    Bounded(Range<usize>),
    LowerBounded(RangeFrom<usize>),
    UpperBounded(RangeTo<usize>),
    Single(usize),
}

impl From<Range<usize>> for ParsedRange {
    fn from(value: Range<usize>) -> Self {
        Self::Bounded(value)
    }
}

impl From<RangeFrom<usize>> for ParsedRange {
    fn from(value: RangeFrom<usize>) -> Self {
        Self::LowerBounded(value)
    }
}

impl From<RangeTo<usize>> for ParsedRange {
    fn from(value: RangeTo<usize>) -> Self {
        Self::UpperBounded(value)
    }
}

impl From<usize> for ParsedRange {
    fn from(value: usize) -> Self {
        Self::Single(value)
    }
}

fn combine_ranges(ranges: &[ParsedRange], max: usize) -> Vec<usize> {
    let mut outrange: Vec<usize> = vec![];
    for range in ranges {
        match range {
            ParsedRange::Bounded(r) => {
                for n in r.start..r.end {
                    outrange.push(n);
                }
            }
            ParsedRange::LowerBounded(r) => {
                for n in r.start..=max {
                    outrange.push(n);
                }
            }
            ParsedRange::UpperBounded(r) => {
                for n in 0..=r.end {
                    outrange.push(n);
                }
            }
            ParsedRange::Single(u) => outrange.push(*u),
        }
    }
    outrange.dedup();
    outrange.sort_unstable();
    outrange
}

fn parse_range(range: &str) -> Result<ParsedRange, Box<dyn Error>> {
    if let Some(stripped) = range.strip_prefix('-') {
        if range.len() > 1 {
            let end: usize = stripped.parse()?;
            if end >= 1 {
                Ok((..end - 1).into())
            } else {
                Err(Box::new(io::Error::new(
                    io::ErrorKind::Other,
                    "invalid range",
                )))
            }
        } else {
            Err(Box::new(io::Error::new(
                io::ErrorKind::Other,
                "invalid range",
            )))
        }
    } else if range.ends_with('-') {
        if range.len() > 1 {
            let start: usize = range[0..range.len()].parse()?;
            if start >= 1 {
                Ok((start - 1..).into())
            } else {
                Err(Box::new(io::Error::new(
                    io::ErrorKind::Other,
                    "invalid range",
                )))
            }
        } else {
            Err(Box::new(io::Error::new(
                io::ErrorKind::Other,
                "invalid range",
            )))
        }
    } else if let Some((start, end)) = range.split_once('-') {
        let start: usize = start.parse()?;
        let end: usize = end.parse()?;
        if start >= 1 && end > start {
            Ok((start - 1..end).into())
        } else {
            Err(Box::new(io::Error::new(
                io::ErrorKind::Other,
                "invalid range",
            )))
        }
    } else {
        let range: usize = range.parse::<usize>()? - 1;
        Ok(range.into())
    }
}

fn print_bytes(line: &str, ranges: &[ParsedRange]) -> Result<(), Box<dyn Error>> {
    let combined_ranges = combine_ranges(ranges, line.len());
    let mut writer = BufWriter::new(std::io::stdout());
    for (idx, byte) in line.as_bytes().iter().enumerate() {
        if combined_ranges.contains(&idx) {
            write!(writer, "{}", *byte as char)?;
        }
    }
    writeln!(writer)?;
    Ok(())
}

fn print_chars(line: &str, ranges: &[ParsedRange]) -> Result<(), Box<dyn Error>> {
    let combined_ranges = combine_ranges(ranges, line.len());
    let mut writer = BufWriter::new(std::io::stdout());
    for (idx, ch) in line.chars().enumerate() {
        if combined_ranges.contains(&idx) {
            write!(writer, "{}", &ch)?;
        }
    }
    writeln!(writer)?;
    Ok(())
}

fn print_fields(
    line: &str,
    ranges: &[ParsedRange],
    suppress: bool,
    delimiter: Option<&String>,
) -> Result<(), Box<dyn Error>> {
    let combined_ranges = combine_ranges(ranges, line.len());
    let mut writer = BufWriter::new(std::io::stdout());
    let delimiter = match delimiter {
        Some(d) => d,
        None => "\t",
    };
    if suppress && !line.contains(delimiter) {
        return Ok(());
    }
    let fields = line.split(delimiter);
    for (idx, field) in fields.enumerate() {
        if combined_ranges.contains(&idx) {
            write!(writer, "{field}")?;
        }
    }
    writeln!(writer)?;
    Ok(())
}