// 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.

// spell-checker:ignore (ToDO) PSKIP linebreak ostream parasplit tabwidth xanti xprefix

use clap::{crate_version, Arg, ArgAction, ArgMatches, Command};
use std::fs::File;
use std::io::{stdin, stdout, BufReader, BufWriter, Read, Stdout, Write};
use uucore::display::Quotable;
use uucore::error::{FromIo, UResult, USimpleError, UUsageError};
use uucore::{format_usage, help_about, help_usage};

use linebreak::break_lines;
use parasplit::ParagraphStream;

mod linebreak;
mod parasplit;

const ABOUT: &str = help_about!("fmt.md");
const USAGE: &str = help_usage!("fmt.md");
const MAX_WIDTH: usize = 2500;
const DEFAULT_GOAL: usize = 70;
const DEFAULT_WIDTH: usize = 75;
// by default, goal is 93% of width
const DEFAULT_GOAL_TO_WIDTH_RATIO: usize = 93;

mod options {
    pub const CROWN_MARGIN: &str = "crown-margin";
    pub const TAGGED_PARAGRAPH: &str = "tagged-paragraph";
    pub const PRESERVE_HEADERS: &str = "preserve-headers";
    pub const SPLIT_ONLY: &str = "split-only";
    pub const UNIFORM_SPACING: &str = "uniform-spacing";
    pub const PREFIX: &str = "prefix";
    pub const SKIP_PREFIX: &str = "skip-prefix";
    pub const EXACT_PREFIX: &str = "exact-prefix";
    pub const EXACT_SKIP_PREFIX: &str = "exact-skip-prefix";
    pub const WIDTH: &str = "width";
    pub const GOAL: &str = "goal";
    pub const QUICK: &str = "quick";
    pub const TAB_WIDTH: &str = "tab-width";
    pub const FILES_OR_WIDTH: &str = "files";
}

pub type FileOrStdReader = BufReader<Box<dyn Read + 'static>>;

pub struct FmtOptions {
    crown: bool,
    tagged: bool,
    mail: bool,
    split_only: bool,
    prefix: Option<String>,
    xprefix: bool,
    anti_prefix: Option<String>,
    xanti_prefix: bool,
    uniform: bool,
    quick: bool,
    width: usize,
    goal: usize,
    tabwidth: usize,
}

impl FmtOptions {
    fn from_matches(matches: &ArgMatches) -> UResult<Self> {
        let mut tagged = matches.get_flag(options::TAGGED_PARAGRAPH);
        let mut crown = matches.get_flag(options::CROWN_MARGIN);

        let mail = matches.get_flag(options::PRESERVE_HEADERS);
        let uniform = matches.get_flag(options::UNIFORM_SPACING);
        let quick = matches.get_flag(options::QUICK);
        let split_only = matches.get_flag(options::SPLIT_ONLY);

        if crown {
            tagged = false;
        }
        if split_only {
            crown = false;
            tagged = false;
        }

        let xprefix = matches.contains_id(options::EXACT_PREFIX);
        let xanti_prefix = matches.contains_id(options::SKIP_PREFIX);

        let prefix = matches.get_one::<String>(options::PREFIX).map(String::from);
        let anti_prefix = matches
            .get_one::<String>(options::SKIP_PREFIX)
            .map(String::from);

        let width_opt = extract_width(matches)?;
        let goal_opt_str = matches.get_one::<String>(options::GOAL);
        let goal_opt = if let Some(goal_str) = goal_opt_str {
            match goal_str.parse::<usize>() {
                Ok(goal) => Some(goal),
                Err(_) => {
                    return Err(USimpleError::new(
                        1,
                        format!("invalid goal: {}", goal_str.quote()),
                    ));
                }
            }
        } else {
            None
        };

        let (width, goal) = match (width_opt, goal_opt) {
            (Some(w), Some(g)) => {
                if g > w {
                    return Err(USimpleError::new(1, "GOAL cannot be greater than WIDTH."));
                }
                (w, g)
            }
            (Some(w), None) => {
                // Only allow a goal of zero if the width is set to be zero
                let g = (w * DEFAULT_GOAL_TO_WIDTH_RATIO / 100).max(if w == 0 { 0 } else { 1 });
                (w, g)
            }
            (None, Some(g)) => {
                if g > DEFAULT_WIDTH {
                    return Err(USimpleError::new(1, "GOAL cannot be greater than WIDTH."));
                }
                let w = (g * 100 / DEFAULT_GOAL_TO_WIDTH_RATIO).max(g + 3);
                (w, g)
            }
            (None, None) => (DEFAULT_WIDTH, DEFAULT_GOAL),
        };
        debug_assert!(width >= goal, "GOAL {goal} should not be greater than WIDTH {width} when given {width_opt:?} and {goal_opt:?}.");

        if width > MAX_WIDTH {
            return Err(USimpleError::new(
                1,
                format!("invalid width: '{width}': Numerical result out of range"),
            ));
        }

        let mut tabwidth = 8;
        if let Some(s) = matches.get_one::<String>(options::TAB_WIDTH) {
            tabwidth = match s.parse::<usize>() {
                Ok(t) => t,
                Err(e) => {
                    return Err(USimpleError::new(
                        1,
                        format!("Invalid TABWIDTH specification: {}: {}", s.quote(), e),
                    ));
                }
            };
        };

        if tabwidth < 1 {
            tabwidth = 1;
        }

        Ok(Self {
            crown,
            tagged,
            mail,
            split_only,
            prefix,
            xprefix,
            anti_prefix,
            xanti_prefix,
            uniform,
            quick,
            width,
            goal,
            tabwidth,
        })
    }
}

/// Process the content of a file and format it according to the provided options.
///
/// # Arguments
///
/// * `file_name` - The name of the file to process. A value of "-" represents the standard input.
/// * `fmt_opts` - A reference to a `FmtOptions` struct containing the formatting options.
/// * `ostream` - A mutable reference to a `BufWriter` wrapping the standard output.
///
/// # Returns
///
/// A `UResult<()>` indicating success or failure.
fn process_file(
    file_name: &str,
    fmt_opts: &FmtOptions,
    ostream: &mut BufWriter<Stdout>,
) -> UResult<()> {
    let mut fp = BufReader::new(match file_name {
        "-" => Box::new(stdin()) as Box<dyn Read + 'static>,
        _ => {
            let f = File::open(file_name)
                .map_err_context(|| format!("cannot open {} for reading", file_name.quote()))?;
            if f.metadata()
                .map_err_context(|| format!("cannot get metadata for {}", file_name.quote()))?
                .is_dir()
            {
                return Err(USimpleError::new(1, "read error".to_string()));
            }

            Box::new(f) as Box<dyn Read + 'static>
        }
    });

    let p_stream = ParagraphStream::new(fmt_opts, &mut fp);
    for para_result in p_stream {
        match para_result {
            Err(s) => {
                ostream
                    .write_all(s.as_bytes())
                    .map_err_context(|| "failed to write output".to_string())?;
                ostream
                    .write_all(b"\n")
                    .map_err_context(|| "failed to write output".to_string())?;
            }
            Ok(para) => break_lines(&para, fmt_opts, ostream)
                .map_err_context(|| "failed to write output".to_string())?,
        }
    }

    // flush the output after each file
    ostream
        .flush()
        .map_err_context(|| "failed to write output".to_string())?;

    Ok(())
}

/// Extract the file names from the positional arguments, ignoring any negative width in the first
/// position.
///
/// # Returns
/// A `UResult<()>` with the file names, or an error if one of the file names could not be parsed
/// (e.g., it is given as a negative number not in the first argument and not after a --
fn extract_files(matches: &ArgMatches) -> UResult<Vec<String>> {
    let in_first_pos = matches
        .index_of(options::FILES_OR_WIDTH)
        .is_some_and(|x| x == 1);
    let is_neg = |s: &str| s.parse::<isize>().is_ok_and(|w| w < 0);

    let files: UResult<Vec<String>> = matches
        .get_many::<String>(options::FILES_OR_WIDTH)
        .into_iter()
        .flatten()
        .enumerate()
        .filter_map(|(i, x)| {
            if is_neg(x) {
                if in_first_pos && i == 0 {
                    None
                } else {
                    let first_num = x.chars().nth(1).expect("a negative number should be at least two characters long");
                    Some(Err(
                        UUsageError::new(1, format!("invalid option -- {first_num}; -WIDTH is recognized only when it is the first\noption; use -w N instead"))
                    ))
                }
            } else {
                Some(Ok(x.clone()))
            }
        })
        .collect();

    if files.as_ref().is_ok_and(|f| f.is_empty()) {
        Ok(vec!["-".into()])
    } else {
        files
    }
}

fn extract_width(matches: &ArgMatches) -> UResult<Option<usize>> {
    let width_opt = matches.get_one::<String>(options::WIDTH);
    if let Some(width_str) = width_opt {
        if let Ok(width) = width_str.parse::<usize>() {
            return Ok(Some(width));
        } else {
            return Err(USimpleError::new(
                1,
                format!("invalid width: {}", width_str.quote()),
            ));
        }
    }

    if let Some(1) = matches.index_of(options::FILES_OR_WIDTH) {
        let width_arg = matches.get_one::<String>(options::FILES_OR_WIDTH).unwrap();
        if let Some(num) = width_arg.strip_prefix('-') {
            Ok(num.parse::<usize>().ok())
        } else {
            // will be treated as a file name
            Ok(None)
        }
    } else {
        Ok(None)
    }
}

#[uucore::main]
pub fn uumain(args: impl uucore::Args) -> UResult<()> {
    let args: Vec<_> = args.collect();

    // Warn the user if it looks like we're trying to pass a number in the first
    // argument with non-numeric characters
    if let Some(first_arg) = args.get(1) {
        let first_arg = first_arg.to_string_lossy();
        let malformed_number = first_arg.starts_with('-')
            && first_arg.chars().nth(1).is_some_and(|c| c.is_ascii_digit())
            && first_arg.chars().skip(2).any(|c| !c.is_ascii_digit());
        if malformed_number {
            return Err(USimpleError::new(
                1,
                format!(
                    "invalid width: {}",
                    first_arg.strip_prefix('-').unwrap().quote()
                ),
            ));
        }
    }

    let matches = uu_app().try_get_matches_from(&args)?;

    let files = extract_files(&matches)?;

    let fmt_opts = FmtOptions::from_matches(&matches)?;

    let mut ostream = BufWriter::new(stdout());

    for file_name in &files {
        process_file(file_name, &fmt_opts, &mut ostream)?;
    }

    Ok(())
}

pub fn uu_app() -> Command {
    Command::new(uucore::util_name())
        .version(crate_version!())
        .about(ABOUT)
        .override_usage(format_usage(USAGE))
        .infer_long_args(true)
        .args_override_self(true)
        .arg(
            Arg::new(options::CROWN_MARGIN)
                .short('c')
                .long(options::CROWN_MARGIN)
                .help(
                    "First and second line of paragraph \
                    may have different indentations, in which \
                    case the first line's indentation is preserved, \
                    and each subsequent line's indentation matches the second line.",
                )
                .action(ArgAction::SetTrue),
        )
        .arg(
            Arg::new(options::TAGGED_PARAGRAPH)
                .short('t')
                .long("tagged-paragraph")
                .help(
                    "Like -c, except that the first and second line of a paragraph *must* \
                    have different indentation or they are treated as separate paragraphs.",
                )
                .action(ArgAction::SetTrue),
        )
        .arg(
            Arg::new(options::PRESERVE_HEADERS)
                .short('m')
                .long("preserve-headers")
                .help(
                    "Attempt to detect and preserve mail headers in the input. \
                    Be careful when combining this flag with -p.",
                )
                .action(ArgAction::SetTrue),
        )
        .arg(
            Arg::new(options::SPLIT_ONLY)
                .short('s')
                .long("split-only")
                .help("Split lines only, do not reflow.")
                .action(ArgAction::SetTrue),
        )
        .arg(
            Arg::new(options::UNIFORM_SPACING)
                .short('u')
                .long("uniform-spacing")
                .help(
                    "Insert exactly one \
                    space between words, and two between sentences. \
                    Sentence breaks in the input are detected as [?!.] \
                    followed by two spaces or a newline; other punctuation \
                    is not interpreted as a sentence break.",
                )
                .action(ArgAction::SetTrue),
        )
        .arg(
            Arg::new(options::PREFIX)
                .short('p')
                .long("prefix")
                .help(
                    "Reformat only lines \
                    beginning with PREFIX, reattaching PREFIX to reformatted lines. \
                    Unless -x is specified, leading whitespace will be ignored \
                    when matching PREFIX.",
                )
                .value_name("PREFIX"),
        )
        .arg(
            Arg::new(options::SKIP_PREFIX)
                .short('P')
                .long("skip-prefix")
                .help(
                    "Do not reformat lines \
                    beginning with PSKIP. Unless -X is specified, leading whitespace \
                    will be ignored when matching PSKIP",
                )
                .value_name("PSKIP"),
        )
        .arg(
            Arg::new(options::EXACT_PREFIX)
                .short('x')
                .long("exact-prefix")
                .help(
                    "PREFIX must match at the \
                    beginning of the line with no preceding whitespace.",
                )
                .action(ArgAction::SetTrue),
        )
        .arg(
            Arg::new(options::EXACT_SKIP_PREFIX)
                .short('X')
                .long("exact-skip-prefix")
                .help(
                    "PSKIP must match at the \
                    beginning of the line with no preceding whitespace.",
                )
                .action(ArgAction::SetTrue),
        )
        .arg(
            Arg::new(options::WIDTH)
                .short('w')
                .long("width")
                .help("Fill output lines up to a maximum of WIDTH columns, default 75. This can be specified as a negative number in the first argument.")
                // We must accept invalid values if they are overridden later. This is not supported by clap, so accept all strings instead.
                .value_name("WIDTH"),
        )
        .arg(
            Arg::new(options::GOAL)
                .short('g')
                .long("goal")
                .help("Goal width, default of 93% of WIDTH. Must be less than or equal to WIDTH.")
                // We must accept invalid values if they are overridden later. This is not supported by clap, so accept all strings instead.
                .value_name("GOAL"),
        )
        .arg(
            Arg::new(options::QUICK)
                .short('q')
                .long("quick")
                .help(
                    "Break lines more quickly at the \
            expense of a potentially more ragged appearance.",
                )
                .action(ArgAction::SetTrue),
        )
        .arg(
            Arg::new(options::TAB_WIDTH)
                .short('T')
                .long("tab-width")
                .help(
                    "Treat tabs as TABWIDTH spaces for \
                    determining line length, default 8. Note that this is used only for \
                    calculating line lengths; tabs are preserved in the output.",
                )
                .value_name("TABWIDTH"),
        )
        .arg(
            Arg::new(options::FILES_OR_WIDTH)
                .action(ArgAction::Append)
                .value_name("FILES")
                .value_hint(clap::ValueHint::FilePath)
                .allow_negative_numbers(true),
        )
}

#[cfg(test)]
mod tests {
    use crate::uu_app;
    use crate::{extract_files, extract_width};

    #[test]
    fn parse_negative_width() {
        let matches = uu_app()
            .try_get_matches_from(vec!["fmt", "-3", "some-file"])
            .unwrap();

        assert_eq!(extract_files(&matches).unwrap(), vec!["some-file"]);
        assert_eq!(extract_width(&matches).ok(), Some(Some(3)));
    }

    #[test]
    fn parse_width_as_arg() {
        let matches = uu_app()
            .try_get_matches_from(vec!["fmt", "-w3", "some-file"])
            .unwrap();

        assert_eq!(extract_files(&matches).unwrap(), vec!["some-file"]);
        assert_eq!(extract_width(&matches).ok(), Some(Some(3)));
    }

    #[test]
    fn parse_no_args() {
        let matches = uu_app().try_get_matches_from(vec!["fmt"]).unwrap();

        assert_eq!(extract_files(&matches).unwrap(), vec!["-"]);
        assert_eq!(extract_width(&matches).ok(), Some(None));
    }

    #[test]
    fn parse_just_file_name() {
        let matches = uu_app()
            .try_get_matches_from(vec!["fmt", "some-file"])
            .unwrap();

        assert_eq!(extract_files(&matches).unwrap(), vec!["some-file"]);
        assert_eq!(extract_width(&matches).ok(), Some(None));
    }

    #[test]
    fn parse_with_both_widths_positional_first() {
        let matches = uu_app()
            .try_get_matches_from(vec!["fmt", "-10", "-w3", "some-file"])
            .unwrap();

        assert_eq!(extract_files(&matches).unwrap(), vec!["some-file"]);
        assert_eq!(extract_width(&matches).ok(), Some(Some(3)));
    }
}
