rep-grep 0.0.8

wgrep/write-grep CLI
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use std::ffi::OsString;
use std::io::{self, Write};
use std::path::PathBuf;
use std::process::{Child, Command, Stdio};

use super::less::retrieve_less_version;

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("Could not parse pager command")]
    ParseError(String),
    #[error("Could not open STDIN for pager")]
    PagerError,
}

pub enum OutputType {
    Pager(Child),
    Stdout(io::Stdout),
}

impl OutputType {
    pub fn for_pager(pager: Option<String>, quit_if_one_screen: bool) -> Result<Self, Error> {
        let replace_arguments_to_less = pager.is_none();
        let pager = pager.unwrap_or_else(|| String::from("less"));
        let pagerflags = match shell_words::split(&pager) {
            Ok(pagerflags) => pagerflags,
            Err(_) => return Err(Error::ParseError(pager)),
        };

        Ok(match pagerflags.split_first() {
            Some((pager_name, args)) => {
                let pager_path = PathBuf::from(pager_name);

                let is_less = pager_path.file_stem() == Some(&OsString::from("less"));
                let process = if is_less {
                    Self::make_process_from_less_path(
                        pager_path,
                        args,
                        replace_arguments_to_less,
                        quit_if_one_screen,
                    )
                } else {
                    Self::make_process_from_pager_path(pager_path, args)
                };
                if let Some(mut process) = process {
                    process
                        .stdin(Stdio::piped())
                        .spawn()
                        .map(OutputType::Pager)
                        .unwrap_or_else(|_| OutputType::stdout())
                } else {
                    OutputType::stdout()
                }
            }
            None => OutputType::stdout(),
        })
    }

    pub fn stdout() -> Self {
        OutputType::Stdout(io::stdout())
    }

    pub fn handle(&mut self) -> Result<&mut dyn Write, crate::output::Error> {
        match *self {
            OutputType::Pager(ref mut command) => match command.stdin.as_mut() {
                Some(stdin) => Ok(stdin),
                None => Err(Error::PagerError),
            },
            OutputType::Stdout(ref mut handle) => Ok(handle),
        }
    }

    fn make_process_from_less_path(
        less_path: PathBuf,
        args: &[String],
        replace_arguments_to_less: bool,
        quit_if_one_screen: bool,
    ) -> Option<Command> {
        if let Ok(less_path) = grep_cli::resolve_binary(less_path) {
            let mut p = Command::new(&less_path);
            if args.is_empty() || replace_arguments_to_less {
                p.args(vec!["--RAW-CONTROL-CHARS"]);

                // Passing '--no-init' fixes a bug with '--quit-if-one-screen' in older
                // versions of 'less'. Unfortunately, it also breaks mouse-wheel support.
                //
                // See: http://www.greenwoodsoftware.com/less/news.530.html
                //
                // For newer versions (530 or 558 on Windows), we omit '--no-init' as it
                // is not needed anymore.
                match retrieve_less_version() {
                    None => {
                        p.arg("--no-init");
                    }
                    Some(version) if (version < 530 || (cfg!(windows) && version < 558)) => {
                        p.arg("--no-init");
                    }
                    _ => {}
                }

                if quit_if_one_screen {
                    p.arg("--quit-if-one-screen");
                }
            } else {
                p.args(args);
            }
            p.env("LESSCHARSET", "UTF-8");
            p.env("LESSANSIENDCHARS", "mK");
            Some(p)
        } else {
            None
        }
    }

    fn make_process_from_pager_path(pager_path: PathBuf, args: &[String]) -> Option<Command> {
        if pager_path.file_stem() == Some(&OsString::from("rep")) {
            eprintln!(
                "Error: rep is set as the pager, which would cause infinite recursion. \
                 Falling back to stdout."
            );
            return None;
        }
        if let Ok(pager_path) = grep_cli::resolve_binary(pager_path) {
            let mut p = Command::new(&pager_path);
            p.args(args);
            Some(p)
        } else {
            None
        }
    }
}

impl Drop for OutputType {
    fn drop(&mut self) {
        if let OutputType::Pager(ref mut command) = *self {
            let _ = command.wait();
        }
    }
}