bashkit 0.4.1

Awesomely fast virtual sandbox with bash and file system
Documentation 
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//! cat builtin command

use async_trait::async_trait;
use std::path::Path;

use super::{Builtin, Context, read_text_file};
use crate::error::Result;
use crate::interpreter::ExecResult;

/// The cat builtin command.
pub struct Cat;

#[async_trait]
impl Builtin for Cat {
    async fn execute(&self, ctx: Context<'_>) -> Result<ExecResult> {
        if let Some(r) = super::check_help_version(
            ctx.args,
            "Usage: cat [OPTION]... [FILE]...\nConcatenate FILE(s) to standard output.\n\n  -n\t\tnumber all output lines\n  -v\t\tuse ^ and M- notation\n  -e\t\tequivalent to -v (simplified)\n  -t\t\tequivalent to -v (simplified)\n  --help\tdisplay this help and exit\n  --version\toutput version information and exit\n",
            Some("cat (bashkit) 0.1"),
        ) {
            return Ok(r);
        }
        let mut output = String::new();
        let mut show_nonprinting = false;
        let mut number_lines = false;
        let mut files: Vec<&str> = Vec::new();

        // Parse flags
        for arg in ctx.args {
            if arg.starts_with('-') && arg.len() > 1 && !arg.starts_with("--") {
                for ch in arg[1..].chars() {
                    match ch {
                        'v' => show_nonprinting = true,
                        'n' => number_lines = true,
                        'e' => show_nonprinting = true, // -e implies -v + show $ at EOL (simplified)
                        't' => show_nonprinting = true, // -t implies -v + show ^I for tabs (simplified)
                        _ => {}
                    }
                }
            } else {
                files.push(arg);
            }
        }

        let mut raw = String::new();

        if files.is_empty() {
            if let Some(stdin) = ctx.stdin {
                raw.push_str(stdin);
            }
        } else {
            for file in &files {
                if *file == "-" {
                    if let Some(stdin) = ctx.stdin {
                        raw.push_str(stdin);
                    }
                } else {
                    let path = if Path::new(file).is_absolute() {
                        file.to_string()
                    } else {
                        ctx.cwd.join(file).to_string_lossy().to_string()
                    };

                    let text = match read_text_file(&*ctx.fs, Path::new(&path), "cat").await {
                        Ok(t) => t,
                        Err(e) => return Ok(e),
                    };
                    raw.push_str(&text);
                }
            }
        }

        if show_nonprinting {
            for ch in raw.chars() {
                match ch {
                    '\n' | '\t' => output.push(ch), // pass through newline and tab
                    c if (c as u32) < 32 => {
                        // Control characters: ^@, ^A, ..., ^Z, ^[, ^\, ^], ^^, ^_
                        output.push('^');
                        output.push((c as u8 + 64) as char);
                    }
                    '\x7f' => {
                        output.push('^');
                        output.push('?');
                    }
                    c => output.push(c),
                }
            }
        } else {
            output = raw;
        }

        if number_lines {
            let lines: Vec<&str> = output.split('\n').collect();
            let mut numbered = String::new();
            for (i, line) in lines.iter().enumerate() {
                if i < lines.len() - 1 || !line.is_empty() {
                    numbered.push_str(&format!("     {}\t{}", i + 1, line));
                    if i < lines.len() - 1 {
                        numbered.push('\n');
                    }
                }
            }
            output = numbered;
        }

        Ok(ExecResult::ok(output))
    }
}