cli-app-base/examples/rotn.rs

//! This is a complete example, showing how to use the boilerplate in a real-world application

#[macro_use]
extern crate serde_derive;
#[macro_use]
extern crate failure;
#[macro_use]
extern crate log;

use clap::ArgMatches;
use clappconfig::AppConfig;
use failure::Fallible;
use smart_default::SmartDefault;
use std::collections::HashMap;
use std::fs::OpenOptions;
use std::io::Read;
use std::path::PathBuf;
use std::str::FromStr;

#[derive(Serialize, Deserialize, Debug, SmartDefault)]
#[serde(deny_unknown_fields)]
#[serde(default)]
struct Config {
    #[default = "info"]
    logging: String,
    log_modules: HashMap<String, String>,

    #[default = 13]
    offset: i32,
}

/// This is a struct created by the `Config::configure()` method
/// (and returned by the `Config::init()`)
struct Main {
    config: Config,
    input_file: PathBuf,
}

impl AppConfig for Config {
    type Init = Main;

    /// Logging from the config struct
    fn logging(&self) -> &str {
        &self.logging
    }

    /// Exclude some spammy libs from logs
    fn logging_suppress_mods(&self) -> Option<Vec<&str>> {
        Some(vec![
            // we do not actually use these here, this is an example
            "tokio_reactor",
            "tokio_io",
            "hyper",
            "reqwest",
            "mio",
            "want",
        ])
    }

    /// We do not want a banner
    fn print_banner(_name: &str, _version: &str) {
        // Disable
    }

    /// Suppress stderr logging on startup
    fn pre_log_println(_message: String) {
        // Disable
    }

    /// Get log module levels to use
    /// (take priority over the main log level & suppressing)
    fn logging_mod_levels(&self) -> Option<&HashMap<String, String>> {
        // we let user configure these
        Some(&self.log_modules)
    }

    /// Add our custom args
    fn add_args<'a: 'b, 'b>(clap: clap::App<'a, 'b>) -> clap::App<'a, 'b> {
        // Default impl
        clap.arg(
            clap::Arg::with_name("input")
                .short("i")
                .long("input")
                .value_name("FILE")
                // Work-around for default-config acting as short-circuit (similar to --version and --help)
                .required_unless("default-config")
                .help("Input file to rotate")
                .takes_value(true),
        )
        .arg(
            clap::Arg::with_name("offset")
                .short("n")
                .long("shift")
                .value_name("N")
                .help("Positive or negative rotation, default 13")
                .takes_value(true),
        )
    }

    /// Here finalize configuration and parse our custom arguments.
    ///
    /// Sometimes these go into `Config`, then we can use `type Init = Config;`
    ///
    /// Here we don't want to have the input path in config, so a different struct is used.
    ///
    /// This can also be solved using `#[serde(skip)]` on the field, but sometimes that is not
    /// possible.
    fn configure<'a>(mut self, clap: &ArgMatches<'a>) -> Fallible<Self::Init> {
        let input = clap.value_of("input").unwrap().to_string();

        // Logging is initialized now - feel free to use it
        debug!("Input: {}", input);

        if input.is_empty() {
            bail!("Input is required!");
        }

        // `?` can be used to abort
        let pb = PathBuf::from_str(&input)?.canonicalize()?;

        debug!("Input path: {}", pb.display());

        if !pb.is_file() {
            return Err(format_err!("Input is not a file!"));
        }

        // Set offset by arg
        if let Some(v) = clap.value_of("offset") {
            self.offset = v.parse()?;
        }

        debug!("Rot raw: {}", self.offset);

        self.offset = i32::rem_euclid(self.offset, 26);
        assert!(self.offset < 26);

        debug!("Rot normalized: {}", self.offset);

        // We construct the `Init` struct here
        Ok(Main {
            config: self,
            input_file: pb,
        })
    }
}

fn main() -> Fallible<()> {
    // Using custom version (default is CARGO_PKG_VERSION)
    let version = format!(
        "{} by {}",
        env!("CARGO_PKG_VERSION"),
        env!("CARGO_PKG_AUTHORS")
    );

    let main = Config::init("Rot-N", "rotn_config.json", Some(&version))?;

    // rot13

    let mut f = OpenOptions::new()
        .read(true)
        .open(main.input_file)?;

    let mut buf = String::new();
    f.read_to_string(&mut buf)?;

    println!("{}", rot_n(buf, main.config.offset as u8));

    Ok(())
}

/// Rotate a string
fn rot_n(string: String, rot: u8) -> String {
    assert!(rot < 26);

    const LOWER: &[u8] = b"abcdefghijklmnopqrstuvwxyz";
    const UPPER: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    string
        .chars()
        .map(|c| match c {
            'A'..='Z' => UPPER[((c as u8 - 'A' as u8 + rot) % 26) as usize] as char,
            'a'..='z' => LOWER[((c as u8 - 'a' as u8 + rot) % 26) as usize] as char,
            _ => c,
        })
        .collect()
}