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//! DVB-S2 CLI subcommand
//!
//! This subcommand can be used to generate the LDPC codes used in the DVB-S2
//! standard. It will print the alist of the parity check matrix to `stdout`
//! and optionally compute and print the girth of the Tanner graph. See
//! [`crate::codes::dvbs2`] for more information about the DVB-S2 LDPC codes.
//!
//! # Examples
//! The r=1/2, n=64800 parity check matrix for the normal FECFRAMEs can
//! be generated with
//! ```shell
//! $ ldpc-toolbox dvbs2 --rate 1/2
//! ```
//! Its girth is computed with
//! ```shell
//! $ ldpc-toolbox dvbs2 --rate 1/2 --girth
//! Code girth = 6
//! ```
//!
//! The n=16200 code for the short FECFRAMEs is generated with
//! ```shell
//! $ ldpc-toolbox dvbs2 --rate 1/2 --short
//! ```

use crate::cli::*;
use crate::codes::dvbs2::Code;
use clap::Parser;

type Error = String;
type Result<T> = std::result::Result<T, Error>;

/// DVB-S2 CLI arguments.
#[derive(Debug, Parser)]
#[command(about = "Generates the alist of DVB-S2 LDPCs")]
pub struct Args {
    /// Coding rate
    #[arg(short, long)]
    rate: String,

    /// Enables short FECFRAME
    #[arg(long)]
    short: bool,

    /// Performs girth calculation
    #[arg(long)]
    girth: bool,
}

impl Args {
    fn code(&self) -> Result<Code> {
        match (&*self.rate, self.short) {
            ("1/4", false) => Ok(Code::R1_4),
            ("1/3", false) => Ok(Code::R1_3),
            ("2/5", false) => Ok(Code::R2_5),
            ("1/2", false) => Ok(Code::R1_2),
            ("3/5", false) => Ok(Code::R3_5),
            ("2/3", false) => Ok(Code::R2_3),
            ("3/4", false) => Ok(Code::R3_4),
            ("4/5", false) => Ok(Code::R4_5),
            ("5/6", false) => Ok(Code::R5_6),
            ("8/9", false) => Ok(Code::R8_9),
            ("9/10", false) => Ok(Code::R9_10),
            ("1/4", true) => Ok(Code::R1_4short),
            ("1/3", true) => Ok(Code::R1_3short),
            ("2/5", true) => Ok(Code::R2_5short),
            ("1/2", true) => Ok(Code::R1_2short),
            ("3/5", true) => Ok(Code::R3_5short),
            ("2/3", true) => Ok(Code::R2_3short),
            ("3/4", true) => Ok(Code::R3_4short),
            ("4/5", true) => Ok(Code::R4_5short),
            ("5/6", true) => Ok(Code::R5_6short),
            ("8/9", true) => Ok(Code::R8_9short),
            _ => Err(self.code_error()),
        }
    }

    fn code_error(&self) -> String {
        let fecframe = if self.short { "short" } else { "normal" };
        format!("Invalid rate {} for {} FECFRAME", self.rate, fecframe)
    }
}

impl Run for Args {
    fn run(&self) -> std::result::Result<(), Box<dyn std::error::Error>> {
        let h = self.code()?.h();
        if self.girth {
            if let Some(g) = h.girth() {
                println!("Code girth = {}", g);
            } else {
                println!("Code girth is infinite");
            }
        } else {
            print!("{}", h.alist());
        }
        Ok(())
    }
}