lineprior-cli 0.3.0

use super::BuildConfigArgs;
use anyhow::{Context, Result};
use clap::Args;
use lineprior::{build_prior_book_from_reader, save_prior_book};
use std::fs::File;
use std::io::BufWriter;
use std::path::PathBuf;
use std::process::ExitCode;

#[derive(Args)]
pub struct BuildArgs {
    /// Input JSONL observation log.
    input: PathBuf,

    /// Output path for the prior book JSONL.
    #[arg(long)]
    out: PathBuf,

    #[command(flatten)]
    config: BuildConfigArgs,

    /// Fail on the first invalid record instead of skipping it with a warning.
    #[arg(long)]
    strict: bool,
}

pub fn run(args: BuildArgs) -> Result<ExitCode> {
    let file = match File::open(&args.input) {
        Ok(f) => f,
        Err(err) => {
            eprintln!("error: opening {}: {err}", args.input.display());
            return Ok(ExitCode::from(3));
        }
    };

    let config = args.config.into_build_config();

    // Streams straight from the file into the prior book -- memory stays
    // bounded by unique (state, action) pairs, not the number of lines
    // read, instead of collecting every observation into a Vec first.
    let output = match build_prior_book_from_reader(file, args.strict, &config) {
        Ok(output) => output,
        Err(err) => {
            eprintln!("error: {err}");
            return Ok(super::exit_code_for_lineprior_error(&err));
        }
    };
    for warning in &output.warnings {
        eprintln!("warning: {warning}");
    }

    if output.book.entries.is_empty() {
        eprintln!("error: no usable data");
        return Ok(ExitCode::from(2));
    }

    let out_file =
        File::create(&args.out).with_context(|| format!("creating {}", args.out.display()))?;
    save_prior_book(&output.book, BufWriter::new(out_file)).context("writing prior book")?;

    if !output.warnings.is_empty() {
        return Ok(ExitCode::from(1));
    }
    Ok(ExitCode::from(0))
}