smolgrep/src/parser.rs

use std::{
    fs::File,
    io::{BufRead, BufReader},
};

use anyhow::Context;
use regex::Regex;

pub fn read_lines(
    file_path: &str,
) -> anyhow::Result<impl Iterator<Item = std::io::Result<String>>, anyhow::Error> {
    if file_path.is_empty() {
        return Err(anyhow::anyhow!("File path cannot be empty"));
    }

    let file =
        File::open(file_path).with_context(|| format!("failed to open file: {file_path}"))?;
    let reader = BufReader::new(file);

    Ok(reader.lines())
}

pub fn match_pattern(
    iter: impl Iterator<Item = std::io::Result<String>>,
    pattern: &str,
) -> anyhow::Result<Vec<String>, anyhow::Error> {
    let reg = Regex::new(pattern).with_context(|| format!("invalid regex: {:?}", pattern))?;
    let lines = iter.collect::<std::io::Result<Vec<_>>>()?;

    let matches = lines.into_iter().filter(|line| reg.is_match(line)).collect::<Vec<_>>();

    Ok(matches)
}