//! Library containing code backing minigrep

mod tests;

use std::env;
use std::error::Error;
use std::fs;

pub struct Config {
    pub filename: String,
    pub query: String,
    pub case_sensitive: bool,
}

impl Config {
    pub fn new(mut args: env::Args) -> Result<Self, &'static str> {
        args.next();

        let query = match args.next() {
            Some(arg) => arg,
            None => return Err("Didn't get a query string"),
        };
        let filename = match args.next() {
            Some(arg) => arg,
            None => return Err("Didn't get a filename"),
        };
        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();

        Ok(Self {
            query,
            filename,
            case_sensitive,
        })
    }
}

/// Searches a newline delimited string for matches against a query. Exact matches only
pub fn run(config: &Config) -> Result<(), Box<dyn Error>> {
    let contents = fs::read_to_string(&config.filename)?;
    if config.case_sensitive {
        search(&config.query, &contents);
    } else {
        search_case_insensitive(&config.query, &contents);
    }
    Ok(())
}

fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    contents
        .lines()
        .filter(|line| line.contains(query))
        .collect()
}

fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    contents
        .lines()
        .filter(|line| line.to_lowercase().contains(&query.to_lowercase()))
        .collect()
}