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

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

impl Config {
   pub fn new (mut args: env::Args) -> Result<Config, &'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 file name"),
        };
        
        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();

        
        return Ok(Config {
            query,
            filename,
            case_sensitive
        });
    }
}

pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
    let content = fs::read_to_string(config.filename)?;
    for line in search(&config.query, &content) {
        println!("{}", line)
    }    
    return Ok(());
}

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

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn one_result() {
        let query = "duct";
        let contents = "\
Rust:
safe, fase, productive
Pick three.";
        assert_eq!(vec!["safe, fase, productive"], search(query, contents));
    }
}