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

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

impl Config {
    pub fn new(args: &[String]) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("not enough arguments");
        }

        let query = args[1].clone();
        let filename = args[2].clone();

        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();

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

pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
    let contents = fs::read_to_string(config.filename)?;

    for line in search(&config.query, &contents, config.case_sensitive) {
        println!("{}", line);
    }

    Ok(())
}

pub fn search<'a>(query: &str, contents: &'a str, case_sensitive: bool) -> Vec<&'a str> {
    let all_lines: Vec<&str> = contents.lines().collect();

    all_lines.iter()
        .cloned()  // why??
        .filter(|&line| {
            if case_sensitive {
                line.contains(query)
            } else {
                line.to_lowercase().contains(&query.to_lowercase())
            }

        })
        .collect::<Vec<&str>>()
}

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

    #[test]
    fn search_case_sensitive() {
        let query = "duct";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.";

        assert_eq!(
            vec!["safe, fast, productive."],
            search(query, contents, true)
        );
    }

    #[test]
    fn search_case_insensitive() {
        let query = "Duct";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.";

        assert_eq!(
            vec!["safe, fast, productive."],
            search(query, contents, false)
        );
    }
}