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

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

impl Config {
    pub fn new(mut args: std::env::Args) -> Result<Config, &'static str> {
        args.next();
        let query = match args.next() {
            Some(arg) => arg,
            None => return Err("query argument required"),
        };
        let filename = match args.next() {
            Some(arg) => arg,
            None => return Err("filename argument required"),
        };
        let case_sensitive = std::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)?;
    let results = if config.case_sensitive {
        search(&config.query, &contents)
    } else {
        search_ignore_case(&config.query, &contents)
    };
    for line in results {
        println!("{}", line);
    }
    Ok(())
}

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

pub fn search_ignore_case<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let query = query.to_lowercase();
    contents.lines().filter(|x| x.to_lowercase().contains(&query)).collect()
}

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

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

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

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

        assert_eq!(vec!["Rust:","Trust me."], search_ignore_case(query, contents));
    }

}