use std::{error::Error, fs, env::{self, Args}};

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

impl Config {
    pub fn new(mut args: env::Args) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("not enough arguments!");
        }
        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 query string"),
        };
        let case_sensitive = env::var("CASE_INSENTSITIVE").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 result = if config.case_sensitive {
        search(&config.query, &contents)
    } else {
        search_case_insensitive(&config.query, &contents)
    };
    for line in result {
        println!("{}", line);
    }

    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> {
    let mut results = Vec::new();

    let query = query.to_lowercase();
    for line in contents.lines() {
        if line.to_lowercase().contains(&query) {
            results.push(line);
        }
    }
    results
}

#[cfg(test)]
mod tests {
    use crate::{search, search_case_insensitive};

    #[test]
    fn case_sensitive() {
        let query = "Rust";

        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Trust me";
        assert_eq!(vec!["Rust:"], 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_case_insensitive(query, contents)
        )
    }
}