use std::{env, error, fs};

pub struct Config {
    pub query: String,
    pub filename: String,
    pub 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("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();

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

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 lowercased_query = query.to_lowercase();

  contents.lines()
      .filter(|line| line.to_lowercase().contains(&lowercased_query))
      .collect()
}

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

    let results = if config.case_sensitive {
      search(&config.query, &contents)
    } else {
      search_case_insensitive(&config.query, &contents)
    };

    for line in results {
      println!("{}", line);
    }

    Ok(())
}

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

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

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

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

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

}