use std::env;
use std::error::Error;
use std::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,
    })
  }
}

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_case_insensitive(&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(|line| line.contains(query))
    .collect()
}

pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
  let query = query.to_lowercase();

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

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

  #[test]
  fn one_result() {
    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_case_insensitive(query, contents)
  );
}