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//! # Config for minigrep
//! `Config` is data structure to be used for minigrep

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

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

impl Config {
    pub fn new<I>(mut args: I) -> Result<Config, &'static str>
    where
        I: Iterator<Item = String>
    {
        let query = match args.next() {
            Some(arg) => arg,
            None => return Err("Didn't get a query string"),
        };
        let fname = 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,
            fname,
            case_sensitive,
        })
    }
}

/// run to search string with query against contents from the given file
/// 
/// # Examples
/// 
/// ```
/// use std::process;
/// use minigrep_robin::Config;
/// 
/// let args = vec![
///         String::from("string_to_query"),
///         String::from("poem.txt")]
///     .into_iter();
/// 
/// let config = Config::new(args).unwrap_or_else(|err| {
///    eprintln!("Problem parsing arguments: {}", err);
///    process::exit(1);
/// });
/// 
/// if let Err(e) = minigrep_robin::run(config) {
///     eprintln!("Application error: {}", e);
///     process::exit(1);
/// }
/// ```
pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
    let contents = fs::read_to_string(config.fname)?;

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

    for line in results {
        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 query = query.to_lowercase();
    contents
        .lines()
        .filter(|line| line.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_case_insensitive(query, contents));
    }
}