//! # A Mini Grep Tool by Rust
//! reference: https://doc.rust-lang.org/book/ch12-00-an-io-project.html

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

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

impl Config {
    // associated functions
    pub fn new(mut args: 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 filename string")
        };

        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(())
}

/// Search a str slice in which line of another str slice's.
/// 
/// # Example
/// 
/// ```rust
/// let query = "Con";
/// let contents = "\
/// helloconcon,
/// Conster.";
/// 
/// assert_eq!(
///     vec!["Conster."],
///     eye_minigrep::search(query, contents)
/// );
/// ```
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();
    let mut results = Vec::new();

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

    results
}

#[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)
        );
    }
}