use std::error::Error;
use std::fs::File;
use std::io::prelude::*;
use std::env;

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<Error>> {
    let mut f = File::open(config.filename)?;
    let mut s = String::new();
    f.read_to_string(&mut s)?;

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

    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();
    let mut res = Vec::new();

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

    res
}

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

    #[test]
    fn one_result() {
        let query = "duct";
        let contents = "\
        Rust:
safe, fast, productive
pick three.
Duck 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)
        )
    }
}