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

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

impl Config {
    pub fn new(mut args: std::env::Args) -> Result<Config, &'static str> {
        args.next(); // 过滤掉第一个
        let query = match args.next() {
            None => return Err("没有传入query参数"),
            Some(t) => t,
        };

        let filename = match args.next() {
            Some(t) => t,
            None => return Err("没有传入filename"),
        };

        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(())
}


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

mod tests {
    use super::*;

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

        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)
        );
    }
}