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

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

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

impl Config {
    pub fn new<I: Iterator<Item = String>>(mut args_iterator: I) -> Result<Config, &'static str> {
        args_iterator.next();

        let query = match args_iterator.next() {
            Some(arg) => arg,
            None => return Err("Did not get a query string"),
        };
        let filename = match args_iterator.next() {
            Some(arg) => arg,
            None => return Err("Did not get a file name"),
        };

        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();

        Ok(Config {
            query,
            filename,
            case_sensitive,
        })
    }
}

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

    #[test]
    fn constructor_returns_error_when_not_enough_arguments() {
        let args = [String::from("arg1"), String::from("arg2")];
        let args_iter = args.iter().map(|s| s.to_string());
        assert!(Config::new(args_iter).is_err());
    }

    #[test]
    fn constructor_does_not_return_error_when_enough_arguments() {
        let args = [
            String::from("arg1"),
            String::from("arg2"),
            String::from("args3"),
        ];
        let args_iter = args.iter().map(|s| s.to_string());
        assert!(!Config::new(args_iter).is_err());
    }

    #[test]
    fn constructor_returns_valid_config_struct() {
        let args = [
            String::from("_"),
            String::from("query"),
            String::from("filename"),
        ];
        let args_iter = args.iter().map(|s| s.to_string());
        let config = Config::new(args_iter).unwrap();
        let other = Config {
            query: String::from("query"),
            filename: String::from("filename"),
            case_sensitive: true,
        };
        assert!(config.filename == other.filename && config.query == other.query)
    }

    #[test]
    fn run_returns_ok_with_valid_file() {
        let args = [
            String::from("_"),
            String::from("_"),
            String::from("poem.txt"),
        ];
        let args_iter = args.iter().map(|s| s.to_string());
        let config = Config::new(args_iter).unwrap();
        assert!(run(config).is_ok());
    }

    #[test]
    fn run_returns_err_with_invalid_file() {
        let args = [
            String::from("_"),
            String::from("_"),
            String::from("not_valid.txt"),
        ];
        let args_iter = args.iter().map(|s| s.to_string());
        let config = Config::new(args_iter).unwrap();
        assert!(run(config).is_err());
    }

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

        assert_eq!(vec!["safe, fast, productive."], search(query, contents));
    }

    #[test]
    fn no_search_results() {
        let query = "no_results";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.";

        assert_eq!(Vec::<&str>::new(), 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)
        );
    }

    #[test]
    fn case_sensitive_does_not_return_insensitive() {
        let query = "rUsT";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Trust me.";
        assert_eq!(Vec::<&str>::new(), search(query, contents));
    }
}