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

/// A struct that holds
/// Query - Search query
/// Filename - The name of the file
pub struct Config {
    pub query: String,
    pub filename: String,
    case_sensitive : bool,
}

impl Config {
    /// The function that parses the args and returns a Result
    /// of either, a Config type or a Err.
    /// Args - std::env::Args
    /// Returns - ```Result<Config, Err>```
    pub fn parse_config<'a>(mut args : std::env::Args) -> Result<Config, &'a str> {

        // Skipping the first arg
        args.next();
        // Checking for everyone after

        let query = match args.next() {
            Some(arg) => arg,
            None => return Err("Query missing"),
        };

        let filename = match args.next() {
            Some(arg) => arg,
            None => return Err("Filename missing")
        };

        let case = match args.next() {
            Some(x) => if x == "-case" {false} else {true},
            None => false,
        };
        Ok(Config {query, filename, case_sensitive:case})
    }
}

/// The run function that controls the search utlity
/// Also worries about case senstivity
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 (i, line) in results.into_iter().enumerate() {
        println!("{}: {}",i+1, &line);
    }

    Ok(())
}


fn search<'a> (query: &str, contents :&'a str) -> Vec<&'a str> {
    // .lines() returns an iterator
    contents
        .lines()
        .filter(|line| line.contains(query))
        .collect()
}


fn search_case_insensitive<'a> (query: &str, contents :&'a str) -> Vec<&'a str> {
    
    // .lines() returns an iterator
    contents
        .lines()
        .filter(|line| line.to_lowercase().contains(&query.to_lowercase()))
        .collect()
}

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

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

        assert_eq!(vec!["Rust:"], search(query, contents));
    }

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

        assert_eq!(vec!["Rust:"], search_case_insensitive(query, contents));
    }

    #[test]
    fn run_test() {

        let var = Config {query: "frog".to_string(), filename : "poem.txt".to_string(), case_sensitive:true};

        assert!(run(var).is_ok())
    }

}