//! # minigrep
//!
//! `minigrep` approximates the basic functionality of `grep(1)`

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

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

impl Config {
    /// Creates a new Config instance
    ///
    /// # Examples
    ///
    /// ```
    /// use superhawk610_minigrep::Config;
    ///
    /// let args = ["/path/to/bin", "foo", "poem.txt", "-i"].iter().map(|s| s.to_string());
    /// let c = Config::new(args).unwrap();
    ///
    /// assert_eq!(c.query, "foo");
    /// assert_eq!(c.filename, "poem.txt");
    /// assert_eq!(c.case_sensitive, false);
    /// ```
    pub fn new<T>(args: T) -> Result<Config, &'static str>
    where
        T: Iterator<Item = String>,
    {
        let mut main_args = Vec::new();
        let mut case_sensitive = true;

        for arg in args.skip(1) {
            let mut iter = arg.chars();

            if iter.next().unwrap() == '-' {
                match iter.next() {
                    Some(c) => match c {
                        'i' => case_sensitive = false,
                        _ => {}
                    },
                    None => {
                        return Err(
                            "An arg that begins with - must be followed by one or more characters",
                        );
                    }
                }
            } else {
                main_args.push(arg);
            }
        }

        if main_args.len() < 2 {
            return Err("not enough args");
        }

        let query = main_args[0].clone();
        let filename = main_args[1].clone();

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

/// Runs the application's main logic.
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 for the given `query` in `contents` (case-sensitive) and
/// return a vector containing each line with at least one match.
///
/// # Examples
///
/// ```
/// use superhawk610_minigrep::search;
///
/// let needle = "foo".to_string();
/// let haystack = "foo\nbar\nbaz".to_string();
///
/// let matches = search(&needle, &haystack);
///
/// assert_eq!(matches, vec!["foo"]);
/// ```
pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    contents
        .lines()
        .filter(|line| line.contains(query))
        .collect()
}

/// Search for the given `query` in `contents` (case-insensitive) and
/// return a vector containing each line with at least one match.
///
/// # Examples
///
/// ```
/// use superhawk610_minigrep::search_case_insensitive;
///
/// let needle = "FoO".to_string();
/// let haystack = "foo\nbar\nbaz".to_string();
///
/// let matches = search_case_insensitive(&needle, &haystack);
///
/// assert_eq!(matches, vec!["foo"]);
/// ```
pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let query = query.to_lowercase();

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

#[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)
        );
    }
}