Fun Log Parser

main.rs

extern crate chrono;
extern crate regex;

use chrono::{NaiveDate, NaiveDateTime};
use regex::Regex;

use std::io::{self, BufRead};

struct Item {
    date: NaiveDate,
    count: i32,
}

impl Item {
    fn new(date: NaiveDate) -> Self {
        Item { date, count: 1 }
    }

    fn add(&mut self) -> &Self {
        self.count += 1;
        self
    }
}

fn read_input_line_by_line() {
    let stdin = io::stdin();
    let search = Regex::new(r"\[([^\]]*)\]").unwrap();
    let mut results: Vec<Item> = Vec::new();
    for line in stdin.lock().lines() {
        let line = line.unwrap();
        parse_line(&search, &line[..], &mut results);
    }
    for result in results.iter() {
        println!("On {}, there were {} calls", result.date, result.count);
    }
}

fn parse_line(search: &Regex, line: &str, results: &mut Vec<Item>) {
    let parts = match search.captures(line) {
        Some(parts) => parts,
        _ => return,
    };
    let date_time = parts.get(1).unwrap().as_str();
    let date = NaiveDateTime::parse_from_str(date_time, "%Y-%m-%d %H:%M").unwrap();
    match results.iter_mut().find(|r| r.date == date.date()) {
        Some(r) => {
            r.add();
        }
        None => {
            results.push(Item::new(date.date()));
        }
    };
}

fn main() {
    read_input_line_by_line();
}