logsplit.rs

use std::env;
use std::fs::{File, OpenOptions};
use std::io::{BufRead, BufReader, Write, BufWriter};
use std::collections::HashMap;
use chrono::{DateTime, Local};

fn main() {
    let args: Vec<String> = env::args().collect();
    if args.len() < 2 {
        println!("file name must be specified.");
        return;
    }
    let filename = &args[1];

    let file = File::open(filename).unwrap_or_else(|e| {
        panic!("failed to open file: {}", e);
    });
    let reader = BufReader::new(file);

    let mut date_map: HashMap<String, u64> = HashMap::new();

    for (_index, line) in reader.lines().enumerate() {
        let line = line.unwrap();
        let date = get_date(&line);
        let dt = DateTime::parse_from_str(date, "%d/%b/%Y:%H:%M:%S %z").unwrap();
        let date = dt.with_timezone(&Local).format("%Y%m%d").to_string();
        let count = date_map.entry(String::from(date)).or_insert(0);
        *count += 1;
    }

    let mut writers: HashMap<String, _> = HashMap::new();

    for (date, _count) in date_map {
        let ds = String::from(&date);
        let fname = format!("{}.log", &date);
        let fo = OpenOptions::new()
            .write(true)
            .truncate(false)
            .append(true)
            .create(true)
            .open(fname)
            .unwrap();
        
        let fw = BufWriter::new(fo);
        writers.insert(ds, fw);
    }

    let file = File::open(filename).unwrap_or_else(|e| {
        panic!("failed to open file: {}", e);
    });
    let reader = BufReader::new(file);

    for (_index, line) in reader.lines().enumerate() {
        let line = line.unwrap();
        let date = get_date(&line);
        let dt = DateTime::parse_from_str(date, "%d/%b/%Y:%H:%M:%S %z").unwrap();
        let ds = dt.with_timezone(&Local).format("%Y%m%d").to_string();
        let w = writers.get_mut(&ds).unwrap();
        writeln!(w, "{}", line).unwrap();
    }
}

fn get_date(line: &str) -> &str {
    let begin = line.find("[");
    if begin.is_none() {
        return &line[0..0];
    }
    let begin_pos = begin.unwrap();
    let end = line[begin_pos+1..].find("]");
    if end.is_none() {
        return &line[0..0];
    }
    let end_pos = end.unwrap() + 1;
    let date = &line[begin_pos+1 .. begin_pos+end_pos];
    return date;
}