be-technical-interview-rust/src/main.rs

use std::{collections::BTreeMap, process::exit};
use std::error::Error;
use std::fs::File;
use std::io::Read;
use std::time::{SystemTime,Duration, UNIX_EPOCH};
use chrono::{DateTime,Utc};
use regex::Regex;

fn parse(
    mut file: File,
) -> Result<BTreeMap<String, BTreeMap<SystemTime, f64>>, Box<dyn Error>> {
    let mut contents = String::new();
    file.read_to_string(&mut contents)?;
    let re = regex::Regex::new(r"(\d+) (\w+) (\d+)")?; 
    Ok(parse_content(contents, re))
}
fn parse_content(
    contents: String,
    re: Regex,
) -> BTreeMap<String, BTreeMap<SystemTime, f64>> {
    dbg!(&contents);
    let mut metrics: BTreeMap<String, BTreeMap<SystemTime, Vec<f64>>> = BTreeMap::new();
    let show_invalid_line = | index: usize, line: &str | println!("invalid line: {} {}", index, line);

    for (index,line ) in contents.lines().enumerate() {
        if let Some(caps) = re.captures(line) {
            let timestamp_raw = &caps[1];
            let metric_name = &caps[2];
            let metric_value_raw = &caps[3];
            let timestamp = timestamp_raw.parse::<i64>().unwrap_or_else(|e|{
                println!("Parse timestamp {} error {}",timestamp_raw,e);
                0
            });
            if timestamp == 0 {
                show_invalid_line(index, line);
                continue;
            } 
            let metric_value = metric_value_raw.parse::<f64>().unwrap_or_else(|e|{
                println!("Parse metric_value {} error {}",metric_value_raw,e);
                0 as f64
            });
            if metric_value == 0 as f64 { 
                show_invalid_line(index, line);
                continue;
            } 
            let minute = UNIX_EPOCH + Duration::from_secs((timestamp - (timestamp % 60)) as u64);
            if let Some(metric) =  metrics.get_mut(metric_name) {
                if let Some(metric_data) = metric.get_mut(&minute) {
                    metric_data.push(metric_value); 
                } else {
                    metric.insert(minute, vec![metric_value]); 
                }
            } else {
                let metric_time: BTreeMap <SystemTime, Vec<f64>> =  [(minute, vec![metric_value])].into_iter().collect();
                metrics.entry(metric_name.to_string()).or_insert( metric_time);
            }
        } else {
            show_invalid_line(index, line);
        }
    }

    let mut aggregated_metrics: BTreeMap<String, BTreeMap<SystemTime, f64>> = BTreeMap::new();
    metrics.into_iter().for_each(|(metric_name, time_val_list)| {
        time_val_list.into_iter().for_each(|(time, values)| {
            let average = values.iter().sum::<f64>() / values.len() as f64;
            if let Some(metric) =  aggregated_metrics.get_mut(&metric_name) {
                if let Some(metric_data) = metric.get_mut(&time) {
                    *metric_data = average;
                } else {
                    metric.insert(time, average); 
                }
            } else {
                let metric_time: BTreeMap <SystemTime,f64> =  [(time, average)].into_iter().collect();
                aggregated_metrics.entry(metric_name.to_string()).or_insert( metric_time);
            }
        })
    });
    aggregated_metrics
}

fn load_input(file_path: &str) -> Result<BTreeMap<String, BTreeMap<SystemTime, f64>>, Box<dyn Error>> {
    let file = File::open(&file_path)
        .map_err(|err| format!("Error reading file: {} {}", &file_path, err))?;
    let metrics = parse(file)
        .map_err(|err| format!("Unable to parse: {} {}", &file_path, err))?;
    Ok(metrics)
}
fn show_metrics(metrics: BTreeMap<String, BTreeMap<SystemTime, f64>>, output_path: &str) -> Vec<String> {
    let mut output = Vec::new();
    metrics.into_iter().for_each(|(metric_name, time_val)| 
            for (time, value) in time_val {
                let output_line = format!(
                    "{} {} {:?}",
                    DateTime::<Utc>::from(time).format("%Y-%m-%dT%H:%M:%SZ"),
                    metric_name,
                    value
                );
                match output_path {
                    "vec" => output.push(output_line),
                    "print" | _  => println!("{}", output_line), 
                }
            }
    );
    output
}
fn main() {
    let default_input = String::from("input.txt");
    match load_input(&default_input) {
        Ok(metrics) => {
            let _ = show_metrics(metrics, "");
        },
        Err(err) => {
            eprint!("Error: {}", err);
            exit(1);
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn test_load_input() -> Result<(), String>{
        let default_input = String::from("input.txt");
        match load_input(&default_input) {
            Ok(_) => Ok(()),
            Err(e) => Err(format!("Error: {}",e).into()),
        }
    }
    #[test]
    fn test_invalid_line_value() -> Result<(), String>{
        let contents = String::from("1650973075 cpu A47\n");
        let re = regex::Regex::new(r"(\d+) (\w+) (\d+)")
            .map_err(|err| format!("Error regex: {}", err))?;
        let result = parse_content(contents.clone(), re);
        if result.len() == 0 {
            Ok(())
        } else {
            Err(format!("Error invalid line value: {}", contents).into())
        }
    }
        #[test]
    fn test_invalid_line_time() -> Result<(), String>{
        let contents = String::from("1650973075A cpu 47\n");
        let re = regex::Regex::new(r"(\d+) (\w+) (\d+)")
            .map_err(|err| format!("Error regex: {}", err))?;
        let result = parse_content(contents.clone(), re);
        if result.len() == 0 {
            Ok(())
        } else {
            Err(format!("Error invalid line time: {}", contents).into())
        }
    }
    #[test]
    fn test_expected_metrics() {
        use std::io::{prelude::*, BufReader};
        let default_input = String::from("input.txt");
        let metrics = load_input(&default_input).unwrap_or_default();
        let data_metrics = show_metrics(metrics, "vec");

        let expected_output = String::from("output_expected.txt");
        let file = File::open(expected_output.clone()).expect(format!("no such file: {}", expected_output).as_str());
        let buf = BufReader::new(file);
        let lines: Vec<String> = buf.lines().map(|l| l.expect("Could not parse line")).collect();

        assert_eq!(lines.join("\n"),data_metrics.join("\n"));
    }
}