Rewrite in Go

Author: agorf

.env.sample

@@ -1 +1 @@
-.env
+*.json

.gitignore

@@ -1,6 +1,6 @@
 The MIT License
 
-Copyright (c) 2016 Angelos Orfanakos
+Copyright (c) 2016-2017 Angelos Orfanakos
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the "Software"), to deal in

Gemfile

@@ -1,56 +1,65 @@
 # trafficjam
 
-A Ruby script that uses the [Google Maps API][] to notify you if your daily
-commute has unusual traffic.
+Queries the [Google Maps API][] and notifies you if a trip has unusual traffic.
+Useful for knowing about traffic in your daily commute before getting stuck.
 
 [Google Maps API]: https://developers.google.com/maps/
 
 ## Quick how-to
 
 First, you need a free [Google Maps API key][] and access to an SMTP server.
-[Mailgun][] has free plans.
+[Mailgun][] has a free plan.
 
 [Google Maps API key]: https://developers.google.com/maps/documentation/javascript/get-api-key#key
 [Mailgun]: https://www.mailgun.com/
 
-Then, issue once:
+Then install [Go](https://golang.org/), if you haven't, and issue once:
 
     $ git clone https://github.com/agorf/trafficjam.git
     $ cd trafficjam
-    $ bundle install
-    $ cp .env.sample .env
+    $ go build trafficjam.go
+    $ cp config.json.sample config.json
 
-Configure the script with your `$EDITOR`:
+Configure the program with your `$EDITOR`:
 
-    $ $EDITOR .env
+    $ $EDITOR config.json
 
-Run the script:
+Run the program:
 
-    $ bundle exec ruby trafficjam.rb
+    $ ./trafficjam config.json
 
 You can use [Cron][] to run the script at predetermined intervals (e.g. right
-before heading out each morning).
+before heading out each morning). Here's what I have:
+
+    0,5,10,15,20,25,30 9 * * 1-5 agorf ./trafficjam config.json
+
+This runs the program on working days, from 9:00 until 9:30, every five minutes.
+
+To avoid getting spammed, you need to figure out the right threshold
+(`max_duration` config option) that you want to get notified for.
 
 [Cron]: https://en.wikipedia.org/wiki/Cron
 
 ## Configuration
 
-The following environment variables should be defined (all required unless
-otherwise stated):
+The configuration file is a plain JSON file. The following keys can be defined
+(all required unless otherwise stated):
 
-* `ORIGINS` – Your home address
-* `DESTINATIONS` – Your work address
-* `KEY` – Your Google Maps API key
-* `MODE` (optional) – See [here](https://developers.google.com/maps/documentation/distance-matrix/intro#travel_modes)
-* `AVOID` (optional) – See [here](https://developers.google.com/maps/documentation/distance-matrix/intro#Restrictions)
-* `TRAFFIC_MODEL` (optional) – See [here](https://developers.google.com/maps/documentation/distance-matrix/intro#traffic-model)
-* `MAX_DURATION_MINUTES` – If the estimated duration of your commute exceeds
+* `origins` – Your home address
+* `destinations` – Your work address
+* `api_key` – Your Google Maps API key
+* `mode` (optional) – See [here](https://developers.google.com/maps/documentation/distance-matrix/intro#travel_modes)
+* `avoid` (optional) – See [here](https://developers.google.com/maps/documentation/distance-matrix/intro#Restrictions)
+* `traffic_model` (optional) – See [here](https://developers.google.com/maps/documentation/distance-matrix/intro#traffic-model)
+* `max_duration` (minutes) – If the estimated duration of your commute exceeds
   this value in minutes, you will get notified
-* `SMTP_HOST` – SMTP server hostname
-* `SMTP_PORT` – SMTP server port
-* `SMTP_USER` – SMTP server username
-* `SMTP_PASS` – SMTP server password
-* `RECIPIENT` – Email address to get notified at
+* `host` (under `smtp`) – SMTP server hostname
+* `port` (under `smtp`) – SMTP server port
+* `user` (under `smtp`) – SMTP server username
+* `pass` (under `smtp`) – SMTP server password
+* `recipient` – Email address to get notified at
+
+See `config.json.sample` for a sample configuration file.
 
 ## License
 

Gemfile.lock

@@ -0,0 +1,16 @@
+{
+  "origins": "",
+  "destinations": "",
+  "api_key": "",
+  "mode": "",
+  "avoid": "",
+  "traffic_model": "",
+  "max_duration": 0,
+  "smtp": {
+    "host": "",
+    "port": 587,
+    "user": "",
+    "pass": ""
+  },
+  "recipient": ""
+}

LICENSE.txt

@@ -0,0 +1,158 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/smtp"
+	"net/url"
+	"os"
+	"os/user"
+)
+
+const (
+	name   = "trafficjam"
+	apiURL = "https://maps.googleapis.com/maps/api/distancematrix/json"
+)
+
+type config struct {
+	Origins      string `json:"origins"`
+	Destinations string `json:"destinations"`
+	APIKey       string `json:"api_key"`
+	Mode         string `json:"mode"`
+	Avoid        string `json:"avoid"`
+	TrafficModel string `json:"traffic_model"`
+	MaxDuration  int    `json:"max_duration"`
+	SMTP         struct {
+		Host string `json:"host"`
+		Port int    `json:"port"`
+		User string `json:"user"`
+		Pass string `json:"pass"`
+	} `json:"smtp"`
+	Recipient string `json:"recipient"`
+}
+
+type apiResponse struct {
+	Rows []struct {
+		Elements []struct {
+			DurationInTraffic struct {
+				Value int `json:"value"`
+			} `json:"duration_in_traffic"`
+			Status string `json:"status"`
+		} `json:"elements"`
+	} `json:"rows"`
+	Status string `json:"status"`
+}
+
+func main() {
+	conf, err := readConfig(os.Args[1])
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s: %v\n", name, err)
+		os.Exit(1)
+	}
+
+	params := map[string]string{
+		"origins":        conf.Origins,
+		"destinations":   conf.Destinations,
+		"key":            conf.APIKey,
+		"mode":           conf.Mode,
+		"avoid":          conf.Avoid,
+		"departure_time": "now",
+		"traffic_model":  conf.TrafficModel,
+	}
+
+	apiResp, err := queryMapsAPI(params)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s: %v\n", name, err)
+		os.Exit(1)
+	}
+
+	duration := apiResp.Rows[0].Elements[0].DurationInTraffic.Value
+	durationMins := int(float64(duration)/60.0 + 0.5) // round
+
+	if durationMins > conf.MaxDuration {
+		sendMail(conf, fmt.Sprintf("%d minutes", durationMins))
+	}
+}
+
+func readConfig(filename string) (*config, error) {
+	var conf config
+
+	confData, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := json.Unmarshal(confData, &conf); err != nil {
+		return nil, err
+	}
+
+	return &conf, nil
+}
+
+func queryMapsAPI(params map[string]string) (*apiResponse, error) {
+	urlBuf := bytes.NewBufferString(apiURL)
+	urlBuf.WriteByte('?')
+
+	for key, val := range params {
+		urlBuf.WriteString(url.QueryEscape(key))
+		urlBuf.WriteByte('=')
+		urlBuf.WriteString(url.QueryEscape(val))
+		urlBuf.WriteByte('&')
+	}
+
+	resp, err := http.Get(urlBuf.String())
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var apiResp apiResponse
+	if err := json.Unmarshal(body, &apiResp); err != nil {
+		return nil, err
+	}
+
+	if apiResp.Status != "OK" {
+		return nil, fmt.Errorf("%s: bad response status: %s\n", name, apiResp.Status)
+	}
+	if len(apiResp.Rows) != 1 {
+		return nil, fmt.Errorf("%s: response row count is not 1\n", name)
+	}
+	if len(apiResp.Rows[0].Elements) != 1 {
+		return nil, fmt.Errorf("%s: response first row element count is not 1\n", name)
+	}
+	if apiResp.Rows[0].Elements[0].Status != "OK" {
+		return nil, fmt.Errorf("%s: bad response row element status: %s\n", name, apiResp.Rows[0].Elements[0].Status)
+	}
+
+	return &apiResp, nil
+}
+
+func sendMail(conf *config, body string) error {
+	user, err := user.Current()
+	if err != nil {
+		return err
+	}
+
+	hostname, err := os.Hostname()
+	if err != nil {
+		return err
+	}
+
+	auth := smtp.PlainAuth("", conf.SMTP.User, conf.SMTP.Pass, conf.SMTP.Host)
+	sender := user.Username + "@" + hostname
+	to := []string{conf.Recipient}
+	msg := []byte("To: " + conf.Recipient + "\r\n" +
+		"Subject: " + name + " alert\r\n" +
+		"\r\n" +
+		body + "\r\n")
+
+	return smtp.SendMail(fmt.Sprintf("%s:%d", conf.SMTP.Host, conf.SMTP.Port), auth, sender, to, msg)
+}