Merge abstraction branch

Addresses #1

Squashed commit of the following:

commit b13df52ab83e41c611d187de3148d03dd2238ffd
Author: Nick Krichevsky <[email protected]>
Date:   Sun Oct 13 00:04:16 2019 -0400

    Minor linting

commit 473879f6ce280419f3b4afddec3067b7c44b870b
Author: Nick Krichevsky <[email protected]>
Date:   Sun Oct 13 00:01:35 2019 -0400

    Update README

commit 15ec2e0d75b9e022718824060baf5cc708b2285a
Author: Nick Krichevsky <[email protected]>
Date:   Sun Oct 13 00:00:38 2019 -0400

    Add basic config validation

commit dd0b3956acc9c4aebae00fc060ba04132b013323
Author: Nick Krichevsky <[email protected]>
Date:   Sat Oct 12 23:56:30 2019 -0400

    Remove dead config code

commit eaa3ceca090fe390fb1bbfeb425f759fe2b9a5aa
Author: Nick Krichevsky <[email protected]>
Date:   Sat Oct 12 23:48:55 2019 -0400

    Improve logging

commit eb08404044944bd3ab75931efecd4011dbc02daa
Author: Nick Krichevsky <[email protected]>
Date:   Sat Oct 12 23:35:56 2019 -0400

    Re-add ability to write to log file

commit e88514c19afcd741b488f7ce18ce01e6c3f57211
Author: Nick Krichevsky <[email protected]>
Date:   Sat Oct 12 23:24:09 2019 -0400

    Move main into cmd package, refactor to use new interface

commit 5bcd98a46a193071aab7236c8b0207af78870bfa
Author: Nick Krichevsky <[email protected]>
Date:   Sat Oct 12 23:09:31 2019 -0400

    Add ability to set ttl of records

commit 8f1dadb8b08a5c09fdfb5d3a88f7e9e976edb8ae
Author: Nick Krichevsky <[email protected]>
Date:   Sat Oct 12 23:05:08 2019 -0400

    Add IPSetter for DO

commit 923d3f5e29d220d5d2c7004dbf8bce5d2d35096d
Author: Nick Krichevsky <[email protected]>
Date:   Sat Oct 12 21:54:25 2019 -0400

    Add abstraction for setting IP addresses

README.md

@@ -1,5 +1,5 @@
 # Pinamic DNS
-Dynamic DNS for your Raspberry Pi (though it doesn't have to be!). Running the binary updates a DNS record on DigitalOcean. 
+Dynamic DNS for your Raspberry Pi (though it doesn't have to be!). Running the binary updates a DNS record on DigitalOcean.
 
 ## Installation
 Run the binary (whether in a shell or a cron job) in the same directory as a `config.json`. The `config.json` must contain the following values.
@@ -21,4 +21,3 @@ Run the binary (whether in a shell or a cron job) in the same directory as a `co
 |-------------|---------------------------------------------------------------------|
 |--config, -c |Set a path to a `config.json`, if not `./config.json`                |
 |--logfile, -l|Redirect output to a logfile                                         |
-|--silent     |Disable all output to stdout. Errors will still be reported to stderr|

cmd/config.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"os"
+
+	"golang.org/x/oauth2"
+)
+
+const defaultConfigPath = "./config.json"
+
+// Config holds the configuration for the application
+// Implements oauth2.TokenSource
+type Config struct {
+	AccessToken string    `json:"access_token"`
+	DNSConfig   DNSConfig `json:"dns_config"`
+}
+
+// DNSConfig represents the config of the DNS records that will be updated.
+type DNSConfig struct {
+	Domain string `json:"domain"`
+	Name   string `json:"name"`
+	TTL    int    `json:"ttl"`
+}
+
+// NewConfig reads the file located at filepath and returns a new Config
+func NewConfig(filepath string) (Config, error) {
+	configReader, err := os.Open(filepath)
+	if err != nil {
+		return Config{}, err
+	}
+
+	defer configReader.Close()
+
+	configDecoder := json.NewDecoder(configReader)
+	var config Config
+	err = configDecoder.Decode(&config)
+	if err != nil {
+		return Config{}, err
+	}
+
+	return config, config.validate()
+}
+
+// validate returns an error if the config is invalid.
+func (config Config) validate() error {
+	if config.AccessToken == "" {
+		return errors.New("access token must be specified in config")
+	} else if config.DNSConfig.Domain == "" {
+		return errors.New("domain must be specified in config")
+	} else if config.DNSConfig.Name == "" {
+		return errors.New("name must be specified in config")
+	} else if config.DNSConfig.TTL == 0 {
+		return errors.New("ttl must be specified in config")
+	}
+
+	return nil
+}
+
+// Token returns a new oauth2.token object.
+// Required for config to implement oauth2.TokenSource
+func (config Config) Token() (*oauth2.Token, error) {
+	return &oauth2.Token{
+		AccessToken: config.AccessToken,
+	}, nil
+}

cmd/main.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"io/ioutil"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"strings"
+
+	"github.com/ogier/pflag"
+	pinamicdns "github.com/ollien/pinamic-dns"
+	"github.com/ollien/xtrace"
+)
+
+//DNSStatusCode represents the result of what CreateOrUpdateRecord did.
+type DNSStatusCode int
+
+//DNSResult represents the result of running CreateOrUpdateRecord, including information of its run.
+type DNSResult struct {
+	IP         string
+	StatusCode DNSStatusCode
+}
+
+//Possible results for DNSResult
+const (
+	StatusIPSet DNSStatusCode = iota
+	StatusIPUpdated
+	StatusIPAlreadySet
+)
+
+func getIP() (net.IP, error) {
+	res, err := http.Get("http://checkip.amazonaws.com/")
+
+	if err != nil {
+		return nil, err
+	}
+
+	defer res.Body.Close()
+	resData, err := ioutil.ReadAll(res.Body)
+
+	if err != nil {
+		return nil, err
+	}
+
+	rawIP := strings.Trim(string(resData), "\n")
+
+	return net.ParseIP(rawIP), nil
+}
+
+func main() {
+	configPath := ""
+	logFilePath := ""
+	pflag.StringVarP(&configPath, "config", "c", defaultConfigPath, "Set a path to a config.json")
+	pflag.StringVarP(&logFilePath, "logfile", "l", "", "Redirect output to a log file.")
+	pflag.Parse()
+
+	logWriter := os.Stderr
+	if logFilePath != "" {
+		logFile, err := os.OpenFile(logFilePath, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0644)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		defer logFile.Close()
+		logWriter = logFile
+	}
+	logger := log.New(logWriter, "", log.LstdFlags)
+
+	config, err := NewConfig(configPath)
+	if err != nil {
+		logger.Fatal(err)
+	}
+
+	var setter pinamicdns.IPSetter
+	setter, err = pinamicdns.NewDigitalOceanIPSetter(config, pinamicdns.DigitalOceanRecordTTL(config.DNSConfig.TTL))
+	ip, err := getIP()
+	if err != nil {
+		logger.Fatalf("Could not get IP to update with: %s", err)
+	}
+
+	err = setter.SetIP(config.DNSConfig.Domain, config.DNSConfig.Name, ip)
+	if err != nil {
+		logger.Printf("Could not update record: %s", err)
+		tracer, tracerErr := xtrace.NewTracer(err)
+		if tracerErr != nil {
+			logger.Fatalf("Could not produce error trace: %s", err)
+		}
+
+		traceErr := tracer.Trace(logWriter)
+		if traceErr != nil {
+			logger.Fatalf("Could not produce error trace: %s", err)
+		}
+		// HACK: Write a newline so there's one after the trace
+		// Should probably be done in xtrace
+		logWriter.Write([]byte("\n"))
+
+		os.Exit(1)
+	}
+}