add configurable timezone

- For some reason, the SmartHub API decided to return "unix timestamps", but in the utility's timezone instead of in UTC, which would be the normal choice for an API.
- My utility returned timestamps in the EST timezone, but other users have reported their local timezones are used as well.

README.md

@@ -22,6 +22,9 @@ Download [config.example.yaml](config.example.yaml) and fill in your own values.
   - Navigate to Usage Explorer (example: https://novec.smarthub.coop/ui/#/usageExplorer)
   - Find a call to `services/secured/utility-usage/poll` in the Network tab
   - Open the call, and copy the `serviceLocationNumber` field from the Payload tab.
+- `timezone` needs to be set to the timezone used by your utility. For some reason,
+  the SmartHub API decided to return unix timestamps, but in the utility's timezone
+  instead of in UTC, which would be the normal choice for an API.
 - `influxdb.insecure` allows connecting to a server with certificate issues.
 - The other fields should be fairly self-explanatory.
 

config.example.yaml

@@ -5,6 +5,7 @@ smarthub:
   password: smarthub_password
   account: 1234567001
   service_location: 123456
+  timezone: America/New_York
 influxdb:
   host: https://localhost:8428
   auth_token: johndoe:influx_password

internal/app/main.go

@@ -29,6 +29,7 @@ type SmartHubConfig struct {
 	Password        string `yaml:"password"`
 	Account         string `yaml:"account"`
 	ServiceLocation string `yaml:"service_location"`
+	Timezone        string `yaml:"timezone"`
 }
 
 // Config is the config format for electric-usage-downloader
@@ -105,7 +106,7 @@ func Main() error {
 			if err != nil {
 				return nil, err
 			}
-			records, err := ParseReader(r)
+			records, err := ParseReader(r, config.SmartHub.Timezone)
 			if err != nil {
 				return nil, err
 			}

internal/app/parser.go

@@ -68,7 +68,7 @@ func (t *RetryableError) Error() string {
 
 // ParseReader parses the json response received in FetchData from the SmartHub poll api.
 // It can return a normal error, a RetryableError, or parsed ElectricUsage.
-func ParseReader(readCloser io.ReadCloser) ([]ElectricUsage, error) {
+func ParseReader(readCloser io.ReadCloser, timezone string) ([]ElectricUsage, error) {
 	defer func() {
 		if err := readCloser.Close(); err != nil {
 			fmt.Println("Error: failed to close response body")
@@ -107,10 +107,10 @@ func ParseReader(readCloser io.ReadCloser) ([]ElectricUsage, error) {
 		}
 	}
 	// this is dumb, but the SmartHub api returns "unix timestamps"
-	// that are based on EST (which is incorrect), at least as of 2/29/2024.
+	// that are based on the utility timezone (which is incorrect), at least as of 2/29/2024.
 	// Example: For Midnight, Jan 1, 1970, EST, this api would return "0"
 	//          However, the correct value (UTC) would be "18000".
-	zone, err := time.LoadLocation("America/New_York")
+	zone, err := time.LoadLocation(timezone)
 	if err != nil {
 		return nil, err
 	}