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// Copyright © 2022 siddharth ravikumar <s@ricketyspace.net>
// SPDX-License-Identifier: ISC
// Functions for accessing the National Weather Service API.
package nws
import (
"encoding/json"
"fmt"
"io"
"time"
"ricketyspace.net/peach/client"
)
type PointLocationProperties struct {
City string
State string
}
type PointLocation struct {
Properties PointLocationProperties
}
type PointProperties struct {
GridId string
GridX int
GridY int
Forecast string
ForecastHourly string
RelativeLocation PointLocation
}
type Point struct {
Properties PointProperties
}
type ForecastPeriod struct {
Number int
Name string
StartTime string
EndTime string
IsDayTime bool
Temperature int
TemperatureUnit string
TemperatureTrend string
WindSpeed string
WindDirection string
ShortForecast string
DetailedForecast string
}
type ForecastProperties struct {
Periods []ForecastPeriod
}
type Forecast struct {
Properties ForecastProperties
}
type Error struct {
Title string
Type string
Status int
Detail string
}
func (e Error) Error() string {
return fmt.Sprintf("%d: %s: %s", e.Status, e.Type, e.Detail)
}
// NWS `/points` endpoint.
//
// TODO: return Error instead of error
func Points(lat, lng float32) (*Point, error) {
url := fmt.Sprintf("https://api.weather.gov/points/%.4f,%.4f", lat, lng)
body, nwsErr := get(url)
if nwsErr != nil {
return nil, fmt.Errorf("points: %v", nwsErr)
}
// Unmarshal.
point := new(Point)
err := json.Unmarshal(body, point)
if err != nil {
return nil, fmt.Errorf("points: decode: %v", err)
}
if point.Properties.Forecast == "" {
return nil, fmt.Errorf("points: forecast empty")
}
if point.Properties.ForecastHourly == "" {
return nil, fmt.Errorf("points: forecasthourly empty")
}
return point, nil
}
// NWS forecast endpoint.
//
// TODO: return Error instead of error.
func GetForecast(point *Point) (*Forecast, error) {
if point == nil {
return nil, fmt.Errorf("forecast: point nil")
}
if len(point.Properties.Forecast) == 0 {
return nil, fmt.Errorf("forecast: link empty")
}
// Get the forecast
body, nwsErr := get(point.Properties.Forecast)
if nwsErr != nil {
return nil, fmt.Errorf("forecast: %v", nwsErr)
}
// Unmarshal.
forecast := new(Forecast)
err := json.Unmarshal(body, forecast)
if err != nil {
return nil, fmt.Errorf("forecast: decode: %v", err)
}
if len(forecast.Properties.Periods) == 0 {
return nil, fmt.Errorf("forecast: periods empty")
}
return forecast, nil
}
// NWS forecast hourly endpoint.
//
// TODO: return Error instead of error
func GetForecastHourly(point *Point) (*Forecast, error) {
if point == nil {
return nil, fmt.Errorf("forecast hourly: point nil")
}
if len(point.Properties.ForecastHourly) == 0 {
return nil, fmt.Errorf("forecast hourly: link empty")
}
// Get the hourly forecast.
body, nwsErr := get(point.Properties.ForecastHourly)
if nwsErr != nil {
return nil, fmt.Errorf("forecast hourly: %v", nwsErr)
}
// Unmarshal.
forecast := new(Forecast)
err := json.Unmarshal(body, forecast)
if err != nil {
return nil, fmt.Errorf("forecast hourly: decode: %v", err)
}
if len(forecast.Properties.Periods) == 0 {
return nil, fmt.Errorf("forecast hourly: periods empty")
}
return forecast, nil
}
// HTTP GET a NWS endpoint.
func get(url string) ([]byte, *Error) {
tries := 5
retryDelay := 100 * time.Millisecond
for {
resp, err := client.Get(url)
if err != nil {
return nil, &Error{
Title: fmt.Sprintf("http get failed: %v", url),
Type: "http-get",
Status: 500,
Detail: err.Error(),
}
}
if tries > 0 && resp.StatusCode != 200 {
tries -= 1
// Wait before re-try.
time.Sleep(retryDelay)
retryDelay *= 2 // Exponential back-off delay.
continue // Re-try
}
// Parse response body.
body, err := io.ReadAll(resp.Body)
if err != nil {
return nil, &Error{
Title: fmt.Sprintf("parsing body: %v", url),
Type: "response-body",
Status: 500,
Detail: err.Error(),
}
}
// Check if the request failed.
if resp.StatusCode != 200 {
nwsErr := Error{}
err := json.Unmarshal(body, &nwsErr)
if err != nil {
return nil, &Error{
Title: fmt.Sprintf("json decode: %v", url),
Type: "json-decode",
Status: 500,
Detail: err.Error(),
}
}
return nil, &nwsErr
}
// Response OK.
return body, nil
}
}
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