From 2081e91caefda0c5dd92069401eee4ffc2e075dd Mon Sep 17 00:00:00 2001
From: siddharth ravikumar <s@ricketyspace.net>
Date: Sun, 5 Jun 2022 14:47:11 -0400
Subject: nws: add get

A thin HTTP GET wrapper for hitting NWS API endpoints.
---
 nws/nws.go      | 55 ++++++++++++++++++++++++++++++++++
 nws/nws_test.go | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 146 insertions(+), 1 deletion(-)

diff --git a/nws/nws.go b/nws/nws.go
index 8c28f19..2fc5662 100644
--- a/nws/nws.go
+++ b/nws/nws.go
@@ -8,6 +8,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"time"
 
 	"ricketyspace.net/peach/client"
 )
@@ -198,3 +199,57 @@ func GetForecastHourly(point *Point) (*Forecast, error) {
 	}
 	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
+	}
+}
diff --git a/nws/nws_test.go b/nws/nws_test.go
index ffa05c8..bac3d83 100644
--- a/nws/nws_test.go
+++ b/nws/nws_test.go
@@ -3,7 +3,13 @@
 
 package nws
 
-import "testing"
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
 
 func TestPoints(t *testing.T) {
 	// Test valid lat,lng.
@@ -142,3 +148,87 @@ func TestGetForecastHourly(t *testing.T) {
 		}
 	}
 }
+
+func TestNWSGetWrapper(t *testing.T) {
+	// Initialize test NWS server.
+	fails := 0
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if fails > 0 {
+			fails -= 1
+			http.Error(w, `{"type":"urn:noaa:nws:api:UnexpectedProblem","title":"Unexpected Problem","status":500,"detail":"An unexpected problem has occurred.","instance":"urn:noaa:nws:api:request:493c3a1d-f87e-407f-ae2c-24483f5aab63","correlationId":"493c3a1d-f87e-407f-ae2c-24483f5aab63","additionalProp1":{}}`, 500)
+			return
+		}
+		// Success.
+		fmt.Fprintln(w, `{"@context":[],"properties":{"gridId":"CLE","gridX":82,"gridY":64,"forecast":"https://api.weather.gov/gridpoints/CLE/82,64/forecast","forecastHourly":"https://api.weather.gov/gridpoints/CLE/82,64/forecast/hourly","relativeLocation":{"properties":{"city":"Cleveland","state":"OH"}}}}`)
+	}))
+	defer ts.Close()
+
+	// Test 1 - Server fails 5 times.
+	fails = 5
+	_, err := get(ts.URL)
+	if err != nil {
+		t.Errorf("get failed: %v", err)
+		return
+	}
+
+	// Test 2 - Server fails 6 times.
+	fails = 6
+	respBody, err := get(ts.URL)
+	if err == nil {
+		t.Errorf("get did not fail: %s", respBody)
+		return
+	}
+	if err != nil && respBody != nil {
+		t.Errorf("body is not nil: %s", respBody)
+	}
+	if err.Title != "Unexpected Problem" {
+		t.Errorf("err title: %s", err.Title)
+		return
+	}
+	if err.Type != "urn:noaa:nws:api:UnexpectedProblem" {
+		t.Errorf("err type: %s", err.Type)
+		return
+	}
+	if err.Status != 500 {
+		t.Errorf("err status: %d", err.Status)
+		return
+	}
+	if err.Detail != "An unexpected problem has occurred." {
+		t.Errorf("err detail: %s", err.Detail)
+		return
+	}
+
+	// Test 3 - Server fails 1 time.
+	fails = 1
+	respBody, err = get(ts.URL)
+	if err != nil {
+		t.Errorf("get failed: %v", err)
+		return
+	}
+	if respBody == nil {
+		t.Errorf("body: %s", respBody)
+		return
+	}
+	point := new(Point)
+	jerr := json.Unmarshal(respBody, point)
+	if jerr != nil {
+		t.Errorf("points: decode: %v", jerr)
+		return
+	}
+	if point.Properties.Forecast == "" {
+		t.Errorf("points: forecast empty")
+		return
+	}
+	if point.Properties.ForecastHourly == "" {
+		t.Errorf("points: forecasthourly empty")
+		return
+	}
+	if point.Properties.RelativeLocation.Properties.City == "" {
+		t.Errorf("points: city empty")
+		return
+	}
+	if point.Properties.RelativeLocation.Properties.State == "" {
+		t.Errorf("points: state empty")
+		return
+	}
+}
-- 
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