add nws package

2 files changed, 98 insertions, 0 deletions

diff --git a/nws/nws.go b/nws/nws.go
new file mode 100644
index 0000000..02b4d75
--- /dev/null
+++ b/nws/nws.go
@@ -0,0 +1,72 @@
+// Copyright © 2022 siddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+// Functions for accessing the National Weather Service API.
+package nws
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+
+	"ricketyspace.net/peach/client"
+)
+
+type NWSPointProperties struct {
+	ForecastLink       string `json:"forecast"`
+	ForecastHourlyLink string `json:"forecastHourly"`
+}
+
+type NWSPoints struct {
+	Properties NWSPointProperties
+}
+
+type NWSPointsError struct {
+	Title  string
+	Type   string
+	Status int
+	Detail string
+}
+
+func (e NWSPointsError) Error() string {
+	return fmt.Sprintf("%d: %s: %s", e.Status, e.Type, e.Detail)
+}
+
+// NWS API's `/points` endpoint.
+func points(lat, lng float32) (*NWSPoints, error) {
+	url := fmt.Sprintf("https://api.weather.gov/points/%.4f,%.4f", lat, lng)
+	resp, err := client.Get(url)
+	if err != nil {
+		return nil, fmt.Errorf("points: http get: %v", err)
+	}
+
+	// Parse response body.
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("getting points: body: %v", err)
+	}
+
+	// Check if the request failed.
+	if resp.StatusCode != 200 {
+		perr := new(NWSPointsError)
+		err := json.Unmarshal(body, perr)
+		if err != nil {
+			return nil, fmt.Errorf("points: json: %v", err)
+		}
+		return nil, fmt.Errorf("points: %v", perr)
+	}
+
+	// Unmarshal.
+	points := new(NWSPoints)
+	err = json.Unmarshal(body, points)
+	if err != nil {
+		return nil, fmt.Errorf("getting points: json decode: %v", err)
+	}
+	if points.Properties.ForecastLink == "" {
+		return nil, fmt.Errorf("points: json: %v", err)
+	}
+	if points.Properties.ForecastHourlyLink == "" {
+		return nil, fmt.Errorf("points: json: %v", err)
+	}
+	return points, nil
+}
diff --git a/nws/nws_test.go b/nws/nws_test.go
new file mode 100644
index 0000000..8c52c25
--- /dev/null
+++ b/nws/nws_test.go
@@ -0,0 +1,26 @@
+// Copyright © 2022 siddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package nws
+
+import "testing"
+
+func TestPoints(t *testing.T) {
+	// Test valid lat,lng.
+	np, err := points(41.115, -83.177)
+	if err != nil {
+		t.Errorf("points: %v", err)
+	}
+	if np.Properties.ForecastLink != "https://api.weather.gov/gridpoints/CLE/33,42/forecast" {
+		t.Errorf("points: forcecast link: '%v'", np.Properties.ForecastLink)
+	}
+	if np.Properties.ForecastHourlyLink != "https://api.weather.gov/gridpoints/CLE/33,42/forecast/hourly" {
+		t.Errorf("points: forcecast link: '%v'", np.Properties.ForecastHourlyLink)
+	}
+
+	// Test invalid lat,lng
+	np, err = points(115.0, -83.177)
+	if err == nil {
+		t.Errorf("points: %v", np)
+	}
+}