fix(nightscape): do not fail on empty array

src/segment_nightscout.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"encoding/json"
+	"errors"
 )
 
 // segment struct, makes templating easier
@@ -82,46 +83,59 @@ func (ns *nightscout) string() string {
 }
 
 func (ns *nightscout) getResult() (*NightscoutData, error) {
-	url := ns.props.getString(URL, "")
+	parseSingleElement := func(data []byte) (*NightscoutData, error) {
-	// natural and understood NS timeout is 5, anything else is unusual
+		var result []*NightscoutData
-	cacheTimeout := ns.props.getInt(NSCacheTimeout, 5)
+		err := json.Unmarshal(data, &result)
-	response := &NightscoutData{}
+		if err != nil {
-	if cacheTimeout > 0 {
+			return nil, err
-		// check if data stored in cache
+		}
-		val, found := ns.env.cache().get(url)
+		if len(result) == 0 {
+			return nil, errors.New("no elements in the array")
+		}
+		return result[0], nil
+	}
+	getCacheValue := func(key string) (*NightscoutData, error) {
+		val, found := ns.env.cache().get(key)
 		// we got something from the cache
 		if found {
-			err := json.Unmarshal([]byte(val), response)
+			if data, err := parseSingleElement([]byte(val)); err == nil {
-			if err != nil {
+				return data, nil
-				return nil, err
 			}
-			return response, nil
+		}
+		return nil, errors.New("no data in cache")
+	}
+
+	url := ns.props.getString(URL, "")
+	httpTimeout := ns.props.getInt(HTTPTimeout, DefaultHTTPTimeout)
+	// natural and understood NS timeout is 5, anything else is unusual
+	cacheTimeout := ns.props.getInt(NSCacheTimeout, 5)
+
+	if cacheTimeout > 0 {
+		if data, err := getCacheValue(url); err == nil {
+			return data, nil
 		}
 	}
 
-	httpTimeout := ns.props.getInt(HTTPTimeout, DefaultHTTPTimeout)
-
 	body, err := ns.env.doGet(url, httpTimeout)
 	if err != nil {
-		return &NightscoutData{}, err
+		return nil, err
 	}
 	var arr []*NightscoutData
 	err = json.Unmarshal(body, &arr)
 	if err != nil {
-		return &NightscoutData{}, err
+		return nil, err
 	}
 
-	firstelement := arr[0]
+	data, err := parseSingleElement(body)
-	firstData, err := json.Marshal(firstelement)
 	if err != nil {
-		return &NightscoutData{}, err
+		return nil, err
 	}
 
 	if cacheTimeout > 0 {
 		// persist new sugars in cache
-		ns.env.cache().set(url, string(firstData), cacheTimeout)
+		ns.env.cache().set(url, string(body), cacheTimeout)
 	}
-	return firstelement, nil
+	return data, nil
 }
 
 func (ns *nightscout) init(props *properties, env environmentInfo) {

src/segment_nightscout_test.go

@@ -17,6 +17,8 @@ func TestNSSegment(t *testing.T) {
 		JSONResponse    string
 		ExpectedString  string
 		ExpectedEnabled bool
+		CacheTimeout    int
+		CacheFoundFail  bool
 		Template        string
 		Error           error
 	}{
@@ -82,18 +84,65 @@ func TestNSSegment(t *testing.T) {
 			Error:           errors.New("Something went wrong"),
 			ExpectedEnabled: false,
 		},
+		{
+			Case:            "Empty array",
+			JSONResponse:    "[]",
+			ExpectedEnabled: false,
+		},
+		{
+			Case: "DoubleDown 50 from cache",
+			JSONResponse: `
+			[{"_id":"619d6fa819696e8ded5b2206","sgv":50,"date":1637707537000,"dateString":"2021-11-23T22:45:37.000Z","trend":4,"direction":"DoubleDown","device":"share2","type":"sgv","utcOffset":0,"sysTime":"2021-11-23T22:45:37.000Z","mills":1637707537000}]`, // nolint:lll
+			Template:        " {{.Sgv}}{{.TrendIcon}}",
+			ExpectedString:  " 50↓↓",
+			ExpectedEnabled: true,
+			CacheTimeout:    10,
+		},
+		{
+			Case: "DoubleDown 50 from cache not found",
+			JSONResponse: `
+			[{"_id":"619d6fa819696e8ded5b2206","sgv":50,"date":1637707537000,"dateString":"2021-11-23T22:45:37.000Z","trend":4,"direction":"DoubleDown","device":"share2","type":"sgv","utcOffset":0,"sysTime":"2021-11-23T22:45:37.000Z","mills":1637707537000}]`, // nolint:lll
+			Template:        " {{.Sgv}}{{.TrendIcon}}",
+			ExpectedString:  " 50↓↓",
+			ExpectedEnabled: true,
+			CacheTimeout:    10,
+			CacheFoundFail:  true,
+		},
+		{
+			Case: "Error parsing response",
+			JSONResponse: `
+			4tffgt4e4567`,
+			Template:        " {{.Sgv}}{{.TrendIcon}}",
+			ExpectedString:  " 50↓↓",
+			ExpectedEnabled: false,
+			CacheTimeout:    10,
+		},
+		{
+			Case: "Faulty template",
+			JSONResponse: `
+			[{"sgv":50,"direction":"DoubleDown"}]`,
+			Template:        " {{.Sgv}}{{.Burp}}",
+			ExpectedString:  incorrectTemplate,
+			ExpectedEnabled: true,
+			CacheTimeout:    10,
+		},
 	}
 
 	for _, tc := range cases {
 		env := &MockedEnvironment{}
 		props := &properties{
 			values: map[Property]interface{}{
-				CacheTimeout: 0,
+				CacheTimeout: tc.CacheTimeout,
 				URL:          "FAKE",
 			},
 		}
 
+		cache := &MockedCache{}
+		cache.On("get", NSAPIURL).Return(tc.JSONResponse, !tc.CacheFoundFail)
+		cache.On("set", NSAPIURL, tc.JSONResponse, tc.CacheTimeout).Return()
+
 		env.On("doGet", NSAPIURL).Return([]byte(tc.JSONResponse), tc.Error)
+		env.On("cache", nil).Return(cache)
 
 		if tc.Template != "" {
 			props.values[SegmentTemplate] = tc.Template