feat: Add reverse nominatim

Signed-off-by: Tim Hårek Andreassen <tim@harek.no>

internal/nominatim/nominatim.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"reflect"
 	"strconv"
 )
 
@@ -54,7 +55,44 @@ func (n *Nominatim) Search(q string) (*SearchResults, error) {
 	}
 
 	return &result, nil
+}
 
+func (n *Nominatim) Reverse(lat, lon float64) (*ReverseResult, error) {
+	url := fmt.Sprintf("https://nominatim.openstreetmap.org/reverse?lat=%.16f&lon=%.16f&format=jsonv2", lat, lon)
+
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	req.Header.Set("User-Agent", n.siteName)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("%s", resp.Status)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	result := ReverseResult{}
+	err = json.Unmarshal(body, &result)
+	if err != nil {
+		return nil, err
+	}
+
+	if allFieldsNil(result) {
+		return nil, fmt.Errorf("No result")
+	}
+
+	return &result, nil
 }
 
 type LookupResult struct {
@@ -92,3 +130,39 @@ func (n *Nominatim) Lookup(q string) (*LookupResult, error) {
 		},
 	}, nil
 }
+
+func (n *Nominatim) ReverseLookup(lat, lon float64) (*LookupResult, error) {
+	r, err := n.Reverse(lat, lon)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &LookupResult{
+		Location: *r.Name,
+		Coordinates: Coordinates{
+			Latitude:  lat,
+			Longitude: lon,
+		},
+	}, nil
+}
+
+func allFieldsNil(s interface{}) bool {
+	v := reflect.ValueOf(s)
+
+	// Check if the passed value is a struct
+	if v.Kind() != reflect.Struct {
+		return false
+	}
+
+	// Iterate through all fields in the struct
+	for i := 0; i < v.NumField(); i++ {
+		field := v.Field(i)
+
+		// Check if the field is a pointer and is nil
+		if field.Kind() == reflect.Ptr && !field.IsNil() {
+			return false
+		}
+	}
+	return true
+}

internal/nominatim/nominatim_test.go

@@ -55,3 +55,21 @@ func TestLookup(t *testing.T) {
 	_, err = c.Lookup("")
 	assert.Error(err)
 }
+
+func TestReverse(t *testing.T) {
+	assert := assert.New(t)
+	c, err := New("my siteName")
+	assert.NoError(err)
+
+	r, err := c.Reverse(60.3943055, 5.3259192)
+	assert.NoError(err)
+
+	assert.NotEmpty(r)
+
+	assert.Equal("5.325973", *r.Longitude)
+	assert.Equal("60.394487", *r.Latitude)
+	assert.Equal("", *r.Name)
+
+	_, err = c.Reverse(-10000, -10000)
+	assert.Error(err)
+}

internal/nominatim/types.go

@@ -32,6 +32,7 @@ type SearchResult struct {
 }
 
 type SearchResults = []SearchResult
+type ReverseResult = SearchResult
 
 type Coordinates struct {
 	Latitude  float64 `json:"latitude"`