Add Nominatim queries resolution initial support

internal/geo/location/location.go

@@ -0,0 +1,49 @@
+package location
+
+import "github.com/chubin/wttr.in/internal/config"
+
+type Location struct {
+	Name     string
+	Fullname string `json:"display_name"`
+	Lat      string
+	Lon      string
+}
+
+type Provider interface {
+	Query(location string) (*Location, error)
+}
+
+type Searcher struct {
+	providers []Provider
+}
+
+// NewSearcher returns a new Searcher for the specified config.
+func NewSearcher(config *config.Config) *Searcher {
+	providers := []Provider{}
+	for _, p := range config.Geo.Nominatim {
+		providers = append(providers, NewNominatim(p.Name, p.URL, p.Token))
+	}
+
+	return &Searcher{
+		providers: providers,
+	}
+}
+
+// Search makes queries through all known providers,
+// and returns response, as soon as it is not nil.
+// If all responses were nil, the last response is returned.
+func (s *Searcher) Search(location string) (*Location, error) {
+	var (
+		err    error
+		result *Location
+	)
+
+	for _, p := range s.providers {
+		result, err = p.Query(location)
+		if result != nil && err == nil {
+			return result, nil
+		}
+	}
+
+	return result, err
+}

internal/geo/location/nominatim.go

@@ -0,0 +1,66 @@
+package location
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/url"
+)
+
+type Nominatim struct {
+	name  string
+	url   string
+	token string
+}
+
+func NewNominatim(name, url, token string) *Nominatim {
+	return &Nominatim{
+		name:  name,
+		url:   url,
+		token: token,
+	}
+}
+
+func (n *Nominatim) Query(location string) (*Location, error) {
+	var (
+		result []Location
+
+		errResponse struct {
+			Error string
+		}
+	)
+
+	urlws := fmt.Sprintf(
+		"%s?q=%s&format=json&accept-language=native&limit=1&key=%s",
+		n.url, url.QueryEscape(location), n.token)
+
+	log.Println(urlws)
+	resp, err := http.Get(urlws)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", n.name, err)
+	}
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", n.name, err)
+	}
+
+	err = json.Unmarshal(body, &errResponse)
+	if err == nil && errResponse.Error != "" {
+		return nil, fmt.Errorf("%s: %s", n.name, errResponse.Error)
+	}
+
+	err = json.Unmarshal(body, &result)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", n.name, err)
+	}
+
+	if len(result) != 1 {
+		return nil, fmt.Errorf("%s: invalid response", n.name)
+	}
+
+	return &result[0], nil
+
+}