URL shortening service (#104)

* URL shortening service

* Url shortener -> url

* Readme edit

url/handler/url.go

@@ -0,0 +1,93 @@
+package handler
+
+import (
+	"context"
+	"errors"
+	"strings"
+
+	"github.com/micro/micro/v3/service/config"
+	"github.com/micro/micro/v3/service/model"
+	"github.com/teris-io/shortid"
+
+	"github.com/micro/services/pkg/tenant"
+	url "github.com/micro/services/url/proto"
+)
+
+const hostPrefix = "https://m3o.one/u"
+
+type Url struct {
+	pairs      model.Model
+	ownerIndex model.Index
+	hostPrefix string
+}
+
+func NewUrl() *Url {
+	var hp string
+	cfg, err := config.Get("micro.url_shortener.host_prefix")
+	if err != nil {
+		hp = cfg.String(hostPrefix)
+	}
+	if len(strings.TrimSpace(hp)) == 0 {
+		hp = hostPrefix
+	}
+
+	ownerIndex := model.ByEquality("Owner")
+	ownerIndex.Order.Type = model.OrderTypeUnordered
+
+	return &Url{
+		pairs: model.NewModel(
+			model.WithKey("ShortURL"),
+			model.WithIndexes(ownerIndex),
+		),
+		ownerIndex: ownerIndex,
+	}
+}
+
+func (e *Url) Shorten(ctx context.Context, req *url.ShortenRequest, rsp *url.ShortenResponse) error {
+	tenantID, ok := tenant.FromContext(ctx)
+	if !ok {
+		return errors.New("Not authorized")
+	}
+	sid, err := shortid.New(1, shortid.DefaultABC, 2342)
+	if err != nil {
+		return err
+	}
+
+	id, err := sid.Generate()
+	if err != nil {
+		return err
+	}
+	return e.pairs.Create(&url.URLPair{
+		DestinationURL: req.DestinationURL,
+		ShortURL:       id,
+		Owner:          tenantID,
+	})
+}
+
+func (e *Url) List(ctx context.Context, req *url.ListRequest, rsp *url.ListResponse) error {
+	tenantID, ok := tenant.FromContext(ctx)
+	if !ok {
+		return errors.New("Not authorized")
+	}
+
+	rsp.UrlPairs = []*url.URLPair{}
+	err := e.pairs.Read(e.ownerIndex.ToQuery(e.ownerIndex.ToQuery(tenantID)), &rsp.UrlPairs)
+	if err != nil {
+		return err
+	}
+	for _, v := range rsp.UrlPairs {
+		v.ShortURL = e.hostPrefix + "/" + v.ShortURL
+	}
+	return nil
+}
+
+func (e *Url) Proxy(ctx context.Context, req *url.ProxyRequest, rsp *url.ProxyResponse) error {
+	var pair url.URLPair
+	err := e.pairs.Read(e.ownerIndex.ToQuery(model.QueryEquals("ShortURL", e.hostPrefix+"/"+req.ShortURL)), pair)
+	if err != nil {
+		return err
+	}
+
+	rsp.DestinationURL = pair.DestinationURL
+	return nil
+}