add backend supporting opengraph and comments

backend/server/server.go

@@ -0,0 +1,150 @@
+package server
+
+import (
+	"encoding/json"
+	"fmt"
+	"git.sa.vin/any-remark/backend/datastore"
+	"git.sa.vin/any-remark/backend/types"
+	"github.com/dyatlov/go-opengraph/opengraph"
+	"net/http"
+)
+
+type Server interface {
+	OpenGraphHandler(w http.ResponseWriter, r *http.Request)
+	ShortLinkHandler(w http.ResponseWriter, r *http.Request)
+	ShortenLinkHandler(w http.ResponseWriter, r *http.Request)
+	AddComment(w http.ResponseWriter, r *http.Request)
+	ListComments(w http.ResponseWriter, r *http.Request)
+}
+
+type server struct {
+	mapper datastore.Mapper
+}
+
+func NewServer(mapper datastore.Mapper) Server {
+	// Empty function for NewServer
+	return &server{
+		mapper: mapper,
+	}
+}
+
+func (s *server) OpenGraphHandler(w http.ResponseWriter, r *http.Request) {
+	// get the url from the query string
+	queryParams := r.URL.Query()
+	url := queryParams.Get("url")
+	og := opengraph.NewOpenGraph()
+
+	if url == "" {
+		http.Error(w, "url parameter is required", http.StatusBadRequest)
+		return
+	}
+
+	// check if our db has the url already
+	// get the opengraph data from the db
+	ogString, err := s.mapper.GetOpenGraphData(url)
+	if err != nil || ogString == "" {
+		// if it doesn't, fetch the opengraph data from the url
+
+		// TODO: fetch the url require that it responds with html
+		resp, err := http.Get(url) // TODO: use an external proxy to fetch the url
+		if err != nil {
+			http.Error(w, fmt.Sprintf("error fetching url: %s", err), http.StatusInternalServerError)
+			return
+		}
+		defer resp.Body.Close()
+		err = og.ProcessHTML(resp.Body)
+		if err != nil {
+			// TODO: decide what to do if the given site does not respond with html or doesn't exist etc.
+			http.Error(w, fmt.Sprintf("error processing html: %s", err), http.StatusInternalServerError)
+			return
+		}
+		// save the opengraph data to the db
+		err = s.mapper.SaveOpenGraphData(url, og.String())
+		if err != nil {
+			http.Error(w, fmt.Sprintf("error saving opengraph data: %s", err), http.StatusInternalServerError)
+			return
+		}
+
+		// return the opengraph data
+		w.Header().Set("Content-Type", "application/json")
+		_, err = w.Write([]byte(og.String()))
+		if err != nil {
+			http.Error(w, fmt.Sprintf("error writing opengraph data: %s", err), http.StatusInternalServerError)
+			return
+		}
+		return
+	}
+
+	// return the opengraph data
+	w.Header().Set("Content-Type", "application/json")
+	_, err = w.Write([]byte(ogString))
+	if err != nil {
+		http.Error(w, fmt.Sprintf("error writing opengraph data: %s", err), http.StatusInternalServerError)
+		return
+	}
+}
+
+func (s *server) ShortLinkHandler(w http.ResponseWriter, r *http.Request) {
+	// Empty handler for /x/{id}
+}
+
+func (s *server) ShortenLinkHandler(w http.ResponseWriter, r *http.Request) {
+	// Empty handler for /api/v1/shorten
+}
+
+func (s *server) AddComment(w http.ResponseWriter, r *http.Request) {
+	var req types.AddCommentRequest
+	// unmarshal the request body into the req struct
+	err := json.NewDecoder(r.Body).Decode(&req)
+	if err != nil {
+		http.Error(w, fmt.Sprintf("error decoding request body: %s", err), http.StatusBadRequest)
+		return
+	}
+	err = s.mapper.AddComment(req)
+	if err != nil {
+		http.Error(w, fmt.Sprintf("error adding comment: %s", err), http.StatusInternalServerError)
+		return
+	}
+	w.WriteHeader(http.StatusCreated)
+}
+
+func (s *server) ListComments(w http.ResponseWriter, r *http.Request) {
+	comments, err := s.mapper.GetComments(r.URL.Query().Get("url"))
+	if err != nil {
+		http.Error(w, fmt.Sprintf("error getting comments: %s", err), http.StatusInternalServerError)
+		return
+	}
+
+	// TODO: add pagination
+
+	// return the comments
+	w.Header().Set("Content-Type", "application/json")
+	err = json.NewEncoder(w).Encode(comments)
+	if err != nil {
+		http.Error(w, fmt.Sprintf("error encoding comments: %s", err), http.StatusInternalServerError)
+		return
+	}
+}
+
+// CorsMiddleware is a middleware that allows CORS
+func CorsMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// allow all origins
+		w.Header().Set("Access-Control-Allow-Origin", "*")
+		// allow all headers
+		w.Header().Set("Access-Control-Allow-Headers", "*")
+		// allow all methods
+		w.Header().Set("Access-Control-Allow-Methods", "*")
+		// allow credentials
+		w.Header().Set("Access-Control-Allow-Credentials", "true")
+
+		// handle pre-flight requests
+		if r.Method == http.MethodOptions {
+			w.WriteHeader(http.StatusOK)
+			return
+		}
+
+		// call the next handler
+		next.ServeHTTP(w, r)
+	})
+}