From 1992dd31cc7d88fd202a6ee499589632a3e0bda2 Mon Sep 17 00:00:00 2001
From: Erik Winter <ik@erikwinter.nl>
Date: Sat, 16 Dec 2023 12:11:16 +0100
Subject: [PATCH] project start

---
 go.mod             |  3 ++
 handler/handler.go | 28 ++++++++++++++
 handler/server.go  | 91 ++++++++++++++++++++++++++++++++++++++++++++++
 service.go         | 38 +++++++++++++++++++
 4 files changed, 160 insertions(+)
 create mode 100644 go.mod
 create mode 100644 handler/handler.go
 create mode 100644 handler/server.go
 create mode 100644 service.go

diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..9689b18
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module "ewintr.nl/emdb"
+
+go 1.21
diff --git a/handler/handler.go b/handler/handler.go
new file mode 100644
index 0000000..96715dd
--- /dev/null
+++ b/handler/handler.go
@@ -0,0 +1,28 @@
+package handler
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+func Index(w http.ResponseWriter) {
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprint(w, `{"message":"emdb index"}`)
+}
+
+func Error(w http.ResponseWriter, status int, message string, err error) {
+	w.WriteHeader(status)
+
+	var resBody []byte
+	res := struct {
+		Message string `json:"message"`
+		Error   string `json:"error"`
+	}{
+		Message: message,
+		Error:   err.Error(),
+	}
+	resBody, _ = json.Marshal(res)
+
+	fmt.Fprint(w, string(resBody))
+}
diff --git a/handler/server.go b/handler/server.go
new file mode 100644
index 0000000..5a58e7a
--- /dev/null
+++ b/handler/server.go
@@ -0,0 +1,91 @@
+package handler
+
+import (
+	"fmt"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"path"
+	"strings"
+)
+
+type APIIndex map[string]http.Handler
+
+type Server struct {
+	apiKey string
+	apis   map[string]http.Handler
+	logger *slog.Logger
+}
+
+func NewServer(apiKey string, apis map[string]http.Handler, logger *slog.Logger) *Server {
+	return &Server{
+		apiKey: apiKey,
+		apis:   apis,
+		logger: logger,
+	}
+}
+
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	rec := httptest.NewRecorder() // records the response to be able to mix writing headers and content
+
+	// cors
+	w.Header().Add("Access-Control-Allow-Origin", "*")
+	w.Header().Add("Access-Control-Allow-Methods", "GET, POST, PUT, PATCH, DELETE, OPTIONS")
+	w.Header().Add("Access-Control-Allow-Headers", "Content-Type, Authorization")
+	if r.Method == http.MethodOptions {
+		w.WriteHeader(http.StatusOK)
+		returnResponse(w, rec, r, s.logger)
+		return
+	}
+
+	logger := s.logger.With("path", r.URL.Path)
+	w.Header().Add("Content-Type", "application/json")
+
+	// authenticate
+	if key := r.Header.Get("Authorization"); key != s.apiKey {
+		Error(rec, http.StatusUnauthorized, "unauthorized", fmt.Errorf("invalid api key"))
+		logger.Info("unauthorized", "key", key)
+		returnResponse(w, rec, r, logger)
+		return
+	}
+
+	// route to internal
+	head, tail := ShiftPath(r.URL.Path)
+	if len(head) == 0 {
+		Index(rec)
+		returnResponse(w, rec, r, logger)
+		return
+	}
+	api, ok := s.apis[head]
+	if !ok {
+		Error(rec, http.StatusNotFound, "Not found", fmt.Errorf("%s is not a valid path", r.URL.Path))
+		returnResponse(w, rec, r, logger)
+		return
+	}
+
+	r.URL.Path = tail
+	api.ServeHTTP(rec, r)
+	returnResponse(w, rec, r, logger)
+}
+
+func returnResponse(w http.ResponseWriter, rec *httptest.ResponseRecorder, r *http.Request, logger *slog.Logger) {
+	for k, v := range rec.Header() {
+		w.Header()[k] = v
+	}
+	w.WriteHeader(rec.Code)
+	w.Write(rec.Body.Bytes())
+	logger.Info("request served", "method", r.Method, "status", rec.Code)
+}
+
+// ShiftPath splits off the first component of p, which will be cleaned of
+// relative components before processing. head will never contain a slash and
+// tail will always be a rooted path without trailing slash.
+// See https://blog.merovius.de/posts/2017-06-18-how-not-to-use-an-http-router/
+func ShiftPath(p string) (string, string) {
+	p = path.Clean("/" + p)
+	i := strings.Index(p[1:], "/") + 1
+	if i <= 0 {
+		return p[1:], "/"
+	}
+	return p[1:i], p[i:]
+}
diff --git a/service.go b/service.go
new file mode 100644
index 0000000..236a145
--- /dev/null
+++ b/service.go
@@ -0,0 +1,38 @@
+package main
+
+import (
+	"fmt"
+	"log/slog"
+	"net/http"
+	"os"
+	"os/signal"
+	"strconv"
+	"syscall"
+
+	"ewintr.nl/emdb/handler"
+)
+
+func main() {
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
+	port, err := strconv.Atoi(getParam("API_PORT", "8080"))
+	if err != nil {
+		fmt.Printf("invalid port: %s", err.Error())
+		os.Exit(1)
+	}
+	apiKey := getParam("API_KEY", "hoi")
+
+	apis := handler.APIIndex{}
+
+	go http.ListenAndServe(fmt.Sprintf(":%d", port), handler.NewServer(apiKey, apis, logger))
+
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
+	<-c
+}
+
+func getParam(param, def string) string {
+	if val, ok := os.LookupEnv(param); ok {
+		return val
+	}
+	return def
+}