Add handler to auth servic

authentication-service/cmd/api/handlers.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+)
+
+func (app *Config) Authenticate(w http.ResponseWriter, r *http.Request) {
+	var requestPayload struct {
+		Email    string `json:"email"`
+		Password string `json:"password"`
+	}
+
+	err := app.readJSON(w, r, &requestPayload)
+	if err != nil {
+		app.errorJSON(w, err, http.StatusBadRequest)
+		return
+	}
+
+	user, err := app.Models.User.GetByEmail(requestPayload.Email)
+	if err != nil {
+		// user not found
+		app.errorJSON(w, errors.New("invalid credentials"), http.StatusBadRequest)
+		return
+	}
+
+	valid, err := user.PasswordMatches(requestPayload.Password)
+	if err != nil || !valid {
+		app.errorJSON(w, errors.New("invalid credentials"), http.StatusBadRequest)
+		return
+	}
+	payload := jsonResponse{
+		Error:   false,
+		Message: fmt.Sprintf("%s %s is authorized to log in.", user.FirstName, user.LastName),
+		Data:    user,
+	}
+
+	app.writeJSON(w, http.StatusAccepted, payload)
+}

authentication-service/cmd/api/helpers.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+)
+
+type jsonResponse struct {
+	Error   bool   `json:"error"`
+	Message string `json:"message"`
+	Data    any    `json:"data,omitempty"`
+}
+
+func (app *Config) readJSON(w http.ResponseWriter, r *http.Request, data any) error {
+	maxBytes := 1048576 // one megabyte
+
+	r.Body = http.MaxBytesReader(w, r.Body, int64(maxBytes))
+
+	dec := json.NewDecoder(r.Body)
+
+	err := dec.Decode(data)
+	if err != nil {
+		return err
+	}
+
+	err = dec.Decode(&struct{}{})
+	if err != io.EOF {
+		return errors.New("body must have only a single JSON value")
+	}
+
+	return nil
+}
+
+func (app *Config) writeJSON(
+	w http.ResponseWriter,
+	status int,
+	data any,
+	headers ...http.Header,
+) error {
+	out, err := json.Marshal(data)
+	if err != nil {
+		return err
+	}
+
+	if len(headers) > 0 {
+		for key, value := range headers[0] {
+			w.Header()[key] = value
+		}
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_, err = w.Write(out)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (app *Config) errorJSON(w http.ResponseWriter, err error, status ...int) error {
+	statusCode := http.StatusBadRequest
+
+	if len(status) > 0 {
+		statusCode = status[0]
+	}
+
+	var payload jsonResponse
+	payload.Error = true
+	payload.Message = err.Error()
+
+	return app.writeJSON(w, statusCode, payload)
+}

authentication-service/cmd/api/routes.go

@@ -23,5 +23,7 @@ func (app *Config) routes() http.Handler {
 
 	mux.Use(middleware.Heartbeat("/ping"))
 
+	mux.Post("/authenticate", app.Authenticate)
+
 	return mux
 }