feat: go greenlight api wip

2026-03-11 15:50:38 +01:00
parent 2ce943f94e
commit abf2db2798
19 changed files with 469 additions and 0 deletions
@@ -0,0 +1,104 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"maps"
+	"net/http"
+	"strconv"
+
+	"github.com/julienschmidt/httprouter"
+)
+
+// Define an envelope type.
+type envelope map[string]any
+
+// Retrieve the "id" URL parameter from the current request context, then convert it to
+// an integer and return it. If the operation isn't successful, return 0 and an error.
+func (app *application) readIDParam(r *http.Request) (int64, error) {
+	params := httprouter.ParamsFromContext(r.Context())
+
+	id, err := strconv.ParseInt(params.ByName("id"), 10, 64)
+	if err != nil || id < 1 {
+		return 0, errors.New("invalid id parameter")
+	}
+
+	return id, nil
+}
+
+// Change the data parameter to have the type envelope instead of interface{}.
+func (app *application) writeJSON(w http.ResponseWriter, status int, data envelope, headers http.Header) error {
+	js, err := json.MarshalIndent(data, "", "\t")
+	if err != nil {
+		return err
+	}
+
+	js = append(js, '\n')
+
+	maps.Copy(w.Header(), headers)
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	w.Write(js)
+
+	return nil
+}
+
+func (app *application) readJSON(w http.ResponseWriter, r *http.Request, dst interface{}) error {
+	// Decode the request body into the target destination.
+	err := json.NewDecoder(r.Body).Decode(dst)
+	if err != nil {
+		// If there is an error during decoding, start the triage...
+		var syntaxError *json.SyntaxError
+		var unmarshalTypeError *json.UnmarshalTypeError
+		var invalidUnmarshalError *json.InvalidUnmarshalError
+
+		switch {
+		// Use the errors.As() function to check whether the error has the type
+
+		// *json.SyntaxError. If it does, then return a plain-english error message
+		// which includes the location of the problem.
+		case errors.As(err, &syntaxError):
+			return fmt.Errorf("body contains badly-formed JSON (at character %d)", syntaxError.Offset)
+
+		// In some circumstances Decode() may also return an io.ErrUnexpectedEOF error
+		// for syntax errors in the JSON. So we check for this using errors.Is() and
+		// return a generic error message. There is an open issue regarding this at
+		// https://github.com/golang/go/issues/25956.
+		case errors.Is(err, io.ErrUnexpectedEOF):
+			return errors.New("body contains badly-formed JSON")
+
+		// Likewise, catch any *json.UnmarshalTypeError errors. These occur when the
+		// JSON value is the wrong type for the target destination. If the error relates
+		// to a specific field, then we include that in our error message to make it
+		// easier for the client to debug.
+		case errors.As(err, &unmarshalTypeError):
+			if unmarshalTypeError.Field != "" {
+				return fmt.Errorf("body contains incorrect JSON type for field %q", unmarshalTypeError.Field)
+			}
+			return fmt.Errorf("body contains incorrect JSON type (at character %d)", unmarshalTypeError.Offset)
+
+		// An io.EOF error will be returned by Decode() if the request body is empty. We
+		// check for this with errors.Is() and return a plain-english error message
+		// instead.
+		case errors.Is(err, io.EOF):
+			return errors.New("body must not be empty")
+
+		// A json.InvalidUnmarshalError error will be returned if we pass a non-nil
+		// pointer to Decode(). We catch this and panic, rather than returning an error
+		// to our handler. At the end of this chapter we'll talk about panicking
+		// versus returning errors, and discuss why it's an appropriate thing to do in
+		// this specific situation.
+		case errors.As(err, &invalidUnmarshalError):
+			panic(err)
+
+		// For anything else, return the error message as-is.
+		default:
+			return err
+		}
+	}
+
+	return nil
+}