udemy-go-web-2/cmd/api/helpers.go

package main

import (
	"encoding/json"
	"errors"
	"io"
	"net/http"

	"golang.org/x/crypto/bcrypt"
)

func (app *application) readJSON(w http.ResponseWriter, r *http.Request, data interface{}) error {
	maxBytes := 1048576

	r.Body = http.MaxBytesReader(w, r.Body, int64(maxBytes))

	dec := json.NewDecoder(r.Body)
	err := dec.Decode(data)
	if err != nil {
		return err
	}

	// Make sure there is only one entry.
	err = dec.Decode(&struct{}{})
	if err != io.EOF {
		return errors.New("body must only have a single JSON value")
	}

	return nil
}

// writeJSON writes arbitrary data out as JSON
func (app *application) writeJSON(
	w http.ResponseWriter,
	status int, data interface{},
	headers ...http.Header,
) error {
	out, err := json.MarshalIndent(data, "", "\t")
	if err != nil {
		return err
	}

	if len(headers) > 0 {
		for k, v := range headers[0] {
			w.Header()[k] = v
		}
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	w.Write(out)
	return nil
}

func (app *application) badRequest(w http.ResponseWriter, r *http.Request, err error) error {
	var payload JSONResponse

	payload.OK = false
	payload.Message = err.Error()

	out, err := json.MarshalIndent(payload, "", "\t")
	if err != nil {
		return err
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusBadGateway)
	w.Write(out)
	return nil
}

func (app *application) invalidCredentials(w http.ResponseWriter) error {
	var payload JSONResponse
	payload.OK = false
	payload.Message = "invalid authentication credentials"

	err := app.writeJSON(w, http.StatusUnauthorized, payload)
	if err != nil {
		return err
	}
	return nil
}

func (app *application) passwordMatches(hash, password string) (bool, error) {
	app.errorLog.Println(hash, password)
	err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
	if err != nil {
		switch {
		case errors.Is(err, bcrypt.ErrMismatchedHashAndPassword):
			return false, nil
		default:
			return false, err
		}
	}

	return true, nil
}