package magic

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

type JsonDecodeError struct {
	inner error
}

func (err JsonDecodeError) Error() string {
	return "failed to decode json: " + err.inner.Error()
}

func (err JsonDecodeError) WriteResponse(rw http.ResponseWriter) {
	rw.WriteHeader(http.StatusBadRequest)
}

type Json[T any] struct {
	Data T
}

func NewJson[T any](data T) Json[T] {
	return Json[T]{
		Data: data,
	}
}

func (data *Json[T]) FromRequest(request *http.Request) error {
	bodyReader := request.Body
	defer bodyReader.Close()

	request.Body = http.NoBody

	if err := json.NewDecoder(bodyReader).Decode(&data.Data); err != nil {
		return JsonDecodeError{inner: err}
	}

	return nil
}

type counter struct {
	counter int64
}

func (c *counter) Write(b []byte) (int, error) {
	n := len(b)
	c.counter += int64(n)

	return n, nil
}

func (container Json[T]) Write(w io.Writer) (int64, error) {
	counter := &counter{}
	err := json.NewEncoder(io.MultiWriter(counter, w)).Encode(container.Data)
	return counter.counter, err
}

func (json Json[T]) WriteResponse(w http.ResponseWriter) {
	json.Write(w)
}