package envitron

import (
	"encoding/json"
	"io"

	"github.com/labstack/echo"
)

type jsonError struct {
	Message string `json:"error"`
}

func (e jsonError) Error() string {
	return e.Message
}

type bindError struct {
	Message string `json:"error"`
	Offset  int64  `json:"offset"`
	Field   string `json:"field,omitempty"`
}

func (e bindError) Error() string {
	return e.Message
}

type jsonBinder struct{}

func (b jsonBinder) Bind(i interface{}, c echo.Context) error {
	err := json.NewDecoder(c.Request().Body).Decode(i)
	if err == nil {
		return nil
	}

	switch e := err.(type) {
	case *json.SyntaxError:
		return bindError{Message: `Syntax error`, Offset: e.Offset, Field: ``}
	case *json.UnmarshalTypeError:
		return bindError{Message: `Type error`, Offset: e.Offset, Field: e.Field}
	}

	if err == io.ErrUnexpectedEOF || err == io.EOF {
		return jsonError{`Unexpected EOF`}
	}
	return jsonError{`Unknown error occurred while parsing JSON. ` + err.Error()}
}