kong/decode/json.go

/*
------------------------------------------------------------------------------------------------------------------------
####### kong ####### Copyright (c) 2021-2022 losyme ################################################ MIT License #######
------------------------------------------------------------------------------------------------------------------------
*/

package decode

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"mime"
	"net/http"
	"strings"

	"forge.chapril.org/losyme/kong/context"
)

const _jsonMediaType = "application/json"

func JSON(c *context.Context, maxBodySize int64, v interface{}) error {
	ct := c.Request.Header.Get("Content-Type")
	if ct == "" {
		return c.NewError(http.StatusUnsupportedMediaType, "header content type cannot be empty") //////////////////////
	}

	mt, _, err := mime.ParseMediaType(ct)
	if err != nil || mt != _jsonMediaType {
		return c.NewError( /////////////////////////////////////////////////////////////////////////////////////////////
			http.StatusUnsupportedMediaType,
			fmt.Sprintf("header content type must be %s not %s", _jsonMediaType, ct),
		)
	}

	decoder := json.NewDecoder(http.MaxBytesReader(c.Response, c.Request.Body, maxBodySize))
	decoder.DisallowUnknownFields()

	if err := decoder.Decode(v); err != nil {
		var (
			jse  *json.SyntaxError
			jute *json.UnmarshalTypeError
		)

		switch {
		case errors.As(err, &jse):
			return c.NewError( /////////////////////////////////////////////////////////////////////////////////////////
				http.StatusBadRequest,
				fmt.Sprintf("request body contains badly-formed JSON (at position %d)", jse.Offset),
			)

		case errors.Is(err, io.ErrUnexpectedEOF):
			return c.NewError(http.StatusBadRequest, "request body contains badly-formed JSON") ////////////////////////

		case errors.As(err, &jute):
			return c.NewError( /////////////////////////////////////////////////////////////////////////////////////////
				http.StatusBadRequest,
				fmt.Sprintf(
					"request body contains an invalid value for the %q field (at position %d)",
					jute.Field,
					jute.Offset,
				),
			)

		case strings.HasPrefix(err.Error(), "json: unknown field"):
			return c.NewError( /////////////////////////////////////////////////////////////////////////////////////////
				http.StatusBadRequest,
				fmt.Sprintf(
					"request body contains unknown field %s",
					strings.TrimPrefix(err.Error(), "json: unknown field "),
				),
			)

		case errors.Is(err, io.EOF):
			return c.NewError(http.StatusBadRequest, "request body must not be empty") /////////////////////////////////

		case err.Error() == "http: request body too large":
			return c.NewError( /////////////////////////////////////////////////////////////////////////////////////////
				http.StatusRequestEntityTooLarge,
				fmt.Sprintf("request body must not be larger than %d bytes", maxBodySize),
			)

		default:
			return err
		}
	}

	if err := decoder.Decode(&struct{}{}); err != io.EOF {
		return c.NewError( /////////////////////////////////////////////////////////////////////////////////////////////
			http.StatusBadRequest,
			"request body must only contain a single JSON object",
		)
	}

	return nil
}

/*
######################################################################################################## @(°_°)@ #######
*/