package internalhttp

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

	"galaxy/authsession/internal/service/shared"

	"github.com/gin-gonic/gin"
)

const internalErrorCodeContextKey = "internal_error_code"

type malformedJSONRequestError struct {
	message string
}

func (e *malformedJSONRequestError) Error() string {
	if e == nil {
		return ""
	}

	return e.message
}

func decodeJSONRequest(request *http.Request, target any) error {
	if request == nil || request.Body == nil {
		return &malformedJSONRequestError{message: "request body must not be empty"}
	}

	return decodeJSONReader(request.Body, target)
}

func decodeJSONReader(reader io.Reader, target any) error {
	decoder := json.NewDecoder(reader)
	decoder.DisallowUnknownFields()

	if err := decoder.Decode(target); err != nil {
		return describeJSONDecodeError(err)
	}

	if err := decoder.Decode(&struct{}{}); err != nil {
		if errors.Is(err, io.EOF) {
			return nil
		}

		return &malformedJSONRequestError{message: "request body must contain a single JSON object"}
	}

	return &malformedJSONRequestError{message: "request body must contain a single JSON object"}
}

func describeJSONDecodeError(err error) error {
	var syntaxErr *json.SyntaxError
	var typeErr *json.UnmarshalTypeError

	switch {
	case errors.Is(err, io.EOF):
		return &malformedJSONRequestError{message: "request body must not be empty"}
	case errors.As(err, &syntaxErr):
		return &malformedJSONRequestError{message: "request body contains malformed JSON"}
	case errors.Is(err, io.ErrUnexpectedEOF):
		return &malformedJSONRequestError{message: "request body contains malformed JSON"}
	case errors.As(err, &typeErr):
		if strings.TrimSpace(typeErr.Field) != "" {
			return &malformedJSONRequestError{
				message: fmt.Sprintf("request body contains an invalid value for %q", typeErr.Field),
			}
		}

		return &malformedJSONRequestError{message: "request body contains an invalid JSON value"}
	case strings.HasPrefix(err.Error(), "json: unknown field "):
		return &malformedJSONRequestError{
			message: fmt.Sprintf("request body contains unknown field %s", strings.TrimPrefix(err.Error(), "json: unknown field ")),
		}
	default:
		return &malformedJSONRequestError{message: "request body contains invalid JSON"}
	}
}

func abortWithProjection(c *gin.Context, projection shared.InternalErrorProjection) {
	c.Set(internalErrorCodeContextKey, projection.Code)
	c.AbortWithStatusJSON(projection.StatusCode, errorResponse{
		Error: errorBody{
			Code:    projection.Code,
			Message: projection.Message,
		},
	})
}