// Package response provides the unified response envelope {code, message, data}
// returned by every endpoint of this service.
package response

import (
	"context"
	"errors"
	"net/http"
	"strings"

	"udeServer/internal/apierr"

	"github.com/zeromicro/go-zero/rest/httpx"
)

// Business codes carried in the unified response body.
const (
	CodeOK          = 100000
	CodeBadRequest  = 100001
	CodeNotFound    = 100002
	CodeServerError = 100003
)

// MsgOK is the message of every successful response.
const MsgOK = "操作成功"

// Body is the unified response envelope.
type Body struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
	Data    any    `json:"data"`
}

// OK builds a successful response body.
func OK(data any) Body {
	return Body{Code: CodeOK, Message: MsgOK, Data: data}
}

// Register installs the global success and error handlers on the framework,
// so every endpoint response is wrapped in the unified envelope:
//   - success: HTTP 200 + {"code":100000,...,"data":<resp>}
//   - failure: HTTP 200 + {"code":100xxx,...,"data":null}
func Register() {
	httpx.SetOkHandler(func(_ context.Context, data any) any {
		return OK(data)
	})

	// HTTP status is always 200; the client decides by body code only.
	httpx.SetErrorHandler(func(err error) (int, any) {
		return http.StatusOK, Body{
			Code:    Code(err),
			Message: err.Error(),
			Data:    nil,
		}
	})
}

// Code maps an error to its business code. Errors without an HTTP-aware
// status, e.g. failures from the framework request parser, fall back to
// CodeServerError unless they describe a missing/unset field.
func Code(err error) int {
	var apiErr *apierr.Error
	if errors.As(err, &apiErr) {
		return statusToCode(apiErr.Status)
	}

	// The request parser reports missing required fields as a plain error
	// like `field "name" is not set` (core/mapping/unmarshaler.go), which is
	// a client-side problem rather than a server error.
	if strings.HasSuffix(err.Error(), " is not set") {
		return CodeBadRequest
	}

	return CodeServerError
}

// statusToCode maps the HTTP-aware status of apierr.Error to the body code.
func statusToCode(status int) int {
	switch status {
	case http.StatusBadRequest:
		return CodeBadRequest
	case http.StatusNotFound:
		return CodeNotFound
	default:
		return CodeServerError
	}
}