package handler

import (
	"net/http"

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

// Response is the unified response structure.
type Response struct {
	Code    int         `json:"code"`
	Message string      `json:"message"`
	Data    interface{} `json:"data"`
}

// PageResponse wraps paginated results.
type PageResponse struct {
	Items    interface{} `json:"items"`
	Total    int64       `json:"total"`
	Page     int         `json:"page"`
	PageSize int         `json:"page_size"`
}

// OK sends a 200 response with data.
func OK(c *gin.Context, data interface{}) {
	c.JSON(http.StatusOK, Response{
		Code:    0,
		Message: "ok",
		Data:    data,
	})
}

// Fail sends an error response.
func Fail(c *gin.Context, code int, msg string) {
	httpStatus := http.StatusBadRequest
	switch code {
	case 401:
		httpStatus = http.StatusUnauthorized
	case 403:
		httpStatus = http.StatusForbidden
	case 404:
		httpStatus = http.StatusNotFound
	case 409:
		httpStatus = http.StatusConflict
	case 429:
		httpStatus = http.StatusTooManyRequests
	case 500:
		httpStatus = http.StatusInternalServerError
	case 501:
		httpStatus = http.StatusNotImplemented
	}
	c.JSON(httpStatus, Response{
		Code:    code,
		Message: msg,
		Data:    nil,
	})
}

// PageOK sends a paginated 200 response.
func PageOK(c *gin.Context, items interface{}, total int64, page, pageSize int) {
	c.JSON(http.StatusOK, Response{
		Code:    0,
		Message: "ok",
		Data: PageResponse{
			Items:    items,
			Total:    total,
			Page:     page,
			PageSize: pageSize,
		},
	})
}

// parsePage extracts page and page_size from query params.
// page defaults to 1, page_size defaults to 20, capped at 100.
func parsePage(c *gin.Context) (page int, pageSize int, offset int) {
	page = 1
	pageSize = 20
	if p := c.Query("page"); p != "" {
		if v := parseInt(p, 1); v > 0 {
			page = v
		}
	}
	if ps := c.Query("page_size"); ps != "" {
		if v := parseInt(ps, 20); v > 0 {
			pageSize = v
		}
	}
	if pageSize > 100 {
		pageSize = 100
	}
	offset = (page - 1) * pageSize
	return
}

func parseInt(s string, def int) int {
	result := 0
	for _, ch := range s {
		if ch < '0' || ch > '9' {
			return def
		}
		result = result*10 + int(ch-'0')
	}
	if s == "" {
		return def
	}
	return result
}