package httpapi

import (
	"net/http"
	"strconv"

	"evobgp/internal/store"
)

func parseListLimit(r *http.Request) int {
	limit, _ := strconv.Atoi(r.URL.Query().Get("limit"))
	if limit <= 0 {
		return 50
	}
	if limit > 500 {
		return 500
	}
	return limit
}

func strPtrOrNull(s string) any {
	if s == "" {
		return nil
	}
	return s
}

// writePaginatedListJSON returns a cursor/limit page as OpenAPI list envelopes (items, next_cursor, has_more).
func writePaginatedListJSON[T any](w http.ResponseWriter, r *http.Request, all []T, toItem func(T) map[string]any) {
	page, next, more := store.PaginateOffset(all, r.URL.Query().Get("cursor"), parseListLimit(r))
	items := make([]map[string]any, 0, len(page))
	for _, x := range page {
		items = append(items, toItem(x))
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"items": items, "next_cursor": strPtrOrNull(next), "has_more": more,
	})
}