package examplelibrary

import (
	"context"

	"google.golang.org/genproto/googleapis/example/library/v1"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"

	"github.com/sraphs/aip/pagination"
)

var generator = pagination.TokenGeneratorWithSalt("example.library.ListShelves")

func (s *Server) ListShelves(
	ctx context.Context,
	request *library.ListShelvesRequest,
) (*library.ListShelvesResponse, error) {
	// Handle request constraints.
	const (
		maxPageSize     = 1000
		defaultPageSize = 100
	)
	switch {
	case request.PageSize < 0:
		return nil, status.Errorf(codes.InvalidArgument, "page size is negative")
	case request.PageSize == 0:
		request.PageSize = defaultPageSize
	case request.PageSize > maxPageSize:
		request.PageSize = maxPageSize
	}
	// Use pagination.PageToken for offset-based page tokens.
	offset, err := generator.GetIndex(request.PageToken)
	if err != nil {
		return nil, status.Errorf(codes.InvalidArgument, "invalid page token")
	}
	// Query the storage.
	result, err := s.Storage.ListShelves(ctx, &ListShelvesQuery{
		Offset:   int64(offset),
		PageSize: request.GetPageSize(),
	})
	if err != nil {
		return nil, err
	}
	// Build the response.
	response := &library.ListShelvesResponse{
		Shelves: result.Shelves,
	}
	// Set the next page token.
	if result.HasNextPage {
		response.NextPageToken = generator.ForIndex(offset + int(request.PageSize))
	}
	// Respond.
	return response, nil
}