package domain

import (
	"errors"

	"calllinesystem/server/internal/model"
)

var ErrFirstTicketExceedsPeopleTarget = errors.New("first ticket party size exceeds people target")

// SelectTicketsForCall preserves the incoming FIFO order. Ticket mode selects
// up to target tickets. People mode selects the longest leading sequence whose
// total party size does not exceed target; tickets are never split or skipped.
func SelectTicketsForCall(tickets []model.QueueTicket, mode string, target int) ([]model.QueueTicket, int, error) {
	if target < 1 || len(tickets) == 0 {
		return nil, 0, nil
	}
	if mode == model.CallModeTicket {
		count := min(target, len(tickets))
		selected := tickets[:count]
		return selected, totalPartySize(selected), nil
	}
	if mode != model.CallModePeople {
		return nil, 0, errors.New("unsupported call mode")
	}
	total := 0
	count := 0
	for _, ticket := range tickets {
		if total+ticket.PartySize > target {
			break
		}
		total += ticket.PartySize
		count++
	}
	if count == 0 {
		return nil, 0, ErrFirstTicketExceedsPeopleTarget
	}
	return tickets[:count], total, nil
}

func totalPartySize(tickets []model.QueueTicket) int {
	total := 0
	for _, ticket := range tickets {
		total += ticket.PartySize
	}
	return total
}