cep/executor/tvm.go

package executor

import (
	"errors"
	"sync"

	"github.com/google/uuid"
)

var ErrTicketPoolFull = errors.New("ticket pool full")
var ErrTicketNotTaken = errors.New("ticket not taken")
var ErrTicketNotFound = errors.New("ticket not found")

type Ticket struct {
	Index int
	UUID  string
	Taken bool
}

type TVM struct {
	mutex   sync.Mutex
	tickets map[int]*Ticket
	size    int
}

func NewTVM(size int) *TVM {
	tickets := map[int]*Ticket{}
	for i := 0; i < size; i++ {
		tickets[i] = &Ticket{
			Index: i,
			UUID:  "",
			Taken: false,
		}
	}

	return &TVM{
		tickets: tickets,
		size:    size,
	}
}

func (this *TVM) AcquireTicket() (*Ticket, error) {
	this.mutex.Lock()
	defer this.mutex.Unlock()

	for i := range len(this.tickets) {
		if this.tickets[i].Taken {
			continue
		}

		this.tickets[i].UUID = uuid.New().String()
		this.tickets[i].Taken = true
		return this.tickets[i], nil
	}

	return nil, ErrTicketPoolFull
}

func (this *TVM) ReleaseTicket(UUID string) error {
	this.mutex.Lock()
	defer this.mutex.Unlock()

	for index, ticket := range this.tickets {
		if ticket.UUID != UUID {
			continue
		}

		if !ticket.Taken {
			return ErrTicketNotTaken
		}

		this.tickets[index].UUID = ""
		this.tickets[index].Taken = false
		return nil
	}

	return ErrTicketNotFound
}

func (this *TVM) FindTicket(UUID string) (*Ticket, error) {
	this.mutex.Lock()
	defer this.mutex.Unlock()

	for _, ticket := range this.tickets {
		if ticket.UUID != UUID {
			continue
		}

		if !ticket.Taken {
			return nil, ErrTicketNotTaken
		}

		return ticket, nil
	}

	return nil, ErrTicketNotFound
}

func (this *TVM) Capacity() int {
	this.mutex.Lock()
	defer this.mutex.Unlock()

	counter := 0
	for i := range len(this.tickets) {
		if !this.tickets[i].Taken {
			counter += 1
		}
	}

	return counter
}

func (this *TVM) HasTicket(UUID string) bool {
	this.mutex.Lock()
	defer this.mutex.Unlock()

	for _, ticket := range this.tickets {
		if ticket.UUID != UUID {
			continue
		}

		return ticket.Taken
	}

	return false
}