git-bug/identity/resolver.go

package identity

import (
	"sync"

	"github.com/MichaelMure/git-bug/entity"
	"github.com/MichaelMure/git-bug/repository"
)

// Resolver define the interface of an Identity resolver, able to load
// an identity from, for example, a repo or a cache.
type Resolver interface {
	ResolveIdentity(id entity.Id) (Interface, error)
}

// SimpleResolver is a Resolver loading Identities directly from a Repo
type SimpleResolver struct {
	repo repository.Repo
}

func NewSimpleResolver(repo repository.Repo) *SimpleResolver {
	return &SimpleResolver{repo: repo}
}

func (r *SimpleResolver) ResolveIdentity(id entity.Id) (Interface, error) {
	return ReadLocal(r.repo, id)
}

// StubResolver is a Resolver that doesn't load anything, only returning IdentityStub instances
type StubResolver struct{}

func NewStubResolver() *StubResolver {
	return &StubResolver{}
}

func (s *StubResolver) ResolveIdentity(id entity.Id) (Interface, error) {
	return &IdentityStub{id: id}, nil
}

// CachedResolver is a resolver ensuring that loading is done only once through another Resolver.
type CachedResolver struct {
	mu         sync.RWMutex
	resolver   Resolver
	identities map[entity.Id]Interface
}

func NewCachedResolver(resolver Resolver) *CachedResolver {
	return &CachedResolver{
		resolver:   resolver,
		identities: make(map[entity.Id]Interface),
	}
}

func (c *CachedResolver) ResolveIdentity(id entity.Id) (Interface, error) {
	c.mu.RLock()
	if i, ok := c.identities[id]; ok {
		c.mu.RUnlock()
		return i, nil
	}
	c.mu.RUnlock()

	c.mu.Lock()
	defer c.mu.Unlock()

	i, err := c.resolver.ResolveIdentity(id)
	if err != nil {
		return nil, err
	}
	c.identities[id] = i
	return i, nil
}