add a cache to support the graphql API and the future interactive CLI UI

1 files changed, 160 insertions, 0 deletions

diff --git a/cache/cache.go b/cache/cache.go
new file mode 100644
index 00000000..a46922be
--- /dev/null
+++ b/cache/cache.go
@@ -0,0 +1,160 @@
+package cache
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/MichaelMure/git-bug/bug"
+	"github.com/MichaelMure/git-bug/repository"
+)
+
+type Cache interface {
+	RegisterRepository(ref string, repo repository.Repo)
+	RegisterDefaultRepository(repo repository.Repo)
+	ResolveRepo(ref string) (CachedRepo, error)
+	DefaultRepo() (CachedRepo, error)
+}
+
+type CachedRepo interface {
+	ResolveBug(id string) (CachedBug, error)
+	ResolveBugPrefix(prefix string) (CachedBug, error)
+	ClearAllBugs()
+}
+
+type CachedBug interface {
+	Snapshot() bug.Snapshot
+	ClearSnapshot()
+}
+
+// Cache ------------------------
+
+type DefaultCache struct {
+	repos map[string]CachedRepo
+}
+
+func NewDefaultCache() Cache {
+	return &DefaultCache{
+		repos: make(map[string]CachedRepo),
+	}
+}
+
+func (c *DefaultCache) RegisterRepository(ref string, repo repository.Repo) {
+	c.repos[ref] = NewCachedRepo(repo)
+}
+
+func (c *DefaultCache) RegisterDefaultRepository(repo repository.Repo) {
+	c.repos[""] = NewCachedRepo(repo)
+}
+
+func (c *DefaultCache) DefaultRepo() (CachedRepo, error) {
+	if len(c.repos) != 1 {
+		return nil, fmt.Errorf("repository is not unique")
+	}
+
+	for _, r := range c.repos {
+		return r, nil
+	}
+
+	panic("unreachable")
+}
+
+func (c *DefaultCache) ResolveRepo(ref string) (CachedRepo, error) {
+	r, ok := c.repos[ref]
+	if !ok {
+		return nil, fmt.Errorf("unknown repo")
+	}
+	return r, nil
+}
+
+// Repo ------------------------
+
+type CachedRepoImpl struct {
+	repo repository.Repo
+	bugs map[string]CachedBug
+}
+
+func NewCachedRepo(r repository.Repo) CachedRepo {
+	return &CachedRepoImpl{
+		repo: r,
+		bugs: make(map[string]CachedBug),
+	}
+}
+
+func (c CachedRepoImpl) ResolveBug(id string) (CachedBug, error) {
+	cached, ok := c.bugs[id]
+	if ok {
+		return cached, nil
+	}
+
+	b, err := bug.ReadLocalBug(c.repo, id)
+	if err != nil {
+		return nil, err
+	}
+
+	cached = NewCachedBug(b)
+	c.bugs[id] = cached
+
+	return cached, nil
+}
+
+func (c CachedRepoImpl) ResolveBugPrefix(prefix string) (CachedBug, error) {
+	// preallocate but empty
+	matching := make([]string, 0, 5)
+
+	for id := range c.bugs {
+		if strings.HasPrefix(id, prefix) {
+			matching = append(matching, id)
+		}
+	}
+
+	// TODO: should check matching bug in the repo as well
+
+	if len(matching) > 1 {
+		return nil, fmt.Errorf("Multiple matching bug found:\n%s", strings.Join(matching, "\n"))
+	}
+
+	if len(matching) == 1 {
+		b := c.bugs[matching[0]]
+		return b, nil
+	}
+
+	b, err := bug.FindLocalBug(c.repo, prefix)
+
+	if err != nil {
+		return nil, err
+	}
+
+	cached := NewCachedBug(b)
+	c.bugs[b.Id()] = cached
+
+	return cached, nil
+}
+
+func (c CachedRepoImpl) ClearAllBugs() {
+	c.bugs = make(map[string]CachedBug)
+}
+
+// Bug ------------------------
+
+type CachedBugImpl struct {
+	bug  *bug.Bug
+	snap *bug.Snapshot
+}
+
+func NewCachedBug(b *bug.Bug) CachedBug {
+	return &CachedBugImpl{
+		bug: b,
+	}
+}
+
+func (c CachedBugImpl) Snapshot() bug.Snapshot {
+	if c.snap == nil {
+		snap := c.bug.Compile()
+		c.snap = &snap
+	}
+	return *c.snap
+}
+
+func (c CachedBugImpl) ClearSnapshot() {
+	c.snap = nil
+}