cmd/mbf: optionally open cache

Some commands do not require the cache. This change also makes acquisition of locked cache cancelable.

Signed-off-by: Ophestra <cat@gensokyo.uk>

3 files changed, 219 insertions, 76 deletions

diff --git a/cmd/mbf/cache.go b/cmd/mbf/cache.go
new file mode 100644
index 00000000..16e77cbc
--- /dev/null
+++ b/cmd/mbf/cache.go
@@ -0,0 +1,90 @@
+package main
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+
+	"hakurei.app/check"
+	"hakurei.app/internal/pkg"
+	"hakurei.app/message"
+)
+
+// cache refers to an instance of [pkg.Cache] that might be open.
+type cache struct {
+	ctx context.Context
+	msg message.Msg
+
+	// Should generally not be used directly.
+	c *pkg.Cache
+
+	cures, jobs        int
+	hostAbstract, idle bool
+
+	base string
+}
+
+// open opens the underlying [pkg.Cache].
+func (cache *cache) open() (err error) {
+	if cache.c != nil {
+		return os.ErrInvalid
+	}
+
+	if cache.base == "" {
+		cache.base = "cache"
+	}
+	var base *check.Absolute
+	if cache.base, err = filepath.Abs(cache.base); err != nil {
+		return
+	} else if base, err = check.NewAbs(cache.base); err != nil {
+		return
+	}
+
+	var flags int
+	if cache.idle {
+		flags |= pkg.CSchedIdle
+	}
+	if cache.hostAbstract {
+		flags |= pkg.CHostAbstract
+	}
+
+	done := make(chan struct{})
+	defer close(done)
+	go func() {
+		select {
+		case <-cache.ctx.Done():
+			os.Exit(2)
+
+		case <-done:
+			return
+		}
+	}()
+
+	cache.msg.Verbosef("opening cache at %s", base)
+	cache.c, err = pkg.Open(
+		cache.ctx,
+		cache.msg,
+		flags,
+		cache.cures,
+		cache.jobs,
+		base,
+	)
+	return
+}
+
+// Close closes the underlying [pkg.Cache] if it is open.
+func (cache *cache) Close() {
+	if cache.c != nil {
+		cache.c.Close()
+	}
+}
+
+// Do calls f on the underlying cache and returns its error value.
+func (cache *cache) Do(f func(cache *pkg.Cache) error) error {
+	if cache.c == nil {
+		if err := cache.open(); err != nil {
+			return err
+		}
+	}
+	return f(cache.c)
+}
diff --git a/cmd/mbf/cache_test.go b/cmd/mbf/cache_test.go
new file mode 100644
index 00000000..0f036542
--- /dev/null
+++ b/cmd/mbf/cache_test.go
@@ -0,0 +1,38 @@
+package main
+
+import (
+	"context"
+	"log"
+	"os"
+	"testing"
+
+	"hakurei.app/internal/pkg"
+	"hakurei.app/message"
+)
+
+func TestCache(t *testing.T) {
+	t.Parallel()
+
+	cm := cache{
+		ctx:  context.Background(),
+		msg:  message.New(log.New(os.Stderr, "check: ", 0)),
+		base: t.TempDir(),
+
+		hostAbstract: true, idle: true,
+	}
+	defer cm.Close()
+	cm.Close()
+
+	if err := cm.open(); err != nil {
+		t.Fatalf("open: error = %v", err)
+	}
+	if err := cm.open(); err != os.ErrInvalid {
+		t.Errorf("(duplicate) open: error = %v", err)
+	}
+
+	if err := cm.Do(func(cache *pkg.Cache) error {
+		return cache.Scrub(0)
+	}); err != nil {
+		t.Errorf("Scrub: error = %v", err)
+	}
+}
diff --git a/cmd/mbf/main.go b/cmd/mbf/main.go
index a9d9a0c8..bfa2aa07 100644
--- a/cmd/mbf/main.go
+++ b/cmd/mbf/main.go
@@ -54,14 +54,13 @@ func main() {
 		log.Fatal("this program must not run as root")
 	}
 
-	var cache *pkg.Cache
 	ctx, stop := signal.NotifyContext(context.Background(),
 		syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)
 	defer stop()
+
+	var cm cache
 	defer func() {
-		if cache != nil {
-			cache.Close()
-		}
+		cm.Close()
 
 		if r := recover(); r != nil {
 			fmt.Println(r)
@@ -71,60 +70,34 @@ func main() {
 
 	var (
 		flagQuiet bool
-		flagCures int
-		flagJobs  int
-		flagBase  string
-		flagIdle  bool
-
-		flagHostAbstract bool
 	)
-	c := command.New(os.Stderr, log.Printf, "mbf", func([]string) (err error) {
+	c := command.New(os.Stderr, log.Printf, "mbf", func([]string) error {
 		msg.SwapVerbose(!flagQuiet)
-
-		flagBase = os.ExpandEnv(flagBase)
-		if flagBase == "" {
-			flagBase = "cache"
-		}
-
-		var base *check.Absolute
-		if flagBase, err = filepath.Abs(flagBase); err != nil {
-			return
-		} else if base, err = check.NewAbs(flagBase); err != nil {
-			return
-		}
-
-		var flags int
-		if flagIdle {
-			flags |= pkg.CSchedIdle
-		}
-		if flagHostAbstract {
-			flags |= pkg.CHostAbstract
-		}
-		cache, err = pkg.Open(ctx, msg, flags, flagCures, flagJobs, base)
-
-		return
+		cm.ctx, cm.msg = ctx, msg
+		cm.base = os.ExpandEnv(cm.base)
+		return nil
 	}).Flag(
 		&flagQuiet,
 		"q", command.BoolFlag(false),
 		"Do not print cure messages",
 	).Flag(
-		&flagCures,
+		&cm.cures,
 		"cures", command.IntFlag(0),
 		"Maximum number of dependencies to cure at any given time",
 	).Flag(
-		&flagJobs,
+		&cm.jobs,
 		"jobs", command.IntFlag(0),
 		"Preferred number of jobs to run, when applicable",
 	).Flag(
-		&flagBase,
+		&cm.base,
 		"d", command.StringFlag("$MBF_CACHE_DIR"),
 		"Directory to store cured artifacts",
 	).Flag(
-		&flagIdle,
+		&cm.idle,
 		"sched-idle", command.BoolFlag(false),
 		"Set SCHED_IDLE scheduling policy",
 	).Flag(
-		&flagHostAbstract,
+		&cm.hostAbstract,
 		"host-abstract", command.BoolFlag(
 			os.Getenv("MBF_HOST_ABSTRACT") != "",
 		),
@@ -156,7 +129,9 @@ func main() {
 				if flagShifts < 0 || flagShifts > 31 {
 					flagShifts = 12
 				}
-				return cache.Scrub(runtime.NumCPU() << flagShifts)
+				return cm.Do(func(cache *pkg.Cache) error {
+					return cache.Scrub(runtime.NumCPU() << flagShifts)
+				})
 			},
 		).Flag(
 			&flagShifts,
@@ -223,7 +198,10 @@ func main() {
 						if flagStatus {
 							if r == nil {
 								var f io.ReadSeekCloser
-								f, err = cache.OpenStatus(rosa.Std.Load(p))
+								err = cm.Do(func(cache *pkg.Cache) (err error) {
+									f, err = cache.OpenStatus(rosa.Std.Load(p))
+									return
+								})
 								if err != nil {
 									if errors.Is(err, os.ErrNotExist) {
 										fmt.Println(
@@ -239,7 +217,7 @@ func main() {
 										return
 									}
 								}
-							} else {
+							} else if err = cm.Do(func(cache *pkg.Cache) (err error) {
 								status, n := r.ArtifactOf(cache.Ident(rosa.Std.Load(p)))
 								if status == nil {
 									fmt.Println(
@@ -252,6 +230,9 @@ func main() {
 										return
 									}
 								}
+								return
+							}); err != nil {
+								return
 							}
 						}
 
@@ -306,7 +287,9 @@ func main() {
 			if ext.Isatty(int(w.Fd())) {
 				return errors.New("output appears to be a terminal")
 			}
-			return rosa.WriteReport(msg, w, cache)
+			return cm.Do(func(cache *pkg.Cache) error {
+				return rosa.WriteReport(msg, w, cache)
+			})
 		},
 	)
 
@@ -406,23 +389,32 @@ func main() {
 					checksum [2]unique.Handle[pkg.Checksum]
 				)
 
-				if pathname, _, err = cache.Cure(
-					(t - 2).Load(rosa.Clang),
-				); err != nil {
-					return err
+				if err = cm.Do(func(cache *pkg.Cache) (err error) {
+					pathname, _, err = cache.Cure(
+						(t - 2).Load(rosa.Clang),
+					)
+					return
+				}); err != nil {
+					return
 				}
 				log.Println("stage1:", pathname)
 
-				if pathname, checksum[0], err = cache.Cure(
-					(t - 1).Load(rosa.Clang),
-				); err != nil {
-					return err
+				if err = cm.Do(func(cache *pkg.Cache) (err error) {
+					pathname, checksum[0], err = cache.Cure(
+						(t - 1).Load(rosa.Clang),
+					)
+					return
+				}); err != nil {
+					return
 				}
 				log.Println("stage2:", pathname)
-				if pathname, checksum[1], err = cache.Cure(
-					t.Load(rosa.Clang),
-				); err != nil {
-					return err
+				if err = cm.Do(func(cache *pkg.Cache) (err error) {
+					pathname, checksum[1], err = cache.Cure(
+						t.Load(rosa.Clang),
+					)
+					return
+				}); err != nil {
+					return
 				}
 				log.Println("stage3:", pathname)
 
@@ -439,10 +431,13 @@ func main() {
 				}
 
 				if flagStage0 {
-					if pathname, _, err = cache.Cure(
-						t.Load(rosa.Stage0),
-					); err != nil {
-						return err
+					if err = cm.Do(func(cache *pkg.Cache) (err error) {
+						pathname, _, err = cache.Cure(
+							t.Load(rosa.Stage0),
+						)
+						return
+					}); err != nil {
+						return
 					}
 					log.Println(pathname)
 				}
@@ -487,7 +482,11 @@ func main() {
 
 				switch {
 				default:
-					pathname, _, err := cache.Cure(rosa.Std.Load(p))
+					var pathname *check.Absolute
+					err := cm.Do(func(cache *pkg.Cache) (err error) {
+						pathname, _, err = cache.Cure(rosa.Std.Load(p))
+						return
+					})
 					if err != nil {
 						return err
 					}
@@ -527,7 +526,9 @@ func main() {
 						return err
 					}
 
-					if err = cache.EncodeAll(f, rosa.Std.Load(p)); err != nil {
+					if err = cm.Do(func(cache *pkg.Cache) error {
+						return cache.EncodeAll(f, rosa.Std.Load(p))
+					}); err != nil {
 						_ = f.Close()
 						return err
 					}
@@ -535,13 +536,15 @@ func main() {
 					return f.Close()
 
 				case flagEnter:
-					return cache.EnterExec(
-						ctx,
-						rosa.Std.Load(p),
-						true, os.Stdin, os.Stdout, os.Stderr,
-						rosa.AbsSystem.Append("bin", "mksh"),
-						"sh",
-					)
+					return cm.Do(func(cache *pkg.Cache) error {
+						return cache.EnterExec(
+							ctx,
+							rosa.Std.Load(p),
+							true, os.Stdin, os.Stdout, os.Stderr,
+							rosa.AbsSystem.Append("bin", "mksh"),
+							"sh",
+						)
+					})
 				}
 			},
 		).
@@ -595,7 +598,10 @@ func main() {
 				root := make(pkg.Collect, 0, 6+len(args))
 				root = rosa.Std.AppendPresets(root, presets...)
 
-				if _, _, err := cache.Cure(&root); err == nil {
+				if err := cm.Do(func(cache *pkg.Cache) error {
+					_, _, err := cache.Cure(&root)
+					return err
+				}); err == nil {
 					return errors.New("unreachable")
 				} else if !pkg.IsCollected(err) {
 					return err
@@ -607,11 +613,22 @@ func main() {
 				}
 				cured := make(map[pkg.Artifact]cureRes)
 				for _, a := range root {
-					pathname, checksum, err := cache.Cure(a)
-					if err != nil {
+					if err := cm.Do(func(cache *pkg.Cache) error {
+						pathname, checksum, err := cache.Cure(a)
+						if err == nil {
+							cured[a] = cureRes{pathname, checksum}
+						}
+						return err
+					}); err != nil {
+						return err
+					}
+				}
+
+				// explicitly open for direct error-free use from this point
+				if cm.c == nil {
+					if err := cm.open(); err != nil {
 						return err
 					}
-					cured[a] = cureRes{pathname, checksum}
 				}
 
 				layers := pkg.PromoteLayers(root, func(a pkg.Artifact) (
@@ -621,7 +638,7 @@ func main() {
 					res := cured[a]
 					return res.pathname, res.checksum
 				}, func(i int, d pkg.Artifact) {
-					r := pkg.Encode(cache.Ident(d).Value())
+					r := pkg.Encode(cm.c.Ident(d).Value())
 					if s, ok := d.(fmt.Stringer); ok {
 						if name := s.String(); name != "" {
 							r += "-" + name
@@ -711,9 +728,7 @@ func main() {
 	)
 
 	c.MustParse(os.Args[1:], func(err error) {
-		if cache != nil {
-			cache.Close()
-		}
+		cm.Close()
 		if w, ok := err.(interface{ Unwrap() []error }); !ok {
 			log.Fatal(err)
 		} else {