internal/pkg: pass cure context as single value

This cleans up the function signature and makes backwards compatible API changes possible.

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

4 files changed, 86 insertions, 55 deletions

diff --git a/internal/pkg/net.go b/internal/pkg/net.go
index 074c5f79..9a6814f8 100644
--- a/internal/pkg/net.go
+++ b/internal/pkg/net.go
@@ -7,8 +7,6 @@ import (
 	"net/http"
 	"sync"
 	"syscall"
-
-	"hakurei.app/container/check"
 )
 
 // An httpArtifact is an [Artifact] backed by a [http] url string. The method is
@@ -101,7 +99,7 @@ func (a *httpArtifact) do() (data []byte, err error) {
 }
 
 // Cure returns syscall.ENOTSUP. Callers should use Data instead.
-func (a *httpArtifact) Cure(*check.Absolute, *check.Absolute, CacheDataFunc) error {
+func (a *httpArtifact) Cure(*CureContext) error {
 	return syscall.ENOTSUP
 }
 
diff --git a/internal/pkg/pkg.go b/internal/pkg/pkg.go
index ec81995d..e1055aca 100644
--- a/internal/pkg/pkg.go
+++ b/internal/pkg/pkg.go
@@ -53,9 +53,36 @@ func MustDecode(s string) Checksum {
 	}
 }
 
-// CacheDataFunc tries to load [File] from [Cache], and if that fails, obtains
-// it via [File.Data] instead.
-type CacheDataFunc func(f File) (data []byte, err error)
+// CureContext is passed to [Artifact.Cure] and contains information and methods
+// useful for curing the [Artifact], like requesting the data of [File], or that
+// other artifacts be cured.
+//
+// Methods of CureContext are safe for concurrent use. CureContext is valid
+// until [Artifact.Cure] returns.
+type CureContext struct {
+	// Address of underlying [Cache], should be zeroed after [Artifact.Cure]
+	// returns and must not be exposed directly.
+	cache *Cache
+
+	// Populated during [Cache.Cure].
+	work, temp *check.Absolute
+}
+
+// GetWorkDir returns a pathname to a directory which [Artifact] is expected to
+// write its output to. This is not the final resting place of the [Artifact]
+// and this pathname should not be directly referred to in the final contents.
+func (c *CureContext) GetWorkDir() *check.Absolute { return c.work }
+
+// GetTempDir returns a pathname which implementations may use as scratch space.
+// A directory is not created automatically, implementations are expected to
+// create it if they wish to use it, using [os.MkdirAll].
+func (c *CureContext) GetTempDir() *check.Absolute { return c.temp }
+
+// LoadData tries to load [File] from [Cache], and if that fails, obtains it via
+// [File.Data] instead. Notably, it does not cure [File].
+func (c *CureContext) LoadData(f File) (data []byte, err error) {
+	return c.cache.loadData(f)
+}
 
 // An Artifact is a read-only reference to a piece of data that may be created
 // deterministically but might not currently be available in memory or on the
@@ -83,18 +110,15 @@ type Artifact interface {
 	// Result must remain identical across multiple invocations.
 	Dependencies() []Artifact
 
-	// Cure cures the current [Artifact] to the caller-specified temporary
-	// pathname. This is not the final resting place of the [Artifact] and this
-	// pathname should not be directly referred to in the final contents.
+	// Cure cures the current [Artifact] to the working directory obtained via
+	// [CureContext.GetWorkDir].
 	//
 	// If the implementation produces a single file, it must implement [File]
 	// as well. In that case, Cure must produce a single regular file with
 	// contents identical to that returned by [File.Data].
 	//
-	// Implementations may use temp as scratch space. The caller is not required
-	// to create a directory here, implementations are expected to create it if
-	// they wish to use it, using [os.MkdirAll].
-	Cure(work, temp *check.Absolute, loadData CacheDataFunc) (err error)
+	// Implementations must not retain c.
+	Cure(c *CureContext) (err error)
 }
 
 // KnownIdent is optionally implemented by [Artifact] and is used instead of
@@ -515,7 +539,7 @@ func (c *Cache) finaliseIdent(
 	close(done)
 }
 
-// loadData provides [CacheDataFunc] for [Artifact.Cure].
+// loadData provides [CureContext.LoadData] for [Artifact.Cure].
 func (c *Cache) loadData(f File) (data []byte, err error) {
 	var r *os.File
 	if kc, ok := f.(KnownChecksum); ok {
@@ -790,10 +814,14 @@ func (c *Cache) Cure(a Artifact) (
 			return
 		}
 
-		workPathname := c.base.Append(dirWork, ids)
+		cc := CureContext{
+			cache: c,
+			work:  c.base.Append(dirWork, ids),
+			temp:  c.base.Append(dirTemp, ids),
+		}
 		defer func() {
 			if err != nil {
-				chmodErr, removeErr := removeAll(workPathname)
+				chmodErr, removeErr := removeAll(cc.work)
 				if chmodErr != nil || removeErr != nil {
 					err = errors.Join(err, chmodErr, removeErr)
 				} else if errors.Is(err, os.ErrExist) {
@@ -803,17 +831,17 @@ func (c *Cache) Cure(a Artifact) (
 			}
 		}()
 
-		tempPathname := c.base.Append(dirTemp, ids)
-		if err = a.Cure(workPathname, tempPathname, c.loadData); err != nil {
+		if err = a.Cure(&cc); err != nil {
 			return
 		}
-		if chmodErr, removeErr := removeAll(tempPathname); chmodErr != nil || removeErr != nil {
+		cc.cache = nil
+		if chmodErr, removeErr := removeAll(cc.temp); chmodErr != nil || removeErr != nil {
 			err = errors.Join(err, chmodErr, removeErr)
 			return
 		}
 
 		var fi os.FileInfo
-		if fi, err = os.Lstat(workPathname.String()); err != nil {
+		if fi, err = os.Lstat(cc.work.String()); err != nil {
 			if errors.Is(err, os.ErrNotExist) {
 				err = NoOutputError{}
 			}
@@ -831,7 +859,7 @@ func (c *Cache) Cure(a Artifact) (
 
 		var gotChecksum Checksum
 		if gotChecksum, err = HashFS(
-			dotOverrideFS{os.DirFS(workPathname.String()).(dirFS)},
+			dotOverrideFS{os.DirFS(cc.work.String()).(dirFS)},
 			".",
 		); err != nil {
 			return
@@ -854,12 +882,12 @@ func (c *Cache) Cure(a Artifact) (
 			}
 		}
 
-		if err = os.Chmod(workPathname.String(), 0700); err != nil {
+		if err = os.Chmod(cc.work.String(), 0700); err != nil {
 			return
 		}
 		c.checksumMu.Lock()
 		if err = os.Rename(
-			workPathname.String(),
+			cc.work.String(),
 			checksumPathname.String(),
 		); err != nil {
 			if !errors.Is(err, os.ErrExist) {
diff --git a/internal/pkg/pkg_test.go b/internal/pkg/pkg_test.go
index 8826e5a1..dca39324 100644
--- a/internal/pkg/pkg_test.go
+++ b/internal/pkg/pkg_test.go
@@ -73,19 +73,13 @@ type stubArtifact struct {
 	params []byte
 	deps   []pkg.Artifact
 
-	cure func(work, temp *check.Absolute, loadData pkg.CacheDataFunc) error
+	cure func(c *pkg.CureContext) error
 }
 
-func (a stubArtifact) Kind() pkg.Kind               { return a.kind }
-func (a stubArtifact) Params() []byte               { return a.params }
-func (a stubArtifact) Dependencies() []pkg.Artifact { return a.deps }
-
-func (a stubArtifact) Cure(
-	work, temp *check.Absolute,
-	loadData pkg.CacheDataFunc,
-) error {
-	return a.cure(work, temp, loadData)
-}
+func (a stubArtifact) Kind() pkg.Kind                { return a.kind }
+func (a stubArtifact) Params() []byte                { return a.params }
+func (a stubArtifact) Dependencies() []pkg.Artifact  { return a.deps }
+func (a stubArtifact) Cure(c *pkg.CureContext) error { return a.cure(c) }
 
 // A stubFile implements [File] with hardcoded behaviour.
 type stubFile struct {
@@ -109,7 +103,7 @@ func newStubFile(
 		kind,
 		nil,
 		nil,
-		func(*check.Absolute, *check.Absolute, pkg.CacheDataFunc) error {
+		func(*pkg.CureContext) error {
 			panic("unreachable")
 		},
 	}}}
@@ -410,7 +404,8 @@ func TestCache(t *testing.T) {
 				binary.LittleEndian.AppendUint64(nil, pkg.TarGzip),
 				overrideIdent{testdataChecksum, stubArtifact{}},
 			)
-			makeSample := func(work, _ *check.Absolute, _ pkg.CacheDataFunc) error {
+			makeSample := func(c *pkg.CureContext) error {
+				work := c.GetWorkDir()
 				if err := os.Mkdir(work.String(), 0700); err != nil {
 					return err
 				}
@@ -511,15 +506,15 @@ func TestCache(t *testing.T) {
 
 				{"cure fault", overrideIdent{pkg.ID{0xff, 0}, stubArtifact{
 					kind: pkg.KindTar,
-					cure: func(work, _ *check.Absolute, _ pkg.CacheDataFunc) error {
-						return makeGarbage(work, stub.UniqueError(0xcafe))
+					cure: func(c *pkg.CureContext) error {
+						return makeGarbage(c.GetWorkDir(), stub.UniqueError(0xcafe))
 					},
 				}}, nil, pkg.Checksum{}, stub.UniqueError(0xcafe)},
 
 				{"checksum mismatch", overrideChecksum{pkg.Checksum{}, overrideIdent{pkg.ID{0xff, 1}, stubArtifact{
 					kind: pkg.KindTar,
-					cure: func(work, _ *check.Absolute, _ pkg.CacheDataFunc) error {
-						return makeGarbage(work, nil)
+					cure: func(c *pkg.CureContext) error {
+						return makeGarbage(c.GetWorkDir(), nil)
 					},
 				}}}, nil, pkg.Checksum{}, &pkg.ChecksumMismatchError{
 					Got: pkg.MustDecode(
@@ -538,8 +533,8 @@ func TestCache(t *testing.T) {
 
 				{"loadData directory", overrideIdent{pkg.ID{0xff, 3}, stubArtifact{
 					kind: pkg.KindTar,
-					cure: func(work, _ *check.Absolute, loadData pkg.CacheDataFunc) error {
-						_, err := loadData(overrideChecksumFile{checksum: wantChecksum})
+					cure: func(c *pkg.CureContext) error {
+						_, err := c.LoadData(overrideChecksumFile{checksum: wantChecksum})
 						return err
 					},
 				}}, nil, pkg.Checksum{}, &os.PathError{
@@ -553,22 +548,25 @@ func TestCache(t *testing.T) {
 
 				{"no output", overrideIdent{pkg.ID{0xff, 4}, stubArtifact{
 					kind: pkg.KindTar,
-					cure: func(work, _ *check.Absolute, loadData pkg.CacheDataFunc) error {
+					cure: func(c *pkg.CureContext) error {
 						return nil
 					},
 				}}, nil, pkg.Checksum{}, pkg.NoOutputError{}},
 
 				{"file output", overrideIdent{pkg.ID{0xff, 5}, stubArtifact{
 					kind: pkg.KindTar,
-					cure: func(work, _ *check.Absolute, loadData pkg.CacheDataFunc) error {
-						return os.WriteFile(work.String(), []byte{0}, 0400)
+					cure: func(c *pkg.CureContext) error {
+						return os.WriteFile(c.GetWorkDir().String(), []byte{0}, 0400)
 					},
 				}}, nil, pkg.Checksum{}, errors.New("non-file artifact produced regular file")},
 
 				{"symlink output", overrideIdent{pkg.ID{0xff, 6}, stubArtifact{
 					kind: pkg.KindTar,
-					cure: func(work, _ *check.Absolute, loadData pkg.CacheDataFunc) error {
-						return os.Symlink(work.String(), work.String())
+					cure: func(c *pkg.CureContext) error {
+						return os.Symlink(
+							c.GetWorkDir().String(),
+							c.GetWorkDir().String(),
+						)
 					},
 				}}, nil, pkg.Checksum{}, pkg.InvalidFileModeError(
 					fs.ModeSymlink | 0777,
@@ -584,7 +582,7 @@ func TestCache(t *testing.T) {
 			go func() {
 				if _, _, err := c.Cure(overrideIdent{pkg.ID{0xff}, stubArtifact{
 					kind: pkg.KindTar,
-					cure: func(work, _ *check.Absolute, loadData pkg.CacheDataFunc) error {
+					cure: func(c *pkg.CureContext) error {
 						close(ready)
 						<-n
 						return wantErr
@@ -616,10 +614,16 @@ func TestCache(t *testing.T) {
 
 				{"file output", overrideIdent{pkg.ID{0xff, 2}, stubArtifact{
 					kind: pkg.KindTar,
-					cure: func(work, _ *check.Absolute, loadData pkg.CacheDataFunc) error {
-						return os.WriteFile(work.String(), []byte{0}, 0400)
+					cure: func(c *pkg.CureContext) error {
+						return os.WriteFile(
+							c.GetWorkDir().String(),
+							[]byte{0},
+							0400,
+						)
 					},
-				}}, nil, pkg.Checksum{}, errors.New("non-file artifact produced regular file")},
+				}}, nil, pkg.Checksum{}, errors.New(
+					"non-file artifact produced regular file",
+				)},
 			})
 
 			wantErrScrub := &pkg.ScrubError{
diff --git a/internal/pkg/tar.go b/internal/pkg/tar.go
index f058d24e..0d1c5724 100644
--- a/internal/pkg/tar.go
+++ b/internal/pkg/tar.go
@@ -69,12 +69,13 @@ func (e DisallowedTypeflagError) Error() string {
 }
 
 // Cure cures the [Artifact], producing a directory located at work.
-func (a *tarArtifact) Cure(work, temp *check.Absolute, loadData CacheDataFunc) (err error) {
+func (a *tarArtifact) Cure(c *CureContext) (err error) {
+	temp := c.GetTempDir()
 	var tr io.ReadCloser
 
 	{
 		var data []byte
-		data, err = loadData(a.f)
+		data, err = c.LoadData(a.f)
 		if err != nil {
 			return
 		}
@@ -209,9 +210,9 @@ func (a *tarArtifact) Cure(work, temp *check.Absolute, loadData CacheDataFunc) (
 		if err = os.Chmod(p.String(), 0700); err != nil {
 			return
 		}
-		err = os.Rename(p.String(), work.String())
+		err = os.Rename(p.String(), c.GetWorkDir().String())
 	} else {
-		err = os.Rename(temp.String(), work.String())
+		err = os.Rename(temp.String(), c.GetWorkDir().String())
 	}
 	return
 }