reachability: Split walk files

9 files changed, 342 insertions, 299 deletions

diff --git a/reachability/walk.go b/reachability/walk.go
index 4611e46e..13400e89 100644
--- a/reachability/walk.go
+++ b/reachability/walk.go
@@ -1,14 +1,7 @@
 package reachability
 
 import (
-	"errors"
-	"fmt"
-	"iter"
-
-	"codeberg.org/lindenii/furgit/format/commitgraph"
-	"codeberg.org/lindenii/furgit/object"
 	"codeberg.org/lindenii/furgit/objectid"
-	"codeberg.org/lindenii/furgit/objecttype"
 )
 
 // Walk is one single-use iterator-style traversal.
@@ -22,295 +15,3 @@ type Walk struct {
 	seqUsed bool
 	err     error
 }
-
-// Seq returns the traversal sequence. It is single-use.
-func (walk *Walk) Seq() iter.Seq[objectid.ObjectID] {
-	if walk.seqUsed {
-		return func(yield func(objectid.ObjectID) bool) {
-			_ = yield
-
-			if walk.err == nil {
-				walk.err = errors.New("reachability: walk sequence already consumed")
-			}
-		}
-	}
-
-	walk.seqUsed = true
-
-	return func(yield func(objectid.ObjectID) bool) {
-		if walk.err != nil {
-			return
-		}
-
-		stack := walk.initialStack()
-
-		var err error
-
-		visited := make(map[objectid.ObjectID]struct{}, len(stack))
-		for len(stack) > 0 {
-			item := stack[len(stack)-1]
-			stack = stack[:len(stack)-1]
-
-			if containsOID(walk.haves, item.id) {
-				continue
-			}
-
-			if _, ok := visited[item.id]; ok {
-				continue
-			}
-
-			visited[item.id] = struct{}{}
-
-			var next []walkItem
-
-			next, err = walk.expand(item)
-			if err != nil {
-				walk.err = err
-
-				return
-			}
-
-			if !yield(item.id) {
-				return
-			}
-
-			stack = append(stack, next...)
-		}
-	}
-}
-
-// Err returns the terminal error, if any, once Seq has been consumed.
-func (walk *Walk) Err() error {
-	return walk.err
-}
-
-type walkItem struct {
-	id   objectid.ObjectID
-	want objecttype.Type
-}
-
-func (walk *Walk) initialStack() []walkItem {
-	if len(walk.wants) == 0 {
-		return nil
-	}
-
-	stack := make([]walkItem, 0, len(walk.wants))
-	for want := range walk.wants {
-		stack = append(stack, walkItem{id: want, want: objecttype.TypeInvalid})
-	}
-
-	return stack
-}
-
-func (walk *Walk) expand(item walkItem) ([]walkItem, error) {
-	if walk.domain == DomainCommits {
-		return walk.expandCommits(item)
-	}
-
-	return walk.expandObjects(item)
-}
-
-func (walk *Walk) expandCommits(item walkItem) ([]walkItem, error) {
-	if walk.reachability.graph != nil { //nolint:nestif
-		next, graphUsed, err := walk.expandCommitsFromGraph(item.id)
-		if err != nil {
-			return nil, err
-		}
-
-		if graphUsed && walk.strict {
-			err = walk.validateCommitObject(item.id)
-			if err != nil {
-				return nil, err
-			}
-		}
-
-		if graphUsed {
-			return next, nil
-		}
-	}
-
-	ty, err := walk.readHeaderType(item.id)
-	if err != nil {
-		return nil, err
-	}
-
-	switch ty {
-	case objecttype.TypeCommit:
-		content, err := walk.readBytesContent(item.id)
-		if err != nil {
-			return nil, err
-		}
-
-		commit, err := object.ParseCommit(content, item.id.Algorithm())
-		if err != nil {
-			return nil, err
-		}
-
-		next := make([]walkItem, 0, len(commit.Parents))
-		for _, parent := range commit.Parents {
-			next = append(next, walkItem{id: parent, want: objecttype.TypeInvalid})
-		}
-
-		return next, nil
-	case objecttype.TypeTag:
-		content, err := walk.readBytesContent(item.id)
-		if err != nil {
-			return nil, err
-		}
-
-		tag, err := object.ParseTag(content, item.id.Algorithm())
-		if err != nil {
-			return nil, err
-		}
-
-		return []walkItem{{id: tag.Target, want: objecttype.TypeInvalid}}, nil
-	case objecttype.TypeTree, objecttype.TypeBlob, objecttype.TypeInvalid,
-		objecttype.TypeFuture, objecttype.TypeOfsDelta, objecttype.TypeRefDelta:
-		return nil, &ErrObjectType{OID: item.id, Got: ty, Want: objecttype.TypeCommit}
-	}
-
-	return nil, fmt.Errorf("reachability: unreachable object type %d", ty)
-}
-
-func (walk *Walk) validateCommitObject(id objectid.ObjectID) error {
-	ty, err := walk.readHeaderType(id)
-	if err != nil {
-		return err
-	}
-
-	if ty != objecttype.TypeCommit {
-		return &ErrObjectType{OID: id, Got: ty, Want: objecttype.TypeCommit}
-	}
-
-	content, err := walk.readBytesContent(id)
-	if err != nil {
-		return err
-	}
-
-	_, err = object.ParseCommit(content, id.Algorithm())
-
-	return err
-}
-
-func (walk *Walk) expandCommitsFromGraph(id objectid.ObjectID) ([]walkItem, bool, error) {
-	pos, err := walk.reachability.graph.Lookup(id)
-	if err != nil {
-		var notFound *commitgraph.ErrNotFound
-		if errors.As(err, &notFound) {
-			return nil, false, nil
-		}
-
-		return nil, true, err
-	}
-
-	commit, err := walk.reachability.graph.CommitAt(pos)
-	if err != nil {
-		return nil, true, err
-	}
-
-	next := make([]walkItem, 0, 2+len(commit.ExtraParents))
-
-	if commit.Parent1.Valid {
-		parentOID, err := walk.reachability.graph.OIDAt(commit.Parent1.Pos)
-		if err != nil {
-			return nil, true, err
-		}
-
-		next = append(next, walkItem{id: parentOID, want: objecttype.TypeInvalid})
-	}
-
-	if commit.Parent2.Valid {
-		parentOID, err := walk.reachability.graph.OIDAt(commit.Parent2.Pos)
-		if err != nil {
-			return nil, true, err
-		}
-
-		next = append(next, walkItem{id: parentOID, want: objecttype.TypeInvalid})
-	}
-
-	for _, parentPos := range commit.ExtraParents {
-		parentOID, err := walk.reachability.graph.OIDAt(parentPos)
-		if err != nil {
-			return nil, true, err
-		}
-
-		next = append(next, walkItem{id: parentOID, want: objecttype.TypeInvalid})
-	}
-
-	return next, true, nil
-}
-
-func (walk *Walk) expandObjects(item walkItem) ([]walkItem, error) {
-	ty, err := walk.readHeaderType(item.id)
-	if err != nil {
-		return nil, err
-	}
-
-	if item.want != objecttype.TypeInvalid && ty != item.want {
-		return nil, &ErrObjectType{OID: item.id, Got: ty, Want: item.want}
-	}
-
-	switch ty {
-	case objecttype.TypeBlob:
-		return nil, nil
-	case objecttype.TypeCommit:
-		content, err := walk.readBytesContent(item.id)
-		if err != nil {
-			return nil, err
-		}
-
-		commit, err := object.ParseCommit(content, item.id.Algorithm())
-		if err != nil {
-			return nil, err
-		}
-
-		next := make([]walkItem, 0, len(commit.Parents)+1)
-
-		next = append(next, walkItem{id: commit.Tree, want: objecttype.TypeTree})
-		for _, parent := range commit.Parents {
-			next = append(next, walkItem{id: parent, want: objecttype.TypeCommit})
-		}
-
-		return next, nil
-	case objecttype.TypeTree:
-		content, err := walk.readBytesContent(item.id)
-		if err != nil {
-			return nil, err
-		}
-
-		tree, err := object.ParseTree(content, item.id.Algorithm())
-		if err != nil {
-			return nil, err
-		}
-
-		next := make([]walkItem, 0, len(tree.Entries))
-		for _, entry := range tree.Entries {
-			switch entry.Mode {
-			case object.FileModeGitlink:
-				continue
-			case object.FileModeDir:
-				next = append(next, walkItem{id: entry.ID, want: objecttype.TypeTree})
-			case object.FileModeRegular, object.FileModeExecutable, object.FileModeSymlink:
-				next = append(next, walkItem{id: entry.ID, want: objecttype.TypeBlob})
-			}
-		}
-
-		return next, nil
-	case objecttype.TypeTag:
-		content, err := walk.readBytesContent(item.id)
-		if err != nil {
-			return nil, err
-		}
-
-		tag, err := object.ParseTag(content, item.id.Algorithm())
-		if err != nil {
-			return nil, err
-		}
-
-		return []walkItem{{id: tag.Target, want: tag.TargetType}}, nil
-	case objecttype.TypeInvalid, objecttype.TypeFuture, objecttype.TypeOfsDelta, objecttype.TypeRefDelta:
-		return nil, &ErrObjectType{OID: item.id, Got: ty, Want: item.want}
-	}
-
-	return nil, fmt.Errorf("reachability: unreachable object type %d", ty)
-}
diff --git a/reachability/walk_expand.go b/reachability/walk_expand.go
new file mode 100644
index 00000000..e36534a2
--- /dev/null
+++ b/reachability/walk_expand.go
@@ -0,0 +1,9 @@
+package reachability
+
+func (walk *Walk) expand(item walkItem) ([]walkItem, error) {
+	if walk.domain == DomainCommits {
+		return walk.expandCommits(item)
+	}
+
+	return walk.expandObjects(item)
+}
diff --git a/reachability/walk_expand_commits.go b/reachability/walk_expand_commits.go
new file mode 100644
index 00000000..11c5c692
--- /dev/null
+++ b/reachability/walk_expand_commits.go
@@ -0,0 +1,70 @@
+package reachability
+
+import (
+	"fmt"
+
+	"codeberg.org/lindenii/furgit/object"
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+func (walk *Walk) expandCommits(item walkItem) ([]walkItem, error) {
+	if walk.reachability.graph != nil { //nolint:nestif
+		next, graphUsed, err := walk.expandCommitsFromGraph(item.id)
+		if err != nil {
+			return nil, err
+		}
+
+		if graphUsed && walk.strict {
+			err = walk.validateCommitObject(item.id)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		if graphUsed {
+			return next, nil
+		}
+	}
+
+	ty, err := walk.readHeaderType(item.id)
+	if err != nil {
+		return nil, err
+	}
+
+	switch ty {
+	case objecttype.TypeCommit:
+		content, err := walk.readBytesContent(item.id)
+		if err != nil {
+			return nil, err
+		}
+
+		commit, err := object.ParseCommit(content, item.id.Algorithm())
+		if err != nil {
+			return nil, err
+		}
+
+		next := make([]walkItem, 0, len(commit.Parents))
+		for _, parent := range commit.Parents {
+			next = append(next, walkItem{id: parent, want: objecttype.TypeInvalid})
+		}
+
+		return next, nil
+	case objecttype.TypeTag:
+		content, err := walk.readBytesContent(item.id)
+		if err != nil {
+			return nil, err
+		}
+
+		tag, err := object.ParseTag(content, item.id.Algorithm())
+		if err != nil {
+			return nil, err
+		}
+
+		return []walkItem{{id: tag.Target, want: objecttype.TypeInvalid}}, nil
+	case objecttype.TypeTree, objecttype.TypeBlob, objecttype.TypeInvalid,
+		objecttype.TypeFuture, objecttype.TypeOfsDelta, objecttype.TypeRefDelta:
+		return nil, &ErrObjectType{OID: item.id, Got: ty, Want: objecttype.TypeCommit}
+	}
+
+	return nil, fmt.Errorf("reachability: unreachable object type %d", ty)
+}
diff --git a/reachability/walk_expand_commits_graph.go b/reachability/walk_expand_commits_graph.go
new file mode 100644
index 00000000..15780c8e
--- /dev/null
+++ b/reachability/walk_expand_commits_graph.go
@@ -0,0 +1,57 @@
+package reachability
+
+import (
+	"errors"
+
+	"codeberg.org/lindenii/furgit/format/commitgraph"
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+func (walk *Walk) expandCommitsFromGraph(id objectid.ObjectID) ([]walkItem, bool, error) {
+	pos, err := walk.reachability.graph.Lookup(id)
+	if err != nil {
+		var notFound *commitgraph.ErrNotFound
+		if errors.As(err, &notFound) {
+			return nil, false, nil
+		}
+
+		return nil, true, err
+	}
+
+	commit, err := walk.reachability.graph.CommitAt(pos)
+	if err != nil {
+		return nil, true, err
+	}
+
+	next := make([]walkItem, 0, 2+len(commit.ExtraParents))
+
+	if commit.Parent1.Valid {
+		parentOID, err := walk.reachability.graph.OIDAt(commit.Parent1.Pos)
+		if err != nil {
+			return nil, true, err
+		}
+
+		next = append(next, walkItem{id: parentOID, want: objecttype.TypeInvalid})
+	}
+
+	if commit.Parent2.Valid {
+		parentOID, err := walk.reachability.graph.OIDAt(commit.Parent2.Pos)
+		if err != nil {
+			return nil, true, err
+		}
+
+		next = append(next, walkItem{id: parentOID, want: objecttype.TypeInvalid})
+	}
+
+	for _, parentPos := range commit.ExtraParents {
+		parentOID, err := walk.reachability.graph.OIDAt(parentPos)
+		if err != nil {
+			return nil, true, err
+		}
+
+		next = append(next, walkItem{id: parentOID, want: objecttype.TypeInvalid})
+	}
+
+	return next, true, nil
+}
diff --git a/reachability/walk_expand_objects.go b/reachability/walk_expand_objects.go
new file mode 100644
index 00000000..97cab79c
--- /dev/null
+++ b/reachability/walk_expand_objects.go
@@ -0,0 +1,83 @@
+package reachability
+
+import (
+	"fmt"
+
+	"codeberg.org/lindenii/furgit/object"
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+func (walk *Walk) expandObjects(item walkItem) ([]walkItem, error) {
+	ty, err := walk.readHeaderType(item.id)
+	if err != nil {
+		return nil, err
+	}
+
+	if item.want != objecttype.TypeInvalid && ty != item.want {
+		return nil, &ErrObjectType{OID: item.id, Got: ty, Want: item.want}
+	}
+
+	switch ty {
+	case objecttype.TypeBlob:
+		return nil, nil
+	case objecttype.TypeCommit:
+		content, err := walk.readBytesContent(item.id)
+		if err != nil {
+			return nil, err
+		}
+
+		commit, err := object.ParseCommit(content, item.id.Algorithm())
+		if err != nil {
+			return nil, err
+		}
+
+		next := make([]walkItem, 0, len(commit.Parents)+1)
+
+		next = append(next, walkItem{id: commit.Tree, want: objecttype.TypeTree})
+		for _, parent := range commit.Parents {
+			next = append(next, walkItem{id: parent, want: objecttype.TypeCommit})
+		}
+
+		return next, nil
+	case objecttype.TypeTree:
+		content, err := walk.readBytesContent(item.id)
+		if err != nil {
+			return nil, err
+		}
+
+		tree, err := object.ParseTree(content, item.id.Algorithm())
+		if err != nil {
+			return nil, err
+		}
+
+		next := make([]walkItem, 0, len(tree.Entries))
+		for _, entry := range tree.Entries {
+			switch entry.Mode {
+			case object.FileModeGitlink:
+				continue
+			case object.FileModeDir:
+				next = append(next, walkItem{id: entry.ID, want: objecttype.TypeTree})
+			case object.FileModeRegular, object.FileModeExecutable, object.FileModeSymlink:
+				next = append(next, walkItem{id: entry.ID, want: objecttype.TypeBlob})
+			}
+		}
+
+		return next, nil
+	case objecttype.TypeTag:
+		content, err := walk.readBytesContent(item.id)
+		if err != nil {
+			return nil, err
+		}
+
+		tag, err := object.ParseTag(content, item.id.Algorithm())
+		if err != nil {
+			return nil, err
+		}
+
+		return []walkItem{{id: tag.Target, want: tag.TargetType}}, nil
+	case objecttype.TypeInvalid, objecttype.TypeFuture, objecttype.TypeOfsDelta, objecttype.TypeRefDelta:
+		return nil, &ErrObjectType{OID: item.id, Got: ty, Want: item.want}
+	}
+
+	return nil, fmt.Errorf("reachability: unreachable object type %d", ty)
+}
diff --git a/reachability/walk_item.go b/reachability/walk_item.go
new file mode 100644
index 00000000..7196cf1a
--- /dev/null
+++ b/reachability/walk_item.go
@@ -0,0 +1,11 @@
+package reachability
+
+import (
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+type walkItem struct {
+	id   objectid.ObjectID
+	want objecttype.Type
+}
diff --git a/reachability/walk_seq.go b/reachability/walk_seq.go
new file mode 100644
index 00000000..ad3415d1
--- /dev/null
+++ b/reachability/walk_seq.go
@@ -0,0 +1,69 @@
+package reachability
+
+import (
+	"errors"
+	"iter"
+
+	"codeberg.org/lindenii/furgit/objectid"
+)
+
+// Seq returns the traversal sequence. It is single-use.
+func (walk *Walk) Seq() iter.Seq[objectid.ObjectID] {
+	if walk.seqUsed {
+		return func(yield func(objectid.ObjectID) bool) {
+			_ = yield
+
+			if walk.err == nil {
+				walk.err = errors.New("reachability: walk sequence already consumed")
+			}
+		}
+	}
+
+	walk.seqUsed = true
+
+	return func(yield func(objectid.ObjectID) bool) {
+		if walk.err != nil {
+			return
+		}
+
+		stack := walk.initialStack()
+
+		var err error
+
+		visited := make(map[objectid.ObjectID]struct{}, len(stack))
+		for len(stack) > 0 {
+			item := stack[len(stack)-1]
+			stack = stack[:len(stack)-1]
+
+			if containsOID(walk.haves, item.id) {
+				continue
+			}
+
+			if _, ok := visited[item.id]; ok {
+				continue
+			}
+
+			visited[item.id] = struct{}{}
+
+			var next []walkItem
+
+			next, err = walk.expand(item)
+			if err != nil {
+				walk.err = err
+
+				return
+			}
+
+			if !yield(item.id) {
+				return
+			}
+
+			stack = append(stack, next...)
+		}
+	}
+}
+
+// Err returns the terminal error, if any, once Seq has been consumed.
+func (walk *Walk) Err() error {
+	return walk.err
+}
diff --git a/reachability/walk_stack.go b/reachability/walk_stack.go
new file mode 100644
index 00000000..847ed1c0
--- /dev/null
+++ b/reachability/walk_stack.go
@@ -0,0 +1,16 @@
+package reachability
+
+import "codeberg.org/lindenii/furgit/objecttype"
+
+func (walk *Walk) initialStack() []walkItem {
+	if len(walk.wants) == 0 {
+		return nil
+	}
+
+	stack := make([]walkItem, 0, len(walk.wants))
+	for want := range walk.wants {
+		stack = append(stack, walkItem{id: want, want: objecttype.TypeInvalid})
+	}
+
+	return stack
+}
diff --git a/reachability/walk_verify.go b/reachability/walk_verify.go
new file mode 100644
index 00000000..46798f5a
--- /dev/null
+++ b/reachability/walk_verify.go
@@ -0,0 +1,27 @@
+package reachability
+
+import (
+	"codeberg.org/lindenii/furgit/object"
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+func (walk *Walk) validateCommitObject(id objectid.ObjectID) error {
+	ty, err := walk.readHeaderType(id)
+	if err != nil {
+		return err
+	}
+
+	if ty != objecttype.TypeCommit {
+		return &ErrObjectType{OID: id, Got: ty, Want: objecttype.TypeCommit}
+	}
+
+	content, err := walk.readBytesContent(id)
+	if err != nil {
+		return err
+	}
+
+	_, err = object.ParseCommit(content, id.Algorithm())
+
+	return err
+}