bolt: refactor extract to separate interface

bolt.go

@@ -0,0 +1,178 @@
+package main
+
+import (
+	"fmt"
+	"path/filepath"
+	"sort"
+	"strings"
+	"time"
+	"unsafe"
+
+	"github.com/ying32/govcl/vcl"
+	"go.etcd.io/bbolt"
+)
+
+type boltLoadedDatabase struct {
+	displayName string
+	path        string
+	db          *bbolt.DB
+	nav         *vcl.TTreeNode
+
+	arena []*navData // keepalive
+}
+
+func (ld *boltLoadedDatabase) DisplayName() string {
+	return ld.displayName
+}
+
+func (ld *boltLoadedDatabase) RootElement() *vcl.TTreeNode {
+	return ld.nav
+}
+
+func (ld *boltLoadedDatabase) Keepalive(ndata *navData) {
+	ld.arena = append(ld.arena, ndata)
+}
+
+func (ld *boltLoadedDatabase) RenderForNav(f *TMainForm, ndata *navData) {
+
+	// Load properties
+
+	bucketDisplayName := strings.Join(ndata.bucketPath, `/`)
+	content := fmt.Sprintf("Selected database: %#v\n\n\nSelected bucket: %q\n", ld.db.Stats(), bucketDisplayName)
+	f.propertiesBox.SetText(content)
+
+	// Load data
+
+	f.contentBox.SetEnabled(false)
+	f.contentBox.Clear()
+
+	err := ld.db.View(func(tx *bbolt.Tx) error {
+		b := boltTargetBucket(tx, ndata.bucketPath)
+		if b == nil {
+			// no such bucket
+			return nil
+		}
+
+		// Valid
+		f.contentBox.Clear()
+
+		c := b.Cursor()
+		for k, v := c.First(); k != nil; k, v = c.Next() {
+			dataEntry := f.contentBox.Items().Add()
+			dataEntry.SetCaption(formatUtf8(k))
+			dataEntry.SubItems().Add(formatUtf8(v))
+		}
+		return nil
+	})
+	if err != nil {
+		vcl.ShowMessage(fmt.Sprintf("Failed to load data for bucket %q: %s", bucketDisplayName, err.Error()))
+		return
+	}
+
+	// Valid
+	f.contentBox.SetEnabled(true)
+}
+
+func (ld *boltLoadedDatabase) NavChildren(ndata *navData) ([]string, error) {
+	// In the bolt implementation, the nav is a recursive tree of child buckets
+	return boltChildBucketNames(ld.db, ndata.bucketPath)
+}
+
+var _ loadedDatabase = &boltLoadedDatabase{} // interface assertion
+
+//
+
+func (f *TMainForm) addDatabaseFromFile(path string) {
+	// TODO load in background thread to stop blocking the UI
+	db, err := bbolt.Open(path, 0644, &bbolt.Options{Timeout: 1 * time.Second})
+	if err != nil {
+		vcl.ShowMessage(fmt.Sprintf("Failed to load database '%s': %s", path, err.Error()))
+		return
+	}
+
+	ld := &boltLoadedDatabase{
+		path:        path,
+		displayName: filepath.Base(path),
+		db:          db,
+	}
+
+	ld.nav = f.Buckets.Items().Add(nil, ld.displayName)
+	ld.nav.SetHasChildren(true) // dynamically populate in OnNavExpanding
+	navData := &navData{
+		ld:             ld,
+		childrenLoaded: false,      // will be loaded dynamically
+		bucketPath:     []string{}, // empty = root
+	}
+	ld.nav.SetData(unsafe.Pointer(navData))
+
+	f.dbs = append(f.dbs, ld)
+
+	ld.Keepalive(navData)
+}
+
+func boltTargetBucket(tx *bbolt.Tx, path []string) *bbolt.Bucket {
+
+	// If we are already deep in buckets, go directly there to find children
+	if len(path) == 0 {
+		return nil
+	}
+
+	b := tx.Bucket([]byte(path[0]))
+	if b == nil {
+		return nil // unexpectedly missing
+	}
+
+	for i := 1; i < len(path); i += 1 {
+		b = b.Bucket([]byte(path[i]))
+		if b == nil {
+			return nil // unexpectedly missing
+		}
+	}
+
+	return b // OK
+}
+
+func boltChildBucketNames(db *bbolt.DB, path []string) ([]string, error) {
+	var nextBucketNames []string
+
+	err := db.View(func(tx *bbolt.Tx) error {
+
+		// If we are already deep in buckets, go directly there to find children
+		if len(path) > 0 {
+			b := tx.Bucket([]byte(path[0]))
+			if b == nil {
+				return fmt.Errorf("Unexpected missing root bucket %q", path[0])
+			}
+
+			for i := 1; i < len(path); i += 1 {
+				b = b.Bucket([]byte(path[i]))
+				if b == nil {
+					return fmt.Errorf("Unexpected missing bucket %q", strings.Join(path[0:i], `/`))
+				}
+			}
+
+			// Find child buckets of this bucket
+			b.ForEachBucket(func(bucketName []byte) error {
+				nextBucketNames = append(nextBucketNames, string(bucketName))
+				return nil
+			})
+
+		} else {
+			// Find root bucket names
+			return tx.ForEach(func(bucketName []byte, _ *bbolt.Bucket) error {
+				nextBucketNames = append(nextBucketNames, string(bucketName))
+				return nil
+			})
+		}
+
+		// OK
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	sort.Strings(nextBucketNames)
+
+	return nextBucketNames, nil
+}

loadedDatabase.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"github.com/ying32/govcl/vcl"
+)
+
+// loadedDatabase is a DB-agnostic interface for each loaded database.
+type loadedDatabase interface {
+	DisplayName() string
+	RootElement() *vcl.TTreeNode
+	RenderForNav(f *TMainForm, ndata *navData)
+	NavChildren(ndata *navData) ([]string, error)
+	Keepalive(ndata *navData)
+}
+
+// navData is the .Data() pointer for each TTreeNode in the left-hand tree.
+type navData struct {
+	ld             loadedDatabase
+	childrenLoaded bool
+	bucketPath     []string
+}

main.go

@@ -2,10 +2,8 @@ package main
 
 import (
 	"fmt"
-	"path/filepath"
+	"os"
-	"sort"
 	"strings"
-	"time"
 	"unicode/utf8"
 	"unsafe"
 
@@ -13,22 +11,8 @@ import (
 	"github.com/ying32/govcl/vcl"
 	"github.com/ying32/govcl/vcl/types"
 
-	"go.etcd.io/bbolt"
 )
 
-type loadedDatabase struct {
-	displayName string
-	path        string
-	db          *bbolt.DB
-	nav         *vcl.TTreeNode
-}
-
-type navData struct {
-	ld             *loadedDatabase
-	childrenLoaded bool
-	bucketPath     []string
-}
-
 type TMainForm struct {
 	*vcl.TForm
 	Menu          *vcl.TMainMenu
@@ -37,8 +21,7 @@ type TMainForm struct {
 	propertiesBox *vcl.TMemo
 	contentBox    *vcl.TListView
 
-	dbs   []loadedDatabase
+	dbs []loadedDatabase
-	arena []*navData // keepalive
 }
 
 var (
@@ -135,43 +118,7 @@ func (f *TMainForm) OnNavChange(sender vcl.IObject, node *vcl.TTreeNode) {
 	}
 
 	ndata := (*navData)(node.Data())
-
+	ndata.ld.RenderForNav(f, ndata) // Handover to the database type's own renderer function
-	// Load properties
-
-	bucketDisplayName := strings.Join(ndata.bucketPath, `/`)
-	content := fmt.Sprintf("Selected database: %#v\n\n\nSelected bucket: %q\n", ndata.ld.db.Stats(), bucketDisplayName)
-	f.propertiesBox.SetText(content)
-
-	// Load data
-
-	f.contentBox.SetEnabled(false)
-	f.contentBox.Clear()
-
-	err := ndata.ld.db.View(func(tx *bbolt.Tx) error {
-		b := boltTargetBucket(tx, ndata.bucketPath)
-		if b == nil {
-			// no such bucket
-			return nil
-		}
-
-		// Valid
-		f.contentBox.Clear()
-
-		c := b.Cursor()
-		for k, v := c.First(); k != nil; k, v = c.Next() {
-			dataEntry := f.contentBox.Items().Add()
-			dataEntry.SetCaption(formatUtf8(k))
-			dataEntry.SubItems().Add(formatUtf8(v))
-		}
-		return nil
-	})
-	if err != nil {
-		vcl.ShowMessage(fmt.Sprintf("Failed to load data for bucket %q: %s", bucketDisplayName, err.Error()))
-		return
-	}
-
-	// Valid
-	f.contentBox.SetEnabled(true)
 }
 
 func formatUtf8(in []byte) string {
@@ -182,73 +129,6 @@ func formatUtf8(in []byte) string {
 	return string(in)
 }
 
-func boltTargetBucket(tx *bbolt.Tx, path []string) *bbolt.Bucket {
-
-	// If we are already deep in buckets, go directly there to find children
-	if len(path) == 0 {
-		return nil
-	}
-
-	b := tx.Bucket([]byte(path[0]))
-	if b == nil {
-		return nil // unexpectedly missing
-	}
-
-	for i := 1; i < len(path); i += 1 {
-		b = b.Bucket([]byte(path[i]))
-		if b == nil {
-			return nil // unexpectedly missing
-		}
-	}
-
-	return b // OK
-}
-
-func boltChildBucketNames(db *bbolt.DB, path []string) ([]string, error) {
-	var nextBucketNames []string
-
-	err := db.View(func(tx *bbolt.Tx) error {
-
-		// If we are already deep in buckets, go directly there to find children
-		if len(path) > 0 {
-			b := tx.Bucket([]byte(path[0]))
-			if b == nil {
-				return fmt.Errorf("Unexpected missing root bucket %q", path[0])
-			}
-
-			for i := 1; i < len(path); i += 1 {
-				b = b.Bucket([]byte(path[i]))
-				if b == nil {
-					return fmt.Errorf("Unexpected missing bucket %q", strings.Join(path[0:i], `/`))
-				}
-			}
-
-			// Find child buckets of this bucket
-			b.ForEachBucket(func(bucketName []byte) error {
-				nextBucketNames = append(nextBucketNames, string(bucketName))
-				return nil
-			})
-
-		} else {
-			// Find root bucket names
-			return tx.ForEach(func(bucketName []byte, _ *bbolt.Bucket) error {
-				nextBucketNames = append(nextBucketNames, string(bucketName))
-				return nil
-			})
-		}
-
-		// OK
-		return nil
-	})
-	if err != nil {
-		return nil, err
-	}
-
-	sort.Strings(nextBucketNames)
-
-	return nextBucketNames, nil
-}
-
 func (f *TMainForm) OnNavExpanding(sender vcl.IObject, node *vcl.TTreeNode, allowExpansion *bool) {
 
 	if node.Data() == nil {
@@ -264,7 +144,7 @@ func (f *TMainForm) OnNavExpanding(sender vcl.IObject, node *vcl.TTreeNode, allo
 	}
 
 	// Find the child buckets from this point under the element
-	nextBucketNames, err := boltChildBucketNames(ndata.ld.db, ndata.bucketPath)
+	nextBucketNames, err := ndata.ld.NavChildren(ndata)
 	if err != nil {
 		vcl.ShowMessage(fmt.Sprintf("Failed to find child buckets under %q: %s", strings.Join(ndata.bucketPath, `/`), err.Error()))
 		*allowExpansion = false
@@ -292,36 +172,10 @@ func (f *TMainForm) OnNavExpanding(sender vcl.IObject, node *vcl.TTreeNode, allo
 			navData.bucketPath = append(navData.bucketPath, ndata.bucketPath...)
 			navData.bucketPath = append(navData.bucketPath, bucketName)
 			node.SetData(unsafe.Pointer(navData))
-			f.arena = append(f.arena, navData) // keepalive
+
+			ndata.ld.Keepalive(navData)
 		}
 
 		*allowExpansion = true
 	}
 }
-
-func (f *TMainForm) addDatabaseFromFile(path string) {
-	// TODO load in background thread to stop blocking the UI
-	db, err := bbolt.Open(path, 0644, &bbolt.Options{Timeout: 1 * time.Second})
-	if err != nil {
-		vcl.ShowMessage(fmt.Sprintf("Failed to load database '%s': %s", path, err.Error()))
-		return
-	}
-
-	entry := loadedDatabase{
-		path:        path,
-		displayName: filepath.Base(path),
-		db:          db,
-	}
-
-	entry.nav = f.Buckets.Items().Add(nil, entry.displayName)
-	entry.nav.SetHasChildren(true) // dynamically populate in OnNavExpanding
-	navData := &navData{
-		ld:             &entry,
-		childrenLoaded: false,      // will be loaded dynamically
-		bucketPath:     []string{}, // empty = root
-	}
-	entry.nav.SetData(unsafe.Pointer(navData))
-
-	f.dbs = append(f.dbs, entry)
-	f.arena = append(f.arena, navData) // keepalive
-}