cache tree traversal for both full and meta on disk as json

server/tree.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/json"
 	"io/ioutil"
 	"os"
 	"path"
@@ -65,15 +66,68 @@ func (tree Tree) WithRoot(root string) Tree {
 }
 
 func (tree Tree) GetRootMeta() (Branch, error) {
+	if meta, ok := tree.getCachedRootMeta(); ok {
+		return meta, nil
+	}
 	got, err := tree.getRoot(NewID(""), false, false)
+	if err != nil {
+		return Branch{}, err
+	}
+	tree.cacheRootMeta(got)
 	return got, err
 }
 
 func (tree Tree) GetRoot() (Branch, error) {
+	if root, ok := tree.getCachedRoot(); ok {
+		return root, nil
+	}
 	got, err := tree.getRoot(NewID(""), true, false)
+	if err != nil {
+		return Branch{}, err
+	}
+	tree.cacheRoot(got)
 	return got, err
 }
 
+func (tree Tree) getCachedRoot() (Branch, bool) {
+	return tree.getCachedFrom("root.json")
+}
+
+func (tree Tree) getCachedRootMeta() (Branch, bool) {
+	return tree.getCachedFrom("root_meta.json")
+}
+
+func (tree Tree) getCachedFrom(name string) (Branch, bool) {
+	b, err := ioutil.ReadFile(path.Join(tree.root, name))
+	if err != nil {
+		return Branch{}, false
+	}
+	var branch Branch
+	err = json.Unmarshal(b, &branch)
+	return branch, err == nil
+}
+
+func (tree Tree) cacheRoot(branch Branch) {
+	tree.cacheRootFrom("root.json", branch)
+}
+
+func (tree Tree) cacheRootMeta(branch Branch) {
+	tree.cacheRootFrom("root_meta.json", branch)
+}
+
+func (tree Tree) cacheRootFrom(name string, branch Branch) {
+	b, err := json.Marshal(branch)
+	if err != nil {
+		return
+	}
+	ensureAndWrite(path.Join(tree.root, name), b)
+}
+
+func (tree Tree) cacheClear() {
+	os.Remove(path.Join(path.Join(tree.root, "root.json")))
+	os.Remove(path.Join(path.Join(tree.root, "root_meta.json")))
+}
+
 func (tree Tree) getRoot(pid ID, withContent, withDeleted bool) (Branch, error) {
 	m := Branch{Branches: map[ID]Branch{}}
 	entries, err := os.ReadDir(tree.root)
@@ -121,6 +175,7 @@ func (tree Tree) toData(id ID) string {
 }
 
 func (tree Tree) Put(id ID, input Leaf) error {
+	tree.cacheClear()
 	if _, err := os.Stat(tree.toData(id)); os.IsNotExist(err) {
 		b, err := yaml.Marshal(Leaf{})
 		if err != nil {
@@ -145,6 +200,7 @@ func (tree Tree) Put(id ID, input Leaf) error {
 }
 
 func (tree Tree) Del(id ID) error {
+	tree.cacheClear()
 	got, err := tree.Get(id)
 	if os.IsNotExist(err) {
 		return nil
@@ -160,6 +216,7 @@ func (tree Tree) Del(id ID) error {
 }
 
 func (tree Tree) HardDel(id ID) error {
+	tree.cacheClear()
 	os.RemoveAll(tree.toDir(id))
 	return nil
 }