commit 35b352afb0d8b9e0e3ad89afdacc231e1fbfe3b5
Author: Jae Kwon <jkwon.work@gmail.com>
Date:   Mon May 19 20:46:41 2014 -0700

    First iteration of the immutable AVL tree

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 000000000..1377554eb
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.swp
diff --git a/README.md b/README.md
new file mode 100644
index 000000000..398ccfb63
--- /dev/null
+++ b/README.md
@@ -0,0 +1 @@
+TenderMint - proof of concept
diff --git a/merkle/iavl.go b/merkle/iavl.go
new file mode 100644
index 000000000..d360339b7
--- /dev/null
+++ b/merkle/iavl.go
@@ -0,0 +1,355 @@
+package merkle
+
+import (
+    "hash"
+    "crypto/sha256"
+)
+
+// Immutable AVL Tree (wraps the Node root)
+
+type IAVLTree struct {
+    root *IAVLNode
+}
+
+func NewIAVLTree() *IAVLTree {
+    return &IAVLTree{}
+}
+
+func (self *IAVLTree) Root() Node {
+    return self.root.Copy(true)
+}
+
+func (self *IAVLTree) Size() int {
+    return self.root.Size()
+}
+
+func (self *IAVLTree) Has(key Sortable) bool {
+    return self.root.Has(key)
+}
+
+func (self *IAVLTree) Put(key Sortable, value interface{}) (err error) {
+    self.root, _ = self.root.Put(key, value)
+    return nil
+}
+
+func (self *IAVLTree) Get(key Sortable) (value interface{}, err error) {
+    return self.root.Get(key)
+}
+
+func (self *IAVLTree) Remove(key Sortable) (value interface{}, err error) {
+    new_root, value, err := self.root.Remove(key)
+    if err != nil {
+        return nil, err
+    }
+    self.root = new_root
+    return value, nil
+}
+
+// Node
+
+type IAVLNode struct {
+    key     Sortable
+    value   interface{}
+    height  int
+    hash    []byte
+    left    *IAVLNode
+    right   *IAVLNode
+}
+
+func (self *IAVLNode) Copy(copyHash bool) *IAVLNode {
+    if self == nil {
+        return nil
+    }
+    var hash []byte
+    if copyHash {
+        hash = self.hash
+    }
+    return &IAVLNode{
+        key:    self.key,
+        value:  self.value,
+        height: self.height,
+        hash:   hash,
+        left:   self.left,
+        right:  self.right,
+    }
+}
+
+func (self *IAVLNode) Has(key Sortable) (has bool) {
+    if self == nil {
+        return false
+    }
+    if self.key.Equals(key) {
+        return true
+    } else if key.Less(self.key) {
+        return self.left.Has(key)
+    } else {
+        return self.right.Has(key)
+    }
+}
+
+func (self *IAVLNode) Get(key Sortable) (value interface{}, err error) {
+    if self == nil {
+        return nil, NotFound(key)
+    }
+    if self.key.Equals(key) {
+        return self.value, nil
+    } else if key.Less(self.key) {
+        return self.left.Get(key)
+    } else {
+        return self.right.Get(key)
+    }
+}
+
+// Copies and pops node from the tree.
+// Returns a new tree (unless node is the root) & new (popped) node.
+func (self *IAVLNode) pop_node(node *IAVLNode) (new_self, new_node *IAVLNode) {
+    if node == nil {
+        panic("node can't be nil")
+    } else if node.left != nil && node.right != nil {
+        panic("node must not have both left and right")
+    }
+
+    if self == nil {
+        return nil, node.Copy(true)
+    } else if self == node {
+        var n *IAVLNode
+        if node.left != nil {
+            n = node.left
+        } else if node.right != nil {
+            n = node.right
+        } else {
+            n = nil
+        }
+        node = node.Copy(false)
+        node.left = nil
+        node.right = nil
+        return n, node
+    }
+
+    self = self.Copy(false)
+
+    if node.key.Less(self.key) {
+        self.left, node = self.left.pop_node(node)
+    } else {
+        self.right, node = self.right.pop_node(node)
+    }
+
+    self.height = max(self.left.Height(), self.right.Height()) + 1
+    return self, node
+}
+
+// Pushes the node to the tree, returns a new tree
+func (self *IAVLNode) push_node(node *IAVLNode) *IAVLNode {
+    if node == nil {
+        panic("node can't be nil")
+    } else if node.left != nil || node.right != nil {
+        panic("node must now be a leaf")
+    }
+
+    self = self.Copy(false)
+
+    if self == nil {
+        node.height = 1
+        return node
+    } else if node.key.Less(self.key) {
+        self.left = self.left.push_node(node)
+    } else {
+        self.right = self.right.push_node(node)
+    }
+    self.height = max(self.left.Height(), self.right.Height()) + 1
+    return self
+}
+
+func (self *IAVLNode) rotate_right() *IAVLNode {
+    if self == nil {
+        return self
+    }
+    if self.left == nil {
+        return self
+    }
+    return self.rotate(self.left.rmd)
+}
+
+func (self *IAVLNode) rotate_left() *IAVLNode {
+    if self == nil {
+        return self
+    }
+    if self.right == nil {
+        return self
+    }
+    return self.rotate(self.right.lmd)
+}
+
+func (self *IAVLNode) rotate(get_new_root func() *IAVLNode) *IAVLNode {
+    self, new_root := self.pop_node(get_new_root())
+    new_root.left = self.left
+    new_root.right = self.right
+    self.hash = nil
+    self.left = nil
+    self.right = nil
+    return new_root.push_node(self)
+}
+
+func (self *IAVLNode) balance() *IAVLNode {
+    if self == nil {
+        return self
+    }
+    for abs(self.left.Height() - self.right.Height()) > 2 {
+        if self.left.Height() > self.right.Height() {
+            self = self.rotate_right()
+        } else {
+            self = self.rotate_left()
+        }
+    }
+    return self
+}
+
+// TODO: don't clear the hash if the value hasn't changed.
+func (self *IAVLNode) Put(key Sortable, value interface{}) (_ *IAVLNode, updated bool) {
+    if self == nil {
+        return &IAVLNode{key: key, value: value, height: 1, hash: nil}, false
+    }
+
+    self = self.Copy(false)
+
+    if self.key.Equals(key) {
+        self.value = value
+        return self, true
+    }
+
+    if key.Less(self.key) {
+        self.left, updated = self.left.Put(key, value)
+    } else {
+        self.right, updated = self.right.Put(key, value)
+    }
+    self.height = max(self.left.Height(), self.right.Height()) + 1
+
+    if !updated {
+        self.height += 1
+        return self.balance(), updated
+    }
+    return self, updated
+}
+
+func (self *IAVLNode) Remove(key Sortable) (_ *IAVLNode, value interface{}, err error) {
+    if self == nil {
+        return nil, nil, NotFound(key)
+    }
+
+    if self.key.Equals(key) {
+        if self.left != nil && self.right != nil {
+            var new_root *IAVLNode
+            if self.left.Size() < self.right.Size() {
+                self, new_root = self.pop_node(self.right.lmd())
+            } else {
+                self, new_root = self.pop_node(self.left.rmd())
+            }
+            new_root.left = self.left
+            new_root.right = self.right
+            return new_root, self.value, nil
+        } else if self.left == nil {
+            return self.right, self.value, nil
+        } else if self.right == nil {
+            return self.left, self.value, nil
+        } else {
+            return nil, self.value, nil
+        }
+    }
+
+    self = self.Copy(true)
+
+    if key.Less(self.key) {
+        self.left, value, err = self.left.Remove(key)
+    } else {
+        self.right, value, err = self.right.Remove(key)
+    }
+    if err == nil {
+        self.hash = nil
+        self.height = max(self.left.Height(), self.right.Height()) + 1
+        return self.balance(), value, err
+    } else {
+        return self, value, err
+    }
+}
+
+func (self *IAVLNode) Height() int {
+    if self == nil {
+        return 0
+    }
+    return self.height
+}
+
+func (self *IAVLNode) Size() int {
+    if self == nil {
+        return 0
+    }
+    return 1 + self.left.Size() + self.right.Size()
+}
+
+
+func (self *IAVLNode) Key() Sortable {
+    return self.key
+}
+
+func (self *IAVLNode) Value() interface{} {
+    return self.value
+}
+
+func (self *IAVLNode) Left() Node {
+    if self.left == nil {
+        return nil
+    }
+    return self.left
+}
+
+func (self *IAVLNode) Right() Node {
+    if self.right == nil {
+        return nil
+    }
+    return self.right
+}
+
+// ...
+
+func (self *IAVLNode) _md(side func(*IAVLNode)*IAVLNode) (*IAVLNode) {
+    if self == nil {
+        return nil
+    } else if side(self) != nil {
+        return side(self)._md(side)
+    } else {
+        return self
+    }
+}
+
+func (self *IAVLNode) lmd() (*IAVLNode) {
+    return self._md(func(node *IAVLNode)*IAVLNode { return node.left })
+}
+
+func (self *IAVLNode) rmd() (*IAVLNode) {
+    return self._md(func(node *IAVLNode)*IAVLNode { return node.right })
+}
+
+func abs(i int) int {
+    if i < 0 {
+        return -i
+    }
+    return i
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+// Calculate the hash of hasher over buf.
+func CalcHash(buf []byte, hasher hash.Hash) []byte {
+    hasher.Write(buf)
+    return hasher.Sum(nil)
+}
+
+// calculate hash256 which is sha256(sha256(data))
+func CalcSha256(buf []byte) []byte {
+    return CalcHash(buf, sha256.New())
+}
diff --git a/merkle/iavl_test.go b/merkle/iavl_test.go
new file mode 100644
index 000000000..47f149c06
--- /dev/null
+++ b/merkle/iavl_test.go
@@ -0,0 +1,200 @@
+package merkle
+
+import "testing"
+
+import (
+    "os"
+    "bytes"
+    "math/rand"
+    "encoding/binary"
+)
+
+
+func init() {
+    if urandom, err := os.Open("/dev/urandom"); err != nil {
+        return
+    } else {
+        buf := make([]byte, 8)
+        if _, err := urandom.Read(buf); err == nil {
+            buf_reader := bytes.NewReader(buf)
+            if seed, err := binary.ReadVarint(buf_reader); err == nil {
+                rand.Seed(seed)
+            }
+        }
+        urandom.Close()
+    }
+}
+
+func randstr(length int) String {
+    if urandom, err := os.Open("/dev/urandom"); err != nil {
+        panic(err)
+    } else {
+        slice := make([]byte, length)
+        if _, err := urandom.Read(slice); err != nil {
+            panic(err)
+        }
+        urandom.Close()
+        return String(slice)
+    }
+    panic("unreachable")
+}
+
+func TestImmutableAvlPutHasGetRemove(t *testing.T) {
+
+    type record struct {
+        key String
+        value String
+    }
+
+    records := make([]*record, 400)
+    var tree *IAVLNode
+    var err error
+    var val interface{}
+    var updated bool
+
+    ranrec := func() *record {
+        return &record{ randstr(20), randstr(20) }
+    }
+
+    for i := range records {
+        r := ranrec()
+        records[i] = r
+        tree, updated = tree.Put(r.key, String(""))
+        if updated {
+            t.Error("should have not been updated")
+        }
+        tree, updated = tree.Put(r.key, r.value)
+        if !updated {
+            t.Error("should have been updated")
+        }
+        if tree.Size() != (i+1) {
+            t.Error("size was wrong", tree.Size(), i+1)
+        }
+    }
+
+    for _, r := range records {
+        if has := tree.Has(r.key); !has {
+            t.Error("Missing key")
+        }
+        if has := tree.Has(randstr(12)); has {
+            t.Error("Table has extra key")
+        }
+        if val, err := tree.Get(r.key); err != nil {
+            t.Error(err, val.(String), r.value)
+        } else if !(val.(String)).Equals(r.value) {
+            t.Error("wrong value")
+        }
+    }
+
+    for i, x := range records {
+        if tree, val, err = tree.Remove(x.key); err != nil {
+            t.Error(err)
+        } else if !(val.(String)).Equals(x.value) {
+            t.Error("wrong value")
+        }
+        for _, r := range records[i+1:] {
+            if has := tree.Has(r.key); !has {
+                t.Error("Missing key")
+            }
+            if has := tree.Has(randstr(12)); has {
+                t.Error("Table has extra key")
+            }
+            if val, err := tree.Get(r.key); err != nil {
+                t.Error(err)
+            } else if !(val.(String)).Equals(r.value) {
+                t.Error("wrong value")
+            }
+        }
+        if tree.Size() != (len(records) - (i+1)) {
+            t.Error("size was wrong", tree.Size(), (len(records) - (i+1)))
+        }
+    }
+}
+
+
+func BenchmarkImmutableAvlTree(b *testing.B) {
+    b.StopTimer()
+
+    type record struct {
+        key String
+        value String
+    }
+
+    records := make([]*record, 100)
+
+    ranrec := func() *record {
+        return &record{ randstr(20), randstr(20) }
+    }
+
+    for i := range records {
+        records[i] = ranrec()
+    }
+
+    b.StartTimer()
+    for i := 0; i < b.N; i++ {
+        t := NewIAVLTree()
+        for _, r := range records {
+            t.Put(r.key, r.value)
+        }
+        for _, r := range records {
+            t.Remove(r.key)
+        }
+    }
+}
+
+
+func TestTraversals(t *testing.T) {
+    var data []int = []int{
+        1, 5, 7, 9, 12, 13, 17, 18, 19, 20,
+    }
+    var order []int = []int{
+        6, 1, 8, 2, 4 , 9 , 5 , 7 , 0 , 3 ,
+    }
+    /*
+    var preorder []int = []int {
+        17, 7, 5, 1, 12, 9, 13, 19, 18, 20,
+    }
+    var postorder []int = []int {
+        1, 5, 9, 13, 12, 7, 18, 20, 19, 17,
+    }
+    */
+
+    test := func(T Tree) {
+        t.Logf("%T", T)
+        for j := range order {
+            if err := T.Put(Int(data[order[j]]), order[j]); err != nil {
+                t.Error(err)
+            }
+        }
+
+        j := 0
+        for
+          tn, next := Iterator(T.Root())();
+          next != nil;
+          tn, next = next () {
+            if int(tn.Key().(Int)) != data[j] {
+                t.Error("key in wrong spot in-order")
+            }
+            j += 1
+        }
+
+        /*
+        j = 0
+        for tn, next := tree.TraverseTreePreOrder(T.Root())(); next != nil; tn, next = next () {
+            if int(tn.Key().(Int)) != preorder[j] {
+                t.Error("key in wrong spot pre-order")
+            }
+            j += 1
+        }
+
+        j = 0
+        for tn, next := tree.TraverseTreePostOrder(T.Root())(); next != nil; tn, next = next () {
+            if int(tn.Key().(Int)) != postorder[j] {
+                t.Error("key in wrong spot post-order")
+            }
+            j += 1
+        }
+        */
+    }
+    test(NewIAVLTree())
+}
diff --git a/merkle/int.go b/merkle/int.go
new file mode 100644
index 000000000..26115a96c
--- /dev/null
+++ b/merkle/int.go
@@ -0,0 +1,225 @@
+package merkle
+
+
+type Int8 int8
+type UInt8 uint8
+type Int16 int16
+type UInt16 uint16
+type Int32 int32
+type UInt32 uint32
+type Int64 int64
+type UInt64 uint64
+type Int int
+type UInt uint
+
+
+func (self Int8) Equals(other Sortable) bool {
+    if o, ok := other.(Int8); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self Int8) Less(other Sortable) bool {
+    if o, ok := other.(Int8); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self Int8) Hash() int {
+    return int(self)
+}
+
+
+func (self UInt8) Equals(other Sortable) bool {
+    if o, ok := other.(UInt8); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self UInt8) Less(other Sortable) bool {
+    if o, ok := other.(UInt8); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self UInt8) Hash() int {
+    return int(self)
+}
+
+
+func (self Int16) Equals(other Sortable) bool {
+    if o, ok := other.(Int16); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self Int16) Less(other Sortable) bool {
+    if o, ok := other.(Int16); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self Int16) Hash() int {
+    return int(self)
+}
+
+
+func (self UInt16) Equals(other Sortable) bool {
+    if o, ok := other.(UInt16); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self UInt16) Less(other Sortable) bool {
+    if o, ok := other.(UInt16); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self UInt16) Hash() int {
+    return int(self)
+}
+
+
+func (self Int32) Equals(other Sortable) bool {
+    if o, ok := other.(Int32); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self Int32) Less(other Sortable) bool {
+    if o, ok := other.(Int32); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self Int32) Hash() int {
+    return int(self)
+}
+
+
+func (self UInt32) Equals(other Sortable) bool {
+    if o, ok := other.(UInt32); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self UInt32) Less(other Sortable) bool {
+    if o, ok := other.(UInt32); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self UInt32) Hash() int {
+    return int(self)
+}
+
+
+func (self Int64) Equals(other Sortable) bool {
+    if o, ok := other.(Int64); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self Int64) Less(other Sortable) bool {
+    if o, ok := other.(Int64); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self Int64) Hash() int {
+    return int(self>>32) ^ int(self)
+}
+
+
+func (self UInt64) Equals(other Sortable) bool {
+    if o, ok := other.(UInt64); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self UInt64) Less(other Sortable) bool {
+    if o, ok := other.(UInt64); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self UInt64) Hash() int {
+    return int(self>>32) ^ int(self)
+}
+
+
+func (self Int) Equals(other Sortable) bool {
+    if o, ok := other.(Int); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self Int) Less(other Sortable) bool {
+    if o, ok := other.(Int); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self Int) Hash() int {
+    return int(self)
+}
+
+
+func (self UInt) Equals(other Sortable) bool {
+    if o, ok := other.(UInt); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self UInt) Less(other Sortable) bool {
+    if o, ok := other.(UInt); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self UInt) Hash() int {
+    return int(self)
+}
+
+
diff --git a/merkle/string.go b/merkle/string.go
new file mode 100644
index 000000000..e497f0282
--- /dev/null
+++ b/merkle/string.go
@@ -0,0 +1,57 @@
+package merkle
+
+import "bytes"
+
+type String string
+type ByteSlice []byte
+
+func (self String) Equals(other Sortable) bool {
+    if o, ok := other.(String); ok {
+        return self == o
+    } else {
+        return false
+    }
+}
+
+func (self String) Less(other Sortable) bool {
+    if o, ok := other.(String); ok {
+        return self < o
+    } else {
+        return false
+    }
+}
+
+func (self String) Hash() int {
+    bytes := []byte(self)
+    hash := 0
+    for i, c := range bytes {
+        hash += (i+1)*int(c)
+    }
+    return hash
+}
+
+func (self ByteSlice) Equals(other Sortable) bool {
+    if o, ok := other.(ByteSlice); ok {
+        return bytes.Equal(self, o)
+    } else {
+        return false
+    }
+}
+
+func (self ByteSlice) Less(other Sortable) bool {
+    if o, ok := other.(ByteSlice); ok {
+        return bytes.Compare(self, o) < 0 // -1 if a < b
+    } else {
+        return false
+    }
+}
+
+func (self ByteSlice) Hash() int {
+    hash := 0
+    for i, c := range self {
+        hash += (i+1)*int(c)
+    }
+    return hash
+}
+
+
diff --git a/merkle/tree.go b/merkle/tree.go
new file mode 100644
index 000000000..e694e6f02
--- /dev/null
+++ b/merkle/tree.go
@@ -0,0 +1,30 @@
+package merkle
+
+func Iterator(node Node) NodeIterator {
+    stack := make([]Node, 0, 10)
+    var cur Node = node
+    var tn_iterator NodeIterator
+    tn_iterator = func()(tn Node, next NodeIterator) {
+        if len(stack) > 0 || cur != nil {
+            for cur != nil {
+                stack = append(stack, cur)
+                cur = cur.Left()
+            }
+            stack, cur = pop(stack)
+            tn = cur
+            cur = cur.Right()
+            return tn, tn_iterator
+        } else {
+            return nil, nil
+        }
+    }
+    return tn_iterator
+}
+
+func pop(stack []Node) ([]Node, Node) {
+    if len(stack) <= 0 {
+        return stack, nil
+    } else {
+        return stack[0:len(stack)-1], stack[len(stack)-1]
+    }
+}
diff --git a/merkle/types.go b/merkle/types.go
new file mode 100644
index 000000000..606b0f037
--- /dev/null
+++ b/merkle/types.go
@@ -0,0 +1,38 @@
+package merkle
+
+import (
+    "fmt"
+)
+
+type Sortable interface {
+    Equals(b Sortable) bool
+    Less(b Sortable) bool
+}
+
+type Tree interface {
+    Root() Node
+
+    Size() int
+    Has(key Sortable) bool
+    Get(key Sortable) (value interface{}, err error)
+
+    Put(key Sortable, value interface{}) (err error)
+    Remove(key Sortable) (value interface{}, err error)
+}
+
+type Node interface {
+    Key() Sortable
+    Value() interface{}
+    Left() Node
+    Right() Node
+
+    Size() int
+    Has(key Sortable) bool
+    Get(key Sortable) (value interface{}, err error)
+}
+
+type NodeIterator func() (node Node, next NodeIterator)
+
+func NotFound(key Sortable) error {
+    return fmt.Errorf("Key was not found.")
+}