From f6e1d2bacc24b239e78a1a4b666fb2f7940c12ee Mon Sep 17 00:00:00 2001
From: lash <dev@holbrook.no>
Date: Fri, 31 Mar 2023 17:27:10 +0100
Subject: [PATCH] Add router

---
 draft.txt                |  3 ++
 go/router/router.go      | 80 ++++++++++++++++++++++++++++++++++++
 go/router/router_test.go | 89 ++++++++++++++++++++++++++++++++++++++++
 go/vm/vm.go              |  9 ++++
 4 files changed, 181 insertions(+)
 create mode 100644 go/router/router.go
 create mode 100644 go/router/router_test.go

diff --git a/draft.txt b/draft.txt
index dafddf0..9669e0b 100644
--- a/draft.txt
+++ b/draft.txt
@@ -105,11 +105,14 @@ PREV <selector> <display>
 GOTO <selector> <display> <symbol>
 EXIT <selector> <display>
 COND <selector> <display> <symbol> <[!]state>
+VAL <symbol>
 
 kept in session as a router object:
 
 SELECTORHASH|SYMBOLHASH
 
+Selectorhash 0x0 is VAL
+
 
 ---
 
diff --git a/go/router/router.go b/go/router/router.go
new file mode 100644
index 0000000..9db5915
--- /dev/null
+++ b/go/router/router.go
@@ -0,0 +1,80 @@
+package router
+
+import (
+	"fmt"
+)
+
+type Router struct {
+	selectors []string
+	symbols map[string]string
+}
+
+func NewRouter() Router {
+	return Router{
+		symbols: make(map[string]string),
+	}
+}
+
+func(r *Router) Add(selector string, symbol string) error {
+	if r.symbols[selector] != "" {
+		return fmt.Errorf("selector %v already set to symbol %v", selector, symbol)
+	}
+	l := len(selector)
+	if (l > 255) {
+		return fmt.Errorf("selector too long (is %v, max 255)", l)
+	}
+	l = len(symbol)
+	if (l > 255) {
+		return fmt.Errorf("symbol too long (is %v, max 255)", l)
+	}
+	r.selectors = append(r.selectors, selector)
+	r.symbols[selector] = symbol
+	return nil
+}
+
+func(r *Router) Next() []byte {
+	if len(r.selectors) == 0 {
+		return []byte{}
+	}
+	k := r.selectors[0]
+	r.selectors = r.selectors[1:]
+	v := r.symbols[k]
+	if len(r.selectors) == 0 {
+		r.symbols = nil	
+	} else {
+		delete(r.symbols, k)
+	}
+	lk := len(k)
+	lv := len(v)
+	b := []byte{uint8(lk)}
+	b = append(b, k...)
+	b = append(b, uint8(lv))	
+	b = append(b, v...)
+	return b
+}
+
+func(r *Router) ToBytes() []byte {
+	b := []byte{}
+	for true {
+		v := r.Next()
+		if len(v) == 0 {
+			break
+		}
+		b = append(b, v...)
+	}
+	return b
+}
+
+func FromBytes(b []byte) Router {
+	rb := NewRouter()
+	for len(b) > 0 {
+		l := b[0]
+		k := b[1:1+l]
+		b = b[1+l:]
+		l = b[0]
+		v := b[1:1+l]
+		b = b[1+l:]
+		rb.Add(string(k), string(v))
+	}
+	return rb
+}
diff --git a/go/router/router_test.go b/go/router/router_test.go
new file mode 100644
index 0000000..6cba085
--- /dev/null
+++ b/go/router/router_test.go
@@ -0,0 +1,89 @@
+package router
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestRouter(t *testing.T) {
+	r := NewRouter()
+	err := r.Add("foo", "bar")
+	if err != nil {
+		t.Error(err)
+	}
+	err = r.Add("baz", "barbarbar")
+	if err != nil {
+		t.Error(err)
+	}
+	err = r.Add("foo", "xyzzy")
+	if err == nil {
+		t.Errorf("expected error for duplicate key foo")
+	}
+}
+
+func TestRouterOut(t *testing.T) {
+	rt := NewRouter()
+	err := rt.Add("foo", "inky")
+	if err != nil {
+		t.Error(err)
+	}
+	err = rt.Add("barbar", "pinky")
+	if err != nil {
+		t.Error(err)
+	}
+	err = rt.Add("bazbazbaz", "blinky")
+	if err != nil {
+		t.Error(err)
+	}
+	rb := []byte{}
+	r := rt.Next()
+	expect := append([]byte{0x3}, []byte("foo")...)
+	expect = append(expect, 4)
+	expect = append(expect, []byte("inky")...)
+	if !bytes.Equal(r, expect) {
+		t.Errorf("expected %v, got %v", expect, r)
+	}
+	rb = append(rb, r...)
+
+	r = rt.Next()
+	expect = append([]byte{0x6}, []byte("barbar")...)
+	expect = append(expect, 5)
+	expect = append(expect, []byte("pinky")...)
+	if !bytes.Equal(r, expect) {
+		t.Errorf("expected %v, got %v", expect, r)
+	}
+	rb = append(rb, r...)
+
+	r = rt.Next()
+	expect = append([]byte{0x9}, []byte("bazbazbaz")...)
+	expect = append(expect, 6)
+	expect = append(expect, []byte("blinky")...)
+	if !bytes.Equal(r, expect) {
+		t.Errorf("expected %v, got %v", expect, r)
+	}
+	rb = append(rb, r...)
+}
+
+func TestSerialize(t *testing.T) {
+	rt := NewRouter()
+	err := rt.Add("foo", "inky")
+	if err != nil {
+		t.Error(err)
+	}
+	err = rt.Add("barbar", "pinky")
+	if err != nil {
+		t.Error(err)
+	}
+	err = rt.Add("bazbazbaz", "blinky")
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Serialize and deserialize.
+	ra := rt.ToBytes()
+	rt = FromBytes(ra)
+	rb := rt.ToBytes()
+	if !bytes.Equal(ra, rb) {
+		t.Errorf("expected %v, got %v", ra, rb)
+	}
+}
diff --git a/go/vm/vm.go b/go/vm/vm.go
index 1f1b2af..b1d955f 100644
--- a/go/vm/vm.go
+++ b/go/vm/vm.go
@@ -12,6 +12,15 @@ import (
 
 type Runner func(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error)
 
+func Apply(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
+	var err error
+	st, instruction, err = Run(instruction, st, rs, ctx)
+	if err != nil {
+		return st, instruction, err
+	}
+	return st, instruction, nil
+}
+
 func Run(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
 	var err error
 	for len(instruction) > 0 {