From e3bc1251e8cb20b30d0c5a27cd1da8f147a82de7 Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Thu, 23 Sep 2021 00:24:53 +0200
Subject: Began coding the interpreter (only manages the minimal example for
 now!)

---
 cmd/headless_interpreter/main.go | 42 ++++++++++++++++++++++++++++++++++++++++
 pkg/interpreter/interpreter.go   | 40 ++++++++++++++++++++++++++++++++++++++
 pkg/pointer/pointer.go           |  6 ++++++
 pkg/pointer/pointer_test.go      | 11 +++++++++++
 4 files changed, 99 insertions(+)
 create mode 100644 cmd/headless_interpreter/main.go
 create mode 100644 pkg/interpreter/interpreter.go

diff --git a/cmd/headless_interpreter/main.go b/cmd/headless_interpreter/main.go
new file mode 100644
index 0000000..73b71dc
--- /dev/null
+++ b/cmd/headless_interpreter/main.go
@@ -0,0 +1,42 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+
+	"git.adyxax.org/adyxax/gofunge/pkg/field"
+	"git.adyxax.org/adyxax/gofunge/pkg/interpreter"
+	"git.adyxax.org/adyxax/gofunge/pkg/pointer"
+)
+
+func main() {
+	filename := flag.String("f", "", "b98 file to interpret")
+	help := flag.Bool("h", false, "display this help message")
+	flag.Parse()
+
+	if *help {
+		flag.Usage()
+		os.Exit(0)
+	}
+
+	if *filename == "" {
+		fmt.Println("Error : no b98 file to interpret")
+		flag.Usage()
+		os.Exit(1)
+	}
+	file, err := os.Open(*filename)
+	if err != nil {
+		fmt.Printf("Failed to open file %s : %+v", *filename, err)
+		os.Exit(2)
+	}
+	defer file.Close()
+
+	f, err := field.Load(file)
+	if err != nil {
+		fmt.Printf("Failed to load file %s : %+v", *filename, err)
+		os.Exit(3)
+	}
+
+	interpreter.NewInterpreter(f, pointer.NewPointer()).Run()
+}
diff --git a/pkg/interpreter/interpreter.go b/pkg/interpreter/interpreter.go
new file mode 100644
index 0000000..ce2499d
--- /dev/null
+++ b/pkg/interpreter/interpreter.go
@@ -0,0 +1,40 @@
+package interpreter
+
+import (
+	"log"
+
+	"git.adyxax.org/adyxax/gofunge/pkg/field"
+	"git.adyxax.org/adyxax/gofunge/pkg/pointer"
+)
+
+type Interpreter struct {
+	f *field.Field
+	p *pointer.Pointer
+}
+
+func NewInterpreter(f *field.Field, p *pointer.Pointer) *Interpreter {
+	return &Interpreter{f: f, p: p}
+}
+
+func (i *Interpreter) Run() {
+	for i.p != nil {
+		i.Step()
+	}
+}
+
+func (i *Interpreter) Step() {
+	var prev *pointer.Pointer = nil
+	for p := i.p; p != nil; p = p.Next {
+		switch p.Get(*i.f) {
+		case '@':
+			if prev == nil {
+				i.p = p.Next
+			} else {
+				prev.Next = p.Next
+			}
+			break
+		default:
+			log.Fatalf("Non implemented instruction code %d : %c", p.Get(*i.f), p.Get(*i.f))
+		}
+	}
+}
diff --git a/pkg/pointer/pointer.go b/pkg/pointer/pointer.go
index 5847e70..a833f5b 100644
--- a/pkg/pointer/pointer.go
+++ b/pkg/pointer/pointer.go
@@ -12,6 +12,8 @@ type Pointer struct {
 	// The Storage offset
 	sox int
 	soy int
+	// The next element for the multi-"threaded" b98 interpreter
+	Next *Pointer
 }
 
 func NewPointer() *Pointer {
@@ -25,3 +27,7 @@ func (p Pointer) Split() *Pointer {
 func (p *Pointer) Step(f field.Field) {
 	p.x, p.y = f.Step(p.x, p.y, p.dx, p.dy)
 }
+
+func (p Pointer) Get(f field.Field) int {
+	return f.Get(p.x, p.y)
+}
diff --git a/pkg/pointer/pointer_test.go b/pkg/pointer/pointer_test.go
index 658528d..ccbf486 100644
--- a/pkg/pointer/pointer_test.go
+++ b/pkg/pointer/pointer_test.go
@@ -39,3 +39,14 @@ func TestStep(t *testing.T) { // Step is thoroughly tested in the field package
 	p.Step(*f)
 	require.Equal(t, defaultPointer, p)
 }
+
+func TestGet(t *testing.T) {
+	// File of one char
+	file, err := os.Open("../field/test_data/minimal.b98")
+	require.NoError(t, err, "Failed to open file")
+	defer file.Close()
+	f, err := field.Load(file)
+	p := NewPointer()
+	v := p.Get(*f)
+	require.Equal(t, int('@'), v)
+}
-- 
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