From 46170dd5b70588c9b1c6f4aa5aaea2649d8c74f0 Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Mon, 20 Sep 2021 01:23:39 +0200
Subject: Began implementing the Instruction Pointer

---
 pkg/pointer/delta.go        | 10 ++++++++++
 pkg/pointer/pointer.go      | 21 +++++++++++++++++++++
 pkg/pointer/pointer_test.go | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 72 insertions(+)
 create mode 100644 pkg/pointer/delta.go
 create mode 100644 pkg/pointer/pointer.go
 create mode 100644 pkg/pointer/pointer_test.go

diff --git a/pkg/pointer/delta.go b/pkg/pointer/delta.go
new file mode 100644
index 0000000..0c3e074
--- /dev/null
+++ b/pkg/pointer/delta.go
@@ -0,0 +1,10 @@
+package pointer
+
+type Delta struct {
+	x int
+	y int
+}
+
+func NewDelta(x, y int) *Delta {
+	return &Delta{x: x, y: y}
+}
diff --git a/pkg/pointer/pointer.go b/pkg/pointer/pointer.go
new file mode 100644
index 0000000..5b4b860
--- /dev/null
+++ b/pkg/pointer/pointer.go
@@ -0,0 +1,21 @@
+package pointer
+
+import "git.adyxax.org/adyxax/gofunge/pkg/field"
+
+type Pointer struct {
+	x     int
+	y     int
+	delta *Delta
+}
+
+func NewPointer() *Pointer {
+	return &Pointer{delta: NewDelta(1, 0)}
+}
+
+func (p Pointer) ForkPointer() *Pointer {
+	return &p // p is already a copy
+}
+
+func (p *Pointer) Step(f field.Field) {
+	p.x, p.y = f.Step(p.x, p.y, p.delta.x, p.delta.y)
+}
diff --git a/pkg/pointer/pointer_test.go b/pkg/pointer/pointer_test.go
new file mode 100644
index 0000000..3a77507
--- /dev/null
+++ b/pkg/pointer/pointer_test.go
@@ -0,0 +1,41 @@
+package pointer
+
+import (
+	"os"
+	"testing"
+
+	"git.adyxax.org/adyxax/gofunge/pkg/field"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewPointer(t *testing.T) {
+	require.Equal(t, NewPointer(), &Pointer{delta: &Delta{1, 0}})
+}
+
+func TestForkPointer(t *testing.T) {
+	file, err := os.Open("../field/test_data/hello.b98")
+	require.NoError(t, err, "Failed to open file")
+	defer file.Close()
+	f, err := field.Load(file)
+	require.NoError(t, err)
+	p := NewPointer()
+	p2 := p.ForkPointer()
+	// We check that p2 is a real copy
+	p.Step(*f)
+	p2.Step(*f)
+	require.Equal(t, p, &Pointer{x: 1, y: 0, delta: &Delta{1, 0}})
+	require.Equal(t, p2, &Pointer{x: 1, y: 0, delta: &Delta{1, 0}})
+}
+
+func TestStep(t *testing.T) { // Step is thoroughly tested in the field package
+	defaultPointer := NewPointer()
+	// 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)
+	require.NoError(t, err)
+	p := NewPointer()
+	p.Step(*f)
+	require.Equal(t, defaultPointer, p)
+}
-- 
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