From 5c4ee2bc2ec7f584487910ef99b0b7b0bf818759 Mon Sep 17 00:00:00 2001
From: Nicholas Novak <34256932+NickyBoy89@users.noreply.github.com>
Date: Mon, 11 Dec 2023 01:33:39 -0800
Subject: [PATCH] feat: In-progress work on unity files

---
 storage/unity_file.go      | 93 ++++++++++++++++++++++++++++++++++++++
 storage/unity_file_test.go | 30 ++++++++++++
 2 files changed, 123 insertions(+)
 create mode 100644 storage/unity_file.go
 create mode 100644 storage/unity_file_test.go

diff --git a/storage/unity_file.go b/storage/unity_file.go
new file mode 100644
index 0000000..83a898a
--- /dev/null
+++ b/storage/unity_file.go
@@ -0,0 +1,93 @@
+package storage
+
+import (
+	"bytes"
+	"encoding/json"
+	"os"
+
+	"git.nicholasnovak.io/nnovak/spatial-db/world"
+)
+
+// A `UnityFile` is a collection of chunks, stored as a single file on disk
+//
+// This is done because with worlds that span millions of chunks, the speed to
+// access individual files slows down
+type UnityFile struct {
+	fd       *os.File
+	fileSize int
+	// metadata maps the position of a chunk to its start index within the file
+	metadata map[world.ChunkPos]int
+}
+
+func CreateUnityFile(fileName string) (UnityFile, error) {
+	var u UnityFile
+
+	f, err := os.Create(fileName)
+	if err != nil {
+		return u, err
+	}
+
+	u.fd = f
+	u.metadata = make(map[world.ChunkPos]int)
+
+	return u, nil
+}
+
+func (u UnityFile) Size() int {
+	return u.fileSize
+}
+
+func (u *UnityFile) WriteChunk(data world.ChunkData) error {
+	var encoded bytes.Buffer
+
+	// Encode the chunk first
+	if err := json.NewEncoder(&encoded).Encode(data); err != nil {
+		return err
+	}
+
+	encodedSize := encoded.Len()
+
+	// Go to the end of the file
+	u.fd.Seek(0, u.fileSize)
+	// Write the encoded contents to the file
+	if _, err := u.fd.Write(encoded.Bytes()); err != nil {
+		return err
+	}
+
+	// Update the metadata with the new file
+	u.metadata[data.Pos] = u.fileSize
+	u.fileSize += encodedSize
+
+	return nil
+}
+
+func (u UnityFile) WriteMetadataFile(fileName string) error {
+	fd, err := os.OpenFile(fileName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
+	if err != nil {
+		return err
+	}
+	defer fd.Close()
+
+	if err := json.NewEncoder(fd).Encode(&u.metadata); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (u *UnityFile) ReadMetadataFile(fileName string) error {
+	fd, err := os.Open(fileName)
+	if err != nil {
+		return err
+	}
+
+	if err := json.NewDecoder(fd).Decode(&u.metadata); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (u UnityFile) ReadChunk() world.ChunkData {
+	return world.ChunkData{}
+}
diff --git a/storage/unity_file_test.go b/storage/unity_file_test.go
new file mode 100644
index 0000000..00bac95
--- /dev/null
+++ b/storage/unity_file_test.go
@@ -0,0 +1,30 @@
+package storage
+
+import (
+	"os"
+	"path"
+	"testing"
+)
+
+func TestCreateUnityFile(t *testing.T) {
+	tempDir, err := os.MkdirTemp("", "unity")
+	if err != nil {
+		t.Fatalf("Error creating temporary directory: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Create an empty file
+	u, err := CreateUnityFile(path.Join(tempDir, "test-unity"))
+	if err != nil {
+		t.Fatalf("Error creating unity file: %v", err)
+	}
+
+	if u.Size() != 0 {
+		t.Fatalf("Expected size of file to be %v, got %v", 0, u.Size())
+	}
+
+	// Save the metadata
+	if err := u.WriteMetadataFile(path.Join(tempDir, "test-unity.metadata")); err != nil {
+		t.Fatalf("Got an error saving the empty metadata: %v", err)
+	}
+}