From 05013370fddf6d4aeedf840de5a462ffa19f0772 Mon Sep 17 00:00:00 2001
From: Marvin Blum <marvin@marvinblum.de>
Date: Tue, 3 May 2016 21:03:00 +0200
Subject: [PATCH] Basic system and window creation.

---
 README.md | 11 ++++++-
 actor.go  | 28 +++++++++++++++++
 game.go   | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 system.go | 68 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 195 insertions(+), 1 deletion(-)
 create mode 100644 actor.go
 create mode 100644 game.go
 create mode 100644 system.go

diff --git a/README.md b/README.md
index 4f6c351..82af253 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,11 @@
-# go-game
+# go-game (package "goga")
+
 Game engine written in Go using OpenGL and GLFW.
+**Under heavy development, do not use yet!**
+
+## Dependencies
+
+* https://github.com/go-gl/gl
+    - 4.5-core
+* https://github.com/go-gl/glfw
+    - 3.1
diff --git a/actor.go b/actor.go
new file mode 100644
index 0000000..fd73d14
--- /dev/null
+++ b/actor.go
@@ -0,0 +1,28 @@
+package goga
+
+import ()
+
+// An actor ID is a unique integer,
+// which can be used to reference an actor.
+type ActorId uint64
+
+// A basic actor, having a unique ID.
+// Use NewActor() to create new actors.
+type Actor struct {
+	id ActorId
+}
+
+var (
+	actorIdGen = ActorId(0)
+)
+
+// Creates a new basic actor with unique ID.
+func NewActor() *Actor {
+	actorIdGen++
+	return &Actor{actorIdGen}
+}
+
+// Returns the ID of actor.
+func (a *Actor) GetId() ActorId {
+	return a.id
+}
diff --git a/game.go b/game.go
new file mode 100644
index 0000000..ff87417
--- /dev/null
+++ b/game.go
@@ -0,0 +1,89 @@
+package goga
+
+import (
+	"github.com/go-gl/glfw/v3.1/glfw"
+	"math"
+	"time"
+)
+
+const (
+	default_width         = uint32(600)
+	default_height        = uint32(400)
+	default_title         = "Game"
+	default_exit_on_close = true
+)
+
+// Run options allow to set some parameters on startup.
+type RunOptions struct {
+	Title       string
+	Width       uint32
+	Height      uint32
+	ExitOnClose bool
+}
+
+// Main game object.
+type Game interface {
+}
+
+var (
+	running = true
+)
+
+// Creates a new window with given options and starts the game.
+// The game struct must implement the Game interface.
+// If options is nil, the default options will be used.
+// This function will panic on error.
+func Run(game Game, options *RunOptions) {
+	// init glfw
+	if err := glfw.Init(); err != nil {
+		panic("Error initializing GLFW: " + err.Error())
+	}
+
+	defer glfw.Terminate()
+
+	// create window
+	width := default_width
+	height := default_height
+	title := default_title
+	exitOnClose := default_exit_on_close
+
+	if options != nil {
+		width = options.Width
+		height = options.Height
+		title = options.Title
+		exitOnClose = options.ExitOnClose
+	}
+
+	wnd, err := glfw.CreateWindow(int(width), int(height), title, nil, nil)
+
+	if err != nil {
+		panic("Error creating GLFW window: " + err.Error())
+	}
+
+	// start and loop
+	wnd.MakeContextCurrent()
+	delta := time.Duration(0)
+	var deltaSec float64
+
+	for running {
+		if exitOnClose && wnd.ShouldClose() {
+			return
+		}
+
+		start := time.Now()
+
+		if !math.IsInf(deltaSec, 0) && !math.IsInf(deltaSec, -1) {
+			updateSystems(deltaSec)
+		}
+
+		delta = time.Since(start)
+		deltaSec = delta.Seconds()
+		wnd.SwapBuffers()
+		glfw.PollEvents()
+	}
+}
+
+// Stops the game and closes the window.
+func Stop() {
+	running = false
+}
diff --git a/system.go b/system.go
new file mode 100644
index 0000000..6bb8728
--- /dev/null
+++ b/system.go
@@ -0,0 +1,68 @@
+package goga
+
+import ()
+
+// A system provides logic for actors satisfying required components.
+// They are automatically updated on each frame.
+type System interface {
+	Update(float64)
+	Add(actor *Actor) bool
+	Remove(actor *Actor) bool
+	RemoveById(id ActorId) bool
+	RemoveAll()
+	Len() int
+	GetName() string
+}
+
+var (
+	systems []System
+)
+
+// Adds a system to the game.
+// Returns false if the system exists already.
+func AddSystem(system System) bool {
+	for _, sys := range systems {
+		if sys == system {
+			return false
+		}
+	}
+
+	systems = append(systems, system)
+
+	return true
+}
+
+// Removes the given system.
+// Returns false if it could not be found.
+func RemoveSystem(system System) bool {
+	for i, sys := range systems {
+		if sys == system {
+			systems = append(systems[:i], systems[i+1:]...)
+			return true
+		}
+	}
+
+	return false
+}
+
+// Removes all systems.
+func RemoveAllSystems() {
+	systems = make([]System, 0)
+}
+
+// Finds and returns a system by name, or nil if not found.
+func GetSystemByName(name string) System {
+	for _, system := range systems {
+		if system.GetName() == name {
+			return system
+		}
+	}
+
+	return nil
+}
+
+func updateSystems(delta float64) {
+	for _, system := range systems {
+		system.Update(delta)
+	}
+}