130 lines
3.0 KiB
Go
130 lines
3.0 KiB
Go
package gohan
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import (
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"fmt"
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"log"
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"os"
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"strings"
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"time"
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"github.com/hajimehoshi/ebiten/v2"
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)
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var (
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gameComponents = make(map[EntityID]map[ComponentID]interface{})
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gameSystems []System
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gameSystemEntities [][]EntityID // Slice of entities matching each system.
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gameSystemReceivesUpdate []bool
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gameSystemReceivesDraw []bool
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debug bool
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)
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func init() {
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debugEnv := os.Getenv("GOHAN_DEBUG")
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debugEnv = strings.TrimSpace(debugEnv)
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debugEnv = strings.ToLower(debugEnv)
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debug = debugEnv == "1" || debugEnv == "t" || debugEnv == "y" || debugEnv == "on" || debugEnv == "yes" || debugEnv == "true"
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}
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// print prints debug information (when enabled).
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func print(s string) {
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if !debug {
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return
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}
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log.Println(s)
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}
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func attachEntitiesToSystem(system System) {
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// This function is always called on a newly added system.
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systemID := len(gameSystemEntities) - 1
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for entity := EntityID(0); entity < nextEntityID; entity++ {
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if system.Matches(entity) {
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gameSystemEntities[systemID] = append(gameSystemEntities[systemID], entity)
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print(fmt.Sprintf("Attached entity %d to system %d.", entity, systemID))
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}
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}
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}
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// RegisterSystem registers a system to start receiving Update and Draw calls.
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func RegisterSystem(system System) {
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gameSystems = append(gameSystems, system)
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gameSystemReceivesUpdate = append(gameSystemReceivesUpdate, true)
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gameSystemReceivesDraw = append(gameSystemReceivesDraw, true)
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gameSystemEntities = append(gameSystemEntities, nil)
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attachEntitiesToSystem(system)
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}
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func updateSystem(i int) (int, error) {
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updated := 0
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for _, entity := range gameSystemEntities[i] {
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err := gameSystems[i].Update(entity)
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if err != nil {
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if err == ErrSystemWithoutUpdate {
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// Unregister system from Update events.
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gameSystemReceivesUpdate[i] = false
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return 0, nil
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}
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return 0, fmt.Errorf("failed to update system %d for entity %d: %s", i, entity, err)
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}
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updated++
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}
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return updated, nil
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}
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// Update updates the game state.
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func Update() error {
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var t time.Time
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if debug {
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t = time.Now()
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}
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var systems int
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for i, registered := range gameSystemReceivesUpdate {
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if !registered {
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continue
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}
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updated, err := updateSystem(i)
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if err != nil {
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return err
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}
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print(fmt.Sprintf("System %d: updated %d entities.", i, updated))
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systems++
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}
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if debug {
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print(fmt.Sprintf("Finished updating %d systems in %.2fms.", systems, float64(time.Since(t).Microseconds())/1000))
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}
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return nil
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}
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// Draw draws the game on to the screen.
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func Draw(screen *ebiten.Image) error {
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DRAWSYSTEMS:
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for i, registered := range gameSystemReceivesDraw {
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if !registered {
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continue
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}
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for _, entity := range gameSystemEntities[i] {
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err := gameSystems[i].Draw(entity, screen)
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if err != nil {
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if err == ErrSystemWithoutDraw {
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// Unregister system from Draw events.
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gameSystemReceivesDraw[i] = false
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continue DRAWSYSTEMS
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}
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return fmt.Errorf("failed to draw system %d for entity %d: %s", i, entity, err)
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}
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}
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}
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return nil
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}
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