package coffee.liz.abstractionengine.game

import androidx.compose.foundation.Canvas
import androidx.compose.runtime.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import coffee.liz.ecs.World
import kotlinx.coroutines.isActive

/**
 * Manages the game loop for an ECS world.
 * Syncs with Compose's frame rate (like requestAnimationFrame) and provides
 * the world to child content for custom rendering/UI.
 *
 * @param world The ECS world containing entities and systems
 * @param content Composable content that can use the world for rendering
 */
@Composable
fun Game(
    world: World,
    content: @Composable () -> Unit
) {
    // Trigger recomposition when we need to redraw
    var frameCount by remember { mutableStateOf(0) }

    // Game loop - syncs with Compose's frame rate like requestAnimationFrame
    LaunchedEffect(world) {
        var lastFrameTimeNanos = 0L

        while (isActive) {
            // Wait for next frame (like requestAnimationFrame)
            withFrameNanos { frameTimeNanos ->
                val deltaTime = if (lastFrameTimeNanos != 0L) {
                    (frameTimeNanos - lastFrameTimeNanos) / 1_000_000_000f
                } else {
                    0f
                }
                lastFrameTimeNanos = frameTimeNanos

                // Update ECS world (runs all systems)
                if (deltaTime > 0f) {
                    world.update(deltaTime)
                }

                // Trigger recomposition to redraw
                frameCount++
            }
        }
    }

    // Render content
    content()
}

/**
 * A Canvas that renders sprites from an ECS world using a RenderSystem.
 *
 * @param world The ECS world containing entities to render
 * @param renderSystem The system responsible for rendering sprites
 * @param backgroundColor Background color for the canvas
 * @param modifier Modifier for the Canvas
 */
@Composable
fun GameCanvas(
    world: World,
    renderSystem: RenderSystem,
    backgroundColor: Color = Color.Transparent,
    modifier: Modifier = Modifier
) {
    Canvas(modifier = modifier) {
        // Clear background
        drawRect(backgroundColor)

        // Render all sprites
        renderSystem.render(world, this)
    }
}