// Rendering constants
const RENDER_CONSTANTS = {
    VIEWPORT_BUFFER: 100,
    SKY_COLORS: {
        TOP: '#1a1a2e',
        UPPER_MID: '#2d1b3d',
        LOWER_MID: '#462639',
        BOTTOM: '#1f1f2f'
    },
    GROUND_COLOR: '#4a4',
    DEBUG_FONT: '14px monospace',
    DEBUG_COLOR: '#ffffff'
};

// Helper functions for rendering
const createSkyGradient = (ctx, groundY) => {
    const gradient = ctx.createLinearGradient(0, 0, 0, groundY);
    gradient.addColorStop(0, RENDER_CONSTANTS.SKY_COLORS.TOP);
    gradient.addColorStop(0.4, RENDER_CONSTANTS.SKY_COLORS.UPPER_MID);
    gradient.addColorStop(0.7, RENDER_CONSTANTS.SKY_COLORS.LOWER_MID);
    gradient.addColorStop(1, RENDER_CONSTANTS.SKY_COLORS.BOTTOM);
    return gradient;
};

const getViewBounds = (camera) => ({
    left: camera.x - RENDER_CONSTANTS.VIEWPORT_BUFFER,
    right: camera.x + camera.width + RENDER_CONSTANTS.VIEWPORT_BUFFER,
    top: camera.y - RENDER_CONSTANTS.VIEWPORT_BUFFER,
    bottom: camera.y + camera.height + RENDER_CONSTANTS.VIEWPORT_BUFFER
});

const isInView = (x, viewBounds) => 
    x > viewBounds.left && x < viewBounds.right;

// Layer rendering functions
const renderBackground = (ctx, state, groundY, viewBounds) => {
    // Save the current transform
    ctx.save();
    
    // Reset transform for viewport-fixed sky and initial black fill
    ctx.setTransform(1, 0, 0, 1, 0, 0);
    
    // Sky (fixed to viewport)
    ctx.fillStyle = state.cachedGradient;
    ctx.fillRect(0, 0, ctx.canvas.width, groundY);

    // Initial black fill for the bottom of the viewport
    ctx.fillStyle = '#000000';
    ctx.fillRect(0, groundY, ctx.canvas.width, ctx.canvas.height - groundY + 1);

    // Restore transform for world-space rendering
    ctx.restore();
    
    // Additional black fill that follows the camera (extends far to left and right)
    ctx.fillStyle = '#000000';
    ctx.fillRect(
        viewBounds.left - 2000,
        groundY,
        viewBounds.right - viewBounds.left + 4000,
        ctx.canvas.height
    );
};

const renderBackgroundObjects = (ctx, state, groundY, viewBounds) => {
    state.world.backgroundTrees
        .filter(tree => isInView(tree.x, viewBounds))
        .forEach(tree => renderTree(ctx, tree, groundY));
    
    state.world.backgroundRocks
        .filter(rock => isInView(rock.x, viewBounds))
        .forEach(rock => renderRock(ctx, rock, groundY));
    
    state.world.backgroundGrass
        .filter(grass => isInView(grass.x, viewBounds))
        .forEach(grass => renderGrass(ctx, grass, groundY, state.time));
};

const renderForegroundObjects = (ctx, state, groundY, viewBounds) => {
    state.world.foregroundTrees
        .filter(tree => isInView(tree.x, viewBounds))
        .forEach(tree => renderTree(ctx, tree, groundY));
    
    state.world.foregroundRocks
        .filter(rock => isInView(rock.x, viewBounds))
        .forEach(rock => renderRock(ctx, rock, groundY));
    
    state.world.foregroundGrass
        .filter(grass => isInView(grass.x, viewBounds))
        .forEach(grass => renderGrass(ctx, grass, groundY, state.time));
};

const renderDebugInfo = (ctx, state) => {
    ctx.fillStyle = RENDER_CONSTANTS.DEBUG_COLOR;
    ctx.font = RENDER_CONSTANTS.DEBUG_FONT;
    const text = `x: ${Math.round(state.debug.mouseX)}, y: ${Math.round(state.debug.mouseY)}`;
    ctx.fillText(text, 10, ctx.canvas.height - 20);
};