package world

// ClampCameraNoWrapViewport clamps camera center so that the VIEWPORT world-rect
// stays within the bounded world [0..worldW) x [0..worldH), when possible.
//
// This is the correct clamp for user panning when wrap is disabled.
// Margins (expanded canvas) are intentionally ignored here; they may extend outside the world.
func ClampCameraNoWrapViewport(
	cameraXWorldFp, cameraYWorldFp int,
	viewportW, viewportH int,
	zoomFp int,
	worldW, worldH int,
) (int, int) {
	if zoomFp <= 0 {
		panic("ClampCameraNoWrapViewport: invalid zoom")
	}
	if viewportW < 0 || viewportH < 0 {
		panic("ClampCameraNoWrapViewport: negative viewport")
	}
	if worldW <= 0 || worldH <= 0 {
		panic("ClampCameraNoWrapViewport: invalid world size")
	}

	spanW := PixelSpanToWorldFixed(viewportW, zoomFp)
	spanH := PixelSpanToWorldFixed(viewportH, zoomFp)

	halfW := spanW / 2
	halfH := spanH / 2

	cameraXWorldFp = clampCameraAxis(cameraXWorldFp, worldW, halfW)
	cameraYWorldFp = clampCameraAxis(cameraYWorldFp, worldH, halfH)

	return cameraXWorldFp, cameraYWorldFp
}

// ClampCameraNoWrapExpanded clamps camera center so that the EXPANDED CANVAS world-rect
// (viewport + margins) stays within the bounded world, when possible.
//
// This is stricter than viewport-based clamp and can prevent panning when margins are large.
func ClampCameraNoWrapExpanded(
	cameraXWorldFp, cameraYWorldFp int,
	viewportW, viewportH int,
	marginX, marginY int,
	zoomFp int,
	worldW, worldH int,
) (int, int) {
	if zoomFp <= 0 {
		panic("ClampCameraNoWrapExpanded: invalid zoom")
	}
	if viewportW < 0 || viewportH < 0 || marginX < 0 || marginY < 0 {
		panic("ClampCameraNoWrapExpanded: negative sizes")
	}
	if worldW <= 0 || worldH <= 0 {
		panic("ClampCameraNoWrapExpanded: invalid world size")
	}

	canvasW := viewportW + 2*marginX
	canvasH := viewportH + 2*marginY

	spanW := PixelSpanToWorldFixed(canvasW, zoomFp)
	spanH := PixelSpanToWorldFixed(canvasH, zoomFp)

	halfW := spanW / 2
	halfH := spanH / 2

	cameraXWorldFp = clampCameraAxis(cameraXWorldFp, worldW, halfW)
	cameraYWorldFp = clampCameraAxis(cameraYWorldFp, worldH, halfH)

	return cameraXWorldFp, cameraYWorldFp
}

func clampCameraAxis(cam, worldSize, halfSpan int) int {
	// If viewport/span does not fit: force center.
	if 2*halfSpan > worldSize {
		return worldSize / 2
	}

	minCam := halfSpan
	maxCam := worldSize - halfSpan

	if cam < minCam {
		return minCam
	}
	if cam > maxCam {
		return maxCam
	}
	return cam
}

// ClampRenderParamsNoWrap clamps camera center in-place when wrap is disabled.
// It uses viewport-based clamp (NOT expanded) so panning remains possible even with margins.
func (w *World) ClampRenderParamsNoWrap(p *RenderParams) {
	if p == nil {
		return
	}
	allowWrap := true
	if p.Options != nil && p.Options.DisableWrapScroll {
		allowWrap = false
	}
	if allowWrap {
		return
	}

	zoomFp, err := p.CameraZoomFp()
	if err != nil || zoomFp <= 0 {
		return
	}

	cx, cy := ClampCameraNoWrapViewport(
		p.CameraXWorldFp, p.CameraYWorldFp,
		p.ViewportWidthPx, p.ViewportHeightPx,
		zoomFp,
		w.W, w.H,
	)
	p.CameraXWorldFp = cx
	p.CameraYWorldFp = cy
}