pms-iot-vue/src/components/mt-edit/utils/canvas-scale.ts

export const MIN_CANVAS_SCALE = 0.1
export const MAX_CANVAS_SCALE = 4
export const CANVAS_SCALE_STEP = 0.1

export type CanvasScaleDirection = 'in' | 'out'

export interface FitCanvasOptions {
  viewportWidth: number
  viewportHeight: number
  canvasWidth: number
  canvasHeight: number
  padding?: Partial<{
    top: number
    right: number
    bottom: number
    left: number
  }>
}

export const normalizeCanvasScale = (scale: number) => {
  const safeScale = Number.isFinite(scale) ? scale : 1
  const clampedScale = Math.min(MAX_CANVAS_SCALE, Math.max(MIN_CANVAS_SCALE, safeScale))
  return Math.round(clampedScale * 100) / 100
}

export const stepCanvasScale = (scale: number, direction: CanvasScaleDirection) =>
  normalizeCanvasScale(scale + (direction === 'in' ? CANVAS_SCALE_STEP : -CANVAS_SCALE_STEP))

export const calculateFitCanvas = ({
  viewportWidth,
  viewportHeight,
  canvasWidth,
  canvasHeight,
  padding
}: FitCanvasOptions) => {
  const safePadding = {
    top: Math.max(0, padding?.top ?? 24),
    right: Math.max(0, padding?.right ?? 24),
    bottom: Math.max(0, padding?.bottom ?? 72),
    left: Math.max(0, padding?.left ?? 24)
  }
  const availableWidth = Math.max(1, viewportWidth - safePadding.left - safePadding.right)
  const availableHeight = Math.max(1, viewportHeight - safePadding.top - safePadding.bottom)
  const safeCanvasWidth = Math.max(1, canvasWidth)
  const safeCanvasHeight = Math.max(1, canvasHeight)
  const scale = normalizeCanvasScale(
    Math.min(availableWidth / safeCanvasWidth, availableHeight / safeCanvasHeight)
  )

  return {
    scale,
    transformOrigin: { x: 0, y: 0 },
    dragOffset: {
      x: Math.round(safePadding.left + (availableWidth - safeCanvasWidth * scale) / 2),
      y: Math.round(safePadding.top + (availableHeight - safeCanvasHeight * scale) / 2)
    }
  }
}