export const BRUSH_MODE_NORMAL = "normal";
export const BRUSH_MODE_PIXEL = "pixel";
export const CANVAS_VIEW_MIN_SCALE = 1;
export const CANVAS_VIEW_MAX_SCALE = 8;
export const CANVAS_UNDO_LIMIT = 50;

const MODE_SPECS = Object.freeze({
  [BRUSH_MODE_NORMAL]: Object.freeze({ min: 1, max: 16, presets: Object.freeze([1, 2, 4, 8]) }),
  [BRUSH_MODE_PIXEL]: Object.freeze({ min: 1, max: 4, presets: Object.freeze([1, 2, 3, 4]) }),
});

function record(value) {
  return value && typeof value === "object" && !Array.isArray(value) ? value : null;
}

export function brushModeSpec(mode) {
  return MODE_SPECS[mode === BRUSH_MODE_PIXEL ? BRUSH_MODE_PIXEL : BRUSH_MODE_NORMAL];
}

export function normalizeBrushSize(value, mode) {
  const spec = brushModeSpec(mode);
  const parsed = Number.parseInt(value, 10);
  return Math.max(spec.min, Math.min(spec.max, Number.isFinite(parsed) ? parsed : spec.min));
}

export function restoreCanvasToolState(savedV2, savedV1 = null) {
  const current = record(savedV2);
  const legacy = record(savedV1);
  const source = current || legacy || {};
  return {
    paintColor: typeof source.paintColor === "string" ? source.paintColor : null,
    backgroundColor: typeof source.backgroundColor === "string" ? source.backgroundColor : null,
    tool: source.tool === "eraser" ? "eraser" : "brush",
    pixelEditEnabled: Boolean(current?.pixelEditEnabled),
    normalBrushSize: normalizeBrushSize(
      current?.normalBrushSize ?? source.brushSize,
      BRUSH_MODE_NORMAL,
    ),
    pixelBrushSize: normalizeBrushSize(current?.pixelBrushSize, BRUSH_MODE_PIXEL),
  };
}

export function linePoints(from, to) {
  const points = [];
  let x = from.x;
  let y = from.y;
  const dx = Math.abs(to.x - from.x);
  const sx = from.x < to.x ? 1 : -1;
  const dy = -Math.abs(to.y - from.y);
  const sy = from.y < to.y ? 1 : -1;
  let error = dx + dy;
  while (true) {
    points.push({ x, y });
    if (x === to.x && y === to.y) break;
    const doubled = 2 * error;
    if (doubled >= dy) {
      error += dy;
      x += sx;
    }
    if (doubled <= dx) {
      error += dx;
      y += sy;
    }
  }
  return points;
}

export function brushStampPoints(centerX, centerY, size, mode, width = 64, height = 64) {
  const normalizedMode = mode === BRUSH_MODE_PIXEL ? BRUSH_MODE_PIXEL : BRUSH_MODE_NORMAL;
  const diameter = normalizeBrushSize(size, normalizedMode);
  const start = -Math.floor((diameter - 1) / 2);
  const radius = Math.max(0.25, (diameter - 0.5) / 2);
  const shapeCenter = (diameter - 1) / 2;
  const points = [];
  for (let localY = 0; localY < diameter; localY += 1) {
    for (let localX = 0; localX < diameter; localX += 1) {
      if (normalizedMode === BRUSH_MODE_NORMAL) {
        const normalizedX = (localX - shapeCenter) / radius;
        const normalizedY = (localY - shapeCenter) / radius;
        if ((normalizedX * normalizedX) + (normalizedY * normalizedY) > 1) continue;
      }
      const x = centerX + start + localX;
      const y = centerY + start + localY;
      if (x >= 0 && x < width && y >= 0 && y < height) points.push({ x, y });
    }
  }
  return points;
}

export function pixelBuffersEqual(left, right) {
  if (!left || !right || left.length !== right.length) return false;
  for (let index = 0; index < left.length; index += 1) {
    if (left[index] !== right[index]) return false;
  }
  return true;
}

export class PixelUndoHistory {
  constructor(limit = CANVAS_UNDO_LIMIT) {
    this.limit = Math.max(1, Number.isInteger(limit) ? limit : CANVAS_UNDO_LIMIT);
    this.entries = [];
  }

  get size() {
    return this.entries.length;
  }

  record(before, after) {
    if (pixelBuffersEqual(before, after)) return false;
    this.entries.push(Uint8Array.from(before));
    if (this.entries.length > this.limit) this.entries.splice(0, this.entries.length - this.limit);
    return true;
  }

  undo() {
    return this.entries.pop() || null;
  }

  clear() {
    this.entries.length = 0;
  }
}

export function normalizeCanvasScale(value) {
  const scale = Number(value);
  if (!Number.isFinite(scale)) return CANVAS_VIEW_MIN_SCALE;
  return Math.max(CANVAS_VIEW_MIN_SCALE, Math.min(CANVAS_VIEW_MAX_SCALE, scale));
}

export function clampCanvasView(
  view,
  { viewportWidth, viewportHeight, baseSize, minVisible = 48 },
) {
  const scale = normalizeCanvasScale(view?.scale);
  const width = Math.max(1, Number(baseSize) || 1) * scale;
  const height = width;
  const visibleX = Math.min(Math.max(1, Number(minVisible) || 1), width, viewportWidth);
  const visibleY = Math.min(Math.max(1, Number(minVisible) || 1), height, viewportHeight);
  const limitX = Math.max(0, (viewportWidth + width) / 2 - visibleX);
  const limitY = Math.max(0, (viewportHeight + height) / 2 - visibleY);
  return {
    scale,
    x: Math.max(-limitX, Math.min(limitX, Number(view?.x) || 0)),
    y: Math.max(-limitY, Math.min(limitY, Number(view?.y) || 0)),
  };
}

export function zoomCanvasView(view, nextScale, anchor, bounds) {
  const scale = normalizeCanvasScale(nextScale);
  const previousScale = normalizeCanvasScale(view?.scale);
  const centerX = bounds.viewportWidth / 2;
  const centerY = bounds.viewportHeight / 2;
  const ratio = scale / previousScale;
  const x = (anchor.x - centerX) - ratio * (anchor.x - centerX - (Number(view?.x) || 0));
  const y = (anchor.y - centerY) - ratio * (anchor.y - centerY - (Number(view?.y) || 0));
  return clampCanvasView({ scale, x, y }, bounds);
}

export function clampFloatingButton(position, {
  viewportWidth,
  viewportHeight,
  size = 56,
  inset = 8,
}) {
  const half = size / 2;
  const minX = inset + half;
  const maxX = Math.max(minX, viewportWidth - inset - half);
  const minY = inset + half;
  const maxY = Math.max(minY, viewportHeight - inset - half);
  return {
    x: Math.max(minX, Math.min(maxX, Number(position?.x) || minX)),
    y: Math.max(minY, Math.min(maxY, Number(position?.y) || minY)),
  };
}