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  {
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   "source": [
    "# Polygon validation\n",
    "\n",
    "Making the polygons be non-self-intersecting is critical. There are routines in GEOS (and exposed in teqpflsh) to break up self-intersecting polygons into non-self-intersecting polygons"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "6b45a70c",
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    "editable": true,
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     "slide_type": ""
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   "source": [
    "import numpy as np\n",
    "import teqpflsh\n",
    "import matplotlib.pyplot as plt\n",
    "teqpflsh.__version__"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "b6182393",
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    "editable": true,
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   "source": [
    "ptr = teqpflsh.GeometryFactoryHolder()\n",
    "\n",
    "# A bowtie curve that is periodic and self-intersecting\n",
    "t = np.linspace(0+0.1, 2*np.pi+0.1, 10000)\n",
    "X,Y = np.cos(t), np.cos(t)*np.sin(t)\n",
    "poly1 = ptr.makeclosedpolygon(X, Y)\n",
    "plt.plot(X, Y)\n",
    "plt.plot(X[0], Y[0], 'o')\n",
    "poly1.isValid # False since self-intersecting"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ca4134dc-7c34-4894-a289-f51717086c14",
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   "source": [
    "The reason this matters in this context is that we need to be able to sample the domain randomly to generate guess values."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "82c3f307-8322-4fa8-be80-f245ae866360",
   "metadata": {
    "editable": true,
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     "slide_type": ""
    },
    "tags": [
     "raises-exception"
    ]
   },
   "outputs": [],
   "source": [
    "# This doesn't work because the triangulation fails because the geometry is not valid\n",
    "N = 10000\n",
    "x = np.zeros((N, ))\n",
    "y = np.zeros((N, ))\n",
    "teqpflsh.sample_random(poly1, 10000, x, y)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "a8e9c1d5-3aa6-44b3-a766-9c413395e1c5",
   "metadata": {
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   "source": [
    "Now we need to break up the polygon into portions that are simple (non self-intersecting) with the MakeValid class of geos : https://libgeos.org/doxygen/classgeos_1_1operation_1_1valid_1_1MakeValid.html"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "038ff472-6551-47c6-bb33-151f1ff4e483",
   "metadata": {
    "editable": true,
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     "slide_type": ""
    },
    "tags": []
   },
   "outputs": [],
   "source": [
    "simpl = poly1.make_valid()\n",
    "print(f'N: {simpl.getNumGeometries()}')\n",
    "print(f'simple: {simpl.isSimple}')\n",
    "print(f'valid: {simpl.isValid}')\n",
    "for i in range(simpl.getNumGeometries()):\n",
    "    pI = simpl.getGeometryN(i)\n",
    "    plt.plot(*pI.getXY())\n",
    "    print(f'N: {pI.getNumGeometries()}')\n",
    "    print(f'simple: {pI.isSimple}')\n",
    "    print(f'valid: {pI.isValid}')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "30b47157-b3c5-4090-a4f4-10a642661cbb",
   "metadata": {
    "editable": true,
    "slideshow": {
     "slide_type": ""
    },
    "tags": []
   },
   "outputs": [],
   "source": [
    "# And now sampling works after forcing validity\n",
    "N = 10000\n",
    "x = np.zeros((N, ))\n",
    "y = np.zeros((N, ))\n",
    "teqpflsh.sample_random(simpl, 10000, x, y)\n",
    "plt.plot(x, y, '.', ms=1);"
   ]
  }
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