# coding: utf-8
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# Copyright (c) 2014-2018 European Synchrotron Radiation Facility
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"""
This module provides convenient classes and functions for OpenGL rendering.
"""

__authors__ = ["T. Vincent"]
__license__ = "MIT"
__date__ = "03/04/2017"


import numpy

from ...._glutils import gl


def buildFillMaskIndices(nIndices, dtype=None):
    """Returns triangle strip indices for rendering a filled polygon mask

    :param int nIndices: Number of points
    :param Union[numpy.dtype,None] dtype:
       If specified the dtype of the returned indices array
    :return: 1D array of indices constructing a triangle strip
    :rtype: numpy.ndarray
    """
    if dtype is None:
        if nIndices <= numpy.iinfo(numpy.uint16).max + 1:
            dtype = numpy.uint16
        else:
            dtype = numpy.uint32

    lastIndex = nIndices - 1
    splitIndex = lastIndex // 2 + 1
    indices = numpy.empty(nIndices, dtype=dtype)
    indices[::2] = numpy.arange(0, splitIndex, step=1, dtype=dtype)
    indices[1::2] = numpy.arange(lastIndex, splitIndex - 1, step=-1,
                                 dtype=dtype)
    return indices


class FilledShape2D(object):
    _NO_HATCH = 0
    _HATCH_STEP = 20

    def __init__(self, points, style='solid', color=(0., 0., 0., 1.)):
        self.vertices = numpy.array(points, dtype=numpy.float32, copy=False)
        self._indices = buildFillMaskIndices(len(self.vertices))

        tVertex = numpy.transpose(self.vertices)
        xMin, xMax = min(tVertex[0]), max(tVertex[0])
        yMin, yMax = min(tVertex[1]), max(tVertex[1])
        self.bboxVertices = numpy.array(((xMin, yMin), (xMin, yMax),
                                         (xMax, yMin), (xMax, yMax)),
                                        dtype=numpy.float32)
        self._xMin, self._xMax = xMin, xMax
        self._yMin, self._yMax = yMin, yMax

        self.style = style
        self.color = color

    def render(self, posAttrib, colorUnif, hatchStepUnif):
        assert self.style in ('hatch', 'solid')
        gl.glUniform4f(colorUnif, *self.color)
        step = self._HATCH_STEP if self.style == 'hatch' else self._NO_HATCH
        gl.glUniform1i(hatchStepUnif, step)

        # Prepare fill mask
        gl.glEnableVertexAttribArray(posAttrib)
        gl.glVertexAttribPointer(posAttrib,
                                 2,
                                 gl.GL_FLOAT,
                                 gl.GL_FALSE,
                                 0, self.vertices)

        gl.glEnable(gl.GL_STENCIL_TEST)
        gl.glStencilMask(1)
        gl.glStencilFunc(gl.GL_ALWAYS, 1, 1)
        gl.glStencilOp(gl.GL_INVERT, gl.GL_INVERT, gl.GL_INVERT)
        gl.glColorMask(gl.GL_FALSE, gl.GL_FALSE, gl.GL_FALSE, gl.GL_FALSE)
        gl.glDepthMask(gl.GL_FALSE)

        gl.glDrawElements(gl.GL_TRIANGLE_STRIP, len(self._indices),
                          gl.GL_UNSIGNED_SHORT, self._indices)

        gl.glStencilFunc(gl.GL_EQUAL, 1, 1)
        # Reset stencil while drawing
        gl.glStencilOp(gl.GL_ZERO, gl.GL_ZERO, gl.GL_ZERO)
        gl.glColorMask(gl.GL_TRUE, gl.GL_TRUE, gl.GL_TRUE, gl.GL_TRUE)
        gl.glDepthMask(gl.GL_TRUE)

        gl.glVertexAttribPointer(posAttrib,
                                 2,
                                 gl.GL_FLOAT,
                                 gl.GL_FALSE,
                                 0, self.bboxVertices)
        gl.glDrawArrays(gl.GL_TRIANGLE_STRIP, 0, len(self.bboxVertices))

        gl.glDisable(gl.GL_STENCIL_TEST)


# matrix ######################################################################

def mat4Ortho(left, right, bottom, top, near, far):
    """Orthographic projection matrix (row-major)"""
    return numpy.array((
        (2./(right - left), 0., 0., -(right+left)/float(right-left)),
        (0., 2./(top - bottom), 0., -(top+bottom)/float(top-bottom)),
        (0., 0., -2./(far-near),    -(far+near)/float(far-near)),
        (0., 0., 0., 1.)), dtype=numpy.float64)


def mat4Translate(x=0., y=0., z=0.):
    """Translation matrix (row-major)"""
    return numpy.array((
        (1., 0., 0., x),
        (0., 1., 0., y),
        (0., 0., 1., z),
        (0., 0., 0., 1.)), dtype=numpy.float64)


def mat4Scale(sx=1., sy=1., sz=1.):
    """Scale matrix (row-major)"""
    return numpy.array((
        (sx, 0., 0., 0.),
        (0., sy, 0., 0.),
        (0., 0., sz, 0.),
        (0., 0., 0., 1.)), dtype=numpy.float64)


def mat4Identity():
    """Identity matrix"""
    return numpy.array((
        (1., 0., 0., 0.),
        (0., 1., 0., 0.),
        (0., 0., 1., 0.),
        (0., 0., 0., 1.)), dtype=numpy.float64)