import copy
import StringIO
import numpy

import theano
from theano import tensor, gof, Op
from theano.tensor.subtensor import IncSubtensor, Subtensor, get_idx_list
import theano.tensor.inplace

try:
    import pygpu
    from pygpu import gpuarray
except ImportError:
    pass

from .type import GpuArrayType
from .basic_ops import as_gpuarray_variable, HideC
from .elemwise import GpuElemwise
from .comp import NVCC_compiler


class GpuSubtensor(HideC, Subtensor):
    def make_node(self, x, *inputs):
        rval = tensor.Subtensor.make_node(self, x, *inputs)
        otype = GpuArrayType(dtype=rval.outputs[0].type.dtype,
                             broadcastable=rval.outputs[0].type.broadcastable)
        x = as_gpuarray_variable(x)
        return gof.Apply(self, [x] + rval.inputs[1:], [otype()])

    def perform(self, node, inputs, out_):
        out, = out_
        x = inputs[0]

        cdata = get_idx_list(inputs, self.idx_list)
        if len(cdata) == 1:
            cdata = cdata[0]

        out[0] = x.__getitem__(cdata)

    def c_support_code(self):
        return """
        static int fix_indices(ssize_t *start, ssize_t *stop, ssize_t *step,
                               int start_n, int stop_n, int step_n,
                               size_t len) {
            if (step_n) *step = 1;
            if (*step == 0) {
                PyErr_SetString(PyExc_ValueError, "slice step cannot be zero");
                return -1;
            }
            if (start_n) *start = (*step < 0) ? len-1 : 0;
            else {
                if (*start < 0) *start += len;
                if (*start < 0) *start = (*step < 0) ? -1 : 0;
                if (*start > -1 && *start >= len) {
                    *start = (*step < 0) ? len-1 : len;
                }
            }

            if (stop_n) *stop = (*step < 0) ? -1 : len;
            else {
                if (*stop < 0) *stop += len;
                if (*stop < 0) *stop = (*step < 0) ? -1 : 0;
                if (*stop > -1 && *stop >= len) {
                    *stop = (*step < 0) ? len-1 : len;
                }
            }
            if (*stop < *start && *step > 0)
                *stop = *start;
            return 0;
        }
        """

    def c_code(self, node, name, inputs, outputs, sub):
        inp_ndim = node.inputs[0].ndim
        inp = inputs[0]
        indices = inputs[1:]

        # pad out the index list to the same dimension as the input
        idx_list = self.idx_list + \
            ((slice(None),) * (inp_ndim - len(self.idx_list)))

        # This case fails when we use pygpu_index(), so here is some
        # special code
        if len(idx_list) == 0:
            return """
        Py_XDECREF(%(out)s);
        %(out)s = pygpu_copy(%(inp)s, GA_ANY_ORDER);
        if (!%(out)s) { %(fail)s }
""" % dict(out=outputs[0], inp=inp, fail=sub['fail'])

        sio = StringIO.StringIO()
        print >> sio, """
        ssize_t starts[%(sz)s];
        ssize_t stops[%(sz)s];
        ssize_t steps[%(sz)s];
        ssize_t cur;
        int err;

        if (%(inp)s->ga.nd != %(sz)s) {
            PyErr_SetString(PyExc_IndexError, "invalid index");
            %(fail)s
        }
        """ % dict(sz=len(idx_list), inp=inp, fail=sub['fail'])

        def fix_idx(idx):
            if idx is None:
                return "0", 1
            elif isinstance(idx, (numpy.integer, int)):
                return str(idx), 0
            elif isinstance(idx, gof.Type):
                return indices.pop(0), 0
            else:
                assert 0, idx

        for i, idx in enumerate(idx_list):
            if isinstance(idx, slice):
                start, start_n = fix_idx(idx.start)
                stop, stop_n = fix_idx(idx.stop)
                step, step_n = fix_idx(idx.step)
                print >>sio, """
                starts[%(i)s] = %(start)s;
                stops[%(i)s] = %(stop)s;
                steps[%(i)s] = %(step)s;
                if (fix_indices(&starts[%(i)s], &stops[%(i)s], &steps[%(i)s],
                                %(start_n)s, %(stop_n)s, %(step_n)s,
                                %(inp)s->ga.dimensions[%(i)s]) == -1) {
                    %(fail)s
                }
                """ % dict(i=i, start=start, stop=stop, step=step,
                           start_n=start_n, stop_n=stop_n, step_n=step_n,
                           fail=sub['fail'], inp=inp)
            else:
                if isinstance(idx, gof.Type):
                    start = indices.pop(0)
                elif isinstance(idx, (numpy.integer, int)):
                    start = idx
                else:
                    assert 0, idx
                print >>sio, """
                cur = %(start)s;
                if (cur < 0)
                    cur += %(inp)s->ga.dimensions[%(i)s];
                starts[%(i)s] = cur;
                steps[%(i)s] = 0;
                """ % dict(i=i, start=start, fail=sub['fail'], inp=inp)

        print >>sio, """
        Py_XDECREF(%(out)s);
        %(out)s = pygpu_index(%(inp)s, starts, stops, steps);
        if (!%(out)s) { %(fail)s }
""" % dict(name=name, fail=sub['fail'], inp=inp, out=outputs[0])

        return sio.getvalue()

    def c_code_cache_version(self):
        return (6,)


class GpuIncSubtensor(IncSubtensor):
    """
    Implement IncSubtensor on the gpu.

    Note: The optimization to make this inplace is in tensor/opt.
          The same optimization handles IncSubtensor and GpuIncSubtensor.
          This Op has c_code too; it inherits tensor.IncSubtensor's c_code.
          The helper methods like do_type_checking, copy_of_x, etc. specialize
          the c_code for this Op.
    """
    def c_headers(self):
        return self.iadd_node.op.c_headers()

    def c_compiler(self):
        return self.iadd_node.op.c_compiler()

    def c_init_code(self):
        return self.iadd_node.op.c_init_code()

    def make_node(self, x, y, *inputs):
        x = as_gpuarray_variable(x)
        y = as_gpuarray_variable(y)
        rval = tensor.IncSubtensor.make_node(self, x, y, *inputs)
        op = copy.copy(self)
        ret = gof.Apply(op, [x, y] + rval.inputs[2:], [x.type()])
        op.create_iadd_node(ret)
        return ret

    def create_iadd_node(self, node):
        # We store a iadd_node in the op that contain the info needed
        # for the inplace add.
        cop = theano.tensor.inplace.add_inplace
        gop = GpuElemwise(cop.scalar_op, copy.copy(cop.inplace_pattern),
                          "Gpu" + cop.name, cop.nfunc_spec)
        y = node.inputs[1]
        xview = y.type()
        iadd_node = gop(xview, y).owner
        self.iadd_node = iadd_node

    def perform(self, node, inputs, out_):
        out, = out_
        x, y = inputs[:2]
        indices = list(reversed(inputs[2:]))

        def convert(entry):
            if isinstance(entry, gof.Type):
                rval = indices.pop()
                return rval
            elif isinstance(entry, slice):
                return slice(convert(entry.start),
                             convert(entry.stop),
                             convert(entry.step))
            else:
                return entry

        cdata = tuple(map(convert, self.idx_list))
        if len(cdata) == 1:
            cdata = cdata[0]
        if not self.inplace:
            x = x.copy()
        sub_x = x.__getitem__(cdata)
        if sub_x.shape:
            # we've sliced out an N-D tensor with N > 0
            if not self.set_instead_of_inc:
                #sub_x += y
                pygpu.elemwise.ielemwise2(sub_x, '+', y,  broadcast=False)
            else:
                #sub_x += -sub_x + y
                x.__setitem__(cdata, y)
        else:
            # scalar case
            if not self.set_instead_of_inc:
                #x.__setitem__(cdata, sub_x + y)
                tmp = pygpu.elemwise.elemwise2(sub_x, '+', y,  sub_x,
                                               broadcast=False)
                x.__setitem__(cdata, tmp)
            else:
                x.__setitem__(cdata, y)
        out[0] = x

    def __setstate__(self, d):
        self.__dict__.update(d)
        owner = getattr(self.__dict__, "owner", None)
        if owner:
            op.create_iadd_node(owner)

    def __getstate__(self):
        d = copy.copy(self.__dict__)
        if "iadd_node" in d:
            d.pop('iadd_node')
        return d

    def do_type_checking(self, node):
        """ Should raise NotImplementedError if c_code does not support
        the types involved in this node.
        """

        if not isinstance(node.inputs[0].type, GpuArrayType):
            raise NotImplementedError()

    def copy_of_x(self, x):
        """
            :param x: a string giving the name of a C variable
                pointing to an array

            :return: C code expression to make a copy of x

            Base class uses `PyArrayObject *`, subclasses may override for
            different types of arrays.
        """
        return """pygpu_copy(%(x)s, GA_ANY_ORDER)""" % locals()

    def decl_view(self):
        return "PyGpuArrayObject* zview = NULL;"

    def make_view_array(self, x, view_ndim):
        """//TODO
            :param x: a string identifying an array to be viewed
            :param view_ndim: a string specifying the number of dimensions
                to have in the view

            This doesn't need to actually set up the view with the
            right indexing; we'll do that manually later.
        """
        ret = """
        size_t dims[%(view_ndim)s];
        for(int i=0; i<%(view_ndim)s; i++)
            dims[i] = xview_dims[i];
        zview = pygpu_fromgpudata(%(x)s->ga.data,
                                  xview_offset,
                                  %(x)s->ga.typecode,
                                  %(view_ndim)s,
                                  dims,
                                  xview_strides,
                                  pygpu_default_context(),
                                  1,
                                  (PyObject *)%(x)s,
                                  (PyObject *)&PyGpuArrayType);
        """ % locals()
        return ret

    def get_helper_c_code_args(self):
        """ Return a dictionary of arguments to use with helper_c_code"""
        return {'c_prefix': 'PyGpuArray',
                'strides_mul': 1
                }

    def copy_into(self, view, source):
        """
            view: string, C code expression for an array
            source: string, C code expression for an array

            returns a C code expression to copy source into view, and
            return 0 on success
        """
        return """GpuArray_setarray(&%(view)s->ga, &%(source)s->ga)""" % locals()

    def c_support_code_apply(self, node, nodename):
        gop = self.iadd_node.op
        sub_name = nodename + "_add_to_zview"
        ret = gop.c_support_code_apply(self.iadd_node, sub_name)
        ret += """
        PyGpuArrayObject* inc_sub_iadd_%(nodename)s(PyGpuArrayObject* dst,
                                                    PyGpuArrayObject* src){
           PyGpuArrayObject* ret = NULL;
        """ % locals()
        # def c_code(self, node, name, inputs, outputs, sub):
        inputs = ["dst", "src"]
        outputs = ["ret"]
        sub = {"fail": "return NULL;"}
        ret += gop.c_code(self.iadd_node, sub_name, inputs, outputs, sub)
        ret += """
            return dst;
        }
        """
        return ret

    def add_to_zview(self, nodename, x, fail):
        # TODO
        return """
        PyGpuArrayObject * add_result = inc_sub_iadd_%(nodename)s(zview, %(x)s);

        if (! add_result )
        {
            Py_DECREF(zview);
            %(fail)s;
        }
        else
        {
            Py_DECREF(add_result);
        }
        """ % locals()

    def c_code_cache_version(self):
        parent_version = super(GpuIncSubtensor, self).c_code_cache_version()
        elemwise_version = self.iadd_node.c_code_cache_version()
        if not parent_version or not elemwise_version:
            return
        return parent_version + elemwise_version + (1,)


class GpuAdvancedIncSubtensor1(HideC, tensor.AdvancedIncSubtensor1):
    """
    Implement AdvancedIncSubtensor1 on the gpu.
    """
    def make_node(self, x, y, ilist):
        x_ = as_gpuarray_variable(x)
        y_ = as_gpuarray_variable(y)
        ilist_ = tensor.as_tensor_variable(ilist)

        assert x_.type.dtype == y_.type.dtype
        assert x_.type.ndim >= y_.type.ndim

        if ilist_.type.dtype[:3] not in ('int', 'uin'):
            raise TypeError('index must be integers')
        if ilist_.type.ndim != 1:
            raise TypeError('index must be vector')
        if x_.type.ndim == 0:
            raise TypeError('cannot index into a scalar')
        if y_.type.ndim > x_.type.ndim:
            if self.set_instead_of_inc:
                opname = 'set'
            else:
                opname = 'increment'
            raise TypeError(
                'cannot %s x subtensor with ndim=%s'
                ' by y with ndim=%s to x subtensor with ndim=%s ' % (
                    opname, x_.type.ndim, y_.type.ndim))

        return gof.Apply(self, [x_, y_, ilist_], [x_.type()])

    def getInplElemwiseAdditionKernel(self, a, b):
        a_arg = pygpu.tools.as_argument(a, 'a')
        b_arg = pygpu.tools.as_argument(b, 'b')
        args = [a_arg, b_arg]
        oper = "a[i] = a[i] + %(b)s" % {'b': b_arg.expr()}
        k = pygpu.elemwise.ElemwiseKernel(a.context, args, oper)
        return k

    # We can't use the parent version that loops on each index
    # as we also need to loop when set_instead_of_inc is True and the
    # parent doesn't loop in that case.
    def perform(self, node, inp, out_):
        # TODO opt to make this inplace
        x, y, idx = inp
        out, = out_

        # Make sure idx is not a GpuArray otherwise we cannot use its content
        # to index x and y
        if isinstance(idx, gpuarray.GpuArray):
            idx = numpy.asarray(idx)

        if not self.inplace:
            x = x.copy()
        if self.set_instead_of_inc:
            assert y.ndim <= x.ndim   # Should be guaranteed by `make_node`
            if y.ndim == x.ndim:
                assert len(y) == len(idx)
                for (j, i) in enumerate(idx):
                    x[i] = y[j]
            else:
                for i in idx:
                    x[i] = y
        else:
            # If `y` has as many dimensions as `x`, then we want to iterate
            # jointly on `x` and `y`. Otherwise, it means `y` should be
            # broadcasted to fill all relevant rows of `x`.
            assert y.ndim <= x.ndim   # Should be guaranteed by `make_node`

            if len(idx) == 0:
                pass
            elif y.ndim == x.ndim:
                assert len(y) == len(idx)

                k = self.getInplElemwiseAdditionKernel(x[0], y[0])

                for (j, i) in enumerate(idx):
                    k(x[i], y[j], broadcast=False)
            else:
                nb_dims_to_add = (x.ndim - 1) - y.ndim
                reshaped_y = y.reshape((1,)*nb_dims_to_add + y.shape)
                k = self.getInplElemwiseAdditionKernel(x[0],
                                                       reshaped_y)

                for i in idx:
                    k(x[i], reshaped_y, broadcast=True)

        out[0] = x


class GpuAdvancedIncSubtensor1_dev20(GpuAdvancedIncSubtensor1):
    """Implement AdvancedIncSubtensor1 on the gpu, but use function
    only avail on compute capability 2.0 and more recent.
    """

    def __init__(self, inplace=False, set_instead_of_inc=False):
        # The python implementation in the parent class is not applicable here
        GpuAdvancedIncSubtensor1.__init__(self, inplace, set_instead_of_inc)

    def make_node(self, x, y, ilist):
        """It defer from GpuAdvancedIncSubtensor1 in that it make sure
        the index are of type long.
        """
        x_ = as_gpuarray_variable(x)
        y_ = as_gpuarray_variable(y)
        ilist_ = as_gpuarray_variable(ilist)

        assert x_.type.dtype == y_.type.dtype
        assert x_.type.ndim >= y_.type.ndim

        if ilist_.type.dtype[:3] not in ('int', 'uin'):
            raise TypeError('index must be integers')
        if ilist_.type.ndim != 1:
            raise TypeError('index must be vector')
        if x_.type.ndim == 0:
            raise TypeError('cannot index into a scalar')
        if y_.type.ndim > x_.type.ndim:
            if self.set_instead_of_inc:
                opname = 'set'
            else:
                opname = 'increment'
            raise TypeError(
                'cannot %s x subtensor with ndim=%s'
                ' by y with ndim=%s to x subtensor with ndim=%s ' % (
                    opname, x_.type.ndim, y_.type.ndim))

        return gof.Apply(self, [x_, y_, ilist_], [x_.type()])

    def c_code_cache_version(self):
        return (2,)

    def c_headers(self):
        return ['cuda.h', '<gpuarray/extension.h>', '<numpy_compat.h>',
                '<gpuarray/ext_cuda.h>']

    def c_compiler(self):
        return NVCC_compiler

    def c_init_code(self):
        return ['setup_ext_cuda();']

    def c_code(self, node, name, inputs, outputs, sub):
        active_device_no = theano.sandbox.cuda.active_device_number()
        device_properties = theano.sandbox.cuda.device_properties
        compute_capability = device_properties(active_device_no)['major']
        if ((self.set_instead_of_inc) or
            (node.inputs[0].ndim != node.inputs[1].ndim) or
            (node.inputs[0].ndim != 2) or
            (compute_capability < 2)):
            raise NotImplementedError("This case does not have C code yet.")

        x = inputs[0]
        y = inputs[1]
        ind = inputs[2]
        out = outputs[0]
        fail = sub['fail']
        inplace = int(self.inplace)
        return """
        Py_XDECREF(%(out)s);
        if (!%(inplace)s) {
            %(out)s = (PyGpuArrayObject*)pygpu_copy(%(x)s, GA_C_ORDER);
        } else {
            %(out)s = %(x)s;
            Py_XINCREF(%(out)s);
        }

        GpuArray_vector_add_fast(%(out)s, %(y)s, %(ind)s);

        if (!%(out)s) {
            %(fail)s
        }
        """ % locals()

    def c_support_code_apply(self, node, nodename):
        dtype_x = node.inputs[0].dtype
        dtype_y = node.inputs[1].dtype
        dtype_ind = node.inputs[2].dtype
        dtype_out = node.outputs[0].dtype
        itemsize_x = numpy.dtype(dtype_x).itemsize
        itemsize_y = numpy.dtype(dtype_y).itemsize
        itemsize_ind = numpy.dtype(dtype_ind).itemsize
        itemsize_out = numpy.dtype(dtype_out).itemsize
        return """

        __global__ void k_vector_add_fast(int numRowsX,
                                          int numColsX,
                                          int stridesX0,
                                          int stridesX1,
                                          npy_%(dtype_x)s *X,
                                          int numRowsY,
                                          int numColsY,
                                          int stridesY0,
                                          int stridesY1,
                                          npy_%(dtype_y)s *Y,
                                          int numIndices,
                                          int stridesIndices,
                                          npy_%(dtype_ind)s *indices_arr)
        {
             for (int i = (blockIdx.x); i < numIndices; i += gridDim.x)
             {
                  for(int j = (threadIdx.x); j < numColsX;j += blockDim.x)
                  {
                      int x_row = indices_arr[i * stridesIndices];
                      int y_row = i;
                      atomicAdd(&X[(x_row * stridesX0) + (j * stridesX1)], Y[(y_row * stridesY0) + (j * stridesY1)]);
                  }
             }
             return;
        }

        void GpuArray_vector_add_fast(PyGpuArrayObject* py_self,
                                      PyGpuArrayObject* py_other,
                                      PyGpuArrayObject *indices_arr)
        {
                int num_threads_per_block = std::min(PyGpuArray_DIMS(py_self)[1],
                                                     (size_t)256);
                int num_blocks = std::min(PyGpuArray_SIZE(indices_arr),
                                          (size_t)4096);

                dim3 n_blocks(num_blocks);
                dim3 n_threads(num_threads_per_block);

                k_vector_add_fast<<<n_blocks, n_threads>>>(
                        PyGpuArray_DIMS(py_self)[0],
                        PyGpuArray_DIMS(py_self)[1],
                        PyGpuArray_STRIDES(py_self)[0] / %(itemsize_x)s,
                        PyGpuArray_STRIDES(py_self)[1] / %(itemsize_x)s,
                        (npy_%(dtype_x)s*)(
                            ((char *)cuda_get_ptr(py_self->ga.data)) +
                            py_self->ga.offset),
                        PyGpuArray_DIMS(py_other)[0],
                        PyGpuArray_DIMS(py_other)[1],
                        PyGpuArray_STRIDES(py_other)[0] / %(itemsize_y)s,
                        PyGpuArray_STRIDES(py_other)[1] / %(itemsize_y)s,
                        (npy_%(dtype_x)s*)(
                            ((char *)cuda_get_ptr(py_other->ga.data)) +
                            py_other->ga.offset),
                        PyGpuArray_DIMS(indices_arr)[0],
                        PyGpuArray_STRIDES(indices_arr)[0] / %(itemsize_ind)s,
                        (npy_%(dtype_ind)s*)(
                            ((char *)cuda_get_ptr(indices_arr->ga.data)) +
                            indices_arr->ga.offset)
                );
                return;
        }

        """ % locals()
