import gdb
import sys

if sys.version_info[0] > 2:
    Iterator = object
else:
    # "Polyfill" for Python2 Iterator interface
    class Iterator:
        def next(self):
            return self.__next__()


class ThrustVectorPrinter(gdb.printing.PrettyPrinter):
    "Print a thrust::*_vector"

    class _host_accessible_iterator(Iterator):
        def __init__(self, start, size):
            self.item = start
            self.size = size
            self.count = 0

        def __iter__(self):
            return self

        def __next__(self):
            if self.count >= self.size:
                raise StopIteration
            elt = self.item.dereference()
            count = self.count
            self.item = self.item + 1
            self.count = self.count + 1
            return ('[%d]' % count, elt)

    class _device_iterator(Iterator):
        def __init__(self, start, size):
            self.exec = exec
            self.item = start
            self.size = size
            self.count = 0
            self.buffer = None
            self.sizeof = self.item.dereference().type.sizeof
            self.buffer_start = 0
            # At most 1 MB or size, at least 1
            self.buffer_size = min(size, max(1, 2 ** 20 // self.sizeof))
            self.buffer = gdb.parse_and_eval(
                '(void*)malloc(%s)' % (self.buffer_size * self.sizeof))
            self.buffer.fetch_lazy()
            self.buffer_count = self.buffer_size
            self.update_buffer()

        def update_buffer(self):
            if self.buffer_count >= self.buffer_size:
                self.buffer_item = gdb.parse_and_eval(
                    hex(self.buffer)).cast(self.item.type)
                self.buffer_count = 0
                self.buffer_start = self.count
                device_addr = hex(self.item.dereference().address)
                buffer_addr = hex(self.buffer)
                size = min(self.buffer_size, self.size -
                           self.buffer_start) * self.sizeof
                status = gdb.parse_and_eval(
                    '(cudaError)cudaMemcpy(%s, %s, %d, cudaMemcpyDeviceToHost)' % (buffer_addr, device_addr, size))
                if status != 0:
                    raise gdb.MemoryError(
                        'memcpy from device failed: %s' % status)

        def __del__(self):
            gdb.parse_and_eval('(void)free(%s)' %
                               hex(self.buffer)).fetch_lazy()

        def __iter__(self):
            return self

        def __next__(self):
            if self.count >= self.size:
                raise StopIteration
            self.update_buffer()
            elt = self.buffer_item.dereference()
            self.buffer_item = self.buffer_item + 1
            self.buffer_count = self.buffer_count + 1
            count = self.count
            self.item = self.item + 1
            self.count = self.count + 1
            return ('[%d]' % count, elt)

    def __init__(self, val):
        self.val = val
        self.pointer = val['m_storage']['m_begin']['m_iterator']
        self.size = int(val['m_size'])
        self.capacity = int(val['m_storage']['m_size'])
        self.is_device = False
        if str(self.pointer.type).startswith("thrust::device_ptr"):
            self.pointer = self.pointer['m_iterator']
            self.is_device = True

    def children(self):
        if self.is_device:
            return self._device_iterator(self.pointer, self.size)
        else:
            return self._host_accessible_iterator(self.pointer, self.size)

    def to_string(self):
        typename = str(self.val.type)
        return ('%s of length %d, capacity %d' % (typename, self.size, self.capacity))

    def display_hint(self):
        return 'array'


class ThrustReferencePrinter(gdb.printing.PrettyPrinter):
    "Print a thrust::device_reference"

    def __init__(self, val):
        self.val = val
        self.pointer = val['ptr']['m_iterator']
        self.type = self.pointer.dereference().type
        sizeof = self.type.sizeof
        self.buffer = gdb.parse_and_eval('(void*)malloc(%s)' % sizeof)
        device_addr = hex(self.pointer)
        buffer_addr = hex(self.buffer)
        status = gdb.parse_and_eval('(cudaError)cudaMemcpy(%s, %s, %d, cudaMemcpyDeviceToHost)' % (
            buffer_addr, device_addr, sizeof))
        if status != 0:
            raise gdb.MemoryError('memcpy from device failed: %s' % status)
        self.buffer_val = gdb.parse_and_eval(
            hex(self.buffer)).cast(self.pointer.type).dereference()

    def __del__(self):
        gdb.parse_and_eval('(void)free(%s)' % hex(self.buffer)).fetch_lazy()

    def children(self):
        return []

    def to_string(self):
        typename = str(self.val.type)
        return ('(%s) @%s: %s' % (typename, self.pointer, self.buffer_val))

    def display_hint(self):
        return None


def METHOD_NAME(val):
    if not str(val.type.unqualified()).startswith('thrust::'):
        return None
    suffix = str(val.type.unqualified())[8:]
    if suffix.startswith('host_vector') or suffix.startswith('device_vector'):
        return ThrustVectorPrinter(val)
    elif int(gdb.VERSION.split(".")[0]) >= 10 and suffix.startswith('device_reference'):
        return ThrustReferencePrinter(val)
    return None


gdb.pretty_printers.append(METHOD_NAME)