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"""GDB support for Blink types.

Add this to your gdb by amending your ~/.gdbinit as follows:
  python
  import sys
  sys.path.insert(0, "/path/to/blink/tools/gdb/")
  import blink
"""

from __future__ import print_function

import gdb
import re
import struct

def guess_string_length(ptr):
    """Guess length of string pointed by ptr.

    Returns a tuple of (length, an error message).
    """
    # Try to guess at the length.
    for i in range(0, 2048):
        try:
            if int((ptr + i).dereference()) == 0:
                return i, ''
        except RuntimeError:
            # We indexed into inaccessible memory; give up.
            return i, ' (gdb hit inaccessible memory)'
    return 256, ' (gdb found no trailing NUL)'


def ustring_to_string(ptr, length=None):
    """Convert a pointer to UTF-16 data into a Python string encoded with utf-8.

    ptr and length are both gdb.Value objects.
    If length is unspecified, will guess at the length."""
    error_message = ''
    if length is None:
        length, error_message = guess_string_length(ptr)
    else:
        length = int(length)
    char_vals = [int((ptr + i).dereference()) for i in range(length)]
    string = struct.pack('H' * length, *char_vals).decode('utf-16', 'replace').encode('utf-8')
    return string + error_message


def lstring_to_string(ptr, length=None):
    """Convert a pointer to LChar* data into a Python (non-Unicode) string.

    ptr and length are both gdb.Value objects.
    If length is unspecified, will guess at the length."""
    error_message = ''
    if length is None:
        length, error_message = guess_string_length(ptr)
    else:
        length = int(length)
    string = ''.join([chr((ptr + i).dereference()) for i in range(length)])
    return string + error_message


class StringPrinter(object):
    "Shared code between different string-printing classes"
    def __init__(self, val):
        self.val = val

    def display_hint(self):
        return 'string'


class UCharStringPrinter(StringPrinter):
    "Print a UChar*; we must guess at the length"
    def to_string(self):
        return ustring_to_string(self.val)


class LCharStringPrinter(StringPrinter):
    "Print a LChar*; we must guess at the length"
    def to_string(self):
        return lstring_to_string(self.val)


class WTFAtomicStringPrinter(StringPrinter):
    "Print a WTF::AtomicString"
    def to_string(self):
        return self.val['string_']


class WTFCStringPrinter(StringPrinter):
    "Print a WTF::CString"
    def to_string(self):
        # The CString holds a buffer, which is a refptr to a WTF::CStringBuffer.
        buf_ptr = self.val['buffer_']['ptr_']
        if not buf_ptr:
            return 0
        data = (buf_ptr + 1).cast(gdb.lookup_type('char').pointer())
        length = self.val['buffer_']['ptr_']['length_']
        return ''.join([chr((data + i).dereference()) for i in range(length)])


class WTFStringImplPrinter(StringPrinter):
    "Print a WTF::StringImpl"
    def get_length(self):
        return self.val['length_']

    def to_string(self):
        chars_start = self.val.address + 1
        if self.is_8bit():
            return lstring_to_string(chars_start.cast(gdb.lookup_type('char').pointer()),
                                     self.get_length())
        return ustring_to_string(chars_start.cast(gdb.lookup_type('UChar').pointer()),
                                 self.get_length())

    def is_8bit(self):
        return self.val['is_8bit_']


class WTFStringPrinter(StringPrinter):
    "Print a WTF::String"
    def stringimpl_ptr(self):
        return self.val['impl_']['ptr_']

    def get_length(self):
        if not self.stringimpl_ptr():
            return 0
        return WTFStringImplPrinter(self.stringimpl_ptr().dereference()).get_length()

    def to_string(self):
        if not self.stringimpl_ptr():
            return '(null)'
        return self.stringimpl_ptr().dereference()


class blinkKURLPrinter(StringPrinter):
    "Print a blink::KURL"
    def to_string(self):
        return WTFStringPrinter(self.val['string_']).to_string()


class blinkLayoutUnitPrinter:
    "Print a blink::LayoutUnit"
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return "%.14gpx" % (self.val['value_'] / 64.0)


class blinkLayoutSizePrinter:
    "Print a blink::LayoutSize"
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return 'LayoutSize(%s, %s)' % (
            blinkLayoutUnitPrinter(self.val['width_']).to_string(),
            blinkLayoutUnitPrinter(self.val['height_']).to_string())


class blinkLayoutPointPrinter:
    "Print a blink::LayoutPoint"
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return 'LayoutPoint(%s, %s)' % (
            blinkLayoutUnitPrinter(self.val['x_']).to_string(),
            blinkLayoutUnitPrinter(self.val['y_']).to_string())


class blinkQualifiedNamePrinter(StringPrinter):
    "Print a blink::QualifiedName"

    def __init__(self, val):
        super(blinkQualifiedNamePrinter, self).__init__(val)
        self.prefix_length = 0
        self.length = 0
        if self.val['impl_']:
            self.prefix_printer = WTFStringPrinter(
                self.val['impl_']['ptr_']['prefix_']['string_'])
            self.local_name_printer = WTFStringPrinter(
                self.val['impl_']['ptr_']['local_name_']['string_'])
            self.prefix_length = self.prefix_printer.get_length()
            if self.prefix_length > 0:
                self.length = (self.prefix_length + 1 +
                    self.local_name_printer.get_length())
            else:
                self.length = self.local_name_printer.get_length()

    def get_length(self):
        return self.length

    def to_string(self):
        if self.get_length() == 0:
            return "(null)"
        else:
            if self.prefix_length > 0:
                return (self.prefix_printer.to_string() + ":" +
                    self.local_name_printer.to_string())
            else:
                return self.local_name_printer.to_string()


class BlinkPixelsAndPercentPrinter:
    "Print a blink::PixelsAndPercent value"
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return "(%gpx, %g%%)" % (self.val['pixels'], self.val['percent'])


class BlinkLengthPrinter:
    """Print a blink::Length."""
    def __init__(self, val):
        self.val = val

    def to_string(self):
        ltype = self.val['type_']
        if self.val['is_float_']:
            val = self.val['float_value_']
        else:
            val = int(self.val['int_value_'])

        quirk = ''
        if self.val['quirk_']:
            quirk = ', quirk=true'

        if ltype == 0:
            return 'Length(Auto)'
        if ltype == 1:
            return 'Length(%g%%, Percent%s)' % (val, quirk)
        if ltype == 2:
            return 'Length(%g, Fixed%s)' % (val, quirk)
        if ltype == 3:
            return 'Length(MinContent)'
        if ltype == 4:
            return 'Length(MaxContent)'
        if ltype == 5:
            return 'Length(FillAvailable)'
        if ltype == 6:
            return 'Length(FitContent)'
        if ltype == 7:
            # Would like to print pixelsAndPercent() but can't call member
            # functions - https://sourceware.org/bugzilla/show_bug.cgi?id=13326
            return 'Length(Calculated)'
        if ltype == 8:
            return 'Length(ExtendToZoom)'
        if ltype == 9:
            return 'Length(DeviceWidth)'
        if ltype == 10:
            return 'Length(DeviceHeight)'
        if ltype == 11:
            return 'Length(MaxSizeNone)'
        return 'Length(unknown type %i)' % ltype


class WTFVectorPrinter:
    """Pretty Printer for a WTF::Vector.

    The output of this pretty printer is similar to the output of std::vector's
    pretty printer, which is bundled in gcc.

    Example gdb session should look like:
    (gdb) p v
    $3 = WTF::Vector of length 7, capacity 16 = {7, 17, 27, 37, 47, 57, 67}
    (gdb) set print elements 3
    (gdb) p v
    $6 = WTF::Vector of length 7, capacity 16 = {7, 17, 27...}
    (gdb) set print array
    (gdb) p v
    $7 = WTF::Vector of length 7, capacity 16 = {
      7,
      17,
      27
      ...
    }
    (gdb) set print elements 200
    (gdb) p v
    $8 = WTF::Vector of length 7, capacity 16 = {
      7,
      17,
      27,
      37,
      47,
      57,
      67
    }
    """

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

        def __iter__(self):
            return self

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

        # Python version < 3 compatibility:
        def next(self):
            return self.__next__()

    def __init__(self, val):
        self.val = val

    def children(self):
        start = self.val['buffer_']
        return self.Iterator(start, start + self.val['size_'])

    def to_string(self):
        return ('%s of length %d, capacity %d'
                % ('WTF::Vector', self.val['size_'], self.val['capacity_']))

    def display_hint(self):
        return 'array'


# Copied from //tools/gdb/gdb_chrome.py
def typed_ptr(ptr):
    """Prints a pointer along with its exact type.

    By default, gdb would print just the address, which takes more
    steps to interpret.
    """
    # Returning this as a cast expression surrounded by parentheses
    # makes it easier to cut+paste inside of gdb.
    return '((%s)%s)' % (ptr.dynamic_type, ptr)


class BlinkDataRefPrinter:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return 'DataRef(%s)' % (str(self.val['data_']))


def add_pretty_printers():
    pretty_printers = (
        (re.compile("^WTF::Vector<.*>$"), WTFVectorPrinter),
        (re.compile("^WTF::AtomicString$"), WTFAtomicStringPrinter),
        (re.compile("^WTF::CString$"), WTFCStringPrinter),
        (re.compile("^WTF::String$"), WTFStringPrinter),
        (re.compile("^WTF::StringImpl$"), WTFStringImplPrinter),
        (re.compile("^blink::KURL$"), blinkKURLPrinter),
        (re.compile("^blink::LayoutUnit$"), blinkLayoutUnitPrinter),
        (re.compile("^blink::LayoutPoint$"), blinkLayoutPointPrinter),
        (re.compile("^blink::LayoutSize$"), blinkLayoutSizePrinter),
        (re.compile("^blink::QualifiedName$"), blinkQualifiedNamePrinter),
        (re.compile("^blink::PixelsAndPercent$"), BlinkPixelsAndPercentPrinter),
        (re.compile("^blink::Length$"), BlinkLengthPrinter),
        (re.compile("^blink::DataRef<.*>$"), BlinkDataRefPrinter),
    )

    def lookup_function(val):
        """Function used to load pretty printers; will be passed to GDB."""
        type = val.type
        if type.code == gdb.TYPE_CODE_REF:
            type = type.target()
        type = type.unqualified().strip_typedefs()
        tag = type.tag
        if tag:
            for function, pretty_printer in pretty_printers:
                if function.search(tag):
                    return pretty_printer(val)

        if type.code == gdb.TYPE_CODE_PTR:
            name = str(type.target().unqualified())
            if name == 'UChar':
                return UCharStringPrinter(val)
            if name == 'LChar':
                return LCharStringPrinter(val)
        return None

    gdb.pretty_printers.append(lookup_function)


add_pretty_printers()


class PrintPathToRootCommand(gdb.Command):
    """Command for printing Blink Node trees.

    Usage: printpathtoroot variable_name"""

    def __init__(self):
        super(PrintPathToRootCommand, self).__init__("printpathtoroot",
            gdb.COMMAND_SUPPORT,
            gdb.COMPLETE_NONE)

    def invoke(self, arg, from_tty):
        element_type = gdb.lookup_type('blink::Element')
        node_type = gdb.lookup_type('blink::Node')
        frame = gdb.selected_frame()
        try:
            val = gdb.Frame.read_var(frame, arg)
        except:
            print("No such variable, or invalid type")
            return

        target_type = str(val.type.target().strip_typedefs())
        if target_type == str(node_type):
            stack = []
            while val:
                stack.append([val,
                              val.cast(element_type.pointer()).dereference()[
                                  'tag_name_']])
                val = val.dereference()['parent_']

            padding = ''
            while len(stack) > 0:
                pair = stack.pop()
                print(padding, pair[1], pair[0])
                padding = padding + '  '
        else:
            print('Sorry: I don\'t know how to deal with %s yet.' % target_type)


PrintPathToRootCommand()