# DExTer : Debugging Experience Tester
# ~~~~~~   ~         ~~         ~   ~~
#
# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
# See https://llvm.org/LICENSE.txt for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
"""Interface for communicating with the LLDB debugger via its python interface.
"""

import imp
import os
from subprocess import CalledProcessError, check_output, STDOUT
import sys

from dex.debugger.DebuggerBase import DebuggerBase
from dex.dextIR import FrameIR, LocIR, StepIR, StopReason, ValueIR
from dex.dextIR import StackFrame, SourceLocation, ProgramState
from dex.utils.Exceptions import DebuggerException, LoadDebuggerException
from dex.utils.ReturnCode import ReturnCode


class LLDB(DebuggerBase):
    def __init__(self, context, *args):
        self.lldb_executable = context.options.lldb_executable
        self._debugger = None
        self._target = None
        self._process = None
        self._thread = None
        # Map {id (int): condition (str)} for breakpoints which have a
        # condition. See get_triggered_breakpoint_ids usage for more info.
        self._breakpoint_conditions = {}
        super(LLDB, self).__init__(context, *args)

    def _custom_init(self):
        self._debugger = self._interface.SBDebugger.Create()
        self._debugger.SetAsync(False)
        self._target = self._debugger.CreateTargetWithFileAndArch(
            self.context.options.executable, self.context.options.arch)
        if not self._target:
            raise LoadDebuggerException(
                'could not create target for executable "{}" with arch:{}'.
                format(self.context.options.executable,
                       self.context.options.arch))

    def _custom_exit(self):
        if getattr(self, '_process', None):
            self._process.Kill()
        if getattr(self, '_debugger', None) and getattr(self, '_target', None):
            self._debugger.DeleteTarget(self._target)

    def _translate_stop_reason(self, reason):
        if reason == self._interface.eStopReasonNone:
            return None
        if reason == self._interface.eStopReasonBreakpoint:
            return StopReason.BREAKPOINT
        if reason == self._interface.eStopReasonPlanComplete:
            return StopReason.STEP
        if reason == self._interface.eStopReasonThreadExiting:
            return StopReason.PROGRAM_EXIT
        if reason == self._interface.eStopReasonException:
            return StopReason.ERROR
        return StopReason.OTHER

    def _load_interface(self):
        try:
            args = [self.lldb_executable, '-P']
            pythonpath = check_output(
                args, stderr=STDOUT).rstrip().decode('utf-8')
        except CalledProcessError as e:
            raise LoadDebuggerException(str(e), sys.exc_info())
        except OSError as e:
            raise LoadDebuggerException(
                '{} ["{}"]'.format(e.strerror, self.lldb_executable),
                sys.exc_info())

        if not os.path.isdir(pythonpath):
            raise LoadDebuggerException(
                'path "{}" does not exist [result of {}]'.format(
                    pythonpath, args), sys.exc_info())

        try:
            module_info = imp.find_module('lldb', [pythonpath])
            return imp.load_module('lldb', *module_info)
        except ImportError as e:
            msg = str(e)
            if msg.endswith('not a valid Win32 application.'):
                msg = '{} [Are you mixing 32-bit and 64-bit binaries?]'.format(
                    msg)
            raise LoadDebuggerException(msg, sys.exc_info())

    @classmethod
    def get_name(cls):
        return 'lldb'

    @classmethod
    def get_option_name(cls):
        return 'lldb'

    @property
    def version(self):
        try:
            return self._interface.SBDebugger_GetVersionString()
        except AttributeError:
            return None

    def clear_breakpoints(self):
        self._target.DeleteAllBreakpoints()

    def _add_breakpoint(self, file_, line):
        return self._add_conditional_breakpoint(file_, line, None)

    def _add_conditional_breakpoint(self, file_, line, condition):
        bp = self._target.BreakpointCreateByLocation(file_, line)
        if not bp:
            raise DebuggerException(
                  'could not add breakpoint [{}:{}]'.format(file_, line))
        id = bp.GetID()
        if condition:
            bp.SetCondition(condition)
            assert id not in self._breakpoint_conditions
            self._breakpoint_conditions[id] = condition
        return id

    def _evaulate_breakpoint_condition(self, id):
        """Evaluate the breakpoint condition and return the result.

        Returns True if a conditional breakpoint with the specified id cannot
        be found (i.e. assume it is an unconditional breakpoint).
        """
        try:
            condition = self._breakpoint_conditions[id]
        except KeyError:
            # This must be an unconditional breakpoint.
            return True
        valueIR = self.evaluate_expression(condition)
        return valueIR.type_name == 'bool' and valueIR.value == 'true'

    def get_triggered_breakpoint_ids(self):
        # Breakpoints can only have been triggered if we've hit one.
        stop_reason = self._translate_stop_reason(self._thread.GetStopReason())
        if stop_reason != StopReason.BREAKPOINT:
            return []
        breakpoint_ids = set()
        # When the stop reason is eStopReasonBreakpoint, GetStopReasonDataCount
        # counts all breakpoints associated with the location that lldb has
        # stopped at, regardless of their condition. I.e. Even if we have two
        # breakpoints at the same source location that have mutually exclusive
        # conditions, both will be counted by GetStopReasonDataCount when
        # either condition is true. Check each breakpoint condition manually to
        # filter the list down to breakpoints that have caused this stop.
        #
        # Breakpoints have two data parts: Breakpoint ID, Location ID. We're
        # only interested in the Breakpoint ID so we skip every other item.
        for i in range(0, self._thread.GetStopReasonDataCount(), 2):
            id = self._thread.GetStopReasonDataAtIndex(i)
            if self._evaulate_breakpoint_condition(id):
                breakpoint_ids.add(id)
        return breakpoint_ids

    def delete_breakpoint(self, id):
        bp = self._target.FindBreakpointByID(id)
        if not bp:
            # The ID is not valid.
            raise KeyError
        try:
            del self._breakpoint_conditions[id]
        except KeyError:
            # This must be an unconditional breakpoint.
            pass
        self._target.BreakpointDelete(id)

    def launch(self):
        self._process = self._target.LaunchSimple(None, None, os.getcwd())
        if not self._process or self._process.GetNumThreads() == 0:
            raise DebuggerException('could not launch process')
        if self._process.GetNumThreads() != 1:
            raise DebuggerException('multiple threads not supported')
        self._thread = self._process.GetThreadAtIndex(0)
        assert self._thread, (self._process, self._thread)

    def step(self):
        self._thread.StepInto()

    def go(self) -> ReturnCode:
        self._process.Continue()
        return ReturnCode.OK

    def _get_step_info(self, watches, step_index):
        frames = []
        state_frames = []

        for i in range(0, self._thread.GetNumFrames()):
            sb_frame = self._thread.GetFrameAtIndex(i)
            sb_line = sb_frame.GetLineEntry()
            sb_filespec = sb_line.GetFileSpec()

            try:
                path = os.path.join(sb_filespec.GetDirectory(),
                                    sb_filespec.GetFilename())
            except (AttributeError, TypeError):
                path = None

            function = self._sanitize_function_name(sb_frame.GetFunctionName())

            loc_dict = {
                'path': path,
                'lineno': sb_line.GetLine(),
                'column': sb_line.GetColumn()
            }
            loc = LocIR(**loc_dict)

            frame = FrameIR(
                function=function, is_inlined=sb_frame.IsInlined(), loc=loc)

            if any(
                    name in (frame.function or '')  # pylint: disable=no-member
                    for name in self.frames_below_main):
                break

            frames.append(frame)

            state_frame = StackFrame(function=frame.function,
                                     is_inlined=frame.is_inlined,
                                     location=SourceLocation(**loc_dict),
                                     watches={})
            for expr in map(
                lambda watch, idx=i: self.evaluate_expression(watch, idx),
                watches):
                state_frame.watches[expr.expression] = expr
            state_frames.append(state_frame)

        if len(frames) == 1 and frames[0].function is None:
            frames = []
            state_frames = []

        reason = self._translate_stop_reason(self._thread.GetStopReason())

        return StepIR(
            step_index=step_index, frames=frames, stop_reason=reason,
            program_state=ProgramState(state_frames))

    @property
    def is_running(self):
        # We're not running in async mode so this is always False.
        return False

    @property
    def is_finished(self):
        return not self._thread.GetFrameAtIndex(0)

    @property
    def frames_below_main(self):
        return ['__scrt_common_main_seh', '__libc_start_main']

    def evaluate_expression(self, expression, frame_idx=0) -> ValueIR:
        result = self._thread.GetFrameAtIndex(frame_idx
            ).EvaluateExpression(expression)
        error_string = str(result.error)

        value = result.value
        could_evaluate = not any(s in error_string for s in [
            "Can't run the expression locally",
            "use of undeclared identifier",
            "no member named",
            "Couldn't lookup symbols",
            "reference to local variable",
            "invalid use of 'this' outside of a non-static member function",
        ])

        is_optimized_away = any(s in error_string for s in [
            'value may have been optimized out',
        ])

        is_irretrievable = any(s in error_string for s in [
            "couldn't get the value of variable",
            "couldn't read its memory",
            "couldn't read from memory",
            "Cannot access memory at address",
            "invalid address (fault address:",
        ])

        if could_evaluate and not is_irretrievable and not is_optimized_away:
            assert error_string == 'success', (error_string, expression, value)
            # assert result.value is not None, (result.value, expression)

        if error_string == 'success':
            error_string = None

        # attempt to find expression as a variable, if found, take the variable
        # obj's type information as it's 'usually' more accurate.
        var_result = self._thread.GetFrameAtIndex(frame_idx).FindVariable(expression)
        if str(var_result.error) == 'success':
            type_name = var_result.type.GetDisplayTypeName()
        else:
            type_name = result.type.GetDisplayTypeName()

        return ValueIR(
            expression=expression,
            value=value,
            type_name=type_name,
            error_string=error_string,
            could_evaluate=could_evaluate,
            is_optimized_away=is_optimized_away,
            is_irretrievable=is_irretrievable,
        )