# This file is part of Androguard.
#
# Copyright (C) 2014 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS-IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

'''This file is a simplified version of writer.py that outputs an AST instead of source code.'''
import struct

from androguard.decompiler.dad import basic_blocks, instruction, opcode_ins

def array_access(arr, ind): return ['ArrayAccess', [arr, ind]]
def array_creation(tn, params, dim): return ['ArrayCreation', [tn] + params, dim]
def array_initializer(params, tn=None): return ['ArrayInitializer', params, tn]
def assignment(lhs, rhs): return ['Assignment', [lhs, rhs]]
def binary_infix(op, left, right): return ['BinaryInfix', op, left, right]
def cast(tn, arg): return ['Cast', [tn, arg]]
def field_access(triple, left): return ['FieldAccess', triple, left]
def literal(result, tt): return ['Literal', result, tt]
def local(name): return ['Local', name]

def method_invocation(triple, name, base, params):
    if base is None:
        return ['MethodInvocation', triple, name, False, params]
    return ['MethodInvocation', triple, name, True, [base]+params]

def parenthesis(expr): return ['Parenthesis', [expr]]
def typen(baset, dim): return ['TypeName', (baset, dim)]
def unary_prefix(op, left): return ['UnaryPrefix', op, left]
def var_decl(typen, var): return [typen, var]

def dummy(*args): return ['Dummy', args]
################################################################################

def expression_stmt(expr): return ['ExpressionStatement', expr]
def local_decl_stmt(expr, decl): return ['LocalDeclarationStatement', expr, decl]
def return_stmt(expr): return ['ReturnStatement', expr]
def throw_stmt(expr): return ['ThrowStatement', expr]
def jump_stmt(keyword): return ['JumpStatement', keyword, None]

def loop_stmt(isdo, cond_expr, body):
    type_ = 'DoStatement' if isdo else 'WhileStatement'
    return [type_, None, cond_expr, body]

def try_stmt(tryb, pairs): return ['TryStatement', None, tryb, pairs]
def if_stmt(cond_expr, scopes): return ['IfStatement', None, cond_expr, scopes]
def switch_stmt(cond_expr, ksv_pairs):
    return ['SwitchStatement', None, cond_expr, ksv_pairs]

# Create empty statement block (statements to be appended later)
# Note, the code below assumes this can be modified in place
def statement_block(): return ['BlockStatement', None, []]

# Add a statement to the end of a statement block
def _append(sb, stmt):
    assert(sb[0] == 'BlockStatement')
    if stmt is not None:
        sb[2].append(stmt)

################################################################################
TYPE_DESCRIPTOR = {
    'V': 'void',
    'Z': 'boolean',
    'B': 'byte',
    'S': 'short',
    'C': 'char',
    'I': 'int',
    'J': 'long',
    'F': 'float',
    'D': 'double',
}

def parse_descriptor(desc):
    dim = 0
    while desc and desc[0] == '[':
        desc = desc[1:]
        dim += 1

    if desc in TYPE_DESCRIPTOR:
        return typen('.'+TYPE_DESCRIPTOR[desc], dim)
    if desc and desc[0] == 'L' and desc[-1] == ';':
        return typen(desc[1:-1], dim)
    # invalid descriptor (probably None)
    return dummy(str(desc))

# Note: the literal_foo functions (and dummy) are also imported by decompile.py
def literal_string(s):
    escapes = {
        '\0':'\\0',
        '\t':'\\t',
        '\r':'\\r',
        '\n':'\\n',
        '"':'\\"',
        '\\':'\\\\'
    }

    buf = ['"']
    for c in s.decode('utf8'):
        if c in escapes:
            buf.append(escapes[c])
        elif ' ' <= c < '\x7f':
            buf.append(c)
        else:
            buf.append('\u{:04x}'.format(ord(c)))
    buf.append('"')
    return literal(''.join(buf), ('java/lang/String', 0))

def literal_class(desc):
    return literal(parse_descriptor(desc), ('java/lang/Class', 0))

def literal_bool(b): return literal(str(b).lower(), ('.boolean', 0))
def literal_int(b): return literal(str(b), ('.int', 0))
def literal_long(b): return literal(str(b)+'L', ('.long', 0))
def literal_float(f): return literal(str(f)+'f', ('.float', 0))
def literal_double(f): return literal(str(f), ('.double', 0))
def literal_null(): return literal('null', ('.null', 0))

def visit_decl(var, init_expr=None):
    t = parse_descriptor(var.get_type())
    v = local('v{}'.format(var.name))
    return local_decl_stmt(init_expr, var_decl(t, v))

def visit_arr_data(value):
    data = value.get_data()
    tab = []
    elem_size = value.element_width
    if elem_size == 4:
        for i in range(0, value.size * 4, 4):
            tab.append(struct.unpack('<i', data[i:i + 4])[0])
    else:  # FIXME: other cases
        for i in range(value.size):
            tab.append(struct.unpack('<b', data[i])[0])
    return array_initializer(map(literal_int, tab))

def visit_expr(op):
    if isinstance(op, instruction.ArrayLengthExpression):
        expr = visit_expr(op.var_map[op.array])
        return field_access([None, 'length', None], expr)
    if isinstance(op, instruction.ArrayLoadExpression):
        array_expr = visit_expr(op.var_map[op.array])
        index_expr = visit_expr(op.var_map[op.idx])
        return array_access(array_expr, index_expr)
    if isinstance(op, instruction.ArrayStoreInstruction):
        array_expr = visit_expr(op.var_map[op.array])
        index_expr = visit_expr(op.var_map[op.index])
        rhs = visit_expr(op.var_map[op.rhs])
        return assignment(array_access(array_expr, index_expr), rhs)

    if isinstance(op, instruction.AssignExpression):
        lhs = op.var_map.get(op.lhs)
        rhs = op.rhs
        if lhs is None:
            return visit_expr(rhs)
        return assignment(visit_expr(lhs), visit_expr(rhs))

    if isinstance(op, instruction.BaseClass):
        if op.clsdesc is None:
            assert(op.cls == "super")
            return local(op.cls)
        return parse_descriptor(op.clsdesc)
    if isinstance(op, instruction.BinaryExpression):
        lhs = op.var_map.get(op.arg1)
        rhs = op.var_map.get(op.arg2)
        expr = binary_infix(op.op, visit_expr(lhs), visit_expr(rhs))
        if not isinstance(op, instruction.BinaryCompExpression):
            expr = parenthesis(expr)
        return expr

    if isinstance(op, instruction.CheckCastExpression):
        lhs = op.var_map.get(op.arg)
        return parenthesis(cast(parse_descriptor(op.clsdesc), visit_expr(lhs)))
    if isinstance(op, instruction.ConditionalExpression):
        lhs = op.var_map.get(op.arg1)
        rhs = op.var_map.get(op.arg2)
        return binary_infix(op.op, visit_expr(lhs), visit_expr(rhs))
    if isinstance(op, instruction.ConditionalZExpression):
        arg = op.var_map[op.arg]
        if isinstance(arg, instruction.BinaryCompExpression):
            arg.op = op.op
            return visit_expr(arg)

        expr = visit_expr(arg)
        atype = arg.get_type()
        if atype == 'Z':
            if op.op == opcode_ins.Op.EQUAL:
                expr = unary_prefix('!', expr)
        elif atype in 'VBSCIJFD':
            expr = binary_infix(op.op, expr, literal_int(0))
        else:
            expr = binary_infix(op.op, expr, literal_null())
        return expr

    if isinstance(op, instruction.Constant):
        if op.type == 'Ljava/lang/String;':
            return literal_string(op.cst)
        elif op.type == 'Z':
            return literal_bool(op.cst == 0)
        elif op.type in 'ISCB':
            return literal_int(op.cst2)
        elif op.type in 'J':
            return literal_long(op.cst2)
        elif op.type in 'F':
            return literal_float(op.cst)
        elif op.type in 'D':
            return literal_double(op.cst)
        elif op.type == 'Ljava/lang/Class;':
            return literal_class(op.clsdesc)
        return dummy('???')

    if isinstance(op, instruction.FillArrayExpression):
        array_expr = visit_expr(op.var_map[op.reg])
        rhs = visit_arr_data(op.value)
        return assignment(array_expr, rhs)
    if isinstance(op, instruction.FilledArrayExpression):
        tn = parse_descriptor(op.type)
        params = [visit_expr(op.var_map[x]) for x in op.args]
        return array_initializer(params, tn)
    if isinstance(op, instruction.InstanceExpression):
        triple = op.clsdesc[1:-1], op.name, op.ftype
        expr = visit_expr(op.var_map[op.arg])
        return field_access(triple, expr)
    if isinstance(op, instruction.InstanceInstruction):
        triple = op.clsdesc[1:-1], op.name, op.atype
        lhs = field_access(triple, visit_expr(op.var_map[op.lhs]))
        rhs = visit_expr(op.var_map[op.rhs])
        return assignment(lhs, rhs)

    if isinstance(op, instruction.InvokeInstruction):
        base = op.var_map[op.base]
        params = [op.var_map[arg] for arg in op.args]
        params = map(visit_expr, params)
        if op.name == '<init>':
            if isinstance(base, instruction.ThisParam):
                return method_invocation(op.triple, 'this', None, params)
            elif isinstance(base, instruction.NewInstance):
                return ['ClassInstanceCreation', params, parse_descriptor(base.type)]
            else:
                assert(isinstance(base, instruction.Variable))
                # fallthrough to create dummy <init> call
        return method_invocation(op.triple, op.name, visit_expr(base), params)
    # for unmatched monitor instructions, just create dummy expressions
    if isinstance(op, instruction.MonitorEnterExpression):
        return dummy("monitor enter(", visit_expr(op.var_map[op.ref]), ")")
    if isinstance(op, instruction.MonitorExitExpression):
        return dummy("monitor exit(", visit_expr(op.var_map[op.ref]), ")")
    if isinstance(op, (instruction.MoveExpression, instruction.MoveResultExpression)):
        lhs = op.var_map.get(op.lhs)
        rhs = op.var_map.get(op.rhs)
        return assignment(visit_expr(lhs), visit_expr(rhs))
    if isinstance(op, instruction.NewArrayExpression):
        tn = parse_descriptor(op.type[1:])
        expr = visit_expr(op.var_map[op.size])
        return array_creation(tn, [expr], 1)
    # create dummy expression for unmatched newinstance
    if isinstance(op, instruction.NewInstance):
        return dummy("new ", parse_descriptor(op.type))
    if isinstance(op, instruction.Param):
        if isinstance(op, instruction.ThisParam):
            return local('this')
        return local('p{}'.format(op.v))
    if isinstance(op, instruction.StaticExpression):
        triple = op.clsdesc[1:-1], op.name, op.ftype
        return field_access(triple, parse_descriptor(op.clsdesc))
    if isinstance(op, instruction.StaticInstruction):
        triple = op.clsdesc[1:-1], op.name, op.ftype
        lhs = field_access(triple, parse_descriptor(op.clsdesc))
        rhs = visit_expr(op.var_map[op.rhs])
        return assignment(lhs, rhs)
    if isinstance(op, instruction.SwitchExpression):
        return visit_expr(op.var_map[op.src])
    if isinstance(op, instruction.UnaryExpression):
        lhs = op.var_map.get(op.arg)
        if isinstance(op, instruction.CastExpression):
            expr = cast(parse_descriptor(op.clsdesc), visit_expr(lhs))
        else:
            expr = unary_prefix(op.op, visit_expr(lhs))
        return parenthesis(expr)
    if isinstance(op, instruction.Variable):
        # assert(op.declared)
        return local('v{}'.format(op.name))
    return dummy('???')

def visit_ins(op, isCtor=False):
    if isinstance(op, instruction.ReturnInstruction):
        expr = None if op.arg is None else visit_expr(op.var_map[op.arg])
        return return_stmt(expr)
    elif isinstance(op, instruction.ThrowExpression):
        return throw_stmt(visit_expr(op.var_map[op.ref]))
    elif isinstance(op, instruction.NopExpression):
        return None

    # Local var decl statements
    if isinstance(op, (instruction.AssignExpression, instruction.MoveExpression, instruction.MoveResultExpression)):
        lhs = op.var_map.get(op.lhs)
        rhs = op.rhs if isinstance(op, instruction.AssignExpression) else op.var_map.get(op.rhs)
        if isinstance(lhs, instruction.Variable) and not lhs.declared:
            lhs.declared = True
            expr = visit_expr(rhs)
            return visit_decl(lhs, expr)

    # skip this() at top of constructors
    if isCtor and isinstance(op, instruction.AssignExpression):
        op2 = op.rhs
        if op.lhs is None and isinstance(op2, instruction.InvokeInstruction):
            if op2.name == '<init>' and len(op2.args) == 0:
                if isinstance(op2.var_map[op2.base], instruction.ThisParam):
                    return None

    return expression_stmt(visit_expr(op))

class JSONWriter(object):
    def __init__(self, graph, method):
        self.graph = graph
        self.method = method

        self.visited_nodes = set()
        self.loop_follow = [None]
        self.if_follow = [None]
        self.switch_follow = [None]
        self.latch_node = [None]
        self.try_follow = [None]
        self.next_case = None
        self.need_break = True
        self.constructor = False

        self.context = []

    # This class is created as a context manager so that it can be used like
    # with self as foo:
    #   ...
    # which pushes a statement block on to the context stack and assigns it to foo
    # within the with block, all added instructions will be added to foo
    def __enter__(self):
        self.context.append(statement_block())
        return self.context[-1]

    def __exit__(self, *args):
        self.context.pop()
        return False

    # Add a statement to the current context
    def add(self, val): _append(self.context[-1], val)

    def visit_ins(self, op):
        self.add(visit_ins(op, isCtor=self.constructor))

    # Note: this is a mutating operation
    def get_ast(self):
        m = self.method
        flags = m.access
        if 'constructor' in flags:
            flags.remove('constructor')
            self.constructor = True

        params = m.lparams[:]
        if 'static' not in m.access:
            params = params[1:]

        # DAD doesn't create any params for abstract methods
        if len(params) != len(m.params_type):
            assert('abstract' in flags and not params)
            params = range(len(m.params_type))

        paramdecls = []
        for ptype, name in zip(m.params_type, params):
            t = parse_descriptor(ptype)
            v = local('p{}'.format(name))
            paramdecls.append(var_decl(t, v))

        if self.graph is None:
            body = None
        else:
            with self as body:
                self.visit_node(self.graph.entry)

        return {
            'triple': m.triple,
            'flags': flags,
            'ret': parse_descriptor(m.type),
            'params': paramdecls,
            'comments': [],
            'body': body,
        }

    def _visit_condition(self, cond):
        left = self.get_cond(cond.cond1)
        right = self.get_cond(cond.cond2)
        op = '&&' if cond.isand else '||'
        res = binary_infix(op, left, right)
        if cond.isnot:
            res = unary_prefix('!', res)
        return res

    def get_cond(self, node):
        if isinstance(node, basic_blocks.ShortCircuitBlock):
            return self._visit_condition(node.cond)
        elif isinstance(node, basic_blocks.LoopBlock):
            return self.get_cond(node.cond)
        else:
            assert(type(node) == basic_blocks.CondBlock)
            assert(len(node.ins) == 1)
            return visit_expr(node.ins[-1])

    def visit_node(self, node):
        if node in (self.if_follow[-1], self.switch_follow[-1],
                    self.loop_follow[-1], self.latch_node[-1],
                    self.try_follow[-1]):
            return
        if not node.type.is_return and node in self.visited_nodes:
            return
        self.visited_nodes.add(node)
        for var in node.var_to_declare:
            if not var.declared:
                self.add(visit_decl(var))
            var.declared = True
        node.visit(self)

    def visit_loop_node(self, loop):
        isDo = cond_expr = body = None

        follow = loop.follow['loop']
        if loop.looptype.is_pretest:
            if loop.true is follow:
                loop.neg()
                loop.true, loop.false = loop.false, loop.true
            isDo = False
            cond_expr = self.get_cond(loop)

        elif loop.looptype.is_posttest:
            isDo = True
            self.latch_node.append(loop.latch)

        elif loop.looptype.is_endless:
            isDo = False
            cond_expr = literal_bool(True)

        with self as body:
            self.loop_follow.append(follow)
            if loop.looptype.is_pretest:
                self.visit_node(loop.true)
            else:
                self.visit_node(loop.cond)
            self.loop_follow.pop()

            if loop.looptype.is_pretest:
                pass
            elif loop.looptype.is_posttest:
                self.latch_node.pop()
                cond_expr = self.get_cond(loop.latch)
            else:
                self.visit_node(loop.latch)

        assert(cond_expr is not None and isDo is not None)
        self.add(loop_stmt(isDo, cond_expr, body))
        if follow is not None:
            self.visit_node(follow)

    def visit_cond_node(self, cond):
        cond_expr = None
        scopes = []

        follow = cond.follow['if']
        if cond.false is cond.true:
            self.visit_node(cond.true)
            return

        if cond.false is self.loop_follow[-1]:
            cond.neg()
            cond.true, cond.false = cond.false, cond.true

        if self.loop_follow[-1] in (cond.true, cond.false):
            cond_expr = self.get_cond(cond)
            with self as scope:
                self.add(jump_stmt('break'))
            scopes.append(scope)

            with self as scope:
                self.visit_node(cond.false)
            scopes.append(scope)

            self.add(if_stmt(cond_expr, scopes))
        elif follow is not None:
            if cond.true in (follow, self.next_case) or\
                                                cond.num > cond.true.num:
                             # or cond.true.num > cond.false.num:
                cond.neg()
                cond.true, cond.false = cond.false, cond.true
            self.if_follow.append(follow)
            if cond.true:  # in self.visited_nodes:
                cond_expr = self.get_cond(cond)
                with self as scope:
                    self.visit_node(cond.true)
                scopes.append(scope)

            is_else = not (follow in (cond.true, cond.false))
            if is_else and not cond.false in self.visited_nodes:
                with self as scope:
                    self.visit_node(cond.false)
                scopes.append(scope)
            self.if_follow.pop()

            self.add(if_stmt(cond_expr, scopes))
            self.visit_node(follow)
        else:
            cond_expr = self.get_cond(cond)
            with self as scope:
                self.visit_node(cond.true)
            scopes.append(scope)

            with self as scope:
                self.visit_node(cond.false)
            scopes.append(scope)
            self.add(if_stmt(cond_expr, scopes))

    def visit_switch_node(self, switch):
        lins = switch.get_ins()
        for ins in lins[:-1]:
            self.visit_ins(ins)
        switch_ins = switch.get_ins()[-1]

        cond_expr = visit_expr(switch_ins)
        ksv_pairs = []

        follow = switch.follow['switch']
        cases = switch.cases
        self.switch_follow.append(follow)
        default = switch.default
        for i, node in enumerate(cases):
            if node in self.visited_nodes:
                continue

            cur_ks = switch.node_to_case[node][:]
            if i + 1 < len(cases):
                self.next_case = cases[i + 1]
            else:
                self.next_case = None

            if node is default:
                cur_ks.append(None)
                default = None

            with self as body:
                self.visit_node(node)
                if self.need_break:
                    self.add(jump_stmt('break'))
                else:
                    self.need_break = True
            ksv_pairs.append((cur_ks, body))

        if default not in (None, follow):
            with self as body:
                self.visit_node(default)
            ksv_pairs.append(([None], body))

        self.add(switch_stmt(cond_expr, ksv_pairs))
        self.switch_follow.pop()
        self.visit_node(follow)

    def visit_statement_node(self, stmt):
        sucs = self.graph.sucs(stmt)
        for ins in stmt.get_ins():
            self.visit_ins(ins)
        if len(sucs) == 1:
            if sucs[0] is self.loop_follow[-1]:
                self.add(jump_stmt('break'))
            elif sucs[0] is self.next_case:
                self.need_break = False
            else:
                self.visit_node(sucs[0])

    def visit_try_node(self, try_node):
        with self as tryb:
            self.try_follow.append(try_node.follow)
            self.visit_node(try_node.try_start)

        pairs = []
        for catch_node in try_node.catch:
            if catch_node.exception_ins:
                ins = catch_node.exception_ins
                assert(isinstance(ins, instruction.MoveExceptionExpression))
                var = ins.var_map[ins.ref]
                var.declared = True

                ctype = var.get_type()
                name = 'v{}'.format(var.name)
            else:
                ctype = catch_node.catch_type
                name = '_'
            catch_decl = var_decl(parse_descriptor(ctype), local(name))

            with self as body:
                self.visit_node(catch_node.catch_start)
            pairs.append((catch_decl, body))

        self.add(try_stmt(tryb, pairs))
        self.visit_node(self.try_follow.pop())

    def visit_return_node(self, ret):
        self.need_break = False
        for ins in ret.get_ins():
            self.visit_ins(ins)

    def visit_throw_node(self, throw):
        for ins in throw.get_ins():
            self.visit_ins(ins)