"""A flow graph representation for Python bytecode"""

import dis

import types

import sys

from compiler import misc

from compiler.consts \

     import CO_OPTIMIZED, CO_NEWLOCALS, CO_VARARGS, CO_VARKEYWORDS

class FlowGraph:

    def __init__(self):

        self.current = self.entry = Block()

        self.exit = Block("exit")

        self.blocks = misc.Set()

        self.blocks.add(self.entry)

        self.blocks.add(self.exit)

    def startBlock(self, block):

        if self._debug:

            if self.current:

                print "end", repr(self.current)

                print "    next", self.current.next

                print "   ", self.current.get_children()

            print repr(block)

        self.current = block

    def nextBlock(self, block=None):

        # XXX think we need to specify when there is implicit transfer

        # from one block to the next.  might be better to represent this

        # with explicit JUMP_ABSOLUTE instructions that are optimized

        # out when they are unnecessary.

        #

        # I think this strategy works: each block has a child

        # designated as "next" which is returned as the last of the

        # children.  because the nodes in a graph are emitted in

        # reverse post order, the "next" block will always be emitted

        # immediately after its parent.

        # Worry: maintaining this invariant could be tricky

        if block is None:

            block = self.newBlock()

        # Note: If the current block ends with an unconditional

        # control transfer, then it is incorrect to add an implicit

        # transfer to the block graph.  The current code requires

        # these edges to get the blocks emitted in the right order,

        # however. :-(  If a client needs to remove these edges, call

        # pruneEdges().

        self.current.addNext(block)

        self.startBlock(block)

    def newBlock(self):

        b = Block()

        self.blocks.add(b)

        return b

    def startExitBlock(self):

        self.startBlock(self.exit)

    _debug = 0

    def _enable_debug(self):

        self._debug = 1

    def _disable_debug(self):

        self._debug = 0

    def emit(self, *inst):

        if self._debug:

            print "\t", inst

        if inst[0] in ['RETURN_VALUE', 'YIELD_VALUE']:

            self.current.addOutEdge(self.exit)

        if len(inst) == 2 and isinstance(inst[1], Block):

            self.current.addOutEdge(inst[1])

        self.current.emit(inst)

    def getBlocksInOrder(self):

        """Return the blocks in reverse postorder

        i.e. each node appears before all of its successors

        """

        # XXX make sure every node that doesn't have an explicit next

        # is set so that next points to exit

        for b in self.blocks.elements():

            if b is self.exit:

                continue

            if not b.next:

                b.addNext(self.exit)

        order = dfs_postorder(self.entry, {})

        order.reverse()

        self.fixupOrder(order, self.exit)

        # hack alert

        if not self.exit in order:

            order.append(self.exit)

        return order

    def fixupOrder(self, blocks, default_next):

        """Fixup bad order introduced by DFS."""

        # XXX This is a total mess.  There must be a better way to get

        # the code blocks in the right order.

        self.fixupOrderHonorNext(blocks, default_next)

        self.fixupOrderForward(blocks, default_next)

    def fixupOrderHonorNext(self, blocks, default_next):

        """Fix one problem with DFS.

        The DFS uses child block, but doesn't know about the special

        "next" block.  As a result, the DFS can order blocks so that a

        block isn't next to the right block for implicit control

        transfers.

        """

        index = {}

        for i in range(len(blocks)):

            index[blocks[i]] = i

        for i in range(0, len(blocks) - 1):

            b = blocks[i]

            n = blocks[i + 1]

            if not b.next or b.next[0] == default_next or b.next[0] == n:

                continue

            # The blocks are in the wrong order.  Find the chain of

            # blocks to insert where they belong.

            cur = b

            chain = []

            elt = cur

            while elt.next and elt.next[0] != default_next:

                chain.append(elt.next[0])

                elt = elt.next[0]

            # Now remove the blocks in the chain from the current

            # block list, so that they can be re-inserted.

            l = []

            for b in chain:

                assert index[b] > i

                l.append((index[b], b))

            l.sort()

            l.reverse()

            for j, b in l:

                del blocks[index[b]]

            # Insert the chain in the proper location

            blocks[i:i + 1] = [cur] + chain

            # Finally, re-compute the block indexes

            for i in range(len(blocks)):

                index[blocks[i]] = i

    def fixupOrderForward(self, blocks, default_next):

        """Make sure all JUMP_FORWARDs jump forward"""

        index = {}

        chains = []

        cur = []

        for b in blocks:

            index[b] = len(chains)

            cur.append(b)

            if b.next and b.next[0] == default_next:

                chains.append(cur)

                cur = []

        chains.append(cur)

        while 1:

            constraints = []

            for i in range(len(chains)):

                l = chains[i]

                for b in l:

                    for c in b.get_children():

                        if index[c] < i:

                            forward_p = 0

                            for inst in b.insts:

                                if inst[0] == 'JUMP_FORWARD':

                                    if inst[1] == c:

                                        forward_p = 1

                            if not forward_p:

                                continue

                            constraints.append((index[c], i))

            if not constraints:

                break

            # XXX just do one for now

            # do swaps to get things in the right order

            goes_before, a_chain = constraints[0]

            assert a_chain > goes_before

            c = chains[a_chain]

            chains.remove(c)

            chains.insert(goes_before, c)

        del blocks[:]

        for c in chains:

            for b in c:

                blocks.append(b)

    def getBlocks(self):

        return self.blocks.elements()

    def getRoot(self):

        """Return nodes appropriate for use with dominator"""

        return self.entry

    def getContainedGraphs(self):

        l = []

        for b in self.getBlocks():

            l.extend(b.getContainedGraphs())

        return l

def dfs_postorder(b, seen):

    """Depth-first search of tree rooted at b, return in postorder"""

    order = []

    seen[b] = b

    for c in b.get_children():

        if seen.has_key(c):

            continue

        order = order + dfs_postorder(c, seen)

    order.append(b)

    return order

class Block:

    _count = 0

    def __init__(self, label=''):

        self.insts = []

        self.inEdges = misc.Set()

        self.outEdges = misc.Set()

        self.label = label

        self.bid = Block._count

        self.next = []

        Block._count = Block._count + 1

    def __repr__(self):

        if self.label:

            return "<block %s id=%d>" % (self.label, self.bid)

        else:

            return "<block id=%d>" % (self.bid)

    def __str__(self):

        insts = map(str, self.insts)

        return "<block %s %d:\n%s>" % (self.label, self.bid,

                                       '\n'.join(insts))

    def emit(self, inst):

        op = inst[0]

        if op[:4] == 'JUMP':

            self.outEdges.add(inst[1])

        self.insts.append(inst)

    def getInstructions(self):

        return self.insts

    def addInEdge(self, block):

        self.inEdges.add(block)

    def addOutEdge(self, block):

        self.outEdges.add(block)

    def addNext(self, block):

        self.next.append(block)

        assert len(self.next) == 1, map(str, self.next)

    _uncond_transfer = ('RETURN_VALUE', 'RAISE_VARARGS', 'YIELD_VALUE',

                        'JUMP_ABSOLUTE', 'JUMP_FORWARD', 'CONTINUE_LOOP')

    def pruneNext(self):

        """Remove bogus edge for unconditional transfers

        Each block has a next edge that accounts for implicit control

        transfers, e.g. from a JUMP_IF_FALSE to the block that will be

        executed if the test is true.

        These edges must remain for the current assembler code to

        work. If they are removed, the dfs_postorder gets things in

        weird orders.  However, they shouldn't be there for other

        purposes, e.g. conversion to SSA form.  This method will

        remove the next edge when it follows an unconditional control

        transfer.

        """

        try:

            op, arg = self.insts[-1]

        except (IndexError, ValueError):

            return

        if op in self._uncond_transfer:

            self.next = []

    def get_children(self):

        if self.next and self.next[0] in self.outEdges:

            self.outEdges.remove(self.next[0])

        return self.outEdges.elements() + self.next

    def getContainedGraphs(self):

        """Return all graphs contained within this block.

        For example, a MAKE_FUNCTION block will contain a reference to

        the graph for the function body.

        """

        contained = []

        for inst in self.insts:

            if len(inst) == 1:

                continue

            op = inst[1]

            if hasattr(op, 'graph'):

                contained.append(op.graph)

        return contained

# flags for code objects

# the FlowGraph is transformed in place; it exists in one of these states

RAW = "RAW"

FLAT = "FLAT"

CONV = "CONV"

DONE = "DONE"

class PyFlowGraph(FlowGraph):

    super_init = FlowGraph.__init__

    def __init__(self, name, filename, args=(), optimized=0, klass=None):

        self.super_init()

        self.name = name

        self.filename = filename

        self.docstring = None

        self.args = args # XXX

        self.argcount = getArgCount(args)

        self.klass = klass

        if optimized:

            self.flags = CO_OPTIMIZED | CO_NEWLOCALS

        else:

            self.flags = 0

        self.consts = []

        self.names = []

        # Free variables found by the symbol table scan, including

        # variables used only in nested scopes, are included here.

        self.freevars = []

        self.cellvars = []

        # The closure list is used to track the order of cell

        # variables and free variables in the resulting code object.

        # The offsets used by LOAD_CLOSURE/LOAD_DEREF refer to both

        # kinds of variables.

        self.closure = []

        self.varnames = list(args) or []

        for i in range(len(self.varnames)):

            var = self.varnames[i]

            if isinstance(var, TupleArg):

                self.varnames[i] = var.getName()

        self.stage = RAW

    def setDocstring(self, doc):

        self.docstring = doc

    def setFlag(self, flag):

        self.flags = self.flags | flag

        if flag == CO_VARARGS:

            self.argcount = self.argcount - 1

    def checkFlag(self, flag):

        if self.flags & flag:

            return 1

    def setFreeVars(self, names):

        self.freevars = list(names)

    def setCellVars(self, names):

        self.cellvars = names

    def getCode(self):

        """Get a Python code object"""

        assert self.stage == RAW

        self.computeStackDepth()

        self.flattenGraph()

        assert self.stage == FLAT

        self.convertArgs()

        assert self.stage == CONV

        self.makeByteCode()

        assert self.stage == DONE

        return self.newCodeObject()

    def dump(self, io=None):

        if io:

            save = sys.stdout

            sys.stdout = io

        pc = 0

        for t in self.insts:

            opname = t[0]

            if opname == "SET_LINENO":

                print

            if len(t) == 1:

                print "\t", "%3d" % pc, opname

                pc = pc + 1

            else:

                print "\t", "%3d" % pc, opname, t[1]

                pc = pc + 3

        if io:

            sys.stdout = save

    def computeStackDepth(self):

        """Compute the max stack depth.

        Approach is to compute the stack effect of each basic block.

        Then find the path through the code with the largest total

        effect.

        """

        depth = {}

        exit = None

        for b in self.getBlocks():

            depth[b] = findDepth(b.getInstructions())

        seen = {}

        def max_depth(b, d):

            if seen.has_key(b):

                return d

            seen[b] = 1

            d = d + depth[b]

            children = b.get_children()

            if children:

                return max([max_depth(c, d) for c in children])

            else:

                if not b.label == "exit":

                    return max_depth(self.exit, d)

                else:

                    return d

        self.stacksize = max_depth(self.entry, 0)

    def flattenGraph(self):

        """Arrange the blocks in order and resolve jumps"""

        assert self.stage == RAW

        self.insts = insts = []

        pc = 0

        begin = {}

        end = {}

        for b in self.getBlocksInOrder():

            begin[b] = pc

            for inst in b.getInstructions():

                insts.append(inst)

                if len(inst) == 1:

                    pc = pc + 1

                elif inst[0] != "SET_LINENO":

                    # arg takes 2 bytes

                    pc = pc + 3

            end[b] = pc

        pc = 0

        for i in range(len(insts)):

            inst = insts[i]

            if len(inst) == 1:

                pc = pc + 1

            elif inst[0] != "SET_LINENO":

                pc = pc + 3

            opname = inst[0]

            if self.hasjrel.has_elt(opname):

                oparg = inst[1]

                offset = begin[oparg] - pc

                insts[i] = opname, offset

            elif self.hasjabs.has_elt(opname):

                insts[i] = opname, begin[inst[1]]

        self.stage = FLAT

    hasjrel = misc.Set()

    for i in dis.hasjrel:

        hasjrel.add(dis.opname[i])

    hasjabs = misc.Set()

    for i in dis.hasjabs:

        hasjabs.add(dis.opname[i])

    def convertArgs(self):

        """Convert arguments from symbolic to concrete form"""

        assert self.stage == FLAT

        self.consts.insert(0, self.docstring)

        self.sort_cellvars()

        for i in range(len(self.insts)):

            t = self.insts[i]

            if len(t) == 2:

                opname, oparg = t

                conv = self._converters.get(opname, None)

                if conv:

                    self.insts[i] = opname, conv(self, oparg)

        self.stage = CONV

    def sort_cellvars(self):

        """Sort cellvars in the order of varnames and prune from freevars.

        """

        cells = {}

        for name in self.cellvars:

            cells[name] = 1

        self.cellvars = [name for name in self.varnames

                         if cells.has_key(name)]

        for name in self.cellvars:

            del cells[name]

        self.cellvars = self.cellvars + cells.keys()

        self.closure = self.cellvars + self.freevars

    def _lookupName(self, name, list):

        """Return index of name in list, appending if necessary

        This routine uses a list instead of a dictionary, because a

        dictionary can't store two different keys if the keys have the

        same value but different types, e.g. 2 and 2L.  The compiler

        must treat these two separately, so it does an explicit type

        comparison before comparing the values.

        """

        t = type(name)

        for i in range(len(list)):

            if t == type(list[i]) and list[i] == name:

                return i

        end = len(list)

        list.append(name)

        return end

    _converters = {}

    def _convert_LOAD_CONST(self, arg):

        if hasattr(arg, 'getCode'):

            arg = arg.getCode()

        return self._lookupName(arg, self.consts)

    def _convert_LOAD_FAST(self, arg):

        self._lookupName(arg, self.names)

        return self._lookupName(arg, self.varnames)

    _convert_STORE_FAST = _convert_LOAD_FAST

    _convert_DELETE_FAST = _convert_LOAD_FAST

    def _convert_LOAD_NAME(self, arg):

        if self.klass is None:

            self._lookupName(arg, self.varnames)

        return self._lookupName(arg, self.names)

    def _convert_NAME(self, arg):

        if self.klass is None:

            self._lookupName(arg, self.varnames)

        return self._lookupName(arg, self.names)