"""
Intermediate representation (IR) code classes.
"""


class Module:
    """ Container unit for variables and functions. """
    def __init__(self, name):
        self.name = name
        self.functions = []
        self.variables = []

    def __repr__(self):
        return 'module {0}'.format(self.name)

    def add_function(self, f):
        """ Add a function to this module """
        self.functions.append(f)

    def addVariable(self, v):
        self.variables.append(v)

    def getVariables(self):
        return self.variables

    Variables = property(getVariables)

    def getFunctions(self):
        return self.functions

    Functions = property(getFunctions)

    def findFunction(self, name):
        for f in self.funcs:
            if f.name == name:
                return f
        raise KeyError(name)

    getFunction = findFunction


class Function:
    """ Represents a function. """
    def __init__(self, name, module=None):
        self.name = name
        self.entry = Block('{}_entry'.format(name))
        self.entry.function = self
        self.epiloog = Block('{}_epilog'.format(name))
        self.epiloog.function = self
        self.epiloog.addInstruction(Terminator())
        self.return_value = Temp('{}_retval'.format(name))
        self.arguments = []
        self.localvars = []
        if module:
            module.add_function(self)

    def __repr__(self):
        args = ','.join(str(a) for a in self.arguments)
        return 'function i32 {}({})'.format(self.name, args)

    def add_block(self, bb):
        #self.bbs.append(bb)
        bb.function = self

    def removeBlock(self, bb):
        #self.bbs.remove(bb)
        bb.function = None

    def getBlocks(self):
        bbs = [self.entry]
        worklist = [self.entry]
        while worklist:
            b = worklist.pop()
            for sb in b.Successors:
                if sb not in bbs:
                    bbs.append(sb)
                    worklist.append(sb)
        bbs.remove(self.entry)
        if self.epiloog in bbs:
            bbs.remove(self.epiloog)
        bbs.insert(0, self.entry)
        bbs.append(self.epiloog)
        return bbs

    def findBasicBlock(self, name):
        for bb in self.bbs:
            if bb.name == name:
                return bb
        raise KeyError(name)

    Blocks = property(getBlocks)

    @property
    def Entry(self):
        return self.entry

    def check(self):
        for b in self.Blocks:
            b.check()

    def addParameter(self, p):
        assert type(p) is Parameter
        p.num = len(self.arguments)
        self.arguments.append(p)

    def addLocal(self, l):
        assert type(l) is LocalVariable
        self.localvars.append(l)


class Block:
    """
        Uninterrupted sequence of instructions with a label at the start.
    """
    def __init__(self, name, function=None):
        self.name = name
        self.function = function
        self.instructions = []

    parent = property(lambda s: s.function)

    def __repr__(self):
        return '{0}:'.format(self.name)

    def addInstruction(self, i):
        i.parent = self
        assert not isinstance(self.LastInstruction, LastStatement)
        self.instructions.append(i)

    def replaceInstruction(self, i1, i2):
        idx = self.instructions.index(i1)
        i1.parent = None
        i1.delete()
        i2.parent = self
        self.instructions[idx] = i2

    def removeInstruction(self, i):
        i.parent = None
        #i.delete()
        self.instructions.remove(i)

    @property
    def Instructions(self):
        return self.instructions

    @property
    def LastInstruction(self):
        if not self.Empty:
            return self.instructions[-1]

    @property
    def Empty(self):
        return len(self.instructions) == 0

    @property
    def FirstInstruction(self):
        return self.instructions[0]

    def getSuccessors(self):
        if not self.Empty:
            return self.LastInstruction.Targets
        return []

    Successors = property(getSuccessors)

    def getPredecessors(self):
        preds = []
        for bb in self.parent.Blocks:
            if self in bb.Successors:
                preds.append(bb)
        return preds

    Predecessors = property(getPredecessors)

    def precedes(self, other):
        raise NotImplementedError()


# Instructions:

class Expression:
    """ Base class for an expression """
    pass


class Const(Expression):
    """ Represents a constant value """
    def __init__(self, value):
        self.value = value

    def __repr__(self):
        return 'Const {}'.format(self.value)


class Call(Expression):
    """ Call a function with some arguments """
    def __init__(self, f, arguments):
        self.f = f
        self.arguments = arguments

    def __repr__(self):
        args = ', '.join([str(arg) for arg in self.arguments])
        return '{}({})'.format(self.f, args)


# Data operations
class Binop(Expression):
    """ Generic binary operation """
    ops = ['+', '-', '*', '/', '|', '&', '<<', '>>']

    def __init__(self, value1, operation, value2):
        assert operation in Binop.ops
        self.a = value1
        self.b = value2
        self.operation = operation

    def __repr__(self):
        a, b = self.a, self.b
        return '({} {} {})'.format(a, self.operation, b)


def Add(a, b):
    """ Add a and b """
    return Binop(a, '+', b)


def Sub(a, b):
    """ Substract b from a """
    return Binop(a, '-', b)


def Mul(a, b):
    """ Multiply a by b """
    return Binop(a, '*', b)


def Div(a, b):
    """ Divide a in b pieces """
    return Binop(a, '/', b)


class Eseq(Expression):
    """ Sequence of instructions where the last is an expression """
    def __init__(self, stmt, e):
        self.stmt = stmt
        self.e = e

    def __repr__(self):
        return '({}, {})'.format(self.stmt, self.e)


class Alloc(Expression):
    """ Allocates space on the stack """
    def __init__(self):
        super().__init__()

    def __repr__(self):
        return 'Alloc'


class Variable(Expression):
    def __init__(self, name):
        self.name = name

    def __repr__(self):
        return 'Var {}'.format(self.name)


class LocalVariable(Variable):
    def __repr__(self):
        return 'Local {}'.format(self.name)


class Parameter(Variable):
    def __repr__(self):
        return 'Param {}'.format(self.name)


class Temp(Expression):
    """ Temporary storage, same as register """
    def __init__(self, name):
        self.name = name

    def __repr__(self):
        return 'TMP_{}'.format(self.name)


class Mem(Expression):
    """ Memory access """
    def __init__(self, e):
        self.e = e

    def __repr__(self):
        return '[{}]'.format(self.e)


class Statement:
    """ Base class for all instructions. """
    @property
    def IsTerminator(self):
        return isinstance(self, LastStatement)


class Move(Statement):
    """ Move source to destination """
    def __init__(self, dst, src):
        self.dst = dst
        self.src = src

    def __repr__(self):
        return '{} = {}'.format(self.dst, self.src)


class Exp(Statement):
    def __init__(self, e):
        self.e = e

    def __repr__(self):
        return '{}'.format(self.e)


# Branching:
class LastStatement(Statement):
    def changeTarget(self, old, new):
        idx = self.Targets.index(old)
        self.Targets[idx] = new


class Terminator(LastStatement):
    """ Instruction that terminates the terminal block """
    def __init__(self):
        self.Targets = []

    def __repr__(self):
        return 'Terminator'


class Jump(LastStatement):
    """ Jump statement to some target location """
    def __init__(self, target):
        self.Targets = [target]

    def setTarget(self, t):
        self.Targets[0] = t

    target = property(lambda s: s.Targets[0], setTarget)

    def __repr__(self):
        return 'JUMP {}'.format(self.target.name)


class CJump(LastStatement):
    """ Conditional jump to true or false labels. """
    conditions = ['==', '<', '>', '>=', '<=', '!=']

    def __init__(self, a, cond, b, lab_yes, lab_no):
        assert cond in CJump.conditions
        self.a = a
        self.cond = cond
        self.b = b
        self.Targets = [lab_yes, lab_no]

    lab_yes = property(lambda s: s.Targets[0])
    lab_no = property(lambda s: s.Targets[1])

    def __repr__(self):
        return 'IF {} {} {} THEN {} ELSE {}'\
               .format(self.a, self.cond, self.b, self.lab_yes, self.lab_no)