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"""
Dummy TALES engine so that I can test out the TAL implementation.
"""

import re
import string
from TALVisitor import NAME_RE

class DummyEngine:

    def __init__(self):
        dict = {}
        self.locals = self.globals = dict
        self.stack = [dict]

    def beginScope(self):
        self.stack.append(self.locals)

    def endScope(self):
        assert len(self.stack) > 1, "more endScope() than beginScope() calls"
        self.locals = self.stack.pop()

    def setLocal(self, name, value):
        if self.locals is self.stack[-1]:
            # Unmerge this scope's locals from previous scope of first set
            self.locals = self.locals.copy()
        self.locals[name] = value

    def setGlobal(self, name, value):
        self.globals[name] = value

    def evaluate(self, expression):
        m = re.match(r"(%s):(.*)" % NAME_RE, expression)
        if m:
            type, expr = m.group(1, 2)
        else:
            type = "var"
            expr = expression
        if type == "str":
            return expr
        if type == "local":
            return self.locals[string.strip(expr)]
        if type == "global":
            return self.globals[string.strip(expr)]
        if type == "var":
            expr = string.strip(expr)
            if self.locals.has_key(expr):
                return self.locals[expr]
            else:
                return self.globals[expr]
        if type == "python":
            return eval(expr, self.globals, self.locals)
        print "Unrecognized expression:", `expression`
        return None

    def evaluateValue(self, expr):
        return self.evaluate(expr)

    def evaluateBoolean(self, expr):
        return self.evaluate(expr)

    def evaluateText(self, expr):
        return self.evaluate(expr)

    def evaluateStructure(self, expr):
        return self.evaluate(expr)

    def evaluateSequence(self, expr):
        return self.evaluate(expr)