from mal_types import MalType, MalSym, MalList, throw_str

# Environment
class Env():
    def __init__(self, outer=None, binds=None, exprs=None):
        self.data = {}
        self.outer = outer or None

        if binds:
            assert isinstance(binds, MalList) and isinstance(exprs, MalList)
            for i in range(len(binds)):
                bind = binds[i]
                if not isinstance(bind, MalSym):
                    throw_str("env bind value is not a symbol")
                if bind.value == u"&":
                    bind = binds[i+1]
                    if not isinstance(bind, MalSym):
                        throw_str("env bind value is not a symbol")
                    self.data[bind.value] = exprs.slice(i)
                    break
                else:
                    self.data[bind.value] = exprs[i]

    def set(self, key, value):
        assert isinstance(key, MalSym)
        assert isinstance(value, MalType)
        self.data[key.value] = value
        return value

    def get(self, key):
        assert isinstance(key, unicode)
        env = self
        while True:
            value = env.data.get(key, None)
            if value is not None: return value
            env = env.outer
            if env is None: return None