#!/usr/bin/env python3
"""Classes and functions for testing the behavior of DPDAs."""

from frozendict import frozendict

import automata.base.exceptions as exceptions
import automata.pda.exceptions as pda_exceptions
import tests.test_pda as test_pda
from automata.pda.configuration import PDAConfiguration
from automata.pda.dpda import DPDA
from automata.pda.stack import PDAStack


class TestDPDA(test_pda.TestPDA):
    """A test class for testing deterministic finite automata."""

    def test_init_dpda(self):
        """Should copy DPDA if passed into DPDA constructor."""
        new_dpda = self.dpda.copy()
        self.assertIsNot(new_dpda, self.dpda)

    def test_init_dpda_missing_formal_params(self):
        """Should raise an error if formal DPDA parameters are missing."""
        with self.assertRaises(TypeError):
            DPDA(
                states={'q0', 'q1', 'q2'},
                input_symbols={'a', 'b'},
                initial_state='q0',
                final_states={'q0'}
            )

    def test_init_dpda_no_acceptance_mode(self):
        """Should create a new DPDA."""
        new_dpda = DPDA(
            states={'q0'},
            input_symbols={'a', 'b'},
            stack_symbols={'#'},
            transitions={'q0': {'a': {'#': ('q0', '')}}},
            initial_state='q0',
            initial_stack_symbol='#',
            final_states={'q0'}
        )
        self.assertEqual(new_dpda.acceptance_mode, 'both')

    def test_init_dpda_invalid_acceptance_mode(self):
        """Should raise an error if the NPDA has an invalid acceptance mode."""
        with self.assertRaises(pda_exceptions.InvalidAcceptanceModeError):
            DPDA(
                states={'q0'},
                input_symbols={'a', 'b'},
                stack_symbols={'#'},
                transitions={'q0': {'a': {'#': ('q0', '')}}},
                initial_state='q0',
                initial_stack_symbol='#',
                final_states={'q0'},
                acceptance_mode='foo'
            )

    def test_dpda_immutable_attr_set(self):
        with self.assertRaises(AttributeError):
            self.dpda.states = {}

    def test_dpda_immutable_attr_del(self):
        with self.assertRaises(AttributeError):
            del self.dpda.states

    def test_dpda_immutable_dict(self):
        """Should create a DPDA whose contents are fully immutable/hashable"""
        self.assertIsInstance(hash(frozendict(self.dpda.input_parameters)), int)

    def test_validate_invalid_input_symbol(self):
        """Should raise error if a transition has an invalid input symbol."""
        with self.assertRaises(exceptions.InvalidSymbolError):
            DPDA(
                states={'q0', 'q1', 'q2', 'q3'},
                input_symbols={'a', 'b'},
                stack_symbols={'0', '1'},
                transitions={
                    'q0': {
                        'a': {'0': ('q1', ('1', '0'))}
                    },
                    'q1': {
                        'a': {'1': ('q1', ('1', '1'))},
                        'b': {'1': ('q2', '')},
                        'c': {'1': 'q2'}
                    },
                    'q2': {
                        'b': {'1': ('q2', '')},
                        '': {'0': ('q3', ('0',))}
                    }
                },
                initial_state='q0',
                initial_stack_symbol='0',
                final_states={'q3'},
                acceptance_mode='final_state'
            )

    def test_validate_invalid_stack_symbol(self):
        """Should raise error if a transition has an invalid stack symbol."""
        with self.assertRaises(exceptions.InvalidSymbolError):
            DPDA(
                states={'q0', 'q1', 'q2', 'q3'},
                input_symbols={'a', 'b'},
                stack_symbols={'0', '1'},
                transitions={
                    'q0': {
                        'a': {'0': ('q1', ('1', '0'))}
                    },
                    'q1': {
                        'a': {'1': ('q1', ('1', '1')), '2': ('q1', ('1', '1'))},
                        'b': {'1': ('q2', '')}
                    },
                    'q2': {
                        'b': {'1': ('q2', '')},
                        '': {'0': ('q3', ('0',))}
                    }
                },
                initial_state='q0',
                initial_stack_symbol='0',
                final_states={'q3'},
                acceptance_mode='final_state'
            )

    def test_validate_nondeterminism(self):
        """Should raise error if DPDA exhibits nondeterminism."""
        with self.assertRaises(pda_exceptions.NondeterminismError):
            DPDA(
                states={'q0', 'q1', 'q2', 'q3'},
                input_symbols={'a', 'b'},
                stack_symbols={'0', '1'},
                transitions={
                    'q0': {
                        'a': {'0': ('q1', ('1', '0'))}
                    },
                    'q1': {
                        'a': {'1': ('q1', ('1', '1'))},
                        'b': {'1': ('q2', '')}
                    },
                    'q2': {
                        'b': {'0': ('q2', '0'), '1': ('q2', '')},
                        '': {'0': ('q3', ('0',))}
                    }
                },
                initial_state='q0',
                initial_stack_symbol='0',
                final_states={'q3'},
                acceptance_mode='final_state'
            )

    def test_validate_invalid_initial_state(self):
        """Should raise error if the initial state is invalid."""
        with self.assertRaises(exceptions.InvalidStateError):
            DPDA(
                states={'q0'},
                input_symbols={'a', 'b'},
                stack_symbols={'#'},
                transitions={'q0': {'a': {'#': ('q0', '')}}},
                initial_state='q1',
                initial_stack_symbol='#',
                final_states={'q0'}
            )

    def test_validate_invalid_initial_stack_symbol(self):
        """Should raise error if the initial stack symbol is invalid."""
        with self.assertRaises(exceptions.InvalidSymbolError):
            DPDA(
                states={'q0'},
                input_symbols={'a', 'b'},
                stack_symbols={'#'},
                transitions={'q0': {'a': {'#': ('q0', '')}}},
                initial_state='q0',
                initial_stack_symbol='2',
                final_states={'q0'}
            )

    def test_validate_invalid_final_state(self):
        """Should raise error if the final state is invalid."""
        with self.assertRaises(exceptions.InvalidStateError):
            DPDA(
                states={'q0'},
                input_symbols={'a', 'b'},
                stack_symbols={'#'},
                transitions={'q0': {'a': {'#': ('q0', '')}}},
                initial_state='q0',
                initial_stack_symbol='#',
                final_states={'q1'}
            )

    def test_validate_invalid_final_state_non_str(self):
        """Should raise InvalidStateError even for non-string final states."""
        with self.assertRaises(exceptions.InvalidStateError):
            DPDA(
                states={'q0'},
                input_symbols={'a', 'b'},
                stack_symbols={'#'},
                transitions={'q0': {'a': {'#': ('q0', '')}}},
                initial_state='q0',
                initial_stack_symbol='#',
                final_states={1}
            )

    def test_read_input_valid_accept_by_final_state(self):
        """Should return correct config if DPDA accepts by final state."""
        self.assertEqual(
            self.dpda.read_input('aabb'),
            PDAConfiguration('q3', '', PDAStack(['0']))
        )

    def test_read_input_invalid_accept_by_final_state(self):
        """Should not accept by final state if DPDA accepts by empty stack."""
        dpda = DPDA(
            states={'q0', 'q1', 'q2', 'q3'},
            input_symbols={'a', 'b'},
            stack_symbols={'0', '1'},
            transitions={
                'q0': {
                    'a': {'0': ('q1', ('1', '0'))}
                },
                'q1': {
                    'a': {'1': ('q1', ('1', '1'))},
                    'b': {'1': ('q2', '')}
                },
                'q2': {
                    'b': {'1': ('q2', '')},
                    '': {'0': ('q3', ('0',))}
                }
            },
            initial_state='q0',
            initial_stack_symbol='0',
            final_states={'q3'},
            acceptance_mode='empty_stack'
        )
        with self.assertRaises(exceptions.RejectionException):
            dpda.read_input('aabb')

    def test_read_input_valid_accept_by_empty_stack(self):
        """Should return correct config if DPDA accepts by empty stack."""
        dpda = DPDA(
            states={'q0', 'q1', 'q2', 'q3'},
            input_symbols={'a', 'b'},
            stack_symbols={'0', '1'},
            transitions={
                'q0': {
                    'a': {'0': ('q1', ('1', '0'))}
                },
                'q1': {
                    'a': {'1': ('q1', ('1', '1'))},
                    'b': {'1': ('q2', '')}
                },
                'q2': {
                    'b': {'1': ('q2', '')},
                    '': {'0': ('q2', '')}
                }
            },
            initial_state='q0',
            initial_stack_symbol='0',
            final_states={'q3'},
            acceptance_mode='empty_stack'
        )
        self.assertEqual(
            dpda.read_input('aabb'),
            PDAConfiguration('q2', '', PDAStack([]))
        )

    def test_read_input_invalid_accept_by_empty_stack(self):
        """Should not accept by empty stack if DPDA accepts by final state."""
        dpda = DPDA(
            states={'q0', 'q1', 'q2', 'q3'},
            input_symbols={'a', 'b'},
            stack_symbols={'0', '1'},
            transitions={
                'q0': {
                    'a': {'0': ('q1', ('1', '0'))}
                },
                'q1': {
                    'a': {'1': ('q1', ('1', '1'))},
                    'b': {'1': ('q2', '')}
                },
                'q2': {
                    'b': {'1': ('q2', '')},
                    '': {'0': ('q2', '')}
                }
            },
            initial_state='q0',
            initial_stack_symbol='0',
            final_states={'q3'},
            acceptance_mode='final_state'
        )
        with self.assertRaises(exceptions.RejectionException):
            dpda.read_input('aabb')

    def test_read_input_valid_consecutive_lambda_transitions(self):
        """Should follow consecutive lambda transitions when validating."""
        dpda = DPDA(
            states={'q0', 'q1', 'q2', 'q3', 'q4'},
            input_symbols={'a', 'b'},
            stack_symbols={'0', '1'},
            transitions={
                'q0': {
                    'a': {'0': ('q1', ('1', '0'))}
                },
                'q1': {
                    'a': {'1': ('q1', ('1', '1'))},
                    'b': {'1': ('q2', '')}
                },
                'q2': {
                    'b': {'1': ('q2', '')},
                    '': {'0': ('q3', ('0',))}
                },
                'q3': {
                    '': {'0': ('q4', ('0',))}
                }
            },
            initial_state='q0',
            initial_stack_symbol='0',
            final_states={'q4'},
            acceptance_mode='final_state'
        )
        self.assertEqual(
            dpda.read_input('aabb'),
            PDAConfiguration('q4', '', PDAStack(['0']))
        )

    def test_read_input_rejected_accept_by_final_state(self):
        """Should reject strings if DPDA accepts by final state."""
        with self.assertRaises(exceptions.RejectionException):
            self.dpda.read_input('aab')

    def test_read_input_rejected_accept_by_empty_stack(self):
        """Should reject strings if DPDA accepts by empty stack."""
        dpda = DPDA(
            states={'q0', 'q1', 'q2', 'q3'},
            input_symbols={'a', 'b'},
            stack_symbols={'0', '1'},
            transitions={
                'q0': {
                    'a': {'0': ('q1', ('1', '0'))}
                },
                'q1': {
                    'a': {'1': ('q1', ('1', '1'))},
                    'b': {'1': ('q2', '')}
                },
                'q2': {
                    'b': {'1': ('q2', '')},
                    '': {'0': ('q2', '')}
                }
            },
            initial_state='q0',
            initial_stack_symbol='0',
            final_states={'q3'},
            acceptance_mode='final_state'
        )
        with self.assertRaises(exceptions.RejectionException):
            dpda.read_input('aab')

    def test_read_input_rejected_undefined_transition(self):
        """Should reject strings which lead to an undefined transition."""
        with self.assertRaises(exceptions.RejectionException):
            self.dpda.read_input('01')

    def test_accepts_input_true(self):
        """Should return False if DPDA input is not accepted."""
        self.assertTrue(self.dpda.accepts_input('aabb'))

    def test_accepts_input_false(self):
        """Should return False if DPDA input is rejected."""
        self.assertFalse(self.dpda.accepts_input('aab'))

    def test_empty_dpda(self):
        """Should accept an empty input if the DPDA is empty."""
        dpda = DPDA(
            states={'q0'},
            input_symbols=set(),
            stack_symbols={'0'},
            transitions=dict(),
            initial_state='q0',
            initial_stack_symbol='0',
            final_states={'q0'},
            acceptance_mode='both'
        )
        self.assertTrue(dpda.accepts_input(''))
