import pytest


import networkx as nx
from networkx.testing import almost_equal

def validate_grid_path(r, c, s, t, p):
    assert isinstance(p, list)
    assert p[0] == s
    assert p[-1] == t
    s = ((s - 1) // c, (s - 1) % c)
    t = ((t - 1) // c, (t - 1) % c)
    assert len(p) == abs(t[0] - s[0]) + abs(t[1] - s[1]) + 1
    p = [((u - 1) // c, (u - 1) % c) for u in p]
    for u in p:
        assert 0 <= u[0] < r
        assert 0 <= u[1] < c
    for u, v in zip(p[:-1], p[1:]):
        assert (abs(v[0] - u[0]), abs(v[1] - u[1])) in [(0, 1), (1, 0)]


class TestGenericPath:

    @classmethod
    def setup_class(cls):
        from networkx import convert_node_labels_to_integers as cnlti
        cls.grid = cnlti(nx.grid_2d_graph(4, 4), first_label=1,
                          ordering="sorted")
        cls.cycle = nx.cycle_graph(7)
        cls.directed_cycle = nx.cycle_graph(7, create_using=nx.DiGraph())
        cls.neg_weights = nx.DiGraph()
        cls.neg_weights.add_edge(0, 1, weight=1)
        cls.neg_weights.add_edge(0, 2, weight=3)
        cls.neg_weights.add_edge(1, 3, weight=1)
        cls.neg_weights.add_edge(2, 3, weight=-2)

    def test_shortest_path(self):
        assert nx.shortest_path(self.cycle, 0, 3) == [0, 1, 2, 3]
        assert nx.shortest_path(self.cycle, 0, 4) == [0, 6, 5, 4]
        validate_grid_path(4, 4, 1, 12, nx.shortest_path(self.grid, 1, 12))
        assert nx.shortest_path(self.directed_cycle, 0, 3) == [0, 1, 2, 3]
        # now with weights
        assert (nx.shortest_path(self.cycle, 0, 3, weight='weight') ==
                     [0, 1, 2, 3])
        assert (nx.shortest_path(self.cycle, 0, 4, weight='weight') ==
                     [0, 6, 5, 4])
        validate_grid_path(4, 4, 1, 12, nx.shortest_path(self.grid, 1, 12,
                                                         weight='weight'))
        assert (nx.shortest_path(self.directed_cycle, 0, 3,
                                      weight='weight') ==
                     [0, 1, 2, 3])
        # weights and method specified
        assert (nx.shortest_path(self.directed_cycle, 0, 3,
                                      weight='weight', method='dijkstra') ==
                     [0, 1, 2, 3])
        assert (nx.shortest_path(self.directed_cycle, 0, 3,
                                      weight='weight', method='bellman-ford') ==
                     [0, 1, 2, 3])
        # when Dijkstra's will probably (depending on precise implementation)
        # incorrectly return [0, 1, 3] instead
        assert (nx.shortest_path(self.neg_weights, 0, 3, weight='weight',
                                      method='bellman-ford') ==
                     [0, 2, 3])
        # confirm bad method rejection
        pytest.raises(ValueError, nx.shortest_path, self.cycle, method='SPAM')
        # confirm absent source rejection
        pytest.raises(nx.NodeNotFound, nx.shortest_path, self.cycle, 8)

    def test_shortest_path_target(self):
        answer = {0: [0, 1], 1: [1], 2: [2, 1]}
        sp = nx.shortest_path(nx.path_graph(3), target=1)
        assert sp == answer
        # with weights
        sp = nx.shortest_path(nx.path_graph(3), target=1, weight='weight')
        assert sp == answer
        # weights and method specified
        sp = nx.shortest_path(nx.path_graph(3), target=1, weight='weight',
                              method='dijkstra')
        assert sp == answer
        sp = nx.shortest_path(nx.path_graph(3), target=1, weight='weight',
                              method='bellman-ford')
        assert sp == answer

    def test_shortest_path_length(self):
        assert nx.shortest_path_length(self.cycle, 0, 3) == 3
        assert nx.shortest_path_length(self.grid, 1, 12) == 5
        assert nx.shortest_path_length(self.directed_cycle, 0, 4) == 4
        # now with weights
        assert (nx.shortest_path_length(self.cycle, 0, 3,
                                             weight='weight') ==
                     3)
        assert (nx.shortest_path_length(self.grid, 1, 12,
                                             weight='weight') ==
                     5)
        assert (nx.shortest_path_length(self.directed_cycle, 0, 4,
                                             weight='weight') ==
                     4)
        # weights and method specified
        assert (nx.shortest_path_length(self.cycle, 0, 3, weight='weight',
                                             method='dijkstra') ==
                     3)
        assert (nx.shortest_path_length(self.cycle, 0, 3, weight='weight',
                                             method='bellman-ford') ==
                     3)
        # confirm bad method rejection
        pytest.raises(ValueError,
                      nx.shortest_path_length,
                      self.cycle,
                      method='SPAM')
        # confirm absent source rejection
        pytest.raises(nx.NodeNotFound, nx.shortest_path_length, self.cycle, 8)

    def test_shortest_path_length_target(self):
        answer = {0: 1, 1: 0, 2: 1}
        sp = dict(nx.shortest_path_length(nx.path_graph(3), target=1))
        assert sp == answer
        # with weights
        sp = nx.shortest_path_length(nx.path_graph(3), target=1,
                                     weight='weight')
        assert sp == answer
        # weights and method specified
        sp = nx.shortest_path_length(nx.path_graph(3), target=1,
                                     weight='weight', method='dijkstra')
        assert sp == answer
        sp = nx.shortest_path_length(nx.path_graph(3), target=1,
                                     weight='weight', method='bellman-ford')
        assert sp == answer

    def test_single_source_shortest_path(self):
        p = nx.shortest_path(self.cycle, 0)
        assert p[3] == [0, 1, 2, 3]
        assert p == nx.single_source_shortest_path(self.cycle, 0)
        p = nx.shortest_path(self.grid, 1)
        validate_grid_path(4, 4, 1, 12, p[12])
        # now with weights
        p = nx.shortest_path(self.cycle, 0, weight='weight')
        assert p[3] == [0, 1, 2, 3]
        assert p == nx.single_source_dijkstra_path(self.cycle, 0)
        p = nx.shortest_path(self.grid, 1, weight='weight')
        validate_grid_path(4, 4, 1, 12, p[12])
        # weights and method specified
        p = nx.shortest_path(self.cycle, 0, method='dijkstra', weight='weight')
        assert p[3] == [0, 1, 2, 3]
        assert p == nx.single_source_shortest_path(self.cycle, 0)
        p = nx.shortest_path(self.cycle, 0, method='bellman-ford',
                             weight='weight')
        assert p[3] == [0, 1, 2, 3]
        assert p == nx.single_source_shortest_path(self.cycle, 0)

    def test_single_source_shortest_path_length(self):
        ans = dict(nx.shortest_path_length(self.cycle, 0))
        assert ans == {0: 0, 1: 1, 2: 2, 3: 3, 4: 3, 5: 2, 6: 1}
        assert (ans ==
                     dict(nx.single_source_shortest_path_length(self.cycle,
                                                                0)))
        ans = dict(nx.shortest_path_length(self.grid, 1))