import pytest

import networkx as nx
from networkx.utils import nodes_equal


class TestCore:
    @classmethod
    def setup_class(cls):
        # G is the example graph in Figure 1 from Batagelj and
        # Zaversnik's paper titled An O(m) Algorithm for Cores
        # Decomposition of Networks, 2003,
        # http://arXiv.org/abs/cs/0310049.  With nodes labeled as
        # shown, the 3-core is given by nodes 1-8, the 2-core by nodes
        # 9-16, the 1-core by nodes 17-20 and node 21 is in the
        # 0-core.
        t1 = nx.convert_node_labels_to_integers(nx.tetrahedral_graph(), 1)
        t2 = nx.convert_node_labels_to_integers(t1, 5)
        G = nx.union(t1, t2)
        G.add_edges_from(
            [
                (3, 7),
                (2, 11),
                (11, 5),
                (11, 12),
                (5, 12),
                (12, 19),
                (12, 18),
                (3, 9),
                (7, 9),
                (7, 10),
                (9, 10),
                (9, 20),
                (17, 13),
                (13, 14),
                (14, 15),
                (15, 16),
                (16, 13),
            ]
        )
        G.add_node(21)
        cls.G = G

        # Create the graph H resulting from the degree sequence
        # [0, 1, 2, 2, 2, 2, 3] when using the Havel-Hakimi algorithm.

        degseq = [0, 1, 2, 2, 2, 2, 3]
        H = nx.havel_hakimi_graph(degseq)
        mapping = {6: 0, 0: 1, 4: 3, 5: 6, 3: 4, 1: 2, 2: 5}
        cls.H = nx.relabel_nodes(H, mapping)

    def test_trivial(self):
        """Empty graph"""
        G = nx.Graph()
        assert nx.core_number(G) == {}

    def test_core_number(self):
        core = nx.core_number(self.G)
        nodes_by_core = [sorted(n for n in core if core[n] == val) for val in range(4)]
        assert nodes_equal(nodes_by_core[0], [21])
        assert nodes_equal(nodes_by_core[1], [17, 18, 19, 20])
        assert nodes_equal(nodes_by_core[2], [9, 10, 11, 12, 13, 14, 15, 16])
        assert nodes_equal(nodes_by_core[3], [1, 2, 3, 4, 5, 6, 7, 8])

    def test_core_number2(self):
        core = nx.core_number(self.H)
        nodes_by_core = [sorted(n for n in core if core[n] == val) for val in range(3)]
        assert nodes_equal(nodes_by_core[0], [0])
        assert nodes_equal(nodes_by_core[1], [1, 3])
        assert nodes_equal(nodes_by_core[2], [2, 4, 5, 6])

    def test_core_number_self_loop(self):
        G = nx.cycle_graph(3)
        G.add_edge(0, 0)
        with pytest.raises(nx.NetworkXError, match="Input graph has self loops"):
            nx.core_number(G)

    def test_directed_core_number(self):
        """core number had a bug for directed graphs found in issue #1959"""
        # small example where too timid edge removal can make cn[2] = 3
        G = nx.DiGraph()
        edges = [(1, 2), (2, 1), (2, 3), (2, 4), (3, 4), (4, 3)]
        G.add_edges_from(edges)
        assert nx.core_number(G) == {1: 2, 2: 2, 3: 2, 4: 2}
        # small example where too aggressive edge removal can make cn[2] = 2
        more_edges = [(1, 5), (3, 5), (4, 5), (3, 6), (4, 6), (5, 6)]
        G.add_edges_from(more_edges)
        assert nx.core_number(G) == {1: 3, 2: 3, 3: 3, 4: 3, 5: 3, 6: 3}

    def test_main_core(self):
        main_core_subgraph = nx.k_core(self.H)
        assert sorted(main_core_subgraph.nodes()) == [2, 4, 5, 6]

    def test_k_core(self):
        # k=0
        k_core_subgraph = nx.k_core(self.H, k=0)
        assert sorted(k_core_subgraph.nodes()) == sorted(self.H.nodes())
        # k=1
        k_core_subgraph = nx.k_core(self.H, k=1)
        assert sorted(k_core_subgraph.nodes()) == [1, 2, 3, 4, 5, 6]
        # k = 2
        k_core_subgraph = nx.k_core(self.H, k=2)
        assert sorted(k_core_subgraph.nodes()) == [2, 4, 5, 6]

    def test_main_crust(self):
        main_crust_subgraph = nx.k_crust(self.H)
        assert sorted(main_crust_subgraph.nodes()) == [0, 1, 3]

    def test_k_crust(self):
        # k = 0
        k_crust_subgraph = nx.k_crust(self.H, k=2)
        assert sorted(k_crust_subgraph.nodes()) == sorted(self.H.nodes())
        # k=1
        k_crust_subgraph = nx.k_crust(self.H, k=1)
        assert sorted(k_crust_subgraph.nodes()) == [0, 1, 3]
        # k=2
        k_crust_subgraph = nx.k_crust(self.H, k=0)
        assert sorted(k_crust_subgraph.nodes()) == [0]

    def test_main_shell(self):
        main_shell_subgraph = nx.k_shell(self.H)
        assert sorted(main_shell_subgraph.nodes()) == [2, 4, 5, 6]

    def test_k_shell(self):
        # k=0
        k_shell_subgraph = nx.k_shell(self.H, k=2)
        assert sorted(k_shell_subgraph.nodes()) == [2, 4, 5, 6]
        # k=1
        k_shell_subgraph = nx.k_shell(self.H, k=1)
        assert sorted(k_shell_subgraph.nodes()) == [1, 3]
        # k=2
        k_shell_subgraph = nx.k_shell(self.H, k=0)
        assert sorted(k_shell_subgraph.nodes()) == [0]

    def test_k_corona(self):
        # k=0
        k_corona_subgraph = nx.k_corona(self.H, k=2)
        assert sorted(k_corona_subgraph.nodes()) == [2, 4, 5, 6]
        # k=1
        k_corona_subgraph = nx.k_corona(self.H, k=1)
        assert sorted(k_corona_subgraph.nodes()) == [1]
        # k=2
        k_corona_subgraph = nx.k_corona(self.H, k=0)
        assert sorted(k_corona_subgraph.nodes()) == [0]

    def test_k_truss(self):
        # k=-1
        k_truss_subgraph = nx.k_truss(self.G, -1)
        assert sorted(k_truss_subgraph.nodes()) == list(range(1, 21))
        # k=0
        k_truss_subgraph = nx.k_truss(self.G, 0)
        assert sorted(k_truss_subgraph.nodes()) == list(range(1, 21))
        # k=1
        k_truss_subgraph = nx.k_truss(self.G, 1)
        assert sorted(k_truss_subgraph.nodes()) == list(range(1, 21))
        # k=2
        k_truss_subgraph = nx.k_truss(self.G, 2)
        assert sorted(k_truss_subgraph.nodes()) == list(range(1, 21))
        # k=3
        k_truss_subgraph = nx.k_truss(self.G, 3)
        assert sorted(k_truss_subgraph.nodes()) == list(range(1, 13))

        k_truss_subgraph = nx.k_truss(self.G, 4)
        assert sorted(k_truss_subgraph.nodes()) == list(range(1, 9))

        k_truss_subgraph = nx.k_truss(self.G, 5)
        assert sorted(k_truss_subgraph.nodes()) == []

    def test_onion_layers(self):
        layers = nx.onion_layers(self.G)
        nodes_by_layer = [
            sorted(n for n in layers if layers[n] == val) for val in range(1, 7)
        ]
        assert nodes_equal(nodes_by_layer[0], [21])
        assert nodes_equal(nodes_by_layer[1], [17, 18, 19, 20])
        assert nodes_equal(nodes_by_layer[2], [10, 12, 13, 14, 15, 16])
        assert nodes_equal(nodes_by_layer[3], [9, 11])
        assert nodes_equal(nodes_by_layer[4], [1, 2, 4, 5, 6, 8])
        assert nodes_equal(nodes_by_layer[5], [3, 7])

    def test_onion_self_loop(self):
        G = nx.cycle_graph(3)
        G.add_edge(0, 0)
        with pytest.raises(nx.NetworkXError, match="Input graph contains self loops"):
            nx.onion_layers(G)