// Copyright ©2021 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gen

import (
	"bytes"
	"fmt"
	"testing"

	"gonum.org/v1/gonum/graph"
	"gonum.org/v1/gonum/graph/encoding/dot"
	"gonum.org/v1/gonum/graph/simple"
)

type nodeIDGraphBuilder interface {
	graph.Graph
	NodeIDGraphBuilder
}

func undirected() nodeIDGraphBuilder { return simple.NewUndirectedGraph() }
func directed() nodeIDGraphBuilder   { return simple.NewDirectedGraph() }

type empty struct{}

func (r empty) Len() int       { return 0 }
func (r empty) ID(i int) int64 { panic("called ID on empty IDer") }

func panics(fn func()) (panicked bool, msg string) {
	defer func() {
		r := recover()
		if r != nil {
			panicked = true
			msg = fmt.Sprint(r)
		}
	}()
	fn()
	return
}

func TestComplete(t *testing.T) {
	tests := []struct {
		name   string
		ids    IDer
		dst    func() nodeIDGraphBuilder
		want   string
		panics string
	}{
		{
			name: "empty",
			ids:  empty{},
			dst:  undirected,
			want: `strict graph empty {
}`,
		},
		{
			name: "single",
			ids:  IDRange{First: 1, Last: 1},
			dst:  undirected,
			want: `strict graph single {
 // Node definitions.
 1;
}`,
		},
		{
			name: "pair_undirected",
			ids:  IDRange{First: 1, Last: 2},
			dst:  undirected,
			want: `strict graph pair_undirected {
 // Node definitions.
 1;
 2;

 // Edge definitions.
 1 -- 2;
}`,
		},
		{
			name: "pair_directed",
			ids:  IDRange{First: 1, Last: 2},
			dst:  directed,
			want: `strict digraph pair_directed {
 // Node definitions.
 1;
 2;

 // Edge definitions.
 1 -> 2;
}`,
		},
		{
			name: "quad_undirected",
			ids:  IDRange{First: 1, Last: 4},
			dst:  undirected,
			want: `strict graph quad_undirected {
 // Node definitions.
 1;
 2;
 3;
 4;

 // Edge definitions.
 1 -- 2;
 1 -- 3;
 1 -- 4;
 2 -- 3;
 2 -- 4;
 3 -- 4;
}`,
		},
		{
			name: "quad_directed",
			ids:  IDRange{First: 1, Last: 4},
			dst:  directed,
			want: `strict digraph quad_directed {
 // Node definitions.
 1;
 2;
 3;
 4;

 // Edge definitions.
 1 -> 2;
 1 -> 3;
 1 -> 4;
 2 -> 3;
 2 -> 4;
 3 -> 4;
}`,
		},
		{
			name:   "collision",
			ids:    IDSet{1, 2, 3, 2},
			dst:    undirected,
			panics: "gen: node ID collision i=1 j=3: id=2",
		},
	}

	for _, test := range tests {
		dst := test.dst()
		panicked, msg := panics(func() { Complete(dst, test.ids) })
		if msg != test.panics {
			t.Errorf("unexpected panic message for %q: got:%q want:%q", test.name, msg, test.panics)
		}
		if panicked {
			continue
		}
		got, err := dot.Marshal(dst, test.name, "", " ")
		if err != nil {
			t.Errorf("unexpected marshaling graph error: %v", err)
		}
		if !bytes.Equal(got, []byte(test.want)) {
			t.Errorf("unexpected result for test %s:\ngot:\n%s\nwant:\n%s", test.name, got, test.want)
		}
	}
}

func TestCycle(t *testing.T) {
	tests := []struct {
		name   string
		ids    IDer
		dst    func() nodeIDGraphBuilder
		want   string
		panics string
	}{
		{
			name: "empty",
			ids:  empty{},
			dst:  undirected,
			want: `strict graph empty {
}`,
		},
		{
			name: "single",
			ids:  IDRange{First: 1, Last: 1},
			dst:  undirected,
			want: `strict graph single {
 // Node definitions.
 1;
}`,
		},
		{
			name: "pair_undirected",
			ids:  IDRange{First: 1, Last: 2},
			dst:  undirected,
			want: `strict graph pair_undirected {
 // Node definitions.
 1;
 2;

 // Edge definitions.
 1 -- 2;
}`,
		},
		{
			name: "pair_directed",
			ids:  IDRange{First: 1, Last: 2},
			dst:  directed,
			want: `strict digraph pair_directed {
 // Node definitions.
 1;
 2;

 // Edge definitions.
 1 -> 2;
 2 -> 1;
}`,
		},
		{
			name: "quad_undirected",
			ids:  IDRange{First: 1, Last: 4},
			dst:  undirected,
			want: `strict graph quad_undirected {
 // Node definitions.
 1;
 2;
 3;
 4;

 // Edge definitions.
 1 -- 2;
 1 -- 4;
 2 -- 3;
 3 -- 4;
}`,
		},
		{
			name: "quad_directed",
			ids:  IDRange{First: 1, Last: 4},
			dst:  directed,
			want: `strict digraph quad_directed {
 // Node definitions.
 1;
 2;
 3;
 4;

 // Edge definitions.
 1 -> 2;
 2 -> 3;
 3 -> 4;
 4 -> 1;
}`,
		},
		{
			name:   "collision",
			ids:    IDSet{1, 2, 3, 2},
			dst:    undirected,
			panics: "gen: node ID collision i=1 j=3: id=2",
		},
	}

	for _, test := range tests {
		dst := test.dst()
		panicked, msg := panics(func() { Cycle(dst, test.ids) })
		if msg != test.panics {
			t.Errorf("unexpected panic message for %q: got:%q want:%q", test.name, msg, test.panics)
		}
		if panicked {
			continue
		}
		got, err := dot.Marshal(dst, test.name, "", " ")
		if err != nil {
			t.Errorf("unexpected error marshaling graph: %v", err)
		}
		if !bytes.Equal(got, []byte(test.want)) {
			t.Errorf("unexpected result for test %s:\ngot:\n%s\nwant:\n%s", test.name, got, test.want)
		}
	}
}

func TestPath(t *testing.T) {
	tests := []struct {
		name   string
		ids    IDer
		dst    func() nodeIDGraphBuilder
		want   string
		panics string
	}{
		{
			name: "empty",
			ids:  empty{},
			dst:  undirected,
			want: `strict graph empty {
}`,
		},
		{
			name: "single",
			ids:  IDRange{First: 1, Last: 1},
			dst:  undirected,
			want: `strict graph single {
 // Node definitions.
 1;
}`,
		},
		{
			name: "pair_undirected",
			ids:  IDRange{First: 1, Last: 2},
			dst:  undirected,
			want: `strict graph pair_undirected {
 // Node definitions.
 1;
 2;

 // Edge definitions.
 1 -- 2;
}`,
		},
		{
			name: "pair_directed",
			ids:  IDRange{First: 1, Last: 2},
			dst:  directed,
			want: `strict digraph pair_directed {
 // Node definitions.
 1;
 2;

 // Edge definitions.
 1 -> 2;
}`,
		},
		{
			name: "quad_undirected",
			ids:  IDRange{First: 1, Last: 4},
			dst:  undirected,
			want: `strict graph quad_undirected {
 // Node definitions.
 1;
 2;
 3;
 4;

 // Edge definitions.
 1 -- 2;
 2 -- 3;
 3 -- 4;
}`,
		},
		{
			name: "quad_directed",
			ids:  IDRange{First: 1, Last: 4},
			dst:  directed,
			want: `strict digraph quad_directed {
 // Node definitions.
 1;
 2;
 3;
 4;

 // Edge definitions.
 1 -> 2;
 2 -> 3;
 3 -> 4;
}`,
		},
		{
			name:   "collision",
			ids:    IDSet{1, 2, 3, 2},
			dst:    undirected,
			panics: "gen: node ID collision i=1 j=3: id=2",
		},
	}

	for _, test := range tests {
		dst := test.dst()
		panicked, msg := panics(func() { Path(dst, test.ids) })
		if msg != test.panics {
			t.Errorf("unexpected panic message for %q: got:%q want:%q", test.name, msg, test.panics)
		}
		if panicked {
			continue
		}
		got, err := dot.Marshal(dst, test.name, "", " ")
		if err != nil {
			t.Errorf("unexpected error marshaling graph: %v", err)
		}
		if !bytes.Equal(got, []byte(test.want)) {
			t.Errorf("unexpected result for test %s:\ngot:\n%s\nwant:\n%s", test.name, got, test.want)
		}
	}
}

func TestStar(t *testing.T) {
	tests := []struct {
		name   string
		center int64
		leaves IDer
		dst    func() nodeIDGraphBuilder
		want   string
		panics string
	}{
		{
			name:   "empty_leaves",
			center: 0,
			leaves: empty{},
			dst:    undirected,
			want: `strict graph empty_leaves {
 // Node definitions.
 0;
}`,
		},
		{
			name:   "single",
			center: 0,
			leaves: IDRange{First: 1, Last: 1},
			dst:    undirected,
			want: `strict graph single {
 // Node definitions.
 0;
 1;

 // Edge definitions.
 0 -- 1;
}`,
		},
		{
			name:   "pair_undirected",
			center: 0,
			leaves: IDRange{First: 1, Last: 2},
			dst:    undirected,
			want: `strict graph pair_undirected {
 // Node definitions.
 0;
 1;
 2;

 // Edge definitions.
 0 -- 1;
 0 -- 2;
}`,
		},
		{
			name:   "pair_directed",
			center: 0,
			leaves: IDRange{First: 1, Last: 2},
			dst:    directed,
			want: `strict digraph pair_directed {
 // Node definitions.
 0;
 1;
 2;

 // Edge definitions.
 0 -> 1;
 0 -> 2;
}`,
		},
		{
			name:   "quad_undirected",
			center: 0,
			leaves: IDRange{First: 1, Last: 4},
			dst:    undirected,
			want: `strict graph quad_undirected {
 // Node definitions.
 0;
 1;
 2;
 3;
 4;

 // Edge definitions.
 0 -- 1;
 0 -- 2;
 0 -- 3;
 0 -- 4;
}`,
		},
		{
			name:   "quad_directed",
			center: 0,
			leaves: IDRange{First: 1, Last: 4},
			dst:    directed,
			want: `strict digraph quad_directed {
 // Node definitions.
 0;
 1;
 2;
 3;
 4;

 // Edge definitions.
 0 -> 1;
 0 -> 2;
 0 -> 3;
 0 -> 4;
}`,
		},
		{
			name:   "center collision",
			center: 1,
			leaves: IDRange{First: 1, Last: 4},
			dst:    undirected,
			panics: "gen: node ID collision i=0 with extra: id=1",
		},
		{
			name:   "leaf collision",
			center: 0,
			leaves: IDSet{1, 2, 3, 2},
			dst:    undirected,
			panics: "gen: node ID collision i=1 j=3: id=2",
		},
	}

	for _, test := range tests {
		dst := test.dst()
		panicked, msg := panics(func() { Star(dst, test.center, test.leaves) })
		if msg != test.panics {
			t.Errorf("unexpected panic message for %q: got:%q want:%q", test.name, msg, test.panics)
		}
		if panicked {
			continue
		}
		got, err := dot.Marshal(dst, test.name, "", " ")
		if err != nil {
			t.Errorf("unexpected error marshaling graph: %v", err)
		}
		if !bytes.Equal(got, []byte(test.want)) {
			t.Errorf("unexpected result for test %s:\ngot:\n%s\nwant:\n%s", test.name, got, test.want)
		}
	}
}

func TestWheel(t *testing.T) {
	tests := []struct {
		name   string
		center int64
		cycle  IDer
		dst    func() nodeIDGraphBuilder
		want   string
		panics string
	}{
		{
			name:   "empty_cycle",
			center: 0,
			cycle:  empty{},
			dst:    undirected,
			want: `strict graph empty_cycle {
 // Node definitions.
 0;
}`,
		},
		{
			name:  "single",
			cycle: IDRange{First: 1, Last: 1},
			dst:   undirected,
			want: `strict graph single {
 // Node definitions.
 0;
 1;

 // Edge definitions.
 0 -- 1;
}`,
		},
		{
			name:   "pair_undirected",
			center: 0,
			cycle:  IDRange{First: 1, Last: 2},
			dst:    undirected,
			want: `strict graph pair_undirected {
 // Node definitions.
 0;
 1;
 2;

 // Edge definitions.
 0 -- 1;
 0 -- 2;
 1 -- 2;
}`,
		},
		{
			name:   "pair_directed",
			center: 0,
			cycle:  IDRange{First: 1, Last: 2},
			dst:    directed,
			want: `strict digraph pair_directed {
 // Node definitions.
 0;
 1;
 2;

 // Edge definitions.
 0 -> 1;
 0 -> 2;
 1 -> 2;
 2 -> 1;
}`,
		},
		{
			name:   "quad_undirected",
			center: 0,
			cycle:  IDRange{First: 1, Last: 4},
			dst:    undirected,
			want: `strict graph quad_undirected {
 // Node definitions.
 0;
 1;
 2;
 3;
 4;

 // Edge definitions.
 0 -- 1;
 0 -- 2;
 0 -- 3;
 0 -- 4;
 1 -- 2;
 1 -- 4;
 2 -- 3;
 3 -- 4;
}`,
		},
		{
			name:   "quad_directed",
			center: 0,
			cycle:  IDRange{First: 1, Last: 4},
			dst:    directed,
			want: `strict digraph quad_directed {
 // Node definitions.
 0;
 1;
 2;
 3;
 4;

 // Edge definitions.
 0 -> 1;
 0 -> 2;
 0 -> 3;
 0 -> 4;
 1 -> 2;
 2 -> 3;
 3 -> 4;
 4 -> 1;
}`,
		},
		{
			name:   "center collision",
			center: 1,
			cycle:  IDRange{First: 1, Last: 4},
			dst:    undirected,
			panics: "gen: node ID collision i=0 with extra: id=1",
		},
		{
			name:   "cycle collision",
			center: 0,
			cycle:  IDSet{1, 2, 3, 2},
			dst:    undirected,
			panics: "gen: node ID collision i=1 j=3: id=2",
		},
	}

	for _, test := range tests {
		dst := test.dst()
		panicked, msg := panics(func() { Wheel(dst, test.center, test.cycle) })
		if msg != test.panics {
			t.Errorf("unexpected panic message for %q: got:%q want:%q", test.name, msg, test.panics)
		}
		if panicked {
			continue
		}
		got, err := dot.Marshal(dst, test.name, "", " ")
		if err != nil {
			t.Errorf("unexpected error marshaling graph: %v", err)
		}
		if !bytes.Equal(got, []byte(test.want)) {
			t.Errorf("unexpected result for test %s:\ngot:\n%s\nwant:\n%s", test.name, got, test.want)
		}
	}
}

func TestCheck(t *testing.T) {
	tests := []struct {
		ids   IDer
		extra []int64
		want  string
	}{
		{
			ids: IDSet{1, 2, 3, 4}, extra: []int64{1},
			want: "gen: node ID collision i=0 with extra: id=1",
		},
		{
			ids: IDSet{1, 2, 3, 4}, extra: []int64{5, 2},
			want: "gen: node ID collision i=1 with extra j=1: id=2",
		},
		{
			ids: IDSet{}, extra: []int64{1, 2, 1},
			want: "gen: extra node ID collision i=0 j=2: id=1",
		},
	}

	for _, test := range tests {
		msg := fmt.Sprint(check(test.ids, test.extra...))
		if msg != test.want {
			t.Errorf("unexpected check panic for ids=%#v extra=%v: got:%q want:%q",
				test.ids, test.extra, msg, test.want)
		}
	}
}

func TestTree(t *testing.T) {
	tests := []struct {
		name   string
		dst    func() nodeIDGraphBuilder
		nodes  IDer
		fanout int
		want   string
		panics string
	}{
		{
			name:   "empty_tree",
			dst:    undirected,
			nodes:  empty{},
			fanout: 2,
			want: `strict graph empty_tree {
}`,
		},
		{
			name:   "singleton_tree",
			dst:    undirected,
			nodes:  IDSet{0},
			fanout: 0,
			want: `strict graph singleton_tree {
 // Node definitions.
 0;
}`,
		},
		{
			name:   "full_binary_tree_undirected",
			dst:    undirected,
			nodes:  IDRange{First: 0, Last: 14},
			fanout: 2,
			want: `strict graph full_binary_tree_undirected {
 // Node definitions.
 0;
 1;
 2;
 3;
 4;
 5;
 6;
 7;
 8;
 9;
 10;
 11;
 12;
 13;
 14;

 // Edge definitions.
 0 -- 1;
 0 -- 2;
 1 -- 3;
 1 -- 4;
 2 -- 5;
 2 -- 6;
 3 -- 7;
 3 -- 8;
 4 -- 9;
 4 -- 10;
 5 -- 11;
 5 -- 12;
 6 -- 13;
 6 -- 14;
}`,
		},
		{
			name:   "partial_ternary_tree_undirected",
			dst:    undirected,
			nodes:  IDRange{First: 0, Last: 17},
			fanout: 3,
			want: `strict graph partial_ternary_tree_undirected {
 // Node definitions.
 0;
 1;
 2;
 3;
 4;
 5;
 6;
 7;
 8;
 9;
 10;
 11;
 12;
 13;
 14;
 15;
 16;
 17;

 // Edge definitions.
 0 -- 1;
 0 -- 2;
 0 -- 3;
 1 -- 4;
 1 -- 5;
 1 -- 6;
 2 -- 7;
 2 -- 8;
 2 -- 9;
 3 -- 10;
 3 -- 11;
 3 -- 12;
 4 -- 13;
 4 -- 14;
 4 -- 15;
 5 -- 16;
 5 -- 17;
}`,
		},
		{
			name:   "linear_graph_undirected",
			dst:    undirected,
			nodes:  IDRange{First: 0, Last: 4},
			fanout: 1,
			want: `strict graph linear_graph_undirected {
 // Node definitions.
 0;
 1;
 2;
 3;
 4;

 // Edge definitions.
 0 -- 1;
 1 -- 2;
 2 -- 3;
 3 -- 4;
}`,
		},
		{
			name:   "full_ternary_tree_directed",
			dst:    directed,
			nodes:  IDRange{First: 0, Last: 12},
			fanout: 3,
			want: `strict digraph full_ternary_tree_directed {
 // Node definitions.
 0;
 1;
 2;
 3;
 4;
 5;
 6;
 7;
 8;
 9;
 10;
 11;
 12;

 // Edge definitions.
 0 -> 1;
 0 -> 2;
 0 -> 3;
 1 -> 4;
 1 -> 5;
 1 -> 6;
 2 -> 7;
 2 -> 8;
 2 -> 9;
 3 -> 10;
 3 -> 11;
 3 -> 12;
}`,
		},
		{
			name:   "bad_fanout",
			dst:    undirected,
			nodes:  IDSet{0, 1, 2, 3},
			fanout: -1,
			panics: "gen: invalid fan-out",
		},
		{
			name:   "collision",
			dst:    undirected,
			nodes:  IDSet{0, 1, 2, 3, 2},
			fanout: 2,
			panics: "gen: node ID collision i=2 j=4: id=2",
		},
	}
	for _, test := range tests {
		dst := test.dst()
		panicked, msg := panics(func() { Tree(dst, test.fanout, test.nodes) })
		if msg != test.panics {
			t.Errorf("unexpected panic message for %q: got:%q want:%q", test.name, msg, test.panics)
		}
		if panicked {
			continue
		}
		got, err := dot.Marshal(dst, test.name, "", " ")
		if err != nil {
			t.Errorf("unexpected error marshaling graph: %v", err)
		}
		if !bytes.Equal(got, []byte(test.want)) {
			t.Errorf("unexpected result for test %s:\ngot:\n%s\nwant:\n%s", test.name, got, test.want)
		}
	}
}