package engine

import (
	"testing"

	"drjosh.dev/gurgle/geom"
	"github.com/google/go-cmp/cmp"
	"github.com/hajimehoshi/ebiten/v2"
)

type fakeDrawBoxer string

func (fakeDrawBoxer) Draw(*ebiten.Image, *ebiten.DrawImageOptions) {}
func (fakeDrawBoxer) BoundingBox() geom.Box {
	return geom.Box{}
}

func TestDAGAddRemoveEdge(t *testing.T) {
	d := make(dag)
	var u, v fakeDrawBoxer = "u", "v"
	d.addEdge(u, v)
	want := dag{
		u: edges{
			in:  drawerSet{},
			out: drawerSet{v: {}},
		},
		v: edges{
			in:  drawerSet{u: {}},
			out: drawerSet{},
		},
	}
	if diff := cmp.Diff(d, want, cmp.AllowUnexported(edges{})); diff != "" {
		t.Errorf("diff after adding edge (u->v):\n%s", diff)
	}
	d.removeEdge(u, v)
	want = dag{
		u: edges{
			in:  drawerSet{},
			out: drawerSet{},
		},
		v: edges{
			in:  drawerSet{},
			out: drawerSet{},
		},
	}
	if diff := cmp.Diff(d, want, cmp.AllowUnexported(edges{})); diff != "" {
		t.Errorf("diff after removing edge (u->v):\n%s", diff)
	}
}

func TestDAGAddVertex(t *testing.T) {
	d := make(dag)
	u := fakeDrawBoxer("u")
	d.addVertex(u)
	want := dag{
		u: edges{
			in:  drawerSet{},
			out: drawerSet{},
		},
	}
	if diff := cmp.Diff(d, want, cmp.AllowUnexported(edges{})); diff != "" {
		t.Errorf("diff after adding vertex u:\n%s", diff)
	}
	v := fakeDrawBoxer("v")
	d.addVertex(v)
	want = dag{
		u: edges{
			in:  drawerSet{},
			out: drawerSet{},
		},
		v: edges{
			in:  drawerSet{},
			out: drawerSet{},
		},
	}
	if diff := cmp.Diff(d, want, cmp.AllowUnexported(edges{})); diff != "" {
		t.Errorf("diff after adding vertex v:\n%s", diff)
	}
	d.addVertex(u)
	if diff := cmp.Diff(d, want, cmp.AllowUnexported(edges{})); diff != "" {
		t.Errorf("diff after adding vertex u a second time:\n%s", diff)
	}
}

func TestDAGRemoveVertex(t *testing.T) {
	u := fakeDrawBoxer("u")
	v := fakeDrawBoxer("v")
	w := fakeDrawBoxer("w")
	d := dag{
		u: edges{
			in:  drawerSet{},
			out: drawerSet{v: {}},
		},
		v: edges{
			in:  drawerSet{u: {}},
			out: drawerSet{w: {}},
		},
		w: edges{
			in:  drawerSet{v: {}},
			out: drawerSet{},
		},
	}
	d.removeVertex(u)
	want := dag{
		v: edges{
			in:  drawerSet{},
			out: drawerSet{w: {}},
		},
		w: edges{
			in:  drawerSet{v: {}},
			out: drawerSet{},
		},
	}
	if diff := cmp.Diff(d, want, cmp.AllowUnexported(edges{})); diff != "" {
		t.Errorf("diff after removing vertex u:\n%s", diff)
	}
	d.removeVertex(u)
	if diff := cmp.Diff(d, want, cmp.AllowUnexported(edges{})); diff != "" {
		t.Errorf("diff after removing vertex u a second time:\n%s", diff)
	}
	d.removeVertex(w)
	want = dag{
		v: edges{
			in:  drawerSet{},
			out: drawerSet{},
		},
	}
	if diff := cmp.Diff(d, want, cmp.AllowUnexported(edges{})); diff != "" {
		t.Errorf("diff after removing vertex v:\n%s", diff)
	}
}

func TestTopWalk(t *testing.T) {
	u := fakeDrawBoxer("u")
	v := fakeDrawBoxer("v")
	w := fakeDrawBoxer("w")
	d := dag{
		u: edges{
			in:  drawerSet{},
			out: drawerSet{v: {}},
		},
		v: edges{
			in:  drawerSet{u: {}},
			out: drawerSet{w: {}},
		},
		w: edges{
			in:  drawerSet{v: {}},
			out: drawerSet{},
		},
	}

	var got []Drawer
	d.topWalk(func(x Drawer) {
		got = append(got, x)
	})
	want := []Drawer{u, v, w}
	if diff := cmp.Diff(got, want); diff != "" {
		t.Errorf("topWalk visited in wrong order - diff:\n%s", diff)
	}
}

func TestTopWalkToleratesCycle(t *testing.T) {
	u := fakeDrawBoxer("u")
	v := fakeDrawBoxer("v")
	w := fakeDrawBoxer("w")
	d := dag{
		u: edges{
			in:  drawerSet{w: {}},
			out: drawerSet{v: {}},
		},
		v: edges{
			in:  drawerSet{u: {}},
			out: drawerSet{w: {}},
		},
		w: edges{
			in:  drawerSet{v: {}},
			out: drawerSet{u: {}},
		},
	}
	got := make(map[Drawer]int)
	d.topWalk(func(x Drawer) {
		got[x]++
	})
	want := map[Drawer]int{u: 1, v: 1, w: 1}
	if diff := cmp.Diff(got, want); diff != "" {
		t.Errorf("topWalk visited vertices wrong number of times - diff:\n%s", diff)
	}
}