// Copyright 2024 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package doctree_test

import (
	"context"
	"fmt"
	"math/rand"
	"path"
	"strings"
	"testing"

	qt "github.com/frankban/quicktest"
	"github.com/gohugoio/hugo/common/para"
	"github.com/gohugoio/hugo/hugolib/doctree"
	"github.com/google/go-cmp/cmp"
)

var eq = qt.CmpEquals(
	cmp.Comparer(func(n1, n2 *testValue) bool {
		if n1 == n2 {
			return true
		}

		return n1.ID == n2.ID && n1.Lang == n2.Lang
	}),
)

func TestTree(t *testing.T) {
	c := qt.New(t)

	zeroZero := doctree.New(
		doctree.Config[*testValue]{
			Shifter: &testShifter{},
		},
	)

	a := &testValue{ID: "/a"}
	zeroZero.InsertIntoValuesDimension("/a", a)
	ab := &testValue{ID: "/a/b"}
	zeroZero.InsertIntoValuesDimension("/a/b", ab)

	c.Assert(zeroZero.Get("/a"), eq, &testValue{ID: "/a", Lang: 0})
	s, v := zeroZero.LongestPrefix("/a/b/c", true, nil)
	c.Assert(v, eq, ab)
	c.Assert(s, eq, "/a/b")

	// Change language.
	oneZero := zeroZero.Increment(0)
	c.Assert(zeroZero.Get("/a"), eq, &testValue{ID: "/a", Lang: 0})
	c.Assert(oneZero.Get("/a"), eq, &testValue{ID: "/a", Lang: 1})
}

func TestTreeData(t *testing.T) {
	c := qt.New(t)

	tree := doctree.New(
		doctree.Config[*testValue]{
			Shifter: &testShifter{},
		},
	)

	tree.InsertIntoValuesDimension("", &testValue{ID: "HOME"})
	tree.InsertIntoValuesDimension("/a", &testValue{ID: "/a"})
	tree.InsertIntoValuesDimension("/a/b", &testValue{ID: "/a/b"})
	tree.InsertIntoValuesDimension("/b", &testValue{ID: "/b"})
	tree.InsertIntoValuesDimension("/b/c", &testValue{ID: "/b/c"})
	tree.InsertIntoValuesDimension("/b/c/d", &testValue{ID: "/b/c/d"})

	var values []string

	ctx := &doctree.WalkContext[*testValue]{}

	w := &doctree.NodeShiftTreeWalker[*testValue]{
		Tree:        tree,
		WalkContext: ctx,
		Handle: func(s string, t *testValue, match doctree.DimensionFlag) (bool, error) {
			ctx.Data().Insert(s, map[string]any{
				"id": t.ID,
			})

			if s != "" {
				p, v := ctx.Data().LongestPrefix(path.Dir(s))
				values = append(values, fmt.Sprintf("%s:%s:%v", s, p, v))
			}
			return false, nil
		},
	}

	w.Walk(context.Background())

	c.Assert(strings.Join(values, "|"), qt.Equals, "/a::map[id:HOME]|/a/b:/a:map[id:/a]|/b::map[id:HOME]|/b/c:/b:map[id:/b]|/b/c/d:/b/c:map[id:/b/c]")
}

func TestTreeEvents(t *testing.T) {
	c := qt.New(t)

	tree := doctree.New(
		doctree.Config[*testValue]{
			Shifter: &testShifter{echo: true},
		},
	)

	tree.InsertIntoValuesDimension("/a", &testValue{ID: "/a", Weight: 2, IsBranch: true})
	tree.InsertIntoValuesDimension("/a/p1", &testValue{ID: "/a/p1", Weight: 5})
	tree.InsertIntoValuesDimension("/a/p", &testValue{ID: "/a/p2", Weight: 6})
	tree.InsertIntoValuesDimension("/a/s1", &testValue{ID: "/a/s1", Weight: 5, IsBranch: true})
	tree.InsertIntoValuesDimension("/a/s1/p1", &testValue{ID: "/a/s1/p1", Weight: 8})
	tree.InsertIntoValuesDimension("/a/s1/p1", &testValue{ID: "/a/s1/p2", Weight: 9})
	tree.InsertIntoValuesDimension("/a/s1/s2", &testValue{ID: "/a/s1/s2", Weight: 6, IsBranch: true})
	tree.InsertIntoValuesDimension("/a/s1/s2/p1", &testValue{ID: "/a/s1/s2/p1", Weight: 8})
	tree.InsertIntoValuesDimension("/a/s1/s2/p2", &testValue{ID: "/a/s1/s2/p2", Weight: 7})

	w := &doctree.NodeShiftTreeWalker[*testValue]{
		Tree:        tree,
		WalkContext: &doctree.WalkContext[*testValue]{},
	}

	w.Handle = func(s string, t *testValue, match doctree.DimensionFlag) (bool, error) {
		if t.IsBranch {
			w.WalkContext.AddEventListener("weight", s, func(e *doctree.Event[*testValue]) {
				if e.Source.Weight > t.Weight {
					t.Weight = e.Source.Weight
					w.WalkContext.SendEvent(&doctree.Event[*testValue]{Source: t, Path: s, Name: "weight"})
				}
				// Reduces the amount of events bubbling up the tree. If the weight for this branch has
				// increased, that will be announced in its own event.
				e.StopPropagation()
			})
		} else {
			w.WalkContext.SendEvent(&doctree.Event[*testValue]{Source: t, Path: s, Name: "weight"})
		}

		return false, nil
	}

	c.Assert(w.Walk(context.Background()), qt.IsNil)
	c.Assert(w.WalkContext.HandleEventsAndHooks(), qt.IsNil)

	c.Assert(tree.Get("/a").Weight, eq, 9)
	c.Assert(tree.Get("/a/s1").Weight, eq, 9)
	c.Assert(tree.Get("/a/p").Weight, eq, 6)
	c.Assert(tree.Get("/a/s1/s2").Weight, eq, 8)
	c.Assert(tree.Get("/a/s1/s2/p2").Weight, eq, 7)
}

func TestTreeInsert(t *testing.T) {
	c := qt.New(t)

	tree := doctree.New(
		doctree.Config[*testValue]{
			Shifter: &testShifter{},
		},
	)

	a := &testValue{ID: "/a"}
	tree.InsertIntoValuesDimension("/a", a)
	ab := &testValue{ID: "/a/b"}
	tree.InsertIntoValuesDimension("/a/b", ab)

	c.Assert(tree.Get("/a"), eq, &testValue{ID: "/a", Lang: 0})
	c.Assert(tree.Get("/notfound"), qt.IsNil)

	ab2 := &testValue{ID: "/a/b", Lang: 0}
	v, ok := tree.InsertIntoValuesDimension("/a/b", ab2)
	c.Assert(ok, qt.IsTrue)
	c.Assert(v, qt.DeepEquals, ab2)

	tree1 := tree.Increment(0)
	c.Assert(tree1.Get("/a/b"), qt.DeepEquals, &testValue{ID: "/a/b", Lang: 1})
}

func TestTreePara(t *testing.T) {
	c := qt.New(t)

	p := para.New(4)
	r, _ := p.Start(context.Background())

	tree := doctree.New(
		doctree.Config[*testValue]{
			Shifter: &testShifter{},
		},
	)

	for i := 0; i < 8; i++ {
		i := i
		r.Run(func() error {
			a := &testValue{ID: "/a"}
			lock := tree.Lock(true)
			defer lock()
			tree.InsertIntoValuesDimension("/a", a)
			ab := &testValue{ID: "/a/b"}
			tree.InsertIntoValuesDimension("/a/b", ab)

			key := fmt.Sprintf("/a/b/c/%d", i)
			val := &testValue{ID: key}
			tree.InsertIntoValuesDimension(key, val)
			c.Assert(tree.Get(key), eq, val)
			// s, _ := tree.LongestPrefix(key, nil)
			// c.Assert(s, eq, "/a/b")

			return nil
		})
	}

	c.Assert(r.Wait(), qt.IsNil)
}

func TestValidateKey(t *testing.T) {
	c := qt.New(t)

	c.Assert(doctree.ValidateKey(""), qt.IsNil)
	c.Assert(doctree.ValidateKey("/a/b/c"), qt.IsNil)
	c.Assert(doctree.ValidateKey("/"), qt.IsNotNil)
	c.Assert(doctree.ValidateKey("a"), qt.IsNotNil)
	c.Assert(doctree.ValidateKey("abc"), qt.IsNotNil)
	c.Assert(doctree.ValidateKey("/abc/"), qt.IsNotNil)
}

type testShifter struct {
	echo bool
}

func (s *testShifter) ForEeachInDimension(n *testValue, d int, f func(n *testValue) bool) {
	if d != doctree.DimensionLanguage.Index() {
		panic("not implemented")
	}
	f(n)
}

func (s *testShifter) Insert(old, new *testValue) *testValue {
	return new
}

func (s *testShifter) InsertInto(old, new *testValue, dimension doctree.Dimension) *testValue {
	return new
}

func (s *testShifter) Delete(n *testValue, dimension doctree.Dimension) (bool, bool) {
	return true, true
}

func (s *testShifter) Shift(n *testValue, dimension doctree.Dimension, exact bool) (*testValue, bool, doctree.DimensionFlag) {
	if s.echo {
		return n, true, doctree.DimensionLanguage
	}
	if n.NoCopy {
		if n.Lang == dimension[0] {
			return n, true, doctree.DimensionLanguage
		}
		return nil, false, doctree.DimensionLanguage
	}
	c := *n
	c.Lang = dimension[0]
	return &c, true, doctree.DimensionLanguage
}

func (s *testShifter) All(n *testValue) []*testValue {
	return []*testValue{n}
}

type testValue struct {
	ID   string
	Lang int

	Weight   int
	IsBranch bool

	NoCopy bool
}

func BenchmarkTreeInsert(b *testing.B) {
	runBench := func(b *testing.B, numElements int) {
		for i := 0; i < b.N; i++ {
			tree := doctree.New(
				doctree.Config[*testValue]{
					Shifter: &testShifter{},
				},
			)

			for i := 0; i < numElements; i++ {
				lang := rand.Intn(2)
				tree.InsertIntoValuesDimension(fmt.Sprintf("/%d", i), &testValue{ID: fmt.Sprintf("/%d", i), Lang: lang, Weight: i, NoCopy: true})
			}
		}
	}

	b.Run("1000", func(b *testing.B) {
		runBench(b, 1000)
	})

	b.Run("10000", func(b *testing.B) {
		runBench(b, 10000)
	})

	b.Run("100000", func(b *testing.B) {
		runBench(b, 100000)
	})

	b.Run("300000", func(b *testing.B) {
		runBench(b, 300000)
	})
}

func BenchmarkWalk(b *testing.B) {
	const numElements = 1000

	createTree := func() *doctree.NodeShiftTree[*testValue] {
		tree := doctree.New(
			doctree.Config[*testValue]{
				Shifter: &testShifter{},
			},
		)

		for i := 0; i < numElements; i++ {
			lang := rand.Intn(2)
			tree.InsertIntoValuesDimension(fmt.Sprintf("/%d", i), &testValue{ID: fmt.Sprintf("/%d", i), Lang: lang, Weight: i, NoCopy: true})
		}

		return tree
	}

	handle := func(s string, t *testValue, match doctree.DimensionFlag) (bool, error) {
		return false, nil
	}

	for _, numElements := range []int{1000, 10000, 100000} {

		b.Run(fmt.Sprintf("Walk one dimension %d", numElements), func(b *testing.B) {
			tree := createTree()
			b.ResetTimer()
			for i := 0; i < b.N; i++ {
				w := &doctree.NodeShiftTreeWalker[*testValue]{
					Tree:   tree,
					Handle: handle,
				}
				if err := w.Walk(context.Background()); err != nil {
					b.Fatal(err)
				}
			}
		})

		b.Run(fmt.Sprintf("Walk all dimensions %d", numElements), func(b *testing.B) {
			base := createTree()
			b.ResetTimer()
			for i := 0; i < b.N; i++ {
				for d1 := 0; d1 < 1; d1++ {
					for d2 := 0; d2 < 2; d2++ {
						tree := base.Shape(d1, d2)
						w := &doctree.NodeShiftTreeWalker[*testValue]{
							Tree:   tree,
							Handle: handle,
						}
						if err := w.Walk(context.Background()); err != nil {
							b.Fatal(err)
						}
					}
				}
			}
		})

	}
}
