package pfile

import (
	"testing"
)

type IndexState struct {
	FreeList  []uint64
	AllocList map[[2]uint64][]uint64
}

func (idx *Index) Assert(t *testing.T, state IndexState) {
	t.Helper()

	idx.fList.Assert(t, state.FreeList...)
	idx.aList.Assert(t, state.AllocList)
}

func TestIndex(t *testing.T) {
	pf, idx := newForTesting(t)
	defer pf.Close()

	idx.Assert(t, IndexState{
		FreeList:  []uint64{},
		AllocList: map[[2]uint64][]uint64{},
	})

	p0 := uint64(0)

	l := (&changeListBuilder{}).
		Store(1, 1, pageDataSize+1).
		Build()

	idx.StageChanges(l)

	idx.Assert(t, IndexState{
		FreeList:  []uint64{},
		AllocList: map[[2]uint64][]uint64{},
	})

	// Unstage a change: free-list gets pages back.
	idx.UnstageChanges(l)

	idx.Assert(t, IndexState{
		FreeList:  []uint64{p0, p0 + 1},
		AllocList: map[[2]uint64][]uint64{},
	})

	// Stage a change: free-list entries are used again.
	l = (*changeListBuilder)(&l).
		Clear().
		Store(1, 1, pageDataSize+1).
		Store(2, 2, pageDataSize-1).
		Store(3, 3, pageDataSize).
		Build()

	idx.StageChanges(l)

	idx.Assert(t, IndexState{
		FreeList:  []uint64{},
		AllocList: map[[2]uint64][]uint64{},
	})

	// Apply changes: alloc-list is updated.
	idx.ApplyChanges(l)

	idx.Assert(t, IndexState{
		FreeList: []uint64{},
		AllocList: map[[2]uint64][]uint64{
			{1, 1}: {p0, p0 + 1},
			{2, 2}: {p0 + 2},
			{3, 3}: {p0 + 3},
		},
	})

	// Clear some things.
	l = (*changeListBuilder)(&l).
		Clear().
		Store(1, 1, pageDataSize).
		Delete(2, 2).
		Build()

	idx.StageChanges(l)

	idx.Assert(t, IndexState{
		FreeList: []uint64{},
		AllocList: map[[2]uint64][]uint64{
			{3, 3}: {p0 + 3},
		},
	})

	// Ustaging will push the staged page p0+4 into the free list.
	idx.UnstageChanges(l)

	idx.Assert(t, IndexState{
		FreeList: []uint64{p0 + 4},
		AllocList: map[[2]uint64][]uint64{
			{1, 1}: {p0, p0 + 1},
			{2, 2}: {p0 + 2},
			{3, 3}: {p0 + 3},
		},
	})

	idx.StageChanges(l)

	idx.Assert(t, IndexState{
		FreeList: []uint64{},
		AllocList: map[[2]uint64][]uint64{
			{3, 3}: {p0 + 3},
		},
	})

	idx.ApplyChanges(l)

	idx.Assert(t, IndexState{
		FreeList: []uint64{p0, p0 + 1, p0 + 2},
		AllocList: map[[2]uint64][]uint64{
			{1, 1}: {p0 + 4},
			{3, 3}: {p0 + 3},
		},
	})

	// Duplicate updates.
	l = (*changeListBuilder)(&l).
		Clear().
		Store(2, 2, pageDataSize).
		Store(3, 3, pageDataSize+1).
		Store(3, 3, pageDataSize).
		Build()

	idx.StageChanges(l)

	idx.Assert(t, IndexState{
		FreeList: []uint64{p0 + 2},
		AllocList: map[[2]uint64][]uint64{
			{1, 1}: {p0 + 4},
		},
	})
}