package commands

import (
	"bytes"
	"testing"

	"github.com/RoaringBitmap/roaring/roaring64"
)

func newMockBackwardChunkLocator(chunks [][]byte) ChunkLocator {
	return func(block uint64) (ChunkProvider, bool, error) {
		for i, v := range chunks {
			bm := roaring64.NewBitmap()
			if _, err := bm.ReadFrom(bytes.NewReader(v)); err != nil {
				return nil, false, err
			}
			if block > bm.Maximum() {
				continue
			}

			return newMockBackwardChunkProvider(chunks[:i+1]), true, nil
		}

		// Not found; return the last to simulate the behavior of returning
		// everything up to the 0xffff... chunk
		if len(chunks) > 0 {
			return newMockBackwardChunkProvider(chunks), true, nil
		}

		return nil, true, nil
	}
}

func newMockBackwardChunkProvider(chunks [][]byte) ChunkProvider {
	i := len(chunks) - 1
	return func() ([]byte, bool, error) {
		if i < 0 {
			return nil, false, nil
		}

		chunk := chunks[i]
		i--
		return chunk, true, nil
	}
}
func TestBackwardBlockProviderWith1Chunk(t *testing.T) {
	// Mocks 1 chunk
	chunk1 := createBitmap(t, []uint64{1000, 1005, 1010})

	chunkLocator := newMockBackwardChunkLocator([][]byte{chunk1})
	blockProvider := NewBackwardBlockProvider(chunkLocator, 0)

	checkNext(t, blockProvider, 1010, true)
	checkNext(t, blockProvider, 1005, true)
	checkNext(t, blockProvider, 1000, false)
}

func TestBackwardBlockProviderWith1ChunkMiddleBlock(t *testing.T) {
	// Mocks 1 chunk
	chunk1 := createBitmap(t, []uint64{1000, 1005, 1010})

	chunkLocator := newMockBackwardChunkLocator([][]byte{chunk1})
	blockProvider := NewBackwardBlockProvider(chunkLocator, 1005)

	checkNext(t, blockProvider, 1005, true)
	checkNext(t, blockProvider, 1000, false)
}

func TestBackwardBlockProviderWith1ChunkNotExactBlock(t *testing.T) {
	// Mocks 1 chunk
	chunk1 := createBitmap(t, []uint64{1000, 1005, 1010})

	chunkLocator := newMockBackwardChunkLocator([][]byte{chunk1})
	blockProvider := NewBackwardBlockProvider(chunkLocator, 1003)

	checkNext(t, blockProvider, 1000, false)
}

func TestBackwardBlockProviderWith1ChunkLastBlock(t *testing.T) {
	// Mocks 1 chunk
	chunk1 := createBitmap(t, []uint64{1000, 1005, 1010})

	chunkLocator := newMockBackwardChunkLocator([][]byte{chunk1})
	blockProvider := NewBackwardBlockProvider(chunkLocator, 1000)

	checkNext(t, blockProvider, 1000, false)
}

func TestBackwardBlockProviderWith1ChunkBlockNotFound(t *testing.T) {
	// Mocks 1 chunk
	chunk1 := createBitmap(t, []uint64{1000, 1005, 1010})

	chunkLocator := newMockBackwardChunkLocator([][]byte{chunk1})
	blockProvider := NewBackwardBlockProvider(chunkLocator, 900)

	checkNext(t, blockProvider, 0, false)
}

func TestBackwardBlockProviderWithNoChunks(t *testing.T) {
	chunkLocator := newMockBackwardChunkLocator([][]byte{})
	blockProvider := NewBackwardBlockProvider(chunkLocator, 0)

	checkNext(t, blockProvider, 0, false)
}

func TestBackwardBlockProviderWithMultipleChunks(t *testing.T) {
	// Mocks 2 chunks
	chunk1 := createBitmap(t, []uint64{1000, 1005, 1010})
	chunk2 := createBitmap(t, []uint64{1501, 1600})

	chunkLocator := newMockBackwardChunkLocator([][]byte{chunk1, chunk2})
	blockProvider := NewBackwardBlockProvider(chunkLocator, 0)

	checkNext(t, blockProvider, 1600, true)
	checkNext(t, blockProvider, 1501, true)
	checkNext(t, blockProvider, 1010, true)
	checkNext(t, blockProvider, 1005, true)
	checkNext(t, blockProvider, 1000, false)
}

func TestBackwardBlockProviderWithMultipleChunksBlockBetweenChunks(t *testing.T) {
	// Mocks 2 chunks
	chunk1 := createBitmap(t, []uint64{1000, 1005, 1010})
	chunk2 := createBitmap(t, []uint64{1501, 1600})

	chunkLocator := newMockBackwardChunkLocator([][]byte{chunk1, chunk2})
	blockProvider := NewBackwardBlockProvider(chunkLocator, 1500)

	checkNext(t, blockProvider, 1010, true)
	checkNext(t, blockProvider, 1005, true)
	checkNext(t, blockProvider, 1000, false)
}

func TestBackwardBlockProviderWithMultipleChunksBlockNotFound(t *testing.T) {
	// Mocks 2 chunks
	chunk1 := createBitmap(t, []uint64{1000, 1005, 1010})
	chunk2 := createBitmap(t, []uint64{1501, 1600})

	chunkLocator := newMockBackwardChunkLocator([][]byte{chunk1, chunk2})
	blockProvider := NewBackwardBlockProvider(chunkLocator, 900)

	checkNext(t, blockProvider, 0, false)
}