package waddrmgr

import (
	"bytes"
	"encoding/binary"
	"errors"
	"fmt"
	"testing"
	"time"

	"github.com/btcsuite/btcd/chaincfg"
	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcwallet/walletdb"
)

// applyMigration is a helper function that allows us to assert the state of the
// top-level bucket before and after a migration. This can be used to ensure
// the correctness of migrations.
func applyMigration(t *testing.T, beforeMigration, afterMigration,
	migration func(walletdb.ReadWriteBucket) error, shouldFail bool) {

	t.Helper()

	// We'll start by setting up our address manager backed by a database.
	teardown, db, _ := setupManager(t)
	defer teardown()

	// First, we'll run the beforeMigration closure, which contains the
	// database modifications/assertions needed before proceeding with the
	// migration.
	err := walletdb.Update(db, func(tx walletdb.ReadWriteTx) error {
		ns := tx.ReadWriteBucket(waddrmgrNamespaceKey)
		if ns == nil {
			return errors.New("top-level namespace does not exist")
		}
		return beforeMigration(ns)
	})
	if err != nil {
		t.Fatalf("unable to run beforeMigration func: %v", err)
	}

	// Then, we'll run the migration itself and fail if it does not match
	// its expected result.
	err = walletdb.Update(db, func(tx walletdb.ReadWriteTx) error {
		ns := tx.ReadWriteBucket(waddrmgrNamespaceKey)
		if ns == nil {
			return errors.New("top-level namespace does not exist")
		}
		return migration(ns)
	})
	if err != nil && !shouldFail {
		t.Fatalf("unable to perform migration: %v", err)
	} else if err == nil && shouldFail {
		t.Fatal("expected migration to fail, but did not")
	}

	// Finally, we'll run the afterMigration closure, which contains the
	// assertions needed in order to guarantee than the migration was
	// successful.
	err = walletdb.Update(db, func(tx walletdb.ReadWriteTx) error {
		ns := tx.ReadWriteBucket(waddrmgrNamespaceKey)
		if ns == nil {
			return errors.New("top-level namespace does not exist")
		}
		return afterMigration(ns)
	})
	if err != nil {
		t.Fatalf("unable to run afterMigration func: %v", err)
	}
}

// TestMigrationPupulateBirthdayBlock ensures that the migration to populate the
// wallet's birthday block works as intended.
func TestMigrationPopulateBirthdayBlock(t *testing.T) {
	t.Parallel()

	var expectedHeight int32
	beforeMigration := func(ns walletdb.ReadWriteBucket) error {
		// To test this migration, we'll start by writing to disk 10
		// random blocks.
		block := &BlockStamp{}
		for i := int32(1); i <= 10; i++ {
			block.Height = i
			blockHash := bytes.Repeat([]byte(string(i)), 32)
			copy(block.Hash[:], blockHash)
			if err := PutSyncedTo(ns, block); err != nil {
				return err
			}
		}

		// With the blocks inserted, we'll assume that the birthday
		// block corresponds to the 7th block (out of 11) in the chain.
		// To do this, we'll need to set our birthday timestamp to the
		// estimated timestamp of a block that's 6 blocks after genesis.
		genesisTimestamp := chaincfg.MainNetParams.GenesisBlock.Header.Timestamp
		delta := time.Hour
		expectedHeight = int32(delta.Seconds() / 600)
		birthday := genesisTimestamp.Add(delta)
		if err := putBirthday(ns, birthday); err != nil {
			return err
		}

		// Finally, since the migration has not yet started, we should
		// not be able to find the birthday block within the database.
		_, err := FetchBirthdayBlock(ns)
		if !IsError(err, ErrBirthdayBlockNotSet) {
			return fmt.Errorf("expected ErrBirthdayBlockNotSet, "+
				"got %v", err)
		}

		return nil
	}

	// After the migration has completed, we should see that the birthday
	// block now exists and is set to the correct expected height.
	afterMigration := func(ns walletdb.ReadWriteBucket) error {
		birthdayBlock, err := FetchBirthdayBlock(ns)
		if err != nil {
			return err
		}

		if birthdayBlock.Height != expectedHeight {
			return fmt.Errorf("expected birthday block with "+
				"height %d, got %d", expectedHeight,
				birthdayBlock.Height)
		}

		return nil
	}

	// We can now apply the migration and expect it not to fail.
	applyMigration(
		t, beforeMigration, afterMigration, populateBirthdayBlock,
		false,
	)
}

// TestMigrationPopulateBirthdayBlockEstimateTooFar ensures that the migration
// can properly detect a height estimate which the chain from our point of view
// has not yet reached.
func TestMigrationPopulateBirthdayBlockEstimateTooFar(t *testing.T) {
	t.Parallel()

	const numBlocks = 1000
	chainParams := chaincfg.MainNetParams

	var expectedHeight int32
	beforeMigration := func(ns walletdb.ReadWriteBucket) error {
		// To test this migration, we'll start by writing to disk 999
		// random blocks to simulate a synced chain with height 1000.
		block := &BlockStamp{}
		for i := int32(1); i < numBlocks; i++ {
			block.Height = i
			blockHash := bytes.Repeat([]byte(string(i)), 32)
			copy(block.Hash[:], blockHash)
			if err := PutSyncedTo(ns, block); err != nil {
				return err
			}
		}

		// With the blocks inserted, we'll assume that the birthday
		// block corresponds to the 900th block in the chain. To do
		// this, we'd need to set our birthday timestamp to the
		// estimated timestamp of a block that's 899 blocks after
		// genesis. However, this will not work if the average block
		// time is not 10 mins, which can throw off the height estimate
		// with a height longer than the chain in the event of test
		// networks (testnet, regtest, etc. and not fully synced
		// wallets). Instead the migration should be able to handle this
		// by subtracting a days worth of blocks until finding a block
		// that it is aware of.
		//
		// We'll have the migration assume that our birthday is at block
		// 1001 in the chain. Since this block doesn't exist from the
		// database's point of view, a days worth of blocks will be
		// subtracted from the estimate, which should give us a valid
		// block height.
		genesisTimestamp := chainParams.GenesisBlock.Header.Timestamp
		delta := numBlocks * 10 * time.Minute
		expectedHeight = numBlocks - 144

		birthday := genesisTimestamp.Add(delta)
		if err := putBirthday(ns, birthday); err != nil {
			return err
		}

		// Finally, since the migration has not yet started, we should
		// not be able to find the birthday block within the database.
		_, err := FetchBirthdayBlock(ns)
		if !IsError(err, ErrBirthdayBlockNotSet) {
			return fmt.Errorf("expected ErrBirthdayBlockNotSet, "+
				"got %v", err)
		}

		return nil
	}

	// After the migration has completed, we should see that the birthday
	// block now exists and is set to the correct expected height.
	afterMigration := func(ns walletdb.ReadWriteBucket) error {
		birthdayBlock, err := FetchBirthdayBlock(ns)
		if err != nil {
			return err
		}

		if birthdayBlock.Height != expectedHeight {
			return fmt.Errorf("expected birthday block height %d, "+
				"got %d", expectedHeight, birthdayBlock.Height)
		}

		return nil
	}

	// We can now apply the migration and expect it not to fail.
	applyMigration(
		t, beforeMigration, afterMigration, populateBirthdayBlock,
		false,
	)
}

// TestMigrationResetSyncedBlockToBirthday ensures that the wallet properly sees
// its synced to block as the birthday block after resetting it.
func TestMigrationResetSyncedBlockToBirthday(t *testing.T) {
	t.Parallel()

	var birthdayBlock BlockStamp
	beforeMigration := func(ns walletdb.ReadWriteBucket) error {
		// To test this migration, we'll assume we're synced to a chain
		// of 100 blocks, with our birthday being the 50th block.
		block := &BlockStamp{}
		for i := int32(1); i < 100; i++ {
			block.Height = i
			blockHash := bytes.Repeat([]byte(string(i)), 32)
			copy(block.Hash[:], blockHash)
			if err := PutSyncedTo(ns, block); err != nil {
				return err
			}
		}

		const birthdayHeight = 50
		birthdayHash, err := fetchBlockHash(ns, birthdayHeight)
		if err != nil {
			return err
		}

		birthdayBlock = BlockStamp{
			Hash: *birthdayHash, Height: birthdayHeight,
		}

		return putBirthdayBlock(ns, birthdayBlock)
	}

	afterMigration := func(ns walletdb.ReadWriteBucket) error {
		// After the migration has succeeded, we should see that the
		// database's synced block now reflects the birthday block.
		syncedBlock, err := fetchSyncedTo(ns)
		if err != nil {
			return err
		}

		if syncedBlock.Height != birthdayBlock.Height {
			return fmt.Errorf("expected synced block height %d, "+
				"got %d", birthdayBlock.Height,
				syncedBlock.Height)
		}
		if !syncedBlock.Hash.IsEqual(&birthdayBlock.Hash) {
			return fmt.Errorf("expected synced block height %v, "+
				"got %v", birthdayBlock.Hash, syncedBlock.Hash)
		}

		return nil
	}

	// We can now apply the migration and expect it not to fail.
	applyMigration(
		t, beforeMigration, afterMigration, resetSyncedBlockToBirthday,
		false,
	)
}

// TestMigrationResetSyncedBlockToBirthdayWithNoBirthdayBlock ensures that we
// cannot reset our synced to block to our birthday block if one isn't
// available.
func TestMigrationResetSyncedBlockToBirthdayWithNoBirthdayBlock(t *testing.T) {
	t.Parallel()

	// To replicate the scenario where the database is not aware of a
	// birthday block, we won't set one. This should cause the migration to
	// fail.
	beforeMigration := func(walletdb.ReadWriteBucket) error {
		return nil
	}
	afterMigration := func(walletdb.ReadWriteBucket) error {
		return nil
	}
	applyMigration(
		t, beforeMigration, afterMigration, resetSyncedBlockToBirthday,
		true,
	)
}

// TestMigrationStoreMaxReorgDepth ensures that the storeMaxReorgDepth migration
// works as expected under different sync scenarios.
func TestMigrationStoreMaxReorgDepth(t *testing.T) {
	t.Parallel()

	testCases := []struct {
		name      string
		numBlocks int32
	}{
		{
			name:      "genesis only",
			numBlocks: 0,
		},
		{
			name:      "below max reorg depth",
			numBlocks: MaxReorgDepth - 1,
		},
		{
			name:      "above max reorg depth",
			numBlocks: MaxReorgDepth + 1,
		},
		{
			name:      "double max reorg depth",
			numBlocks: MaxReorgDepth * 2,
		},
	}

	for _, testCase := range testCases {
		success := t.Run(testCase.name, func(t *testing.T) {
			// We'll start the test by creating the number of blocks
			// we'll add to the chain. We start from height 1 as the
			// genesis block (height 0) is already included when the
			// address manager is created.
			blocks := make([]*BlockStamp, 0, testCase.numBlocks)
			for i := int32(1); i <= testCase.numBlocks; i++ {
				var hash chainhash.Hash
				binary.BigEndian.PutUint32(hash[:], uint32(i))
				blocks = append(blocks, &BlockStamp{
					Hash:   hash,
					Height: i,
				})
			}

			// Before the migration, we'll go ahead and add all of
			// the blocks created. This simulates the behavior of an
			// existing synced chain. We won't use PutSyncedTo as
			// that would remove the stale entries on its own.
			beforeMigration := func(ns walletdb.ReadWriteBucket) error {
				if testCase.numBlocks == 0 {
					return nil
				}

				// Write all the block hash entries.
				for _, block := range blocks {
					err := addBlockHash(
						ns, block.Height, block.Hash,
					)
					if err != nil {
						return err
					}
					err = updateSyncedTo(ns, block)
					if err != nil {
						return err
					}
				}

				// Check to make sure they've been added
				// properly.
				for _, block := range blocks {
					hash, err := fetchBlockHash(
						ns, block.Height,
					)
					if err != nil {
						return err
					}
					if *hash != block.Hash {
						return fmt.Errorf("expected "+
							"hash %v for height "+
							"%v, got %v",
							block.Hash,
							block.Height, hash)
					}
				}
				block, err := fetchSyncedTo(ns)
				if err != nil {
					return err
				}
				expectedBlock := blocks[len(blocks)-1]
				if block.Height != block.Height {
					return fmt.Errorf("expected synced to "+
						"block height %v, got %v",
						expectedBlock.Height,
						block.Height)
				}
				if block.Hash != block.Hash {
					return fmt.Errorf("expected synced to "+
						"block hash %v, got %v",
						expectedBlock.Hash,
						block.Hash)
				}

				return nil
			}

			// After the migration, we'll ensure we're unable to
			// find all the block hashes that should have been
			// removed.
			afterMigration := func(ns walletdb.ReadWriteBucket) error {
				maxStaleHeight := staleHeight(testCase.numBlocks)
				for _, block := range blocks {
					if block.Height <= maxStaleHeight {
						_, err := fetchBlockHash(
							ns, block.Height,
						)
						if IsError(err, ErrBlockNotFound) {
							continue
						}
						return fmt.Errorf("expected "+
							"ErrBlockNotFound for "+
							"height %v, got %v",
							block.Height, err)
					}

					hash, err := fetchBlockHash(
						ns, block.Height,
					)
					if err != nil {
						return err
					}
					if *hash != block.Hash {
						return fmt.Errorf("expected "+
							"hash %v for height "+
							"%v, got %v",
							block.Hash,
							block.Height, hash)
					}
				}
				return nil
			}

			applyMigration(
				t, beforeMigration, afterMigration,
				storeMaxReorgDepth, false,
			)
		})
		if !success {
			return
		}
	}
}