4 files changed, 357 insertions, 0 deletions
diff --git a/pkg/blockchain/coindatabase/coin.go b/pkg/blockchain/coindatabase/coin.go
new file mode 100644
index 0000000..4281ac1
--- /dev/null
+++ b/pkg/blockchain/coindatabase/coin.go
@@ -0,0 +1,29 @@
+package coindatabase
+
+import "Chain/pkg/block"
+
+// Coin is used by the CoinDatabase to keep track of unspent
+// TransactionOutputs.
+// TransactionOutput is the underlying TransactionOutput.
+// IsSpent is whether that TransactionOutput has been spent.
+// Active is whether that TransactionOutput is one created by
+// Blocks on the active Chain.
+type Coin struct {
+	TransactionOutput *block.TransactionOutput
+	IsSpent           bool
+}
+
+// CoinLocator is a dumbed down TransactionInput, used
+// as a key to Coins in the CoinDatabase's mainCache.
+type CoinLocator struct {
+	ReferenceTransactionHash string
+	OutputIndex              uint32
+}
+
+// makeCoinLocator returns a CoinLocator given a TransactionInput.
+func makeCoinLocator(txi *block.TransactionInput) CoinLocator {
+	return CoinLocator{
+		ReferenceTransactionHash: txi.ReferenceTransactionHash,
+		OutputIndex:              txi.OutputIndex,
+	}
+}
diff --git a/pkg/blockchain/coindatabase/coindatabase.go b/pkg/blockchain/coindatabase/coindatabase.go
new file mode 100644
index 0000000..83b3026
--- /dev/null
+++ b/pkg/blockchain/coindatabase/coindatabase.go
@@ -0,0 +1,265 @@
+package coindatabase
+
+import (
+	"Chain/pkg/block"
+	"Chain/pkg/blockchain/chainwriter"
+	"Chain/pkg/pro"
+	"Chain/pkg/utils"
+	"fmt"
+	"github.com/syndtr/goleveldb/leveldb"
+	"google.golang.org/protobuf/proto"
+)
+
+// CoinDatabase keeps track of Coins.
+// db is a levelDB for persistent storage.
+// mainCache stores as many Coins as possible for rapid validation.
+// mainCacheSize is how many Coins are currently in the mainCache.
+// mainCacheCapacity is the maximum number of Coins that the mainCache
+// can store before it must flush.
+type CoinDatabase struct {
+	db                *leveldb.DB
+	mainCache         map[CoinLocator]*Coin
+	mainCacheSize     uint32
+	mainCacheCapacity uint32
+}
+
+// New returns a CoinDatabase given a Config.
+func New(config *Config) *CoinDatabase {
+	db, err := leveldb.OpenFile(config.DatabasePath, nil)
+	if err != nil {
+		utils.Debug.Printf("Unable to initialize BlockInfoDatabase with path {%v}", config.DatabasePath)
+	}
+	return &CoinDatabase{
+		db:                db,
+		mainCache:         make(map[CoinLocator]*Coin),
+		mainCacheSize:     0,
+		mainCacheCapacity: config.MainCacheCapacity,
+	}
+}
+
+// ValidateBlock returns whether a Block's Transactions are valid.
+func (coinDB *CoinDatabase) ValidateBlock(transactions []*block.Transaction) bool {
+	for _, tx := range transactions {
+		if err := coinDB.validateTransaction(tx); err != nil {
+			utils.Debug.Printf("%v", err)
+			return false
+		}
+	}
+	return true
+}
+
+// validateTransaction checks whether a Transaction's inputs are valid Coins.
+// If the Coins have already been spent or do not exist, validateTransaction
+// returns an error.
+func (coinDB *CoinDatabase) validateTransaction(transaction *block.Transaction) error {
+	for _, txi := range transaction.Inputs {
+		key := makeCoinLocator(txi)
+		if coin, ok := coinDB.mainCache[key]; ok {
+			if coin.IsSpent {
+				return fmt.Errorf("[validateTransaction] coin already spent")
+			}
+			continue
+		}
+		if data, err := coinDB.db.Get([]byte(txi.ReferenceTransactionHash), nil); err != nil {
+			return fmt.Errorf("[validateTransaction] coin not in leveldb")
+		} else {
+			pcr := &pro.CoinRecord{}
+			if err2 := proto.Unmarshal(data, pcr); err2 != nil {
+				utils.Debug.Printf("Failed to unmarshal record from hash {%v}:", txi.ReferenceTransactionHash, err)
+			}
+			cr := DecodeCoinRecord(pcr)
+			if !contains(cr.OutputIndexes, txi.OutputIndex) {
+				return fmt.Errorf("[validateTransaction] coin record did not still contain output required for transaction input ")
+			}
+		}
+	}
+	return nil
+}
+
+// UndoCoins handles reverting a Block. It:
+// (1) erases the Coins created by a Block and
+// (2) marks the Coins used to create those Transactions as unspent.
+func (coinDB *CoinDatabase) UndoCoins(blocks []*block.Block, undoBlocks []*chainwriter.UndoBlock) {
+	//TODO
+}
+
+// addCoinsToRecord adds coins to a CoinRecord given an UndoBlock and
+// returns the updated CoinRecord.
+func (coinDB *CoinDatabase) addCoinsToRecord(cr *CoinRecord, ub *chainwriter.UndoBlock) *CoinRecord {
+	cr.OutputIndexes = append(cr.OutputIndexes, ub.OutputIndexes...)
+	cr.Amounts = append(cr.Amounts, ub.Amounts...)
+	cr.LockingScripts = append(cr.LockingScripts, ub.LockingScripts...)
+	return cr
+}
+
+// FlushMainCache flushes the mainCache to the db.
+func (coinDB *CoinDatabase) FlushMainCache() {
+	// update coin records
+	updatedCoinRecords := make(map[string]*CoinRecord)
+	for cl := range coinDB.mainCache {
+		// check whether we already updated this record
+		var cr *CoinRecord
+
+		// (1) get our coin record
+		// first check our map, in case we already updated the coin record given
+		// a previous coin
+		if cr2, ok := updatedCoinRecords[cl.ReferenceTransactionHash]; ok {
+			cr = cr2
+		} else {
+			// if we haven't already update this coin record, retrieve from db
+			data, err := coinDB.db.Get([]byte(cl.ReferenceTransactionHash), nil)
+			if err != nil {
+				utils.Debug.Printf("[FlushMainCache] coin record not in leveldb")
+			}
+			pcr := &pro.CoinRecord{}
+			if err = proto.Unmarshal(data, pcr); err != nil {
+				utils.Debug.Printf("Failed to unmarshal record from hash {%v}:%v", cl.ReferenceTransactionHash, err)
+			}
+			cr = DecodeCoinRecord(pcr)
+		}
+		// (2) remove the coin from the record if it's been spent
+		if coinDB.mainCache[cl].IsSpent {
+			cr = coinDB.removeCoinFromRecord(cr, cl.OutputIndex)
+		}
+		updatedCoinRecords[cl.ReferenceTransactionHash] = cr
+		delete(coinDB.mainCache, cl)
+	}
+	coinDB.mainCacheSize = 0
+	// write the new records
+	for key, cr := range updatedCoinRecords {
+		if len(cr.OutputIndexes) <= 1 {
+			err := coinDB.db.Delete([]byte(key), nil)
+			if err != nil {
+				utils.Debug.Printf("[FlushMainCache] failed to delete key {%v}", key)
+			}
+		} else {
+			coinDB.putRecordInDB(key, cr)
+		}
+	}
+}
+
+// StoreBlock handles storing a newly minted Block. It:
+// (1) removes spent TransactionOutputs (if active)
+// (2) stores new TransactionOutputs as Coins in the mainCache (if active)
+// (3) stores CoinRecords for the Transactions in the db.
+func (coinDB *CoinDatabase) StoreBlock(transactions []*block.Transaction, active bool) {
+	//TODO
+}
+
+// removeCoinFromDB removes a Coin from a CoinRecord, deleting the CoinRecord
+// from the db entirely if it is the last remaining Coin in the CoinRecord.
+func (coinDB *CoinDatabase) removeCoinFromDB(txHash string, cl CoinLocator) {
+	// 3. If the coin is not in the main cache, retrieve from the database
+	// 4. Delete coin records if they only have one coin
+	// 5. Remove coins from the record
+	cr := coinDB.getCoinRecordFromDB(txHash)
+	switch {
+	case cr == nil:
+		return
+	case len(cr.Amounts) <= 1:
+		if err := coinDB.db.Delete([]byte(txHash), nil); err != nil {
+			utils.Debug.Printf("[removeCoinFromDB] failed to remove {%v} from db", txHash)
+		}
+	default:
+		cr = coinDB.removeCoinFromRecord(cr, cl.OutputIndex)
+		coinDB.putRecordInDB(txHash, cr)
+	}
+}
+
+// putRecordInDB puts a CoinRecord into the db.
+func (coinDB *CoinDatabase) putRecordInDB(txHash string, cr *CoinRecord) {
+	record := EncodeCoinRecord(cr)
+	if err2 := coinDB.db.Put([]byte(txHash), []byte(record.String()), nil); err2 != nil {
+		utils.Debug.Printf("Unable to store block record for key {%v}", txHash)
+	}
+}
+
+// removeCoinFromRecord returns an updated CoinRecord. It removes the Coin
+// with the given outputIndex, if the Coin exists in the CoinRecord.
+func (coinDB *CoinDatabase) removeCoinFromRecord(cr *CoinRecord, outputIndex uint32) *CoinRecord {
+	index := indexOf(cr.OutputIndexes, outputIndex)
+	if index < 0 {
+		return cr
+	}
+	cr.OutputIndexes = append(cr.OutputIndexes[:index], cr.OutputIndexes[index+1:]...)
+	cr.Amounts = append(cr.Amounts[:index], cr.Amounts[index+1:]...)
+	cr.LockingScripts = append(cr.LockingScripts[:index], cr.LockingScripts[index+1:]...)
+	return cr
+}
+
+// createCoinRecord returns a CoinRecord for the provided Transaction.
+func (coinDB *CoinDatabase) createCoinRecord(tx *block.Transaction) *CoinRecord {
+	var outputIndexes []uint32
+	var amounts []uint32
+	var LockingScripts []string
+	for i, txo := range tx.Outputs {
+		outputIndexes = append(outputIndexes, uint32(i))
+		amounts = append(amounts, txo.Amount)
+		LockingScripts = append(LockingScripts, txo.LockingScript)
+	}
+	cr := &CoinRecord{
+		Version:        0,
+		OutputIndexes:  outputIndexes,
+		Amounts:        amounts,
+		LockingScripts: LockingScripts,
+	}
+	return cr
+}
+
+// getCoinRecordFromDB returns a CoinRecord from the db given a hash.
+func (coinDB *CoinDatabase) getCoinRecordFromDB(txHash string) *CoinRecord {
+	if data, err := coinDB.db.Get([]byte(txHash), nil); err != nil {
+		utils.Debug.Printf("[validateTransaction] coin not in leveldb")
+		return nil
+	} else {
+		pcr := &pro.CoinRecord{}
+		if err := proto.Unmarshal(data, pcr); err != nil {
+			utils.Debug.Printf("Failed to unmarshal record from hash {%v}:", txHash, err)
+		}
+		cr := DecodeCoinRecord(pcr)
+		return cr
+	}
+}
+
+// GetCoin returns a Coin given a CoinLocator. It first checks the
+// mainCache, then checks the db. If the Coin doesn't exist, it returns nil.
+func (coinDB *CoinDatabase) GetCoin(cl CoinLocator) *Coin {
+	if coin, ok := coinDB.mainCache[cl]; ok {
+		return coin
+	}
+	cr := coinDB.getCoinRecordFromDB(cl.ReferenceTransactionHash)
+	if cr == nil {
+		return nil
+	}
+	index := indexOf(cr.OutputIndexes, cl.OutputIndex)
+	if index < 0 {
+		return nil
+	}
+	return &Coin{
+		TransactionOutput: &block.TransactionOutput{
+			Amount:        cr.Amounts[index],
+			LockingScript: cr.LockingScripts[index],
+		},
+		IsSpent: false,
+	}
+}
+
+// contains returns true if an int slice s contains element e, false if it does not.
+func contains(s []uint32, e uint32) bool {
+	for _, a := range s {
+		if a == e {
+			return true
+		}
+	}
+	return false
+}
+
+//indexOf returns the index of element e in int slice s, -1 if the element does not exist.
+func indexOf(s []uint32, e uint32) int {
+	for i, a := range s {
+		if a == e {
+			return i
+		}
+	}
+	return -1
+}
diff --git a/pkg/blockchain/coindatabase/coinrecord.go b/pkg/blockchain/coindatabase/coinrecord.go
new file mode 100644
index 0000000..6de45c3
--- /dev/null
+++ b/pkg/blockchain/coindatabase/coinrecord.go
@@ -0,0 +1,48 @@
+package coindatabase
+
+import "Chain/pkg/pro"
+
+// CoinRecord is a record of which coins created by a Transaction
+// have been spent. It is stored in the CoinDatabase's db.
+type CoinRecord struct {
+	Version        uint32
+	OutputIndexes  []uint32
+	Amounts        []uint32
+	LockingScripts []string
+}
+
+// EncodeCoinRecord returns a pro.CoinRecord given a CoinRecord.
+func EncodeCoinRecord(cr *CoinRecord) *pro.CoinRecord {
+	var outputIndexes []uint32
+	var amounts []uint32
+	var lockingScripts []string
+	for i := 0; i < len(cr.OutputIndexes); i++ {
+		outputIndexes = append(outputIndexes, cr.OutputIndexes[i])
+		amounts = append(amounts, cr.Amounts[i])
+		lockingScripts = append(lockingScripts, cr.LockingScripts[i])
+	}
+	return &pro.CoinRecord{
+		Version:        cr.Version,
+		OutputIndexes:  outputIndexes,
+		Amounts:        amounts,
+		LockingScripts: lockingScripts,
+	}
+}
+
+// DecodeCoinRecord returns a CoinRecord given a pro.CoinRecord.
+func DecodeCoinRecord(pcr *pro.CoinRecord) *CoinRecord {
+	var outputIndexes []uint32
+	var amounts []uint32
+	var lockingScripts []string
+	for i := 0; i < len(pcr.GetOutputIndexes()); i++ {
+		outputIndexes = append(outputIndexes, pcr.GetOutputIndexes()[i])
+		amounts = append(amounts, pcr.GetAmounts()[i])
+		lockingScripts = append(lockingScripts, pcr.GetLockingScripts()[i])
+	}
+	return &CoinRecord{
+		Version:        pcr.GetVersion(),
+		OutputIndexes:  outputIndexes,
+		Amounts:        amounts,
+		LockingScripts: lockingScripts,
+	}
+}
diff --git a/pkg/blockchain/coindatabase/config.go b/pkg/blockchain/coindatabase/config.go
new file mode 100644
index 0000000..bfb372b
--- /dev/null
+++ b/pkg/blockchain/coindatabase/config.go
@@ -0,0 +1,15 @@
+package coindatabase
+
+// Config is the CoinDatabase's configuration options.
+type Config struct {
+	DatabasePath      string
+	MainCacheCapacity uint32
+}
+
+// DefaultConfig returns the CoinDatabase's default Config.
+func DefaultConfig() *Config {
+	return &Config{
+		DatabasePath:      "./coindata",
+		MainCacheCapacity: 30,
+	}
+}