walletdb

type BatchDB interface {
	DB

	// Batch is similar to the package-level Update method, but it will
	// attempt to optimistically combine the invocation of several
	// transaction functions into a single db write transaction.
	Batch(func(tx ReadWriteTx) error) error
}

type DB interface {
	// BeginReadTx opens a database read transaction.
	BeginReadTx() (ReadTx, error)

	// BeginReadWriteTx opens a database read+write transaction.
	BeginReadWriteTx() (ReadWriteTx, error)

	// Copy writes a copy of the database to the provided writer.  This
	// call will start a read-only transaction to perform all operations.
	Copy(w io.Writer) error

	// Close cleanly shuts down the database and syncs all data.
	Close() error

	// PrintStats returns all collected stats pretty printed into a string.
	PrintStats() string

	// View opens a database read transaction and executes the function f
	// with the transaction passed as a parameter. After f exits, the
	// transaction is rolled back. If f errors, its error is returned, not a
	// rollback error (if any occur). The passed reset function is called
	// before the start of the transaction and can be used to reset
	// intermediate state. As callers may expect retries of the f closure
	// (depending on the database backend used), the reset function will be
	// called before each retry respectively.
	//
	// NOTE: For new code, this method should be used directly instead of
	// the package level View() function.
	View(f func(tx ReadTx) error, reset func()) error

	// Update opens a database read/write transaction and executes the
	// function f with the transaction passed as a parameter. After f exits,
	// if f did not error, the transaction is committed. Otherwise, if f did
	// error, the transaction is rolled back. If the rollback fails, the
	// original error returned by f is still returned. If the commit fails,
	// the commit error is returned. As callers may expect retries of the f
	// closure (depending on the database backend used), the reset function
	// will be called before each retry respectively.
	//
	// NOTE: For new code, this method should be used directly instead of
	// the package level Update() function.
	Update(f func(tx ReadWriteTx) error, reset func()) error
}

type Driver struct {
	// DbType is the identifier used to uniquely identify a specific
	// database driver.  There can be only one driver with the same name.
	DbType string

	// Create is the function that will be invoked with all user-specified
	// arguments to create the database.  This function must return
	// ErrDbExists if the database already exists.
	Create func(args ...interface{}) (DB, error)

	// Open is the function that will be invoked with all user-specified
	// arguments to open the database.  This function must return
	// ErrDbDoesNotExist if the database has not already been created.
	Open func(args ...interface{}) (DB, error)
}

type ReadBucket interface {
	// NestedReadBucket retrieves a nested bucket with the given key.
	// Returns nil if the bucket does not exist.
	NestedReadBucket(key []byte) ReadBucket

	// ForEach invokes the passed function with every key/value pair in
	// the bucket.  This includes nested buckets, in which case the value
	// is nil, but it does not include the key/value pairs within those
	// nested buckets.
	//
	// NOTE: The values returned by this function are only valid during a
	// transaction.  Attempting to access them after a transaction has ended
	// results in undefined behavior.  This constraint prevents additional
	// data copies and allows support for memory-mapped database
	// implementations.
	ForEach(func(k, v []byte) error) error

	// Get returns the value for the given key.  Returns nil if the key does
	// not exist in this bucket (or nested buckets).
	//
	// NOTE: The value returned by this function is only valid during a
	// transaction.  Attempting to access it after a transaction has ended
	// results in undefined behavior.  This constraint prevents additional
	// data copies and allows support for memory-mapped database
	// implementations.
	Get(key []byte) []byte

	ReadCursor() ReadCursor
}

type ReadCursor interface {
	// First positions the cursor at the first key/value pair and returns
	// the pair.
	First() (key, value []byte)

	// Last positions the cursor at the last key/value pair and returns the
	// pair.
	Last() (key, value []byte)

	// Next moves the cursor one key/value pair forward and returns the new
	// pair.
	Next() (key, value []byte)

	// Prev moves the cursor one key/value pair backward and returns the new
	// pair.
	Prev() (key, value []byte)

	// Seek positions the cursor at the passed seek key.  If the key does
	// not exist, the cursor is moved to the next key after seek.  Returns
	// the new pair.
	Seek(seek []byte) (key, value []byte)
}

type ReadTx interface {
	// ReadBucket opens the root bucket for read only access.  If the bucket
	// described by the key does not exist, nil is returned.
	ReadBucket(key []byte) ReadBucket

	// ForEachBucket will iterate through all top level buckets.
	ForEachBucket(func(key []byte) error) error

	// Rollback closes the transaction, discarding changes (if any) if the
	// database was modified by a write transaction.
	Rollback() error
}

type ReadWriteBucket interface {
	ReadBucket

	// NestedReadWriteBucket retrieves a nested bucket with the given key.
	// Returns nil if the bucket does not exist.
	NestedReadWriteBucket(key []byte) ReadWriteBucket

	// CreateBucket creates and returns a new nested bucket with the given
	// key.  Returns ErrBucketExists if the bucket already exists,
	// ErrBucketNameRequired if the key is empty, or ErrIncompatibleValue
	// if the key value is otherwise invalid for the particular database
	// implementation.  Other errors are possible depending on the
	// implementation.
	CreateBucket(key []byte) (ReadWriteBucket, error)

	// CreateBucketIfNotExists creates and returns a new nested bucket with
	// the given key if it does not already exist.  Returns
	// ErrBucketNameRequired if the key is empty or ErrIncompatibleValue
	// if the key value is otherwise invalid for the particular database
	// backend.  Other errors are possible depending on the implementation.
	CreateBucketIfNotExists(key []byte) (ReadWriteBucket, error)

	// DeleteNestedBucket removes a nested bucket with the given key.
	// Returns ErrTxNotWritable if attempted against a read-only transaction
	// and ErrBucketNotFound if the specified bucket does not exist.
	DeleteNestedBucket(key []byte) error

	// Put saves the specified key/value pair to the bucket.  Keys that do
	// not already exist are added and keys that already exist are
	// overwritten.  Returns ErrTxNotWritable if attempted against a
	// read-only transaction.
	Put(key, value []byte) error

	// Delete removes the specified key from the bucket.  Deleting a key
	// that does not exist does not return an error.  Returns
	// ErrTxNotWritable if attempted against a read-only transaction.
	Delete(key []byte) error

	// ReadWriteCursor returns a new cursor, allowing for iteration over the
	// bucket's key/value pairs and nested buckets in forward or backward
	// order.
	ReadWriteCursor() ReadWriteCursor

	// Tx returns the bucket's transaction.
	Tx() ReadWriteTx

	// NextSequence returns an autoincrementing integer for the bucket.
	NextSequence() (uint64, error)

	// SetSequence updates the sequence number for the bucket.
	SetSequence(v uint64) error

	// Sequence returns the current integer for the bucket without
	// incrementing it.
	Sequence() uint64
}

type ReadWriteCursor interface {
	ReadCursor

	// Delete removes the current key/value pair the cursor is at without
	// invalidating the cursor.  Returns ErrIncompatibleValue if attempted
	// when the cursor points to a nested bucket.
	Delete() error
}

type ReadWriteTx interface {
	ReadTx

	// ReadWriteBucket opens the root bucket for read/write access.  If the
	// bucket described by the key does not exist, nil is returned.
	ReadWriteBucket(key []byte) ReadWriteBucket

	// CreateTopLevelBucket creates the top level bucket for a key if it
	// does not exist.  The newly-created bucket it returned.
	CreateTopLevelBucket(key []byte) (ReadWriteBucket, error)

	// DeleteTopLevelBucket deletes the top level bucket for a key.  This
	// errors if the bucket can not be found or the key keys a single value
	// instead of a bucket.
	DeleteTopLevelBucket(key []byte) error

	// Commit commits all changes that have been on the transaction's root
	// buckets and all of their sub-buckets to persistent storage.
	Commit() error

	// OnCommit takes a function closure that will be executed when the
	// transaction successfully gets committed.
	OnCommit(func())
}