frontend: implement GetLatestBlock, GetBlock; refactoring

frontend/service.go

@@ -0,0 +1,78 @@
+package frontend
+
+import (
+	"context"
+	"database/sql"
+	"encoding/hex"
+	"errors"
+
+	_ "github.com/mattn/go-sqlite3"
+
+	"github.com/gtank/ctxd/rpc"
+	"github.com/gtank/ctxd/storage"
+)
+
+var (
+	ErrNoImpl      = errors.New("not yet implemented")
+	ErrUnspecified = errors.New("request for unspecified identifier")
+)
+
+// the service type
+type sqlStreamer struct {
+	db *sql.DB
+}
+
+func NewSQLiteStreamer(dbPath string) (rpc.CompactTxStreamerServer, error) {
+	db, err := sql.Open("sqlite3", dbPath)
+	if err != nil {
+		return nil, err
+	}
+
+	// Creates our tables if they don't already exist.
+	err = storage.CreateTables(db)
+	if err != nil {
+		return nil, err
+	}
+
+	return &sqlStreamer{db}, nil
+}
+
+func (s *sqlStreamer) GetLatestBlock(ctx context.Context, placeholder *rpc.ChainSpec) (*rpc.BlockID, error) {
+	// the ChainSpec type is an empty placeholder
+	height, err := storage.GetCurrentHeight(ctx, s.db)
+	if err != nil {
+		return nil, err
+	}
+	// TODO: also return block hashes here
+	return &rpc.BlockID{Height: uint64(height)}, nil
+}
+
+func (s *sqlStreamer) GetBlock(ctx context.Context, id *rpc.BlockID) (*rpc.CompactBlock, error) {
+	if id.Height == 0 && id.Hash == nil {
+		return nil, ErrUnspecified
+	}
+
+	// Precedence: a hash is more specific than a height. If we have it, use it first.
+	if id.Hash != nil {
+		leHashString := hex.EncodeToString(id.Hash)
+		return storage.GetBlockByHash(ctx, s.db, leHashString)
+	}
+
+	// we have a height and not a hash
+	if int(id.Height) > 0 {
+		return storage.GetBlock(ctx, s.db, int(id.Height))
+	}
+
+	return nil, ErrUnspecified
+}
+
+func (s *sqlStreamer) GetBlockRange(*rpc.BlockRange, rpc.CompactTxStreamer_GetBlockRangeServer) error {
+	return ErrNoImpl
+}
+
+func (s *sqlStreamer) GetTransaction(context.Context, *rpc.TxFilter) (*rpc.RawTransaction, error) {
+	return nil, ErrNoImpl
+}
+func (s *sqlStreamer) SendTransaction(context.Context, *rpc.RawTransaction) (*rpc.SendResponse, error) {
+	return nil, ErrNoImpl
+}