implemented persistence

internal/state.go

@@ -0,0 +1,46 @@
+package internal
+
+import (
+	"context"
+
+	"github.com/shopspring/decimal"
+)
+
+// StateVersion is the schema version of the persisted State struct.
+const StateVersion = "1"
+
+// State is the platform-agnostic representation of the buy-queue state that is
+// written to disk after a successful run and reloaded on the next run.
+type State struct {
+	Version  string                       `json:"version"`
+	Platform string                       `json:"platform"`
+	Queues   map[string][]persistedFiller `json:"queues"`
+}
+
+// persistedFiller is the on-disk representation of a single Filler. The
+// Record-specific data is kept as opaque bytes so the internal package does
+// not need to know about any broker package's concrete Record type.
+type persistedFiller struct {
+	ReaderData []byte          `json:"reader_data"`
+	Quantity   decimal.Decimal `json:"quantity"`
+	Price      decimal.Decimal `json:"price"`
+	Filled     decimal.Decimal `json:"filled"`
+}
+
+// RecordEncoder encodes a Record into its broker-specific byte representation.
+type RecordEncoder interface {
+	MarshalRecord(context.Context, Record) ([]byte, error)
+}
+
+// RecordDecoder decodes broker-specific bytes back into a Record.
+type RecordDecoder interface {
+	UnmarshalRecord(context.Context, []byte) (Record, error)
+}
+
+// RecordSerializer composes encoding and decoding of Records. Broker packages
+// own the implementation so that lazy/closured Record fields can be re-wired
+// on load.
+type RecordSerializer interface {
+	RecordEncoder
+	RecordDecoder
+}