init

db.go

@@ -0,0 +1,24 @@
+package outbox
+
+import (
+	"context"
+	"database/sql"
+	_ "embed"
+	"errors"
+)
+
+var (
+	ErrMigrate = errors.New("error creating outbox table")
+)
+
+//go:embed init_db.sql
+var initStatement string
+
+func initDB(ctx context.Context, db *sql.DB) error {
+	_, err := db.ExecContext(ctx, initStatement)
+	if err != nil {
+		return errors.Join(ErrMigrate, err)
+	}
+
+	return nil
+}

go.mod

@@ -0,0 +1,5 @@
+module code.uint32.ru/tiny/outbox
+
+go 1.24.1
+
+require github.com/mattn/go-sqlite3 v1.14.28 // indirect

go.sum

@@ -0,0 +1,2 @@
+github.com/mattn/go-sqlite3 v1.14.28 h1:ThEiQrnbtumT+QMknw63Befp/ce/nUPgBPMlRFEum7A=
+github.com/mattn/go-sqlite3 v1.14.28/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=

init_db.sql

@@ -0,0 +1,6 @@
+CREATE TABLE IF NOT EXISTS outbox (
+    id text PRIMARY KEY, 
+    created_at timestamp with time zone default now, 
+    is_processed boolean default false, 
+    payload jsonb
+)

outbox.go

@@ -0,0 +1,103 @@
+package outbox
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"time"
+)
+
+var (
+	ErrMarshal       = errors.New("error marshaling value")
+	ErrInsert        = errors.New("error inserting value")
+	ErrSelectPending = errors.New("error selecting pending objects")
+	ErrUpdate        = errors.New("error updating object")
+	ErrCleanup       = errors.New("error deleting processed items")
+)
+
+type Box[T any] interface {
+	Save(ctx context.Context, id string, v *T) error
+	MarkProcessed(ctx context.Context, id string) error
+	GetPending(ctx context.Context, n int) ([]*T, error)
+}
+
+func OpenOrCreate[T any](ctx context.Context, db *sql.DB) (*Outbox[T], error) {
+	if err := initDB(ctx, db); err != nil {
+		return nil, err
+	}
+
+	return &Outbox[T]{
+		db: db,
+	}, nil
+}
+
+type Outbox[T any] struct {
+	db *sql.DB
+}
+
+func (o *Outbox[T]) Save(ctx context.Context, id string, v *T) error {
+	now := time.Now()
+
+	b, err := json.Marshal(v)
+	if err != nil {
+		return errors.Join(ErrMarshal, err)
+	}
+
+	stmt := "INSERT INTO outbox (id, created_at, is_processed, payload) VALUES ($1, $2, $3, $4)"
+
+	if _, err := o.db.ExecContext(ctx, stmt, id, now, false, b); err != nil {
+		return errors.Join(ErrInsert, err)
+	}
+
+	return nil
+}
+
+func (o *Outbox[T]) MarkProcessed(ctx context.Context, id string) error {
+	stmt := "UPDATE outbox SET is_processed = true WHERE id = $1"
+
+	if _, err := o.db.ExecContext(ctx, stmt, id); err != nil {
+		return errors.Join(ErrUpdate, err)
+	}
+
+	return nil
+}
+
+func (o *Outbox[T]) GetPending(ctx context.Context, n int) ([]*T, error) {
+	stmt := "SELECT payload FROM outbox WHERE is_processed = false order by created_at desc limit $1"
+
+	rows, err := o.db.QueryContext(ctx, stmt, n)
+	if err != nil {
+		return nil, errors.Join(ErrSelectPending, err)
+	}
+
+	defer rows.Close()
+
+	out := make([]*T, 0)
+
+	for rows.Next() {
+		b := []byte{}
+		if err := rows.Scan(&b); err != nil {
+			return nil, err
+		}
+
+		v := new(T)
+		if err := json.Unmarshal(b, v); err != nil {
+			return nil, err
+		}
+
+		out = append(out, v)
+	}
+
+	return out, nil
+}
+
+func (o *Outbox[T]) Cleanup(ctx context.Context) error {
+	stmt := "DELETE FROM outbox WHERE is_processed = true"
+
+	if _, err := o.db.ExecContext(ctx, stmt); err != nil {
+		return errors.Join(ErrCleanup, err)
+	}
+
+	return nil
+}

outbox_test.go

@@ -0,0 +1,69 @@
+package outbox_test
+
+import (
+	"context"
+	"database/sql"
+	"os"
+	"testing"
+
+	_ "github.com/mattn/go-sqlite3"
+
+	"code.uint32.ru/tiny/outbox"
+)
+
+type My struct {
+	A string
+	B int
+}
+
+func TestOutboxMethods(t *testing.T) {
+	db, err := sql.Open("sqlite3", "test.db")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer os.Remove("test.db")
+	defer db.Close()
+
+	ctx := context.Background()
+
+	box, err := outbox.OpenOrCreate[My](ctx, db)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	one := My{
+		A: "hello",
+		B: 42,
+	}
+
+	if err := box.Save(ctx, "test", &one); err != nil {
+		t.Fatal(err)
+	}
+
+	lst, err := box.GetPending(ctx, 100)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(lst) != 1 {
+		t.Fatal("incorrect pending len")
+	}
+
+	if err := box.MarkProcessed(ctx, "test"); err != nil {
+		t.Fatal(err)
+	}
+
+	lst, err = box.GetPending(ctx, 100)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(lst) != 0 {
+		t.Fatal("should be zero pending")
+	}
+
+	if err := box.Cleanup(ctx); err != nil {
+		t.Fatal(err)
+	}
+}