2 files changed, 208 insertions, 0 deletions
diff --git a/src/post/asset/asset.go b/src/post/asset/asset.go
new file mode 100644
index 0000000..d20b347
--- /dev/null
+++ b/src/post/asset/asset.go
@@ -0,0 +1,116 @@
+package asset
+
+import (
+	"bytes"
+	"database/sql"
+	"errors"
+	"fmt"
+	"io"
+
+	"github.com/mediocregopher/blog.mediocregopher.com/srv/post"
+)
+
+var (
+	// ErrNotFound is used to indicate an Asset could not be found in the
+	// Store.
+	ErrNotFound = errors.New("asset not found")
+)
+
+// Store implements the storage and retrieval of binary assets, which are
+// intended to be used by posts (e.g. images).
+type Store interface {
+
+	// Set sets the id to the contents of the given io.Reader.
+	Set(id string, from io.Reader) error
+
+	// Get writes the id's body to the given io.Writer, or returns
+	// ErrNotFound.
+	Get(id string, into io.Writer) error
+
+	// Delete's the body stored for the id, if any.
+	Delete(id string) error
+
+	// List returns all ids which are currently stored.
+	List() ([]string, error)
+}
+
+type store struct {
+	db *post.SQLDB
+}
+
+// NewStore initializes a new Store using an existing SQLDB.
+func NewStore(db *post.SQLDB) Store {
+	return &store{
+		db: db,
+	}
+}
+
+func (s *store) Set(id string, from io.Reader) error {
+
+	body, err := io.ReadAll(from)
+	if err != nil {
+		return fmt.Errorf("reading body fully into memory: %w", err)
+	}
+
+	_, err = s.db.Exec(
+		`INSERT INTO assets (id, body)
+		VALUES (?, ?)
+		ON CONFLICT (id) DO UPDATE SET body=excluded.body`,
+		id, body,
+	)
+
+	if err != nil {
+		return fmt.Errorf("inserting into assets: %w", err)
+	}
+
+	return nil
+}
+
+func (s *store) Get(id string, into io.Writer) error {
+
+	var body []byte
+
+	err := s.db.QueryRow(`SELECT body FROM assets WHERE id = ?`, id).Scan(&body)
+
+	if errors.Is(err, sql.ErrNoRows) {
+		return ErrNotFound
+	} else if err != nil {
+		return fmt.Errorf("selecting from assets: %w", err)
+	}
+
+	if _, err := io.Copy(into, bytes.NewReader(body)); err != nil {
+		return fmt.Errorf("writing body to io.Writer: %w", err)
+	}
+
+	return nil
+}
+
+func (s *store) Delete(id string) error {
+	_, err := s.db.Exec(`DELETE FROM assets WHERE id = ?`, id)
+	return err
+}
+
+func (s *store) List() ([]string, error) {
+
+	rows, err := s.db.Query(`SELECT id FROM assets ORDER BY id ASC`)
+
+	if err != nil {
+		return nil, fmt.Errorf("querying: %w", err)
+	}
+
+	defer rows.Close()
+
+	var ids []string
+
+	for rows.Next() {
+
+		var id string
+		if err := rows.Scan(&id); err != nil {
+			return nil, fmt.Errorf("scanning row: %w", err)
+		}
+
+		ids = append(ids, id)
+	}
+
+	return ids, nil
+}
diff --git a/src/post/asset/asset_test.go b/src/post/asset/asset_test.go
new file mode 100644
index 0000000..574cc08
--- /dev/null
+++ b/src/post/asset/asset_test.go
@@ -0,0 +1,92 @@
+package asset
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"github.com/mediocregopher/blog.mediocregopher.com/srv/post"
+	"github.com/stretchr/testify/assert"
+)
+
+type testHarness struct {
+	store Store
+}
+
+func newTestHarness(t *testing.T) *testHarness {
+
+	db := post.NewInMemSQLDB()
+	t.Cleanup(func() { db.Close() })
+
+	store := NewStore(db)
+
+	return &testHarness{
+		store: store,
+	}
+}
+
+func (h *testHarness) assertGet(t *testing.T, exp, id string) {
+	t.Helper()
+	buf := new(bytes.Buffer)
+	err := h.store.Get(id, buf)
+	assert.NoError(t, err)
+	assert.Equal(t, exp, buf.String())
+}
+
+func (h *testHarness) assertNotFound(t *testing.T, id string) {
+	t.Helper()
+	err := h.store.Get(id, io.Discard)
+	assert.ErrorIs(t, ErrNotFound, err)
+}
+
+func TestStore(t *testing.T) {
+
+	testStore := func(t *testing.T, h *testHarness) {
+		t.Helper()
+
+		h.assertNotFound(t, "foo")
+		h.assertNotFound(t, "bar")
+
+		err := h.store.Set("foo", bytes.NewBufferString("FOO"))
+		assert.NoError(t, err)
+
+		h.assertGet(t, "FOO", "foo")
+		h.assertNotFound(t, "bar")
+
+		err = h.store.Set("foo", bytes.NewBufferString("FOOFOO"))
+		assert.NoError(t, err)
+
+		h.assertGet(t, "FOOFOO", "foo")
+		h.assertNotFound(t, "bar")
+
+		assert.NoError(t, h.store.Delete("foo"))
+		h.assertNotFound(t, "foo")
+		h.assertNotFound(t, "bar")
+
+		assert.NoError(t, h.store.Delete("bar"))
+		h.assertNotFound(t, "foo")
+		h.assertNotFound(t, "bar")
+
+		// test list
+
+		ids, err := h.store.List()
+		assert.NoError(t, err)
+		assert.Empty(t, ids)
+
+		err = h.store.Set("foo", bytes.NewBufferString("FOOFOO"))
+		assert.NoError(t, err)
+		err = h.store.Set("foo", bytes.NewBufferString("FOOFOO"))
+		assert.NoError(t, err)
+		err = h.store.Set("bar", bytes.NewBufferString("FOOFOO"))
+		assert.NoError(t, err)
+
+		ids, err = h.store.List()
+		assert.NoError(t, err)
+		assert.Equal(t, []string{"bar", "foo"}, ids)
+	}
+
+	t.Run("sql", func(t *testing.T) {
+		h := newTestHarness(t)
+		testStore(t, h)
+	})
+}