initial planning

database/memory.go

@@ -0,0 +1,79 @@
+package database
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"git.yetaga.in/alazyreader/library/book"
+)
+
+type Memory struct {
+	lock  sync.Mutex
+	shelf []book.Book
+}
+
+func (m *Memory) GetAllBooks(_ context.Context) ([]book.Book, error) {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	if m.shelf == nil {
+		m.shelf = []book.Book{}
+	}
+
+	return m.shelf, nil
+}
+
+func (m *Memory) AddBook(_ context.Context, b *book.Book) error {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	if m.shelf == nil {
+		m.shelf = []book.Book{}
+	}
+
+	m.shelf = append(m.shelf, *b)
+	return nil
+}
+
+func (m *Memory) UpdateBook(_ context.Context, old, new *book.Book) error {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	if m.shelf == nil {
+		m.shelf = []book.Book{}
+		return fmt.Errorf("book does not exist")
+	}
+
+	if old.ID != new.ID {
+		return fmt.Errorf("cannot change book ID")
+	}
+
+	for i := range m.shelf {
+		if m.shelf[i].ID == old.ID {
+			m.shelf[i] = *new
+			return nil
+		}
+	}
+	return fmt.Errorf("book does not exist")
+}
+
+func (m *Memory) DeleteBook(_ context.Context, b *book.Book) error {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	if m.shelf == nil {
+		m.shelf = []book.Book{}
+		return fmt.Errorf("book does not exist")
+	}
+
+	for i := range m.shelf {
+		if m.shelf[i].ID == b.ID {
+			// reorder slice to remove book quickly
+			m.shelf[i] = m.shelf[len(m.shelf)-1]
+			m.shelf = m.shelf[:len(m.shelf)-1]
+			return nil
+		}
+	}
+	return fmt.Errorf("book does not exist")
+}