Add todo service layer

Author: MarkMoudy

README.md

@@ -1 +1,3 @@
 # go-todo
+
+This repo contains a basic Todo application and is mostly to provide a Go coding sample.

go.mod

@@ -0,0 +1,5 @@
+module github.com/MarkMoudy/go-todo
+
+go 1.15
+
+require github.com/google/go-cmp v0.5.5

go.sum

@@ -0,0 +1,3 @@
+github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
+github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

todo/service.go

@@ -0,0 +1,137 @@
+// package todo provides an API to store and manage Todos.
+package todo
+
+import (
+	"context"
+	"errors"
+	"sort"
+	"sync"
+)
+
+type Service interface {
+	// Todo fetches a single Todo using the given 'id'.
+	Todo(ctx context.Context, id int) (Todo, error)
+
+	// Todos fetches all Todos.
+	Todos(ctx context.Context) ([]Todo, error)
+
+	// CreateTodo creates a new Todo with the given 'description'. All new Todo
+	// items are initially marked as incomplete.
+	CreateTodo(ctx context.Context, description string) error
+
+	// UpdateTodo modifies an existing Todo.
+	UpdateTodo(ctx context.Context, id int, desc string) error
+
+	// SetCompletedStatus sets a Todo item's completed status.
+	SetCompletedStatus(ctx context.Context, id int, completed bool) error
+}
+
+// Todo represents a Todo task.
+type Todo struct {
+	ID          int
+	Description string
+	Completed   bool
+}
+
+type inmemService struct {
+	nextID int
+
+	todos map[int]Todo
+	mu    sync.Mutex
+}
+
+// NewInmemService returns an in memory implementation of Service.
+func NewInmemService() Service {
+	return &inmemService{
+		nextID: 1,
+		todos:  make(map[int]Todo),
+	}
+}
+
+// Errors returned by Service.
+var (
+	ErrInvalidID    = errors.New("invalid id, must be non-negative")
+	ErrTodoNotFound = errors.New("todo not found")
+)
+
+// Todo implements Service.
+func (s *inmemService) Todo(ctx context.Context, id int) (Todo, error) {
+	if id < 0 {
+		return Todo{}, ErrInvalidID
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if todo, ok := s.todos[id]; ok {
+		return todo, nil
+	}
+
+	return Todo{}, nil
+}
+
+// Todos implements Service.
+func (s *inmemService) Todos(ctx context.Context) ([]Todo, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	var todos []Todo
+	for _, v := range s.todos {
+		todos = append(todos, v)
+	}
+
+	sort.Slice(todos, func(i, j int) bool {
+		return todos[i].ID < todos[j].ID
+	})
+	return todos, nil
+}
+
+// CreateTodo implements Service.
+func (s *inmemService) CreateTodo(ctx context.Context, desc string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	todo := Todo{
+		ID:          s.generateID(),
+		Description: desc,
+	}
+
+	s.todos[todo.ID] = todo
+	return nil
+}
+
+func (s *inmemService) generateID() int {
+	defer func() { s.nextID++ }()
+	return s.nextID
+}
+
+// UpdateTodo implements Service.
+func (s *inmemService) UpdateTodo(ctx context.Context, id int, desc string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	todo, ok := s.todos[id]
+	if !ok {
+		return ErrTodoNotFound
+	}
+
+	todo.Description = desc
+	s.todos[id] = todo
+
+	return nil
+}
+
+// SetCompletedStatus implements Service.
+func (s *inmemService) SetCompletedStatus(ctx context.Context, id int, completed bool) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	todo, ok := s.todos[id]
+	if !ok {
+		return ErrTodoNotFound
+	}
+
+	todo.Completed = completed
+
+	s.todos[id] = todo
+
+	return nil
+}

todo/service_test.go

@@ -0,0 +1,188 @@
+package todo
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestTodo(t *testing.T) {
+	testcases := []struct {
+		name     string
+		todos    []Todo
+		id       int
+		wantTodo Todo
+		errMatch error
+	}{
+		{
+			name: "successful-lookup",
+			todos: []Todo{
+				{
+					Description: "do this task",
+				},
+			},
+			id: 1,
+			wantTodo: Todo{
+				ID:          1,
+				Description: "do this task",
+			},
+		},
+		{
+			name:     "invalid-id",
+			id:       -1,
+			errMatch: ErrInvalidID,
+		},
+	}
+
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			svc := NewInmemService()
+			ctx := context.Background()
+
+			for _, v := range tc.todos {
+				if err := svc.CreateTodo(ctx, v.Description); err != nil {
+					t.Fatalf("unexpected error creating initial set of Todo data %v", err)
+				}
+			}
+
+			gotTodo, gotErr := svc.Todo(ctx, tc.id)
+
+			if !errors.Is(gotErr, tc.errMatch) {
+				t.Fatalf("unexpected error got %v, want %v", gotErr, tc.errMatch)
+			}
+
+			if got, want := gotTodo, tc.wantTodo; got != want {
+				t.Errorf("unexpected Todo returned got %+v, want %+v", got, want)
+			}
+
+		})
+	}
+}
+
+func TestTodos(t *testing.T) {
+	testcases := []struct {
+		name      string
+		todos     []Todo
+		wantTodos []Todo
+	}{
+		{
+			name: "no-items",
+		},
+		{
+			name: "single-item",
+			todos: []Todo{
+				{
+					Description: "desc 1",
+				},
+			},
+			wantTodos: []Todo{
+				{
+					ID:          1,
+					Description: "desc 1",
+				},
+			},
+		},
+		{
+			name: "multiple-items",
+			todos: []Todo{
+				{
+					Description: "desc 1",
+				},
+				{
+					Description: "desc 2",
+				},
+				{
+					Description: "desc 3",
+				},
+			},
+			wantTodos: []Todo{
+				{
+					ID:          1,
+					Description: "desc 1",
+				},
+				{
+					ID:          2,
+					Description: "desc 2",
+				},
+				{
+					ID:          3,
+					Description: "desc 3",
+				},
+			},
+		},
+	}
+
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			svc := NewInmemService()
+			ctx := context.Background()
+
+			for _, v := range tc.todos {
+				if err := svc.CreateTodo(ctx, v.Description); err != nil {
+					t.Fatalf("unexpected error inserting todo data %v", err)
+				}
+			}
+
+			gotTodos, err := svc.Todos(ctx)
+			if err != nil {
+				t.Fatalf("unexpected error fetching Todos %v", err)
+			}
+
+			if got, want := gotTodos, tc.wantTodos; !cmp.Equal(got, want) {
+				t.Errorf("unexpected todos returned (got: -, want: +) %v", cmp.Diff(got, want))
+			}
+		})
+	}
+}
+
+func TestUpdateTodo(t *testing.T) {
+	testcases := []struct {
+		name     string
+		todo     Todo
+		desc     string
+		wantTodo Todo
+		errMatch error
+	}{
+		{
+			name: "successful-update",
+			todo: Todo{
+				Description: "foo desc",
+			},
+			desc: "bar desc",
+			wantTodo: Todo{
+				ID:          1,
+				Description: "bar desc",
+			},
+		},
+		{
+			name:     "todo-not-found",
+			errMatch: ErrTodoNotFound,
+		},
+	}
+
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			svc := NewInmemService()
+			ctx := context.Background()
+
+			if err := svc.CreateTodo(ctx, tc.todo.Description); err != nil {
+				t.Fatalf("unexpected error creating initial Todo %v", err)
+			}
+
+			if err := svc.UpdateTodo(ctx, tc.wantTodo.ID, tc.desc); !errors.Is(tc.errMatch, err) {
+				t.Fatalf("unexpected error got %v, want %v", err, tc.errMatch)
+			}
+
+			gotTodo, err := svc.Todo(ctx, tc.wantTodo.ID)
+			if err != nil {
+				t.Fatalf("unexpected error fetching updated Todo %v", err)
+			}
+
+			if got, want := gotTodo, tc.wantTodo; !cmp.Equal(got, want) {
+				t.Errorf("unexpected Todo returned (got: -, want: +) %v", cmp.Diff(got, want))
+			}
+		})
+	}
+}