fix: tighten imap service message contract

internal/imapclient/service.go

@@ -22,6 +22,6 @@ func (s Service) ListMessages(ctx context.Context, cred secretstore.Credential,
 	return s.backend.ListMessages(ctx, cred, mailbox, limit)
 }
 
-func (s Service) GetMessage(ctx context.Context, cred secretstore.Credential, mailbox string, id string) (Message, error) {
+func (s Service) GetMessage(ctx context.Context, cred secretstore.Credential, mailbox string, uid uint32) (Message, error) {
-	return s.backend.GetMessage(ctx, cred, mailbox, id)
+	return s.backend.GetMessage(ctx, cred, mailbox, uid)
 }

internal/imapclient/service_test.go

@@ -2,27 +2,47 @@ package imapclient
 
 import (
 	"context"
+	"errors"
 	"testing"
 
 	"email-mcp/internal/secretstore"
 )
 
-type backendStub struct{}
+type backendStub struct {
-
+	listMailboxes func(context.Context, secretstore.Credential) ([]Mailbox, error)
-func (backendStub) ListMailboxes(context.Context, secretstore.Credential) ([]Mailbox, error) {
+	listMessages  func(context.Context, secretstore.Credential, string, int) ([]MessageSummary, error)
-	return []Mailbox{{Name: "INBOX"}}, nil
+	getMessage    func(context.Context, secretstore.Credential, string, uint32) (Message, error)
 }
 
-func (backendStub) ListMessages(context.Context, secretstore.Credential, string, int) ([]MessageSummary, error) {
+func (b backendStub) ListMailboxes(ctx context.Context, cred secretstore.Credential) ([]Mailbox, error) {
-	return nil, nil
+	return b.listMailboxes(ctx, cred)
 }
 
-func (backendStub) GetMessage(context.Context, secretstore.Credential, string, string) (Message, error) {
+func (b backendStub) ListMessages(ctx context.Context, cred secretstore.Credential, mailbox string, limit int) ([]MessageSummary, error) {
-	return Message{}, nil
+	return b.listMessages(ctx, cred, mailbox, limit)
+}
+
+func (b backendStub) GetMessage(ctx context.Context, cred secretstore.Credential, mailbox string, uid uint32) (Message, error) {
+	return b.getMessage(ctx, cred, mailbox, uid)
 }
 
 func TestServiceListMailboxesUsesBackend(t *testing.T) {
-	svc := NewService(backendStub{})
+	svc := NewService(backendStub{
+		listMailboxes: func(_ context.Context, cred secretstore.Credential) ([]Mailbox, error) {
+			if cred.Host != "imap.example.com" || cred.Username != "alice" || cred.Password != "secret" {
+				t.Fatalf("unexpected credential: %#v", cred)
+			}
+			return []Mailbox{{Name: "INBOX"}}, nil
+		},
+		listMessages: func(context.Context, secretstore.Credential, string, int) ([]MessageSummary, error) {
+			t.Fatal("ListMessages should not be called")
+			return nil, nil
+		},
+		getMessage: func(context.Context, secretstore.Credential, string, uint32) (Message, error) {
+			t.Fatal("GetMessage should not be called")
+			return Message{}, nil
+		},
+	})
 
 	boxes, err := svc.ListMailboxes(context.Background(), secretstore.Credential{
 		Host:     "imap.example.com",
@@ -36,3 +56,138 @@ func TestServiceListMailboxesUsesBackend(t *testing.T) {
 		t.Fatalf("unexpected mailboxes: %#v", boxes)
 	}
 }
+
+func TestServiceListMessagesUsesBackend(t *testing.T) {
+	svc := NewService(backendStub{
+		listMailboxes: func(context.Context, secretstore.Credential) ([]Mailbox, error) {
+			t.Fatal("ListMailboxes should not be called")
+			return nil, nil
+		},
+		listMessages: func(_ context.Context, cred secretstore.Credential, mailbox string, limit int) ([]MessageSummary, error) {
+			if cred.Host != "imap.example.com" || mailbox != "INBOX" || limit != 10 {
+				t.Fatalf("unexpected call: cred=%#v mailbox=%q limit=%d", cred, mailbox, limit)
+			}
+			return []MessageSummary{{
+				UID:     42,
+				Subject: "hello",
+				From:    "alice@example.com",
+			}}, nil
+		},
+		getMessage: func(context.Context, secretstore.Credential, string, uint32) (Message, error) {
+			t.Fatal("GetMessage should not be called")
+			return Message{}, nil
+		},
+	})
+
+	messages, err := svc.ListMessages(context.Background(), secretstore.Credential{
+		Host:     "imap.example.com",
+		Username: "alice",
+		Password: "secret",
+	}, "INBOX", 10)
+	if err != nil {
+		t.Fatalf("ListMessages returned error: %v", err)
+	}
+	if len(messages) != 1 || messages[0].UID != 42 {
+		t.Fatalf("unexpected messages: %#v", messages)
+	}
+}
+
+func TestServiceGetMessageUsesBackend(t *testing.T) {
+	svc := NewService(backendStub{
+		listMailboxes: func(context.Context, secretstore.Credential) ([]Mailbox, error) {
+			t.Fatal("ListMailboxes should not be called")
+			return nil, nil
+		},
+		listMessages: func(context.Context, secretstore.Credential, string, int) ([]MessageSummary, error) {
+			t.Fatal("ListMessages should not be called")
+			return nil, nil
+		},
+		getMessage: func(_ context.Context, cred secretstore.Credential, mailbox string, uid uint32) (Message, error) {
+			if cred.Host != "imap.example.com" || mailbox != "INBOX" || uid != 42 {
+				t.Fatalf("unexpected call: cred=%#v mailbox=%q uid=%d", cred, mailbox, uid)
+			}
+			return Message{
+				UID:     42,
+				Mailbox: "INBOX",
+				Headers: []Header{
+					{Name: "Received", Value: "first"},
+					{Name: "Received", Value: "second"},
+					{Name: "Subject", Value: "hello"},
+				},
+				Body: "body",
+			}, nil
+		},
+	})
+
+	message, err := svc.GetMessage(context.Background(), secretstore.Credential{
+		Host:     "imap.example.com",
+		Username: "alice",
+		Password: "secret",
+	}, "INBOX", 42)
+	if err != nil {
+		t.Fatalf("GetMessage returned error: %v", err)
+	}
+	if message.UID != 42 {
+		t.Fatalf("unexpected message UID: %#v", message)
+	}
+	if len(message.Headers) != 3 {
+		t.Fatalf("unexpected headers: %#v", message.Headers)
+	}
+	if message.Headers[0].Name != "Received" || message.Headers[0].Value != "first" {
+		t.Fatalf("unexpected first header: %#v", message.Headers[0])
+	}
+	if message.Headers[1].Name != "Received" || message.Headers[1].Value != "second" {
+		t.Fatalf("unexpected second header: %#v", message.Headers[1])
+	}
+}
+
+func TestServicePropagatesBackendErrors(t *testing.T) {
+	wantErr := errors.New("backend failed")
+
+	tests := []struct {
+		name string
+		run  func(Service) error
+	}{
+		{
+			name: "ListMailboxes",
+			run: func(svc Service) error {
+				_, err := svc.ListMailboxes(context.Background(), secretstore.Credential{})
+				return err
+			},
+		},
+		{
+			name: "ListMessages",
+			run: func(svc Service) error {
+				_, err := svc.ListMessages(context.Background(), secretstore.Credential{}, "INBOX", 10)
+				return err
+			},
+		},
+		{
+			name: "GetMessage",
+			run: func(svc Service) error {
+				_, err := svc.GetMessage(context.Background(), secretstore.Credential{}, "INBOX", 42)
+				return err
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			svc := NewService(backendStub{
+				listMailboxes: func(context.Context, secretstore.Credential) ([]Mailbox, error) {
+					return nil, wantErr
+				},
+				listMessages: func(context.Context, secretstore.Credential, string, int) ([]MessageSummary, error) {
+					return nil, wantErr
+				},
+				getMessage: func(context.Context, secretstore.Credential, string, uint32) (Message, error) {
+					return Message{}, wantErr
+				},
+			})
+
+			if err := tc.run(svc); !errors.Is(err, wantErr) {
+				t.Fatalf("expected error %v, got %v", wantErr, err)
+			}
+		})
+	}
+}

internal/imapclient/types.go

@@ -11,21 +11,25 @@ type Mailbox struct {
 }
 
 type MessageSummary struct {
-	ID      string `json:"id"`
+	UID     uint32 `json:"uid"`
 	Subject string `json:"subject"`
 	From    string `json:"from"`
-	UID     uint32 `json:"uid"`
+}
+
+type Header struct {
+	Name  string `json:"name"`
+	Value string `json:"value"`
 }
 
 type Message struct {
-	ID      string            `json:"id"`
+	UID     uint32   `json:"uid"`
-	Mailbox string            `json:"mailbox"`
+	Mailbox string   `json:"mailbox"`
-	Headers map[string]string `json:"headers"`
+	Headers []Header `json:"headers"`
-	Body    string            `json:"body"`
+	Body    string   `json:"body"`
 }
 
 type Backend interface {
 	ListMailboxes(context.Context, secretstore.Credential) ([]Mailbox, error)
 	ListMessages(context.Context, secretstore.Credential, string, int) ([]MessageSummary, error)
-	GetMessage(context.Context, secretstore.Credential, string, string) (Message, error)
+	GetMessage(context.Context, secretstore.Credential, string, uint32) (Message, error)
 }