email-mcp/internal/imapclient/service_test.go

package imapclient

import (
	"context"
	"errors"
	"testing"

	"email-mcp/internal/secretstore"
)

type backendStub struct {
	listMailboxes func(context.Context, secretstore.Credential) ([]Mailbox, error)
	listMessages  func(context.Context, secretstore.Credential, string, int) ([]MessageSummary, error)
	getMessage    func(context.Context, secretstore.Credential, string, uint32) (Message, error)
}

func (b backendStub) ListMailboxes(ctx context.Context, cred secretstore.Credential) ([]Mailbox, error) {
	return b.listMailboxes(ctx, cred)
}

func (b backendStub) ListMessages(ctx context.Context, cred secretstore.Credential, mailbox string, limit int) ([]MessageSummary, error) {
	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{
		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",
		Username: "alice",
		Password: "secret",
	})
	if err != nil {
		t.Fatalf("ListMailboxes returned error: %v", err)
	}
	if len(boxes) != 1 || boxes[0].Name != "INBOX" {
		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)
			}
		})
	}
}