gochat/internal/channel/email/provider.go

package email

// EmailProvider implements channel.ChannelProvider + channel.PollingProvider for Email (IMAP+SMTP).
// Reference: Chatwoot app/models/channel/email.rb + ChannelEmail lifecycle hooks
//
// Email channel lifecycle:
//   - OnCreate: validate IMAP+SMTP connections, set forward_to_address
//   - Incoming (IMAP): PollMessages → FetchIMAPMessages → IncomingProcessor.Process
//   - Incoming (Webhook): HandleWebhookRequest → ParseWebhookBody → IncomingProcessor.Process
//   - Outgoing: SendMessage → SendViaSMTP
//   - OnDestroy: no cleanup needed (IMAP/SMTP connections are per-session)
//
// Design notes:
//   - Email is a PollingProvider (IMAP polling) as well as a ChannelProvider (webhook relay)
//   - The two incoming paths (IMAP poll + webhook relay) converge at IncomingProcessor
//   - SMTPSender handles outbound delivery; IMAPListener handles inbound polling
//   - forward_to_address is auto-generated for ActionMailbox-style email relay

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

	channelpkg "github.com/gochat/gochat/internal/channel"
	"github.com/gochat/gochat/internal/model"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// EmailProvider implements ChannelProvider and PollingProvider for Email.
type EmailProvider struct {
	service  *Service
	repo     *Repository
	pipeline *IncomingProcessor
}

// NewEmailProvider creates an Email channel provider with all dependencies.
func NewEmailProvider(service *Service, repo *Repository, pipeline *IncomingProcessor) *EmailProvider {
	return &EmailProvider{
		service:  service,
		repo:     repo,
		pipeline: pipeline,
	}
}

// === Channel Identity ===

func (p *EmailProvider) Type() channelpkg.ChannelType { return channelpkg.ChannelEmail }
func (p *EmailProvider) Name() string                 { return "Email" }
func (p *EmailProvider) Description() string {
	return "Email channel (IMAP + SMTP)"
}

// === Configuration ===

func (p *EmailProvider) ConfigSchema() *channelpkg.ConfigSchemaDefinition {
	return &channelpkg.ConfigSchemaDefinition{
		Type: "object",
		Properties: map[string]channelpkg.ConfigProperty{
			"imap_address": {
				Type:        "string",
				Description: "IMAP server hostname (e.g. imap.gmail.com)",
				Required:    true,
			},
			"imap_port": {
				Type:        "number",
				Description: "IMAP server port (typically 993 for SSL)",
				Default:     993,
				Required:    true,
			},
			"imap_email": {
				Type:        "string",
				Description: "IMAP login email address",
				Format:      "email",
				Required:    true,
			},
			"imap_password": {
				Type:        "string",
				Description: "IMAP password for authentication",
				Required:    true,
				Secret:      true,
			},
			"imap_ssl": {
				Type:        "boolean",
				Description: "Whether to use SSL for IMAP connection",
				Default:     true,
				Required:    false,
			},
			"smtp_address": {
				Type:        "string",
				Description: "SMTP server hostname (e.g. smtp.gmail.com)",
				Required:    true,
			},
			"smtp_port": {
				Type:        "number",
				Description: "SMTP server port (typically 587 for TLS or 465 for SSL)",
				Default:     587,
				Required:    true,
			},
			"smtp_email": {
				Type:        "string",
				Description: "SMTP login email address",
				Format:      "email",
				Required:    true,
			},
			"smtp_password": {
				Type:        "string",
				Description: "SMTP password for authentication",
				Required:    true,
				Secret:      true,
			},
			"smtp_ssl": {
				Type:        "boolean",
				Description: "Whether to use SSL/TLS for SMTP connection",
				Default:     true,
				Required:    false,
			},
		},
		Required: []string{
			"imap_address", "imap_port", "imap_email", "imap_password",
			"smtp_address", "smtp_port", "smtp_email", "smtp_password",
		},
	}
}

func (p *EmailProvider) ValidateConfig(ctx context.Context, config channelpkg.ChannelConfig) error {
	imapAddress, _ := config["imap_address"].(string)
	imapPort := configInt(config, "imap_port", 0)
	imapEmail, _ := config["imap_email"].(string)
	imapPassword, _ := config["imap_password"].(string)

	smtpAddress, _ := config["smtp_address"].(string)
	smtpPort := configInt(config, "smtp_port", 0)
	smtpEmail, _ := config["smtp_email"].(string)
	smtpPassword, _ := config["smtp_password"].(string)

	if imapAddress == "" {
		return fmt.Errorf("imap_address is required")
	}
	if imapPort == 0 {
		return fmt.Errorf("imap_port is required")
	}
	if imapEmail == "" {
		return fmt.Errorf("imap_email is required")
	}
	if imapPassword == "" {
		return fmt.Errorf("imap_password is required")
	}
	if smtpAddress == "" {
		return fmt.Errorf("smtp_address is required")
	}
	if smtpPort == 0 {
		return fmt.Errorf("smtp_port is required")
	}
	if smtpEmail == "" {
		return fmt.Errorf("smtp_email is required")
	}
	if smtpPassword == "" {
		return fmt.Errorf("smtp_password is required")
	}

	return nil
}

func (p *EmailProvider) DefaultConfig() channelpkg.ChannelConfig {
	return channelpkg.ChannelConfig{
		"imap_address":  "",
		"imap_port":     993,
		"imap_email":    "",
		"imap_password": "",
		"imap_ssl":      true,
		"smtp_address":  "",
		"smtp_port":     587,
		"smtp_email":    "",
		"smtp_password": "",
		"smtp_ssl":      true,
	}
}

// === Lifecycle Hooks ===

// OnCreate validates IMAP+SMTP connections and sets forward_to_address.
// Reference: Chatwoot's before_create :ensure_imap_connection + :ensure_smtp_connection + :ensure_forward_to_address
func (p *EmailProvider) OnCreate(ctx context.Context, inbox *model.Inbox, config channelpkg.ChannelConfig) (channelpkg.ChannelConfig, error) {
	// Validate IMAP connection
	if err := p.service.ValidateIMAPConnection(config); err != nil {
		applogger.L().Warnf("Email OnCreate: IMAP connection validation failed: %v", err)
		return nil, fmt.Errorf("IMAP connection validation failed: %w", err)
	}

	// Validate SMTP connection
	if err := p.service.ValidateSMTPConnection(config); err != nil {
		applogger.L().Warnf("Email OnCreate: SMTP connection validation failed: %v", err)
		return nil, fmt.Errorf("SMTP connection validation failed: %w", err)
	}

	// Set forward_to_address for email relay (ActionMailbox-style)
	// Reference: Chatwoot's ensure_forward_to_address callback
	smtpEmail, _ := config["smtp_email"].(string)
	if smtpEmail != "" {
		config["forward_to_address"] = smtpEmail
	}

	applogger.L().Infof("Email OnCreate: IMAP+SMTP validated for inbox=%d email=%s", inbox.ID, smtpEmail)
	return config, nil
}

// OnDestroy handles cleanup before channel destruction.
// Email doesn't require external cleanup — IMAP/SMTP connections are per-session.
func (p *EmailProvider) OnDestroy(ctx context.Context, inbox *model.Inbox, config channelpkg.ChannelConfig) error {
	applogger.L().Infof("Email OnDestroy: channel destroyed for inbox=%d", inbox.ID)
	return nil
}

// === Messaging: Inbound ===

// ProcessIncoming transforms raw email payload into IncomingMessage.
// This handles both IMAP-pollled messages and webhook-relayed messages.
func (p *EmailProvider) ProcessIncoming(ctx context.Context, inbox *model.Inbox, rawPayload []byte) (*channelpkg.IncomingMessage, error) {
	var emailMsg EmailMessage
	if err := json.Unmarshal(rawPayload, &emailMsg); err != nil {
		return nil, fmt.Errorf("email ProcessIncoming: failed to parse payload: %w", err)
	}

	// Build IncomingMessage from parsed EmailMessage
	incoming := &channelpkg.IncomingMessage{
		ChannelType:    channelpkg.ChannelEmail,
		SourceID:       emailMsg.MessageID,
		ConversationID: emailMsg.InReplyTo, // threading via In-Reply-To
		SenderID:       emailMsg.FromAddress,
		SenderName:     emailMsg.FromName,
		SenderType:     channelpkg.SenderContact,
		Content:        emailMsg.TextContent,
		ContentType:    channelpkg.ContentEmail,
		InboxID:        inbox.ID,
		AccountID:      inbox.AccountID,
		ReceivedAt:     time.Now(),
		Extra: channelpkg.ChannelConfig{
			"subject":          emailMsg.Subject,
			"html_content":     emailMsg.HTMLContent,
			"reply_to_address": emailMsg.ReplyToAddress,
			"to_addresses":     emailMsg.ToAddresses,
			"cc_addresses":     emailMsg.CcAddresses,
			"in_reply_to":      emailMsg.InReplyTo,
			"references":       emailMsg.References,
			"imap_uid":         emailMsg.UID,
		},
	}

	// Convert attachments
	for _, att := range emailMsg.Attachments {
		incoming.Attachments = append(incoming.Attachments, channelpkg.Attachment{
			URL:         att.URL,
			ContentType: att.ContentType,
			Filename:    att.Filename,
			FileSize:    att.FileSize,
		})
	}

	// If there's a reply-to reference, set ReplyToID
	if emailMsg.InReplyTo != "" {
		incoming.ReplyToID = emailMsg.InReplyTo
	}

	return incoming, nil
}

// ValidateWebhookRequest verifies email webhook relay request authenticity.
// For email relay webhooks, we accept the request as-is since the relay
// service (Postfix, SES, Mailgun) handles its own authentication.
// Additional verification can be added per relay provider.
func (p *EmailProvider) ValidateWebhookRequest(ctx context.Context, inbox *model.Inbox, request *channelpkg.WebhookRequest) error {
	// Email webhook relay providers handle their own authentication:
	// - Mailgun: HMAC signature verification
	// - SendGrid: API key in headers
	// - SES: SNS signature verification
	// - Generic: basic auth or IP whitelist
	//
	// For now, we accept all relay requests. Per-provider verification
	// can be added based on the relay source identified in headers.
	return nil
}

// === Messaging: Outbound ===

// SendMessage sends an outgoing email via SMTP.
// Reference: Chatwoot's SendOnEmailService
func (p *EmailProvider) SendMessage(ctx context.Context, inbox *model.Inbox, message *model.Message, contact *model.Contact) (*channelpkg.SendResult, error) {
	config := parseInboxConfig(inbox.ChannelConfig)

	// Determine recipient email address
	toAddress := contact.SourceID
	if toAddress == "" {
		return nil, fmt.Errorf("email SendMessage: contact has no source_id (email address)")
	}

	// Determine sender email address
	fromAddress := configStr(config, "smtp_email", "")
	if fromAddress == "" {
		return nil, fmt.Errorf("email SendMessage: smtp_email not configured")
	}

	// Build subject from message content attributes or default
	subject := fmt.Sprintf("Message from gochat inbox #%d", inbox.ID)

	// Send via SMTP
	body := message.Content

	messageID, err := p.service.SendViaSMTP(config, fromAddress, toAddress, subject, body)
	if err != nil {
		return nil, fmt.Errorf("email SendMessage: SMTP send failed: %w", err)
	}

	applogger.L().Infof("Email SendMessage: sent to=%s subject=%s msg_id=%s", toAddress, subject, messageID)

	return &channelpkg.SendResult{
		ExternalID:  messageID,
		DeliveredAt: time.Now(),
		Extra: channelpkg.ChannelConfig{
			"from":    fromAddress,
			"to":      toAddress,
			"subject": subject,
		},
	}, nil
}

// === Contact Info ===

// GetContactProfile resolves a contact profile from an email address.
// Email contacts are identified by their email address; we construct
// a profile using the sender info from the email message headers.
func (p *EmailProvider) GetContactProfile(ctx context.Context, inbox *model.Inbox, contactSource string) (*channelpkg.ContactProfile, error) {
	// Email contacts are identified by email address (contactSource).
	// The profile is constructed from message headers (From name, From address).
	// No external API call is needed — email doesn't have a profile API.
	return &channelpkg.ContactProfile{
		Name: contactSource, // email address as name; real name comes from message headers
		Extra: channelpkg.ChannelConfig{
			"email": contactSource,
		},
	}, nil
}

// === Capabilities ===

func (p *EmailProvider) Capabilities() channelpkg.ChannelCapabilities {
	return channelpkg.ChannelCapabilities{
		SupportsAttachments:     true,  // email attachments (MIME multipart)
		SupportsLocation:        false,
		SupportsTypingIndicator: false,
		SupportsDeliveryStatus:  true,  // SMTP delivery status notifications (DSN)
		SupportsReplies:         true,  // threading via In-Reply-To/References
		SupportsEmojiReactions:  false,
		SupportsVoiceMessages:   false,
		SupportsVideoCalls:      false,
		SupportsCustomCards:     false,
		SupportsTemplates:       false,
		SupportsEmailHeaders:    true,  // subject, cc, bcc, reply-to
		MaxAttachmentSize:       25 * 1024 * 1024, // 25MB (typical email limit)
		MaxTextLength:           0,                // no practical limit for email
	}
}

// === PollingProvider Interface ===

// PollInterval returns the IMAP polling interval.
// Reference: Chatwoot's FetchImapEmailService runs every 5 minutes
func (p *EmailProvider) PollInterval() time.Duration {
	return 5 * time.Minute
}

// PollMessages fetches new email messages via IMAP polling.
// Reference: Chatwoot's Imap::FetchService
func (p *EmailProvider) PollMessages(ctx context.Context, inbox *model.Inbox) ([]*channelpkg.IncomingMessage, error) {
	config := parseInboxConfig(inbox.ChannelConfig)

	// Fetch messages via IMAP
	incomingMessages, err := p.service.FetchIMAPMessages(ctx, inbox, config)
	if err != nil {
		applogger.L().Errorf("Email PollMessages: IMAP fetch failed for inbox=%d: %v", inbox.ID, err)
		return nil, fmt.Errorf("IMAP fetch failed: %w", err)
	}

	if len(incomingMessages) == 0 {
		return nil, nil
	}

	// Process each message through the pipeline for full contact/conversation/message creation
	for _, msg := range incomingMessages {
		// Try to process via the pipeline for database persistence
		// The pipeline requires an EmailMessage, which we reconstruct from the IncomingMessage Extra
		if msg.Extra != nil {
			rawPayload, err := json.Marshal(msg)
			if err != nil {
				applogger.L().Warnf("Email PollMessages: failed to serialize message source_id=%s: %v", msg.SourceID, err)
				continue
			}

			// Reconstruct EmailMessage from the IncomingMessage's Extra data for pipeline processing
			var emailMsg EmailMessage
			if err := json.Unmarshal(rawPayload, &emailMsg); err != nil {
				applogger.L().Warnf("Email PollMessages: failed to reconstruct EmailMessage for source_id=%s: %v", msg.SourceID, err)
				continue
			}

			if _, err := p.pipeline.Process(ctx, inbox, &emailMsg); err != nil {
				applogger.L().Warnf("Email PollMessages: pipeline process failed for source_id=%s: %v", msg.SourceID, err)
				continue
			}
		}
	}

	applogger.L().Infof("Email PollMessages: fetched %d messages for inbox=%d", len(incomingMessages), inbox.ID)
	return incomingMessages, nil
}

// === Helpers ===

// parseInboxConfig converts the inbox's JSON string ChannelConfig into a ChannelConfig map.
func parseInboxConfig(configStr string) channelpkg.ChannelConfig {
	if configStr == "" {
		return channelpkg.ChannelConfig{}
	}
	var config channelpkg.ChannelConfig
	if err := json.Unmarshal([]byte(configStr), &config); err != nil {
		applogger.L().Warnf("Email: failed to parse inbox channel_config JSON: %v", err)
		return channelpkg.ChannelConfig{}
	}
	return config
}

// configStr extracts a string value from ChannelConfig with a default fallback.
func configStr(config channelpkg.ChannelConfig, key, defaultVal string) string {
	if v, ok := config[key]; ok {
		if s, ok := v.(string); ok && s != "" {
			return s
		}
	}
	return defaultVal
}

// === Registration ===

// SetPipeline sets the incoming message processor for this provider.
// Called by bootstrap after pipeline is created (pipeline depends on provider as IncomingMessageHandler).
func (p *EmailProvider) SetPipeline(pipeline *IncomingProcessor) {
	p.pipeline = pipeline
}

func init() {
	// Auto-register Email provider when this package is imported.
	// Requires dependencies to be injected via NewEmailProvider before use.
	// The actual registration happens in bootstrap when dependencies are available.
}