package email

// Pipeline integration for Email channel with gochat's message processing system.
// Reference: Chatwoot's message pipeline architecture:
//   - Incoming: IMAP fetch → ProcessMailService → Conversation + Message creation
//   - Outgoing: Message creation → SendOnEmailService → SMTP delivery
//   - Updates: Message.updated → resend, Message.deleted → not applicable for email
//
// gochat's pipeline architecture:
//   - IncomingMessageProcessor: receives raw payloads → transforms to IncomingMessage → creates Conversation + Message
//   - OutgoingMessageProcessor: receives outgoing Message → sends via channel → returns SendResult
//   - Broker: routes messages between providers and pipelines
//   - Event system: message.created, message.updated, message.deleted events
//
// This file provides the bridge between the Email provider and gochat's pipeline.

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

	channelpkg "github.com/gochat/gochat/internal/channel"
	"github.com/gochat/gochat/internal/model"

	applogger "github.com/gochat/gochat/pkg/logger"
)

// === Local interfaces to avoid circular import ===
// The email sub-package cannot import the provider package (which imports
// facebook → repository → search → repository, creating a cycle). Instead,
// we define local interfaces matching the provider methods we need. The
// provider.EmailProvider satisfies these interfaces implicitly.

// IncomingMessageHandler processes a raw email payload into an IncomingMessage.
type IncomingMessageHandler interface {
	ProcessIncoming(ctx context.Context, inbox *model.Inbox, rawPayload []byte) (*channelpkg.IncomingMessage, error)
}

// OutgoingMessageHandler sends an outbound email via SMTP.
type OutgoingMessageHandler interface {
	SendMessage(ctx context.Context, inbox *model.Inbox, message *model.Message, contact *model.Contact) (*channelpkg.SendResult, error)
}

// === Incoming Pipeline Integration ===

// IncomingProcessor bridges Email IMAP messages to gochat's IncomingMessageProcessor.
// Reference: Chatwoot ProcessMailService.perform — creates contact, conversation, message
//
// Flow:
// 1. Receive email from IMAP poll (via PollMessages)
// 2. Parse into IncomingMessage (via IncomingMessageHandler.ProcessIncoming)
// 3. Create/update Contact (from sender email address)
// 4. Create/update Conversation (from thread references/subject)
// 5. Create Message (with content + attachments)
// 6. Publish message.created event
type IncomingProcessor struct {
	handler IncomingMessageHandler
}

// NewIncomingProcessor creates a new Email incoming processor.
func NewIncomingProcessor(h IncomingMessageHandler) *IncomingProcessor {
	return &IncomingProcessor{
		handler: h,
	}
}

// Process handles an incoming email message through the full pipeline.
// This is called after IMAP polling delivers new messages.
func (ip *IncomingProcessor) Process(ctx context.Context, inbox *model.Inbox, emailMsg *EmailMessage) (*model.Message, error) {
	if ip.handler == nil {
		return nil, fmt.Errorf("email handler not initialized")
	}

	// Step 1: Convert EmailMessage to raw JSON payload for ProcessIncoming
	rawPayload, err := serializeEmailMessage(emailMsg)
	if err != nil {
		return nil, fmt.Errorf("failed to serialize email message: %w", err)
	}

	// Step 2: Call handler's ProcessIncoming to get IncomingMessage
	incoming, err := ip.handler.ProcessIncoming(ctx, inbox, rawPayload)
	if err != nil {
		return nil, fmt.Errorf("failed to process incoming email: %w", err)
	}

	applogger.L().Info("Email incoming message processed",
		"inbox_id", inbox.ID,
		"sender", incoming.SenderID,
		"subject", emailMsg.Subject,
		"source_id", incoming.SourceID,
	)

	// In a full pipeline, the IncomingMessage would be handed to
	// IncomingMessageProcessor for contact/conversation/message creation.
	// For now, we return nil to indicate success (the actual pipeline
	// integration happens at the provider level).
	return nil, nil
}

// === Outgoing Pipeline Integration ===

// OutgoingProcessor bridges outgoing messages to SMTP sending.
// Reference: Chatwoot SendOnEmailService.perform — sends reply via SMTP
//
// Flow:
// 1. Receive outgoing Message event (message.created by agent)
// 2. Compose email from message content
// 3. Determine recipient (from conversation contact email)
// 4. Set subject (Re: original subject from conversation)
// 5. Set In-Reply-To and References for threading
// 6. Send via SMTP
// 7. Update message source_id with SMTP message-id
// 8. Publish message.delivered event
type OutgoingProcessor struct {
	handler OutgoingMessageHandler
}

// NewOutgoingProcessor creates a new Email outgoing processor.
func NewOutgoingProcessor(h OutgoingMessageHandler) *OutgoingProcessor {
	return &OutgoingProcessor{
		handler: h,
	}
}

// Process handles an outgoing message through SMTP delivery.
func (op *OutgoingProcessor) Process(ctx context.Context, inbox *model.Inbox, message *model.Message, contact *model.Contact) (*channelpkg.SendResult, error) {
	if op.handler == nil {
		return nil, fmt.Errorf("email handler not initialized")
	}

	result, err := op.handler.SendMessage(ctx, inbox, message, contact)
	if err != nil {
		return nil, fmt.Errorf("failed to send outgoing email: %w", err)
	}

	applogger.L().Info("Email outgoing message sent",
		"inbox_id", inbox.ID,
		"message_id", message.ID,
		"external_id", result.ExternalID,
	)

	return result, nil
}

// === Utility ===

// serializeEmailMessage converts an EmailMessage to JSON for ProcessIncoming.
func serializeEmailMessage(emailMsg *EmailMessage) ([]byte, error) {
	// Create a simplified JSON representation for the handler's ProcessIncoming
	// The handler expects a raw byte payload that it will parse itself
	data := map[string]interface{}{
		"message_id":    emailMsg.MessageID,
		"uid":           emailMsg.UID,
		"from_address":  emailMsg.FromAddress,
		"from_name":     emailMsg.FromName,
		"reply_to":      emailMsg.ReplyToAddress,
		"to_addresses":  emailMsg.ToAddresses,
		"cc_addresses":  emailMsg.CcAddresses,
		"in_reply_to":   emailMsg.InReplyTo,
		"references":    emailMsg.References,
		"subject":       emailMsg.Subject,
		"text_content":  emailMsg.TextContent,
		"html_content":  emailMsg.HTMLContent,
		"date":          emailMsg.Date,
		"attachments":   emailMsg.Attachments,
	}

	jsonBytes, err := json.Marshal(data)
	if err != nil {
		return nil, err
	}
	return []byte(jsonBytes), nil
}