package webhook

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

	"github.com/google/uuid"
	"gorm.io/datatypes"
	"gorm.io/gorm"

	"github.com/gochat/gochat/internal/channel"
	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/worker"
)

// IncomingPersister is the durable boundary after provider-specific webhook parsing.
// Reference: Chatwoot IncomingMessageService creates ContactInbox, Conversation, and Message.
type IncomingPersister struct {
	db         *gorm.DB
	dispatcher *channel.Dispatcher
	worker     *worker.WorkerPool
}

type IncomingPersistResult struct {
	Contact             *model.Contact
	ContactInbox        *model.ContactInbox
	Conversation        *model.Conversation
	Message             *model.Message
	Duplicate           bool
	ContactCreated      bool
	ConversationCreated bool
}

func (p *IncomingPersister) SetWorkerPool(wp *worker.WorkerPool) *IncomingPersister {
	if p == nil || wp == nil {
		return p
	}
	p.worker = wp
	p.registerJobs(wp)
	return p
}

func NewIncomingPersister(db *gorm.DB, dispatcher ...*channel.Dispatcher) *IncomingPersister {
	if db == nil {
		return nil
	}
	p := &IncomingPersister{db: db}
	if len(dispatcher) > 0 {
		p.dispatcher = dispatcher[0]
	}
	return p
}

func (p *IncomingPersister) PersistIncoming(ctx context.Context, inbox *model.Inbox, msg *channel.IncomingMessage) (*IncomingPersistResult, error) {
	if p == nil || p.db == nil || inbox == nil || msg == nil {
		return nil, nil
	}
	if err := validateIncomingMessage(p, inbox, msg); err != nil {
		return nil, err
	}
	if p.worker != nil {
		return nil, p.enqueueIncomingMessagePersist(ctx, inbox.ID, msg)
	}
	return p.performPersistIncoming(ctx, inbox, msg)
}

func validateIncomingMessage(p *IncomingPersister, inbox *model.Inbox, msg *channel.IncomingMessage) error {
	if p == nil || p.db == nil || inbox == nil || msg == nil {
		return nil
	}
	if msg.SourceID == "" {
		return fmt.Errorf("incoming message missing source_id")
	}
	senderID := msg.SenderID
	if senderID == "" {
		senderID = msg.ConversationID
	}
	if senderID == "" {
		return fmt.Errorf("incoming message missing sender_id")
	}
	if msg.Content == "" && len(msg.Attachments) == 0 {
		return fmt.Errorf("incoming message has no content or attachments")
	}
	return nil
}

func (p *IncomingPersister) performPersistIncoming(ctx context.Context, inbox *model.Inbox, msg *channel.IncomingMessage) (*IncomingPersistResult, error) {
	if p == nil || p.db == nil || inbox == nil || msg == nil {
		return nil, nil
	}
	senderID := msg.SenderID
	if senderID == "" {
		senderID = msg.ConversationID
	}

	var result IncomingPersistResult
	err := p.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var existingMessage model.Message
		if err := tx.Where("inbox_id = ? AND source_id = ?", inbox.ID, msg.SourceID).First(&existingMessage).Error; err == nil {
			result.Message = &existingMessage
			result.Duplicate = true
			return nil
		} else if err != gorm.ErrRecordNotFound {
			return err
		}

		contact, contactInbox, contactCreated, err := p.resolveOrCreateContactInbox(ctx, tx, inbox, msg, senderID)
		if err != nil {
			return err
		}
		result.Contact = contact
		result.ContactInbox = contactInbox
		result.ContactCreated = contactCreated

		conversation, conversationCreated, err := p.resolveOrCreateConversation(ctx, tx, inbox, contact, contactInbox, msg)
		if err != nil {
			return err
		}
		result.Conversation = conversation
		result.ConversationCreated = conversationCreated

		message, err := p.createMessage(ctx, tx, inbox, conversation, contact, msg)
		if err != nil {
			return err
		}
		result.Message = message
		return nil
	})
	if err != nil {
		return nil, err
	}
	p.dispatchIncomingEvents(ctx, inbox, &result)
	return &result, nil
}

// UpdateMessageStatus applies provider delivery/read/failed receipts to existing messages.
func (p *IncomingPersister) UpdateMessageStatus(ctx context.Context, inbox *model.Inbox, sourceID string, status model.MessageStatus, occurredAt *time.Time) error {
	return p.UpdateMessageStatusWithError(ctx, inbox, sourceID, status, occurredAt, "")
}

// UpdateMessageStatusWithError applies provider receipts and records provider failure details.
func (p *IncomingPersister) UpdateMessageStatusWithError(ctx context.Context, inbox *model.Inbox, sourceID string, status model.MessageStatus, occurredAt *time.Time, externalError string) error {
	if p == nil || p.db == nil || inbox == nil || sourceID == "" {
		return nil
	}
	if p.worker != nil {
		return p.enqueueMessageStatusUpdate(ctx, inbox.ID, sourceID, status, occurredAt, externalError)
	}
	return p.performMessageStatusUpdate(ctx, inbox, sourceID, status, occurredAt, externalError)
}

func (p *IncomingPersister) performMessageStatusUpdate(ctx context.Context, inbox *model.Inbox, sourceID string, status model.MessageStatus, occurredAt *time.Time, externalError string) error {
	if p == nil || p.db == nil || inbox == nil || sourceID == "" {
		return nil
	}

	return p.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var message model.Message
		if err := tx.Where("inbox_id = ? AND source_id = ?", inbox.ID, sourceID).First(&message).Error; err != nil {
			if err == gorm.ErrRecordNotFound {
				return nil
			}
			return err
		}
		if !validProviderMessageStatusTransition(model.MessageStatus(message.Status), status) {
			return nil
		}
		updates := map[string]any{
			"status":             string(status),
			"content_attributes": setProviderMessageExternalError(message.ContentAttributes, status, externalError),
		}
		if err := tx.Model(&message).Updates(updates).Error; err != nil {
			return err
		}
		message.Status = string(status)
		message.ContentAttributes = updates["content_attributes"].(datatypes.JSON)
		contactID, err := p.deliveryStatusContactID(ctx, tx, &message)
		if err != nil {
			return err
		}
		if contactID == 0 {
			p.dispatchMessageStatusEvent(ctx, inbox, &message)
			return nil
		}
		if err := p.upsertDeliveryStatus(ctx, tx, &message, contactID, status, occurredAt); err != nil {
			return err
		}
		p.dispatchMessageStatusEvent(ctx, inbox, &message)
		return nil
	})
}

// UpdateContactConversationMessagesStatus applies read receipts that only identify the contact/conversation.
func (p *IncomingPersister) UpdateContactConversationMessagesStatus(ctx context.Context, inbox *model.Inbox, contactSourceID string, status model.MessageStatus, occurredAt *time.Time) error {
	if p == nil || p.db == nil || inbox == nil || contactSourceID == "" {
		return nil
	}
	if p.worker != nil {
		return p.enqueueContactMessagesStatusUpdate(ctx, inbox.ID, contactSourceID, status, occurredAt)
	}
	return p.performContactMessagesStatusUpdate(ctx, inbox, contactSourceID, status, occurredAt)
}

func (p *IncomingPersister) performContactMessagesStatusUpdate(ctx context.Context, inbox *model.Inbox, contactSourceID string, status model.MessageStatus, occurredAt *time.Time) error {
	if p == nil || p.db == nil || inbox == nil || contactSourceID == "" {
		return nil
	}

	return p.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var contactInbox model.ContactInbox
		if err := tx.Where("inbox_id = ? AND source_id = ?", inbox.ID, contactSourceID).First(&contactInbox).Error; err != nil {
			if err == gorm.ErrRecordNotFound {
				return nil
			}
			return err
		}

		query := tx.Model(&model.Message{}).
			Joins("JOIN conversations ON conversations.id = messages.conversation_id").
			Where("messages.inbox_id = ? AND conversations.contact_id = ?", inbox.ID, contactInbox.ContactID).
			Where("messages.message_type = ?", model.MessageTypeOutgoing)
		if occurredAt != nil {
			query = query.Where("messages.created_at <= ?", *occurredAt)
		}

		var messages []model.Message
		if err := query.Select("messages.*").Find(&messages).Error; err != nil {
			return err
		}
		for i := range messages {
			if !validProviderMessageStatusTransition(model.MessageStatus(messages[i].Status), status) {
				continue
			}
			if err := tx.Model(&messages[i]).Updates(map[string]any{
				"status":             string(status),
				"content_attributes": setProviderMessageExternalError(messages[i].ContentAttributes, status, ""),
			}).Error; err != nil {
				return err
			}
			messages[i].Status = string(status)
			if err := p.upsertDeliveryStatus(ctx, tx, &messages[i], contactInbox.ContactID, status, occurredAt); err != nil {
				return err
			}
			p.dispatchMessageStatusEvent(ctx, inbox, &messages[i])
		}
		return nil
	})
}

func (p *IncomingPersister) deliveryStatusContactID(ctx context.Context, tx *gorm.DB, message *model.Message) (uint, error) {
	if message == nil {
		return 0, nil
	}
	if message.ConversationID != 0 {
		var conversation model.Conversation
		if err := tx.WithContext(ctx).Select("id", "contact_id").First(&conversation, message.ConversationID).Error; err != nil {
			if err != gorm.ErrRecordNotFound {
				return 0, err
			}
		} else if conversation.ContactID != 0 {
			return conversation.ContactID, nil
		}
	}
	if message.SenderID != nil {
		return *message.SenderID, nil
	}
	return 0, nil
}

func (p *IncomingPersister) upsertDeliveryStatus(ctx context.Context, tx *gorm.DB, message *model.Message, contactID uint, status model.MessageStatus, occurredAt *time.Time) error {
	var delivery model.DeliveryStatus
	err := tx.WithContext(ctx).Where("message_id = ? AND contact_id = ?", message.ID, contactID).First(&delivery).Error
	if err != nil && err != gorm.ErrRecordNotFound {
		return err
	}
	if err == gorm.ErrRecordNotFound {
		delivery = model.DeliveryStatus{MessageID: message.ID, InboxID: message.InboxID, ContactID: contactID}
	}
	delivery.Status = status
	if occurredAt != nil {
		switch status {
		case model.MessageStatusRead:
			delivery.ReadAt = occurredAt
		case model.MessageStatusDelivered:
			delivery.DeliveredAt = occurredAt
		}
	}
	if delivery.ID == 0 {
		return tx.WithContext(ctx).Create(&delivery).Error
	}
	return tx.WithContext(ctx).Save(&delivery).Error
}

func (p *IncomingPersister) dispatchIncomingEvents(ctx context.Context, inbox *model.Inbox, result *IncomingPersistResult) {
	if p.dispatcher == nil || result == nil || result.Duplicate {
		return
	}
	if result.ContactCreated && result.Contact != nil {
		p.dispatch(ctx, channel.EventContactCreated, inbox, result, nil)
	}
	if result.Conversation != nil {
		if result.ConversationCreated {
			p.dispatch(ctx, channel.EventConversationCreated, inbox, result, nil)
			p.dispatch(ctx, channel.EventConversationOpened, inbox, result, nil)
		} else {
			p.dispatch(ctx, channel.EventConversationUpdated, inbox, result, nil)
		}
	}
	if result.Message != nil {
		p.dispatch(ctx, channel.EventMessageCreated, inbox, result, result.Message)
		p.dispatch(ctx, channel.EventMessageIncoming, inbox, result, result.Message)
	}
}

func (p *IncomingPersister) dispatchMessageStatusEvent(ctx context.Context, inbox *model.Inbox, message *model.Message) {
	if p.dispatcher == nil || inbox == nil || message == nil {
		return
	}
	result := &IncomingPersistResult{Message: message}
	p.dispatch(ctx, channel.EventMessageStatusUpdated, inbox, result, message)
}

func (p *IncomingPersister) dispatch(ctx context.Context, eventType channel.EventType, inbox *model.Inbox, result *IncomingPersistResult, message *model.Message) {
	if p.dispatcher == nil || inbox == nil {
		return
	}
	channelType := channel.ChannelType(inbox.ChannelType)
	event := channel.NewChannelEvent(eventType, channelType, inbox.AccountID, inbox.ID)
	if result != nil {
		if result.Conversation != nil {
			event.ConversationID = result.Conversation.ID
			event.Data["conversation"] = result.Conversation
		}
		if result.Contact != nil {
			event.ContactID = result.Contact.ID
			event.Data["contact"] = result.Contact
		}
		if result.Message != nil {
			event.Data["message"] = result.Message
		}
	}
	if message != nil {
		event.ConversationID = message.ConversationID
		event.Data["message"] = message
		if message.SenderID != nil {
			event.ContactID = *message.SenderID
		}
	}
	event.Data["inbox"] = inbox
	if err := p.dispatcher.DispatchAsync(ctx, event); err != nil {
		// Chatwoot's async side effects should not make provider webhooks fail.
		_ = err
	}
}

func (p *IncomingPersister) resolveOrCreateContactInbox(ctx context.Context, tx *gorm.DB, inbox *model.Inbox, msg *channel.IncomingMessage, senderID string) (*model.Contact, *model.ContactInbox, bool, error) {
	var contactInbox model.ContactInbox
	if err := tx.WithContext(ctx).Preload("Contact").Where("inbox_id = ? AND source_id = ?", inbox.ID, senderID).First(&contactInbox).Error; err == nil {
		contact := contactInbox.Contact
		updates := map[string]interface{}{}
		if msg.SenderName != "" && contact.Name != msg.SenderName {
			updates["name"] = msg.SenderName
		}
		if len(updates) > 0 {
			if err := tx.WithContext(ctx).Model(&contact).Updates(updates).Error; err != nil {
				return nil, nil, false, err
			}
			if err := tx.WithContext(ctx).First(&contact, contact.ID).Error; err != nil {
				return nil, nil, false, err
			}
		}
		return &contact, &contactInbox, false, nil
	} else if err != gorm.ErrRecordNotFound {
		return nil, nil, false, err
	}

	name := msg.SenderName
	if name == "" {
		name = senderID
	}
	attrs := mergeChannelConfig(msg.SenderExtra, map[string]interface{}{
		"source_id":    senderID,
		"channel_type": string(msg.ChannelType),
	})
	contact := model.Contact{
		AccountID:            inbox.AccountID,
		Name:                 name,
		Identifier:           senderID,
		SourceID:             string(msg.ChannelType),
		AdditionalAttributes: mustJSON(attrs),
		CustomAttributes:     datatypes.JSON("{}"),
	}
	if err := tx.WithContext(ctx).Create(&contact).Error; err != nil {
		return nil, nil, false, err
	}

	contactInbox = model.ContactInbox{
		ContactID:   contact.ID,
		InboxID:     inbox.ID,
		SourceID:    senderID,
		PubsubToken: uuid.NewString(),
	}
	if err := tx.WithContext(ctx).Create(&contactInbox).Error; err != nil {
		return nil, nil, false, err
	}
	return &contact, &contactInbox, true, nil
}

func (p *IncomingPersister) resolveOrCreateConversation(ctx context.Context, tx *gorm.DB, inbox *model.Inbox, contact *model.Contact, contactInbox *model.ContactInbox, msg *channel.IncomingMessage) (*model.Conversation, bool, error) {
	var conversation model.Conversation
	if err := tx.WithContext(ctx).
		Where("account_id = ? AND inbox_id = ? AND contact_id = ? AND status = ?", inbox.AccountID, inbox.ID, contact.ID, model.ConversationStatusOpen).
		Order("id DESC").First(&conversation).Error; err == nil {
		now := time.Now().Unix()
		_ = tx.WithContext(ctx).Model(&conversation).Updates(map[string]interface{}{
			"last_activity_at": now,
			"last_message_at":  now,
		}).Error
		return &conversation, false, nil
	} else if err != gorm.ErrRecordNotFound {
		return nil, false, err
	}

	now := time.Now().Unix()
	channelType := inbox.ChannelType
	if msg.ChannelType != "" {
		channelType = string(msg.ChannelType)
	}
	conversation = model.Conversation{
		AccountID:            inbox.AccountID,
		InboxID:              inbox.ID,
		ContactID:            contact.ID,
		ContactInboxID:       &contactInbox.ID,
		Status:               string(model.ConversationStatusOpen),
		Priority:             "none",
		ChannelType:          channelType,
		Channel:              inbox.ChannelType,
		LastActivityAt:       &now,
		LastMessageAt:        &now,
		LastNonSysMsgAt:      &now,
		AdditionalAttributes: mustJSON(mergeChannelConfig(msg.ConversationExtra, map[string]interface{}{"external_conversation_id": msg.ConversationID})),
		CustomAttributes:     datatypes.JSON("{}"),
	}
	if err := tx.WithContext(ctx).Create(&conversation).Error; err != nil {
		return nil, false, err
	}
	return &conversation, true, nil
}

func (p *IncomingPersister) createMessage(ctx context.Context, tx *gorm.DB, inbox *model.Inbox, conversation *model.Conversation, contact *model.Contact, msg *channel.IncomingMessage) (*model.Message, error) {
	contentAttrs := map[string]interface{}{}
	if len(msg.Attachments) > 0 {
		contentAttrs["attachments"] = msg.Attachments
	}
	if msg.ReplyToID != "" {
		contentAttrs["in_reply_to"] = msg.ReplyToID
	}
	message := model.Message{
		ConversationID:       conversation.ID,
		AccountID:            inbox.AccountID,
		InboxID:              inbox.ID,
		SenderID:             &contact.ID,
		SenderType:           string(model.SenderTypeContact),
		Content:              msg.Content,
		ContentType:          mapIncomingContentType(msg.ContentType),
		Status:               string(model.MessageStatusSent),
		MessageType:          string(model.MessageTypeIncoming),
		SourceID:             msg.SourceID,
		ContentAttributes:    mustJSON(contentAttrs),
		AdditionalAttributes: mustJSON(msg.Extra),
	}
	if err := tx.WithContext(ctx).Create(&message).Error; err != nil {
		return nil, err
	}
	return &message, nil
}

func mapIncomingContentType(contentType channel.ContentType) string {
	switch contentType {
	case channel.ContentImage:
		return string(model.MessageContentTypeImage)
	case channel.ContentAudio:
		return string(model.MessageContentTypeAudio)
	case channel.ContentVideo:
		return string(model.MessageContentTypeVideo)
	case channel.ContentFile:
		return string(model.MessageContentTypeFile)
	case channel.ContentLocation:
		return string(model.MessageContentTypeLocation)
	default:
		return string(model.MessageContentTypeText)
	}
}

func mergeChannelConfig(base channel.ChannelConfig, extra map[string]interface{}) map[string]interface{} {
	merged := map[string]interface{}{}
	for k, v := range base {
		merged[k] = v
	}
	for k, v := range extra {
		if v != "" && v != nil {
			merged[k] = v
		}
	}
	return merged
}

func mustJSON(value interface{}) datatypes.JSON {
	if value == nil {
		return datatypes.JSON("{}")
	}
	data, err := json.Marshal(value)
	if err != nil || len(data) == 0 {
		return datatypes.JSON("{}")
	}
	return datatypes.JSON(data)
}