package campaign

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

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

// CampaignService provides business logic for campaign operations.
// Reference: Chatwoot CampaignService — CRUD + campaign triggering.
type CampaignService struct {
	db         *gorm.DB
	dispatcher *channel.Dispatcher
}

func NewCampaignService(db *gorm.DB, dispatchers ...*channel.Dispatcher) *CampaignService {
	var dispatcher *channel.Dispatcher
	if len(dispatchers) > 0 {
		dispatcher = dispatchers[0]
	}
	return &CampaignService{db: db, dispatcher: dispatcher}
}

// Create creates a new campaign.
func (s *CampaignService) Create(ctx context.Context, campaign *Campaign) error {
	if campaign.DisplayID == 0 {
		var next uint
		if err := s.db.WithContext(ctx).Model(&Campaign{}).
			Select("COALESCE(MAX(display_id), 0) + 1").Scan(&next).Error; err != nil {
			return err
		}
		campaign.DisplayID = next
	}
	return s.db.WithContext(ctx).Create(campaign).Error
}

// GetByID retrieves a campaign by ID.
func (s *CampaignService) GetByID(ctx context.Context, id uint) (*Campaign, error) {
	var c Campaign
	if err := s.db.WithContext(ctx).First(&c, id).Error; err != nil {
		return nil, err
	}
	return &c, nil
}

// ListByAccount returns campaigns for an account with pagination.
func (s *CampaignService) ListByAccount(ctx context.Context, accountID uint, offset, limit int) ([]Campaign, int64, error) {
	var campaigns []Campaign
	var count int64
	db := s.db.WithContext(ctx).Model(&Campaign{}).Where("account_id = ?", accountID)
	db.Count(&count)
	if err := db.Offset(offset).Limit(limit).Order("created_at DESC").Find(&campaigns).Error; err != nil {
		return nil, 0, err
	}
	return campaigns, count, nil
}

// ListByInbox returns campaigns for a specific inbox.
func (s *CampaignService) ListByInbox(ctx context.Context, accountID, inboxID uint) ([]Campaign, error) {
	var campaigns []Campaign
	err := s.db.WithContext(ctx).
		Where("account_id = ? AND inbox_id = ?", accountID, inboxID).
		Order("created_at DESC").Find(&campaigns).Error
	return campaigns, err
}

// Update updates campaign fields.
func (s *CampaignService) Update(ctx context.Context, id uint, updates map[string]interface{}) error {
	return s.db.WithContext(ctx).Model(&Campaign{}).Where("id = ?", id).Updates(updates).Error
}

// Delete soft-deletes a campaign.
func (s *CampaignService) Delete(ctx context.Context, id uint) error {
	return s.db.WithContext(ctx).Delete(&Campaign{}, id).Error
}

// MarkCompleted transitions a campaign to completed status.
func (s *CampaignService) MarkCompleted(ctx context.Context, id uint) error {
	return s.Update(ctx, id, map[string]interface{}{
		"campaign_status": CampaignStatusCompleted,
	})
}

// TriggerCampaign executes a campaign by creating conversations for the target audience.
// Reference: Chatwoot CampaignService.trigger — builds conversation from campaign.
func (s *CampaignService) TriggerCampaign(ctx context.Context, campaignID uint) error {
	campaign, err := s.GetByID(ctx, campaignID)
	if err != nil {
		return fmt.Errorf("campaign: get campaign: %w", err)
	}

	if !campaign.Enabled {
		applogger.L().Info("campaign: campaign is disabled, skipping trigger", "campaign_id", campaignID)
		return nil
	}

	builder := NewCampaignConversationBuilder(s.db, s.dispatcher)
	return builder.Build(ctx, campaign)
}

// CampaignConversationBuilder builds a conversation from a campaign trigger.
// Reference: Chatwoot CampaignListener — on campaign_triggered event -> builds conversation.
type CampaignConversationBuilder struct {
	db         *gorm.DB
	dispatcher *channel.Dispatcher
}

func NewCampaignConversationBuilder(db *gorm.DB, dispatchers ...*channel.Dispatcher) *CampaignConversationBuilder {
	var dispatcher *channel.Dispatcher
	if len(dispatchers) > 0 {
		dispatcher = dispatchers[0]
	}
	return &CampaignConversationBuilder{db: db, dispatcher: dispatcher}
}

// Build creates a new conversation from the campaign for each contact in the audience.
// The audience field (JSONB) contains contact IDs or filter criteria.
func (b *CampaignConversationBuilder) Build(ctx context.Context, campaign *Campaign) error {
	contactIDs, err := campaignAudienceContactIDs(campaign.Audience)
	if err != nil {
		return fmt.Errorf("campaign: parse audience: %w", err)
	}
	inbox := b.loadInbox(ctx, campaign)

	for _, contactID := range contactIDs {
		conv := &model.Conversation{
			AccountID:   campaign.AccountID,
			InboxID:     campaign.InboxID,
			ContactID:   contactID,
			CampaignID:  &campaign.ID,
			Status:      "open",
			ChannelType: "campaign",
		}

		if campaign.SenderID != nil {
			conv.AssigneeID = campaign.SenderID
		}

		if err := b.db.WithContext(ctx).Create(conv).Error; err != nil {
			applogger.L().Error("campaign: failed to create conversation for contact",
				"campaign_id", campaign.ID, "contact_id", contactID, "error", err)
			continue
		}
		b.dispatch(ctx, channel.EventConversationCreated, campaign, inbox, conv, nil)
		b.dispatch(ctx, channel.EventConversationOpened, campaign, inbox, conv, nil)

		// Create the initial campaign message in the conversation
		msg := &model.Message{
			ConversationID: conv.ID,
			AccountID:      campaign.AccountID,
			InboxID:        campaign.InboxID,
			Content:        campaign.Message,
			ContentType:    "template",
			MessageType:    "outgoing",
			SenderType:     "agent",
		}
		if campaign.SenderID != nil {
			msg.SenderID = campaign.SenderID
		}

		if err := b.db.WithContext(ctx).Create(msg).Error; err != nil {
			applogger.L().Error("campaign: failed to create campaign message",
				"campaign_id", campaign.ID, "conversation_id", conv.ID, "error", err)
			continue
		}
		b.dispatch(ctx, channel.EventMessageCreated, campaign, inbox, conv, msg)
		b.dispatch(ctx, channel.EventMessageOutgoing, campaign, inbox, conv, msg)

		applogger.L().Info("campaign: created conversation from campaign",
			"campaign_id", campaign.ID, "conversation_id", conv.ID, "contact_id", contactID)
	}

	return nil
}

func (b *CampaignConversationBuilder) loadInbox(ctx context.Context, c *Campaign) *model.Inbox {
	if c.Inbox.ID != 0 {
		return &c.Inbox
	}
	var inbox model.Inbox
	if err := b.db.WithContext(ctx).Where("account_id = ? AND id = ?", c.AccountID, c.InboxID).First(&inbox).Error; err != nil {
		return nil
	}
	return &inbox
}

func (b *CampaignConversationBuilder) dispatch(ctx context.Context, eventType channel.EventType, campaign *Campaign, inbox *model.Inbox, conversation *model.Conversation, message *model.Message) {
	if b.dispatcher == nil || campaign == nil || conversation == nil {
		return
	}
	channelType := channel.ChannelAPI
	inboxID := campaign.InboxID
	if inbox != nil {
		channelType = channel.ChannelType(inbox.ChannelType)
		inboxID = inbox.ID
	}
	event := channel.NewChannelEvent(eventType, channelType, campaign.AccountID, inboxID)
	event.ConversationID = conversation.ID
	event.ContactID = conversation.ContactID
	event.Data["campaign_id"] = campaign.ID
	event.Data["conversation"] = conversation
	if inbox != nil {
		event.Data["inbox"] = inbox
	}
	if message != nil {
		event.Data["message"] = message
	}
	if err := b.dispatcher.DispatchAsync(ctx, event); err != nil {
		applogger.L().Warn("campaign: failed to dispatch campaign event", "campaign_id", campaign.ID, "event", eventType, "error", err)
	}
}

func campaignAudienceContactIDs(raw string) ([]uint, error) {
	var audienceData struct {
		ContactIDs []uint `json:"contact_ids"`
	}
	if err := json.Unmarshal([]byte(raw), &audienceData); err == nil {
		return audienceData.ContactIDs, nil
	}

	var frontendRules []map[string]any
	if err := json.Unmarshal([]byte(raw), &frontendRules); err != nil {
		return nil, err
	}
	return []uint{}, nil
}