import { Injectable, Inject, Logger } from '@nestjs/common';
import { eq, and, desc, asc, sql } from 'drizzle-orm';
import {
  type AsyncResult,
  ok,
  err,
  DatabaseError,
  NotFoundError,
} from '@manacore/shared-errors';
import { DATABASE_CONNECTION } from '../db/database.module';
import { type Database } from '../db/connection';
import {
  conversations,
  type Conversation,
  type NewConversation,
} from '../db/schema/conversations.schema';
import { messages, type Message, type NewMessage } from '../db/schema/messages.schema';

@Injectable()
export class ConversationService {
  private readonly logger = new Logger(ConversationService.name);

  constructor(
    @Inject(DATABASE_CONNECTION) private readonly db: Database,
  ) {}

  async getConversations(
    userId: string,
    spaceId?: string,
  ): AsyncResult<Conversation[]> {
    try {
      const conditions = [
        eq(conversations.userId, userId),
        eq(conversations.isArchived, false),
      ];

      if (spaceId) {
        conditions.push(eq(conversations.spaceId, spaceId));
      }

      const result = await this.db
        .select()
        .from(conversations)
        .where(and(...conditions))
        .orderBy(desc(conversations.updatedAt));

      return ok(result);
    } catch (error) {
      this.logger.error('Error fetching conversations', error);
      return err(DatabaseError.queryFailed('Failed to fetch conversations'));
    }
  }

  async getArchivedConversations(userId: string): AsyncResult<Conversation[]> {
    try {
      const result = await this.db
        .select()
        .from(conversations)
        .where(
          and(
            eq(conversations.userId, userId),
            eq(conversations.isArchived, true),
          ),
        )
        .orderBy(desc(conversations.updatedAt));

      return ok(result);
    } catch (error) {
      this.logger.error('Error fetching archived conversations', error);
      return err(DatabaseError.queryFailed('Failed to fetch archived conversations'));
    }
  }

  async getConversation(id: string, userId: string): AsyncResult<Conversation> {
    try {
      const result = await this.db
        .select()
        .from(conversations)
        .where(
          and(eq(conversations.id, id), eq(conversations.userId, userId)),
        )
        .limit(1);

      if (result.length === 0) {
        return err(new NotFoundError('Conversation', id));
      }

      return ok(result[0]);
    } catch (error) {
      this.logger.error('Error fetching conversation', error);
      return err(DatabaseError.queryFailed('Failed to fetch conversation'));
    }
  }

  async getMessages(
    conversationId: string,
    userId: string,
  ): AsyncResult<Message[]> {
    try {
      // First verify the conversation belongs to the user
      const convResult = await this.getConversation(conversationId, userId);
      if (!convResult.ok) {
        return err(convResult.error);
      }

      const result = await this.db
        .select()
        .from(messages)
        .where(eq(messages.conversationId, conversationId))
        .orderBy(asc(messages.createdAt));

      return ok(result);
    } catch (error) {
      this.logger.error('Error fetching messages', error);
      return err(DatabaseError.queryFailed('Failed to fetch messages'));
    }
  }

  async createConversation(
    userId: string,
    modelId: string,
    options?: {
      title?: string;
      templateId?: string;
      conversationMode?: 'free' | 'guided' | 'template';
      documentMode?: boolean;
      spaceId?: string;
    },
  ): AsyncResult<Conversation> {
    try {
      const newConversation: NewConversation = {
        userId,
        modelId,
        title: options?.title || 'Neue Unterhaltung',
        templateId: options?.templateId,
        conversationMode: options?.conversationMode || 'free',
        documentMode: options?.documentMode || false,
        spaceId: options?.spaceId,
        isArchived: false,
      };

      const result = await this.db
        .insert(conversations)
        .values(newConversation)
        .returning();

      return ok(result[0]);
    } catch (error) {
      this.logger.error('Error creating conversation', error);
      return err(DatabaseError.queryFailed('Failed to create conversation'));
    }
  }

  async addMessage(
    conversationId: string,
    userId: string,
    sender: 'user' | 'assistant' | 'system',
    messageText: string,
  ): AsyncResult<Message> {
    try {
      // First verify the conversation belongs to the user
      const convResult = await this.getConversation(conversationId, userId);
      if (!convResult.ok) {
        return err(convResult.error);
      }

      const newMessage: NewMessage = {
        conversationId,
        sender,
        messageText,
      };

      const result = await this.db
        .insert(messages)
        .values(newMessage)
        .returning();

      // Update conversation updated_at
      await this.db
        .update(conversations)
        .set({ updatedAt: new Date() })
        .where(eq(conversations.id, conversationId));

      return ok(result[0]);
    } catch (error) {
      this.logger.error('Error adding message', error);
      return err(DatabaseError.queryFailed('Failed to add message'));
    }
  }

  async updateTitle(
    conversationId: string,
    userId: string,
    title: string,
  ): AsyncResult<Conversation> {
    try {
      // First verify the conversation belongs to the user
      const convResult = await this.getConversation(conversationId, userId);
      if (!convResult.ok) {
        return err(convResult.error);
      }

      const result = await this.db
        .update(conversations)
        .set({ title, updatedAt: new Date() })
        .where(eq(conversations.id, conversationId))
        .returning();

      return ok(result[0]);
    } catch (error) {
      this.logger.error('Error updating title', error);
      return err(DatabaseError.queryFailed('Failed to update title'));
    }
  }

  async archiveConversation(
    conversationId: string,
    userId: string,
  ): AsyncResult<Conversation> {
    try {
      // First verify the conversation belongs to the user
      const convResult = await this.getConversation(conversationId, userId);
      if (!convResult.ok) {
        return err(convResult.error);
      }

      const result = await this.db
        .update(conversations)
        .set({ isArchived: true, updatedAt: new Date() })
        .where(eq(conversations.id, conversationId))
        .returning();

      return ok(result[0]);
    } catch (error) {
      this.logger.error('Error archiving conversation', error);
      return err(DatabaseError.queryFailed('Failed to archive conversation'));
    }
  }

  async unarchiveConversation(
    conversationId: string,
    userId: string,
  ): AsyncResult<Conversation> {
    try {
      // First verify the conversation belongs to the user
      const convResult = await this.db
        .select()
        .from(conversations)
        .where(
          and(
            eq(conversations.id, conversationId),
            eq(conversations.userId, userId),
          ),
        )
        .limit(1);

      if (convResult.length === 0) {
        return err(new NotFoundError('Conversation', conversationId));
      }

      const result = await this.db
        .update(conversations)
        .set({ isArchived: false, updatedAt: new Date() })
        .where(eq(conversations.id, conversationId))
        .returning();

      return ok(result[0]);
    } catch (error) {
      this.logger.error('Error unarchiving conversation', error);
      return err(DatabaseError.queryFailed('Failed to unarchive conversation'));
    }
  }

  async deleteConversation(
    conversationId: string,
    userId: string,
  ): AsyncResult<void> {
    try {
      // First verify the conversation belongs to the user
      const convResult = await this.getConversation(conversationId, userId);
      if (!convResult.ok) {
        return err(convResult.error);
      }

      // Messages will be cascade deleted due to foreign key constraint
      await this.db
        .delete(conversations)
        .where(eq(conversations.id, conversationId));

      return ok(undefined);
    } catch (error) {
      this.logger.error('Error deleting conversation', error);
      return err(DatabaseError.queryFailed('Failed to delete conversation'));
    }
  }

  async getMessageCount(
    conversationId: string,
    userId: string,
  ): AsyncResult<number> {
    try {
      // First verify the conversation belongs to the user
      const convResult = await this.getConversation(conversationId, userId);
      if (!convResult.ok) {
        return err(convResult.error);
      }

      const result = await this.db
        .select({ count: sql<number>`count(*)` })
        .from(messages)
        .where(eq(messages.conversationId, conversationId));

      return ok(Number(result[0]?.count || 0));
    } catch (error) {
      this.logger.error('Error getting message count', error);
      return err(DatabaseError.queryFailed('Failed to get message count'));
    }
  }
}