import { db } from "./db";
import {
  chats,
  messages,
  type Chat,
  type Message,
  MessageRole,
  type MessagePart,
  type DBMessage,
} from "./db/schema";
import { eq, desc, and } from "drizzle-orm";
import { nanoid } from "nanoid";
import { generateTitle } from "@/app/actions";

type AIMessage = {
  role: string;
  content: string | any[];
  id?: string;
  parts?: MessagePart[];
};

type UIMessage = {
  id: string;
  role: string;
  content: string;
  parts: MessagePart[];
  createdAt?: Date;
};

type SaveChatParams = {
  id?: string;
  userId: string;
  messages?: any[];
  title?: string;
};

type ChatWithMessages = Chat & {
  messages: Message[];
};

export async function saveMessages({
  messages: dbMessages,
}: {
  messages: Array<DBMessage>;
}) {
  try {
    if (dbMessages.length > 0) {
      const chatId = dbMessages[0].chatId;

      // First delete any existing messages for this chat
      await db.delete(messages).where(eq(messages.chatId, chatId));

      // Then insert the new messages
      return await db.insert(messages).values(dbMessages);
    }
    return null;
  } catch (error) {
    console.error("Failed to save messages in database", error);
    throw error;
  }
}

// Function to convert AI messages to DB format
export function convertToDBMessages(
  aiMessages: AIMessage[],
  chatId: string
): DBMessage[] {
  return aiMessages.map((msg) => {
    // Use existing id or generate a new one
    const messageId = msg.id || nanoid();

    // If msg has parts, use them directly
    if (msg.parts) {
      return {
        id: messageId,
        chatId,
        role: msg.role,
        parts: msg.parts,
        createdAt: new Date(),
      };
    }

    // Otherwise, convert content to parts
    let parts: MessagePart[];

    if (typeof msg.content === "string") {
      const thinkRegex = /<think>([\s\S]*?)<\/think>/g;
      const content = msg.content;
      parts = [];
      let lastIndex = 0;
      let match;

      while ((match = thinkRegex.exec(content)) !== null) {
        // Add text part before the think tag
        if (match.index > lastIndex) {
          parts.push({
            type: "text",
            text: content.substring(lastIndex, match.index),
          });
        }

        // Add the thinking part
        parts.push({
          type: "thinking",
          thinking: match[1],
          details: [{ type: "text", text: match[1] }],
        });

        lastIndex = thinkRegex.lastIndex;
      }

      // Add any remaining text part
      if (lastIndex < content.length) {
        parts.push({ type: "text", text: content.substring(lastIndex) });
      }

      // If no thinking tags were found, treat the whole content as a single text part
      if (parts.length === 0) {
        parts.push({ type: "text", text: content });
      }
    } else if (Array.isArray(msg.content)) {
      if (
        msg.content.every((item) => typeof item === "object" && item !== null)
      ) {
        // Content is already in parts-like format
        parts = msg.content as MessagePart[];
      } else {
        // Content is an array but not in parts format
        parts = [{ type: "text", text: JSON.stringify(msg.content) }];
      }
    } else {
      // Default case
      parts = [{ type: "text", text: String(msg.content) }];
    }

    return {
      id: messageId,
      chatId,
      role: msg.role,
      parts,
      createdAt: new Date(),
    };
  });
}

// Convert DB messages to UI format
export function convertToUIMessages(
  dbMessages: Array<Message>
): Array<UIMessage> {
  return dbMessages.map((message) => ({
    id: message.id,
    parts: message.parts as MessagePart[],
    role: message.role as string,
    content: getTextContent(message), // For backward compatibility
    createdAt: message.createdAt,
  }));
}

export async function saveChat({
  id,
  userId,
  messages: aiMessages,
  title,
}: SaveChatParams) {
  // Generate a new ID if one wasn't provided
  const chatId = id || nanoid();

  // Check if title is provided, if not generate one
  let chatTitle = title;

  // Generate title if messages are provided and no title is specified
  if (aiMessages && aiMessages.length > 0) {
    const hasEnoughMessages =
      aiMessages.length >= 2 &&
      aiMessages.some((m) => m.role === "user") &&
      aiMessages.some((m) => m.role === "assistant");

    if (!chatTitle || chatTitle === "New Chat" || chatTitle === undefined) {
      if (hasEnoughMessages) {
        try {
          // Use AI to generate a meaningful title based on conversation
          chatTitle = await generateTitle(aiMessages);
        } catch (error) {
          console.error("Error generating title:", error);
          // Fallback to basic title extraction if AI title generation fails
          const firstUserMessage = aiMessages.find((m) => m.role === "user");
          if (firstUserMessage) {
            // Check for parts first (new format)
            if (
              firstUserMessage.parts &&
              Array.isArray(firstUserMessage.parts)
            ) {
              const textParts = firstUserMessage.parts.filter(
                (p: MessagePart) => p.type === "text" && p.text
              );
              if (textParts.length > 0) {
                chatTitle = textParts[0].text?.slice(0, 50) || "New Chat";
                if ((textParts[0].text?.length || 0) > 50) {
                  chatTitle += "...";
                }
              } else {
                chatTitle = "New Chat";
              }
            }
            // Fallback to content (old format)
            else if (typeof firstUserMessage.content === "string") {
              chatTitle = firstUserMessage.content.slice(0, 50);
              if (firstUserMessage.content.length > 50) {
                chatTitle += "...";
              }
            } else {
              chatTitle = "New Chat";
            }
          } else {
            chatTitle = "New Chat";
          }
        }
      } else {
        // Not enough messages for AI title, use first message
        const firstUserMessage = aiMessages.find((m) => m.role === "user");
        if (firstUserMessage) {
          // Check for parts first (new format)
          if (firstUserMessage.parts && Array.isArray(firstUserMessage.parts)) {
            const textParts = firstUserMessage.parts.filter(
              (p: MessagePart) => p.type === "text" && p.text
            );
            if (textParts.length > 0) {
              chatTitle = textParts[0].text?.slice(0, 50) || "New Chat";
              if ((textParts[0].text?.length || 0) > 50) {
                chatTitle += "...";
              }
            } else {
              chatTitle = "New Chat";
            }
          }
          // Fallback to content (old format)
          else if (typeof firstUserMessage.content === "string") {
            chatTitle = firstUserMessage.content.slice(0, 50);
            if (firstUserMessage.content.length > 50) {
              chatTitle += "...";
            }
          } else {
            chatTitle = "New Chat";
          }
        } else {
          chatTitle = "New Chat";
        }
      }
    }
  } else {
    chatTitle = chatTitle || "New Chat";
  }

  // Check if chat already exists
  const existingChat = await db.query.chats.findFirst({
    where: and(eq(chats.id, chatId), eq(chats.userId, userId)),
  });

  if (existingChat) {
    // Update existing chat
    await db
      .update(chats)
      .set({
        title: chatTitle,
        updatedAt: new Date(),
      })
      .where(and(eq(chats.id, chatId), eq(chats.userId, userId)));
  } else {
    // Create new chat
    await db.insert(chats).values({
      id: chatId,
      userId,
      title: chatTitle,
      createdAt: new Date(),
      updatedAt: new Date(),
    });
  }

  return { id: chatId };
}

// Helper to get just the text content for display
export function getTextContent(message: Message): string {
  try {
    const parts = message.parts as MessagePart[];
    return parts
      .filter((part) => part.type === "text" && part.text)
      .map((part) => part.text)
      .join("\n");
  } catch (e) {
    // If parsing fails, return empty string
    return "";
  }
}

export async function getChats(userId: string) {
  return await db.query.chats.findMany({
    where: eq(chats.userId, userId),
    orderBy: [desc(chats.updatedAt)],
  });
}

export async function getChatById(
  id: string,
  userId: string
): Promise<ChatWithMessages | null> {
  const chat = await db.query.chats.findFirst({
    where: and(eq(chats.id, id), eq(chats.userId, userId)),
  });

  if (!chat) return null;

  const chatMessages = await db.query.messages.findMany({
    where: eq(messages.chatId, id),
    orderBy: [messages.createdAt],
  });

  return {
    ...chat,
    messages: chatMessages,
  };
}

export async function deleteChat(id: string, userId: string) {
  await db.delete(chats).where(and(eq(chats.id, id), eq(chats.userId, userId)));
}