/** Memories */
import { z } from 'zod';
import { tool } from '@langchain/core/tools';
import { Tools } from 'librechat-data-provider';
import { logger } from '@librechat/data-schemas';
import { Run, Providers, GraphEvents } from '@librechat/agents';
import type {
  OpenAIClientOptions,
  StreamEventData,
  ToolEndCallback,
  ClientOptions,
  EventHandler,
  ToolEndData,
  LLMConfig,
} from '@librechat/agents';
import type { TAttachment, MemoryArtifact } from 'librechat-data-provider';
import type { ObjectId, MemoryMethods } from '@librechat/data-schemas';
import type { BaseMessage } from '@langchain/core/messages';
import type { Response as ServerResponse } from 'express';
import { Tokenizer } from '~/utils';

type RequiredMemoryMethods = Pick<
  MemoryMethods,
  'setMemory' | 'deleteMemory' | 'getFormattedMemories'
>;

type ToolEndMetadata = Record<string, unknown> & {
  run_id?: string;
  thread_id?: string;
};

export interface MemoryConfig {
  validKeys?: string[];
  instructions?: string;
  llmConfig?: Partial<LLMConfig>;
  tokenLimit?: number;
}

export const memoryInstructions =
  'The system automatically stores important user information and can update or delete memories based on user requests, enabling dynamic memory management.';

const getDefaultInstructions = (
  validKeys?: string[],
  tokenLimit?: number,
) => `Use the \`set_memory\` tool to save important information about the user, but ONLY when the user has requested you to remember something.

The \`delete_memory\` tool should only be used in two scenarios:
  1. When the user explicitly asks to forget or remove specific information
  2. When updating existing memories, use the \`set_memory\` tool instead of deleting and re-adding the memory.

1. ONLY use memory tools when the user requests memory actions with phrases like:
   - "Remember [that] [I]..."
   - "Don't forget [that] [I]..."
   - "Please remember..."
   - "Store this..."
   - "Forget [that] [I]..."
   - "Delete the memory about..."

2. NEVER store information just because the user mentioned it in conversation.

3. NEVER use memory tools when the user asks you to use other tools or invoke tools in general.

4. Memory tools are ONLY for memory requests, not for general tool usage.

5. If the user doesn't ask you to remember or forget something, DO NOT use any memory tools.

${validKeys && validKeys.length > 0 ? `\nVALID KEYS: ${validKeys.join(', ')}` : ''}

${tokenLimit ? `\nTOKEN LIMIT: Maximum ${tokenLimit} tokens per memory value.` : ''}

When in doubt, and the user hasn't asked to remember or forget anything, END THE TURN IMMEDIATELY.`;

/**
 * Creates a memory tool instance with user context
 */
export const createMemoryTool = ({
  userId,
  setMemory,
  validKeys,
  tokenLimit,
  totalTokens = 0,
}: {
  userId: string | ObjectId;
  setMemory: MemoryMethods['setMemory'];
  validKeys?: string[];
  tokenLimit?: number;
  totalTokens?: number;
}) => {
  const remainingTokens = tokenLimit ? tokenLimit - totalTokens : Infinity;
  const isOverflowing = tokenLimit ? remainingTokens <= 0 : false;

  return tool(
    async ({ key, value }) => {
      try {
        if (validKeys && validKeys.length > 0 && !validKeys.includes(key)) {
          logger.warn(
            `Memory Agent failed to set memory: Invalid key "${key}". Must be one of: ${validKeys.join(
              ', ',
            )}`,
          );
          return [`Invalid key "${key}". Must be one of: ${validKeys.join(', ')}`, undefined];
        }

        const tokenCount = Tokenizer.getTokenCount(value, 'o200k_base');

        if (isOverflowing) {
          const errorArtifact: Record<Tools.memory, MemoryArtifact> = {
            [Tools.memory]: {
              key: 'system',
              type: 'error',
              value: JSON.stringify({
                errorType: 'already_exceeded',
                tokenCount: Math.abs(remainingTokens),
                totalTokens: totalTokens,
                tokenLimit: tokenLimit!,
              }),
              tokenCount: totalTokens,
            },
          };
          return [`Memory storage exceeded. Cannot save new memories.`, errorArtifact];
        }

        if (tokenLimit) {
          const newTotalTokens = totalTokens + tokenCount;
          const newRemainingTokens = tokenLimit - newTotalTokens;

          if (newRemainingTokens < 0) {
            const errorArtifact: Record<Tools.memory, MemoryArtifact> = {
              [Tools.memory]: {
                key: 'system',
                type: 'error',
                value: JSON.stringify({
                  errorType: 'would_exceed',
                  tokenCount: Math.abs(newRemainingTokens),
                  totalTokens: newTotalTokens,
                  tokenLimit,
                }),
                tokenCount: totalTokens,
              },
            };
            return [`Memory storage would exceed limit. Cannot save this memory.`, errorArtifact];
          }
        }

        const artifact: Record<Tools.memory, MemoryArtifact> = {
          [Tools.memory]: {
            key,
            value,
            tokenCount,
            type: 'update',
          },
        };

        const result = await setMemory({ userId, key, value, tokenCount });
        if (result.ok) {
          logger.debug(`Memory set for key "${key}" (${tokenCount} tokens) for user "${userId}"`);
          return [`Memory set for key "${key}" (${tokenCount} tokens)`, artifact];
        }
        logger.warn(`Failed to set memory for key "${key}" for user "${userId}"`);
        return [`Failed to set memory for key "${key}"`, undefined];
      } catch (error) {
        logger.error('Memory Agent failed to set memory', error);
        return [`Error setting memory for key "${key}"`, undefined];
      }
    },
    {
      name: 'set_memory',
      description: 'Saves important information about the user into memory.',
      responseFormat: 'content_and_artifact',
      schema: z.object({
        key: z
          .string()
          .describe(
            validKeys && validKeys.length > 0
              ? `The key of the memory value. Must be one of: ${validKeys.join(', ')}`
              : 'The key identifier for this memory',
          ),
        value: z
          .string()
          .describe(
            'Value MUST be a complete sentence that fully describes relevant user information.',
          ),
      }),
    },
  );
};

/**
 * Creates a delete memory tool instance with user context
 */
const createDeleteMemoryTool = ({
  userId,
  deleteMemory,
  validKeys,
}: {
  userId: string | ObjectId;
  deleteMemory: MemoryMethods['deleteMemory'];
  validKeys?: string[];
}) => {
  return tool(
    async ({ key }) => {
      try {
        if (validKeys && validKeys.length > 0 && !validKeys.includes(key)) {
          logger.warn(
            `Memory Agent failed to delete memory: Invalid key "${key}". Must be one of: ${validKeys.join(
              ', ',
            )}`,
          );
          return [`Invalid key "${key}". Must be one of: ${validKeys.join(', ')}`, undefined];
        }

        const artifact: Record<Tools.memory, MemoryArtifact> = {
          [Tools.memory]: {
            key,
            type: 'delete',
          },
        };

        const result = await deleteMemory({ userId, key });
        if (result.ok) {
          logger.debug(`Memory deleted for key "${key}" for user "${userId}"`);
          return [`Memory deleted for key "${key}"`, artifact];
        }
        logger.warn(`Failed to delete memory for key "${key}" for user "${userId}"`);
        return [`Failed to delete memory for key "${key}"`, undefined];
      } catch (error) {
        logger.error('Memory Agent failed to delete memory', error);
        return [`Error deleting memory for key "${key}"`, undefined];
      }
    },
    {
      name: 'delete_memory',
      description:
        'Deletes specific memory data about the user using the provided key. For updating existing memories, use the `set_memory` tool instead',
      responseFormat: 'content_and_artifact',
      schema: z.object({
        key: z
          .string()
          .describe(
            validKeys && validKeys.length > 0
              ? `The key of the memory to delete. Must be one of: ${validKeys.join(', ')}`
              : 'The key identifier of the memory to delete',
          ),
      }),
    },
  );
};
export class BasicToolEndHandler implements EventHandler {
  private callback?: ToolEndCallback;
  constructor(callback?: ToolEndCallback) {
    this.callback = callback;
  }
  handle(
    event: string,
    data: StreamEventData | undefined,
    metadata?: Record<string, unknown>,
  ): void {
    if (!metadata) {
      console.warn(`Graph or metadata not found in ${event} event`);
      return;
    }
    const toolEndData = data as ToolEndData | undefined;
    if (!toolEndData?.output) {
      console.warn('No output found in tool_end event');
      return;
    }
    this.callback?.(toolEndData, metadata);
  }
}

export async function processMemory({
  res,
  userId,
  setMemory,
  deleteMemory,
  messages,
  memory,
  messageId,
  conversationId,
  validKeys,
  instructions,
  llmConfig,
  tokenLimit,
  totalTokens = 0,
}: {
  res: ServerResponse;
  setMemory: MemoryMethods['setMemory'];
  deleteMemory: MemoryMethods['deleteMemory'];
  userId: string | ObjectId;
  memory: string;
  messageId: string;
  conversationId: string;
  messages: BaseMessage[];
  validKeys?: string[];
  instructions: string;
  tokenLimit?: number;
  totalTokens?: number;
  llmConfig?: Partial<LLMConfig>;
}): Promise<(TAttachment | null)[] | undefined> {
  try {
    const memoryTool = createMemoryTool({
      userId,
      tokenLimit,
      setMemory,
      validKeys,
      totalTokens,
    });
    const deleteMemoryTool = createDeleteMemoryTool({
      userId,
      validKeys,
      deleteMemory,
    });

    const currentMemoryTokens = totalTokens;

    let memoryStatus = `# Existing memory:\n${memory ?? 'No existing memories'}`;

    if (tokenLimit) {
      const remainingTokens = tokenLimit - currentMemoryTokens;
      memoryStatus = `# Memory Status:
Current memory usage: ${currentMemoryTokens} tokens
Token limit: ${tokenLimit} tokens
Remaining capacity: ${remainingTokens} tokens

# Existing memory:
${memory ?? 'No existing memories'}`;
    }

    const defaultLLMConfig: LLMConfig = {
      provider: Providers.OPENAI,
      model: 'gpt-4.1-mini',
      temperature: 0.4,
      streaming: false,
      disableStreaming: true,
    };

    const finalLLMConfig: ClientOptions = {
      ...defaultLLMConfig,
      ...llmConfig,
      /**
       * Ensure streaming is always disabled for memory processing
       */
      streaming: false,
      disableStreaming: true,
    };

    // Handle GPT-5+ models
    if ('model' in finalLLMConfig && /\bgpt-[5-9]\b/i.test(finalLLMConfig.model ?? '')) {
      // Remove temperature for GPT-5+ models
      delete finalLLMConfig.temperature;

      // Move maxTokens to modelKwargs for GPT-5+ models
      if ('maxTokens' in finalLLMConfig && finalLLMConfig.maxTokens != null) {
        const modelKwargs = (finalLLMConfig as OpenAIClientOptions).modelKwargs ?? {};
        modelKwargs.max_completion_tokens = finalLLMConfig.maxTokens;
        delete finalLLMConfig.maxTokens;
        (finalLLMConfig as OpenAIClientOptions).modelKwargs = modelKwargs;
      }
    }

    const artifactPromises: Promise<TAttachment | null>[] = [];
    const memoryCallback = createMemoryCallback({ res, artifactPromises });
    const customHandlers = {
      [GraphEvents.TOOL_END]: new BasicToolEndHandler(memoryCallback),
    };

    const run = await Run.create({
      runId: messageId,
      graphConfig: {
        type: 'standard',
        llmConfig: finalLLMConfig,
        tools: [memoryTool, deleteMemoryTool],
        instructions,
        additional_instructions: memoryStatus,
        toolEnd: true,
      },
      customHandlers,
      returnContent: true,
    });

    const config = {
      configurable: {
        provider: llmConfig?.provider,
        thread_id: `memory-run-${conversationId}`,
      },
      streamMode: 'values',
      recursionLimit: 3,
      version: 'v2',
    } as const;

    const inputs = {
      messages,
    };
    const content = await run.processStream(inputs, config);
    if (content) {
      logger.debug('Memory Agent processed memory successfully', content);
    } else {
      logger.warn('Memory Agent processed memory but returned no content');
    }
    return await Promise.all(artifactPromises);
  } catch (error) {
    logger.error('Memory Agent failed to process memory', error);
  }
}

export async function createMemoryProcessor({
  res,
  userId,
  messageId,
  memoryMethods,
  conversationId,
  config = {},
}: {
  res: ServerResponse;
  messageId: string;
  conversationId: string;
  userId: string | ObjectId;
  memoryMethods: RequiredMemoryMethods;
  config?: MemoryConfig;
}): Promise<[string, (messages: BaseMessage[]) => Promise<(TAttachment | null)[] | undefined>]> {
  const { validKeys, instructions, llmConfig, tokenLimit } = config;
  const finalInstructions = instructions || getDefaultInstructions(validKeys, tokenLimit);

  const { withKeys, withoutKeys, totalTokens } = await memoryMethods.getFormattedMemories({
    userId,
  });

  return [
    withoutKeys,
    async function (messages: BaseMessage[]): Promise<(TAttachment | null)[] | undefined> {
      try {
        return await processMemory({
          res,
          userId,
          messages,
          validKeys,
          llmConfig,
          messageId,
          tokenLimit,
          conversationId,
          memory: withKeys,
          totalTokens: totalTokens || 0,
          instructions: finalInstructions,
          setMemory: memoryMethods.setMemory,
          deleteMemory: memoryMethods.deleteMemory,
        });
      } catch (error) {
        logger.error('Memory Agent failed to process memory', error);
      }
    },
  ];
}

async function handleMemoryArtifact({
  res,
  data,
  metadata,
}: {
  res: ServerResponse;
  data: ToolEndData;
  metadata?: ToolEndMetadata;
}) {
  const output = data?.output;
  if (!output) {
    return null;
  }

  if (!output.artifact) {
    return null;
  }

  const memoryArtifact = output.artifact[Tools.memory] as MemoryArtifact | undefined;
  if (!memoryArtifact) {
    return null;
  }

  const attachment: Partial<TAttachment> = {
    type: Tools.memory,
    toolCallId: output.tool_call_id,
    messageId: metadata?.run_id ?? '',
    conversationId: metadata?.thread_id ?? '',
    [Tools.memory]: memoryArtifact,
  };
  if (!res.headersSent) {
    return attachment;
  }
  res.write(`event: attachment\ndata: ${JSON.stringify(attachment)}\n\n`);
  return attachment;
}

/**
 * Creates a memory callback for handling memory artifacts
 * @param params - The parameters object
 * @param params.res - The server response object
 * @param params.artifactPromises - Array to collect artifact promises
 * @returns The memory callback function
 */
export function createMemoryCallback({
  res,
  artifactPromises,
}: {
  res: ServerResponse;
  artifactPromises: Promise<Partial<TAttachment> | null>[];
}): ToolEndCallback {
  return async (data: ToolEndData, metadata?: Record<string, unknown>) => {
    const output = data?.output;
    const memoryArtifact = output?.artifact?.[Tools.memory] as MemoryArtifact;
    if (memoryArtifact == null) {
      return;
    }
    artifactPromises.push(
      handleMemoryArtifact({ res, data, metadata }).catch((error) => {
        logger.error('Error processing memory artifact content:', error);
        return null;
      }),
    );
  };
}