LibreChat/api/app/clients/agents/CustomAgent/outputParser.js

const { ZeroShotAgentOutputParser } = require('langchain/agents');
const { logger } = require('~/config');

class CustomOutputParser extends ZeroShotAgentOutputParser {
  constructor(fields) {
    super(fields);
    this.tools = fields.tools;
    this.longestToolName = '';
    for (const tool of this.tools) {
      if (tool.name.length > this.longestToolName.length) {
        this.longestToolName = tool.name;
      }
    }
    this.finishToolNameRegex = /(?:the\s+)?final\s+answer:\s*/i;
    this.actionValues =
      /(?:Action(?: [1-9])?:) ([\s\S]*?)(?:\n(?:Action Input(?: [1-9])?:) ([\s\S]*?))?$/i;
    this.actionInputRegex = /(?:Action Input(?: *\d*):) ?([\s\S]*?)$/i;
    this.thoughtRegex = /(?:Thought(?: *\d*):) ?([\s\S]*?)$/i;
  }

  getValidTool(text) {
    let result = false;
    for (const tool of this.tools) {
      const { name } = tool;
      const toolIndex = text.indexOf(name);
      if (toolIndex !== -1) {
        result = name;
        break;
      }
    }
    return result;
  }

  checkIfValidTool(text) {
    let isValidTool = false;
    for (const tool of this.tools) {
      const { name } = tool;
      if (text === name) {
        isValidTool = true;
        break;
      }
    }
    return isValidTool;
  }

  async parse(text) {
    const finalMatch = text.match(this.finishToolNameRegex);
    // if (text.includes(this.finishToolName)) {
    //   const parts = text.split(this.finishToolName);
    //   const output = parts[parts.length - 1].trim();
    //   return {
    //     returnValues: { output },
    //     log: text
    //   };
    // }

    if (finalMatch) {
      const output = text.substring(finalMatch.index + finalMatch[0].length).trim();
      return {
        returnValues: { output },
        log: text,
      };
    }

    const match = this.actionValues.exec(text); // old v2

    if (!match) {
      logger.debug(
        '\n\n<----------------------[CustomOutputParser] HIT NO MATCH PARSING ERROR---------------------->\n\n' +
          match,
      );
      const thoughts = text.replace(/[tT]hought:/, '').split('\n');
      // return {
      //   tool: 'self-reflection',
      //   toolInput: thoughts[0],
      //   log: thoughts.slice(1).join('\n')
      // };

      return {
        returnValues: { output: thoughts[0] },
        log: thoughts.slice(1).join('\n'),
      };
    }

    let selectedTool = match?.[1].trim().toLowerCase();

    if (match && selectedTool === 'n/a') {
      logger.debug(
        '\n\n<----------------------[CustomOutputParser] HIT N/A PARSING ERROR---------------------->\n\n' +
          match,
      );
      return {
        tool: 'self-reflection',
        toolInput: match[2]?.trim().replace(/^"+|"+$/g, '') ?? '',
        log: text,
      };
    }

    let toolIsValid = this.checkIfValidTool(selectedTool);
    if (match && !toolIsValid) {
      logger.debug(
        '\n\n<----------------[CustomOutputParser] Tool invalid: Re-assigning Selected Tool---------------->\n\n' +
          match,
      );
      selectedTool = this.getValidTool(selectedTool);
    }

    if (match && !selectedTool) {
      logger.debug(
        '\n\n<----------------------[CustomOutputParser] HIT INVALID TOOL PARSING ERROR---------------------->\n\n' +
          match,
      );
      selectedTool = 'self-reflection';
    }

    if (match && !match[2]) {
      logger.debug(
        '\n\n<----------------------[CustomOutputParser] HIT NO ACTION INPUT PARSING ERROR---------------------->\n\n' +
          match,
      );

      // In case there is no action input, let's double-check if there is an action input in 'text' variable
      const actionInputMatch = this.actionInputRegex.exec(text);
      const thoughtMatch = this.thoughtRegex.exec(text);
      if (actionInputMatch) {
        return {
          tool: selectedTool,
          toolInput: actionInputMatch[1].trim(),
          log: text,
        };
      }

      if (thoughtMatch && !actionInputMatch) {
        return {
          tool: selectedTool,
          toolInput: thoughtMatch[1].trim(),
          log: text,
        };
      }
    }

    if (match && selectedTool.length > this.longestToolName.length) {
      logger.debug(
        '\n\n<----------------------[CustomOutputParser] HIT LONG PARSING ERROR---------------------->\n\n',
      );

      let action, input, thought;
      let firstIndex = Infinity;

      for (const tool of this.tools) {
        const { name } = tool;
        const toolIndex = text.indexOf(name);
        if (toolIndex !== -1 && toolIndex < firstIndex) {
          firstIndex = toolIndex;
          action = name;
        }
      }

      // In case there is no action input, let's double-check if there is an action input in 'text' variable
      const actionInputMatch = this.actionInputRegex.exec(text);
      if (action && actionInputMatch) {
        logger.debug(
          '\n\n<------[CustomOutputParser] Matched Action Input in Long Parsing Error------>\n\n' +
            actionInputMatch,
        );
        return {
          tool: action,
          toolInput: actionInputMatch[1].trim().replaceAll('"', ''),
          log: text,
        };
      }

      if (action) {
        const actionEndIndex = text.indexOf('Action:', firstIndex + action.length);
        const inputText = text
          .slice(firstIndex + action.length, actionEndIndex !== -1 ? actionEndIndex : undefined)
          .trim();
        const inputLines = inputText.split('\n');
        input = inputLines[0];
        if (inputLines.length > 1) {
          thought = inputLines.slice(1).join('\n');
        }
        const returnValues = {
          tool: action,
          toolInput: input,
          log: thought || inputText,
        };

        const inputMatch = this.actionValues.exec(returnValues.log); //new
        if (inputMatch) {
          logger.debug('[CustomOutputParser] inputMatch', inputMatch);
          returnValues.toolInput = inputMatch[1].replaceAll('"', '').trim();
          returnValues.log = returnValues.log.replace(this.actionValues, '');
        }

        return returnValues;
      } else {
        logger.debug('[CustomOutputParser] No valid tool mentioned.', this.tools, text);
        return {
          tool: 'self-reflection',
          toolInput: 'Hypothetical actions: \n"' + text + '"\n',
          log: 'Thought: I need to look at my hypothetical actions and try one',
        };
      }

      // if (action && input) {
      //   logger.debug('Action:', action);
      //   logger.debug('Input:', input);
      // }
    }

    return {
      tool: selectedTool,
      toolInput: match[2]?.trim()?.replace(/^"+|"+$/g, '') ?? '',
      log: text,
    };
  }
}

module.exports = { CustomOutputParser };