costTracker.js

/**
 * @fileoverview Cost tracking module for LangRoute.
 * 
 * This module handles all cost-related calculations and tracking for LLM API requests.
 * It works in conjunction with the token counter to accurately calculate costs
 * based on both input and output tokens, using model-specific pricing from the database.
 * 
 * Features:
 * - Per-model cost calculation
 * - Separate tracking of input and output costs
 * - User cost accumulation
 * - Database-driven pricing configuration
 * 
 * @module costTracker
 * @requires ./tokenCounter
 * @requires ./database
 */

// costTracker.js
const { countTokens } = require('./tokenCounter');
const db = require('./database'); // Import Sequelize models

/**
 * Calculates the cost of a request based on the model and token usage.
 * @param {string} modelName - The name of the model used for the request.
 * @param {number} inputTokens - The number of input tokens used in the request.
 * @param {number} outputTokens - The number of output tokens generated by the request.
 * @returns {object} An object containing the input tokens, output tokens, and total cost.
 */
/**
 * Calculates the total cost of an LLM API request based on token usage.
 * Uses model-specific pricing from the database to calculate costs separately
 * for input and output tokens.
 * 
 * @async
 * @param {string} modelName - The name of the LLM model (e.g., 'gpt-3.5-turbo', 'mistral-small')
 * @param {number} inputTokens - Number of tokens in the input/prompt
 * @param {number} outputTokens - Number of tokens in the model's response
 * @returns {Promise<Object>} Cost breakdown
 * @returns {number} .inputTokens - Number of input tokens used
 * @returns {number} .outputTokens - Number of output tokens used
 * @returns {number} .inputCost - Cost for input tokens in USD
 * @returns {number} .outputCost - Cost for output tokens in USD
 * @returns {number} .totalCost - Total cost of the request in USD
 * @throws {Error} If the model configuration is not found in the database
 */
async function calculateCost(modelName, inputTokens, outputTokens) {
    const modelConfig = await db.LLMModel.findOne({ where: { name: modelName } }); //Use complete model name
    if (!modelConfig) {
        throw new Error(`Model ${modelName} not found in database.`);
    }
    const inputCost = (inputTokens / 1000) * modelConfig.inputCostPer1k;
    const outputCost = (outputTokens / 1000) * modelConfig.outputCostPer1k;

    return {
        inputTokens,
        outputTokens,
        inputCost,
        outputCost,
        totalCost: inputCost + outputCost,
    };
}
/**
 * Updates a user's accumulated cost in the database.
 * This function is called after each successful API request to track spending.
 * 
 * @async
 * @param {Object} user - The user object from the database
 * @param {number} user.totalCost - User's current accumulated cost
 * @param {number} cost - Additional cost to add to the user's total
 * @returns {Promise<void>}
 */
async function updateUserCost(user, cost) {
  user.totalCost += cost;
  await user.save();
}
module.exports = { calculateCost, updateUserCost};