/**
 * Token usage tracking and cost estimation service
 */

// Pricing per million tokens (as of Dec 2025)
const MODEL_PRICING = {
  // Claude 4.5 models
  "claude-opus-4-5-20251101": { input: 5.00, output: 25.00 },
  "claude-sonnet-4-5-20250929": { input: 3.00, output: 15.00 },
  "claude-haiku-4-5-20251001": { input: 1.00, output: 5.00 },

  // Claude 4 models
  "claude-opus-4-1-20250805": { input: 15.00, output: 75.00 },
  "claude-sonnet-4-20250514": { input: 3.00, output: 15.00 },

  // Claude 3.7/3.5 models
  "claude-3-7-sonnet-20250219": { input: 3.00, output: 15.00 },
  "claude-3-5-sonnet-20241022": { input: 3.00, output: 15.00 },
  "claude-3-5-haiku-20241022": { input: 0.80, output: 4.00 },

  // Claude 3 models
  "claude-3-opus-20240229": { input: 15.00, output: 75.00 },
  "claude-3-sonnet-20240229": { input: 3.00, output: 15.00 },
  "claude-3-haiku-20240307": { input: 0.25, output: 1.25 },

  // Cloudflare Workers AI models (approximate - based on neuron costs)
  "@cf/mistralai/mistral-small-3.1-24b-instruct": { input: 0.30, output: 0.30 },
  "@hf/nousresearch/hermes-2-pro-mistral-7b": { input: 0.10, output: 0.10 },
  "@cf/meta/llama-3.3-70b-instruct-fp8-fast": { input: 0.20, output: 0.20 },
  "@cf/meta/llama-3.1-70b-instruct": { input: 0.20, output: 0.20 },
  "@cf/meta/llama-3.1-8b-instruct": { input: 0.05, output: 0.05 },
  "@cf/deepseek-ai/deepseek-r1-distill-qwen-32b": { input: 0.15, output: 0.15 },
  "@cf/qwen/qwen2.5-coder-32b-instruct": { input: 0.15, output: 0.15 },
};

// Cache pricing multipliers
const CACHE_WRITE_MULTIPLIER = 1.25;  // 25% more expensive to write cache
const CACHE_READ_MULTIPLIER = 0.10;   // 90% cheaper to read from cache

// In-memory storage for usage tracking
const sessionUsage = new Map();
const globalUsage = {
  totalInputTokens: 0,
  totalOutputTokens: 0,
  totalCacheCreationTokens: 0,
  totalCacheReadTokens: 0,
  totalCost: 0,
  requestCount: 0,
  byModel: {},
  startTime: Date.now()
};

/**
 * Get pricing for a model, with fallback to sonnet pricing
 */
function getModelPricing(model) {
  // Try exact match first
  if (MODEL_PRICING[model]) {
    return MODEL_PRICING[model];
  }

  // Try to match by model family
  if (model.includes("opus")) {
    return MODEL_PRICING["claude-opus-4-5-20251101"];
  }
  if (model.includes("haiku")) {
    return MODEL_PRICING["claude-haiku-4-5-20251001"];
  }

  // Cloudflare models - default to cheap pricing
  if (model.startsWith("@cf/") || model.startsWith("@hf/")) {
    return { input: 0.10, output: 0.10 };
  }

  // Default to sonnet pricing
  return MODEL_PRICING["claude-sonnet-4-5-20250929"];
}

/**
 * Calculate cost for a request
 */
function calculateCost(model, usage) {
  const pricing = getModelPricing(model);
  const perMillionDivisor = 1_000_000;

  let cost = 0;

  // Standard input tokens
  const standardInputTokens = (usage.input_tokens || 0) - (usage.cache_read_input_tokens || 0);
  cost += (standardInputTokens / perMillionDivisor) * pricing.input;

  // Cache read tokens (90% cheaper)
  if (usage.cache_read_input_tokens) {
    cost += (usage.cache_read_input_tokens / perMillionDivisor) * pricing.input * CACHE_READ_MULTIPLIER;
  }

  // Cache creation tokens (25% more expensive)
  if (usage.cache_creation_input_tokens) {
    cost += (usage.cache_creation_input_tokens / perMillionDivisor) * pricing.input * CACHE_WRITE_MULTIPLIER;
  }

  // Output tokens
  cost += ((usage.output_tokens || 0) / perMillionDivisor) * pricing.output;

  return cost;
}

/**
 * Track usage for a request
 * @param {string} sessionId - Session identifier
 * @param {string} model - Model used
 * @param {object} usage - Token usage from API response
 * @param {object} content - Optional input/output content for detailed tracking
 * @param {string} content.inputText - User input text
 * @param {string} content.outputText - Assistant output text
 * @param {array} content.toolCalls - Tool calls made
 */
export function trackUsage(sessionId, model, usage, content = {}) {
  if (!usage) return null;

  const cost = calculateCost(model, usage);

  // Truncate text for storage (keep first 500 chars)
  const truncate = (text, maxLen = 500) => {
    if (!text) return null;
    return text.length > maxLen ? text.substring(0, maxLen) + '...' : text;
  };

  const usageRecord = {
    timestamp: Date.now(),
    model,
    inputTokens: usage.input_tokens || 0,
    outputTokens: usage.output_tokens || 0,
    cacheCreationTokens: usage.cache_creation_input_tokens || 0,
    cacheReadTokens: usage.cache_read_input_tokens || 0,
    cost,
    inputText: truncate(content.inputText),
    outputText: truncate(content.outputText),
    toolCalls: content.toolCalls || []
  };

  // Update session usage
  if (sessionId) {
    if (!sessionUsage.has(sessionId)) {
      sessionUsage.set(sessionId, {
        totalInputTokens: 0,
        totalOutputTokens: 0,
        totalCacheCreationTokens: 0,
        totalCacheReadTokens: 0,
        totalCost: 0,
        requestCount: 0,
        requests: [],
        startTime: Date.now()
      });
    }

    const session = sessionUsage.get(sessionId);
    session.totalInputTokens += usageRecord.inputTokens;
    session.totalOutputTokens += usageRecord.outputTokens;
    session.totalCacheCreationTokens += usageRecord.cacheCreationTokens;
    session.totalCacheReadTokens += usageRecord.cacheReadTokens;
    session.totalCost += cost;
    session.requestCount += 1;
    session.requests.push(usageRecord);

    // Keep only last 100 requests per session to limit memory
    if (session.requests.length > 100) {
      session.requests.shift();
    }
  }

  // Update global usage
  globalUsage.totalInputTokens += usageRecord.inputTokens;
  globalUsage.totalOutputTokens += usageRecord.outputTokens;
  globalUsage.totalCacheCreationTokens += usageRecord.cacheCreationTokens;
  globalUsage.totalCacheReadTokens += usageRecord.cacheReadTokens;
  globalUsage.totalCost += cost;
  globalUsage.requestCount += 1;

  // Track by model
  if (!globalUsage.byModel[model]) {
    globalUsage.byModel[model] = {
      inputTokens: 0,
      outputTokens: 0,
      cost: 0,
      requestCount: 0
    };
  }
  globalUsage.byModel[model].inputTokens += usageRecord.inputTokens;
  globalUsage.byModel[model].outputTokens += usageRecord.outputTokens;
  globalUsage.byModel[model].cost += cost;
  globalUsage.byModel[model].requestCount += 1;

  return usageRecord;
}

/**
 * Get usage for a session
 */
export function getSessionUsage(sessionId) {
  return sessionUsage.get(sessionId) || null;
}

/**
 * Get global usage stats
 */
export function getGlobalUsage() {
  return {
    ...globalUsage,
    uptime: Date.now() - globalUsage.startTime
  };
}

/**
 * Format cost as currency string
 */
export function formatCost(cost) {
  return `$${cost.toFixed(6)}`;
}

/**
 * Clear session usage (call when session ends)
 */
export function clearSessionUsage(sessionId) {
  sessionUsage.delete(sessionId);
}

/**
 * Get a formatted usage summary for logging
 */
export function getUsageSummary(usageRecord) {
  if (!usageRecord) return "No usage data";

  return [
    `Input: ${usageRecord.inputTokens}`,
    `Output: ${usageRecord.outputTokens}`,
    usageRecord.cacheReadTokens ? `Cache read: ${usageRecord.cacheReadTokens}` : null,
    usageRecord.cacheCreationTokens ? `Cache write: ${usageRecord.cacheCreationTokens}` : null,
    `Cost: ${formatCost(usageRecord.cost)}`
  ].filter(Boolean).join(" | ");
}