// MetricsAggregator: accumulates per-endpoint counters for periodic flush.

#pragma once

#include <cstdint>

#include <functional>

#include <string>

#include <unordered_map>

// Per-endpoint counters accumulated within one flush window.

struct EndpointStats {

  uint8_t     hitCount;  // request hits since last flush

  uint32_t    errorCount; // error responses since last flush

};

// Callback type invoked by flush() for each endpoint with non-zero counters.

using ReportFn = std::function<void(const std::string&, uint32_t, uint32_t)>;

// Aggregates request hits and errors per endpoint.

// Not thread-safe; callers must serialise access.

class MetricsAggregator {

public:

  // Parameters:

  //   reporter - callback invoked once per endpoint during flush

  // Returns: new MetricsAggregator with empty counters

  explicit MetricsAggregator(ReportFn reporter);

  // Records one request event for the given endpoint.

  // Parameters:

  //   endpoint - request path to credit

  //   isError  - true if the response was an error (4xx/5xx)

  // Returns: void; counters for endpoint are incremented

  void record(const std::string& endpoint, bool isError);

  // Flushes accumulated counters to the reporter and resets them.

  // Parameters: none

  // Returns: void; all per-endpoint counters are zero after this call

  void flush();

private:

  std::unordered_map<std::string, EndpointStats> counters_; // per-endpoint accumulators

  ReportFn reporter_; // callback used to ship counters to the backend

};