#include "tlbmc/pacemaker/pacemaker.h"

#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <memory>
#include <string>
#include <utility>

#include "absl/functional/any_invocable.h"
#include "absl/log/log.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/ascii.h"
#include "absl/strings/match.h"
#include "absl/strings/numbers.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/str_format.h"
#include "absl/synchronization/mutex.h"
#include "absl/time/clock.h"
#include "absl/time/time.h"
#include "g3/macros.h"
#include "nlohmann/json.hpp"

namespace milotic_tlbmc {

namespace {

constexpr const int kMaxConsecutiveRestartAttempts = 10;
constexpr const char* kProcessName = "bmcweb";
constexpr const int kExpectedListeningPort = 443;
constexpr const int kMemoryUsageThreshold = 300 * 1024 * 1024;  // 300MB
constexpr const char* kIsActiveCommand = "systemctl is-active %s";
constexpr const char* kActiveStatus = "active";
constexpr const char* kRestartCommand = "systemctl restart %s";
constexpr const char* kIsListeningCommand = "ss -tulpn | grep %d";
constexpr const char* kGetMemoryUsageCommand =
    "cat /proc/%d/status | grep VmRSS | awk '{print $2}'";
constexpr const char* kGetPidCommand =
    "systemctl status %s | grep 'Main PID:' | awk '{print $3}'";
constexpr const char* kGetCpuUsageCommand =
    "top -n1 | grep %s -i | awk '{print int($8)}'";
constexpr const char* kGetActiveEnterTimestampMonotonic =
    "systemctl show --property=ActiveEnterTimestampMonotonic %s | awk -F'=' "
    "'{print $2}'";
constexpr const int kMaxRecentDataPoints = 12;

}  // namespace

nlohmann::json Pacemaker::ErrorInfo::ToJson() const {
  auto error_type_to_string = [](ErrorType type) -> std::string {
    switch (type) {
      case ErrorType::kUnknown:
        return "Unknown";
      case ErrorType::kServiceInactive:
        return "ServiceInactive";
      case ErrorType::kPortNotListening:
        return "PortNotListening";
      case ErrorType::kMemoryUsageAboveThreshold:
        return "MemoryUsageAboveThreshold";
      default:
        return "Unknown";
    }
  };

  nlohmann::json json;
  json["type"] = error_type_to_string(type);
  json["timestamp"] = absl::FormatTime(timestamp);
  return json;
}

nlohmann::json Pacemaker::MonitoredData::ToJson() const {
  nlohmann::json json;
  // Get the last kMaxRecentDataPoints memory usage data points.
  auto it = memory_usage_bytes.rbegin();
  for (int i = 0; i < kMaxRecentDataPoints && it != memory_usage_bytes.rend();
       ++i, ++it) {
    json["MemoryUsageRecentToOldest"].push_back(*it);
  }
  // Get the last kMaxRecentDataPoints error data points.
  auto it_error = restart_log.rbegin();
  for (int i = 0; i < kMaxRecentDataPoints && it_error != restart_log.rend();
       ++i, ++it_error) {
    json["ErrorsRecentToOldest"].push_back(it_error->ToJson());
  }
  json["CpuUsage"] = cpu_usage;
  json["MemoryUsage"] =
      memory_usage_bytes.empty() ? -1 : memory_usage_bytes.back();
  json["LastActiveTimestamp"] = last_active_timestamp;
  json["LastResetTime"] = absl::FormatTime(last_reset_time);
  json["RestartTriggered"] = restart_triggered;
  json["Pid"] = pid;
  json["ConsecutiveRestartAttempts"] = consecutive_restart_attempts;
  return json;
}

absl::StatusOr<std::string> ShellCommandExecutor::Execute(
    const std::string& command) {
  FILE* pipe = popen(command.c_str(), "r");
  if (pipe == nullptr) {
    return absl::InternalError(
        absl::StrCat("Error: Failed to execute command: ", command));
  }
  std::string result;
  char* line = nullptr;
  size_t len = 0;
  ssize_t read;

  while ((read = getline(&line, &len, pipe)) != -1) {
    result.append(line, static_cast<std::string::size_type>(read));
  }

  free(line);
  pclose(pipe);
  return result;
}

absl::StatusOr<bool> Pacemaker::IsServiceActive(
    const std::string& service_name) const {
  LOG(INFO) << "Checking if service " << service_name << " is active.";
  ECCLESIA_ASSIGN_OR_RETURN(
      std::string output, shell_command_executor_->Execute(
                              absl::StrFormat(kIsActiveCommand, service_name)));
  absl::StripAsciiWhitespace(&output);
  // Compare string
  if (!absl::EqualsIgnoreCase(output, "active")) {
    LOG(ERROR) << "Service " << service_name << " is not active."
               << " status is " << output << " instead of " << kActiveStatus;
    return false;
  }
  return true;
}

absl::StatusOr<bool> Pacemaker::IsPortListening(int port) const {
  LOG(INFO) << "Checking if port " << port << " is listening.";
  ECCLESIA_ASSIGN_OR_RETURN(std::string output,
                            shell_command_executor_->Execute(
                                absl::StrFormat(kIsListeningCommand, port)));
  return !output.empty();
}

absl::StatusOr<int> Pacemaker::GetMemoryUsage(int pid) const {
  LOG(INFO) << "Getting memory usage for pid " << pid;
  ECCLESIA_ASSIGN_OR_RETURN(std::string output,
                            shell_command_executor_->Execute(
                                absl::StrFormat(kGetMemoryUsageCommand, pid)));
  int memory_usage;
  if (!absl::SimpleAtoi(output, &memory_usage)) {
    return absl::InternalError(
        absl::StrCat("Error: Failed to parse memory usage: ", output));
  }
  return memory_usage;
}

absl::StatusOr<int> Pacemaker::GetCpuUsage(
    const std::string& process_name) const {
  LOG(INFO) << "Getting CPU usage for process " << process_name;
  ECCLESIA_ASSIGN_OR_RETURN(std::string output,
                            shell_command_executor_->Execute(absl::StrFormat(
                                kGetCpuUsageCommand, process_name)));
  int cpu_usage = -1;
  if (output.empty()) {
    return cpu_usage;
  }
  if (!absl::SimpleAtoi(output, &cpu_usage)) {
    return absl::InternalError(
        absl::StrCat("Error: Failed to parse CPU usage: ", output));
  }
  return cpu_usage;
}

absl::StatusOr<int64_t> Pacemaker::GetLastActiveTimestamp(
    const std::string& process_name) const {
  LOG(INFO) << "Getting last active timestamp for process " << process_name;
  ECCLESIA_ASSIGN_OR_RETURN(
      std::string output,
      shell_command_executor_->Execute(
          absl::StrFormat(kGetActiveEnterTimestampMonotonic, process_name)));
  int64_t last_active_timestamp;
  if (!absl::SimpleAtoi(output, &last_active_timestamp)) {
    return absl::InternalError(
        absl::StrCat("Error: Failed to parse last reset time: ", output));
  }
  return last_active_timestamp;
}

absl::Status Pacemaker::RestartService(const std::string& service_name) {
  LOG(ERROR) << "Restarting service " << service_name;
  {
    absl::MutexLock lock(&mutex_);
    if (monitored_data_.restart_triggered) {
      if (monitored_data_.consecutive_restart_attempts >=
          kMaxConsecutiveRestartAttempts) {
        LOG(ERROR) << "Restart attempts exceeded the limit of "
                   << kMaxConsecutiveRestartAttempts;
        return absl::InternalError(
            absl::StrCat("Error: Restart attempts exceeded the limit of ",
                         kMaxConsecutiveRestartAttempts));
      }
      ++monitored_data_.consecutive_restart_attempts;
    }
    monitored_data_.restart_triggered = true;
    monitored_data_.last_reset_time = absl::Now();
  }
  ECCLESIA_ASSIGN_OR_RETURN(
      std::string output, shell_command_executor_->Execute(
                              absl::StrFormat(kRestartCommand, service_name)));
  return absl::OkStatus();
}

// Get PID of the process.
absl::StatusOr<int> Pacemaker::GetPid(const std::string& process_name) const {
  LOG(INFO) << "Getting PID for process " << process_name;
  ECCLESIA_ASSIGN_OR_RETURN(std::string output,
                            shell_command_executor_->Execute(
                                absl::StrFormat(kGetPidCommand, process_name)));
  int pid = -1;
  if (output.empty()) {
    return absl::InternalError(
        absl::StrCat("Error: Main PID not found for service: ", process_name));
  }
  // Trim leading and trailing whitespace, including newlines.
  output = std::string(absl::StripAsciiWhitespace(output));

  if (absl::SimpleAtoi(output, &pid)) {
    return pid;
  }
  return absl::InternalError(
      absl::StrCat("Error: Invalid PID found in systemctl output: ", output,
                   " for service: ", process_name));
}

void Pacemaker::RecordError(ErrorType type) {
  absl::MutexLock lock(&mutex_);
  // If the error type is unknown, we can't determine the timestamp.
  // So we just record the error and continue.
  if (type == ErrorType::kUnknown) {
    monitored_data_.restart_log.push_back({type, absl::InfinitePast()});
    return;
  }
  ErrorInfo error_info = {type, absl::Now()};
  LOG(ERROR) << "Restart required due to Error:\n"
             << error_info.ToJson().dump(2);
  monitored_data_.restart_log.push_back(error_info);
}

absl::Status Pacemaker::PerformChecks() {
  bool unknown_restart_detected = false;
  ECCLESIA_ASSIGN_OR_RETURN(bool is_active, IsServiceActive(kProcessName));
  ECCLESIA_ASSIGN_OR_RETURN(bool is_listening,
                            IsPortListening(kExpectedListeningPort));
  ECCLESIA_ASSIGN_OR_RETURN(int pid, GetPid(kProcessName));
  ECCLESIA_ASSIGN_OR_RETURN(int cpu_usage, GetCpuUsage(kProcessName));
  int memory_usage = -1;
  if (pid > 0) {
    ECCLESIA_ASSIGN_OR_RETURN(memory_usage, GetMemoryUsage(pid));
  }

  absl::StatusOr<int64_t> last_active_timestamp =
      GetLastActiveTimestamp(kProcessName);
  if (!last_active_timestamp.ok()) {
    LOG(ERROR) << "Failed to get last active timestamp: "
               << last_active_timestamp.status();
  }

  // Update monitored data.
  {
    absl::MutexLock lock(&mutex_);
    monitored_data_.memory_usage_bytes.push_back(memory_usage);
    monitored_data_.cpu_usage = cpu_usage;
    monitored_data_.pid = pid;

    // Check if the process was restarted outside of pacemaker.
    if (last_active_timestamp.ok()) {
      // We check if the `last_active_timestamp` we got from systemctl
      // is different from the one we got from the previous run and if the
      // process was not restarted by pacemaker.
      // If the timestamps are different, it means the process was restarted
      // outside of pacemaker and we should record it as an unknown error.
      if (monitored_data_.last_active_timestamp != -1 &&
          *last_active_timestamp != monitored_data_.last_active_timestamp &&
          !monitored_data_.restart_triggered) {
        LOG(INFO) << "Process " << kProcessName
                  << " was restarted outside of pacemaker.";
        unknown_restart_detected = true;
      }
      monitored_data_.last_active_timestamp = *last_active_timestamp;
    }
  }

  if (unknown_restart_detected) {
    RecordError(ErrorType::kUnknown);
  }

  if (!is_active) {
    RecordError(ErrorType::kServiceInactive);
    ECCLESIA_RETURN_IF_ERROR(RestartService(kProcessName));
    return absl::OkStatus();
  }

  if (!is_listening) {
    LOG(ERROR) << "Process " << kProcessName << " is not listening on port "
               << kExpectedListeningPort;
    RecordError(ErrorType::kPortNotListening);
    ECCLESIA_RETURN_IF_ERROR(RestartService(kProcessName));
    return absl::OkStatus();
  }

  if (memory_usage > kMemoryUsageThreshold) {
    LOG(ERROR) << "Process " << kProcessName << " memory usage is "
               << memory_usage << " bytes which is more than the threshold of "
               << kMemoryUsageThreshold;
    RecordError(ErrorType::kMemoryUsageAboveThreshold);
    ECCLESIA_RETURN_IF_ERROR(RestartService(kProcessName));
    return absl::OkStatus();
  }

  // If we reach here, it means all checks passed.
  // Reset the restart triggered and consecutive restart attempts counters.
  absl::MutexLock lock(&mutex_);
  monitored_data_.restart_triggered = false;
  monitored_data_.consecutive_restart_attempts = 0;
  return absl::OkStatus();
}

nlohmann::json Pacemaker::GetMonitoringData() const {
  nlohmann::json json;
  {
    absl::MutexLock lock(&mutex_);
    json = monitored_data_.ToJson();
  }
  json["PacemakerSchedulerStats"] = scheduler_.ToJson();
  return json;
}

Pacemaker::Pacemaker(
    absl::Duration interval,
    std::unique_ptr<ShellCommandExecutor> shell_command_executor)
    : shell_command_executor_(std::move(shell_command_executor)) {
  scheduler_.RunAndScheduleAsync(
      [this](absl::AnyInvocable<void()> OnDone) {
        if (absl::Status status = PerformChecks(); !status.ok()) {
          LOG(ERROR) << "Failed to perform checks: " << status;
        } else {
          // Dump the monitoring data to the syslog periodically.
          LOG(WARNING) << "tlBMC Health stats:\n"
                       << GetMonitoringData().dump(2);
        }
        OnDone();
      },
      interval);
}

}  // namespace milotic_tlbmc