/*
  Dynagate config manager, CSV parser, and utilities (C++20 port)
  Created by Luxferre in 2026, released into the public domain
*/

#ifndef _DARWIN_C_SOURCE
#define _DARWIN_C_SOURCE
#endif

#include "dynagate.hpp"

#include <algorithm>
#include <cctype>
#include <cerrno>
#include <cstdarg>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <fstream>
#include <sstream>
#include <thread>
#include <unordered_set>

#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

namespace {

std::mutex g_log_mu;

std::string run_shell_command(const std::string &command, int &exit_status) {
  exit_status = -1;
  int pipefd[2];
  if (pipe(pipefd) != 0) {
    return "pipe() failed: " + std::string(std::strerror(errno));
  }

  pid_t pid = fork();
  if (pid < 0) {
    close(pipefd[0]);
    close(pipefd[1]);
    return "fork() failed: " + std::string(std::strerror(errno));
  }

  if (pid == 0) {
    close(pipefd[0]);
    dup2(pipefd[1], STDOUT_FILENO);
    dup2(pipefd[1], STDERR_FILENO);
    close(pipefd[1]);
    execl("/bin/sh", "sh", "-c", command.c_str(), static_cast<char *>(nullptr));
    _exit(127);
  }

  close(pipefd[1]);
  std::string output;
  char buf[4096];
  for (;;) {
    ssize_t n = read(pipefd[0], buf, sizeof(buf));
    if (n > 0) {
      output.append(buf, static_cast<size_t>(n));
    } else if (n == 0) {
      break;
    } else if (errno != EINTR) {
      break;
    }
  }
  close(pipefd[0]);

  int status = 0;
  while (waitpid(pid, &status, 0) < 0) {
    if (errno != EINTR) {
      break;
    }
  }
  if (WIFEXITED(status)) {
    exit_status = WEXITSTATUS(status);
  } else if (WIFSIGNALED(status)) {
    exit_status = 128 + WTERMSIG(status);
  }
  return output;
}

} // namespace

void log_msg(const char *fmt, ...) {
  std::lock_guard<std::mutex> lock(g_log_mu);

  std::time_t now = std::time(nullptr);
  struct tm tm_now;
  localtime_r(&now, &tm_now);
  char time_buf[32];
  std::strftime(time_buf, sizeof(time_buf), "%Y/%m/%d %H:%M:%S", &tm_now);

  char msg_buf[2048];
  va_list ap;
  va_start(ap, fmt);
  std::vsnprintf(msg_buf, sizeof(msg_buf), fmt, ap);
  va_end(ap);

  std::fprintf(stderr, "%s %s\n", time_buf, msg_buf);
  std::fflush(stderr);
}

std::string str_trim(std::string_view sv) {
  size_t start = 0;
  while (start < sv.size() &&
         std::isspace(static_cast<unsigned char>(sv[start]))) {
    ++start;
  }
  size_t end = sv.size();
  while (end > start &&
         std::isspace(static_cast<unsigned char>(sv[end - 1]))) {
    --end;
  }
  return std::string(sv.substr(start, end - start));
}

std::string str_to_lower(std::string_view sv) {
  std::string out(sv);
  std::transform(out.begin(), out.end(), out.begin(), [](unsigned char c) {
    return static_cast<char>(std::tolower(c));
  });
  return out;
}

bool str_iequals(std::string_view a, std::string_view b) {
  if (a.size() != b.size()) {
    return false;
  }
  for (size_t i = 0; i < a.size(); ++i) {
    if (std::tolower(static_cast<unsigned char>(a[i])) !=
        std::tolower(static_cast<unsigned char>(b[i]))) {
      return false;
    }
  }
  return true;
}

void HeaderList::add(std::string_view key, std::string_view value) {
  items.emplace_back(std::string(key), std::string(value));
}

void HeaderList::set(std::string_view key, std::string_view value) {
  del(key);
  items.emplace_back(std::string(key), std::string(value));
}

void HeaderList::del(std::string_view key) {
  items.erase(
    std::remove_if(items.begin(), items.end(), [&](const auto &kv) {
      return str_iequals(kv.first, key);
    }),
    items.end());
}

std::string HeaderList::get(std::string_view key) const {
  for (const auto &kv : items) {
    if (str_iequals(kv.first, key)) {
      return kv.second;
    }
  }
  return "";
}

std::vector<std::string> HeaderList::values(std::string_view key) const {
  std::vector<std::string> res;
  for (const auto &kv : items) {
    if (str_iequals(kv.first, key)) {
      res.push_back(kv.second);
    }
  }
  return res;
}

bool parse_csv(std::string_view content,
               std::vector<std::vector<std::string>> &rows,
               std::string *err_out) {
  rows.clear();
  size_t i = 0;
  const size_t n = content.size();

  while (i < n) {
    // Skip empty lines (matching Go encoding/csv behavior)
    if (content[i] == '\n') {
      ++i;
      continue;
    }
    if (content[i] == '\r' && i + 1 < n && content[i + 1] == '\n') {
      i += 2;
      continue;
    }

    std::vector<std::string> row;
    bool line_done = false;

    while (!line_done) {
      std::string field;
      if (i < n && content[i] == '"') {
        // Quoted field
        ++i;
        bool closed = false;
        while (i < n) {
          if (content[i] == '"') {
            if (i + 1 < n && content[i + 1] == '"') {
              field.push_back('"');
              i += 2;
            } else {
              ++i;
              closed = true;
              break;
            }
          } else {
            if (content[i] == '\r' && i + 1 < n && content[i + 1] == '\n') {
              field.push_back('\n');
              i += 2;
            } else {
              field.push_back(content[i]);
              ++i;
            }
          }
        }
        if (!closed) {
          if (err_out) {
            *err_out = "parse error: bare or unclosed \" in quoted-field";
          }
          return false;
        }
        if (i < n) {
          if (content[i] == ',') {
            row.push_back(std::move(field));
            ++i;
            if (i == n || content[i] == '\n' ||
                (content[i] == '\r' && i + 1 < n && content[i + 1] == '\n')) {
              row.emplace_back("");
              if (i < n && content[i] == '\r') {
                i += 2;
              } else if (i < n && content[i] == '\n') {
                ++i;
              }
              line_done = true;
            }
          } else if (content[i] == '\n') {
            row.push_back(std::move(field));
            ++i;
            line_done = true;
          } else if (content[i] == '\r' && i + 1 < n &&
                     content[i + 1] == '\n') {
            row.push_back(std::move(field));
            i += 2;
            line_done = true;
          } else {
            if (err_out) {
              *err_out = "parse error: extraneous or missing \" in quoted-field";
            }
            return false;
          }
        } else {
          row.push_back(std::move(field));
          line_done = true;
        }
      } else {
        // Unquoted field
        while (i < n && content[i] != ',' && content[i] != '\n' &&
               !(content[i] == '\r' && i + 1 < n && content[i + 1] == '\n')) {
          if (content[i] == '"') {
            if (err_out) {
              *err_out = "parse error: bare \" in non-quoted-field";
            }
            return false;
          }
          field.push_back(content[i]);
          ++i;
        }
        row.push_back(std::move(field));
        if (i < n && content[i] == ',') {
          ++i;
          if (i == n || content[i] == '\n' ||
              (content[i] == '\r' && i + 1 < n && content[i + 1] == '\n')) {
            row.emplace_back("");
            if (i < n && content[i] == '\r') {
              i += 2;
            } else if (i < n && content[i] == '\n') {
              ++i;
            }
            line_done = true;
          }
        } else {
          if (i < n && content[i] == '\r' && i + 1 < n &&
              content[i + 1] == '\n') {
            i += 2;
          } else if (i < n && content[i] == '\n') {
            ++i;
          }
          line_done = true;
        }
      }
    }

    rows.push_back(std::move(row));
  }

  return true;
}

std::vector<std::string> parse_auth_tokens(std::string_view content) {
  std::vector<std::string> tokens;
  size_t pos = 0;
  while (pos <= content.size()) {
    size_t nl = content.find('\n', pos);
    std::string_view line = (nl == std::string_view::npos)
                              ? content.substr(pos)
                              : content.substr(pos, nl - pos);
    std::string token = str_trim(line);
    if (!token.empty()) {
      tokens.push_back(std::move(token));
    }
    if (nl == std::string_view::npos) {
      break;
    }
    pos = nl + 1;
  }
  return tokens;
}

ConfigManager::ConfigManager(std::string file_path)
  : file_path_(std::move(file_path)) {
  std::string err;
  if (!load(&err)) {
    log_msg(
      "Initial configuration load failed or file not found (will retry on change): %s",
      err.c_str());
  }
}

ConfigManager::ConfigManager(std::vector<ModelConfig> configs,
                             std::vector<std::string> unique_models)
  : configs_(std::move(configs)), unique_models_(std::move(unique_models)) {}

bool ConfigManager::load(std::string *err_out) {
  std::error_code ec;
  auto mod_time = std::filesystem::last_write_time(file_path_, ec);
  if (ec) {
    if (err_out) {
      *err_out = ec.message();
    }
    return false;
  }
  auto fsize = std::filesystem::file_size(file_path_, ec);
  if (ec) {
    if (err_out) {
      *err_out = ec.message();
    }
    return false;
  }

  std::ifstream ifs(file_path_, std::ios::binary);
  if (!ifs.is_open()) {
    if (err_out) {
      *err_out = "failed to open " + file_path_;
    }
    return false;
  }

  std::ostringstream oss;
  oss << ifs.rdbuf();
  std::string content = oss.str();

  std::vector<std::vector<std::string>> rows;
  if (!parse_csv(content, rows, err_out)) {
    return false;
  }

  std::vector<ModelConfig> configs;
  if (rows.empty()) {
    update(std::move(configs), mod_time, fsize, true);
    return true;
  }

  // Detect header row
  bool has_header = false;
  const auto &first_row = rows[0];
  for (const auto &col : first_row) {
    std::string col_lower = str_to_lower(str_trim(col));
    if (col_lower == "model" || col_lower == "key" || col_lower == "endpoint") {
      has_header = true;
      break;
    }
  }

  size_t start_idx = 0;
  int model_idx = 0;
  int key_idx = 1;
  int endpoint_idx = 2;
  int extra_idx = -1;

  if (has_header) {
    start_idx = 1;
    model_idx = -1;
    key_idx = -1;
    endpoint_idx = -1;
    extra_idx = -1;
    for (size_t i = 0; i < first_row.size(); ++i) {
      std::string col_lower = str_to_lower(str_trim(first_row[i]));
      if (col_lower == "model") {
        model_idx = static_cast<int>(i);
      } else if (col_lower == "key") {
        key_idx = static_cast<int>(i);
      } else if (col_lower == "endpoint") {
        endpoint_idx = static_cast<int>(i);
      } else if (col_lower == "extra") {
        extra_idx = static_cast<int>(i);
      }
    }
    if (model_idx == -1) {
      model_idx = 0;
    }
    if (key_idx == -1) {
      key_idx = 1;
    }
    if (endpoint_idx == -1) {
      endpoint_idx = 2;
    }
  } else {
    start_idx = 0;
  }

  for (size_t i = start_idx; i < rows.size(); ++i) {
    const auto &row = rows[i];
    int max_idx = std::max({model_idx, key_idx, endpoint_idx});
    if (static_cast<int>(row.size()) <= max_idx) {
      continue;
    }

    std::string m = str_trim(row[static_cast<size_t>(model_idx)]);
    std::string k = str_trim(row[static_cast<size_t>(key_idx)]);
    std::string ep = str_trim(row[static_cast<size_t>(endpoint_idx)]);

    if (m.empty() || k.empty() || ep.empty()) {
      continue;
    }

    std::string extra;
    if (has_header) {
      if (extra_idx != -1 && static_cast<int>(row.size()) > extra_idx) {
        extra = str_trim(row[static_cast<size_t>(extra_idx)]);
      }
    } else {
      if (row.size() > 3) {
        extra = str_trim(row[3]);
      }
    }

    configs.push_back(ModelConfig{
      std::move(m),
      std::move(k),
      std::move(ep),
      std::move(extra),
    });
  }

  size_t count = configs.size();
  update(std::move(configs), mod_time, fsize, true);
  log_msg("Loaded %zu model configurations from %s", count, file_path_.c_str());
  return true;
}

void ConfigManager::update(std::vector<ModelConfig> configs,
                           std::filesystem::file_time_type mod_time,
                           std::uintmax_t size,
                           bool has_stat) {
  std::unique_lock<std::shared_mutex> lock(mu_);

  configs_ = std::move(configs);
  last_mod_time_ = mod_time;
  last_size_ = size;
  has_stat_ = has_stat;

  std::vector<std::string> unique_models;
  std::unordered_set<std::string> seen;
  for (const auto &cfg : configs_) {
    if (seen.insert(cfg.model).second) {
      unique_models.push_back(cfg.model);
    }
  }
  unique_models_ = std::move(unique_models);
}

std::vector<ModelConfig> ConfigManager::get_configs() const {
  std::shared_lock<std::shared_mutex> lock(mu_);
  return configs_;
}

std::vector<std::string> ConfigManager::get_unique_models() const {
  std::shared_lock<std::shared_mutex> lock(mu_);
  return unique_models_;
}

void ConfigManager::watch(std::atomic<bool> &stop_flag) {
  while (!stop_flag.load()) {
    for (int i = 0; i < 20 && !stop_flag.load(); ++i) {
      std::this_thread::sleep_for(std::chrono::milliseconds(50));
    }
    if (stop_flag.load()) {
      return;
    }

    std::error_code ec;
    auto mod_time = std::filesystem::last_write_time(file_path_, ec);
    if (ec) {
      continue;
    }
    auto fsize = std::filesystem::file_size(file_path_, ec);
    if (ec) {
      continue;
    }

    bool changed = false;
    {
      std::shared_lock<std::shared_mutex> lock(mu_);
      if (!has_stat_ || mod_time > last_mod_time_ || fsize != last_size_) {
        changed = true;
      }
    }

    if (changed) {
      log_msg("Detected changes in %s, reloading...", file_path_.c_str());
      std::string err;
      if (!load(&err)) {
        log_msg("Error reloading configuration: %s", err.c_str());
      } else {
        log_msg("Configuration reloaded successfully");
      }
    }
  }
}

void start_csv_updater(std::atomic<bool> &stop_flag,
                       const std::string &command,
                       std::chrono::milliseconds interval) {
  auto run_updater = [&]() {
    log_msg("Running CSV updater command: %s", command.c_str());
    int exit_status = 0;
    std::string output = run_shell_command(command, exit_status);
    if (exit_status != 0) {
      std::string trimmed = str_trim(output);
      log_msg("CSV updater command failed: exit status %d, output: \"%s\"",
              exit_status, trimmed.c_str());
    } else {
      log_msg("CSV updater command completed successfully");
    }
  };

  // Run once immediately at startup
  run_updater();

  while (!stop_flag.load()) {
    auto start = std::chrono::steady_clock::now();
    while (!stop_flag.load()) {
      auto elapsed = std::chrono::steady_clock::now() - start;
      if (elapsed >= interval) {
        break;
      }
      auto remaining = std::chrono::duration_cast<std::chrono::milliseconds>(
        interval - elapsed);
      auto sleep_dur = std::min(remaining, std::chrono::milliseconds(50));
      if (sleep_dur.count() > 0) {
        std::this_thread::sleep_for(sleep_dur);
      }
    }
    if (stop_flag.load()) {
      return;
    }
    run_updater();
  }
}