#include "http_handler.hpp"
#include "arena_allocator.hpp"
#include "perfetto_categories.hpp"
#include <cstring>
#include <string>
#include <strings.h>

// HttpConnectionState implementation
HttpConnectionState::HttpConnectionState(ArenaAllocator &arena)
    : current_header_field_buf(ArenaStlAllocator<char>(&arena)),
      current_header_value_buf(ArenaStlAllocator<char>(&arena)) {
  llhttp_settings_init(&settings);

  // Set up llhttp callbacks
  settings.on_url = HttpHandler::onUrl;
  settings.on_header_field = HttpHandler::onHeaderField;
  settings.on_header_field_complete = HttpHandler::onHeaderFieldComplete;
  settings.on_header_value = HttpHandler::onHeaderValue;
  settings.on_header_value_complete = HttpHandler::onHeaderValueComplete;
  settings.on_headers_complete = HttpHandler::onHeadersComplete;
  settings.on_body = HttpHandler::onBody;
  settings.on_message_complete = HttpHandler::onMessageComplete;

  llhttp_init(&parser, HTTP_REQUEST, &settings);
  parser.data = this;
}

// HttpHandler implementation
void HttpHandler::on_connection_established(Connection &conn) {
  // Allocate HTTP state in connection's arena
  ArenaAllocator &arena = conn.get_arena();
  void *mem = arena.allocate_raw(sizeof(HttpConnectionState),
                                 alignof(HttpConnectionState));
  auto *state = new (mem) HttpConnectionState(arena);
  conn.user_data = state;
}

void HttpHandler::on_connection_closed(Connection &conn) {
  // Arena cleanup happens automatically when connection is destroyed
  auto *state = static_cast<HttpConnectionState *>(conn.user_data);
  state->~HttpConnectionState();
  conn.user_data = nullptr;
}

void HttpHandler::on_write_buffer_drained(
    std::unique_ptr<Connection> &conn_ptr) {
  // Reset arena after all messages have been written for the next request
  on_connection_closed(*conn_ptr);
  conn_ptr->reset();
  on_connection_established(*conn_ptr);
}

void HttpHandler::on_batch_complete(
    std::span<std::unique_ptr<Connection>> batch) {
  int readyCount = 0;
  for (int i = 0; i < int(batch.size()); ++i) {
    readyCount += batch[i] && batch[i]->outgoingBytesQueued() > 0;
  }
  if (readyCount > 0) {
    auto guard = pipeline.push(readyCount, /*block=*/true);
    auto outIter = guard.batch.begin();
    for (int i = 0; i < int(batch.size()); ++i) {
      if (batch[i] && batch[i]->outgoingBytesQueued() > 0) {
        *outIter++ = std::move(batch[i]);
      }
    }
  }
}

void HttpHandler::on_data_arrived(std::string_view data,
                                  std::unique_ptr<Connection> &conn_ptr) {
  auto *state = static_cast<HttpConnectionState *>(conn_ptr->user_data);
  if (!state) {
    sendErrorResponse(*conn_ptr, 500, "Internal server error", true);
    return;
  }

  // TODO: Enforce the configured max_request_size_bytes limit here.
  // Should track cumulative bytes received for the current HTTP request
  // and send 413 Request Entity Too Large if limit is exceeded.
  // This prevents DoS attacks via oversized HTTP requests.

  // Parse HTTP data with llhttp
  enum llhttp_errno err =
      llhttp_execute(&state->parser, data.data(), data.size());

  if (err != HPE_OK) {
    sendErrorResponse(*conn_ptr, 400, "Bad request", true);
    return;
  }

  // If message is complete, route and handle the request
  if (state->message_complete) {
    // Parse route from method and URL
    state->route = parseRoute(state->method, state->url);

    // Route to appropriate handler
    switch (state->route) {
    case HttpRoute::GET_version:
      handleGetVersion(*conn_ptr, *state);
      break;
    case HttpRoute::POST_commit:
      handlePostCommit(*conn_ptr, *state);
      break;
    case HttpRoute::GET_subscribe:
      handleGetSubscribe(*conn_ptr, *state);
      break;
    case HttpRoute::GET_status:
      handleGetStatus(*conn_ptr, *state);
      break;
    case HttpRoute::PUT_retention:
      handlePutRetention(*conn_ptr, *state);
      break;
    case HttpRoute::GET_retention:
      handleGetRetention(*conn_ptr, *state);
      break;
    case HttpRoute::DELETE_retention:
      handleDeleteRetention(*conn_ptr, *state);
      break;
    case HttpRoute::GET_metrics:
      handleGetMetrics(*conn_ptr, *state);
      break;
    case HttpRoute::GET_ok:
      handleGetOk(*conn_ptr, *state);
      break;
    case HttpRoute::NotFound:
    default:
      handleNotFound(*conn_ptr, *state);
      break;
    }
  }
}

HttpRoute HttpHandler::parseRoute(std::string_view method,
                                  std::string_view url) {
  // Strip query parameters if present
  size_t query_pos = url.find('?');
  if (query_pos != std::string_view::npos) {
    url = url.substr(0, query_pos);
  }

  // Route based on method and path
  if (method == "GET") {
    if (url == "/v1/version")
      return HttpRoute::GET_version;
    if (url == "/v1/subscribe")
      return HttpRoute::GET_subscribe;
    if (url.starts_with("/v1/status"))
      return HttpRoute::GET_status;
    if (url.starts_with("/v1/retention")) {
      // Check if it's a specific retention policy or list all
      return HttpRoute::GET_retention;
    }
    if (url == "/metrics")
      return HttpRoute::GET_metrics;
    if (url == "/ok")
      return HttpRoute::GET_ok;
  } else if (method == "POST") {
    if (url == "/v1/commit")
      return HttpRoute::POST_commit;
  } else if (method == "PUT") {
    if (url.starts_with("/v1/retention/"))
      return HttpRoute::PUT_retention;
  } else if (method == "DELETE") {
    if (url.starts_with("/v1/retention/"))
      return HttpRoute::DELETE_retention;
  }

  return HttpRoute::NotFound;
}

// Route handlers (basic implementations)
void HttpHandler::handleGetVersion(Connection &conn,
                                   const HttpConnectionState &state) {
  sendJsonResponse(
      conn, 200,
      R"({"version":"0.0.1","leader":"node-1","committed_version":42})",
      state.connection_close);
}

void HttpHandler::handlePostCommit(Connection &conn,
                                   const HttpConnectionState &state) {
  // TODO: Parse commit request from state.body and process
  sendJsonResponse(
      conn, 200,
      R"({"request_id":"example","status":"committed","version":43})",
      state.connection_close);
}

void HttpHandler::handleGetSubscribe(Connection &conn,
                                     const HttpConnectionState &state) {
  // TODO: Implement subscription streaming
  sendJsonResponse(
      conn, 200,
      R"({"message":"Subscription endpoint - streaming not yet implemented"})",
      state.connection_close);
}

void HttpHandler::handleGetStatus(Connection &conn,
                                  const HttpConnectionState &state) {
  // TODO: Extract request_id from URL and check status
  sendJsonResponse(
      conn, 200,
      R"({"request_id":"example","status":"committed","version":43})",
      state.connection_close);
}

void HttpHandler::handlePutRetention(Connection &conn,
                                     const HttpConnectionState &state) {
  // TODO: Parse retention policy from body and store
  sendJsonResponse(conn, 200, R"({"policy_id":"example","status":"created"})",
                   state.connection_close);
}

void HttpHandler::handleGetRetention(Connection &conn,
                                     const HttpConnectionState &state) {
  // TODO: Extract policy_id from URL or return all policies
  sendJsonResponse(conn, 200, R"({"policies":[]})", state.connection_close);
}

void HttpHandler::handleDeleteRetention(Connection &conn,
                                        const HttpConnectionState &state) {
  // TODO: Extract policy_id from URL and delete
  sendJsonResponse(conn, 200, R"({"policy_id":"example","status":"deleted"})",
                   state.connection_close);
}

void HttpHandler::handleGetMetrics(Connection &conn,
                                   const HttpConnectionState &state) {
  // TODO: Implement metrics collection and formatting
  sendResponse(conn, 200, "text/plain",
               "# WeaselDB metrics\nweaseldb_requests_total 0\n",
               state.connection_close);
}

void HttpHandler::handleGetOk(Connection &conn,
                              const HttpConnectionState &state) {
  TRACE_EVENT("http", "GET /ok", perfetto::Flow::Global(state.request_id));

  sendResponse(conn, 200, "text/plain", "OK", state.connection_close);
}

void HttpHandler::handleNotFound(Connection &conn,
                                 const HttpConnectionState &state) {
  sendErrorResponse(conn, 404, "Not found", state.connection_close);
}

// HTTP utility methods
void HttpHandler::sendResponse(Connection &conn, int status_code,
                               std::string_view content_type,
                               std::string_view body, bool close_connection) {
  [[maybe_unused]] ArenaAllocator &arena = conn.get_arena();

  // Build HTTP response using arena
  std::string response;
  response.reserve(256 + body.size());

  response += "HTTP/1.1 ";
  response += std::to_string(status_code);
  response += " ";

  // Status text
  switch (status_code) {
  case 200:
    response += "OK";
    break;
  case 400:
    response += "Bad Request";
    break;
  case 404:
    response += "Not Found";
    break;
  case 500:
    response += "Internal Server Error";
    break;
  default:
    response += "Unknown";
    break;
  }

  auto *state = static_cast<HttpConnectionState *>(conn.user_data);

  response += "\r\n";
  response += "Content-Type: ";
  response += content_type;
  response += "\r\n";
  response += "Content-Length: ";
  response += std::to_string(body.size());
  response += "\r\n";
  response += "X-Response-ID: ";
  response += std::to_string(state->request_id);
  response += "\r\n";

  if (close_connection) {
    response += "Connection: close\r\n";
    conn.close_after_send(); // Signal connection should be closed after sending
  } else {
    response += "Connection: keep-alive\r\n";
  }

  response += "\r\n";
  response += body;

  conn.append_message(response);
}

void HttpHandler::sendJsonResponse(Connection &conn, int status_code,
                                   std::string_view json,
                                   bool close_connection) {
  sendResponse(conn, status_code, "application/json", json, close_connection);
}

void HttpHandler::sendErrorResponse(Connection &conn, int status_code,
                                    std::string_view message,
                                    bool close_connection) {
  [[maybe_unused]] ArenaAllocator &arena = conn.get_arena();

  std::string json = R"({"error":")";
  json += message;
  json += R"("})";

  sendJsonResponse(conn, status_code, json, close_connection);
}

// llhttp callbacks
int HttpHandler::onUrl(llhttp_t *parser, const char *at, size_t length) {
  auto *state = static_cast<HttpConnectionState *>(parser->data);
  // Store URL in arena (simplified - would need to accumulate for streaming)
  state->url = std::string_view(at, length);
  return 0;
}

int HttpHandler::onHeaderField(llhttp_t *parser, const char *at,
                               size_t length) {
  auto *state = static_cast<HttpConnectionState *>(parser->data);
  // Accumulate header field data
  state->current_header_field_buf.append(at, length);
  return 0;
}

int HttpHandler::onHeaderFieldComplete(llhttp_t *parser) {
  auto *state = static_cast<HttpConnectionState *>(parser->data);
  state->header_field_complete = true;
  return 0;
}

int HttpHandler::onHeaderValue(llhttp_t *parser, const char *at,
                               size_t length) {
  auto *state = static_cast<HttpConnectionState *>(parser->data);
  // Accumulate header value data
  state->current_header_value_buf.append(at, length);
  return 0;
}

int HttpHandler::onHeaderValueComplete(llhttp_t *parser) {
  auto *state = static_cast<HttpConnectionState *>(parser->data);

  if (!state->header_field_complete) {
    // Field is not complete yet, wait
    return 0;
  }

  // Now we have complete header field and value
  const auto &field = state->current_header_field_buf;
  const auto &value = state->current_header_value_buf;

  // Check for Connection header
  if (field.size() == 10 && strncasecmp(field.data(), "connection", 10) == 0) {
    if (value.size() == 5 && strncasecmp(value.data(), "close", 5) == 0) {
      state->connection_close = true;
    }
  }

  // Check for X-Request-Id header
  if (field.size() == 12 &&
      strncasecmp(field.data(), "x-request-id", 12) == 0) {
    int64_t id = 0;
    for (char c : value) {
      if (c >= '0' && c <= '9') {
        id = id * 10 + (c - '0');
      }
    }
    state->request_id = id;
  }

  // Clear buffers for next header
  state->current_header_field_buf.clear();
  state->current_header_value_buf.clear();
  state->header_field_complete = false;

  return 0;
}

int HttpHandler::onHeadersComplete(llhttp_t *parser) {
  auto *state = static_cast<HttpConnectionState *>(parser->data);
  state->headers_complete = true;

  // Get HTTP method
  const char *method_str =
      llhttp_method_name(static_cast<llhttp_method_t>(parser->method));
  state->method = std::string_view(method_str);

  return 0;
}

int HttpHandler::onBody(llhttp_t *parser, const char *at, size_t length) {
  [[maybe_unused]] auto *state =
      static_cast<HttpConnectionState *>(parser->data);
  (void)at;
  (void)length;
  return 0;
}

int HttpHandler::onMessageComplete(llhttp_t *parser) {
  auto *state = static_cast<HttpConnectionState *>(parser->data);
  state->message_complete = true;
  return 0;
}