/**
 * @file src/process.cpp
 * @brief todo
 */
#define BOOST_BIND_GLOBAL_PLACEHOLDERS

#include "process.h"

#include <filesystem>
#include <string>
#include <vector>

#include <boost/algorithm/string.hpp>
#include <boost/crc.hpp>
#include <boost/filesystem.hpp>
#include <boost/program_options/parsers.hpp>
#include <boost/property_tree/json_parser.hpp>
#include <boost/property_tree/ptree.hpp>

#include <openssl/evp.h>
#include <openssl/sha.h>

#include "config.h"
#include "crypto.h"
#include "main.h"
#include "platform/common.h"
#include "utility.h"

#ifdef _WIN32
  // _SH constants for _wfsopen()
  #include <share.h>
#endif

#define DEFAULT_APP_IMAGE_PATH SUNSHINE_ASSETS_DIR "/box.png"

namespace proc {
  using namespace std::literals;
  namespace bp = boost::process;
  namespace pt = boost::property_tree;

  proc_t proc;

  class deinit_t: public platf::deinit_t {
  public:
    ~deinit_t() {
      proc.terminate();
    }
  };

  /**
   * @brief Initializes proc functions
   * @return Unique pointer to `deinit_t` to manage cleanup
   */
  std::unique_ptr<platf::deinit_t>
  init() {
    return std::make_unique<deinit_t>();
  }

  void
  process_end(bp::child &proc, bp::group &proc_handle) {
    if (!proc.running()) {
      return;
    }

    BOOST_LOG(debug) << "Force termination Child-Process"sv;
    proc_handle.terminate();

    // avoid zombie process
    proc.wait();
  }

  boost::filesystem::path
  find_working_directory(const std::string &cmd, bp::environment &env) {
    // Parse the raw command string into parts to get the actual command portion
#ifdef _WIN32
    auto parts = boost::program_options::split_winmain(cmd);
#else
    auto parts = boost::program_options::split_unix(cmd);
#endif
    if (parts.empty()) {
      BOOST_LOG(error) << "Unable to parse command: "sv << cmd;
      return boost::filesystem::path();
    }

    BOOST_LOG(debug) << "Parsed executable ["sv << parts.at(0) << "] from command ["sv << cmd << ']';

    // If the cmd path is not an absolute path, resolve it using our PATH variable
    boost::filesystem::path cmd_path(parts.at(0));
    if (!cmd_path.is_absolute()) {
      cmd_path = boost::process::search_path(parts.at(0));
      if (cmd_path.empty()) {
        BOOST_LOG(error) << "Unable to find executable ["sv << parts.at(0) << "]. Is it in your PATH?"sv;
        return boost::filesystem::path();
      }
    }

    BOOST_LOG(debug) << "Resolved executable ["sv << parts.at(0) << "] to path ["sv << cmd_path << ']';

    // Now that we have a complete path, we can just use parent_path()
    return cmd_path.parent_path();
  }

  int
  proc_t::execute(int app_id) {
    // Ensure starting from a clean slate
    terminate();

    auto iter = std::find_if(_apps.begin(), _apps.end(), [&app_id](const auto app) {
      return app.id == std::to_string(app_id);
    });

    if (iter == _apps.end()) {
      BOOST_LOG(error) << "Couldn't find app with ID ["sv << app_id << ']';
      return 404;
    }

    _app_id = app_id;
    _app = *iter;

    _app_prep_begin = std::begin(_app.prep_cmds);
    _app_prep_it = _app_prep_begin;

    if (!_app.output.empty() && _app.output != "null"sv) {
#ifdef _WIN32
      // fopen() interprets the filename as an ANSI string on Windows, so we must convert it
      // to UTF-16 and use the wchar_t variants for proper Unicode log file path support.
      std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t> converter;
      auto woutput = converter.from_bytes(_app.output);

      // Use _SH_DENYNO to allow us to open this log file again for writing even if it is
      // still open from a previous execution. This is required to handle the case of a
      // detached process executing again while the previous process is still running.
      _pipe.reset(_wfsopen(woutput.c_str(), L"a", _SH_DENYNO));
#else
      _pipe.reset(fopen(_app.output.c_str(), "a"));
#endif
    }

    std::error_code ec;
    // Executed when returning from function
    auto fg = util::fail_guard([&]() {
      terminate();
    });

    for (; _app_prep_it != std::end(_app.prep_cmds); ++_app_prep_it) {
      auto &cmd = *_app_prep_it;

      // Skip empty commands
      if (cmd.do_cmd.empty()) {
        continue;
      }

      boost::filesystem::path working_dir = _app.working_dir.empty() ?
                                              find_working_directory(cmd.do_cmd, _env) :
                                              boost::filesystem::path(_app.working_dir);
      BOOST_LOG(info) << "Executing Do Cmd: ["sv << cmd.do_cmd << ']';
      auto child = platf::run_command(cmd.elevated, true, cmd.do_cmd, working_dir, _env, _pipe.get(), ec, nullptr);

      if (ec) {
        BOOST_LOG(error) << "Couldn't run ["sv << cmd.do_cmd << "]: System: "sv << ec.message();
        return -1;
      }

      child.wait();
      auto ret = child.exit_code();

      if (ret != 0) {
        BOOST_LOG(error) << '[' << cmd.do_cmd << "] failed with code ["sv << ret << ']';
        return -1;
      }
    }

    for (auto &cmd : _app.detached) {
      boost::filesystem::path working_dir = _app.working_dir.empty() ?
                                              find_working_directory(cmd, _env) :
                                              boost::filesystem::path(_app.working_dir);
      BOOST_LOG(info) << "Spawning ["sv << cmd << "] in ["sv << working_dir << ']';
      auto child = platf::run_command(_app.elevated, true, cmd, working_dir, _env, _pipe.get(), ec, nullptr);
      if (ec) {
        BOOST_LOG(warning) << "Couldn't spawn ["sv << cmd << "]: System: "sv << ec.message();
      }
      else {
        child.detach();
      }
    }

    if (_app.cmd.empty()) {
      BOOST_LOG(info) << "Executing [Desktop]"sv;
      placebo = true;
    }
    else {
      boost::filesystem::path working_dir = _app.working_dir.empty() ?
                                              find_working_directory(_app.cmd, _env) :
                                              boost::filesystem::path(_app.working_dir);
      BOOST_LOG(info) << "Executing: ["sv << _app.cmd << "] in ["sv << working_dir << ']';
      _process = platf::run_command(_app.elevated, true, _app.cmd, working_dir, _env, _pipe.get(), ec, &_process_handle);
      if (ec) {
        BOOST_LOG(warning) << "Couldn't run ["sv << _app.cmd << "]: System: "sv << ec.message();
        return -1;
      }
    }

    fg.disable();

    return 0;
  }

  int
  proc_t::running() {
    if (placebo || _process.running()) {
      return _app_id;
    }

    // Perform cleanup actions now if needed
    if (_process) {
      terminate();
    }

    return 0;
  }

  void
  proc_t::terminate() {
    std::error_code ec;

    // Ensure child process is terminated
    placebo = false;
    process_end(_process, _process_handle);
    _process = bp::child();
    _process_handle = bp::group();
    _app_id = -1;

    for (; _app_prep_it != _app_prep_begin; --_app_prep_it) {
      auto &cmd = *(_app_prep_it - 1);

      if (cmd.undo_cmd.empty()) {
        continue;
      }

      boost::filesystem::path working_dir = _app.working_dir.empty() ?
                                              find_working_directory(cmd.undo_cmd, _env) :
                                              boost::filesystem::path(_app.working_dir);
      BOOST_LOG(info) << "Executing Undo Cmd: ["sv << cmd.undo_cmd << ']';
      auto child = platf::run_command(cmd.elevated, true, cmd.undo_cmd, working_dir, _env, _pipe.get(), ec, nullptr);

      if (ec) {
        BOOST_LOG(warning) << "System: "sv << ec.message();
      }

      child.wait();
      auto ret = child.exit_code();

      if (ret != 0) {
        BOOST_LOG(warning) << "Return code ["sv << ret << ']';
      }
    }

    _pipe.reset();
  }

  const std::vector<ctx_t> &
  proc_t::get_apps() const {
    return _apps;
  }
  std::vector<ctx_t> &
  proc_t::get_apps() {
    return _apps;
  }

  // Gets application image from application list.
  // Returns image from assets directory if found there.
  // Returns default image if image configuration is not set.
  // Returns http content-type header compatible image type.
  std::string
  proc_t::get_app_image(int app_id) {
    auto iter = std::find_if(_apps.begin(), _apps.end(), [&app_id](const auto app) {
      return app.id == std::to_string(app_id);
    });
    auto app_image_path = iter == _apps.end() ? std::string() : iter->image_path;

    return validate_app_image_path(app_image_path);
  }

  proc_t::~proc_t() {
    // It's not safe to call terminate() here because our proc_t is a static variable
    // that may be destroyed after the Boost loggers have been destroyed. Instead,
    // we return a deinit_t to main() to handle termination when we're exiting.
    // Once we reach this point here, termination must have already happened.
    assert(!placebo);
    assert(!_process.running());
  }

  std::string_view::iterator
  find_match(std::string_view::iterator begin, std::string_view::iterator end) {
    int stack = 0;

    --begin;
    do {
      ++begin;
      switch (*begin) {
        case '(':
          ++stack;
          break;
        case ')':
          --stack;
      }
    } while (begin != end && stack != 0);

    if (begin == end) {
      throw std::out_of_range("Missing closing bracket \')\'");
    }
    return begin;
  }

  std::string
  parse_env_val(bp::native_environment &env, const std::string_view &val_raw) {
    auto pos = std::begin(val_raw);
    auto dollar = std::find(pos, std::end(val_raw), '$');

    std::stringstream ss;

    while (dollar != std::end(val_raw)) {
      auto next = dollar + 1;
      if (next != std::end(val_raw)) {
        switch (*next) {
          case '(': {
            ss.write(pos, (dollar - pos));
            auto var_begin = next + 1;
            auto var_end = find_match(next, std::end(val_raw));
            auto var_name = std::string { var_begin, var_end };

#ifdef _WIN32
            // Windows treats environment variable names in a case-insensitive manner,
            // so we look for a case-insensitive match here. This is critical for
            // correctly appending to PATH on Windows.
            auto itr = std::find_if(env.cbegin(), env.cend(),
              [&](const auto &e) { return boost::iequals(e.get_name(), var_name); });
            if (itr != env.cend()) {
              // Use an existing case-insensitive match
              var_name = itr->get_name();
            }
#endif

            ss << env[var_name].to_string();

            pos = var_end + 1;
            next = var_end;

            break;
          }
          case '$':
            ss.write(pos, (next - pos));
            pos = next + 1;
            ++next;
            break;
        }

        dollar = std::find(next, std::end(val_raw), '$');
      }
      else {
        dollar = next;
      }
    }

    ss.write(pos, (dollar - pos));

    return ss.str();
  }

  std::string
  validate_app_image_path(std::string app_image_path) {
    if (app_image_path.empty()) {
      return DEFAULT_APP_IMAGE_PATH;
    }

    // get the image extension and convert it to lowercase
    auto image_extension = std::filesystem::path(app_image_path).extension().string();
    boost::to_lower(image_extension);

    // return the default box image if extension is not "png"
    if (image_extension != ".png") {
      return DEFAULT_APP_IMAGE_PATH;
    }

    // check if image is in assets directory
    auto full_image_path = std::filesystem::path(SUNSHINE_ASSETS_DIR) / app_image_path;
    if (std::filesystem::exists(full_image_path)) {
      return full_image_path.string();
    }
    else if (app_image_path == "./assets/steam.png") {
      // handle old default steam image definition
      return SUNSHINE_ASSETS_DIR "/steam.png";
    }

    // check if specified image exists
    std::error_code code;
    if (!std::filesystem::exists(app_image_path, code)) {
      // return default box image if image does not exist
      BOOST_LOG(warning) << "Couldn't find app image at path ["sv << app_image_path << ']';
      return DEFAULT_APP_IMAGE_PATH;
    }

    // image is a png, and not in assets directory
    // return only "content-type" http header compatible image type
    return app_image_path;
  }

  std::optional<std::string>
  calculate_sha256(const std::string &filename) {
    crypto::md_ctx_t ctx { EVP_MD_CTX_create() };
    if (!ctx) {
      return std::nullopt;
    }

    if (!EVP_DigestInit_ex(ctx.get(), EVP_sha256(), nullptr)) {
      return std::nullopt;
    }

    // Read file and update calculated SHA
    char buf[1024 * 16];
    std::ifstream file(filename, std::ifstream::binary);
    while (file.good()) {
      file.read(buf, sizeof(buf));
      if (!EVP_DigestUpdate(ctx.get(), buf, file.gcount())) {
        return std::nullopt;
      }
    }
    file.close();

    unsigned char result[SHA256_DIGEST_LENGTH];
    if (!EVP_DigestFinal_ex(ctx.get(), result, nullptr)) {
      return std::nullopt;
    }

    // Transform byte-array to string
    std::stringstream ss;
    ss << std::hex << std::setfill('0');
    for (const auto &byte : result) {
      ss << std::setw(2) << (int) byte;
    }
    return ss.str();
  }

  uint32_t
  calculate_crc32(const std::string &input) {
    boost::crc_32_type result;
    result.process_bytes(input.data(), input.length());
    return result.checksum();
  }

  std::tuple<std::string, std::string>
  calculate_app_id(const std::string &app_name, std::string app_image_path, int index) {
    // Generate id by hashing name with image data if present
    std::vector<std::string> to_hash;
    to_hash.push_back(app_name);
    auto file_path = validate_app_image_path(app_image_path);
    if (file_path != DEFAULT_APP_IMAGE_PATH) {
      auto file_hash = calculate_sha256(file_path);
      if (file_hash) {
        to_hash.push_back(file_hash.value());
      }
      else {
        // Fallback to just hashing image path
        to_hash.push_back(file_path);
      }
    }

    // Create combined strings for hash
    std::stringstream ss;
    for_each(to_hash.begin(), to_hash.end(), [&ss](const std::string &s) { ss << s; });
    auto input_no_index = ss.str();
    ss << index;
    auto input_with_index = ss.str();

    // CRC32 then truncate to signed 32-bit range due to client limitations
    auto id_no_index = std::to_string(abs((int32_t) calculate_crc32(input_no_index)));
    auto id_with_index = std::to_string(abs((int32_t) calculate_crc32(input_with_index)));

    return std::make_tuple(id_no_index, id_with_index);
  }

  std::optional<proc::proc_t>
  parse(const std::string &file_name) {
    pt::ptree tree;

    try {
      pt::read_json(file_name, tree);

      auto &apps_node = tree.get_child("apps"s);
      auto &env_vars = tree.get_child("env"s);

      auto this_env = boost::this_process::environment();

      for (auto &[name, val] : env_vars) {
        this_env[name] = parse_env_val(this_env, val.get_value<std::string>());
      }

      std::set<std::string> ids;
      std::vector<proc::ctx_t> apps;
      int i = 0;
      for (auto &[_, app_node] : apps_node) {
        proc::ctx_t ctx;

        auto prep_nodes_opt = app_node.get_child_optional("prep-cmd"s);
        auto detached_nodes_opt = app_node.get_child_optional("detached"s);
        auto exclude_global_prep = app_node.get_optional<bool>("exclude-global-prep-cmd"s);
        auto output = app_node.get_optional<std::string>("output"s);
        auto name = parse_env_val(this_env, app_node.get<std::string>("name"s));
        auto cmd = app_node.get_optional<std::string>("cmd"s);
        auto image_path = app_node.get_optional<std::string>("image-path"s);
        auto working_dir = app_node.get_optional<std::string>("working-dir"s);
        auto elevated = app_node.get_optional<bool>("elevated"s);

        std::vector<proc::cmd_t> prep_cmds;
        if (!exclude_global_prep.value_or(false)) {
          prep_cmds.reserve(config::sunshine.prep_cmds.size());
          for (auto &prep_cmd : config::sunshine.prep_cmds) {
            auto do_cmd = parse_env_val(this_env, prep_cmd.do_cmd);
            auto undo_cmd = parse_env_val(this_env, prep_cmd.undo_cmd);

            prep_cmds.emplace_back(
              std::move(do_cmd),
              std::move(undo_cmd),
              std::move(prep_cmd.elevated));
          }
        }

        if (prep_nodes_opt) {
          auto &prep_nodes = *prep_nodes_opt;

          prep_cmds.reserve(prep_cmds.size() + prep_nodes.size());
          for (auto &[_, prep_node] : prep_nodes) {
            auto do_cmd = prep_node.get_optional<std::string>("do"s);
            auto undo_cmd = prep_node.get_optional<std::string>("undo"s);
            auto elevated = prep_node.get_optional<bool>("elevated");

            prep_cmds.emplace_back(
              parse_env_val(this_env, do_cmd.value_or("")),
              parse_env_val(this_env, undo_cmd.value_or("")),
              std::move(elevated.value_or(false)));
          }
        }

        std::vector<std::string> detached;
        if (detached_nodes_opt) {
          auto &detached_nodes = *detached_nodes_opt;

          detached.reserve(detached_nodes.size());
          for (auto &[_, detached_val] : detached_nodes) {
            detached.emplace_back(parse_env_val(this_env, detached_val.get_value<std::string>()));
          }
        }

        if (output) {
          ctx.output = parse_env_val(this_env, *output);
        }

        if (cmd) {
          ctx.cmd = parse_env_val(this_env, *cmd);
        }

        if (working_dir) {
          ctx.working_dir = parse_env_val(this_env, *working_dir);
        }

        if (image_path) {
          ctx.image_path = parse_env_val(this_env, *image_path);
        }

        ctx.elevated = elevated.value_or(false);

        auto possible_ids = calculate_app_id(name, ctx.image_path, i++);
        if (ids.count(std::get<0>(possible_ids)) == 0) {
          // Avoid using index to generate id if possible
          ctx.id = std::get<0>(possible_ids);
        }
        else {
          // Fallback to include index on collision
          ctx.id = std::get<1>(possible_ids);
        }
        ids.insert(ctx.id);

        ctx.name = std::move(name);
        ctx.prep_cmds = std::move(prep_cmds);
        ctx.detached = std::move(detached);

        apps.emplace_back(std::move(ctx));
      }

      return proc::proc_t {
        std::move(this_env), std::move(apps)
      };
    }
    catch (std::exception &e) {
      BOOST_LOG(error) << e.what();
    }

    return std::nullopt;
  }

  void
  refresh(const std::string &file_name) {
    auto proc_opt = proc::parse(file_name);

    if (proc_opt) {
      proc = std::move(*proc_opt);
    }
  }
}  // namespace proc
