#include <vamp_zero/control.hpp>

#include <chrono>
#include <array>
#include <expected>
#include <filesystem>
#include <fstream>
#include <memory>
#include <mutex>
#include <optional>
#include <set>
#include <string>
#include <utility>

#include <boost/asio/awaitable.hpp>
#include <boost/json/object.hpp>
#include <boost/json/value.hpp>
#include <openssl/sha.h>

#include <vamp_protocol/page_control.hpp>
#include <vamp_zero/page_control.hpp>
#include <vamp_zero/errors.hpp>


namespace {

auto read_asset(std::filesystem::path const &root, std::filesystem::path const &relative, std::size_t limit, std::string *resolved = nullptr) -> std::optional<std::string> {
  auto error = std::error_code{};
  auto canonical_root = std::filesystem::canonical(root, error);
  if (error) {
    return std::nullopt;
  }
  auto path = std::filesystem::canonical(canonical_root / relative, error);
  auto contained = path.lexically_relative(canonical_root);
  if (error || contained.empty() || *contained.begin() == ".." || !std::filesystem::is_regular_file(path, error) || error) {
    return std::nullopt;
  }
  auto size = std::filesystem::file_size(path, error);
  if (error || size == 0U || size > limit) {
    return std::nullopt;
  }
  auto bytes = std::string(static_cast<std::size_t>(size), '\0');
  auto input = std::ifstream{path, std::ios::binary};
  if (!input.read(bytes.data(), static_cast<std::streamsize>(bytes.size())) || input.peek() != std::ifstream::traits_type::eof()) {
    return std::nullopt;
  }
  if (resolved != nullptr) {
    *resolved = path.string();
  }
  return bytes;
}

struct title_file {
  std::string path;
  std::string bytes;
};

auto read_title(std::filesystem::path const &root, std::string const &identifier) -> std::optional<title_file> {
  if (!vamp_protocol::valid_title_id(identifier)) {
    return std::nullopt;
  }
  auto resolved = std::string{};
  auto bytes = read_asset(root, std::filesystem::path{"pico/titles"} / (identifier + ".mask"), vamp_protocol::title_image_size, &resolved);
  if (!bytes || !vamp_protocol::valid_title_image(*bytes)) {
    return std::nullopt;
  }
  auto error = std::error_code{};
  auto directory = std::filesystem::canonical(root / "pico/titles", error);
  if (error || std::filesystem::path{resolved}.parent_path() != directory) {
    return std::nullopt;
  }
  auto digest = std::array<std::uchar_t, SHA256_DIGEST_LENGTH>{};
  SHA256(reinterpret_cast<std::uchar_t const *>(bytes->data()), bytes->size(), digest.data());
  auto hash = std::string{};
  constexpr auto digits = std::string_view{"0123456789abcdef"};
  for (auto byte : digest) {
    hash.push_back(digits[byte >> 4U]);
    hash.push_back(digits[byte & 15U]);
  }
  if (hash != identifier) {
    return std::nullopt;
  }
  return title_file{std::move(resolved), std::move(*bytes)};
}

class title_assets {
public:
  title_assets(std::filesystem::path root, vamp_zero::catalog const &catalog)
      : root_{std::move(root)} {
    for (auto const &part : catalog.parts) {
      identifiers_.insert(part.title_image);
    }
  }
  auto image(std::string const &identifier) const -> std::optional<title_file> {
    return identifiers_.contains(identifier) ? read_title(root_, identifier) : std::nullopt;
  }
private:
  std::filesystem::path root_;
  std::set<std::string> identifiers_{};
};

auto remote_response(vamp_zero::app_state const &state) -> ligo::service_response {
  return ligo::text_response("text/plain; charset=utf-8", vamp_zero::remote_display_text(state));
}

}

auto vamp_zero::validated_title_path(std::string const &assets_path, std::string const &identifier) -> std::expected<std::string, modulus::error> {
  auto title = read_title(assets_path, identifier);
  if (!title) {
    return std::unexpected(vamp_zero::make_error(vamp_zero::error_code::INVALID_ARGUMENT, "invalid or missing generated Pico title; regenerate assets"));
  }
  return std::move(title->path);
}

vamp_zero::control_state::control_state(vamp_zero::config config, vamp_zero::app_state state)
    : config_{std::move(config)}, state_{std::move(state)} {}

auto vamp_zero::control_state::config() const -> vamp_zero::config {
  auto lock = std::scoped_lock{mutex_};
  return config_;
}

auto vamp_zero::control_state::pico_connected_locked() const -> std::bool_t {
  return last_heartbeat_ != std::chrono::steady_clock::time_point{} && std::chrono::steady_clock::now() - last_heartbeat_ < std::chrono::seconds{3};
}

auto vamp_zero::control_state::snapshot_locked() const -> vamp_zero::app_state {
  auto copy = state_;
  copy.pico_connected = pico_connected_locked();
  return copy;
}

auto vamp_zero::control_state::snapshot() const -> vamp_zero::app_state {
  auto lock = std::scoped_lock{mutex_};
  return snapshot_locked();
}

auto vamp_zero::control_state::apply(vamp_protocol::page_command command) -> vamp_zero::app_state {
  auto observer = std::function<void(vamp_zero::app_state)>{};
  auto updated = vamp_zero::app_state{};
  {
    auto lock = std::scoped_lock{mutex_};
    state_ = vamp_zero::apply_app_command(std::move(state_), command);
    state_.pico_connected = pico_connected_locked();
    updated = state_;
    observer = observer_;
  }
  if (observer) {
    observer(updated);
  }
  return updated;
}

auto vamp_zero::control_state::apply(vamp_zero::menu_action const &action) -> vamp_zero::app_state {
  auto observer = std::function<void(vamp_zero::app_state)>{};
  auto updated = vamp_zero::app_state{};
  {
    auto lock = std::scoped_lock{mutex_};
    auto revision = state_.input_revision;
    state_ = vamp_zero::apply_menu_action(std::move(state_), action);
    updated = snapshot_locked();
    if (revision != state_.input_revision) {
      observer = observer_;
    }
  }
  if (observer) {
    observer(updated);
  }
  return updated;
}

auto vamp_zero::control_state::heartbeat() -> vamp_zero::app_state {
  auto observer = std::function<void(vamp_zero::app_state)>{};
  auto updated = vamp_zero::app_state{};
  {
    auto lock = std::scoped_lock{mutex_};
    last_heartbeat_ = std::chrono::steady_clock::now();
    auto notify = !state_.pico_connected;
    state_.pico_connected = true;
    updated = state_;
    if (notify) {
      observer = observer_;
    }
  }
  if (observer) {
    observer(updated);
  }
  return updated;
}

auto vamp_zero::control_state::refresh_connection() -> std::optional<vamp_zero::app_state> {
  auto observer = std::function<void(vamp_zero::app_state)>{};
  auto updated = vamp_zero::app_state{};
  {
    auto lock = std::scoped_lock{mutex_};
    auto connected = pico_connected_locked();
    if (connected == state_.pico_connected) {
      return std::nullopt;
    }
    state_.pico_connected = connected;
    updated = state_;
    observer = observer_;
  }
  if (observer) {
    observer(updated);
  }
  return updated;
}

auto vamp_zero::control_state::set_observer(std::function<void(vamp_zero::app_state)> observer) -> void {
  auto lock = std::scoped_lock{mutex_};
  observer_ = std::move(observer);
}

auto vamp_zero::control_state::finish_playback(std::uint64_t session, std::string error, std::shared_ptr<vamp_zero::catalog const> catalog) -> void {
  auto observer = std::function<void(vamp_zero::app_state)>{};
  auto updated = vamp_zero::app_state{};
  {
    auto lock = std::scoped_lock{mutex_};
    if (!state_.audio.playback_enabled || state_.score_session != session || (catalog && catalog != state_.catalog) || state_.mode != vamp_zero::app_mode::PERFORMANCE_SCORE) {
      return;
    }
    if (error.empty()) {
      state_ = vamp_zero::apply_app_command(std::move(state_), vamp_protocol::page_command::SELECT);
    } else {
      state_.audio.playback_error = std::move(error);
    }
    updated = snapshot_locked();
    observer = observer_;
  }
  if (observer) {
    observer(std::move(updated));
  }
}

auto vamp_zero::make_router(vamp_zero::control_state &state) -> ligo::service_router {
  auto router = ligo::service_router{};
  auto assets = state.config().runtime.assets_path;
  auto artwork = std::make_shared<title_assets const>(assets, *state.snapshot().catalog);
  router.add_response_route("POST", vamp_protocol::remote_title_path, [artwork](ligo::request_context, boost::json::value payload) -> boost::asio::awaitable<std::expected<ligo::service_response, modulus::error>> {
    auto const *id = payload.is_object() && payload.as_object().size() == 1U ? payload.as_object().if_contains("id") : nullptr;
    if (id == nullptr || !id->is_string() || !vamp_protocol::valid_title_id(id->as_string())) {
      co_return std::unexpected(vamp_zero::make_error(vamp_zero::error_code::INVALID_ARGUMENT, "invalid title identifier"));
    }
    auto bytes = artwork->image(std::string{id->as_string()});
    if (!bytes) {
      co_return std::unexpected(vamp_zero::make_error(vamp_zero::error_code::INVALID_ARGUMENT, "generated title unavailable"));
    }
    co_return ligo::text_response("application/octet-stream", std::move(bytes->bytes));
  });
  router.add_route("GET", "/api/health", [](ligo::request_context, boost::json::value) -> boost::asio::awaitable<std::expected<boost::json::value, modulus::error>> {
    co_return boost::json::object{{"product", "product-vamp"}, {"device", "zero"}, {"status", "ready"}};
  });
  router.add_response_route("GET", vamp_protocol::remote_display_path, [&state](ligo::request_context, boost::json::value) -> boost::asio::awaitable<std::expected<ligo::service_response, modulus::error>> {
    auto updated = state.heartbeat();
    co_return remote_response(updated);
  });
  router.add_response_route("POST", vamp_protocol::remote_heartbeat_path, [&state](ligo::request_context, boost::json::value) -> boost::asio::awaitable<std::expected<ligo::service_response, modulus::error>> {
    auto updated = state.heartbeat();
    co_return remote_response(updated);
  });
  router.add_response_route("POST", vamp_protocol::remote_next_path, [&state](ligo::request_context, boost::json::value) -> boost::asio::awaitable<std::expected<ligo::service_response, modulus::error>> {
    static_cast<void>(state.heartbeat());
    auto updated = state.apply(vamp_protocol::page_command::NEXT);
    co_return remote_response(updated);
  });
  router.add_response_route("POST", vamp_protocol::remote_previous_path, [&state](ligo::request_context, boost::json::value) -> boost::asio::awaitable<std::expected<ligo::service_response, modulus::error>> {
    static_cast<void>(state.heartbeat());
    auto updated = state.apply(vamp_protocol::page_command::PREVIOUS);
    co_return remote_response(updated);
  });
  router.add_response_route("POST", vamp_protocol::remote_select_path, [&state](ligo::request_context, boost::json::value) -> boost::asio::awaitable<std::expected<ligo::service_response, modulus::error>> {
    static_cast<void>(state.heartbeat());
    auto updated = state.apply(vamp_protocol::page_command::SELECT);
    co_return remote_response(updated);
  });
  return router;
}