// SPDX-License-Identifier: MIT
#include "help_window.hpp"

#include <adwaita.h>

#include <functional>
#include <string>
#include <vector>

#include "build_info.hpp"
#include "layout_store.hpp"

// Both come from CMakeLists: the document identifier is derived from the desktop file's
// basename (its desktop-file id), and the directory is where the Mallard set lives in the
// source tree, which is what the self-check scans. Yelp resolves `help:<identifier>` to
// `<datadir>/help/<lang>/<identifier>/` on its own (freedesktop Help System Specification),
// so the identifier and the installed directory have to name the same set -- which is why
// neither is written out again here.
static_assert(sizeof(UDPSCOPE_HELP_NAME) > 1, "UDPSCOPE_HELP_NAME must come from the build");
static_assert(sizeof(UDPSCOPE_HELP_DIR) > 1, "UDPSCOPE_HELP_DIR must come from the build");

namespace udpscope {
namespace {

/// Nulled by each dialog's own close handler, so a second open cannot present a dead widget.
/// One pointer per dialog, file-scope because there is one application. The help manual is no
/// longer one of these: it opens in a separate viewer process through the `help:` URI, and a
/// process with no window of ours has nothing to null.
AdwDialog* g_about = nullptr;
/// The overview is built from a `.ui` file, so its builder is held too: the window belongs to
/// the builder, and a *destroyed* `GtkWindow` cannot be presented again -- which is why the
/// builder is replaced on the next opening rather than reused.
GtkWidget* g_shortcuts = nullptr;
GtkBuilder* g_shortcuts_ui = nullptr;

gboolean on_window_close(GtkWindow* window, gpointer slot) {
  (void)window;
  *static_cast<GtkWidget**>(slot) = nullptr;
  return FALSE;  // let the default handler destroy it
}

/// Shared by both `AdwDialog`s: the pointer to clear is the `user_data`, so there is one
/// handler rather than one per dialog.
void on_dialog_closed(AdwDialog* dialog, gpointer slot) {
  (void)dialog;
  *static_cast<AdwDialog**>(slot) = nullptr;
}

/// What an asynchronous launch needs to survive the call: the window it is attributed to (held,
/// because the call outlives the stack frame that made it) and the caller's reporter, if it asked
/// for one. One small struct rather than two `gpointer`s, because a callback that takes both through
/// one `user_data` still has to get them there.
struct HelpLaunch {
  GtkWindow* parent = nullptr;
  std::function<void(bool, const std::string&)> done;
};

/// The launch failed. Report it rather than leaving a click that silently did nothing -- and say
/// *which* thing is missing: `gtk_uri_launcher_launch_finish()` reports that the URI could not be
/// handed over, which is the handler's absence, while a document that is not installed is a
/// different failure the launcher cannot tell it from. `help_installed_path()` settles that from the
/// file system, so a missing *document* is not reported as a missing *handler*: with the manual
/// installed the message names the viewer, and without it the message names the document, its
/// expected path and the install command -- and a viewer as well, because that second possibility
/// cannot be ruled out from here.
void on_help_launched(GObject* source, GAsyncResult* result, gpointer user) {
  auto* launch = static_cast<HelpLaunch*>(user);
  GError* error = nullptr;
  const bool ok = gtk_uri_launcher_launch_finish(GTK_URI_LAUNCHER(source), result, &error);
  if (!ok) {
    const std::string installed = help_installed_path();
    GtkAlertDialog* alert = gtk_alert_dialog_new("Could not open the help manual");
    std::string detail = error != nullptr ? error->message : std::string("the launch failed");
    detail += "\n\n";
    if (!installed.empty()) {
      detail += "The manual is installed at " + installed +
                ", so what is missing is a viewer for the `help:` URI it is opened with: install "
                "one (for example `yelp`) or make it the desktop's default for that scheme.";
    } else {
      // The system-wide install is named *first* on purpose: a set under the user's data
      // directory is one a sandboxed viewer (Yelp) cannot read its figures from -- the pages
      // open without their images -- so the no-root route carries that caveat rather than
      // leading. The message is kept no longer than the one it replaces; do the same on edit.
      detail += "The manual does not look installed: nothing named \"help:" UDPSCOPE_HELP_NAME
                "\" was found where `help:` resolves. Install it system-wide:\n\n"
                "    cmake -DCMAKE_INSTALL_PREFIX=/usr .. && sudo cmake --build build --target install-help\n\n"
                "That writes where the viewer looks. The no-root `install-help-user` writes under "
                "your data directory instead: a sandboxed viewer shows those pages without their "
                "figures. A `help:` viewer (for example `yelp`) is needed as well.";
    }
    gtk_alert_dialog_set_detail(alert, detail.c_str());
    gtk_alert_dialog_show(alert, launch->parent);
    g_object_unref(alert);
  }
  if (launch->done) {
    launch->done(ok, ok || error == nullptr ? std::string() : std::string(error->message));
  }
  if (launch->parent != nullptr) g_object_unref(launch->parent);
  delete launch;
  if (error != nullptr) g_error_free(error);
}

}  // namespace

void show_about(GtkWindow* parent, const std::string& session_path) {
  if (g_about != nullptr) {
    adw_dialog_present(g_about, GTK_WIDGET(parent));
    return;
  }

  // `AdwAboutDialog` rather than `GtkAboutDialog`: it shows the application icon as the page's
  // own header, which is the whole reason the app has one, and `adw_about_window_new()` is
  // deprecated in favour of it. It is an `AdwDialog`, so it is modal on what it is presented
  // on and needs no transient-for or modal call of its own.
  AdwDialog* dialog = adw_about_dialog_new();
  g_about = dialog;
  AdwAboutDialog* about = ADW_ABOUT_DIALOG(dialog);
  adw_about_dialog_set_application_name(about, "udpscope");
  adw_about_dialog_set_application_icon(about, "org.udpscope.app");
  adw_about_dialog_set_developer_name(about, "Martino Ferrari");
  adw_about_dialog_set_version(about, build_info::kVersion);
  adw_about_dialog_set_comments(about, "An oscilloscope for UDPStreamer sources.");
  adw_about_dialog_set_license_type(about, GTK_LICENSE_MIT_X11);
  adw_about_dialog_set_website(about, "https://git.ferrarinas.it/martino/udpscope");

  // `debug_info` rather than `system_information`: it renders as a Troubleshooting page with a
  // copy button, where the old field was inert text a user had to retype. A `std::string`
  // rather than a fixed buffer, because a long settings path used to truncate it silently.
  const std::string debug = "Commit: " + std::string(build_info::kCommit) +
                            "\nBuilt: " + build_info::kTimestamp +
                            "\nSettings: " + config_dir() +
                            "\nSession file: " + session_path;
  adw_about_dialog_set_debug_info(about, debug.c_str());

  g_signal_connect(dialog, "closed", G_CALLBACK(on_dialog_closed), &g_about);
  adw_dialog_present(dialog, GTK_WIDGET(parent));
}

const char* about_icon_name() {
  if (g_about == nullptr) return "";
  return adw_about_dialog_get_application_icon(ADW_ABOUT_DIALOG(g_about));
}

std::string help_installed_path() {
  // The freedesktop Help System Specification's own search order: `$XDG_DATA_HOME` first, then every
  // `$XDG_DATA_DIRS` entry in order. Yelp resolves `help:<id>` the same way, so this is a reading of
  // where the document *would* be found rather than a second, private convention.
  std::vector<std::string> roots;
  roots.emplace_back(g_get_user_data_dir() != nullptr ? g_get_user_data_dir() : "");
  const char* const* dirs = g_get_system_data_dirs();
  for (int i = 0; dirs != nullptr && dirs[i] != nullptr; ++i) roots.emplace_back(dirs[i]);
  for (const std::string& root : roots) {
    if (root.empty()) continue;
    const std::string base = root + "/help";
    GError* error = nullptr;
    GDir* dir = g_dir_open(base.c_str(), 0, &error);
    if (dir == nullptr) {
      if (error != nullptr) g_error_free(error);
      continue;
    }
    // `<lang>` is a directory of its own (`C`, `en`, `it`, ...), so the document is looked for one
    // level below the `help` root rather than straight under it.
    while (const char* lang = g_dir_read_name(dir)) {
      const std::string candidate = base + "/" + lang + "/" UDPSCOPE_HELP_NAME;
      if (g_file_test((candidate + "/index.page").c_str(), G_FILE_TEST_IS_REGULAR)) {
        g_dir_close(dir);
        return candidate;
      }
    }
    g_dir_close(dir);
  }
  return std::string();
}

HelpReport help_self_check() {
  HelpReport report;

  // The manual is a set of files on disk now, so the reading is a file-system one: a missing
  // directory leaves `topics=0 index=false`, which is a manual that is not where the build
  // says it is -- and Yelp would show nothing for `help:<identifier>`.
  GError* error = nullptr;
  GDir* dir = g_dir_open(UDPSCOPE_HELP_DIR, 0, &error);
  if (dir == nullptr) {
    if (error != nullptr) g_error_free(error);
    return report;
  }
  while (const char* name = g_dir_read_name(dir)) {
    if (!g_str_has_suffix(name, ".page")) continue;
    if (g_strcmp0(name, "index.page") == 0) report.index = true;
    else ++report.topics;
  }
  g_dir_close(dir);

  // The figures the pages reference, counted for the same reason: an image that went missing
  // is a broken figure in the viewer rather than a failed build.
  const std::string figures = std::string(UDPSCOPE_HELP_DIR) + "/figures";
  if (GDir* figdir = g_dir_open(figures.c_str(), 0, &error)) {
    while (const char* name = g_dir_read_name(figdir)) {
      if (g_str_has_suffix(name, ".png") || g_str_has_suffix(name, ".jpg")) ++report.figures;
    }
    g_dir_close(figdir);
  } else if (error != nullptr) {
    g_error_free(error);
  }
  return report;
}

void show_help(GtkWindow* parent, std::function<void(bool, const std::string&)> done) {
  // The freedesktop `help:` URI, handed to whatever the desktop registered for it -- Yelp on
  // GNOME. The launch is asynchronous, so both the parent and the reporter are carried across it in
  // a heap `HelpLaunch` and released in the callback; `parent` may legitimately be nullptr (the
  // chooser runs before any window exists).
  auto* launch = new HelpLaunch;
  launch->parent = parent != nullptr ? GTK_WINDOW(g_object_ref(parent)) : nullptr;
  launch->done = std::move(done);
  GtkUriLauncher* launcher = gtk_uri_launcher_new("help:" UDPSCOPE_HELP_NAME);
  gtk_uri_launcher_launch(launcher, parent, nullptr, on_help_launched, launch);
  g_object_unref(launcher);
}

void show_shortcuts(GtkWindow* parent) {
  if (g_shortcuts != nullptr) {
    gtk_window_present(GTK_WINDOW(g_shortcuts));
    return;
  }

  // A `GtkShortcutsWindow` from `src/ui/shortcuts.ui` -- gedit's arrangement, and GTK's own: one
  // section per page, with the sidebar and the search box drawn by the window itself. A UI file
  // rather than widget construction because of the mouse rows: an accelerator cannot spell "Ctrl
  // and drag", and libadwaita's `AdwShortcutsItem` -- the modern replacement -- has no icon
  // property, so its cell reads "No Shortcut". `GtkShortcutsShortcut`'s one generic gesture type
  // draws the `icon` the row names. (The widget is deprecated since 4.20, but this uses none of
  // its functions: the file is loaded as data and presented as a `GtkWindow`.)
  //
  // A builder per opening, not one reused: the window belongs to the builder and `close-request`
  // destroys the window, so the resource is parsed again rather than an already-dead window
  // fetched.
  g_clear_object(&g_shortcuts_ui);
  g_shortcuts_ui = gtk_builder_new_from_resource("/org/udpscope/ui/shortcuts.ui");
  if (g_shortcuts_ui == nullptr) return;
  GObject* overlay = gtk_builder_get_object(g_shortcuts_ui, "help_overlay");
  if (overlay == nullptr) return;
  g_shortcuts = GTK_WIDGET(overlay);
  gtk_window_set_transient_for(GTK_WINDOW(g_shortcuts), parent);
  g_signal_connect(g_shortcuts, "close-request", G_CALLBACK(on_window_close), &g_shortcuts);
  gtk_window_present(GTK_WINDOW(g_shortcuts));
}

void close_help_windows() {
  if (g_about != nullptr) adw_dialog_close(g_about);
  if (g_shortcuts != nullptr) gtk_window_close(GTK_WINDOW(g_shortcuts));
}

}  // namespace udpscope