// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: 2026 Martino Ferrari

#include "source_dialog.hpp"

#include "waveform.hpp"

#include "layout_store.hpp"

#include <adwaita.h>
#include <gtk/gtk.h>

#include <unistd.h>

#include <cstdio>
#include <cstdlib>
#include <string>
#include <vector>

namespace udpscope {
namespace {

/// A chooser row's source becomes the connection to open. The interface comes along with the
/// group: it is the local address the join happens on, so storing one without the other would
/// reconnect to the right group on the wrong path.
void apply_source(Config& cfg, const KnownSource& src) {
  cfg.server = src.host;
  cfg.port = src.port;
  cfg.multicast = src.multicast;
  cfg.interface_addr = src.interface_addr;
  // The configuration's own startup settings. They are read *before* the model exists, which is the
  // only moment a buffer size can be applied at all -- and the reason they are stored per
  // configuration rather than only passed on the command line.
  if (src.buffer_mb > 0.0) cfg.buffer_mb = src.buffer_mb;
  cfg.relative_time = src.relative_time;
  cfg.capture_packets = src.capture_packets;
}

/// One line per known source on stderr, in the style of the probes in `ui.cpp`.
void report_sources(const std::vector<KnownSource>& known) {
  std::fprintf(stderr, "[sources] %zu known:", known.size());
  for (const KnownSource& s : known) {
    std::fprintf(stderr, " %s:%u/%s plots=%d signals=%d buffer=%.6g relative=%d capture=%u",
                 s.host.c_str(), s.port, s.config.c_str(), s.rows, s.signals, s.buffer_mb,
                 s.relative_time ? 1 : 0, s.capture_packets);
    if (!s.comment.empty()) std::fprintf(stderr, " note='%s'", s.comment.c_str());
    if (!s.multicast.empty()) std::fprintf(stderr, " multicast=%s", s.multicast.c_str());
    if (!s.interface_addr.empty()) {
      std::fprintf(stderr, " interface=%s", s.interface_addr.c_str());
    }
    std::fprintf(stderr, " |");
  }
  std::fprintf(stderr, "\n");
  std::fflush(stderr);
}

/// The chooser's own state for the life of its nested loop. A plain local in `choose_source()`:
/// the loop runs inside that call, so nothing here outlives the stack frame and there is nothing
/// to free on a handler path.
struct Chooser {
  Config* cfg = nullptr;
  GMainLoop* loop = nullptr;
  bool chosen = false;
  GtkWidget* window = nullptr;
  GtkWidget* list = nullptr;
  std::vector<KnownSource> known;
  /// The Waveforms page: the exports opened before, newest first, and the notebook that holds the
  /// two pages. A waveform is the *other* answer to "which source", so it gets a page of its own
  /// rather than a button that hides a file dialog behind one more click.
  GtkWidget* notebook = nullptr;
  GtkWidget* wave_list = nullptr;
  std::vector<std::string> waves;
  /// The connection form, created on demand. Members of the chooser rather than a heap struct:
  /// the chooser outlives the form by construction, so there is nothing to free on a close path
  /// -- and a dialog whose context is freed by a handler is how this project earned a use-after
  /// -free in the math editor.
  GtkWidget* form = nullptr;
  GtkWidget* form_server = nullptr;
  GtkWidget* form_port = nullptr;
  GtkWidget* form_group = nullptr;
  GtkWidget* form_iface = nullptr;
  GtkWidget* form_connect = nullptr;
  /// The configuration half of the form: what a source's *session* is called and the settings that
  /// can only be applied before the model exists. A new host needs all of them, and so does an
  /// existing one -- which is why the same form is used for both.
  GtkWidget* form_name = nullptr;
  GtkWidget* form_note = nullptr;
  GtkWidget* form_buffer = nullptr;
  GtkWidget* form_relative = nullptr;
  /// The configuration the form is editing: empty for a new host. Copied rather than referenced,
  /// because `chooser_populate()` rebuilds `known` under the form.
  std::string edit_host;
  std::uint16_t edit_port = 0;
  std::string edit_config;
  /// `UDPSCOPE_PROBE_PICK_MS`'s timeout, kept so a pick made before it fires can cancel it. The
  /// probe clears it when it runs: `g_source_remove()` on an id whose source already returned
  /// `G_SOURCE_REMOVE` is a GLib critical, not a no-op.
  guint pick_source = 0;
  /// What the *form* last wrote, for `report_pick()`: a save finishes the chooser and destroys the
  /// list with it, so the row a report would name is gone by the time the probe reads it.
  std::string saved_config;
  std::string saved_note;
};

void chooser_finish(Chooser& c, bool chosen) {
  c.chosen = chosen;
  // Destroy the form first: any path that reaches here while the form is up -- a row click, the
  // Escape key -- would otherwise leave a window whose four handlers are bound to a dead stack
  // frame. `gtk_window_destroy()` rather than `gtk_window_close()`: the pointer is already
  // cleared, so the `close-request` handler is not needed here, and `close()` on an unrealized
  // window returns having done nothing.
  if (c.form != nullptr) {
    GtkWidget* w = c.form;
    c.form = nullptr;  // before the destroy, so the `close-request` handler cannot re-enter
    gtk_window_destroy(GTK_WINDOW(w));
  }
  if (c.window != nullptr) {
    GtkWidget* w = c.window;
    c.window = nullptr;  // before the destroy: `close-request` must not re-enter this
    gtk_window_destroy(GTK_WINDOW(w));
  }
  if (c.loop != nullptr) g_main_loop_quit(c.loop);
}

void chooser_populate(Chooser& c);
void chooser_populate_waves(Chooser& c);
void report_pick(const Chooser& c);
/// Defined below; the row buttons reach it, and the row builder sits above it.
void open_form(Chooser& c, int edit_index);

void on_row_activated(GtkListBox*, GtkListBoxRow* row, gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  const int idx = GPOINTER_TO_INT(g_object_get_data(G_OBJECT(row), "source-index"));
  if (idx < 0 || static_cast<std::size_t>(idx) >= c.known.size()) return;
  const KnownSource& src = c.known[static_cast<std::size_t>(idx)];
  // Picking a configuration *is* choosing it as the active one: the app reads that back when it
  // loads the session, and the next save goes to the same file. Without this, opening `bench`
  // from the chooser would leave the source pointing at whatever was active before.
  set_active_configuration(src.host, src.port, src.config);
  apply_source(*c.cfg, src);
  chooser_finish(c, true);
}

/// One row per waveform opened before, newest first. The name first (that is what a person reads),
/// the directory under it, and a missing file said out loud rather than left to fail on the click.
void chooser_populate_waves(Chooser& c) {
  while (GtkWidget* child = gtk_widget_get_first_child(c.wave_list)) {
    gtk_list_box_remove(GTK_LIST_BOX(c.wave_list), child);
  }
  c.waves = recent_waveforms();
  if (c.waves.empty()) {
    GtkWidget* empty = gtk_label_new("No waveform opened yet -- use Open\xe2\x80\xa6");
    gtk_widget_add_css_class(empty, "dim-label");
    gtk_widget_set_margin_top(empty, 24);
    gtk_widget_set_margin_bottom(empty, 24);
    gtk_list_box_append(GTK_LIST_BOX(c.wave_list), empty);
    gtk_list_box_set_selection_mode(GTK_LIST_BOX(c.wave_list), GTK_SELECTION_NONE);
    return;
  }
  gtk_list_box_set_selection_mode(GTK_LIST_BOX(c.wave_list), GTK_SELECTION_SINGLE);
  for (std::size_t i = 0; i < c.waves.size(); ++i) {
    const std::string& path = c.waves[i];
    GtkWidget* row = gtk_list_box_row_new();
    g_object_set_data(G_OBJECT(row), "wave-index", GINT_TO_POINTER(static_cast<int>(i)));

    GtkWidget* line = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 12);
    gtk_widget_set_margin_start(line, 12);
    gtk_widget_set_margin_end(line, 6);
    gtk_widget_set_margin_top(line, 6);
    gtk_widget_set_margin_bottom(line, 6);
    GtkWidget* text = gtk_box_new(GTK_ORIENTATION_VERTICAL, 2);
    gtk_widget_set_hexpand(text, TRUE);
    const std::size_t slash = path.rfind('/');
    const std::string base = slash == std::string::npos ? path : path.substr(slash + 1);
    GtkWidget* title = gtk_label_new(base.c_str());
    gtk_widget_set_halign(title, GTK_ALIGN_START);
    gtk_box_append(GTK_BOX(text), title);
    const bool present = ::access(path.c_str(), R_OK) == 0;
    std::string sub = present ? path : path + "  (missing)";
    GtkWidget* under = gtk_label_new(sub.c_str());
    gtk_widget_add_css_class(under, "dim-label");
    gtk_widget_set_halign(under, GTK_ALIGN_START);
    gtk_label_set_ellipsize(GTK_LABEL(under), PANGO_ELLIPSIZE_MIDDLE);
    gtk_box_append(GTK_BOX(text), under);
    gtk_box_append(GTK_BOX(line), text);
    gtk_list_box_row_set_child(GTK_LIST_BOX_ROW(row), line);
    gtk_list_box_append(GTK_LIST_BOX(c.wave_list), row);
  }
}

void on_wave_activated(GtkListBox*, GtkListBoxRow* row, gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  if (row == nullptr) return;
  const int idx = GPOINTER_TO_INT(g_object_get_data(G_OBJECT(row), "wave-index"));
  if (idx < 0 || static_cast<std::size_t>(idx) >= c.waves.size()) return;
  const std::string& path = c.waves[static_cast<std::size_t>(idx)];
  if (::access(path.c_str(), R_OK) != 0) {
    std::fprintf(stderr, "[sources] waveform is gone: %s\n", path.c_str());
    std::fflush(stderr);
    return;
  }
  // The file *is* the source: the chooser's answer is a path, not a socket.
  c.cfg->open_waveform = path;
  report_pick(c);
  chooser_finish(c, true);
}

void on_wave_open_done(GObject* source, GAsyncResult* result, gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  GFile* file = gtk_file_dialog_open_finish(GTK_FILE_DIALOG(source), result, nullptr);
  if (file == nullptr) return;  // cancelled
  char* path = g_file_get_path(file);
  g_object_unref(file);
  if (path != nullptr) {
    c.cfg->open_waveform = path;
    g_free(path);
    report_pick(c);
    chooser_finish(c, true);
  }
}

void on_wave_open_clicked(GtkButton*, gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  GtkFileDialog* dialog = gtk_file_dialog_new();
  gtk_file_dialog_set_title(dialog, "Open an exported waveform");
  GtkFileFilter* filter = gtk_file_filter_new();
  gtk_file_filter_set_name(filter, "NumPy export (*.npy)");
  gtk_file_filter_add_pattern(filter, "*.npy");
  GListStore* filters = g_list_store_new(GTK_TYPE_FILE_FILTER);
  g_list_store_append(filters, filter);
  gtk_file_dialog_set_filters(dialog, G_LIST_MODEL(filters));
  gtk_file_dialog_open(dialog, GTK_WINDOW(c.window), nullptr, on_wave_open_done, &c);
  g_object_unref(filters);
  g_object_unref(filter);
  g_object_unref(dialog);
}

void on_edit_clicked(GtkButton* button, gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  const int idx = GPOINTER_TO_INT(g_object_get_data(G_OBJECT(button), "source-index"));
  if (idx < 0 || static_cast<std::size_t>(idx) >= c.known.size()) return;
  open_form(c, idx);
}

void on_forget_clicked(GtkButton* button, gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  const int idx = GPOINTER_TO_INT(g_object_get_data(G_OBJECT(button), "source-index"));
  if (idx < 0 || static_cast<std::size_t>(idx) >= c.known.size()) return;
  forget_source(c.known[static_cast<std::size_t>(idx)]);
  // Repopulate rather than remove one row: the rows carry their index into `known`, and dropping
  // an entry renumbers every later one. Re-reading is also the honest answer to "did it go".
  chooser_populate(c);
}

/// Fills the list box from `known_sources()`. Called again after a forget.
void chooser_populate(Chooser& c) {
  while (GtkWidget* child = gtk_widget_get_first_child(c.list)) {
    gtk_list_box_remove(GTK_LIST_BOX(c.list), child);
  }
  c.known = known_sources();

  if (c.known.empty()) {
    GtkWidget* empty = gtk_label_new("No saved sources yet.");
    gtk_widget_add_css_class(empty, "dim-label");
    gtk_widget_set_margin_top(empty, 24);
    gtk_widget_set_margin_bottom(empty, 24);
    // GTK4 auto-wraps any non-row widget appended to a `GtkListBox` in a row, so this is
    // activatable -- but the wrapped row carries no `"source-index"` data, `g_object_get_data()`
    // returns null, the index reads 0, and `on_row_activated`'s bounds check refuses it.
    gtk_list_box_append(GTK_LIST_BOX(c.list), empty);
    gtk_list_box_set_selection_mode(GTK_LIST_BOX(c.list), GTK_SELECTION_NONE);
    return;
  }
  gtk_list_box_set_selection_mode(GTK_LIST_BOX(c.list), GTK_SELECTION_SINGLE);

  for (std::size_t i = 0; i < c.known.size(); ++i) {
    const KnownSource& s = c.known[i];
    GtkWidget* row = gtk_list_box_row_new();
    g_object_set_data(G_OBJECT(row), "source-index", GINT_TO_POINTER(static_cast<int>(i)));

    GtkWidget* line = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 12);
    gtk_widget_set_margin_start(line, 12);
    gtk_widget_set_margin_end(line, 6);
    gtk_widget_set_margin_top(line, 6);
    gtk_widget_set_margin_bottom(line, 6);

    GtkWidget* text = gtk_box_new(GTK_ORIENTATION_VERTICAL, 2);
    gtk_widget_set_hexpand(text, TRUE);

    // The *server*, even for a multicast session: that is the host the file is named after and
    // the one CONFIG is fetched from. Titling the row by the group would name it after something
    // that is not its identity.
    const std::string title = s.host + ":" + std::to_string(s.port) + "  \u00b7  " + s.config;
    GtkWidget* title_label = gtk_label_new(title.c_str());
    gtk_widget_set_halign(title_label, GTK_ALIGN_START);
    gtk_box_append(GTK_BOX(text), title_label);

    // The note first when there is one: it is what tells two configurations of one source apart,
    // and a list that shows only counts makes the user open them to find out.
    if (!s.comment.empty()) {
      GtkWidget* note = gtk_label_new(s.comment.c_str());
      gtk_widget_set_halign(note, GTK_ALIGN_START);
      gtk_label_set_ellipsize(GTK_LABEL(note), PANGO_ELLIPSIZE_END);
      gtk_box_append(GTK_BOX(text), note);
    }

    std::string sub = std::to_string(s.rows) + (s.rows == 1 ? " plot, " : " plots, ") +
                      std::to_string(s.signals) + (s.signals == 1 ? " signal" : " signals");
    if (s.buffer_mb > 0.0) {
      sub += ", buffer " + std::to_string(static_cast<int>(s.buffer_mb)) + " MB";
    }
    if (s.relative_time) sub += ", relative time";
    if (s.capture_packets > 0) {
      sub += ", capture " + std::to_string(s.capture_packets) + " packets";
    }
    if (!s.multicast.empty()) sub += ", multicast " + s.multicast;
    GtkWidget* sub_label = gtk_label_new(sub.c_str());
    gtk_widget_add_css_class(sub_label, "dim-label");
    gtk_widget_set_halign(sub_label, GTK_ALIGN_START);
    gtk_box_append(GTK_BOX(text), sub_label);
    gtk_box_append(GTK_BOX(line), text);

    GtkWidget* edit = gtk_button_new_from_icon_name("document-edit-symbolic");
    gtk_widget_set_tooltip_text(edit,
                                "Edit this configuration: its name and note, the buffer size and "
                                "the clock, or the address it points at");
    gtk_widget_add_css_class(edit, "flat");
    gtk_widget_set_valign(edit, GTK_ALIGN_CENTER);
    g_object_set_data(G_OBJECT(edit), "source-index", GINT_TO_POINTER(static_cast<int>(i)));
    g_signal_connect(edit, "clicked", G_CALLBACK(on_edit_clicked), &c);
    gtk_box_append(GTK_BOX(line), edit);

    GtkWidget* forget = gtk_button_new_from_icon_name("window-close-symbolic");
    gtk_widget_set_tooltip_text(forget, "Forget this configuration (deletes its saved session)");
    gtk_widget_add_css_class(forget, "flat");
    gtk_widget_set_valign(forget, GTK_ALIGN_CENTER);
    g_object_set_data(G_OBJECT(forget), "source-index", GINT_TO_POINTER(static_cast<int>(i)));
    g_signal_connect(forget, "clicked", G_CALLBACK(on_forget_clicked), &c);
    gtk_box_append(GTK_BOX(line), forget);

    gtk_list_box_row_set_child(GTK_LIST_BOX_ROW(row), line);
    gtk_list_box_append(GTK_LIST_BOX(c.list), row);
  }
}

void form_close(Chooser& c) {
  if (c.form == nullptr) return;
  GtkWidget* w = c.form;
  c.form = nullptr;  // before the close, so the handler cannot re-enter
  gtk_window_close(GTK_WINDOW(w));
}

void on_form_server_changed(GtkEditable* entry, gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  if (c.form_connect == nullptr) return;
  // The only validation here. A *malformed* address is the acquisition layer's to report -- it
  // already does, and the starvation notice covers a source that takes the socket and says
  // nothing -- so checking it twice would be two expressions of one rule.
  gtk_widget_set_sensitive(c.form_connect, gtk_entry_buffer_get_length(
                                               gtk_entry_get_buffer(GTK_ENTRY(entry))) > 0);
}

void on_form_connect(GtkButton*, gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  const char* server = gtk_editable_get_text(GTK_EDITABLE(c.form_server));
  if (server == nullptr || server[0] == '\0') return;
  const std::string host = server;
  const std::uint16_t port = static_cast<std::uint16_t>(
      gtk_spin_button_get_value_as_int(GTK_SPIN_BUTTON(c.form_port)));
  const std::string group = gtk_editable_get_text(GTK_EDITABLE(c.form_group));
  const std::string iface = gtk_editable_get_text(GTK_EDITABLE(c.form_iface));
  std::string name = gtk_editable_get_text(GTK_EDITABLE(c.form_name));
  const std::string note = gtk_editable_get_text(GTK_EDITABLE(c.form_note));
  const double buffer_mb = gtk_spin_button_get_value(GTK_SPIN_BUTTON(c.form_buffer));
  const bool relative = gtk_switch_get_active(GTK_SWITCH(c.form_relative));
  if (name.empty()) name = "default";

  c.cfg->server = host;
  c.cfg->port = port;
  c.cfg->multicast = group;
  c.cfg->interface_addr = iface;
  // The startup settings. Applied here because this runs *before* `ScopeModel` exists, which is the
  // only moment a buffer size can be applied at all -- and stored, so the next run gets them back.
  c.cfg->buffer_mb = buffer_mb;
  c.cfg->relative_time = relative;

  LayoutState st;
  if (!c.edit_config.empty()) {
    // An edit keeps everything the configuration already holds -- plots, calibration, math,
    // measurements -- and changes only what the form shows.
    load_layout(configuration_path(c.edit_host, c.edit_port, c.edit_config), st);
  }
  st.comment = note;
  st.buffer_mb = buffer_mb;
  st.relative_time = relative;
  st.multicast = group;
  st.interface_addr = iface;

  const bool editing = !c.edit_config.empty();
  const bool moved =
      editing && (c.edit_host != host || c.edit_port != port || c.edit_config != name);
  if (save_layout(configuration_path(host, port, name), st)) {
    set_active_configuration(host, port, name);
    // A renamed configuration, or one re-addressed, is a *move*: the old file has no reason to exist
    // and leaving it would list the same session twice.
    if (moved) forget_configuration(c.edit_host, c.edit_port, c.edit_config);
    c.saved_config = name;
    c.saved_note = note;
    std::fprintf(stderr,
                 "[sources] configuration %s: %s:%u/%s note='%s' buffer=%.6g relative=%d\n",
                 editing ? "saved" : "created", host.c_str(), port, name.c_str(), note.c_str(),
                 buffer_mb, relative ? 1 : 0);
    std::fflush(stderr);
  } else {
    std::fprintf(stderr, "[sources] configuration write failed: %s:%u/%s\n", host.c_str(), port,
                 name.c_str());
    std::fflush(stderr);
  }
  form_close(c);
  chooser_finish(c, true);
}

/// A labelled row for the form's grid.
GtkWidget* form_field(GtkWidget* grid, int row, const char* label, GtkWidget* widget) {
  GtkWidget* l = gtk_label_new(label);
  gtk_widget_set_halign(l, GTK_ALIGN_END);
  gtk_grid_attach(GTK_GRID(grid), l, 0, row, 1, 1);
  gtk_widget_set_hexpand(widget, TRUE);
  gtk_grid_attach(GTK_GRID(grid), widget, 1, row, 1, 1);
  return widget;
}

/// Opens the connection form: on a new host, or on an existing configuration (`edit_index`). One
/// form for both, because the fields are the same and a configuration *is* a host plus its
/// settings -- the only difference is where the values start and what the button is called.
void open_form(Chooser& c, int edit_index = -1) {
  if (c.form != nullptr) {
    gtk_window_present(GTK_WINDOW(c.form));
    return;
  }
  const KnownSource* src =
      edit_index >= 0 && static_cast<std::size_t>(edit_index) < c.known.size()
          ? &c.known[static_cast<std::size_t>(edit_index)]
          : nullptr;
  c.edit_host = src != nullptr ? src->host : std::string();
  c.edit_port = src != nullptr ? src->port : 0;
  c.edit_config = src != nullptr ? src->config : std::string();

  c.form = gtk_window_new();
  gtk_window_set_title(GTK_WINDOW(c.form), src != nullptr ? "Edit configuration" : "New host");
  gtk_window_set_transient_for(GTK_WINDOW(c.form), GTK_WINDOW(c.window));
  gtk_window_set_modal(GTK_WINDOW(c.form), TRUE);

  GtkWidget* box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 12);
  gtk_widget_set_margin_start(box, 12);
  gtk_widget_set_margin_end(box, 12);
  gtk_widget_set_margin_top(box, 12);
  gtk_widget_set_margin_bottom(box, 12);
  gtk_window_set_child(GTK_WINDOW(c.form), box);

  GtkWidget* grid = gtk_grid_new();
  gtk_grid_set_row_spacing(GTK_GRID(grid), 6);
  gtk_grid_set_column_spacing(GTK_GRID(grid), 12);
  gtk_box_append(GTK_BOX(box), grid);

  c.form_server = form_field(grid, 0, "Server", gtk_entry_new());
  gtk_editable_set_text(GTK_EDITABLE(c.form_server),
                        src != nullptr ? src->host.c_str() : "127.0.0.1");
  // A spin button holds no decimals by default, which is right for a port and wrong for every
  // other numeric field in this project -- see the math dialog's fields.
  c.form_port = form_field(grid, 1, "Port", gtk_spin_button_new_with_range(1, 65535, 1));
  gtk_spin_button_set_value(GTK_SPIN_BUTTON(c.form_port), src != nullptr ? src->port : 8000);
  c.form_group = form_field(grid, 2, "Multicast group", gtk_entry_new());
  gtk_entry_set_placeholder_text(GTK_ENTRY(c.form_group), "empty = unicast");
  gtk_editable_set_text(GTK_EDITABLE(c.form_group),
                        src != nullptr ? src->multicast.c_str() : "");
  c.form_iface = form_field(grid, 3, "Interface", gtk_entry_new());
  gtk_entry_set_placeholder_text(GTK_ENTRY(c.form_iface), "empty = default route");
  gtk_editable_set_text(GTK_EDITABLE(c.form_iface),
                        src != nullptr ? src->interface_addr.c_str() : "");

  // The session half: what this source's configuration is called, and the settings that have to be
  // decided before the first socket is opened.
  GtkWidget* heading = gtk_label_new(nullptr);
  gtk_label_set_markup(GTK_LABEL(heading), "<b>Configuration</b>");
  gtk_widget_set_halign(heading, GTK_ALIGN_START);
  gtk_widget_set_margin_top(heading, 8);
  gtk_grid_attach(GTK_GRID(grid), heading, 0, 4, 2, 1);

  c.form_name = form_field(grid, 5, "Name", gtk_entry_new());
  gtk_entry_set_placeholder_text(GTK_ENTRY(c.form_name), "default");
  gtk_editable_set_text(GTK_EDITABLE(c.form_name),
                        src != nullptr ? src->config.c_str() : "default");
  c.form_note = form_field(grid, 6, "Note", gtk_entry_new());
  gtk_entry_set_placeholder_text(GTK_ENTRY(c.form_note), "what this configuration is for");
  gtk_editable_set_text(GTK_EDITABLE(c.form_note),
                        src != nullptr ? src->comment.c_str() : "");
  c.form_buffer = form_field(grid, 7, "Buffer MB", gtk_spin_button_new_with_range(1, 65536, 1));
  gtk_widget_set_tooltip_text(c.form_buffer,
                              "sample buffer per source, applied when this source is opened");
  gtk_spin_button_set_value(GTK_SPIN_BUTTON(c.form_buffer),
                            src != nullptr && src->buffer_mb > 0.0
                                ? src->buffer_mb
                                : std::max(1.0, c.cfg->buffer_mb));
  GtkWidget* relative = gtk_switch_new();
  gtk_widget_set_halign(relative, GTK_ALIGN_START);
  gtk_widget_set_tooltip_text(relative,
                              "plot time from the packet counter and the declared rate, instead "
                              "of the stream's own time signal (--relative-time)");
  gtk_switch_set_active(GTK_SWITCH(relative),
                        src != nullptr ? src->relative_time : c.cfg->relative_time);
  c.form_relative = form_field(grid, 8, "Relative time", relative);

  GtkWidget* actions = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 6);
  gtk_widget_set_halign(actions, GTK_ALIGN_END);
  GtkWidget* cancel = gtk_button_new_with_label("Cancel");
  g_signal_connect(cancel, "clicked", G_CALLBACK(+[](GtkButton*, gpointer user) {
                     form_close(*static_cast<Chooser*>(user));
                   }),
                   &c);
  c.form_connect = gtk_button_new_with_label(src != nullptr ? "Save" : "Connect");
  g_signal_connect(c.form_connect, "clicked", G_CALLBACK(on_form_connect), &c);
  gtk_box_append(GTK_BOX(actions), cancel);
  gtk_box_append(GTK_BOX(actions), c.form_connect);
  gtk_box_append(GTK_BOX(box), actions);

  g_signal_connect(c.form_server, "changed", G_CALLBACK(on_form_server_changed), &c);
  // `close-request` clears the pointer, and only a *close* emits it: `gtk_window_destroy()` does
  // not, which is how the math dialog once kept presenting a finalized window.
  g_signal_connect(c.form, "close-request", G_CALLBACK(+[](GtkWindow*, gpointer user) {
                     static_cast<Chooser*>(user)->form = nullptr;
                     return FALSE;
                   }),
                   &c);

  gtk_window_present(GTK_WINDOW(c.form));
  gtk_widget_grab_focus(c.form_server);
}

/// What the pick probes report: the connection the chooser came back with. One helper rather than
/// the same four lines in each branch, since both probes assert against this exact line.
void report_pick(const Chooser& c) {
  if (!c.cfg->open_waveform.empty()) {
    std::fprintf(stderr, "[sources] picked waveform %s\n", c.cfg->open_waveform.c_str());
    std::fflush(stderr);
    return;
  }
  // The settings the configuration carried, not just the address: a pick that dropped the buffer
  // size would look identical here otherwise, and the buffer is the one of them a user notices
  // only after a long capture has been sized wrong.
  std::fprintf(stderr,
               "[sources] picked %s:%u multicast=%s interface=%s buffer=%.6g relative=%d "
               "capture=%u config=%s note='%s'\n",
               c.cfg->server.c_str(), c.cfg->port, c.cfg->multicast.c_str(),
               c.cfg->interface_addr.c_str(), c.cfg->buffer_mb, c.cfg->relative_time ? 1 : 0,
               c.cfg->capture_packets,
               (c.saved_config.empty() ? (c.known.empty() ? "-" : c.known.front().config)
                                       : c.saved_config)
                   .c_str(),
               (c.saved_config.empty() ? (c.known.empty() ? "-" : c.known.front().comment)
                                       : c.saved_note)
                   .c_str());
  std::fflush(stderr);
}

gboolean on_chooser_close(GtkWindow*, gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  c.window = nullptr;  // GTK destroys it for us on the default handler
  chooser_finish(c, false);
  return FALSE;
}

gboolean on_chooser_key(GtkEventControllerKey*, guint keyval, guint, GdkModifierType,
                        gpointer user) {
  if (keyval != GDK_KEY_Escape) return FALSE;
  chooser_finish(*static_cast<Chooser*>(user), false);
  return TRUE;
}

/// `UDPSCOPE_PROBE_PICK_MS`: activate the first row, the way a click does.
/// `UDPSCOPE_PROBE_NEWHOST=host:port` drives the form instead of a row. The crash surface of a
/// dialog built, filled and destroyed is as much the point as the values, the same way
/// `UDPSCOPE_PROBE_FIELDS_MS` is in `ui.cpp`.
gboolean pick_probe(gpointer user) {
  Chooser& c = *static_cast<Chooser*>(user);
  // Every path below returns `G_SOURCE_REMOVE`, so the source is gone the moment this returns and
  // its id is stale. Clear it here rather than on each path: `choose_source()`'s cancel-the-pending
  // -probe call would otherwise be a GLib critical on every run that let the probe fire.
  c.pick_source = 0;

  // `UDPSCOPE_PROBE_WAVEFORMS=1` is the waveforms page without a display: the recent list, and the
  // page selected the way a click on its tab does. `UDPSCOPE_PROBE_WAVE=<path>` is the file dialog's
  // answer without the dialog -- the same field, set the same way.
  if (g_getenv("UDPSCOPE_PROBE_WAVEFORMS") != nullptr) {
    if (c.notebook != nullptr) gtk_notebook_set_current_page(GTK_NOTEBOOK(c.notebook), 1);
    std::fprintf(stderr, "[sources] waveforms: %zu recent", c.waves.size());
    for (const std::string& p : c.waves) {
      std::fprintf(stderr, " %s(%s)", p.c_str(), ::access(p.c_str(), R_OK) == 0 ? "ok" : "missing");
    }
    std::fprintf(stderr, " page=%d\n",
                 static_cast<int>(gtk_notebook_get_current_page(GTK_NOTEBOOK(c.notebook))));
    std::fflush(stderr);
  }
  if (const char* path = g_getenv("UDPSCOPE_PROBE_WAVE")) {
    c.cfg->open_waveform = path;
    report_pick(c);
    chooser_finish(c, true);
    return G_SOURCE_REMOVE;
  }

  // `UDPSCOPE_PROBE_NEWHOST=host:port` drives the form instead of a row: the address, and the four
  // things a host could not be given before -- a name, a note, a buffer size and a clock.
  if (const char* spec = g_getenv("UDPSCOPE_PROBE_NEWHOST")) {
    open_form(c);
    const std::string s = spec;
    const std::size_t colon = s.rfind(':');
    gtk_editable_set_text(GTK_EDITABLE(c.form_server),
                          colon == std::string::npos ? s.c_str() : s.substr(0, colon).c_str());
    if (colon != std::string::npos) {
      gtk_spin_button_set_value(GTK_SPIN_BUTTON(c.form_port), std::atof(s.c_str() + colon + 1));
    }
    gtk_editable_set_text(GTK_EDITABLE(c.form_name), "probe-host");
    gtk_editable_set_text(GTK_EDITABLE(c.form_note), "made by the new-host probe");
    gtk_spin_button_set_value(GTK_SPIN_BUTTON(c.form_buffer), 32);
    gtk_switch_set_active(GTK_SWITCH(c.form_relative), TRUE);
    std::fprintf(stderr,
                 "[sources] form: name='%s' note='%s' buffer=%.6g relative=%d "
                 "connect_sensitive=%d\n",
                 gtk_editable_get_text(GTK_EDITABLE(c.form_name)),
                 gtk_editable_get_text(GTK_EDITABLE(c.form_note)),
                 gtk_spin_button_get_value(GTK_SPIN_BUTTON(c.form_buffer)),
                 gtk_switch_get_active(GTK_SWITCH(c.form_relative)) ? 1 : 0,
                 gtk_widget_get_sensitive(c.form_connect) ? 1 : 0);
    g_signal_emit_by_name(c.form_connect, "clicked");
    report_pick(c);
    return G_SOURCE_REMOVE;
  }

  // `UDPSCOPE_PROBE_EDITHOST=host:port` opens the existing configuration's form, changes its
  // settings and saves: the path a user reaches by clicking the row's pencil.
  if (const char* spec = g_getenv("UDPSCOPE_PROBE_EDITHOST")) {
    const std::string want = spec;
    int idx = -1;
    for (std::size_t i = 0; i < c.known.size(); ++i) {
      if (c.known[i].host + ":" + std::to_string(c.known[i].port) == want) {
        idx = static_cast<int>(i);
        break;
      }
    }
    if (idx < 0) {
      std::fprintf(stderr, "[sources] edit: no configuration for '%s'\n", want.c_str());
      std::fflush(stderr);
      chooser_finish(c, false);
      return G_SOURCE_REMOVE;
    }
    open_form(c, idx);
    // The reading is the *pre-fill*: an edit form that opens empty is the defect this asserts
    // against, and the button's label says which mode it is in.
    std::fprintf(stderr,
                 "[sources] edit form: name='%s' note='%s' buffer=%.6g relative=%d button='%s'\n",
                 gtk_editable_get_text(GTK_EDITABLE(c.form_name)),
                 gtk_editable_get_text(GTK_EDITABLE(c.form_note)),
                 gtk_spin_button_get_value(GTK_SPIN_BUTTON(c.form_buffer)),
                 gtk_switch_get_active(GTK_SWITCH(c.form_relative)) ? 1 : 0,
                 gtk_button_get_label(GTK_BUTTON(c.form_connect)));
    gtk_editable_set_text(GTK_EDITABLE(c.form_note), "edited by the probe");
    gtk_spin_button_set_value(GTK_SPIN_BUTTON(c.form_buffer), 16);
    gtk_switch_set_active(GTK_SWITCH(c.form_relative), FALSE);
    // `UDPSCOPE_PROBE_EDITNAME=new-name` also renames it, which is a *move*: the old file must not
    // survive, or the chooser lists the same session twice.
    if (const char* rename_to = g_getenv("UDPSCOPE_PROBE_EDITNAME")) {
      gtk_editable_set_text(GTK_EDITABLE(c.form_name), rename_to);
    }
    g_signal_emit_by_name(c.form_connect, "clicked");
    report_pick(c);
    return G_SOURCE_REMOVE;
  }

  // Check the source list rather than the row count: `gtk_list_box_append` auto-wraps any
  // non-row widget in a `GtkListBoxRow`, so `gtk_list_box_get_row_at_index` returns non-null
  // even when the only list child is the empty-state placeholder label.
  if (c.known.empty()) {
    std::fprintf(stderr, "[sources] picked nothing: the list is empty\n");
    std::fflush(stderr);
    chooser_finish(c, false);
    return G_SOURCE_REMOVE;
  }
  GtkListBoxRow* row = gtk_list_box_get_row_at_index(GTK_LIST_BOX(c.list), 0);
  // `row-activated`, not `gtk_widget_activate()`: this project has already learned that
  // activating a widget takes a path a real click does not (a `GtkButton` holds for its 250 ms
  // ACTIVATE_TIMEOUT and then emits into a widget a rebuild has destroyed).
  g_signal_emit_by_name(c.list, "row-activated", row);
  report_pick(c);
  return G_SOURCE_REMOVE;
}

}  // namespace

void apply_stored_settings(Config& cfg) {
  const std::string want = active_configuration(cfg.server, cfg.port);
  if (want.empty()) return;
  LayoutState st;
  if (!load_layout(configuration_path(cfg.server, cfg.port, want), st)) return;
  // Only where the command line was silent: a flag the user typed wins, because it is the more
  // recent statement of intent -- and the file is not a place to hide a surprise from the ones who
  // did type it.
  if (!cfg.buffer_mb_specified && st.buffer_mb > 0.0) cfg.buffer_mb = st.buffer_mb;
  if (st.relative_time) cfg.relative_time = true;
  if (cfg.capture_packets == 0 && st.capture_packets > 0) cfg.capture_packets = st.capture_packets;
  const bool applied = (!cfg.buffer_mb_specified && st.buffer_mb > 0.0) || st.relative_time ||
                       st.capture_packets > 0;
  if (applied) {
    std::fprintf(stderr,
                 "[sources] settings from configuration '%s': buffer=%.6g relative=%d capture=%u\n",
                 want.c_str(), cfg.buffer_mb, cfg.relative_time ? 1 : 0, cfg.capture_packets);
    std::fflush(stderr);
  }
}

bool choose_source(Config& cfg) {
  const std::vector<KnownSource> known = known_sources();

  // The discovery half, checkable with no display at all: this returns before `gtk_init()`, so
  // it asserts what the list found without needing an X server or a GL context. False means the
  // caller exits 0, which is what "list and exit" wants.
  if (g_getenv("UDPSCOPE_PROBE_SOURCES") != nullptr) {
    report_sources(known);
    return false;
  }

  // `adw_init()` rather than `gtk_init()`: it does everything the latter does and also
  // installs libadwaita's stylesheet, which the shortcut overview's `AdwShortcutsDialog`
  // is drawn with. Both are idempotent, so `run_ui()` calling it again costs nothing.
  adw_init();

  Chooser c;
  c.cfg = &cfg;
  c.window = gtk_window_new();
  gtk_window_set_title(GTK_WINDOW(c.window), "udpscope \xe2\x80\x94 choose a source");
  gtk_window_set_default_size(GTK_WINDOW(c.window), 420, 320);

  GtkWidget* box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
  gtk_window_set_child(GTK_WINDOW(c.window), box);

  // Two pages under one window: the sources it can connect to, and the waveforms it can open. A
  // waveform is not a source with a file in place of an address -- there is no socket and nothing
  // arrives -- so it is a *page* rather than a field, which is also where its history belongs.
  c.notebook = gtk_notebook_new();
  gtk_widget_set_vexpand(c.notebook, TRUE);
  gtk_box_append(GTK_BOX(box), c.notebook);

  GtkWidget* scroller = gtk_scrolled_window_new();
  gtk_widget_set_vexpand(scroller, TRUE);
  gtk_scrolled_window_set_policy(GTK_SCROLLED_WINDOW(scroller), GTK_POLICY_NEVER,
                                 GTK_POLICY_AUTOMATIC);
  c.list = gtk_list_box_new();
  gtk_list_box_set_activate_on_single_click(GTK_LIST_BOX(c.list), TRUE);
  g_signal_connect(c.list, "row-activated", G_CALLBACK(on_row_activated), &c);
  gtk_scrolled_window_set_child(GTK_SCROLLED_WINDOW(scroller), c.list);
  gtk_notebook_append_page(GTK_NOTEBOOK(c.notebook), scroller, gtk_label_new("Sources"));

  GtkWidget* wave_page = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
  GtkWidget* wave_scroller = gtk_scrolled_window_new();
  gtk_widget_set_vexpand(wave_scroller, TRUE);
  gtk_scrolled_window_set_policy(GTK_SCROLLED_WINDOW(wave_scroller), GTK_POLICY_NEVER,
                                 GTK_POLICY_AUTOMATIC);
  c.wave_list = gtk_list_box_new();
  gtk_list_box_set_activate_on_single_click(GTK_LIST_BOX(c.wave_list), TRUE);
  g_signal_connect(c.wave_list, "row-activated", G_CALLBACK(on_wave_activated), &c);
  gtk_scrolled_window_set_child(GTK_SCROLLED_WINDOW(wave_scroller), c.wave_list);
  gtk_box_append(GTK_BOX(wave_page), wave_scroller);
  GtkWidget* wave_actions = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 6);
  gtk_widget_set_halign(wave_actions, GTK_ALIGN_END);
  gtk_widget_set_margin_top(wave_actions, 6);
  gtk_widget_set_margin_bottom(wave_actions, 6);
  gtk_widget_set_margin_end(wave_actions, 12);
  GtkWidget* wave_open = gtk_button_new_with_label("Open\xe2\x80\xa6");
  gtk_widget_set_tooltip_text(wave_open, "choose an exported .npy to view and analyse");
  g_signal_connect(wave_open, "clicked", G_CALLBACK(on_wave_open_clicked), &c);
  gtk_box_append(GTK_BOX(wave_actions), wave_open);
  gtk_box_append(GTK_BOX(wave_page), wave_actions);
  gtk_notebook_append_page(GTK_NOTEBOOK(c.notebook), wave_page, gtk_label_new("Waveforms"));
  chooser_populate_waves(c);

  GtkWidget* actions = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 6);
  gtk_widget_set_margin_start(actions, 12);
  gtk_widget_set_margin_end(actions, 12);
  gtk_widget_set_margin_top(actions, 12);
  gtk_widget_set_margin_bottom(actions, 12);
  gtk_widget_set_halign(actions, GTK_ALIGN_END);
  GtkWidget* new_host = gtk_button_new_with_label("New host\xe2\x80\xa6");
  g_signal_connect(new_host, "clicked", G_CALLBACK(+[](GtkButton*, gpointer user) {
                     open_form(*static_cast<Chooser*>(user));
                   }),
                   &c);
  GtkWidget* cancel = gtk_button_new_with_label("Cancel");
  g_signal_connect(cancel, "clicked", G_CALLBACK(+[](GtkButton*, gpointer user) {
                     chooser_finish(*static_cast<Chooser*>(user), false);
                   }),
                   &c);
  gtk_box_append(GTK_BOX(actions), new_host);
  gtk_box_append(GTK_BOX(actions), cancel);
  gtk_box_append(GTK_BOX(box), actions);

  chooser_populate(c);
  if (c.known.empty()) gtk_widget_grab_focus(new_host);

  g_signal_connect(c.window, "close-request", G_CALLBACK(on_chooser_close), &c);
  GtkEventController* keys = gtk_event_controller_key_new();
  g_signal_connect(keys, "key-pressed", G_CALLBACK(on_chooser_key), &c);
  gtk_widget_add_controller(c.window, keys);

  gtk_window_present(GTK_WINDOW(c.window));

  // Keep the timeout id so it can be cancelled if the chooser finishes before it fires. A row
  // clicked before UDPSCOPE_PROBE_PICK_MS elapses would otherwise leave an armed source on the
  // default main context pointing at the now-gone stack frame.
  if (const char* env = g_getenv("UDPSCOPE_PROBE_PICK_MS")) {
    c.pick_source = g_timeout_add(static_cast<guint>(std::atoi(env)), pick_probe, &c);
  }

  c.loop = g_main_loop_new(nullptr, FALSE);
  g_main_loop_run(c.loop);
  g_main_loop_unref(c.loop);
  c.loop = nullptr;
  if (c.pick_source != 0) g_source_remove(c.pick_source);
  return c.chosen;
}

}  // namespace udpscope