// Copyright (c) 2010, Niels Martin Hansen
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/// @file selection_controller.h
/// @ingroup controllers
/// @brief Interface declaration for the SubtitleSelectionController

#pragma once

#include <set>

#include <libaegisub/signal.h>

/// @class SelectionController
/// @brief Abstract interface for selection controllers
///
/// Two concepts are managed by implementations of this interface: The concept of the
/// active line, and the concept of the set of selected lines. There is one or zero
/// active lines, the active line is the base for subtitle manipulation in the GUI.
/// The set of selected lines may contain any number of subtitle lines, and those
/// lines are the primary target of subtitle manipulation. In other words, the active
/// line controls what values the user is presented to modify, and the selected set
/// controls what lines are actually modified when the user performs modifications.
/// In most cases, the active line will be a member of the selected set. It will be
/// the responsibility of manipulators to affect the appropriate lines.
///
/// There is only intended to be one instance of a class implementing this interface
/// per editing session, but there may be many different implementations of it.
/// The primary implementation would be the subtitle grid in the main GUI, allowing
/// the user to actively manipulate the active and selected line sets, but other
/// potential implementations are in a test driver and in a non-interactive scenario.
///
/// Objects implementing the SelectionListener interface can subscribe to
/// changes in the active line and the selected set.
template <typename ItemDataType>
class SelectionController {
public:
	typedef std::set<ItemDataType> Selection;

protected:
	agi::signal::Signal<ItemDataType> AnnounceActiveLineChanged;
	agi::signal::Signal<Selection const&, Selection const&> AnnounceSelectedSetChanged;

public:
	/// Virtual destructor for safety
	virtual ~SelectionController() { }

	/// @brief Change the active line
	/// @param new_line Subtitle line to become the new active line
	///
	/// The active line may be changed to nullptr, in which case there is no longer an
	/// active line.
	///
	/// Calling this method should only cause a change notification to be sent if
	/// the active line was actually changed.
	///
	/// This method must not affect the selected set.
	virtual void SetActiveLine(ItemDataType new_line) = 0;

	/// @brief Obtain the active line
	/// @return The active line or nullptr if there is none
	virtual ItemDataType GetActiveLine() const = 0;

	/// @brief Change the selected set
	/// @param new_selection The set of subtitle lines to become the new selected set
	///
	/// Implementations must either completely change the selected set to the new
	/// set provided, or not change the selected set at all. Partial changes are
	/// not allowed.
	///
	/// If no change happens to the selected set, whether because it was refused or
	/// because the new set was identical to the old set, no change notification may
	/// be sent.
	virtual void SetSelectedSet(Selection new_selection) = 0;

	/// @brief Obtain the selected set
	/// @param[out] selection Filled with the selected set on return
	virtual void GetSelectedSet(Selection &selection) const = 0;

	/// @brief Obtain the selected set
	/// @return The selected set
	virtual Selection const& GetSelectedSet() const = 0;

	/// @brief Set both the selected set and active line
	/// @param new_line Subtitle line to become the new active line
	/// @param new_selection The set of subtitle lines to become the new selected set
	///
	/// This sets both the active line and selected set before announcing the
	/// change to either of them, and is guaranteed to announce the active line
	/// change before the selection change.
	virtual void SetSelectionAndActive(Selection new_selection, ItemDataType new_line) = 0;

	/// @brief Change the active line to the next in sequence
	///
	/// If there is no logical next line in sequence, no change happens. This should
	/// also reset the selected set to consist of exactly the active line, if the
	/// active line was changed.
	virtual void NextLine() = 0;

	/// @brief Change the active line to the previous in sequence
	///
	/// If there is no logical previous line in sequence, no change happens. This
	/// should also reset the selected set to consist of exactly the active line, if
	/// the active line was changed.
	virtual void PrevLine() = 0;

	DEFINE_SIGNAL_ADDERS(AnnounceSelectedSetChanged, AddSelectionListener)
	DEFINE_SIGNAL_ADDERS(AnnounceActiveLineChanged, AddActiveLineListener)
};

class AssDialogue;
typedef SelectionController<AssDialogue *> SubtitleSelectionController;
typedef SubtitleSelectionController::Selection SubtitleSelection;