/* $Id$ */

/** @file ai_subsidy.hpp Everything to query subsidies. */

#ifndef AI_SUBSIDY_HPP
#define AI_SUBSIDY_HPP

#include "ai_object.hpp"
#include "ai_company.hpp"

/**
 * Class that handles all subsidy related functions.
 */
class AISubsidy : public AIObject {
public:
	static const char *GetClassName() { return "AISubsidy"; }

	/**
	 * Check whether this is a valid SubsidyID.
	 * @param subsidy_id The SubsidyID to check.
	 * @return True if and only if this subsidy is still valid.
	 */
	static bool IsValidSubsidy(SubsidyID subsidy_id);

	/**
	 * Checks whether this subsidy is already awarded to some company.
	 * @param subsidy_id The SubsidyID to check.
	 * @pre IsValidSubsidy(subsidy).
	 * @return True if and only if this subsidy is already awarded.
	 */
	static bool IsAwarded(SubsidyID subsidy_id);

	/**
	 * Get the company index of the company this subsidy is awarded to.
	 * @param subsidy_id The SubsidyID to check.
	 * @pre IsAwarded(subsidy_id).
	 * @return The companyindex of the company this subsidy is awarded to.
	 */
	static AICompany::CompanyID GetAwardedTo(SubsidyID subsidy_id);

	/**
	 * Get the date this subsidy expires. In case the subsidy is already
	 *  awarded, return the date the subsidy expires, else, return the date the
	 *  offer expires.
	 * @param subsidy_id The SubsidyID to check.
	 * @pre IsValidSubsidy(subsidy_id).
	 * @return The last valid date of this subsidy.
	 * @note The return value of this function will change if the subsidy is
	 *  awarded.
	 */
	static int32 GetExpireDate(SubsidyID subsidy_id);

	/**
	 * Get the cargo type that has to be transported in order to be awarded this
	 *  subsidy.
	 * @param subsidy_id The SubsidyID to check.
	 * @pre IsValidSubsidy(subsidy_id).
	 * @return The cargo type to transport.
	 */
	static CargoID GetCargoType(SubsidyID subsidy_id);

	/**
	 * Is the source of the subsidy a town or an industry.
	 * @param subsidy_id The SubsidyID to check.
	 * @pre IsValidSubsidy(subsidy_id) && !IsAwarded(subsidy_id).
	 * @return True if the source is a town, false if it is an industry.
	 */
	static bool SourceIsTown(SubsidyID subsidy_id);

	/**
	 * Return the source TownID/IndustryID/StationID the subsidy is for.
	 * 1) IsAwarded(subsidy_id) -> return the StationID the subsidy is awarded to.
	 * 2) !IsAwarded(subsidy_id) && SourceIsTown(subsidy_id) -> return the TownID.
	 * 3) !IsAwarded(subsidy_id) && !SourceIsTown(subsidy_id) -> return the IndustryID.
	 * @param subsidy_id The SubsidyID to check.
	 * @pre IsValidSubsidy(subsidy_id).
	 * @return One of TownID/IndustryID/StationID.
	 */
	static int32 GetSource(SubsidyID subsidy_id);

	/**
	 * Is the destination of the subsidy a town or an industry.
	 * @param subsidy_id The SubsidyID to check.
	 * @pre IsValidSubsidy(subsidy_id) && !IsAwarded(subsidy_id).
	 * @return True if the destination is a town, false if it is an industry.
	 */
	static bool DestinationIsTown(SubsidyID subsidy_id);

	/**
	 * Return the destination TownID/IndustryID/StationID the subsidy is for.
	 * 1) IsAwarded(subsidy_id) -> return the StationID the subsidy is awarded to.
	 * 2) !IsAwarded(subsidy_id) && SourceIsTown(subsidy_id) -> return the TownID.
	 * 3) !IsAwarded(subsidy_id) && !SourceIsTown(subsidy_id) -> return the IndustryID.
	 * @param subsidy_id the SubsidyID to check.
	 * @pre IsValidSubsidy(subsidy_id).
	 * @return One of TownID/IndustryID/StationID.
	 */
	static int32 GetDestination(SubsidyID subsidy_id);
};

#endif /* AI_SUBSIDY_HPP */