// See the file "COPYING" in the main distribution directory for copyright.

// Each event raised/handled by Zeek is registered in the EventRegistry.

#pragma once

#include <map>
#include <memory>
#include <string>
#include <string_view>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include "zeek/IntrusivePtr.h"
#include "zeek/ZeekArgs.h"

namespace zeek {

// The different kinds of event groups that exist.
enum class EventGroupKind : uint8_t {
    Attribute,
    Module,
};

class EnumVal;
class EventGroup;
class EventHandler;
class EventHandlerPtr;
class RE_Matcher;
class RecordVal;
class Type;

using EnumValPtr = IntrusivePtr<EnumVal>;
using EventGroupPtr = std::shared_ptr<EventGroup>;
using RecordValPtr = IntrusivePtr<RecordVal>;
using TypePtr = IntrusivePtr<Type>;

namespace detail {
class ScriptFunc;
using ScriptFuncPtr = zeek::IntrusivePtr<ScriptFunc>;

/**
 * Well-known event metadata identifiers.
 */
enum class MetadataType : uint8_t {
    NetworkTimestamp = 1,
};

} // namespace detail

/**
 * Descriptor for event metadata.
 *
 * Event metadata is registered via @ref EventRegistry::RegisterMetadata. The descriptor
 * holds the metadata identifier and registered type. For the identifier,
 * *id* is the unsigned int representation, while *id_val* holds the
 * script-layer zeek::EnumVal.
 */
class EventMetadataDescriptor {
public:
    EventMetadataDescriptor(zeek_uint_t id, EnumValPtr id_val, TypePtr type)
        : id(id), id_val(std::move(id_val)), type(std::move(type)) {}

    zeek_uint_t Id() const { return id; }
    const EnumValPtr& IdVal() const { return id_val; }
    const TypePtr& Type() const { return type; }

private:
    zeek_uint_t id;
    EnumValPtr id_val;
    TypePtr type;
};

// The registry keeps track of all events that we provide or handle.
class EventRegistry final {
public:
    EventRegistry();
    ~EventRegistry() noexcept;

    /**
     * Performs a lookup for an existing event handler and returns it
     * if one exists, or else creates one, registers it, and returns it.
     * @param name  The name of the event handler to lookup/register.
     * @param name  Whether the registration is coming from a script element.
     * @return  The event handler.
     */
    EventHandlerPtr Register(std::string_view name, bool is_from_script = false);

    void Register(EventHandlerPtr handler, bool is_from_script = false);

    // Return nil if unknown.
    EventHandler* Lookup(std::string_view name);

    // True if the given event handler (1) exists, and (2) was registered
    // in a non-script context (even if perhaps also registered in a script
    // context).
    bool NotOnlyRegisteredFromScript(std::string_view name);

    // Returns a list of all local handlers that match the given pattern.
    // Passes ownership of list.
    using string_list = std::vector<std::string>;
    string_list Match(RE_Matcher* pattern);

    // Marks a handler as handling errors. Error handler will not be called
    // recursively to avoid infinite loops in case they trigger an error
    // themselves.
    void SetErrorHandler(std::string_view name);

    string_list AllHandlers();

    void PrintDebug();

    /**
     * Marks all event handlers as active.
     *
     * By default, zeek does not generate (raise) events that have not handled by
     * any scripts. This means that these events will be invisible to a lot of other
     * event handlers - and will not raise :zeek:id:`new_event`. Calling this
     * function will cause all event handlers to be raised. This is likely only
     * useful for debugging and fuzzing, and likely causes reduced performance.
     */
    void ActivateAllHandlers();

    /**
     * Lookup or register a new event group.
     *
     * @return Pointer to the group.
     */
    EventGroupPtr RegisterGroup(EventGroupKind kind, std::string_view name);

    /**
     * Lookup an event group.
     *
     * @return Pointer to the group or nil if the group does not exist.
     */
    EventGroupPtr LookupGroup(EventGroupKind kind, std::string_view name);

    /**
     * Register a script-layer metadata identifier *id* with type *type*.
     *
     * @param id The script-level ``EventMetadata::ID`` enum value.
     * @param type The type to expect for the given metadata identifier.
     */
    bool RegisterMetadata(EnumValPtr id, TypePtr type);

    /**
     * Lookup the MetadataDescriptor for metadata identifier *id*
     *
     * @param id The metadata identifier as unsigned int.
     * @return A pointer to a MetadataDescriptor or nullptr.
     */
    const EventMetadataDescriptor* LookupMetadata(zeek_uint_t id) const;


private:
    std::map<std::string, std::unique_ptr<EventHandler>, std::less<>> handlers;
    // Tracks whether a given event handler was registered in a
    // non-script context.
    std::unordered_set<std::string> not_only_from_script;

    // Map event groups identified by kind and name to their instances.
    std::map<std::pair<EventGroupKind, std::string>, std::shared_ptr<EventGroup>, std::less<>> event_groups;

    // Map for event metadata identifier to their descriptors types.
    std::unordered_map<zeek_uint_t, EventMetadataDescriptor> event_metadata_types;
};

/**
 * Event group.
 *
 * Event and hook handlers (Func::Body instances) can be part of event groups.
 *
 * By default, all groups are enabled. An event or hook handler that is part of
 * any group that is disabled will be disabled and its execution prevented.
 *
 * Different kinds of event groups exist. Currently, attribute and module
 * event groups are implemented. The first relates to event handler tagged
 * with the &group attribute. The second is based on grouping event and hook
 * handlers by the module in which and these are implemented.
 *
 * Different kinds of are separate: Disabling the "HTTP" module event group does
 * not disable event handlers tagged with &group="HTTP", or vice versa.
 *
 * As an implementation detail: Event groups hold pointers to ScriptFunc
 * instances. Enabling or disabling individual groups iterates through all
 * bodies of the tracked ScriptFuncs and updates them to reflect the current
 * group state.
 */
class EventGroup final {
public:
    EventGroup(EventGroupKind kind, std::string_view name);
    ~EventGroup() noexcept = default;
    EventGroup(const EventGroup& g) = delete;
    EventGroup& operator=(const EventGroup&) = delete;

    /**
     * Enable this event group and update all event handlers associated with it.
     */
    void Enable();

    /**
     * Disable this event group and update all event handlers associated with it.
     */
    void Disable();

    /**
     * @return True if this group is disabled else false.
     */
    bool IsDisabled() { return ! enabled; }

    /**
     * Add a function to this group that may contain matching bodies.
     *
     * @param f Pointer to the function to track.
     */
    void AddFunc(detail::ScriptFuncPtr f);

private:
    void UpdateFuncBodies();

    EventGroupKind kind;
    bool enabled = true;
    std::string name;
    std::unordered_set<detail::ScriptFuncPtr> funcs;
};

extern EventRegistry* event_registry;

} // namespace zeek