// Functions for handling event triggers
//
// Because most of these functions can be called by signal handler, it is important to make it well
// defined when these functions produce output or perform memory allocations, since such functions
// may not be safely called by signal handlers.
#ifndef FISH_EVENT_H
#define FISH_EVENT_H

#include <unistd.h>

#include <map>
#include <memory>
#include <vector>

#include "common.h"
#include "io.h"

/// The process id that is used to match any process id.
#define EVENT_ANY_PID 0

/// Enumeration of event types.
enum class event_type_t {
    /// Matches any event type (Not always any event, as the function name may limit the choice as
    /// well.
    any,
    /// An event triggered by a signal.
    signal,
    /// An event triggered by a variable update.
    variable,
    /// An event triggered by a job or process exit.
    exit,
    /// An event triggered by a job exit.
    job_exit,
    /// A generic event.
    generic,
};

/// Properties of an event.
struct event_description_t {
    /// The event type.
    event_type_t type;

    /// The type-specific parameter. The int types are one of the following:
    ///
    /// signal: Signal number for signal-type events.Use EVENT_ANY_SIGNAL to match any signal
    /// pid: Process id for process-type events. Use EVENT_ANY_PID to match any pid. (Negative
    /// values are used for PGIDs). job_id: Job id for EVENT_JOB_ID type events
    union {
        int signal;
        int job_id;
        pid_t pid;
    } param1{};

    /// The string types are one of the following:
    ///
    /// variable: Variable name for variable-type events.
    /// param: The parameter describing this generic event.
    wcstring str_param1{};

    explicit event_description_t(event_type_t t) : type(t) {}
    static event_description_t signal(int sig);
    static event_description_t variable(wcstring str);
    static event_description_t generic(wcstring str);
};

/// Represents a handler for an event.
struct event_handler_t {
    /// Properties of the event to match.
    event_description_t desc;

    /// Name of the function to invoke.
    wcstring function_name{};

    explicit event_handler_t(event_type_t t) : desc(t) {}
    event_handler_t(event_description_t d, wcstring name)
        : desc(d), function_name(std::move(name)) {}
};
using event_handler_list_t = std::vector<std::shared_ptr<event_handler_t>>;

/// Represents a event that is fired, or capable of being fired.
struct event_t {
    /// Properties of the event.
    event_description_t desc;

    /// Arguments to any handler.
    wcstring_list_t arguments{};

    event_t(event_type_t t) : desc(t) {}

    static event_t variable(wcstring name, wcstring_list_t args);
};

/// Add an event handler.
void event_add_handler(std::shared_ptr<event_handler_t> eh);

/// Remove all events for the given function name.
void event_remove_function_handlers(const wcstring &name);

/// Return all event handlers for the given function.
event_handler_list_t event_get_function_handlers(const wcstring &name);

/// Returns whether an event listener is registered for the given signal. This is safe to call from
/// a signal handler.
bool event_is_signal_observed(int signal);

/// Fire the specified event \p event.
void event_fire(const event_t &event);

/// Fire all delayed eents.
void event_fire_delayed();

/// Enqueue a signal event. Invoked from a signal handler.
void event_enqueue_signal(int signal);

/// Print all events. If type_filter is not none(), only output events with that type.
void event_print(io_streams_t &streams, maybe_t<event_type_t> type_filter);

/// Returns a string describing the specified event.
wcstring event_get_desc(const event_t &e);

/// Fire a generic event with the specified name.
void event_fire_generic(const wchar_t *name, const wcstring_list_t *args = NULL);

/// Return the event type for a given name, or none.
maybe_t<event_type_t> event_type_for_name(const wcstring &name);

#endif
