// Event listeners work similar to the JavaScript event dispatching system,
// except that the event object is a hash table.
//
// Javascript reference:
// https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Creating_and_triggering_events
//
// Example usage:
/*
// Create a handler function:
public function myHandler {
    // ... do something with getarg(0)
}

// Create a new event:
$@event = htnew();

// Listen for the event:
addEventListener($@event, "myHandler");

// Dispatch the event:
dispatchEvent($@event, "misc data");
*/


/**
 * getEventHt(<hash table expression>) => ht id
 *
 * Parses a hash table "event" expression and creates one when necessary.
 * The following are all valid:
 *
 * getEventHt(.@ht); // variable
 * getEventHt(72); // arbitrary integer (global namespace)
 * getEventHt("some event"); // arbitrary string (global namespace)
 *
 * NOTE: This is only called internally; you don't have to use this function
 *
 * @param 0 - a variable / string / integer
 * @return the hash table id
 */
function	script	getEventHt	{
    .@ht = ((getdatatype(getarg(0)) & (DATATYPE_VAR | DATATYPE_INT)) != 0) ? getarg(0) : 0;

    if (htexists(.@ht)) {
        // this is already a valid hash table
        return getarg(0);
    } else if ((getdatatype(getarg(0)) & DATATYPE_VAR) != 0) {
        // the hash table doesn't exist yet: create one and store it in the
        // provided variable

        if ((getdatatype(getarg(0)) & DATATYPE_STR) != 0) {
            consolemes(CONSOLEMES_ERROR, "getEventHt: variable must be an integer variable (cannot use %s)", data_to_string(getarg(0)));
            end;
        }

        if (getarg(0) > 0) {
            consolemes(CONSOLEMES_WARNING, "getEventHt: variable is already assigned (overwriting %s)", data_to_string(getarg(0)));
        }

        return set(getarg(0), htnew());
    } else {
        // global event listener namespace
        if ($@GLOBAL_EVTL_HT < 1) {
            $@GLOBAL_EVTL_HT = htnew();

            // the global scope is new: create a new one
            .@ht = htnew();
            htput($@GLOBAL_EVTL_HT, data_to_string(getarg(0)), "" + .@ht);
            return .@ht;
        } else if ((.@ht$ = htget($@GLOBAL_EVTL_HT, data_to_string(getarg(0)), "")) != "") {
            // found in the global scope
            return atoi(.@ht$);
        } else {
            // not found in the global scope: create new
            .@ht = htnew();
            htput($@GLOBAL_EVTL_HT, data_to_string(getarg(0)), "" + .@ht);
            return .@ht;
        }
    }
}

/**
 * addEventListener(<ht: event>, "<handler: public local function>") => void
 *
 * Register a public local function in the current NPC as an event handler for
 * the given hash table. Can also register for another NPC using the syntax
 * `npcName::function`
 *
 * NOTE: only one handler may be assigned per NPC per Event
 *
 * @param 0 - the event to listen to (string, variable, or hash table)
 * @param 1 - the event handler (must be a public local function)
 */
function	script	addEventListener	{
    .@ht = getEventHt(getarg(0));
    .@pos = strpos(getarg(1), "::");

    if (.@pos > -1) {
        .@id = getnpcid(substr(getarg(1), 0, .@pos - 1));
        .@function$ = substr(getarg(1), .@pos + 2, getstrlen(getarg(1)) - 1);
    } else {
        .@id = getnpcid();
        .@function$ = getarg(1);
    }

    if (.@id == 0) {
        consolemes(CONSOLEMES_WARNING, "addEventListener: the target NPC doesn't exist");
        return;
    }

    // TODO: check that the target function exists
    return htput(.@ht, "" + .@id, .@function$);
}

/**
 * dispatchEvent(<ht: event>{, ...<arg>}) => bool
 *
 * Calls every event handler for the given hash table and passes the given
 * arguments (if any)
 *
 * @param 0 - the event to dispatch (string, variable, or hash table)
 * @return true when handlers were called, else false
 */
function	script	dispatchEvent	{
    .@ht = getEventHt(getarg(0));

    if (htsize(.@ht) < 1) {
        // no handler to call
        return false;
    }

    .@it = htiterator(.@ht);

    freeloop(true);
    for (.@npc$ = htinextkey(.@it); hticheck(.@it); .@npc$ = htinextkey(.@it)) {
        if (.@npc$ == "") {
            continue;
        }

        .@func$ = htget(.@ht, .@npc$, "");

        // this is ugly but we don't have rest parameters (...args) to apply args to function calls
        switch (getargcount()) {
        case 1:
            callfunctionofnpc(atoi(.@npc$), .@func$);
            break;
        case 2:
            callfunctionofnpc(atoi(.@npc$), .@func$, getarg(1));
            break;
        case 3:
            callfunctionofnpc(atoi(.@npc$), .@func$, getarg(1), getarg(2));
            break;
        case 4:
            callfunctionofnpc(atoi(.@npc$), .@func$, getarg(1), getarg(2), getarg(3));
            break;
        case 5:
            callfunctionofnpc(atoi(.@npc$), .@func$, getarg(1), getarg(2), getarg(3), getarg(4));
            break;
        default:
            consolemes(CONSOLEMES_WARNING, "dispatchEvent: truncating to 5 arguments (%d given)", getargcount() - 1);
        case 6:
            callfunctionofnpc(atoi(.@npc$), .@func$, getarg(1), getarg(2), getarg(3), getarg(4), getarg(5));
            break;
        }
    }
    freeloop(false);

    htidelete(.@it);
    return true;
}