EventManager.ttslua

require('ge_tts.License')

local TableUtils = require('ge_tts.TableUtils')
local Logger = require('ge_tts.Logger')

---@type table<string, any>
local EVENT_DEFAULT_RETURN_VALUES = {
    filterObjectEnterContainer = true,
}

---@type table<string, function[]>
local eventHandlers = {}

local globalHandlers = --[[---@type {[string]: nil | function}]] _G

---@param event string
local function listen(event)
    local previousGlobalHandler = globalHandlers[event]

    ;(--[[---@type table]] _G)[event] = function(...)
        local handlers = TableUtils.copy(eventHandlers[event]) -- Copied in case we add/remove handlers during a handler callback

        ---@type std__Packed<any>
        local finalResult = --[[---@type std__Packed<any>]] {n = 0}

        for _, handler in ipairs(handlers) do
            local result = table.pack(handler(...))

            if result.n > 0 then
                finalResult = result
            end
        end

        if finalResult.n > 0 then
            return table.unpack(finalResult, 1, finalResult.n)
        else
            local defaultValue = EVENT_DEFAULT_RETURN_VALUES[event]

            if defaultValue ~= nil then
                return defaultValue
            end
        end
    end

    ---@type function[]
    local handlers = {}

    eventHandlers[event] = handlers

    Logger.log('EventManager now listening for ' .. event, Logger.VERBOSE)

    if previousGlobalHandler then
        table.insert(handlers, --[[---@not nil]] previousGlobalHandler)
        Logger.log('Pre-existing global ' .. event .. ' handler preserved as the first handler', Logger.VERBOSE)
    end

    return handlers
end

local SAVE_MANAGER_EVENTS = {'onSave', 'onLoad'}

---@class ge_tts__EventManager
local EventManager = {}

---@param event string @Event name
---@param handler function @Function that will be called when the event fires. Parameters vary depending on the event.
function EventManager.addHandler(event, handler)
    assert(not TableUtils.find(SAVE_MANAGER_EVENTS, event), 'EventManager cannot handle ' .. event .. '. Please use SaveManager instead.')

    local handlers = eventHandlers[event] or listen(event)

    if not TableUtils.find(handlers, handler) then
        table.insert(handlers, handler)
    end
end

---@param event string @Event name
---@param handler function @A previously registered handler that you wish to remove.
function EventManager.removeHandler(event, handler)
    assert(not TableUtils.find(SAVE_MANAGER_EVENTS, event), 'EventManager cannot handle ' .. event .. '. Please use SaveManager instead.')

    local handlers = eventHandlers[event]
    local handlerIndex = handlers and TableUtils.find(handlers, handler)

    if handlerIndex then
        table.remove(handlers, --[[---@not nil]] handlerIndex)
    end
end

---@param event string @Event name
---@vararg any
function EventManager.triggerEvent(event, ...)
    local handler = globalHandlers[event]

    if handler then
        (--[[---@not nil]] handler)(...)
    end
end

return EventManager