// Called when a mob tries to use the item as a tool.
// Handles most checks.
/obj/item/proc/use_tool(atom/target, mob/living/user, delay, amount=0, volume=0, datum/callback/extra_checks)
	// No delay means there is no start message, and no reason to call tool_start_check before use_tool.
	// Run the start check here so we wouldn't have to call it manually.
	target.add_fingerprint(user)
	if(!tool_start_check(target, user, amount) && !delay)
		return
	delay *= toolspeed

	// Play tool sound at the beginning of tool usage.
	play_tool_sound(target, volume)

	if(delay)
		// Create a callback with checks that would be called every tick by do_after.
		var/datum/callback/tool_check = CALLBACK(src, PROC_REF(tool_check_callback), user, target, amount, extra_checks)

		if(ismob(target))
			if(!do_mob(user, target, delay, extra_checks = list(tool_check)))
				return

		else
			if(!do_after(user, delay, target=target, extra_checks = list(tool_check)))
				return
	else
		// Invoke the extra checks once, just in case.
		if(extra_checks && !extra_checks.Invoke())
			return

	// Use tool's fuel, stack sheets or charges if amount is set.
	if(amount && !use(amount))
		return

	// Play tool sound at the end of tool usage,
	// but only if the delay between the beginning and the end is not too small
	if(delay >= MIN_TOOL_SOUND_DELAY)
		play_tool_sound(target, volume)
	return TRUE

// Called before use_tool if there is a delay, or by use_tool if there isn't.
// Only ever used by welding tools and stacks, so it's not added on any other use_tool checks.
/obj/item/proc/tool_start_check(atom/target, mob/living/user, amount=0)
	return tool_use_check(user, amount)

// A check called by tool_start_check once, and by use_tool on every tick of delay.
/obj/item/proc/tool_use_check(mob/living/user, amount, silent = FALSE)
	return !amount

/obj/item/proc/play_tool_sound(atom/target, volume = tool_volume)
	if(target && usesound && volume)
		var/played_sound = usesound

		if(islist(usesound))
			played_sound = pick(usesound)

		playsound(target, played_sound, volume, 1)

// Used in a callback that is passed by use_tool into do_after call. Do not override, do not call manually.
/obj/item/proc/tool_check_callback(mob/living/user, atom/target, amount, datum/callback/extra_checks)
	if(!tool_use_check(user, amount))
		return TRUE
	if(extra_checks && !extra_checks.Invoke())
		return TRUE
	return FALSE