#pragma once

#include <vector>

#include <QPoint>
#include <QPointF>

#include "Item.h"
#include "Rotation.h"

// A single item on a belt-like lane: an item plus its fractional progress along
// the lane's travel direction. Shared by BeltSystem's belt/tunnel tiles and by a
// building's virtual output belt (REQ-MAT-OUTPUT-EMERGE) so the packing and
// geometry live in exactly one place.
struct BeltItemSlot
{
    Item   item;
    double progress;  // [0.0, 1.0]: 0 = just entered, 1 = at output edge
};

// Advances every slot in `slots` by `progressPerTick`, applying the standard belt
// packing: the front (index 0) carries the highest progress; each following slot
// stays at least 0.25 behind the slot ahead and is capped at 1.0 - i * 0.25.
// `slots` must be ordered front (highest progress) first. This is the per-tile
// advance shared by belts, tunnel entries, and tunnel exits.
void advanceBeltSlots(std::vector<BeltItemSlot>& slots, double progressPerTick);

// World-space centre (in tile units) of a slot at `progress` on a lane occupying
// `tile` and flowing in `dir`. Progress 0 = entry edge, 1 = output edge.
QPointF beltSlotWorldPos(QPoint tile, Rotation dir, double progress);