#include "catch.hpp"

#include <map>
#include <random>
#include <string>
#include <vector>

#include <QPoint>

#include "BeltSystem.h"
#include "Building.h"
#include "BuildingSystem.h"
#include "BuildingType.h"
#include "ConfigLoader.h"
#include "Item.h"
#include "ItemType.h"
#include "Port.h"
#include "Rotation.h"
#include "Tick.h"

// ---------------------------------------------------------------------------
// Fixture helpers
// ---------------------------------------------------------------------------

static GameConfig loadConfig()
{
    return ConfigLoader::loadFromDirectory(CONFIG_DIR);
}

static Item makeItem(const std::string& id)
{
    Item item;
    item.type.id = id;
    return item;
}

static Port eastPort(QPoint tile)
{
    Port p;
    p.tile      = tile;
    p.direction = Rotation::East;
    return p;
}

static Port westPort(QPoint tile)
{
    Port p;
    p.tile      = tile;
    p.direction = Rotation::West;
    return p;
}

// Run N full sim ticks: construction, belt-pull, production, belt-push, belt tick.
static void runTicks(BuildingSystem& bs, BeltSystem& belts, int n, Tick& tick)
{
    for (int i = 0; i < n; ++i)
    {
        bs.tickConstruction(tick);
        bs.tickBeltPull();
        bs.tickProduction(tick);
        bs.tickBeltPush();
        belts.tick();
        ++tick;
    }
}

// ---------------------------------------------------------------------------
// Placement
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: place miner occupies expected body tiles", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);
    REQUIRE(id != kInvalidBuildingId);

    // Miner mask ["AA","A>"] with East rotation → body at (0,0),(1,0),(0,1).
    REQUIRE(bs.isTileOccupied(QPoint(0, 0)));
    REQUIRE(bs.isTileOccupied(QPoint(1, 0)));
    REQUIRE(bs.isTileOccupied(QPoint(0, 1)));
    // (1,1) is the output-port tile, NOT a body cell.
    REQUIRE_FALSE(bs.isTileOccupied(QPoint(1, 1)));
}

TEST_CASE("BuildingSystem: placing a belt registers it with BeltSystem after construction",
          "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    bs.place(BuildingType::Belt, QPoint(5, 5), Rotation::East, 0);

    // Belt is queued — not yet in BeltSystem.
    REQUIRE_FALSE(belts.tryPutItem(QPoint(5, 5), makeItem("iron_ore")));

    // Complete construction (1 s).
    Tick tick = 0;
    runTicks(bs, belts, static_cast<int>(secondsToTicks(1.0)) + 1, tick);

    REQUIRE(belts.tryPutItem(QPoint(5, 5), makeItem("iron_ore")));
    REQUIRE(bs.allBuildings().size() == 1);
    REQUIRE(bs.allBuildings()[0].type == BuildingType::Belt);
    REQUIRE(bs.allBuildings()[0].anchor == QPoint(5, 5));
}

TEST_CASE("BuildingSystem: placed building enters construction queue", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);

    REQUIRE(bs.allSites().size() == 1);
    REQUIRE(bs.allBuildings().empty());
    REQUIRE(bs.findSite(id) != nullptr);
}

TEST_CASE("BuildingSystem: demolish frees tiles and returns refund", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);

	// Miner construction_time_seconds = 10.  completesAt = secondsToTicks(10) = 300.
	// We need to process tick 300 itself, so run 301 ticks (ticks 0..300).
	Tick tick = 0;
	runTicks(bs, belts, static_cast<int>(secondsToTicks(10.0)) + 1, tick);

    const int refund = bs.demolish(id);

    // Miner cost = 15, refund = floor(15 * 75 / 100) = 11.
    REQUIRE(refund == 15 * cfg.world.refundPercentage / 100);
    REQUIRE_FALSE(bs.isTileOccupied(QPoint(0, 0)));
    REQUIRE(bs.allSites().empty());
}

// ---------------------------------------------------------------------------
// Construction queue
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: first queued building starts construction immediately",
          "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);
    REQUIRE(bs.allSites().front().completesAt > 0);
}

TEST_CASE("BuildingSystem: second queued building waits (completesAt == 0)", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);
    bs.place(BuildingType::Miner, QPoint(5, 5), Rotation::East, 0);

    REQUIRE(bs.allSites().size() == 2);
    REQUIRE(bs.allSites()[0].completesAt > 0);
    REQUIRE(bs.allSites()[1].completesAt == 0);
}

TEST_CASE("BuildingSystem: construction completes after configured duration", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);

    // Miner construction_time_seconds = 10.  completesAt = secondsToTicks(10) = 300.
    // We need to process tick 300 itself, so run 301 ticks (ticks 0..300).
    Tick tick = 0;
    runTicks(bs, belts, static_cast<int>(secondsToTicks(10.0)) + 1, tick);

    REQUIRE(bs.allSites().empty());
    REQUIRE(bs.findBuilding(id) != nullptr);
}

TEST_CASE("BuildingSystem: second building starts after first completes", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);
    const BuildingId id2 = bs.place(BuildingType::Miner, QPoint(5, 5), Rotation::East, 0);

    // Process through tick 300 to complete first miner's construction.
    Tick tick = 0;
    runTicks(bs, belts, static_cast<int>(secondsToTicks(10.0)) + 1, tick);

    REQUIRE(bs.allSites().size() == 1);
    REQUIRE(bs.allSites().front().id == id2);
    REQUIRE(bs.allSites().front().completesAt > 0);
}

// ---------------------------------------------------------------------------
// Miner production cycle
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: miner produces iron_ore after recipe duration", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);
    bs.setRecipe(id, "mine_iron_ore");

    Tick tick = 0;
    // Construction completes on tick 300; production cycle starts tick 300,
    // completes on tick 330.  Process through tick 330: 331 ticks total.
    runTicks(bs, belts,
             static_cast<int>(secondsToTicks(10.0)) + static_cast<int>(secondsToTicks(1.0)) + 1,
             tick);

    const Building* b = bs.findBuilding(id);
    REQUIRE(b != nullptr);
    REQUIRE_FALSE(b->outputBuffer.items.empty());
    REQUIRE(b->outputBuffer.items.front().type.id == "iron_ore");
}

TEST_CASE("BuildingSystem: miner output buffer stalls when full", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);
    bs.setRecipe(id, "mine_iron_ore");

    Tick tick = 0;
    // Construction (10s) then cycle 1 starts at tick 300 (completesAt=330).
    // Cycle 1 completes at tick 330: deposit item, continue (no same-tick restart).
    // Cycle 2 starts at tick 331 (completesAt=361).
    // Cycle 2 completes at tick 361: deposit item → buffer=2, cycle 3 stalls.
    // Need to process through tick 361: 362 ticks total.
    runTicks(bs, belts,
             static_cast<int>(secondsToTicks(10.0))
             + 2 * static_cast<int>(secondsToTicks(1.0)) + 2,
             tick);

    const Building* b = bs.findBuilding(id);
    REQUIRE(b != nullptr);
    REQUIRE(static_cast<int>(b->outputBuffer.items.size()) == 2);
    REQUIRE_FALSE(b->production.has_value());
}

// ---------------------------------------------------------------------------
// REQ-UI-DEBUG-OVERLAY production counts
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: productionBuildingCount excludes construction sites", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId minerId   = bs.place(BuildingType::Miner,   QPoint(0, 0),  Rotation::East, 0);
    const BuildingId smelterId = bs.place(BuildingType::Smelter, QPoint(10, 0), Rotation::East, 0);
    (void)smelterId;

    Tick tick = 0;
    // Both still under construction.
    REQUIRE(bs.productionBuildingCount() == 0);

    // The queue builds one at a time: miner (10s) completes at tick 300, then
    // the smelter (15s) starts and completes at tick 300 + 450 = 750.
    runTicks(bs, belts, static_cast<int>(secondsToTicks(10.0)) + 1, tick);
    REQUIRE(bs.productionBuildingCount() == 1);

    runTicks(bs, belts, static_cast<int>(secondsToTicks(15.0)), tick);
    REQUIRE(bs.productionBuildingCount() == 2);

    // Neither has a recipe selected, so neither has an active cycle.
    REQUIRE(bs.activeProductionBuildingCount() == 0);

    bs.setRecipe(minerId, "mine_iron_ore");
    runTicks(bs, belts, 1, tick);
    REQUIRE(bs.activeProductionBuildingCount() == 1);
}

TEST_CASE("BuildingSystem: activeProductionBuildingCount tracks production cycle state",
          "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);
    bs.setRecipe(id, "mine_iron_ore");

    Tick tick = 0;
    // Not yet operational while under construction.
    REQUIRE(bs.activeProductionBuildingCount() == 0);

    // Construction completes at tick 300; cycle 1 starts the same tick (completesAt=330).
    runTicks(bs, belts, static_cast<int>(secondsToTicks(10.0)) + 1, tick);
    REQUIRE(bs.activeProductionBuildingCount() == 1);

    // Run cycles 1 and 2 to completion (1s each); cycle 3 stalls once the
    // output buffer (capacity 2) is full (REQ-MAT-OUTPUT-BUFFER).
    runTicks(bs, belts, 2 * static_cast<int>(secondsToTicks(1.0)) + 1, tick);

    const Building* b = bs.findBuilding(id);
    REQUIRE(b != nullptr);
    REQUIRE(static_cast<int>(b->outputBuffer.items.size()) == 2);
    REQUIRE_FALSE(b->production.has_value());
    REQUIRE(bs.activeProductionBuildingCount() == 0);
}

// ---------------------------------------------------------------------------
// Belt pull → input buffer
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: smelter input buffer fills from adjacent west-flowing belt",
          "[building]")
{
    const GameConfig cfg = loadConfig();
    // Fast belt so items are immediately available for peek/take.
    BeltSystem belts(static_cast<double>(kTickRateHz));
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    // Smelter mask ["AA ","AA>"] → body (0,0),(1,0),(0,1),(1,1).
    // Output port (2,1) East.  Input port example: (2,0) West.
    const BuildingId sid = bs.place(BuildingType::Smelter, QPoint(0, 0), Rotation::East, 0);
    bs.setRecipe(sid, "iron_ingot");

    // Complete construction (15s → tick 450+1 = 451 ticks).
    Tick tick = 0;
    runTicks(bs, belts, static_cast<int>(secondsToTicks(15.0)) + 1, tick);

    // Place west-flowing belt at (2,0): belt flows West, delivers to smelter.
    belts.placeBelt(QPoint(2, 0), Rotation::West);
    belts.tryPutItem(QPoint(2, 0), makeItem("iron_ore"));
    belts.tick();

    bs.tickBeltPull();

    const Building* b = bs.findBuilding(sid);
    REQUIRE(b != nullptr);
    const std::map<ItemType, int>::const_iterator it =
        b->inputBuffer.counts.find(ItemType{"iron_ore"});
    REQUIRE(it != b->inputBuffer.counts.end());
    REQUIRE(it->second >= 1);
}

// ---------------------------------------------------------------------------
// Belt push → belt tile
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: miner output buffer drains onto adjacent belt", "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(static_cast<double>(kTickRateHz));
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);
    bs.setRecipe(id, "mine_iron_ore");

    // Belt at the miner's output port tile (1,1) flowing East.
    belts.placeBelt(QPoint(1, 1), Rotation::East);

    Tick tick = 0;
    // Construction (10s) + 1 production cycle (1s) + 1 extra tick.
    runTicks(bs, belts,
             static_cast<int>(secondsToTicks(10.0)) + static_cast<int>(secondsToTicks(1.0)) + 1,
             tick);

    // Item should have been pushed onto the belt this tick or a subsequent one.
    // Run one more tick to ensure tickBeltPush fires after the deposit tick.
    runTicks(bs, belts, 1, tick);

    const std::optional<Item> item = belts.tryTakeItem(eastPort(QPoint(1, 1)));
    REQUIRE(item.has_value());
    REQUIRE(item->type.id == "iron_ore");
}

// ---------------------------------------------------------------------------
// setRecipe clears buffers
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: setRecipe clears output buffer and active production",
          "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(static_cast<double>(kTickRateHz));
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0);
    bs.setRecipe(id, "mine_iron_ore");

    Tick tick = 0;
    // Run until first item is in output buffer.
    runTicks(bs, belts,
             static_cast<int>(secondsToTicks(10.0)) + static_cast<int>(secondsToTicks(1.0)) + 1,
             tick);

    {
        const Building* b = bs.findBuilding(id);
        REQUIRE(b != nullptr);
        REQUIRE_FALSE(b->outputBuffer.items.empty());
    }

    bs.setRecipe(id, "mine_copper_ore");

    const Building* b = bs.findBuilding(id);
    REQUIRE(b->outputBuffer.items.empty());
    REQUIRE_FALSE(b->production.has_value());
}

// ---------------------------------------------------------------------------
// Reprocessing plant — output buffer capacity (REQ-MAT-OUTPUT-BUFFER-REPROCESSING)
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: reprocessing plant output buffer capacity equals max output per roll",
          "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::ReprocessingPlant,
                                  QPoint(0, 0), Rotation::East, 0);
    bs.setRecipe(id, "reprocessing_cycle");

    // Complete construction (25s).
    Tick tick = 0;
    runTicks(bs, belts, static_cast<int>(secondsToTicks(25.0)) + 1, tick);

    const Building* b = bs.findBuilding(id);
    REQUIRE(b != nullptr);
    // reprocessing_cycle outputs: 2 iron_ingot (60%), 1 circuit_board (30%),
    // 1 advanced_alloy (10%).  Max per roll = 2.  Capacity = 2 (1× max).
    REQUIRE(b->outputBuffer.capacity == 2);
}

TEST_CASE("BuildingSystem: reprocessing plant produces one cycle output then stalls",
          "[building]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(static_cast<double>(kTickRateHz));
    int stock = 0;
    // Seed chosen so first roll produces 2-item output (iron_ingot), filling buffer.
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::ReprocessingPlant,
                                  QPoint(0, 0), Rotation::East, 0);
    bs.setRecipe(id, "reprocessing_cycle");

    // Complete construction (25s).
    Tick tick = 0;
    runTicks(bs, belts, static_cast<int>(secondsToTicks(25.0)) + 1, tick);

    // Feed 5 scrap into the building via a belt at an input port.
    // Reprocessing plant body (East rotation) = 3×3 at (0,0).
    // Valid input port: tile (-1,0) flowing East.
    belts.placeBelt(QPoint(-1, 0), Rotation::East);
    for (int i = 0; i < 5; ++i)
    {
        belts.tryPutItem(QPoint(-1, 0), makeItem("scrap"));
        belts.tick();
        bs.tickBeltPull();
    }

    // Verify scrap is in input buffer.
    {
        const Building* b = bs.findBuilding(id);
        REQUIRE(b != nullptr);
        const std::map<ItemType, int>::const_iterator it =
            b->inputBuffer.counts.find(ItemType{"scrap"});
        REQUIRE(it != b->inputBuffer.counts.end());
        REQUIRE(it->second == 5);
    }

    // Run production cycle (3s = 90 ticks + 1 for the completion tick).
    runTicks(bs, belts, static_cast<int>(secondsToTicks(3.0)) + 1, tick);

    const Building* b = bs.findBuilding(id);
    REQUIRE(b != nullptr);
    // Cycle should have completed and output deposited.
    REQUIRE_FALSE(b->outputBuffer.items.empty());
    // No new production: inputs were consumed and not replenished.
    REQUIRE_FALSE(b->production.has_value());
}

// ---------------------------------------------------------------------------
// findRotateInPlaceTarget
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: findRotateInPlaceTarget returns nullopt when tile is empty",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    REQUIRE_FALSE(
        bs.findRotateInPlaceTarget(BuildingType::Belt, QPoint(0, 0), Rotation::East).has_value());
}

TEST_CASE("BuildingSystem: findRotateInPlaceTarget returns the site id for a queued belt (same type, different rotation)",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Belt, QPoint(0, 0), Rotation::East, 0);

    const std::optional<BuildingId> result =
        bs.findRotateInPlaceTarget(BuildingType::Belt, QPoint(0, 0), Rotation::North);
    REQUIRE(result.has_value());
    REQUIRE(*result == id);
}

TEST_CASE("BuildingSystem: findRotateInPlaceTarget returns the building id for a completed operational belt",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Belt, QPoint(0, 0), Rotation::East, 0);

    Tick tick = 0;
    runTicks(bs, belts, static_cast<int>(secondsToTicks(1.0)) + 1, tick);
    REQUIRE(bs.allSites().empty());

    const std::optional<BuildingId> result =
        bs.findRotateInPlaceTarget(BuildingType::Belt, QPoint(0, 0), Rotation::South);
    REQUIRE(result.has_value());
    REQUIRE(*result == id);
}

TEST_CASE("BuildingSystem: findRotateInPlaceTarget returns nullopt when building type differs",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    bs.place(BuildingType::Belt, QPoint(0, 0), Rotation::East, 0);

    // Querying with Splitter at the same tile — type mismatch → nullopt.
    REQUIRE_FALSE(
        bs.findRotateInPlaceTarget(BuildingType::Splitter, QPoint(0, 0), Rotation::East).has_value());
}

TEST_CASE("BuildingSystem: findRotateInPlaceTarget returns nullopt when footprints only partially overlap",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    // Smelter at (0,0) occupies body tiles (0,0),(1,0),(0,1),(1,1).
    bs.place(BuildingType::Smelter, QPoint(0, 0), Rotation::East, 0);

    // Ghost anchored at (1,0) would cover (1,0),(2,0),(1,1),(2,1):
    // only (1,0) and (1,1) are occupied — not a full coincidence.
    REQUIRE_FALSE(
        bs.findRotateInPlaceTarget(BuildingType::Smelter, QPoint(1, 0), Rotation::East).has_value());
}

TEST_CASE("BuildingSystem: findRotateInPlaceTarget works for a symmetric multi-tile building with rotated ghost",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    // Smelter is a fully filled 2×2 footprint — rotating the ghost produces the
    // same four body tiles, so findRotateInPlaceTarget must still return the id.
    const BuildingId id = bs.place(BuildingType::Smelter, QPoint(0, 0), Rotation::East, 0);

    const std::optional<BuildingId> result =
        bs.findRotateInPlaceTarget(BuildingType::Smelter, QPoint(0, 0), Rotation::North);
    REQUIRE(result.has_value());
    REQUIRE(*result == id);
}

// ---------------------------------------------------------------------------
// rotateInPlace
// ---------------------------------------------------------------------------

TEST_CASE("BuildingSystem: rotateInPlace updates the rotation field of a construction site",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Belt, QPoint(0, 0), Rotation::East, 0);
    REQUIRE(bs.findSite(id)->rotation == Rotation::East);

    bs.rotateInPlace(id, Rotation::North);

    REQUIRE(bs.findSite(id)->rotation == Rotation::North);
}

TEST_CASE("BuildingSystem: rotateInPlace preserves the construction progress of a queued site",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Belt, QPoint(0, 0), Rotation::East, 0);
    const Tick completesAt = bs.findSite(id)->completesAt;
    REQUIRE(completesAt > 0);

    bs.rotateInPlace(id, Rotation::South);

    REQUIRE(bs.findSite(id)->completesAt == completesAt);
}

TEST_CASE("BuildingSystem: rotateInPlace updates rotation and output port direction on an operational building",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Belt, QPoint(0, 0), Rotation::East, 0);

    Tick tick = 0;
    runTicks(bs, belts, static_cast<int>(secondsToTicks(1.0)) + 1, tick);
    REQUIRE(bs.findBuilding(id) != nullptr);

    const Building& before = *bs.findBuilding(id);
    REQUIRE(before.outputPorts[0].direction == Rotation::East);

    bs.rotateInPlace(id, Rotation::North);

    const Building& after = *bs.findBuilding(id);
    REQUIRE(after.rotation == Rotation::North);
    REQUIRE(after.outputPorts[0].direction == Rotation::North);
}

TEST_CASE("BuildingSystem: rotateInPlace re-registers a belt tile with BeltSystem so it still accepts items",
          "[building][rotate-in-place]")
{
    const GameConfig cfg = loadConfig();
    BeltSystem belts(cfg.world.beltSpeed_tps);
    int stock = 0;
    std::mt19937 rng(0);
    BuildingId nextBuildingId = 1;
    BuildingSystem bs(cfg, belts,
                      [&nextBuildingId]() { return nextBuildingId++; },
                      [&stock](int n) { stock += n; },
                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                      [](const std::string&) -> bool { return true; },
                      rng);

    const BuildingId id = bs.place(BuildingType::Belt, QPoint(0, 0), Rotation::East, 0);

    Tick tick = 0;
    runTicks(bs, belts, static_cast<int>(secondsToTicks(1.0)) + 1, tick);

    bs.rotateInPlace(id, Rotation::North);

    // Belt tile must still be registered after rotation — items can be placed on it.
    REQUIRE(belts.tryPutItem(QPoint(0, 0), makeItem("iron_ore")));
}