// Standalone tests for the FX reclaimer's drain — no REAPER, no test framework. The
// loop is templated on its host precisely so the four properties that make it safe to
// run in the background are assertable here: the debounce, the per-tick budget's
// yield-and-resume, the queue being a cache of intent that a model change discards, and
// the user's own offline plugins surviving an online.

#include "../src/shell/view/fx_reclaim.h"

#include <cstdio>
#include <map>
#include <set>
#include <string>
#include <vector>

using namespace reasampler;
using namespace reasampler::view;

static int g_fail = 0;
#define CHECK(cond) do { if(!(cond)) { \
    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)

namespace {

// -- a fake project ------------------------------------------------------------

// One live FX: its identity (empty when REAPER reports none) and whether it is offline.
struct FakeFx {
    std::string guid;
    bool        offline = false;
};

// Stands in for the REAPER half of drainTick's Host contract. The clock advances only
// on a REAL write, mirroring the live host: a compare-before-write that finds the FX
// already where it wants it costs a read, not a plugin load.
struct FakeHost {
    std::map<std::string, std::vector<FakeFx>> chains;
    std::set<std::string>                      released;
    std::vector<std::string>                   writeLog;
    double clock      = 0.0;
    double stepCostMs = 50.0;

    double nowMs() const { return clock; }

    bool liveChain(const std::string& guid, std::vector<std::string>& out) {
        auto it = chains.find(guid);
        if (it == chains.end()) return false;
        out.clear();
        for (const FakeFx& fx : it->second) out.push_back(fx.guid);
        return true;
    }

    bool writeOffline(const std::string& guid, int fxIndex, bool offline) {
        auto it = chains.find(guid);
        if (it == chains.end()) return false;
        if (fxIndex < 0 || fxIndex >= static_cast<int>(it->second.size())) return false;
        if (it->second[static_cast<std::size_t>(fxIndex)].offline == offline) return false;

        it->second[static_cast<std::size_t>(fxIndex)].offline = offline;
        clock += stepCostMs;
        writeLog.push_back(guid + ":" + std::to_string(fxIndex) + (offline ? "=off" : "=on"));
        return true;
    }

    void releaseFx(const std::string& guid) { released.insert(guid); }

    bool offlineAt(const std::string& guid, std::size_t slot) const {
        auto it = chains.find(guid);
        return it != chains.end() && slot < it->second.size() && it->second[slot].offline;
    }
};

// -- model helpers -------------------------------------------------------------

TrackSnapshot recordWithFx(std::vector<FxOfflineState> fx) {
    TrackSnapshot snap;
    snap.showInTcp = 1; snap.showInMixer = 1; snap.mainSend = 1; snap.fxEnable = 1;
    snap.fxOffline = std::move(fx);
    return snap;
}

// What the shell does on every invalidation: throw the queue away and recompute it.
std::vector<ReclaimItem> derive(const ViewModeModel& vm, const std::set<std::string>& live) {
    return makeQueue(desiredFxState(vm, vm.activeModeId(), live));
}

std::vector<FakeFx> onlineChain(const std::vector<std::string>& guids) {
    std::vector<FakeFx> chain;
    for (const std::string& g : guids) chain.push_back(FakeFx{g, false});
    return chain;
}

std::vector<FakeFx> offlineChain(const std::vector<std::string>& guids) {
    std::vector<FakeFx> chain;
    for (const std::string& g : guids) chain.push_back(FakeFx{g, true});
    return chain;
}

// A Design leaf the tool has parked: record held, both halves, nothing user-offlined.
ViewModeModel parkedDesignLeaf(const std::vector<std::string>& fxGuids) {
    ViewModeModel vm;
    vm.membership().tag("{T}", kDesignModeId);  // active mode is Arrange ⇒ {T} is parked
    std::vector<FxOfflineState> fx;
    for (const std::string& g : fxGuids) fx.push_back(FxOfflineState{g, 0});
    vm.storeSnapshot("{T}", recordWithFx(fx));
    return vm;
}

// Puts the queue's offline items past their debounce the way the live loop does: the
// hold starts at the FIRST observation, so advancing the clock before that one just
// moves the origin and matures nothing.
void matureHold(std::vector<ReclaimItem>& items, ParkClock& clock, FakeHost& host) {
    clock.observe(items, host.nowMs());
    host.clock += kParkHoldMs;
}

// Runs ticks until the queue settles, bounded so a non-terminating drain fails the test
// rather than hanging CTest.
int drainToSettled(std::vector<ReclaimItem>& items, ParkClock& clock, FakeHost& host,
                   int maxTicks = 64) {
    for (int t = 1; t <= maxTicks; ++t)
        if (drainTick(items, clock, host).settled) return t;
    CHECK(false);  // did not settle — the drain is not making forward progress
    return -1;
}

}  // namespace

// -- 1. debounce ---------------------------------------------------------------

static void testFastFlipMovesZeroPluginsButAHeldParkStillReclaims() {
    // A→B: {T} parks. The reclaimer must not touch it yet.
    ViewModeModel vm = parkedDesignLeaf({"{FX-A}", "{FX-B}", "{FX-C}"});
    FakeHost host;
    host.chains["{T}"] = onlineChain({"{FX-A}", "{FX-B}", "{FX-C}"});
    ParkClock clock;

    std::vector<ReclaimItem> items = derive(vm, {"{T}"});
    CHECK(items.size() == 1 && items[0].work.kind == FxWorkKind::Offline);
    CHECK(drainTick(items, clock, host).writes == 0);
    CHECK(!drainTick(items, clock, host).settled);  // waiting out its hold, not finished

    // B→A half a second later: the flags come back and the FX half is still held, so the
    // reclaimer is now owed an ONLINE — over a chain it never got round to offlining.
    host.clock = 500.0;
    vm.setActiveMode(kDesignModeId);
    vm.releaseSnapshotFlags("{T}");
    items = derive(vm, {"{T}"});
    CHECK(items.size() == 1 && items[0].work.kind == FxWorkKind::Online);
    drainToSettled(items, clock, host);

    // The whole point of the 3s hold: a fast A→B→A flip moved NO plugins.
    CHECK(host.writeLog.empty());
    CHECK(!host.offlineAt("{T}", 0) && !host.offlineAt("{T}", 1) && !host.offlineAt("{T}", 2));
    CHECK(host.released.count("{T}") == 1);  // the chain is verifiably online; record spent

    // The contrast, so the assertion above is about the hold and not about the drain
    // being inert: the same park held past 3s DOES reclaim.
    ViewModeModel held = parkedDesignLeaf({"{FX-A}", "{FX-B}", "{FX-C}"});
    FakeHost host2;
    host2.chains["{T}"] = onlineChain({"{FX-A}", "{FX-B}", "{FX-C}"});
    ParkClock clock2;
    std::vector<ReclaimItem> items2 = derive(held, {"{T}"});
    CHECK(drainTick(items2, clock2, host2).writes == 0);  // observed parked at t=0
    host2.clock = kParkHoldMs;
    drainToSettled(items2, clock2, host2);
    CHECK(host2.writeLog.size() == 3);
    CHECK(host2.offlineAt("{T}", 0) && host2.offlineAt("{T}", 1) && host2.offlineAt("{T}", 2));
    CHECK(host2.released.empty());  // an OFFLINE never releases — the record is still owed
}

// -- 2. budget: yield and resume ------------------------------------------------

static void testOfflineDrainYieldsOnBudgetAndResumesWhereItStopped() {
    ViewModeModel vm = parkedDesignLeaf({"{FX-A}", "{FX-B}", "{FX-C}", "{FX-D}"});
    FakeHost host;
    host.chains["{T}"] = onlineChain({"{FX-A}", "{FX-B}", "{FX-C}", "{FX-D}"});
    host.stepCostMs = 50.0;  // dearer than kOfflineBudgetMs ⇒ exactly one plugin per tick
    ParkClock clock;

    std::vector<ReclaimItem> items = derive(vm, {"{T}"});
    matureHold(items, clock, host);
    CHECK(drainTick(items, clock, host).writes == 1);
    CHECK(items[0].work.resumeAfterSlot == 0);
    CHECK(items[0].work.resumeAfterFxGuid == "{FX-A}");
    CHECK(!items[0].done);

    CHECK(drainTick(items, clock, host).writes == 1);
    CHECK(items[0].work.resumeAfterSlot == 1);

    // Slots 2 and 3, one per tick; the tick that writes the last one also exhausts the
    // item's write list, so it settles in the same pass rather than costing a spare tick.
    CHECK(drainToSettled(items, clock, host) == 2);

    // Each slot moved exactly once and in order — no slot re-walked across a yield.
    const std::vector<std::string> expected{"{T}:0=off", "{T}:1=off", "{T}:2=off", "{T}:3=off"};
    CHECK(host.writeLog == expected);
}

static void testOnlineDrainGetsTheLargerBudget() {
    // Same per-plugin cost, same chain length: the only difference is the direction, and
    // onlining is the one the user is waiting on.
    ViewModeModel vm = parkedDesignLeaf({"{FX-A}", "{FX-B}", "{FX-C}", "{FX-D}"});
    vm.setActiveMode(kDesignModeId);
    vm.releaseSnapshotFlags("{T}");
    FakeHost host;
    host.chains["{T}"] = offlineChain({"{FX-A}", "{FX-B}", "{FX-C}", "{FX-D}"});
    host.stepCostMs = 50.0;
    ParkClock clock;

    std::vector<ReclaimItem> items = derive(vm, {"{T}"});
    CHECK(items.size() == 1 && items[0].work.kind == FxWorkKind::Online);
    CHECK(drainTick(items, clock, host).writes == 3);  // 120ms budget vs 30ms
}

static void testATickStartedOnOnlineWorkDoesNotSpendIntoOfflineWork() {
    ViewModeModel vm;
    vm.membership().tag("{Z-back}", kArrangeModeId);  // active; owed an online
    vm.membership().tag("{A-park}", kDesignModeId);   // parked; owed an offline
    vm.storeSnapshot("{Z-back}", recordWithFx({{"{FX-1}", 0}}));
    vm.storeSnapshot("{A-park}", recordWithFx({{"{FX-2}", 0}}));

    FakeHost host;
    host.chains["{Z-back}"] = offlineChain({"{FX-1}"});
    host.chains["{A-park}"] = onlineChain({"{FX-2}"});
    host.stepCostMs = 1.0;  // cheap enough that only the kind break can stop the tick
    ParkClock clock;

    std::vector<ReclaimItem> items = derive(vm, {"{Z-back}", "{A-park}"});
    CHECK(items.size() == 2);
    CHECK(items[0].work.kind == FxWorkKind::Online);   // fx_state's ordering
    matureHold(items, clock, host);  // the parked track's hold is no longer the blocker

    CHECK(drainTick(items, clock, host).writes == 1);
    CHECK(host.writeLog == std::vector<std::string>{"{Z-back}:0=on"});
    CHECK(!host.offlineAt("{A-park}", 0));  // opportunistic reclaim waits for its own tick

    CHECK(drainTick(items, clock, host).writes == 1);
    CHECK(host.offlineAt("{A-park}", 0));
}

// -- 3. invalidation: the queue is a cache of intent ----------------------------

static void testModelChangeDiscardsDrainProgressButNotTheParkHold() {
    ViewModeModel vm = parkedDesignLeaf({"{FX-A}", "{FX-B}", "{FX-C}"});
    vm.membership().tag("{U}", kDesignModeId);  // a second parked leaf, left alone below
    vm.storeSnapshot("{U}", recordWithFx({{"{FX-U}", 0}}));

    FakeHost host;
    host.chains["{T}"] = onlineChain({"{FX-A}", "{FX-B}", "{FX-C}"});
    host.chains["{U}"] = onlineChain({"{FX-U}"});
    host.stepCostMs = 50.0;
    ParkClock clock;

    std::vector<ReclaimItem> items = derive(vm, {"{T}", "{U}"});
    drainTick(items, clock, host);          // observes both parked at t=0
    host.clock = kParkHoldMs + 100.0;
    drainTick(items, clock, host);          // one plugin moves; {T} now carries a cursor
    CHECK(items[0].work.resumeAfterSlot >= 0);

    // The model changes: {T} is retagged into the active mode and restored, while {U}
    // stays exactly as parked as it was. The queue is discarded whole — direction,
    // cursors, completion marks and all — and re-derived.
    vm.membership().tag("{T}", kArrangeModeId);
    vm.releaseSnapshotFlags("{T}");
    items = derive(vm, {"{T}", "{U}"});
    CHECK(items.size() == 2);
    CHECK(items[0].work.kind == FxWorkKind::Online);
    CHECK(items[0].work.trackGuid == "{T}");
    CHECK(items[0].work.resumeAfterSlot == -1);  // no drain progress survives a re-derive
    CHECK(items[0].work.resumeAfterFxGuid.empty());
    CHECK(!items[0].done);

    // ...but {U}'s hold does survive it. {U} never stopped being parked, and restarting
    // its 3s on every unrelated model change would defer its reclaim indefinitely.
    clock.observe(items, host.clock);
    CHECK(clock.matured("{U}", host.clock));
    CHECK(nextEligible(items, clock, host.clock) == 0);  // online first, then {U} available

    // The mirror: a track that LEAVES the offline set and comes back starts a fresh hold.
    // {T} was dropped from the clock by the observation above, while it was online.
    vm.membership().tag("{T}", kDesignModeId);
    items = derive(vm, {"{T}", "{U}"});
    clock.observe(items, host.clock);
    CHECK(!clock.matured("{T}", host.clock));
    CHECK(!clock.matured("{T}", host.clock + kParkHoldMs - 1.0));
    CHECK(clock.matured("{T}", host.clock + kParkHoldMs));
    CHECK(clock.matured("{U}", host.clock));  // and {U}'s own hold still is not restarted
}

// -- 4. the user's own offline plugins ------------------------------------------

static void testAPluginTheUserOfflinedIsNeverOnlinedByTheDrain() {
    // {FX-B} was offline before the park because the USER put it there; the record is
    // the only account of that, and an online must honor it.
    ViewModeModel vm;
    vm.membership().tag("{T}", kDesignModeId);
    vm.setActiveMode(kDesignModeId);
    vm.storeSnapshot("{T}", recordWithFx({{"{FX-A}", 0}, {"{FX-B}", 1}, {"{FX-C}", 0}}));
    vm.releaseSnapshotFlags("{T}");

    FakeHost host;
    host.chains["{T}"] = offlineChain({"{FX-A}", "{FX-B}", "{FX-C}"});  // fully parked
    ParkClock clock;

    std::vector<ReclaimItem> items = derive(vm, {"{T}"});
    drainToSettled(items, clock, host);

    CHECK(!host.offlineAt("{T}", 0));
    CHECK(host.offlineAt("{T}", 1));   // still offline — never blanket-onlined
    CHECK(!host.offlineAt("{T}", 2));
    for (const std::string& entry : host.writeLog) CHECK(entry != "{T}:1=on");
    CHECK(host.writeLog.size() == 2);
    CHECK(host.released.count("{T}") == 1);
}

// -- forward progress: the cursor cases that decide termination -----------------

static void testResumeCursorAdvancesPastAnFxWithNoIdentity() {
    // The case Wave 1's slot cursor exists for. Slot 1 is an FX REAPER reports no GUID
    // for; with the identity alone the cursor would read as "nothing done yet" and the
    // item would re-walk from slot 0 on every tick.
    ViewModeModel vm = parkedDesignLeaf({"{FX-A}", "{FX-B}", "{FX-C}"});
    FakeHost host;
    host.chains["{T}"] = onlineChain({"{FX-A}", "", "{FX-C}"});
    host.stepCostMs = 50.0;  // one plugin per tick on the offline budget
    ParkClock clock;

    std::vector<ReclaimItem> items = derive(vm, {"{T}"});
    matureHold(items, clock, host);
    drainTick(items, clock, host);
    drainTick(items, clock, host);
    CHECK(items[0].work.resumeAfterFxGuid.empty());  // slot 1 has no identity to record
    CHECK(items[0].work.resumeAfterSlot == 1);       // ...so the slot is what carries it

    CHECK(drainToSettled(items, clock, host) == 1);  // slot 2, and the item is exhausted
    const std::vector<std::string> expected{"{T}:0=off", "{T}:1=off", "{T}:2=off"};
    CHECK(host.writeLog == expected);
}

static void testSlotKeyedOnlineRecordCarriesItsCursorAsASlot() {
    // A record lifted from a project saved before FX identity existed: its targets hold
    // no identity, so a cursor taken from the LIVE identity would match none of them and
    // the item would re-walk its whole chain after every yield.
    ViewModeModel vm;
    vm.membership().tag("{T}", kDesignModeId);
    vm.setActiveMode(kDesignModeId);
    TrackSnapshot snap = recordWithFx({{"", 0}, {"", 1}, {"", 0}});
    snap.fxKeying = FxKeying::Slot;
    vm.storeSnapshot("{T}", snap);
    vm.releaseSnapshotFlags("{T}");

    FakeHost host;
    host.chains["{T}"] = offlineChain({"{FX-X}", "{FX-Y}", "{FX-Z}"});
    host.stepCostMs = kOnlineBudgetMs + 10.0;  // one plugin per tick, then yield
    ParkClock clock;

    std::vector<ReclaimItem> items = derive(vm, {"{T}"});
    CHECK(items.size() == 1 && resumeBySlotOnly(items[0].work));
    drainTick(items, clock, host);
    CHECK(items[0].work.resumeAfterFxGuid.empty());  // NOT "{FX-X}", which matches no target
    CHECK(items[0].work.resumeAfterSlot == 0);

    drainToSettled(items, clock, host);
    const std::vector<std::string> expected{"{T}:0=on", "{T}:2=on"};
    CHECK(host.writeLog == expected);  // slot 1 stays offline, as the record captured
    CHECK(host.offlineAt("{T}", 1));
}

static void testATrackThatLeftTheProjectCompletesRatherThanStalls() {
    ViewModeModel vm = parkedDesignLeaf({"{FX-A}"});
    FakeHost host;  // no chain registered ⇒ liveChain reports the track gone
    ParkClock clock;

    std::vector<ReclaimItem> items = derive(vm, {"{T}"});
    matureHold(items, clock, host);
    CHECK(drainTick(items, clock, host).settled);
    CHECK(host.writeLog.empty());
    CHECK(host.released.empty());  // the next apply's reconcile drops the whole record
}

int main() {
    testFastFlipMovesZeroPluginsButAHeldParkStillReclaims();

    testOfflineDrainYieldsOnBudgetAndResumesWhereItStopped();
    testOnlineDrainGetsTheLargerBudget();
    testATickStartedOnOnlineWorkDoesNotSpendIntoOfflineWork();

    testModelChangeDiscardsDrainProgressButNotTheParkHold();

    testAPluginTheUserOfflinedIsNeverOnlinedByTheDrain();

    testResumeCursorAdvancesPastAnFxWithNoIdentity();
    testSlotKeyedOnlineRecordCarriesItsCursorAsASlot();
    testATrackThatLeftTheProjectCompletesRatherThanStalls();

    if (g_fail == 0) std::printf("All tests passed.\n");
    return g_fail ? 1 : 0;
}