#pragma once
// Design View's per-FX offline surface: the FX-identity read that snapshot,
// park and restore all address FX through, the deferred intent queue that keeps
// TrackFX_SetOffline off the mode switch's synchronous path, and the two drains
// that apply it — restores whole, parks one FX per idle tick. See
// src/shell/view/CLAUDE.md's FX-parking caveat.

#include <string>
#include <vector>

#include "core/view/fx_offline.h"

// Forward-declared to keep this header SDK-free; the .cpp includes the real SDK header.
class MediaTrack;
class ReaProject;

namespace reasampler {

// The coalescing delay's gate, pure so the debounce can be asserted without a
// DAW clock (test_view_fx_park.cpp). parkReadyAt is called on EVERY enqueue,
// not just the first — that re-arming from each call's own `now` is what makes
// it a debounce rather than a one-shot timer, and is what lets a rapid A→B→A
// flip (three enqueues inside one delay window) cost a single wait measured
// from the last flip rather than three, or one anchored to the first.
inline double parkReadyAt(double now, double coalesceSeconds) { return now + coalesceSeconds; }
inline bool   parkIsReady(double now, double readyAt) { return now >= readyAt; }

// The chain as it stands now: identity by current slot. Snapshot, park and
// restore all address FX through this one plain 0..TrackFX_GetCount-1
// enumeration — never the 0x1000000/0x2000000 input-FX or container forms — so
// whatever it covers, all three cover identically.
std::vector<std::string> liveFxGuids(MediaTrack* tr);

// One deferred per-FX intent for one track. A park carries no ops (every live
// slot goes offline); a restore carries the planned ops verbatim.
struct FxParkIntent {
    std::string guid;
    bool        park = false;
    // Set once a park write has landed on this track — the live chain then
    // matches NEITHER endpoint, so the cancel-on-inverse rule below is unsafe
    // until the intent resumes/supersedes instead of annihilating. Restores
    // carry no such state: they are detached whole and applied in one drain.
    // Full contract: src/shell/view/CLAUDE.md's `view_fx_park` entry.
    bool                     partial = false;
    std::vector<FxOfflineOp> restoreOps;
};

// The queue's re-entrancy rule, pure so it can be asserted without a DAW: at
// most ONE intent per track GUID, and the latest one wins. Park and restore are
// inverses, so an UNSTARTED intent landing on its own pending inverse CANCELS it
// rather than stacking — the queued work never ran, so the track already holds
// the state the newcomer asks for, and replaying both would be both slower and
// observably wrong. That cancel is what makes a rapid A→B→A mode flip cost zero
// plugin work: B→A's restore annihilates A's park before a single FX moved.
class FxParkQueue {
public:
    // Returns the ops of a pending restore this park CANCELLED, empty otherwise.
    // The caller needs them: that restore never ran, so the live chain still
    // reads the PARKED offline states and is no longer a source for a fresh
    // pre-park snapshot (see preParkFxFromCancelledRestore).
    //
    // The empty return is a LOAD-BEARING sentinel that deliberately conflates
    // "nothing was cancelled" with "cancelled a restore carrying no ops": a
    // zero-op restore held no FX state to hand back, so falling through to a
    // live chain read is the same answer, not a worse one.
    std::vector<FxOfflineOp> park(const std::string& guid) {
        FxParkIntent* held = find(guid);
        if (!held) {
            pending_.push_back(FxParkIntent{guid, true, false, {}});
            return {};
        }
        if (held->park) return {};
        std::vector<FxOfflineOp> cancelled = std::move(held->restoreOps);
        if (held->partial) *held = FxParkIntent{guid, true, true, {}};
        else               erase(held);
        return cancelled;
    }

    // A restore cancelling an UNSTARTED park is COMPLETE at that point — the
    // park never ran, so no drain will ever come for this GUID. Against a park
    // that has already written, the restore supersedes instead: its ops are the
    // only thing that can put the offlined FX back.
    void restore(const std::string& guid, std::vector<FxOfflineOp> ops) {
        FxParkIntent* held = find(guid);
        if (!held) {
            pending_.push_back(FxParkIntent{guid, false, false, std::move(ops)});
        } else if (held->park && !held->partial) {
            erase(held);
        } else if (held->park) {
            *held = FxParkIntent{guid, false, true, std::move(ops)};
        } else {
            held->restoreOps = std::move(ops);
        }
    }

    // Enqueue order, which is apply order WITHIN a kind — the two kinds drain
    // separately and on different schedules (see the two drains below).
    const std::vector<FxParkIntent>& pending() const { return pending_; }
    bool empty() const { return pending_.empty(); }
    void clear() { pending_.clear(); }

    // Detaches every pending RESTORE and leaves the parks behind, in order. The
    // detach — not a live iteration, not a clear afterwards — is what lets the
    // queue accept intents enqueued WHILE the caller applies what it took:
    // [verify — DAW] applying loads/unloads plugins, which is ASSUMED to pump
    // the message loop, so a re-entrant switch can enqueue mid-apply. Iterating
    // the live queue would dangle on the push_back and clearing it afterwards
    // would discard whatever arrived. Correct either way; only the need for it
    // is unconfirmed.
    std::vector<FxParkIntent> takeRestores() {
        std::vector<FxParkIntent> taken;
        std::vector<FxParkIntent> kept;
        for (FxParkIntent& i : pending_) {
            if (i.park) kept.push_back(std::move(i));
            else        taken.push_back(std::move(i));
        }
        pending_.swap(kept);
        return taken;
    }

    // The park the drain should work next, in enqueue order; empty when none is
    // pending. A PEEK, by value — an apply can reshape the queue under a pointer
    // — and it marks nothing: a park still cancellable for free stays that way
    // until markPartial says a write is imminent.
    std::string nextParkGuid() const {
        for (const FxParkIntent& i : pending_)
            if (i.park) return i.guid;
        return {};
    }

    // Records that a park write is ABOUT TO land on `guid` — set before the
    // write, because the write may pump the message loop and an intent arriving
    // in that window must already see a chain that matches neither endpoint.
    void markPartial(const std::string& guid) {
        if (FxParkIntent* held = find(guid)) held->partial = true;
    }

    // Retires a park with nothing left to offline. A no-op when a restore
    // replaced it mid-apply — that restore is the newer intent and owns the
    // chain from here.
    void finishPark(const std::string& guid) {
        FxParkIntent* held = find(guid);
        if (held && held->park) erase(held);
    }

private:
    FxParkIntent* find(const std::string& guid) {
        for (FxParkIntent& i : pending_)
            if (i.guid == guid) return &i;
        return nullptr;
    }
    void erase(FxParkIntent* held) {
        pending_.erase(pending_.begin() + (held - pending_.data()));
    }

    std::vector<FxParkIntent> pending_;
};

// The FX half of a snapshot, with the keying it must be read back under.
struct PreParkFx {
    std::vector<FxOfflineState> states;
    FxKeying                    keying = FxKeying::Identity;
};

// The FX half a fresh pre-park snapshot must carry when the park CANCELLED a
// pending restore: those ops are the only surviving record of the pre-park
// state, because the chain still reads the parked values and the cancel means
// no drain will ever put them back. Empty (nothing cancelled) means the caller
// reads the live chain instead; the restore's own keying travels with it so a
// slot-keyed snapshot does not silently become identity-keyed with no
// identities. The ops describe the chain as of the ORIGINAL park, not the live
// chain applyPark re-enumerates at drain time — so an FX added while parked (a
// floating FX-chain window, ReaScript) is absent here yet still offlined by the
// cancelling park's drain, and never comes back online. Rare and hand-recoverable.
// `offline` widens back from FxOfflineOp's bool to FxOfflineState's defensive int
// — restoring the type, not adding information.
inline PreParkFx preParkFxFromCancelledRestore(const std::vector<FxOfflineOp>& cancelled) {
    PreParkFx out;
    if (cancelled.empty()) return out;
    out.keying = cancelled.front().keying;
    out.states.reserve(cancelled.size());
    for (const FxOfflineOp& op : cancelled)
        out.states.push_back(FxOfflineState{op.fxGuid, op.offline ? 1 : 0});
    return out;
}

// The FX half of a fresh pre-park snapshot for `tr`: whatever the accompanying
// park cancelled, else a live read of the chain.
PreParkFx snapshotFxOffline(MediaTrack* tr, const std::vector<FxOfflineOp>& cancelled);

// Enqueue against `proj` (nullptr = current project). An enqueue naming a
// different project than the pending intents discards those unapplied. The park
// returns whatever pending restore it cancelled, per FxParkQueue::park.
std::vector<FxOfflineOp> deferFxPark(ReaProject* proj, const std::string& guid);
void deferFxRestore(ReaProject* proj, const std::string& guid, std::vector<FxOfflineOp> ops);

// The two halves of the drain, split because only ONE of them is unsafe to
// persist over. Both touch NO model state — a restore's snapshot is dropped
// where the restore is planned (applyMode) — both discard the queue unapplied if
// the project it was enqueued against is no longer current (close / switch),
// both prune an intent whose track is gone, both cost one empty-queue test when
// idle, and both early-out re-entrantly: one drain at a time, the outer one owns
// the queue.
//
// RESTORES, applied whole, synchronously. Called on the idle tick and forced by
// a subset of the paths that serialize the view model. WHICH paths force it, and
// why forcing is required, is src/shell/view/CLAUDE.md's Documented-caveat entry
// — kept there only, not restated here, so the two cannot drift apart.
void drainDeferredFxRestores();

// PARKS, one FX per idle tick behind a short coalescing delay (parkReadyAt /
// parkIsReady above). Unlike a restore it is safe to persist over — it
// converges on its own; see CLAUDE.md for why, and for the CPU-reclaim-is-
// progressive consequence.
//
// One FX, not one track: a single convolution reverb or loaded sampler is the
// unit of cost, so per-track chunking would not bound the hitch — only the
// per-FX split does, and only to ONE FX's unload per tick, not to zero.
//
// The live-enumeration hazard's width is delay + (FX count × tick interval), NOT
// the delay alone: firstOnlineFx re-enumerates the chain LIVE every tick, not
// just the first, so an FX added at any point before the park retires is
// offlined carrying no snapshot entry — resolveFxRestore then has no op for it
// and it stays offline. Same failure as the cancelled-restore case above, over a
// longer window. Do not lengthen the delay casually; it is only one term.
void tickDeferredFxParks();

// Drops every pending intent without applying it. Called when the model the
// intents were planned against has been replaced (project load/switch, undo/redo
// state restore) — applying them then would write the pre-reload plan over the
// project that replaced it.
//
// Not pure loss: the caller reapplies the active mode over the reloaded model
// immediately after, which re-plans a park for every inactive leaf, so parked FX
// converge on the following drain. The case that does NOT self-heal is a track
// whose reloaded model carries no snapshot — nothing plans a restore for it, so
// FX left offline stay offline.
void discardDeferredFxParks();

} // namespace reasampler