reasampler/src/vst/reasampler_processor.cpp

// reasampler_processor.cpp — see reasampler_processor.h.

#include "reasampler_processor.h"

#include <algorithm>
#include <cstdint>
#include <fstream>
#include <vector>

#include "pluginterfaces/base/ibstream.h"
#include "pluginterfaces/vst/ivstaudioprocessor.h"
#include "pluginterfaces/vst/ivstevents.h"
#include "pluginterfaces/vst/vstspeaker.h"

#include "capture_paths.h"   // resolveBankFile (shared M4 path resolution)
#include "ext_keys.h"        // kProjExtBanksKey (shared wire contract)
#include "reasampler_editor.h"
#include "sample_map.h"       // selectSample, downmixToMono, buildTier0Keymap, state (de)ser
#include "wav_trim.h"         // parseWavLayout, extractFloatFrames (shared WAV parse)

using namespace Steinberg;
using namespace Steinberg::Vst;

namespace reasampler::vst {

namespace {

// Tier-0 fixed instrument shape (Tier 2 makes these editable). A gentle amp envelope so
// notes neither click on nor cut off abruptly; sustain at unity (velocity does the
// dynamics), a short release for a natural tail. Times are in seconds, converted to
// frames against the live sample rate at build time.
constexpr double kAttackSeconds = 0.003;
constexpr double kDecaySeconds = 0.0;
constexpr double kSustainLevel = 1.0;
constexpr double kReleaseSeconds = 0.060;
constexpr std::size_t kMaxVoices = 16;

AdsrParams tier0Adsr(double sampleRate) {
    const double sr = sampleRate > 0.0 ? sampleRate : 44100.0;
    AdsrParams p;
    p.attackFrames = static_cast<std::int64_t>(kAttackSeconds * sr);
    p.decayFrames = static_cast<std::int64_t>(kDecaySeconds * sr);
    p.sustainLevel = kSustainLevel;
    p.releaseFrames = static_cast<std::int64_t>(kReleaseSeconds * sr);
    return p;
}

// Read a whole file into a byte buffer. Off-thread only (blocking file I/O). Empty on
// any failure — the caller treats an unreadable WAV as "nothing to play".
std::vector<std::uint8_t> readFileBytes(const std::string& path) {
    std::vector<std::uint8_t> bytes;
    std::ifstream f(path, std::ios::binary | std::ios::ate);
    if (!f) return bytes;
    const std::streamoff size = f.tellg();
    if (size <= 0) return bytes;
    f.seekg(0, std::ios::beg);
    bytes.resize(static_cast<std::size_t>(size));
    if (!f.read(reinterpret_cast<char*>(bytes.data()), size)) bytes.clear();
    return bytes;
}

}  // namespace

FUnknown* ReaSamplerProcessor::createInstance(void* /*context*/) {
    // The host owns the returned reference. Cast up to the combined interface the SDK
    // exposes (IAudioProcessor) so the FUnknown refcount is correctly rooted.
    return static_cast<IAudioProcessor*>(new ReaSamplerProcessor());
}

tresult PLUGIN_API ReaSamplerProcessor::initialize(FUnknown* context) {
    tresult result = SingleComponentEffect::initialize(context);
    if (result != kResultOk) return result;

    // Connect the REAPER bridge. Non-fatal if it fails (non-REAPER host): the
    // instrument still loads, it just has no live bank to play.
    bridge_.connect(context);

    // Instrument bus topology: one event input (MIDI in, 16 channels), one stereo audio
    // output, no audio input. This is the standard VSTi arrangement.
    addEventInput(STR16("MIDI In"), 16);
    addAudioOutput(STR16("Stereo Out"), SpeakerArr::kStereo);

    return kResultOk;
}

tresult PLUGIN_API ReaSamplerProcessor::terminate() {
    // process() is not running at terminate. Free the live instrument and drain the
    // graveyard. Take the pointer out of the atomic first so nothing else races it.
    std::lock_guard<std::mutex> lock(reloadMutex_);
    delete live_.exchange(nullptr);
    graveyard_.clear();
    return SingleComponentEffect::terminate();
}

tresult PLUGIN_API ReaSamplerProcessor::setActive(TBool state) {
    // Activating: build the instrument from the currently-selected sample so the first
    // block after activation can play. Deactivating: process is now GUARANTEED stopped by
    // the host, so this is the safe point to reclaim the graveyard (the displaced engines
    // no reload could free while active). The build/drain are off the audio thread —
    // setActive is a main/UI-thread call.
    if (state) {
        reloadFromBank();
    } else {
        std::lock_guard<std::mutex> lock(reloadMutex_);
        graveyard_.clear();
    }
    return kResultOk;
}

tresult PLUGIN_API ReaSamplerProcessor::setupProcessing(ProcessSetup& setup) {
    sampleRate_ = setup.sampleRate;
    maxBlockSize_ = setup.maxSamplesPerBlock;
    return SingleComponentEffect::setupProcessing(setup);
}

tresult PLUGIN_API ReaSamplerProcessor::setState(IBStream* state) {
    if (!state) return kResultFalse;
    // Read the whole component-state blob (the selected sample id, versioned). The blob
    // is small; read in one shot into a growable buffer.
    std::vector<std::uint8_t> bytes;
    std::uint8_t chunk[256];
    int32 got = 0;
    while (state->read(chunk, sizeof(chunk), &got) == kResultOk && got > 0) {
        bytes.insert(bytes.end(), chunk, chunk + got);
    }
    setSelectedSampleId(deserializeSelection(bytes));
    // Rebuild from the restored selection (off-thread — setState is a load-time call).
    reloadFromBank();
    return kResultOk;
}

tresult PLUGIN_API ReaSamplerProcessor::getState(IBStream* state) {
    if (!state) return kResultFalse;
    const std::vector<std::uint8_t> bytes = serializeSelection(selectedSampleId());
    if (!bytes.empty()) {
        const tresult wr = state->write(const_cast<std::uint8_t*>(bytes.data()),
                                        static_cast<int32>(bytes.size()), nullptr);
        if (wr != kResultOk) return wr;
    }
    return kResultOk;
}

std::string ReaSamplerProcessor::selectedSampleId() {
    std::lock_guard<std::mutex> lock(selectionMutex_);
    return selectedSampleId_;
}

void ReaSamplerProcessor::setSelectedSampleId(const std::string& id) {
    std::lock_guard<std::mutex> lock(selectionMutex_);
    selectedSampleId_ = id;
}

std::string ReaSamplerProcessor::reloadFromBank() {
    // OFF THE AUDIO THREAD. Serialize concurrent reloads (editor click + setState) so
    // the retired-slot free is single-writer. This mutex is NEVER taken on the audio
    // thread — process() only touches the atomic.
    std::lock_guard<std::mutex> lock(reloadMutex_);

    // Mint this reload's generation number first so we can stamp the built instrument
    // with it before publishing. Under reloadMutex_ no other reload races here.
    const std::uint64_t gen = reloadGeneration_.fetch_add(1, std::memory_order_relaxed) + 1;

    // 1. Read the live bank + resolve the project dir over the bridge (allocates,
    //    calls REAPER — fine here, off-thread).
    std::optional<std::string> banksJson =
        bridge_.readReasamplerExtState(kProjExtBanksKey);
    const std::string projectDir = bridge_.activeProjectDir();

    std::string resolvedId;
    std::unique_ptr<LoadedInstrument> built;

    if (banksJson) {
        // 2. Pick the sample (shared bank_book JSON parse — NOT a second parser).
        std::optional<SelectedSample> sel =
            selectSample(*banksJson, selectedSampleId());
        if (sel) {
            // 3. Resolve the project-relative WAV path the M4 way persist does, read +
            //    decode it (file I/O off-thread), downmix to the core's mono contract.
            const std::string abs = resolveBankFile(projectDir, sel->relativePath);
            if (!abs.empty()) {
                const std::vector<std::uint8_t> bytes = readFileBytes(abs);
                const WavLayout layout = parseWavLayout(bytes);
                if (layout.valid) {
                    const std::size_t frames = layout.frameCount();
                    std::vector<AudioSample> interleaved =
                        extractFloatFrames(bytes, layout, 0, frames);
                    std::vector<AudioSample> mono =
                        downmixToMono(interleaved, layout.channelCount);
                    if (!mono.empty()) {
                        Keymap km = buildTier0Keymap(
                            std::move(mono),
                            static_cast<int>(layout.sampleRate), sel->rootNote,
                            sel->loop);
                        built = std::make_unique<LoadedInstrument>(
                            std::move(km), kMaxVoices, tier0Adsr(sampleRate_), gen);
                        // Record which id actually resolved so a first-sample fallback
                        // (empty stored id) becomes the concrete selection.
                        resolvedId = selectedSampleId();
                    }
                }
            }
        }
    }

    // 4. Publish. Atomically install the new instrument; the DISPLACED one goes to the
    //    graveyard tagged with this generation (process may still be mid-block reading
    //    it). A null `built` (no bank / unreadable WAV) installs silence.
    //    `built` is heap-owned; release() hands ownership to the atomic, and the
    //    exchanged pointer is re-owned by the graveyard.
    //
    //    Bounded reclaim: prune graveyard entries where displacedAt <= seen, where seen
    //    is the last generation process() published. process() publishes inst->installedAt
    //    (not a re-read of reloadGeneration_), so seen == D means process holds the
    //    instrument installed at gen D. An entry with displacedAt == D was displaced by
    //    reload D, which installed that very successor — process cannot be holding the
    //    displaced entry. The pruning condition is therefore <= (see header for the full
    //    proof). Remaining entries drain at setActive(false) / terminate() when process
    //    is guaranteed stopped.
    const std::uint64_t seen = processGeneration_.load(std::memory_order_acquire);
    graveyard_.erase(
        std::remove_if(graveyard_.begin(), graveyard_.end(),
                       [seen](const GraveyardEntry& e) { return e.displacedAt <= seen; }),
        graveyard_.end());
    LoadedInstrument* prev = live_.exchange(built.release());
    if (prev) graveyard_.push_back({gen, std::unique_ptr<LoadedInstrument>(prev)});
    return resolvedId;
}

tresult PLUGIN_API ReaSamplerProcessor::process(ProcessData& data) {
    // REAL-TIME: no allocation, no IO, no locks. Load the live instrument once for the
    // whole block (a single atomic acquire), then publish inst->installedAt so the off-
    // thread graveyard pruner knows exactly which generation this block is holding.
    //
    // We publish installedAt — not a fresh re-read of reloadGeneration_ — to close an
    // ordering race: reading reloadGeneration_ after live_ could observe a generation
    // newer than the pointer we actually hold, causing the pruner to free an instrument
    // process is still reading. installedAt was set on the reload path before the atomic
    // exchange that made the instrument visible, so it is always <= the generation of any
    // instrument that could have been loaded after our acquire above.
    LoadedInstrument* inst = live_.load(std::memory_order_acquire);
    const std::uint64_t heldGen = inst ? inst->installedAt : 0;
    processGeneration_.store(heldGen, std::memory_order_release);

    // Marshal MIDI note-on/off from the event input into the voice engine. Tier 0 maps
    // events at block granularity (no per-event sample-offset split) — audible timing is
    // within one block, adequate for Tier 0; sample-accurate scheduling is a later tier.
    if (inst && data.inputEvents) {
        const int32 count = data.inputEvents->getEventCount();
        for (int32 i = 0; i < count; ++i) {
            Event e;
            if (data.inputEvents->getEvent(i, e) != kResultOk) continue;
            if (e.type == Event::kNoteOnEvent) {
                // A note-on with velocity 0 is a note-off by MIDI convention.
                const int vel = static_cast<int>(e.noteOn.velocity * 127.0f + 0.5f);
                if (vel <= 0) {
                    inst->engine.noteOff(e.noteOn.pitch);
                } else {
                    inst->engine.noteOn(e.noteOn.pitch, vel);
                }
            } else if (e.type == Event::kNoteOffEvent) {
                inst->engine.noteOff(e.noteOff.pitch);
            }
        }
    }

    if (data.numOutputs <= 0 || !data.outputs || data.numSamples <= 0) {
        return kResultOk;
    }
    AudioBusBuffers& out = data.outputs[0];
    const int32 frames = data.numSamples;

    // 64-bit host processing is not supported by the mono float core; emit silence
    // rather than mis-render. REAPER runs 32-bit float by default.
    if (data.symbolicSampleSize != kSample32) {
        for (int32 ch = 0; ch < out.numChannels; ++ch) {
            if (double* buf = out.channelBuffers64[ch]) {
                for (int32 i = 0; i < frames; ++i) buf[i] = 0.0;
            }
        }
        out.silenceFlags = (out.numChannels >= 64)
                               ? ~0ULL
                               : ((1ULL << out.numChannels) - 1);
        return kResultOk;
    }

    // Render mono into channel 0's buffer, then replicate to the other channels (the
    // core is mono-per-sample). Clear channel 0 first (render ADDS), then mix.
    float* ch0 = out.numChannels > 0 ? out.channelBuffers32[0] : nullptr;
    if (ch0) {
        for (int32 i = 0; i < frames; ++i) ch0[i] = 0.f;
        if (inst) {
            inst->engine.render(ch0, static_cast<std::size_t>(frames));
        }
        // Duplicate the mono render across the remaining output channels.
        for (int32 ch = 1; ch < out.numChannels; ++ch) {
            if (float* buf = out.channelBuffers32[ch]) {
                for (int32 i = 0; i < frames; ++i) buf[i] = ch0[i];
            }
        }
    }

    // Report silence only when nothing is loaded (lets the host optimize when idle).
    // With an instrument loaded we clear the flag so a ringing voice is not skipped.
    out.silenceFlags = inst ? 0 : ((out.numChannels >= 64)
                                       ? ~0ULL
                                       : ((1ULL << out.numChannels) - 1));
    return kResultOk;
}

IPlugView* PLUGIN_API ReaSamplerProcessor::createView(FIDString name) {
    if (name && FIDStringsEqual(name, ViewType::kEditor)) {
        return new ReaSamplerEditor(this);
    }
    return nullptr;
}

}  // namespace reasampler::vst