// instrument_drop — pure implementation. See instrument_drop.h.
// No REAPER/SWELL/VST3 SDK/vendor. Reuses sample_map's ComponentState serializer
// and the SDK-free UID macros (reasampler_uid.h).

#include "core/wire/instrument_drop.h"

#include <cstdio>

#include "core/wire/reasampler_uid.h"  // REASAMPLER_ACTIVE_UID_* — the FROZEN, channel-selected class UID
#include "core/instrument/map/component_state_io.h"  // ComponentState + serializeComponentState (the SHARED writer)
#include "core/wire/bytes.h"           // putLE — the ONE LE byte codec

namespace reasampler::wire {

using instrument::map::ComponentState;
using instrument::map::serializeComponentState;

namespace {

// The .vstpreset container stores its integers little-endian on disk (public.sdk
// vstpresetfile.cpp swaps only on big-endian hosts) — putLE is exactly that byte order.

void appendFourCC(std::vector<std::uint8_t>& out, const char id[4]) {
    out.insert(out.end(), id, id + 4);
}

}  // namespace

std::string vstClassIdHex() {
    char buf[33];
    std::snprintf(buf, sizeof(buf), "%08X%08X%08X%08X",
                  static_cast<unsigned>(REASAMPLER_ACTIVE_UID_1),
                  static_cast<unsigned>(REASAMPLER_ACTIVE_UID_2),
                  static_cast<unsigned>(REASAMPLER_ACTIVE_UID_3),
                  static_cast<unsigned>(REASAMPLER_ACTIVE_UID_4));
    return std::string(buf, 32);
}

std::vector<std::uint8_t> buildVstPresetBytes(
    const std::string& classIdHex32, const std::vector<std::uint8_t>& componentState) {
    std::vector<std::uint8_t> out;
    if (classIdHex32.size() != 32) return out;  // contract violation -> empty, never throws

    // Header (48 bytes): 'VST3' + int32 version + 32-char class ID + int64 list offset.
    constexpr std::uint64_t kHeaderSize = 4 + 4 + 32 + 8;
    const std::uint64_t compSize = componentState.size();
    const std::uint64_t listOffset = kHeaderSize + compSize;

    out.reserve(static_cast<std::size_t>(listOffset) + 4 + 4 + (4 + 8 + 8));
    appendFourCC(out, "VST3");
    putLE<std::uint32_t>(out, 1);  // kFormatVersion
    out.insert(out.end(), classIdHex32.begin(), classIdHex32.end());
    putLE<std::uint64_t>(out, listOffset);

    // Data area: the one 'Comp' chunk's bytes, at offset kHeaderSize.
    out.insert(out.end(), componentState.begin(), componentState.end());

    // Chunk list: 'List' + entry count + one entry {'Comp', offset, size}.
    appendFourCC(out, "List");
    putLE<std::uint32_t>(out, 1);
    appendFourCC(out, "Comp");
    putLE<std::uint64_t>(out, kHeaderSize);
    putLE<std::uint64_t>(out, compSize);
    return out;
}

std::vector<std::uint8_t> instrumentDropStateBytes(const std::string& sampleId) {
    // Everything but selectionId stays at fresh-instance defaults (no zones,
    // implicit channel mode, generation 0) — same as a browser click.
    ComponentState cs;
    cs.selectionId = sampleId;
    return serializeComponentState(cs);
}

std::vector<std::uint8_t> buildInstrumentDropPreset(const std::string& sampleId) {
    return buildVstPresetBytes(vstClassIdHex(), instrumentDropStateBytes(sampleId));
}

DropOutcome decideDropOutcome(const DropAttempt& attempt) {
    DropOutcome out;
    if (attempt.addedFxIndex < 0) return out;  // add failed — nothing exists to roll back
    if (!attempt.presetApplied) {
        out.rollbackFxIndex = attempt.addedFxIndex;
        return out;
    }
    out.loaded = true;
    return out;
}

bool infoNamesFxHotspot(const std::string& info) {
    // See the header contract for the prefix rule and the embed-strip exclusion.
    auto startsWith = [&info](const char* p) { return info.rfind(p, 0) == 0; };
    if (startsWith("tcp.fxembed") || startsWith("mcp.fxembed")) return false;
    return startsWith("fx_") || startsWith("tcp.fx") || startsWith("mcp.fx");
}

}  // namespace reasampler::wire