// 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 (vst/reasampler_uid.h).

#include "instrument_drop.h"

#include <cstdio>

#include "vst/reasampler_uid.h"  // REASAMPLER_ACTIVE_UID_* — the FROZEN, channel-selected class UID
#include "vst/sample_map.h"      // ComponentState + serializeComponentState (the SHARED writer)

namespace reasampler {

namespace {

// Little-endian appenders — the .vstpreset container stores its integers little-endian on
// disk (public.sdk vstpresetfile.cpp swaps only on big-endian hosts).
void appendU32LE(std::vector<std::uint8_t>& out, std::uint32_t v) {
    out.push_back(static_cast<std::uint8_t>(v & 0xFF));
    out.push_back(static_cast<std::uint8_t>((v >> 8) & 0xFF));
    out.push_back(static_cast<std::uint8_t>((v >> 16) & 0xFF));
    out.push_back(static_cast<std::uint8_t>((v >> 24) & 0xFF));
}

void appendU64LE(std::vector<std::uint8_t>& out, std::uint64_t v) {
    for (int i = 0; i < 8; ++i)
        out.push_back(static_cast<std::uint8_t>((v >> (8 * i)) & 0xFF));
}

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

}  // namespace

std::string vstClassIdHex() {
    // FUID::toString reduces to the four INLINE_UID words as "%08X" in order on BOTH byte
    // layouts (see header contract), so rendering the macros directly is the platform-stable
    // derivation of the string the .vstpreset header must carry.
    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");
    appendU32LE(out, 1);  // kFormatVersion
    out.insert(out.end(), classIdHex32.begin(), classIdHex32.end());
    appendU64LE(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");
    appendU32LE(out, 1);
    appendFourCC(out, "Comp");
    appendU64LE(out, kHeaderSize);
    appendU64LE(out, compSize);
    return out;
}

std::vector<std::uint8_t> instrumentDropStateBytes(const std::string& sampleId) {
    // The ONE fact the drop carries: this capture is the instance's selection. Everything
    // else stays at the fresh-instance defaults (no zones, implicit channel mode, generation
    // 0) — the same ComponentState a browser click would produce. The implicit mode means
    // the GA auto-default will follow the loaded capture's channel count on first reload.
    // serializeComponentState is the instrument's own writer (the single source of truth for
    // the byte layout), so this is NOT a parallel encoder — it IS the instrument's encoder.
    ComponentState cs;
    cs.selectionId = sampleId;
    return serializeComponentState(cs);
}

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

bool infoNamesFxHotspot(const std::string& info) {
    // See the header contract. Prefix rule (S-GA-DropFX): "fx_" names the FX-chain /
    // floating-FX windows; "tcp.fx" / "mcp.fx" prefixes name the TCP/MCP FX button and its
    // sibling FX sub-elements (fxbyp/fxparm/fxlist...), tolerant of the SDK-documented "may
    // append additional information". Bare "tcp"/"mcp" and non-FX sub-elements ("tcp.mute",
    // "tcp.vol") must NOT trigger an instrument drop.
    //
    // EXCLUDE the embed-strip sub-element ("tcp.fxembed" / "mcp.fxembed"): that is the
    // surface where a ReaSampler 9000 embed strip draws inside the TCP/MCP. Dropping a card
    // there must NOT add a SECOND instance — the surface is the existing instance's own UI,
    // not an FX-chain drop target. It starts with "tcp.fx" so it must be explicitly excluded.
    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