// bridge_marshal.h — PURE marshalling helper for the REAPER VST-host bridge read.
// NO VST3, NO REAPER types at the boundary.
//
// The bridge shell (reaper_bridge.cpp) resolves REAPER API functions by name over the
// host callback and invokes them; the one fiddly-and-easy-to-get-wrong part around
// GetProjExtState — interpreting its int return against the buffer it filled — is pure
// and unit-tested here. Mirror of capture_paths / wav_trim splitting the arithmetic out
// of a REAPER-facing shell.
//
// The S1 spike ALSO carried a string-scan JSON reader (extractJsonStringField) as a
// stand-in until the instrument could parse the bank properly. S4 retired it: the
// instrument now parses the "reasampler" bank blob through the SHARED bank_book /
// bank_model JSON path (sample_map.cpp), so there is no second JSON parser. This module
// is back to its one honest job — the API-return decode.
//
// Verified against vendor/reaper-sdk/sdk/reaper_plugin_functions.h:
//   int  GetProjExtState (ReaProject*, extname, key, valOutNeedBig, valOutNeedBig_sz);
//        -- returns the length written (0 when the key is absent).

#pragma once

#include <optional>
#include <string>

namespace reasampler::vst {

// Interpret a GetProjExtState result: the int return value (bytes the API reports for
// the key) and the buffer it filled. Returns the value only when the API reported a
// non-empty result AND the buffer is non-empty — REAPER writes 0 and leaves the buffer
// untouched for an absent key, and we must not treat stale buffer contents as a hit.
//
// `apiReturn` is GetProjExtState's return; `buffer` is the NUL-terminated string it
// wrote (already truncated to the C string by the caller).
std::optional<std::string> decodeGetProjExtState(int apiReturn,
                                                  const std::string& buffer);

}  // namespace reasampler::vst