#include "./stacktrace.hpp"

#include <cstdint>
#include <optional>
#include <string>
#include <backtrace.h>

namespace mijin
{
namespace
{
//
// internal defines
//

//
// internal constants
//

//
// internal types
//

struct BacktraceData
{
    std::optional<std::string> error;
    std::vector<Stackframe> stackframes;
};

//
// internal variables
//

//
// internal functions
//

int backtraceFullCallback(void* data, std::uintptr_t programCounter, const char* filename, int lineno, const char* function)
{
    BacktraceData& btData = *static_cast<BacktraceData*>(data);
    btData.stackframes.push_back({
        .address = reinterpret_cast<void*>(programCounter),
        .filename = filename ? filename : "<unknown>",
        .function = function ? function : "<unknown>",
        .lineNumber = lineno
    });
    return 0;
}

void backtraceErrorCallback(void* data, const char* msg, int /* errnum */)
{
    BacktraceData& btData = *static_cast<BacktraceData*>(data);
    btData.error = msg;
}

thread_local backtrace_state* gBacktraceState = nullptr;
} // namespace

//
// public functions
//

Result<Stacktrace> captureStacktrace(unsigned skipFrames) noexcept
{
    BacktraceData btData;
    if (gBacktraceState == nullptr)
    {
        gBacktraceState = backtrace_create_state(/*filename = */ nullptr, /* threaded = */ false, &backtraceErrorCallback, &btData);
    }
    if (btData.error.has_value())
    {
        return ResultError(std::move(*btData.error));
    }
    if (gBacktraceState == nullptr)
    {
        return ResultError("Error initializing libbacktrace.");
    }
    backtrace_full(gBacktraceState, static_cast<int>(skipFrames) + 1, &backtraceFullCallback, &backtraceErrorCallback, &btData);
    if (btData.error.has_value())
    {
        return ResultError(std::move(*btData.error));
    }

    return Stacktrace(std::move(btData.stackframes));
}

} // namespace mijin