/*
 * VizionStreamer - Shared Memory Writer Interface
 * Copyright (c) 2025 Maik Jurischka
 *
 * Licensed under CC BY-NC-SA 4.0
 * https://creativecommons.org/licenses/by-nc-sa/4.0/
 */

#pragma once

#include <string>
#include <cstdint>
#include <atomic>

// Shared memory header structure for lock-free synchronization
struct SharedMemoryHeader {
    uint32_t magic;                      // Magic number for validation (0x56495A4E = "VIZN")
    uint32_t width;                      // Frame width in pixels
    uint32_t height;                     // Frame height in pixels
    uint32_t format;                     // Format enum (matches VX_IMAGE_FORMAT)
    uint32_t data_size;                  // Actual frame data size in bytes
    uint64_t timestamp_ns;               // Timestamp in nanoseconds
    uint32_t frame_sequence;             // Monotonic frame counter
    std::atomic<uint32_t> write_sequence; // Lock-free synchronization counter
    char format_str[16];                 // Format string ("YUY2", "MJPG", etc.)
    uint8_t reserved[72];                // Reserved for future expansion (padding to 128 bytes)
};

static_assert(sizeof(SharedMemoryHeader) == 128, "SharedMemoryHeader must be exactly 128 bytes");

class SharedMemoryWriter {
public:
    explicit SharedMemoryWriter(std::string name);
    ~SharedMemoryWriter();

    // Initialize shared memory region with given buffer size
    bool create(size_t frame_buffer_size);

    // Write frame to shared memory with lock-free protocol
    bool writeFrame(const uint8_t* data, size_t size,
                   int width, int height,
                   const std::string& format,
                   uint64_t timestamp_ns = 0);

    // Cleanup shared memory
    void destroy();

    // Status queries
    bool isCreated() const { return shm_fd_ >= 0; }
    std::string getName() const { return shm_name_; }
    size_t getBufferSize() const { return buffer_size_; }
    uint32_t getFrameCount() const { return frame_counter_; }

private:
    SharedMemoryHeader* getHeader();

    std::string shm_name_;           // Shared memory object name
    int shm_fd_;                     // File descriptor from shm_open
    void* shm_ptr_;                  // Mapped memory pointer
    size_t buffer_size_;             // Total size (header + frame data)
    uint32_t frame_counter_;         // Frame sequence counter
};