#include "streaming_io.h"

#include <algorithm>
#include <cerrno>
#include <cstring>
#include <fcntl.h>
#include <filesystem>
#include <mutex>
#include <thread>
#include <vector>
#include <zlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

// Simplified tar parsing (USTAR format)
// For production, use libarchive or similar

namespace fs = std::filesystem;

struct TarHeader {
    char name[100];
    char mode[8];
    char uid[8];
    char gid[8];
    char size[12];
    char mtime[12];
    char checksum[8];
    char typeflag;
    char linkname[100];
    char magic[6];
    char version[2];
    char uname[32];
    char gname[32];
    char devmajor[8];
    char devminor[8];
    char prefix[155];
};

static uint64_t parse_octal(const char* str, size_t len) {
    uint64_t result = 0;
    for (size_t i = 0; i < len && str[i]; ++i) {
        if (str[i] >= '0' && str[i] <= '7') {
            result = result * 8 + (str[i] - '0');
        }
    }
    return result;
}

struct ExtractTask {
    std::string path;
    uint64_t offset;
    uint64_t size;
    uint32_t mode;
};

struct sio_extractor {
    uint32_t num_threads;
    sio_progress_cb progress_cb = nullptr;
    sio_error_cb error_cb = nullptr;
    void* user_data = nullptr;
    std::string last_error;
    std::mutex error_mutex;
    
    uint64_t bytes_extracted = 0;
    uint64_t bytes_written = 0;
    std::mutex stats_mutex;
};

sio_extractor_t* sio_create_extractor(uint32_t num_threads) {
    auto* ex = new sio_extractor_t;
    
    if (num_threads == 0) {
        num_threads = std::thread::hardware_concurrency();
        if (num_threads == 0) num_threads = 4;
        if (num_threads > 8) num_threads = 8;
    }
    
    ex->num_threads = num_threads;
    return ex;
}

void sio_destroy_extractor(sio_extractor_t* ex) {
    delete ex;
}

void sio_set_progress_cb(sio_extractor_t* ex, sio_progress_cb cb, void* user_data) {
    if (ex) {
        ex->progress_cb = cb;
        ex->user_data = user_data;
    }
}

void sio_set_error_cb(sio_extractor_t* ex, sio_error_cb cb, void* user_data) {
    if (ex) {
        ex->error_cb = cb;
        ex->user_data = user_data;
    }
}

static void set_error(sio_extractor_t* ex, const char* msg) {
    if (ex) {
        std::lock_guard<std::mutex> lock(ex->error_mutex);
        ex->last_error = msg;
    }
}

// Extract a single file from gzipped tar
static int extract_file(const char* archive_path, uint64_t offset, uint64_t size,
                        const char* dst_path, uint32_t mode, sio_extractor_t* ex) {
    // Open archive
    gzFile gz = gzopen(archive_path, "rb");
    if (!gz) {
        set_error(ex, "Failed to open archive");
        return -1;
    }
    
    // Seek to offset (gzseek is slow but necessary)
    if (gzseek(gz, offset, SEEK_SET) < 0) {
        gzclose(gz);
        set_error(ex, "Failed to seek in archive");
        return -1;
    }
    
    // Ensure destination directory exists
    fs::path dst(dst_path);
    fs::create_directories(dst.parent_path());
    
    // Open output file
    int fd = open(dst_path, O_WRONLY | O_CREAT | O_TRUNC, mode);
    if (fd < 0) {
        gzclose(gz);
        set_error(ex, "Failed to create output file");
        return -1;
    }
    
    // Extract data
    std::vector<uint8_t> buffer(64 * 1024);  // 64KB buffer
    uint64_t remaining = size;
    uint64_t extracted = 0;
    
    while (remaining > 0) {
        size_t to_read = std::min<size_t>(buffer.size(), remaining);
        int n = gzread(gz, buffer.data(), to_read);
        
        if (n <= 0) {
            close(fd);
            gzclose(gz);
            set_error(ex, "Failed to read from archive");
            return -1;
        }
        
        ssize_t written = write(fd, buffer.data(), n);
        if (written != n) {
            close(fd);
            gzclose(gz);
            set_error(ex, "Failed to write output file");
            return -1;
        }
        
        remaining -= n;
        extracted += n;
        
        // Update stats
        if (ex) {
            std::lock_guard<std::mutex> lock(ex->stats_mutex);
            ex->bytes_extracted += n;
            ex->bytes_written += written;
        }
        
        // Progress callback
        if (ex && ex->progress_cb) {
            ex->progress_cb(dst_path, extracted, size, ex->user_data);
        }
    }
    
    close(fd);
    gzclose(gz);
    
    return 0;
}

int sio_extract_tar_gz(sio_extractor_t* ex, const char* archive_path, const char* dst_dir) {
    if (!ex || !archive_path || !dst_dir) return -1;
    
    // Open archive
    gzFile gz = gzopen(archive_path, "rb");
    if (!gz) {
        set_error(ex, "Failed to open archive");
        return -1;
    }
    
    // Read and parse tar headers
    std::vector<ExtractTask> tasks;
    uint64_t offset = 0;
    
    while (true) {
        TarHeader header;
        int n = gzread(gz, &header, sizeof(TarHeader));
        if (n != sizeof(TarHeader)) {
            break;  // End of archive or error
        }
        
        // Check for empty block (end of archive)
        bool empty = true;
        for (size_t i = 0; i < sizeof(TarHeader); ++i) {
            if (reinterpret_cast<uint8_t*>(&header)[i] != 0) {
                empty = false;
                break;
            }
        }
        if (empty) {
            break;
        }
        
        // Parse header
        uint64_t file_size = parse_octal(header.size, 12);
        uint32_t mode = parse_octal(header.mode, 8);
        
        // Build full path
        std::string path;
        if (header.prefix[0]) {
            path = std::string(header.prefix) + "/" + header.name;
        } else {
            path = header.name;
        }
        
        // Skip directories and other special files for now
        if (header.typeflag == '0' || header.typeflag == '\0') {
            ExtractTask task;
            task.path = (fs::path(dst_dir) / path).string();
            task.offset = offset + sizeof(TarHeader);
            task.size = file_size;
            task.mode = mode;
            tasks.push_back(task);
        }
        
        // Skip to next header (file size rounded up to 512 bytes)
        uint64_t skip_size = (file_size + 511) & ~511;
        if (gzseek(gz, skip_size, SEEK_CUR) < 0) {
            break;
        }
        
        offset += sizeof(TarHeader) + skip_size;
    }
    
    gzclose(gz);
    
    if (tasks.empty()) {
        set_error(ex, "No files found in archive");
        return -1;
    }
    
    // Extract files (single-threaded for now - parallel extraction needs block independence)
    for (const auto& task : tasks) {
        if (extract_file(archive_path, task.offset, task.size, 
                         task.path.c_str(), task.mode, ex) != 0) {
            return -1;
        }
    }
    
    return 0;
}

const char* sio_last_error(sio_extractor_t* ex) {
    if (!ex) return nullptr;
    std::lock_guard<std::mutex> lock(ex->error_mutex);
    return ex->last_error.empty() ? nullptr : ex->last_error.c_str();
}

uint64_t sio_get_bytes_extracted(sio_extractor_t* ex) {
    if (!ex) return 0;
    std::lock_guard<std::mutex> lock(ex->stats_mutex);
    return ex->bytes_extracted;
}

uint64_t sio_get_bytes_written(sio_extractor_t* ex) {
    if (!ex) return 0;
    std::lock_guard<std::mutex> lock(ex->stats_mutex);
    return ex->bytes_written;
}