#!/usr/bin/env python3
"""
Merge CVE data from NVD zip (original) and fkie-cad xz (GitHub release).
Creates a unified dataset using the most recent 'lastModified' timestamp.
"""
import json
import os
import re
from pathlib import Path

def merge_cves(nvd_data, fkie_data):
    """
    Merge CVE data from two sources.
    Returns merged vulnerabilities list.
    """
    # Build dictionary for NVD vulnerabilities
    nvd_vulns = nvd_data.get('vulnerabilities', [])
    nvd_dict = {}
    for v in nvd_vulns:
        cve = v.get('cve', v) if isinstance(v, dict) else {}
        cve_id = cve.get('id')
        if cve_id:
            nvd_dict[cve_id] = v

    # Build dictionary for fkie vulnerabilities
    fkie_vulns = fkie_data.get('cve_items', [])
    if not fkie_vulns:
        fkie_vulns = fkie_data.get('vulnerabilities', [])
        
    fkie_dict = {}
    for v in fkie_vulns:
        cve = v.get('cve', v) if isinstance(v, dict) else {}
        cve_id = cve.get('id')
        if cve_id:
            fkie_dict[cve_id] = v

    # Merge
    merged_dict = {}
    all_ids = set(nvd_dict.keys()) | set(fkie_dict.keys())
    
    nvd_only_count = 0
    fkie_only_count = 0
    updated_from_fkie = 0
    updated_from_nvd = 0
    identical = 0

    for cve_id in all_ids:
        in_nvd = cve_id in nvd_dict
        in_fkie = cve_id in fkie_dict

        if in_nvd and not in_fkie:
            merged_dict[cve_id] = nvd_dict[cve_id]
            nvd_only_count += 1
        elif in_fkie and not in_nvd:
            merged_dict[cve_id] = fkie_dict[cve_id]
            fkie_only_count += 1
        else:
            # Present in both, compare lastModified
            n_cve = nvd_dict[cve_id].get('cve', nvd_dict[cve_id]) if isinstance(nvd_dict[cve_id], dict) else {}
            f_cve = fkie_dict[cve_id].get('cve', fkie_dict[cve_id]) if isinstance(fkie_dict[cve_id], dict) else {}
            
            n_last = n_cve.get('lastModified', '')
            f_last = f_cve.get('lastModified', '')

            if f_last > n_last:
                merged_dict[cve_id] = fkie_dict[cve_id]
                updated_from_fkie += 1
            elif n_last > f_last:
                merged_dict[cve_id] = nvd_dict[cve_id]
                updated_from_nvd += 1
            else:
                merged_dict[cve_id] = nvd_dict[cve_id]
                identical += 1
                
    return {
        "merged_list": list(merged_dict.values()),
        "stats": {
            "total": len(merged_dict),
            "nvd_only": nvd_only_count,
            "fkie_only": fkie_only_count,
            "updated_from_fkie": updated_from_fkie,
            "updated_from_nvd": updated_from_nvd,
            "identical": identical
        }
    }

def main():
    base = Path(__file__).resolve().parent.parent / "data" / "CVE"
    nvd_dir = base / "json_from_zip"
    fkie_dir = base / "json_fkie_backup"
    out_dir = base / "json_merged"
    
    out_dir.mkdir(exist_ok=True, parents=True)
    
    pattern = re.compile(r'nvdcve-2\.0-(\d{4})\.json')
    
    # Get years from both
    nvd_years = {m.group(1) for f in nvd_dir.iterdir() if (m := pattern.match(f.name))} if nvd_dir.exists() else set()
    fkie_years = {m.group(1) for f in fkie_dir.iterdir() if (m := pattern.match(f.name))} if fkie_dir.exists() else set()
    
    all_years = sorted(nvd_years | fkie_years)
    
    print(f"Found years to process: {all_years}")
    print(f"Output directory: {out_dir}\n")
    
    total_stats = {
        "total": 0, "nvd_only": 0, "fkie_only": 0, 
        "updated_from_fkie": 0, "updated_from_nvd": 0, "identical": 0
    }
    
    for year in all_years:
        print(f"Processing year {year}...")
        nvd_file = nvd_dir / f"nvdcve-2.0-{year}.json"
        fkie_file = fkie_dir / f"nvdcve-2.0-{year}.json"
        
        nvd_data = {}
        if nvd_file.exists():
            with open(nvd_file, 'r') as f:
                nvd_data = json.load(f)
                
        fkie_data = {}
        if fkie_file.exists():
            with open(fkie_file, 'r') as f:
                fkie_data = json.load(f)
                
        # Merge logic
        result = merge_cves(nvd_data, fkie_data)
        stats = result["stats"]
        
        # Base JSON structure
        merged_json = {}
        if nvd_data:
            merged_json = nvd_data.copy()
        elif fkie_data:
            merged_json = fkie_data.copy()
            
        merged_json["vulnerabilities"] = result["merged_list"]
        merged_json["totalResults"] = len(result["merged_list"])
        
        # Update format/timestamp if needed
        if fkie_data and nvd_data:
            t_nvd = nvd_data.get('timestamp', '')
            t_fkie = fkie_data.get('timestamp', '')
            merged_json['timestamp'] = max(t_nvd, t_fkie)
            
        # Write merged file
        out_file = out_dir / f"nvdcve-2.0-{year}.json"
        with open(out_file, 'w') as f:
            json.dump(merged_json, f, separators=(',', ':'))
            
        print(f"  [DONE] Total: {stats['total']} "
              f"(NVD only: {stats['nvd_only']}, fkie only: {stats['fkie_only']}, "
              f"updated from fkie: {stats['updated_from_fkie']}, "
              f"updated from NVD: {stats['updated_from_nvd']}, "
              f"identical: {stats['identical']})")
              
        for k in total_stats:
            total_stats[k] += stats[k]
            
    print("\n" + "="*50)
    print("GLOBAL MERGE SUMMARY")
    print("="*50)
    print(f"Total CVEs processed:     {total_stats['total']}")
    print(f"Total only in NVD:        {total_stats['nvd_only']}")
    print(f"Total only in fkie:       {total_stats['fkie_only']}")
    print(f"Shared - identical:       {total_stats['identical']}")
    print(f"Shared - updated by fkie: {total_stats['updated_from_fkie']}")
    print(f"Shared - updated by NVD:  {total_stats['updated_from_nvd']}")

if __name__ == "__main__":
    main()