#!/usr/bin/env python3
# Standalone synthetic fixture; no user files or external network.

import copy,json,hashlib

def merge(target,patch):
    if not isinstance(patch,dict):return copy.deepcopy(patch)
    out=copy.deepcopy(target)if isinstance(target,dict)else{}
    for key,value in patch.items():
        if value is None:out.pop(key,None)
        else:out[key]=merge(out.get(key),value)
    return out
original={'title':'draft','description':'keep','tags':['review','source'],'profile':{'city':'Seoul','name':'editor'},'nullable':None}
cases=[('omitted',{'title':'revised'},{'title':'revised','description':'keep','tags':['review','source'],'profile':{'city':'Seoul','name':'editor'},'nullable':None}),('delete-null',{'description':None},{'title':'draft','tags':['review','source'],'profile':{'city':'Seoul','name':'editor'},'nullable':None}),('replace-array',{'tags':['edited']},{'title':'draft','description':'keep','tags':['edited'],'profile':{'city':'Seoul','name':'editor'},'nullable':None}),('nested-delete',{'profile':{'city':None,'lang':'ko'}},{'title':'draft','description':'keep','tags':['review','source'],'profile':{'name':'editor','lang':'ko'},'nullable':None}),('replace-root',None,None),('delete-missing',{'missing':None},original)]
before=copy.deepcopy(original);rows=[]
for name,patch,expected in cases:
    actual=merge(original,patch);assert actual==expected and original==before
    assert merge(actual,patch)==actual
    rows.append({'case':name,'patch':patch,'expected':expected,'actual':actual,'repeatSamePatchUnchanged':True})
scalar=merge('old',{'priority':1});assert scalar=={'priority':1}
result={'original':original,'cases':rows,'scalarTargetObjectPatch':scalar,'sourceUnmodified':original==before,'scope':'RFC7396-style pure value transformation. Null in object patch means delete; root null replaces whole document. No HTTP API called, no server authorization/concurrency guarantees inferred.'}

import sys,json
from datetime import datetime,timezone
result={'experiment':'json-merge-patch-semantics','executedAt':datetime.now(timezone.utc).isoformat(),'runtime':sys.version.split()[0],'synthetic':True,**result}
print(json.dumps(result,ensure_ascii=False,indent=2))