"""Synthetic JPEG marker streams and R09-shaped pins; never capture evidence.

Streams exercise the structural parser, not a decoder or visual acceptance.
Independent of all operational Root handoff documents.
"""
import hashlib
import json
import shutil
import struct

def put(path, value):
    path.write_text(json.dumps(value, sort_keys=True)+'\n')

def jpeg(width=1280, height=752, progressive=False):
    def segment(marker, body):
        return bytes((255, marker))+struct.pack('>H', len(body)+2)+body
    frame = segment(0xc2 if progressive else 0xc0,
                    b'\x08'+struct.pack('>HH', height, width)+b'\x01\x01\x11\x00')
    scan = segment(0xda, b'\x01\x01\x00\x00\x3f\x00')+b'\x12\xff\x00\x34\xff\xd0\x56'
    return b'\xff\xd8'+segment(0xe0, b'SYNTHETIC')+frame+scan+(scan if progressive else b'')+b'\xff\xd9'

def make(base, candidate):
    out, original = base/'canonical', base/'original'
    out.mkdir(); index = {'commit':candidate, 'artifacts':{}}
    measurement = {'scope':'synthetic post-collection measurement', 'images':[]}
    for role, count in (('reader',5), ('writer',64)):
        for i in range(1,count+1):
            for side in ('before','after'):
                name = f'os-pair/{role}-request-{i:04d}/screen-{side}.png'
                path = out/name; path.parent.mkdir(parents=True, exist_ok=True)
                path.write_bytes(jpeg(progressive=i%2 == 0))
                measurement['images'].append({'file':name, 'source_sha256':hashlib.sha256(path.read_bytes()).hexdigest(),
                    'width':1280,'height':752,'format_by_magic':'JPEG'})
    for name in ('runner-input.json','runner-ended.json','os-runs/writer/ended.json','os-runs/reader/ended.json'):
        path = out/name; path.parent.mkdir(parents=True,exist_ok=True); put(path, {'synthetic':True})
    refresh(out, index, measurement)
    shutil.copytree(out, original)
    def pin(name):
        p=original/name
        return {'path':str(p),'bytes':p.stat().st_size,'sha256':hashlib.sha256(p.read_bytes()).hexdigest()}
    pins = {'original_root':str(original),'native_candidate':candidate,'index':pin('index.json'),
            'runner_input':pin('runner-input.json'),'runner_ended':pin('runner-ended.json'),
            'OS':{role:{'receipt':pin('os-runs/'+role+'/ended.json')} for role in ('writer','reader')}}
    return out, original, index, measurement, pins

def refresh(out, index, measurement):
    index['artifacts'] = {p.relative_to(out).as_posix():{'bytes':p.stat().st_size,
        'sha256':hashlib.sha256(p.read_bytes()).hexdigest()} for p in out.rglob('*') if p.is_file() and p.name != 'index.json'}
    put(out/'index.json',index)
    measurement['original_index_sha256'] = hashlib.sha256((out/'index.json').read_bytes()).hexdigest()