"""Prepare a Blender GLB export for the configurator.

python tools/prepare_export.py path/to/edited.glb --out prepared
Produces prepared/dum.glb and prepared/scene.json. Keeps the original complete
catalogue texture library, rebinds material/node indices using loceniceId.
It does not update floor polygons, collision volumes, windows or structural design.
"""
from pathlib import Path
from copy import deepcopy
import argparse, json, struct
ROOT=Path(__file__).resolve().parent.parent

def read_glb(path):
    data=Path(path).read_bytes()
    if len(data)<28 or struct.unpack_from('<II',data)!=(0x46546c67,2):
        raise ValueError('Expected glTF 2.0 GLB')
    if struct.unpack_from('<I',data,8)[0]!=len(data):raise ValueError('GLB size mismatch')
    offset=12;g=None;b=None
    while offset<len(data):
        size,kind=struct.unpack_from('<II',data,offset)
        if offset+8+size>len(data):raise ValueError('Truncated GLB')
        chunk=data[offset+8:offset+8+size]
        if kind==0x4e4f534a:g=json.loads(chunk)
        elif kind==0x004e4942:b=chunk
        offset+=8+size
    if g is None or b is None:raise ValueError('Missing JSON or binary chunk')
    return g,b

def write_glb(path,g,b):
    j=json.dumps(g,ensure_ascii=False,separators=(',',':')).encode();j+=b' '*((-len(j))%4)
    b=bytes(b);b+=b'\0'*((-len(b))%4)
    Path(path).write_bytes(struct.pack('<IIIII',0x46546c67,2,28+len(j)+len(b),len(j),0x4e4f534a)+j+struct.pack('<II',len(b),0x004e4942)+b)

def rebind(source,edited,output,metadata=None):
    old,oldbin=read_glb(source);new,newbin=read_glb(edited);newbin=bytearray(newbin)
    if len(new.get('buffers',[]))!=1:raise ValueError('Use a single embedded GLB buffer')
    maps={}
    for plural in ['nodes','materials']:
        by_id={v.get('extras',{}).get('loceniceId'):i for i,v in enumerate(new[plural]) if v.get('extras',{}).get('loceniceId')}
        by_name={v.get('name'):i for i,v in enumerate(new[plural]) if v.get('name')}
        mapping={}
        for i,value in enumerate(old[plural]):
            key=value.get('extras',{}).get('loceniceId');index=by_id.get(key,by_name.get(value.get('name')))
            if index is not None:
                mapping[i]=index
                # Restore unsupported glTF extras lost by an editor, retain edited properties.
                new[plural][index]['extras']={**deepcopy(value.get('extras',{})),**new[plural][index].get('extras',{})}
        maps[plural]=mapping
    def node(i):
        if i not in maps['nodes']:raise ValueError(f'Missing configured object {old["nodes"][i].get("name",i)}. Preserve loceniceId, do not join variants.')
        return maps['nodes'][i]
    def material(i):
        if i not in maps['materials']:raise ValueError(f'Missing material {old["materials"][i].get("name",i)}. Do not merge material slots.')
        return maps['materials'][i]
    meta=deepcopy(metadata or old['extras'])
    h=meta['hardiePlank'];h['boardMaterial']=material(h['boardMaterial']);h['backingMaterial']=material(h['backingMaterial'])
    for key in ['boardNodes','backingNodes']:h[key]=[node(i)for i in h[key]]
    interior=meta['interiorStudy']
    for key in ['roofNodes','cutOriginalNodes']:interior[key]=[node(i)for i in interior[key]]
    interior['wallPaint']['materialIndices']=[material(i)for i in interior['wallPaint']['materialIndices']]
    if 'node'in interior.get('timberReference',{}):interior['timberReference']['node']=node(interior['timberReference']['node'])
    std=meta['allstavStandards'];std['materials']={k:[material(i)for i in v]for k,v in std['materials'].items()}
    std['triangleExcludedNode']=node(std['triangleExcludedNode'])
    for window in std['windows']:window['node']=node(window['node'])
    for value in new['nodes']:
        extras=value.get('extras',{})
        if 'windowNode'in extras:extras['windowNode']=node(extras['windowNode'])
    # The app uses a stable texture library: indices 0..31, including inactive samples.
    # Blender exports only used images; append the complete library from the source GLB.
    count=old.get('extras',{}).get('webTextureLibrarySize',32)
    for value in new.get('materials',[]):
        def shift(obj):
            if not isinstance(obj,dict):return
            for key,val in obj.items():
                if isinstance(val,dict):
                    if key.endswith('Texture')and isinstance(val.get('index'),int):val['index']+=count
                    else:shift(val)
        shift(value)
    oldsamplers=old.get('samplers',[]);sampler_offset=len(new.setdefault('samplers',[]));new['samplers']+=deepcopy(oldsamplers)
    lib=[];images={}
    for texture in old['textures'][:count]:
        src=texture['source']
        if src not in images:
            im=deepcopy(old['images'][src]);bv=old['bufferViews'][im['bufferView']]
            start=bv.get('byteOffset',0);payload=oldbin[start:start+bv['byteLength']]
            newbin+=b'\0'*((-len(newbin))%4);offset=len(newbin);newbin+=payload
            view_index=len(new.setdefault('bufferViews',[]));new['bufferViews'].append({'buffer':0,'byteOffset':offset,'byteLength':len(payload)})
            im['bufferView']=view_index;images[src]=len(new.setdefault('images',[]));new['images'].append(im)
        tex=deepcopy(texture);tex['source']=images[src]
        if 'sampler'in tex:tex['sampler']+=sampler_offset
        lib.append(tex)
    new['textures']=lib+new.get('textures',[])
    new['buffers'][0]['byteLength']=len(newbin)
    meta['webTextureLibrarySize']=count;meta['webRevision']='locenice-web-edited'
    new['extras']={**new.get('extras',{}),**meta}
    output=Path(output);output.mkdir(parents=True,exist_ok=True)
    if (output/'dum.glb').exists()or(output/'scene.json').exists():raise FileExistsError('Output already exists; choose a new directory')
    write_glb(output/'dum.glb',new,newbin)
    (output/'scene.json').write_text(json.dumps(meta,ensure_ascii=False,indent=2))
    return {'nodes':len(new['nodes']),'materials':len(new['materials']),'textures':len(new['textures']),'mappedNodes':len(maps['nodes'])}

if __name__=='__main__':
    parser=argparse.ArgumentParser(description=__doc__)
    parser.add_argument('edited',type=Path);parser.add_argument('--out',type=Path,default=Path('prepared'))
    parser.add_argument('--source',type=Path,default=ROOT/'models'/'dum.glb')
    args=parser.parse_args()
    print(rebind(args.source,args.edited,args.out))
    print('Back up the website first. Replace models/dum.glb AND data/scene.json together.')
    print('Use Three.js for exported transforms. Recheck dimensions, variants, collisions and camera presets.')