Initial Spatial Lab release with verified Blender bridge

spatial_lab/project.py

@@ -0,0 +1,101 @@
+"""Transactional project edits, with bounded persistent undo/redo."""
+import copy
+import json
+import os
+import tempfile
+from contextlib import contextmanager
+from pathlib import Path
+from .kernel import build, digest, dependencies
+
+def read_json(path):
+    p=Path(path)
+    if p.stat().st_size>64*1024*1024:raise ValueError('JSON input exceeds 64 MiB')
+    with p.open() as f:return json.load(f)
+
+def write_json(path,data):
+    p=Path(path);p.parent.mkdir(parents=True,exist_ok=True)
+    fd,temp=tempfile.mkstemp(prefix=p.name+'.',suffix='.tmp',dir=p.parent)
+    try:
+        with os.fdopen(fd,'w') as f:
+            json.dump(data,f,indent=2,allow_nan=False);f.write('\n');f.flush();os.fsync(f.fileno())
+        os.replace(temp,p)
+    finally:
+        if os.path.exists(temp):os.unlink(temp)
+
+class Project:
+    def __init__(self,path):
+        self.path=Path(path).resolve()
+        self.history_path=self.path.parent/'.spatial_lab'/(self.path.name+'.history.json')
+
+    def read(self):return read_json(self.path)
+    def build(self):return build(self.read())
+
+    @contextmanager
+    def _lock(self):
+        self.history_path.parent.mkdir(parents=True,exist_ok=True)
+        with self.history_path.with_suffix('.lock').open('a+b') as f:
+            if os.name=='nt':
+                import msvcrt
+                f.seek(0,2)
+                if f.tell()==0:f.write(b'0');f.flush()
+                f.seek(0);msvcrt.locking(f.fileno(),msvcrt.LK_NBLCK,1)
+            else:
+                import fcntl
+                fcntl.flock(f.fileno(),fcntl.LOCK_EX|fcntl.LOCK_NB)
+            try:yield
+            finally:
+                if os.name=='nt':f.seek(0);msvcrt.locking(f.fileno(),msvcrt.LK_UNLCK,1)
+                else:fcntl.flock(f.fileno(),fcntl.LOCK_UN)
+
+    def _history(self,current):
+        h=read_json(self.history_path) if self.history_path.exists() else {}
+        # External JSON edits or an interrupted two-file write invalidate history,
+        # never the current project. The next edit starts a new undo chain.
+        if h.get('current_hash')!=digest(current):h={'past':[],'future':[],'current_hash':digest(current)}
+        return h
+
+    def _save(self,project,history):
+        history['current_hash']=digest(project)
+        write_json(self.history_path,history);write_json(self.path,project)
+
+    def apply(self,changes):
+        if not isinstance(changes,list) or not changes:raise ValueError('An edit transaction needs a nonempty list of changes')
+        with self._lock():
+            before=self.read();after=copy.deepcopy(before);h=self._history(before)
+            for change in changes:
+                action=change.get('action')
+                if action=='set_parameter':after.setdefault('parameters',{})[change['name']]=change['value']
+                elif action=='upsert_node':
+                    node=copy.deepcopy(change['node']);ids=[n['id'] for n in after['nodes']]
+                    if node['id'] in ids:after['nodes'][ids.index(node['id'])]=node
+                    else:after['nodes'].append(node)
+                elif action=='patch_node':
+                    node=next((n for n in after['nodes'] if n['id']==change['id']),None)
+                    if node is None:raise ValueError('No such node: '+change['id'])
+                    for key,value in change['patch'].items():
+                        if key=='id':raise ValueError('Stable node IDs cannot be renamed with patch_node')
+                        if key in ['params','inputs']:node.setdefault(key,{}).update(value)
+                        else:node[key]=value
+                elif action=='remove_node':
+                    target=change['id']
+                    if target not in [n['id'] for n in after['nodes']]:raise ValueError('No such node: '+target)
+                    removing={target}
+                    while True:
+                        dependents={n['id'] for n in after['nodes'] if any(d in removing for d in dependencies(n))}-removing
+                        if dependents and not change.get('cascade',False):raise ValueError('Node is used by: '+', '.join(sorted(dependents)))
+                        if not dependents:break
+                        removing.update(dependents)
+                    after['nodes']=[n for n in after['nodes'] if n['id'] not in removing]
+                else:raise ValueError(f'Unknown edit action: {action}')
+            result=build(after)  # Failed evaluation leaves both project and history untouched.
+            if digest(before)==digest(after):return result
+            h['past']=(h['past']+[before])[-64:];h['future']=[];self._save(after,h)
+            return result
+
+    def travel(self,direction):
+        if direction not in ['undo','redo']:raise ValueError('Expected undo or redo')
+        with self._lock():
+            current=self.read();h=self._history(current);src,dst=('past','future') if direction=='undo' else ('future','past')
+            if not h[src]:raise ValueError('Nothing to '+direction+' (external edits start a new history chain)')
+            target=h[src][-1];result=build(target);h[src].pop();h[dst]=(h[dst]+[current])[-64:];self._save(target,h)
+            return result