"""Consistent logical backup of the complete current MySQL database; no DB writes."""
import gzip, hashlib, json, os, pathlib, time
import pymysql
from db_access import connect
os.umask(0o077)
root=pathlib.Path('/opt/lingniu-go-native/backups/mileage-reconciliation-20260916')
root.mkdir(parents=True,exist_ok=True)
path=root/'database.sql.gz'
if path.exists(): raise RuntimeError('Backup already exists; do not overwrite')
c=connect(); manifest={'started_at':time.strftime('%Y-%m-%dT%H:%M:%S%z'),'tables':{}}
with c.cursor() as q:
 q.execute('SELECT DATABASE() AS db'); db=q.fetchone()['db'];manifest['database']=db
 q.execute('SHOW FULL TABLES'); entries=q.fetchall()
 tables=[list(r.values())[0] for r in entries if list(r.values())[1]=='BASE TABLE']
 q.execute('SHOW TRIGGERS'); triggers=q.fetchall()
 q.execute('START TRANSACTION WITH CONSISTENT SNAPSHOT, READ ONLY')
 def literal(v):
  if isinstance(v,bytes): return '0x'+v.hex()
  return c.escape(v)
 with gzip.open(str(path)+'.partial','wt',encoding='utf-8',compresslevel=3) as f:
  f.write('SET NAMES utf8mb4;\nSET FOREIGN_KEY_CHECKS=0;\n')
  for table in tables:
   q.execute('SHOW CREATE TABLE `'+table+'`');ddl=list(q.fetchone().values())[1]
   f.write('DROP TABLE IF EXISTS `'+table+'`;\n'+ddl+';\n')
   q.execute('SHOW COLUMNS FROM `'+table+'`');cols=[r['Field'] for r in q.fetchall() if 'GENERATED' not in r['Extra']]
   names=','.join('`'+v+'`' for v in cols);count=0
   with c.cursor(pymysql.cursors.SSCursor) as stream:
    stream.execute('SELECT '+names+' FROM `'+table+'`')
    while True:
     rows=stream.fetchmany(500)
     if not rows:break
     f.write('INSERT INTO `'+table+'` ('+names+') VALUES\n'+',\n'.join('('+','.join(literal(v) for v in row)+')' for row in rows)+';\n')
     count+=len(rows)
   manifest['tables'][table]=count
   print(json.dumps({'table':table,'rows':count}),flush=True)
  for row in entries:
   if list(row.values())[1]=='VIEW':
    name=list(row.values())[0];q.execute('SHOW CREATE VIEW `'+name+'`');ddl=q.fetchone()['Create View'];f.write(ddl+';\n')
  for trigger in triggers:
   q.execute('SHOW CREATE TRIGGER `'+trigger['Trigger']+'`');ddl=q.fetchone()['SQL Original Statement'];f.write('DELIMITER ;;\n'+ddl+';;\nDELIMITER ;\n')
  f.write('SET FOREIGN_KEY_CHECKS=1;\n')
c.rollback();c.close()
os.rename(str(path)+'.partial',path)
h=hashlib.sha256()
with path.open('rb') as f:
 for block in iter(lambda:f.read(1024*1024),b''):h.update(block)
manifest.update(sha256=h.hexdigest(),bytes=path.stat().st_size,finished_at=time.strftime('%Y-%m-%dT%H:%M:%S%z'))
(root/'manifest.json').write_text(json.dumps(manifest,indent=2))
print(json.dumps({'complete':True,'bytes':manifest['bytes'],'sha256':manifest['sha256']}),flush=True)