#!/usr/bin/env python3
"""
Compare two symbol JSON files produced by collect_symbols.py.

Usage: compare_symbols.py <old.json> <new.json>

Output:
  + [module] symbol  — new build adds a required symbol the old build did not have
  - [module] symbol  — new build drops a required symbol the old build had

Exit codes:
  0  — no differences
  1  — differences found
"""

import json
import sys
from pathlib import Path

old = json.loads(Path(sys.argv[1]).read_text())
new = json.loads(Path(sys.argv[2]).read_text())

all_mods = sorted(set(old) | set(new))
changes = []
for mod in all_mods:
    added   = sorted(set(new.get(mod, [])) - set(old.get(mod, [])))
    removed = sorted(set(old.get(mod, [])) - set(new.get(mod, [])))
    if added or removed:
        changes.append((mod, added, removed))

if not changes:
    print("OK: no symbol changes between stable and PR build")
    sys.exit(0)

print("Symbol changes detected (+ new requirement in PR build, - dropped by PR build):")
for mod, added, removed in changes:
    for sym in added:
        print(f"  + [{mod}] {sym}")
    for sym in removed:
        print(f"  - [{mod}] {sym}")
sys.exit(1)