from SCons.Errors import UserError

Import('env', 'arch')

if arch == 'comma_arm64':
  # Keep the caller's compiler, subprocess environment and selected sysroot.
  # Root application warning/architecture/include/library flags do not define
  # the guard ABI or its qualified artifact identity.
  roots = []
  for variable in ('CCFLAGS', 'CFLAGS', 'CPPFLAGS', 'LINKFLAGS', 'SHLINKFLAGS'):
    tokens = [str(token) for line in env.subst_list('$' + variable) for token in line]
    i = 0
    while i < len(tokens):
      token = tokens[i]
      if token == '--sysroot':
        i += 1
        if i == len(tokens) or not tokens[i] or tokens[i].startswith('-'):
          raise UserError('guard build: --sysroot requires a path')
        roots.append(tokens[i])
      elif token.startswith('--sysroot='):
        if not token[len('--sysroot='):]:
          raise UserError('guard build: --sysroot requires a path')
        roots.append(token[len('--sysroot='):])
      i += 1
  roots = list(dict.fromkeys(roots))
  if len(roots) > 1:
    raise UserError('guard build: conflicting compiler/linker sysroots')
  sysroot_flags = ['--sysroot=' + roots[0]] if roots else []
  guard_env = env.Clone()
  guard_env.Replace(
    CCFLAGS=sysroot_flags,
    CFLAGS=['-std=c11', '-O2', '-Wall', '-Wextra', '-Werror'],
    CPPFLAGS=[], CPPPATH=[], CPPDEFINES=[], LIBPATH=[], LIBS=[], RPATH=[],
    LINKFLAGS=sysroot_flags,
    # Restore the ordinary C shared-library/PIC flags even if the root extends
    # these separately. The compiler and ENV remain those of the caller.
    SHCCFLAGS=['$CCFLAGS', '-fPIC'], SHCFLAGS=['$CFLAGS'],
    SHLINKFLAGS=['$LINKFLAGS', '-shared'],
  )
  # guard-policy.json pins both libraries by SHA-256 and the tree ships them built. A device build that recompiles
  # them writes different bytes over the tracked files, and the guard then stops modeld, dmonitoringmodeld and
  # controlsd at import ("Model submission guard source/artifact changed"). Keep the shipped libraries while they
  # match the policy; rebuild only when they do not, which the guard then refuses at runtime.
  import hashlib
  import json
  import os
  here = Dir('.').srcnode().abspath
  with open(os.path.join(here, 'guard-policy.json'), 'rb') as policy_file:
    pinned = json.load(policy_file)['files']

  def shipped(name):
    path = os.path.join(here, name)
    if os.path.islink(path) or not os.path.isfile(path):
      return False
    with open(path, 'rb') as library:
      return hashlib.sha256(library.read()).hexdigest() == pinned.get(name)

  if not (shipped('libbounded_wait.so') and shipped('libusb_guards.so')):
    guard_env.SharedLibrary('bounded_wait', ['bounded_wait.c'])
    guard_env.SharedLibrary('usb_guards', ['usb_guards.c'])
  Return('guard_env')