from pathlib import Path
from types import SimpleNamespace
import pytest
from lightnest.bootstrap import Task, iterate, propose_and_validate
from lightnest.rv32 import assemble


def program(op):
    return assemble(f'lw t0, 0(a1)\nlw t1, 4(a1)\n{op} a0, t0, t1\nebreak')


def test_two_accepted_generations_inherit_actual_bytes(tmp_path):
    source = tmp_path/'source.bin'
    source.write_bytes(program('add'))
    observed = []
    class Policy:
        def propose(self, command, blob, base_offset=0):
            observed.append(blob)
            target = program('sub') if len(observed) == 1 else program('add')
            changes = [i for i,(a,b) in enumerate(zip(blob,target)) if a != b]
            assert len(changes) == 1
            i=changes[0]
            return SimpleNamespace(relative_offset=i,old_byte=blob[i],new_byte=target[i],base_offset=base_offset)
    records = iterate(Policy(), source, tmp_path/'lineage', [
        Task('subtract', (((7,2),5), ((-5,3),-8))),
        Task('add', (((7,2),9), ((-5,3),-2)))])
    assert all(x['accepted'] for x in records)
    assert records[1]['parent_sha256'] == records[0]['candidate_sha256']
    assert observed == [program('add'), program('sub')]
    assert source.read_bytes() == program('add')


def test_wrong_proposal_rejected_without_file_or_repair(tmp_path):
    source=tmp_path/'source.bin';source.write_bytes(program('add'))
    class Wrong:
        def propose(self, command, blob, base_offset=0):
            return SimpleNamespace(relative_offset=0,old_byte=blob[0],new_byte=0,base_offset=0)
    candidate=tmp_path/'candidate.bin'
    result=propose_and_validate(Wrong(),source,candidate,Task('subtract',(((7,2),5),)))
    assert not result['accepted'] and not candidate.exists()
    assert source.read_bytes()==program('add')


def test_bad_oracle_limits_rejected(tmp_path):
    with pytest.raises(ValueError):
        propose_and_validate(None,tmp_path/'missing',tmp_path/'candidate',Task('x',()))


def test_existing_audit_rejected_before_policy_or_child(tmp_path):
    source=tmp_path/'source.bin';source.write_bytes(program('add'))
    folder=tmp_path/'lineage';folder.mkdir()
    audit=folder/'generation-001.json';audit.write_text('prior audit')
    class Never:
        def propose(self,*args,**kwargs):
            pytest.fail('existing audit must reject before model call')
    with pytest.raises(FileExistsError):
        iterate(Never(),source,folder,[Task('subtract',(((7,2),5),))])
    assert audit.read_text()=='prior audit'
    assert not (folder/'generation-001.rv32').exists()