"""Conservative structural screening; never grants research admission."""
import argparse
import hashlib
import json
from pathlib import Path
import re

RELATIONS = {'requires', 'enables', 'creates-context-for', 'refines', 'generalizes',
             'complements', 'alternative-to', 'conflicts-with', 'commonly-combined-with'}


def json_block(text):
    blocks = re.findall(r'```json\s*\n(.*?)\n```', text, re.S)
    if len(blocks) == 1:
        return json.loads(blocks[0])
    if blocks or '```' in text:
        raise ValueError('exactly one JSON block required')
    # Accept one unambiguous terminal JSON document without Markdown fences.
    # Never repair malformed JSON or infer data from prose.
    starts = list(re.finditer(r'(?m)^[ \t]*(?=[{\[])', text))
    if len(starts) == 1:
        return json.loads(text[starts[0].start():].strip())
    raise ValueError('exactly one JSON block or terminal document required')


def screen(candidates, relations):
    findings = []
    ids = set()
    try:
        ledger = json_block(candidates)
        if not isinstance(ledger, dict) or not isinstance(ledger.get('candidates'), list):
            raise ValueError('candidate ledger required')
        for item in ledger['candidates']:
            if not isinstance(item, dict):
                raise ValueError('candidate must be an object')
            cid = item.get('id')
            if not isinstance(cid, str) or not re.fullmatch(r'P[0-9]{2,}', cid) or cid in ids:
                raise ValueError('candidate IDs must be unique Pnn identities')
            ids.add(cid)
            uses = item.get('known_uses')
            if not isinstance(uses, list):
                raise ValueError('known_uses list required')
            for use in uses:
                if (not isinstance(use, dict) or not all(
                        isinstance(use.get(k), str) and use[k].strip()
                        for k in ('implementation', 'source_locator'))):
                    findings.append(f'{cid}: known use lacks implementation/source locator')
            recurrence = item.get('recurrence')
            if recurrence not in ('unknown', 'supported'):
                findings.append(f'{cid}: recurrence must be unknown or supported')
            if recurrence == 'supported':
                located = {(u.get('implementation'), u.get('source_locator')) for u in uses
                           if isinstance(u, dict) and isinstance(u.get('implementation'), str)
                           and isinstance(u.get('source_locator'), str) and u['source_locator'].strip()}
                if len({x[0] for x in located}) < 2:
                    findings.append(f'{cid}: recurrence lacks two located implementations')
    except (ValueError, TypeError) as exc:
        findings.append(f'candidate contract: {exc}')
    try:
        edges = json_block(relations)
        if not isinstance(edges, list):
            raise ValueError('relation array required')
        for edge in edges:
            if not isinstance(edge, dict):
                raise ValueError('relation must be an object')
            for field in ('subject_candidate_id', 'object_candidate_id'):
                endpoint = edge.get(field)
                if not isinstance(endpoint, str) or endpoint not in ids:
                    findings.append(f'invalid {field}: {endpoint!r}; must resolve to candidate ledger')
            if edge.get('relation') not in RELATIONS:
                findings.append('invalid relation type')
            for field in ('rationale', 'source_claim_and_locator', 'counterexample'):
                if not isinstance(edge.get(field), str) or not edge[field].strip():
                    findings.append(f'relation missing {field}')
            if edge.get('observation_versus_hypothesis') not in ('observation', 'hypothesis'):
                findings.append('relation missing observation/hypothesis classification')
    except (ValueError, TypeError) as exc:
        findings.append(f'relation contract: {exc}')
    return {'structural_status': 'blocked' if findings else 'passed',
            'admission': 'not_granted', 'semantic_review': 'required', 'findings': findings}


def audit(root):
    root = Path(root)
    paths = [root / 'artifacts/generated' / name for name in
             ('candidates.md', 'relation-proposals.md')]
    result = screen(*(p.read_text() for p in paths))
    result['artifact_sha256'] = {str(p.relative_to(root)): hashlib.sha256(p.read_bytes()).hexdigest()
                                 for p in paths}
    return result


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('root', type=Path)
    args = parser.parse_args()
    try:
        result = audit(args.root)
    except (OSError, ValueError) as exc:
        parser.exit(1, f'{exc}\n')
    print(json.dumps(result, indent=2))
    raise SystemExit(0 if result['structural_status'] == 'passed' else 1)