"""
Hermes WebUI -- HTTP helper functions.
"""
import json as _json
from pathlib import Path
from api.config import IMAGE_EXTS, MD_EXTS


def require(body: dict, *fields):
    """Phase D: Validate required fields. Raises ValueError with clean message."""
    missing = [f for f in fields if not body.get(f) and body.get(f) != 0]
    if missing:
        raise ValueError(f"Missing required field(s): {', '.join(missing)}")


def bad(handler, msg, status=400):
    """Return a clean JSON error response."""
    return j(handler, {'error': msg}, status=status)


def safe_resolve(root: Path, requested: str) -> Path:
    """Resolve a relative path inside root, raising ValueError on traversal."""
    resolved = (root / requested).resolve()
    resolved.relative_to(root.resolve())  # raises ValueError if outside root
    return resolved


def j(handler, payload, status=200):
    """Send a JSON response."""
    body = _json.dumps(payload, ensure_ascii=False, indent=2).encode('utf-8')
    handler.send_response(status)
    handler.send_header('Content-Type', 'application/json; charset=utf-8')
    handler.send_header('Content-Length', str(len(body)))
    handler.send_header('Cache-Control', 'no-store')
    handler.end_headers()
    handler.wfile.write(body)


def t(handler, payload, status=200, content_type='text/plain; charset=utf-8'):
    """Send a plain text or HTML response."""
    body = payload if isinstance(payload, bytes) else str(payload).encode('utf-8')
    handler.send_response(status)
    handler.send_header('Content-Type', content_type)
    handler.send_header('Content-Length', str(len(body)))
    handler.send_header('Cache-Control', 'no-store')
    handler.end_headers()
    handler.wfile.write(body)


def read_body(handler):
    """Read and JSON-parse a POST request body."""
    length = int(handler.headers.get('Content-Length', 0))
    raw = handler.rfile.read(length) if length else b'{}'
    try:
        return _json.loads(raw)
    except Exception:
        return {}