from typing import Optional


def align_records(
    cobol_records: list[dict],
    java_records: list[dict],
    key_field: str = "CUST-ID"
) -> list[tuple]:
    """Align records by key field. Returns list of (cobol, java, status)."""
    if not cobol_records and not java_records:
        return []

    cobol_by_key = {}
    for i, r in enumerate(cobol_records):
        k = r.get(key_field)
        k = _normalize_key(k)
        if k not in cobol_by_key:
            cobol_by_key[k] = []
        cobol_by_key[k].append(r)

    java_by_key = {}
    for i, r in enumerate(java_records):
        k = r.get(key_field)
        k = _normalize_key(k)
        if k not in java_by_key:
            java_by_key[k] = []
        java_by_key[k].append(r)

    pairs = []
    all_keys = set(list(cobol_by_key.keys()) + list(java_by_key.keys()))

    for key in all_keys:
        cobol_items = cobol_by_key.get(key, [])
        java_items = java_by_key.get(key, [])
        max_len = max(len(cobol_items), len(java_items))

        for i in range(max_len):
            c = cobol_items[i] if i < len(cobol_items) else None
            j = java_items[i] if i < len(java_items) else None

            if c is not None and j is not None:
                pairs.append((c, j, "MATCHED"))
            elif c is not None:
                pairs.append((c, None, "MISSING_IN_SPARK"))
            else:
                pairs.append((None, j, "EXTRA_IN_SPARK"))

    return pairs


def _normalize_key(key) -> str:
    if key is None:
        return "__NONE__"
    return str(key)