"""Audit ORM index/unique-key byte sizes against MySQL InnoDB prefix limits.

MySQL with the legacy 767-byte InnoDB index-prefix limit (5.6, or 5.7 with
COMPACT row format) rejects any index whose key exceeds 767 bytes — and
utf8mb4 costs 4 bytes per char, so an indexed VARCHAR key may total at most
191 chars. Modern servers (DYNAMIC row format) allow 3072 bytes = 768 chars.

Run: PYTHONPATH=. .venv/Scripts/python scripts/audit_index_key_lengths.py
"""

from __future__ import annotations

import sys

from sqlalchemy import String, UniqueConstraint

import deerflow.persistence.models  # noqa: F401  (registers all ORM models)
from deerflow.persistence.base import Base

LIMIT_OLD = 767
LIMIT_NEW = 3072
BYTES_PER_CHAR = 4  # utf8mb4


def _col_key_bytes(col) -> int | None:
    t = col.type
    # unwrap TypeDecorator
    impl = getattr(t, "impl", None)
    if impl is not None:
        t = impl
    if isinstance(t, String):
        return (t.length or 255) * BYTES_PER_CHAR
    return 8  # ints/datetimes/floats — small fixed size, close enough


def _key_bytes(col, mysql_length) -> int:
    full = _col_key_bytes(col) or 0
    if mysql_length is None:
        return full
    if isinstance(mysql_length, dict):
        prefix = mysql_length.get(col.name)
    else:
        prefix = mysql_length
    if prefix is None:
        return full
    return min(full, int(prefix) * BYTES_PER_CHAR)


def main() -> int:
    bad = 0
    for table in Base.metadata.sorted_tables:
        keys: list[tuple[str, str, list, object]] = []
        for idx in table.indexes:
            keys.append(("INDEX", idx.name, list(idx.columns), idx.dialect_options["mysql"].get("length")))
        for cons in table.constraints:
            if isinstance(cons, UniqueConstraint):
                keys.append(("UNIQUE", cons.name or "?", list(cons.columns), None))
        for kind, name, cols, mysql_length in keys:
            total = sum(_key_bytes(c, mysql_length) for c in cols)
            if total > LIMIT_OLD:
                bad += 1
                tag = "EXCEEDS 3072 (fails on ALL MySQL)" if total > LIMIT_NEW else "exceeds 767 (fails on legacy MySQL)"
                detail = ", ".join(f"{c.name}({getattr(getattr(c.type, 'impl', c.type), 'length', '?')})" for c in cols)
                print(f"{table.name}: {kind} {name} = {total} bytes [{detail}] -- {tag}")
    if not bad:
        print("OK: every index key fits within 767 bytes (utf8mb4 worst case)")
    return 0


if __name__ == "__main__":
    sys.exit(main())