"""
Lightweight, idempotent schema updates for SQLite.

Adds newly introduced columns to existing tables when running on an
already-initialized database. Safe to call multiple times.
"""
from typing import Dict
from sqlalchemy.engine import Engine
from sqlalchemy import text


def _existing_columns(conn, table: str) -> set[str]:
    rows = conn.execute(text(f"PRAGMA table_info('{table}')")).fetchall()
    return {row[1] for row in rows}  # name is column 2


def ensure_schema_updates(engine: Engine) -> None:
    """Ensure missing columns are added for backward-compatible updates."""
    # Map of table -> {column: SQL type}
    updates: Dict[str, Dict[str, str]] = {
        # Billing batch history (lightweight persistence)
        "billing_batches": {
            "id": "INTEGER",
            "batch_id": "TEXT",
            "status": "TEXT",
            "total_files": "INTEGER",
            "successful_files": "INTEGER",
            "failed_files": "INTEGER",
            "started_at": "DATETIME",
            "updated_at": "DATETIME",
            "completed_at": "DATETIME",
            "processing_time_seconds": "FLOAT",
            "success_rate": "FLOAT",
            "error_message": "TEXT",
        },
        "billing_batch_files": {
            "id": "INTEGER",
            "batch_id": "TEXT",
            "file_no": "TEXT",
            "status": "TEXT",
            "error_message": "TEXT",
            "filename": "TEXT",
            "size": "INTEGER",
            "started_at": "DATETIME",
            "completed_at": "DATETIME",
        },
        # Forms
        "form_index": {
            "keyword": "TEXT",
        },
        # Richer Life/Number tables (forms & pensions harmonized)
        "life_tables": {
            "le_aa": "FLOAT",
            "na_aa": "FLOAT",
            "le_am": "FLOAT",
            "na_am": "FLOAT",
            "le_af": "FLOAT",
            "na_af": "FLOAT",
            "le_wa": "FLOAT",
            "na_wa": "FLOAT",
            "le_wm": "FLOAT",
            "na_wm": "FLOAT",
            "le_wf": "FLOAT",
            "na_wf": "FLOAT",
            "le_ba": "FLOAT",
            "na_ba": "FLOAT",
            "le_bm": "FLOAT",
            "na_bm": "FLOAT",
            "le_bf": "FLOAT",
            "na_bf": "FLOAT",
            "le_ha": "FLOAT",
            "na_ha": "FLOAT",
            "le_hm": "FLOAT",
            "na_hm": "FLOAT",
            "le_hf": "FLOAT",
            "na_hf": "FLOAT",
            "table_year": "INTEGER",
            "table_type": "VARCHAR(45)",
        },
        "number_tables": {
            "month": "INTEGER",
            "na_aa": "FLOAT",
            "na_am": "FLOAT",
            "na_af": "FLOAT",
            "na_wa": "FLOAT",
            "na_wm": "FLOAT",
            "na_wf": "FLOAT",
            "na_ba": "FLOAT",
            "na_bm": "FLOAT",
            "na_bf": "FLOAT",
            "na_ha": "FLOAT",
            "na_hm": "FLOAT",
            "na_hf": "FLOAT",
            "table_type": "VARCHAR(45)",
            "description": "TEXT",
        },
        "form_list": {
            "status": "VARCHAR(45)",
        },
        # Printers: add advanced legacy fields
        "printers": {
            "number": "INTEGER",
            "page_break": "VARCHAR(50)",
            "setup_st": "VARCHAR(200)",
            "reset_st": "VARCHAR(200)",
            "b_underline": "VARCHAR(100)",
            "e_underline": "VARCHAR(100)",
            "b_bold": "VARCHAR(100)",
            "e_bold": "VARCHAR(100)",
            "phone_book": "BOOLEAN",
            "rolodex_info": "BOOLEAN",
            "envelope": "BOOLEAN",
            "file_cabinet": "BOOLEAN",
            "accounts": "BOOLEAN",
            "statements": "BOOLEAN",
            "calendar": "BOOLEAN",
        },
        # Pensions
        "pension_schedules": {
            "vests_on": "DATE",
            "vests_at": "FLOAT",
            "version": "VARCHAR(10)",
        },
        "marriage_history": {
            "married_from": "DATE",
            "married_to": "DATE",
            "married_years": "FLOAT",
            "service_from": "DATE",
            "service_to": "DATE",
            "service_years": "FLOAT",
            "marital_percent": "FLOAT",
            "version": "VARCHAR(10)",
        },
        "death_benefits": {
            "lump1": "FLOAT",
            "lump2": "FLOAT",
            "growth1": "FLOAT",
            "growth2": "FLOAT",
            "disc1": "FLOAT",
            "disc2": "FLOAT",
            "version": "VARCHAR(10)",
        },
        "separation_agreements": {
            "version": "VARCHAR(10)",
        },
        # QDROs: add explicit created_at and workflow fields if missing
        "qdros": {
            "created_at": "DATETIME",
            "approval_status": "VARCHAR(45)",
            "approved_date": "DATE",
            "filed_date": "DATE",
        },
        # Users: add approver flag
        "users": {
            "is_approver": "BOOLEAN",
        },
    }

    with engine.begin() as conn:
        for table, cols in updates.items():
            try:
                existing = _existing_columns(conn, table)
            except Exception:
                # Table may not exist yet
                continue
            for col_name, col_type in cols.items():
                if col_name not in existing:
                    try:
                        conn.execute(text(f"ALTER TABLE {table} ADD COLUMN {col_name} {col_type}"))
                    except Exception:
                        # Ignore if not applicable (other engines) or race condition
                        pass