from __future__ import annotations

import sqlite3
from pathlib import Path

from .connection import connect, resolve_db_path
from .schema import ACCOUNT_ADDITIVE_COLUMNS, SCHEMA_SQL, SCHEMA_VERSION, TRANSACTION_ADDITIVE_COLUMNS

def _existing_columns(conn: sqlite3.Connection, table: str) -> set[str]:
    return {row["name"] for row in conn.execute(f"PRAGMA table_info({table})")}


def _add_missing_columns(conn: sqlite3.Connection, table: str, columns: dict[str, str]) -> None:
    existing = _existing_columns(conn, table)
    for name, definition in columns.items():
        if name not in existing:
            conn.execute(f"ALTER TABLE {table} ADD COLUMN {name} {definition}")


def migrate_db(conn: sqlite3.Connection) -> None:
    """Apply additive, idempotent migrations only."""
    _add_missing_columns(conn, "accounts", ACCOUNT_ADDITIVE_COLUMNS)
    _add_missing_columns(conn, "transactions", TRANSACTION_ADDITIVE_COLUMNS)
    conn.execute("CREATE INDEX IF NOT EXISTS idx_transactions_datetime ON transactions(transaction_datetime)")
    conn.execute("""CREATE TABLE IF NOT EXISTS category_rules (
        id TEXT PRIMARY KEY,
        priority INTEGER NOT NULL DEFAULT 100,
        match_field TEXT NOT NULL,
        match_type TEXT NOT NULL DEFAULT 'contains',
        pattern TEXT NOT NULL,
        amount_min INTEGER,
        amount_max INTEGER,
        day_of_month INTEGER,
        transaction_type TEXT NOT NULL DEFAULT '',
        category TEXT NOT NULL,
        subcategory TEXT NOT NULL DEFAULT '',
        person TEXT NOT NULL DEFAULT '',
        is_fixed INTEGER,
        confidence REAL NOT NULL DEFAULT 1.0,
        active INTEGER NOT NULL DEFAULT 1,
        memo TEXT NOT NULL DEFAULT '',
        created_at TEXT NOT NULL,
        updated_at TEXT NOT NULL
    )""")
    _add_missing_columns(conn, "category_rules", {"amount_min": "INTEGER", "amount_max": "INTEGER", "day_of_month": "INTEGER"})
    conn.execute("CREATE INDEX IF NOT EXISTS idx_category_rules_active_priority ON category_rules(active, priority)")
    conn.execute("CREATE UNIQUE INDEX IF NOT EXISTS idx_category_rules_unique ON category_rules(match_field, match_type, pattern, transaction_type, category, subcategory, person)")
    conn.execute("""CREATE TABLE IF NOT EXISTS ledger_categories (
        id TEXT PRIMARY KEY,
        category TEXT NOT NULL,
        subcategory TEXT NOT NULL DEFAULT '',
        cashflow_kind TEXT NOT NULL DEFAULT 'expense',
        active INTEGER NOT NULL DEFAULT 1,
        sort_order INTEGER NOT NULL DEFAULT 100,
        memo TEXT NOT NULL DEFAULT '',
        created_at TEXT NOT NULL,
        updated_at TEXT NOT NULL
    )""")
    _add_missing_columns(conn, "ledger_categories", {"cashflow_kind": "TEXT NOT NULL DEFAULT 'expense'"})
    conn.execute("CREATE INDEX IF NOT EXISTS idx_ledger_categories_active_sort ON ledger_categories(active, sort_order, category, subcategory)")
    conn.execute("CREATE UNIQUE INDEX IF NOT EXISTS idx_ledger_categories_unique ON ledger_categories(category, subcategory)")
    conn.execute("""CREATE TABLE IF NOT EXISTS manual_assets (
        id TEXT PRIMARY KEY,
        name TEXT NOT NULL,
        liquidity_bucket TEXT NOT NULL DEFAULT 'other',
        valuation_amount INTEGER,
        valuation_date TEXT NOT NULL DEFAULT '',
        currency TEXT NOT NULL DEFAULT 'KRW',
        source_note TEXT NOT NULL DEFAULT '',
        memo TEXT NOT NULL DEFAULT '',
        active INTEGER NOT NULL DEFAULT 1,
        created_at TEXT NOT NULL,
        updated_at TEXT NOT NULL
    )""")
    conn.execute("CREATE INDEX IF NOT EXISTS idx_manual_assets_active_bucket ON manual_assets(active, liquidity_bucket, name)")
    conn.execute("CREATE INDEX IF NOT EXISTS idx_manual_assets_valuation_date ON manual_assets(valuation_date)")
    conn.execute("""CREATE TABLE IF NOT EXISTS asset_snapshots (
        id TEXT PRIMARY KEY,
        basis_date TEXT NOT NULL,
        source_type TEXT NOT NULL,
        source_id TEXT NOT NULL DEFAULT '',
        name TEXT NOT NULL,
        amount INTEGER,
        currency TEXT NOT NULL DEFAULT 'KRW',
        liquidity_bucket TEXT NOT NULL DEFAULT 'other',
        valuation_source TEXT NOT NULL DEFAULT '',
        source_note TEXT NOT NULL DEFAULT '',
        memo TEXT NOT NULL DEFAULT '',
        snapshot_run_id TEXT NOT NULL DEFAULT '',
        correction_of_run_id TEXT NOT NULL DEFAULT '',
        correction_reason TEXT NOT NULL DEFAULT '',
        is_correction INTEGER NOT NULL DEFAULT 0,
        closed_at TEXT NOT NULL DEFAULT '',
        created_at TEXT NOT NULL
    )""")
    _add_missing_columns(conn, "asset_snapshots", {
        "snapshot_run_id": "TEXT NOT NULL DEFAULT ''",
        "correction_of_run_id": "TEXT NOT NULL DEFAULT ''",
        "correction_reason": "TEXT NOT NULL DEFAULT ''",
        "is_correction": "INTEGER NOT NULL DEFAULT 0",
        "closed_at": "TEXT NOT NULL DEFAULT ''",
    })
    conn.execute("CREATE INDEX IF NOT EXISTS idx_asset_snapshots_basis_date ON asset_snapshots(basis_date)")
    conn.execute("CREATE INDEX IF NOT EXISTS idx_asset_snapshots_source ON asset_snapshots(source_type, source_id)")
    conn.execute("CREATE INDEX IF NOT EXISTS idx_asset_snapshots_run ON asset_snapshots(basis_date, snapshot_run_id, created_at)")
    conn.execute("INSERT OR REPLACE INTO schema_meta(key, value) VALUES ('schema_version', ?)", (SCHEMA_VERSION,))


def init_db(db_path: str | None = None) -> str:
    path = resolve_db_path(db_path)
    with connect(str(path)) as conn:
        conn.executescript(SCHEMA_SQL)
        migrate_db(conn)
    return str(path)