"""Transactional, versioned SQLite schema migrations for Magent."""

from __future__ import annotations

import sqlite3
from dataclasses import dataclass
from datetime import datetime, timezone
from typing import Callable


MigrationStep = Callable[[sqlite3.Connection], None]


@dataclass(frozen=True)
class Migration:
    version: int
    name: str
    apply: MigrationStep


def _column_names(conn: sqlite3.Connection, table: str) -> set[str]:
    return {str(row[1]) for row in conn.execute(f'PRAGMA table_info("{table}")').fetchall()}


def _add_column(conn: sqlite3.Connection, table: str, definition: str) -> None:
    column = definition.split(maxsplit=1)[0].strip('"')
    if column not in _column_names(conn, table):
        conn.execute(f'ALTER TABLE "{table}" ADD COLUMN {definition}')


def _migration_001_legacy_columns_and_indexes(conn: sqlite3.Connection) -> None:
    for definition in (
        "email TEXT",
        "last_login_at TEXT",
        "is_blocked INTEGER NOT NULL DEFAULT 0",
        "auth_provider TEXT NOT NULL DEFAULT 'local'",
        "jellyfin_password_hash TEXT",
        "last_jellyfin_auth_at TEXT",
        "jellyseerr_user_id INTEGER",
        "auto_search_enabled INTEGER NOT NULL DEFAULT 1",
        "invite_management_enabled INTEGER NOT NULL DEFAULT 0",
        "profile_id INTEGER",
        "expires_at TEXT",
        "invited_by_code TEXT",
        "invited_at TEXT",
        "auth_version INTEGER NOT NULL DEFAULT 1",
    ):
        _add_column(conn, "users", definition)

    for definition in ("recipient_email TEXT", "code_hint TEXT"):
        _add_column(conn, "signup_invites", definition)

    for definition in (
        "related_item_id INTEGER",
        "workflow_request_status TEXT",
        "workflow_media_status TEXT",
        "issue_type TEXT",
        "issue_resolved_at TEXT",
        "metadata_json TEXT",
    ):
        _add_column(conn, "portal_items", definition)

    _add_column(conn, "requests_cache", "requested_by_id INTEGER")

    statements = (
        "CREATE INDEX IF NOT EXISTS idx_portal_items_workflow ON portal_items "
        "(kind, workflow_request_status, workflow_media_status, updated_at DESC, id DESC)",
        "CREATE INDEX IF NOT EXISTS idx_portal_items_related_item ON portal_items "
        "(related_item_id, updated_at DESC, id DESC)",
        "CREATE INDEX IF NOT EXISTS idx_users_profile_id ON users (profile_id)",
        "CREATE INDEX IF NOT EXISTS idx_users_expires_at ON users (expires_at)",
        "CREATE INDEX IF NOT EXISTS idx_users_username_nocase ON users (username COLLATE NOCASE)",
        "CREATE INDEX IF NOT EXISTS idx_users_email_nocase ON users (email COLLATE NOCASE)",
        "CREATE INDEX IF NOT EXISTS idx_requests_cache_requested_by_id ON requests_cache (requested_by_id)",
        "CREATE INDEX IF NOT EXISTS idx_requests_cache_requested_by_id_created_at ON requests_cache "
        "(requested_by_id, created_at DESC, request_id DESC)",
    )
    for statement in statements:
        conn.execute(statement)


MIGRATIONS = (
    Migration(1, "legacy_columns_and_indexes", _migration_001_legacy_columns_and_indexes),
)


def run_schema_migrations(conn: sqlite3.Connection) -> list[int]:
    conn.execute(
        """
        CREATE TABLE IF NOT EXISTS schema_migrations (
            version INTEGER PRIMARY KEY,
            name TEXT NOT NULL UNIQUE,
            applied_at TEXT NOT NULL
        )
        """
    )
    applied = {int(row[0]) for row in conn.execute("SELECT version FROM schema_migrations")}
    completed: list[int] = []
    for migration in MIGRATIONS:
        if migration.version in applied:
            continue
        savepoint = f"magent_migration_{migration.version}"
        conn.execute(f"SAVEPOINT {savepoint}")
        try:
            migration.apply(conn)
            conn.execute(
                "INSERT INTO schema_migrations (version, name, applied_at) VALUES (?, ?, ?)",
                (migration.version, migration.name, datetime.now(timezone.utc).isoformat()),
            )
            conn.execute(f"RELEASE SAVEPOINT {savepoint}")
        except Exception:
            conn.execute(f"ROLLBACK TO SAVEPOINT {savepoint}")
            conn.execute(f"RELEASE SAVEPOINT {savepoint}")
            raise
        completed.append(migration.version)
    return completed