import { drizzle, type NodePgDatabase } from "drizzle-orm/node-postgres";
import { Pool, type PoolConfig } from "pg";
import { identityAdapterSchema } from "./schema.js";

export type IdentityDrizzleDatabase = NodePgDatabase<typeof identityAdapterSchema>;

export type IdentityDatabaseErrorCode = "IDENTITY_DATABASE_CONFIGURATION_INVALID";

const maximumPostgresTimeoutMs = 2_147_483_647;

/** Never carries the offending connection string, host, or underlying driver error. */
export class IdentityDatabaseError extends Error {
  readonly code: IdentityDatabaseErrorCode;

  constructor(code: IdentityDatabaseErrorCode) {
    super("Identity database configuration is invalid.");
    this.name = "IdentityDatabaseError";
    this.code = code;
    this.stack = `${this.name}: ${this.message}`;
    Object.freeze(this);
  }
}

export interface IdentityDatabaseOptions {
  readonly connectionTimeoutMs?: number;
  /** Bounds both `query_timeout` and `statement_timeout`: a hung or unexpectedly slow query on
   * the identity connection is aborted rather than holding the pool connection (and the caller)
   * indefinitely. `connectionTimeoutMs` alone only bounds establishing a connection — it does
   * nothing once a query is already running on one. */
  readonly operationTimeoutMs?: number;
}

export interface IdentityDatabaseHandle {
  readonly close: () => Promise<void>;
  readonly db: IdentityDrizzleDatabase;
}

function validateConnectionString(connectionString: string): string {
  if (connectionString.trim().length === 0) {
    throw new IdentityDatabaseError("IDENTITY_DATABASE_CONFIGURATION_INVALID");
  }
  let protocol: string;
  try {
    protocol = new URL(connectionString).protocol;
  } catch {
    throw new IdentityDatabaseError("IDENTITY_DATABASE_CONFIGURATION_INVALID");
  }
  if (protocol !== "postgres:" && protocol !== "postgresql:") {
    throw new IdentityDatabaseError("IDENTITY_DATABASE_CONFIGURATION_INVALID");
  }
  return connectionString;
}

/** Mirrors `core/src/migrations/postgres-database.ts`'s timeout validation exactly: an explicit
 * timeout must be a positive safe integer no larger than PostgreSQL's own maximum, or it is
 * rejected as invalid configuration rather than silently passed through to `pg`. */
function validateTimeout(value: unknown): number | undefined {
  if (value === undefined) {
    return undefined;
  }
  if (
    typeof value !== "number" ||
    !Number.isSafeInteger(value) ||
    value <= 0 ||
    value > maximumPostgresTimeoutMs
  ) {
    throw new IdentityDatabaseError("IDENTITY_DATABASE_CONFIGURATION_INVALID");
  }
  return value;
}

/**
 * Explicitly constructs the Core-owned Drizzle database instance used by the identity factory.
 * Building the `pg.Pool` performs no network I/O until a query is issued, and this function is
 * only ever invoked by explicit caller code — never during module import.
 */
export function createIdentityDrizzleDatabase(
  connectionString: string,
  options: IdentityDatabaseOptions = {},
): IdentityDatabaseHandle {
  const validatedConnectionString = validateConnectionString(connectionString);
  const validatedConnectionTimeoutMs = validateTimeout(options.connectionTimeoutMs);
  const validatedOperationTimeoutMs = validateTimeout(options.operationTimeoutMs);
  const poolConfig: PoolConfig = {
    connectionString: validatedConnectionString,
    ...(validatedConnectionTimeoutMs === undefined
      ? {}
      : { connectionTimeoutMillis: validatedConnectionTimeoutMs }),
    ...(validatedOperationTimeoutMs === undefined
      ? {}
      : {
          query_timeout: validatedOperationTimeoutMs,
          statement_timeout: validatedOperationTimeoutMs,
        }),
  };

  const pool = new Pool(poolConfig);
  // pg's own documentation requires an error listener on the pool: an idle client can be
  // terminated by the server (for example, its backend is killed, or the network drops) after
  // being returned to the pool, and the pool surfaces that as an 'error' event on itself rather
  // than on any in-flight query. Without a listener, that event is an unhandled Node.js error and
  // can crash the process even though no caller is doing anything wrong at the time.
  pool.on("error", () => undefined);
  const db = drizzle(pool, { schema: identityAdapterSchema });

  return Object.freeze({
    close: () => pool.end(),
    db,
  });
}

/**
 * A typed Drizzle view over an externally owned pool — for example one shared with the
 * authorization schema via `createValidatedPostgresPool` (`core/src/database/pool.ts`). Unlike
 * `createIdentityDrizzleDatabase`, this function never constructs, registers an error listener
 * on, or closes a pool itself: the caller retains that responsibility exactly once, regardless of
 * how many typed views it creates over the same pool.
 */
export function createIdentityDrizzleView(pool: Pool): IdentityDrizzleDatabase {
  return drizzle(pool, { schema: identityAdapterSchema });
}