import pg from "pg";
import { AsyncLocalStorage } from "async_hooks";
import { drizzle, type NodePgDatabase } from "drizzle-orm/node-postgres";
import * as schema from "@shared/schema";

type Schema = typeof schema;

let _pool: pg.Pool | null = null;
let _globalDb: NodePgDatabase<Schema> | null = null;

type TenantCtx = { tenantDb: NodePgDatabase<Schema>; client: pg.PoolClient };

// Per-request / per-operation tenant context.
// Stores a Drizzle instance bound to a dedicated pg.PoolClient.
// The `db` proxy routes all db.* calls to that instance when a context is active.
export const _tenantCtx = new AsyncLocalStorage<TenantCtx>();

function getPool(): pg.Pool {
  if (_pool) return _pool;

  if (!process.env.DATABASE_URL) {
    const msg =
      "[DB] FATAL: DATABASE_URL is not set.\n" +
      "  Make sure your .env file (or environment) defines DATABASE_URL.\n" +
      "  Example: DATABASE_URL=postgres://user:password@host:5432/dbname";
    console.error(msg);
    throw new Error(msg);
  }

  // SSL включается для sslmode=require и Neon. rejectUnauthorized управляется
  // env DATABASE_SSL_REJECT_UNAUTHORIZED (дефолт true — проверка сертификата);
  // 'false' допустимо только с самоподписанными сертификатами (dev-стенды).
  const sslRequired =
    process.env.DATABASE_URL.includes("sslmode=require") ||
    process.env.DATABASE_URL.includes("neon.tech");
  const sslRejectUnauthorized = process.env.DATABASE_SSL_REJECT_UNAUTHORIZED !== "false";

  _pool = new pg.Pool({
    connectionString: process.env.DATABASE_URL,
    max: 50,
    idleTimeoutMillis: 30_000,
    connectionTimeoutMillis: 5_000,
    ssl: sslRequired ? { rejectUnauthorized: sslRejectUnauthorized } : undefined,
  });

  _pool.on("error", (err) => {
    let host = "<unknown>";
    try { host = new URL(process.env.DATABASE_URL!).host; } catch { /* ignore */ }
    console.error(
      `[DB] ERROR: Unexpected database connection error (host: ${host}).\n` +
        "  The app may be unable to serve requests until the database is reachable.\n" +
        `  Details: ${err.message}`
    );
  });

  setInterval(() => {
    const p = getPool();
    console.log(`[POOL] total=${p.totalCount} idle=${p.idleCount} waiting=${p.waitingCount}`);
  }, 60_000);

  const sigHandler = async () => {
    console.log("[SHUTDOWN] Draining pool...");
    if (_pool) {
      await _pool.end();
    }
    process.exit(0);
  };
  process.on("SIGTERM", sigHandler);

  return _pool;
}

export const pool: pg.Pool = new Proxy({} as pg.Pool, {
  get(_target, prop) {
    const p = getPool();
    const value = Reflect.get(p, prop, p);
    return typeof value === "function" ? value.bind(p) : value;
  },
});

// Context-aware Drizzle instance.
// When inside an openTenantCtx/openSuperAdminCtx context, routes all db.* calls
// to the dedicated client with SET SESSION already applied.
// Falls back to the shared pool otherwise.
export const db: NodePgDatabase<Schema> = new Proxy({} as NodePgDatabase<Schema>, {
  get(_target, prop) {
    const ctx = _tenantCtx.getStore();
    const target = ctx
      ? ctx.tenantDb
      : (() => {
          if (!_globalDb) _globalDb = drizzle({ client: getPool(), schema });
          return _globalDb;
        })();
    const value = Reflect.get(target, prop, target);
    return typeof value === "function" ? value.bind(target) : value;
  },
});

// Handle returned by openTenantCtx / openSuperAdminCtx.
export type CtxHandle = {
  run: (fn: () => void) => void;
  release: () => Promise<void>;
};

// Opens a dedicated client scoped to one organization using SET SESSION.
// SET SESSION (not SET LOCAL) persists the variable across transaction boundaries,
// so storage methods calling db.transaction() do not lose the RLS context.
// The client is released (with session var reset) when release() is called.
export async function openTenantCtx(organizationId: number): Promise<CtxHandle> {
  const client = await getPool().connect();
  let released = false;
  try {
    // set_config(name, value, is_local): false = session scope (survives db.transaction())
    await client.query("SELECT set_config('app.current_org_id', $1, false)", [String(organizationId)]);
    const tenantDb = drizzle({ client, schema });
    const ctx: TenantCtx = { tenantDb, client };
    return {
      run: (fn) => _tenantCtx.run(ctx, fn),
      release: async () => {
        if (released) return;
        released = true;
        try {
          await client.query("SELECT set_config('app.current_org_id', '', false)");
        } catch { /* ignore */ }
        client.release();
      },
    };
  } catch (err) {
    client.release();
    throw err;
  }
}

// Opens a dedicated client with superadmin bypass using SET SESSION.
// SET SESSION persists is_superadmin across any db.transaction() calls in storage.
export async function openSuperAdminCtx(): Promise<CtxHandle> {
  const client = await getPool().connect();
  let released = false;
  try {
    await client.query("SELECT set_config('app.is_superadmin', 'true', false)");
    const saDb = drizzle({ client, schema });
    const ctx: TenantCtx = { tenantDb: saDb, client };
    return {
      run: (fn) => _tenantCtx.run(ctx, fn),
      release: async () => {
        if (released) return;
        released = true;
        try {
          await client.query("SELECT set_config('app.is_superadmin', 'false', false)");
        } catch { /* ignore */ }
        client.release();
      },
    };
  } catch (err) {
    client.release();
    throw err;
  }
}

// Executes fn within a dedicated client scoped to one organization.
// Uses BEGIN + set_config(is_local=true) for short-lived point operations.
// Re-entrant: reuses the existing context if already inside one. Note: if called
// inside a withSuperAdmin context, the superadmin scope is reused (no narrowing).
export async function withTenant<T>(
  organizationId: number,
  fn: (tenantDb: NodePgDatabase<Schema>) => Promise<T>
): Promise<T> {
  const existing = _tenantCtx.getStore();
  if (existing) return fn(existing.tenantDb);

  const client = await getPool().connect();
  try {
    await client.query("BEGIN");
    // set_config(name, value, is_local=true): transaction-local scope, reset on ROLLBACK/COMMIT
    await client.query("SELECT set_config('app.current_org_id', $1, true)", [String(organizationId)]);
    const tenantDb = drizzle({ client, schema });
    const result = await _tenantCtx.run({ tenantDb, client }, () => fn(tenantDb));
    await client.query("COMMIT");
    return result;
  } catch (err) {
    try { await client.query("ROLLBACK"); } catch { /* ignore */ }
    throw err;
  } finally {
    client.release();
  }
}

// Executes fn with superadmin bypass for cross-tenant data access.
// Uses BEGIN + set_config(is_local=true) for short-lived point operations.
// Re-entrant: reuses the existing context if already inside one. Note: if called
// inside a withTenant context, the tenant scope is reused (no elevation).
// Always call from explicitly superadmin-only code paths.
export async function withSuperAdmin<T>(
  fn: (saDb: NodePgDatabase<Schema>) => Promise<T>
): Promise<T> {
  const existing = _tenantCtx.getStore();
  if (existing) return fn(existing.tenantDb);

  const client = await getPool().connect();
  try {
    await client.query("BEGIN");
    await client.query("SELECT set_config('app.is_superadmin', 'true', true)");
    const saDb = drizzle({ client, schema });
    const result = await _tenantCtx.run({ tenantDb: saDb, client }, () => fn(saDb));
    await client.query("COMMIT");
    return result;
  } catch (err) {
    try { await client.query("ROLLBACK"); } catch { /* ignore */ }
    throw err;
  } finally {
    client.release();
  }
}