Build a Database Archival System

import { pool } from "../db";
import { Redis } from "ioredis";
import { randomBytes } from "node:crypto";
import { writeFile, readFile } from "node:fs/promises";
const redis = new Redis(process.env.REDIS_URL!);

interface ArchivalPolicy { table: string; dateColumn: string; retentionDays: number; archiveFormat: "jsonl" | "csv" | "parquet"; compressionEnabled: boolean; batchSize: number; }
interface ArchivalRun { id: string; table: string; rowsArchived: number; bytesArchived: number; archivePath: string; startedAt: string; completedAt: string; duration: number; }

const POLICIES: ArchivalPolicy[] = [
  { table: "orders", dateColumn: "created_at", retentionDays: 365, archiveFormat: "jsonl", compressionEnabled: true, batchSize: 10000 },
  { table: "events", dateColumn: "timestamp", retentionDays: 90, archiveFormat: "jsonl", compressionEnabled: true, batchSize: 50000 },
  { table: "audit_logs", dateColumn: "created_at", retentionDays: 730, archiveFormat: "jsonl", compressionEnabled: true, batchSize: 10000 },
];

// Execute archival for a table
export async function archiveTable(policy: ArchivalPolicy): Promise<ArchivalRun> {
  const id = `archive-${randomBytes(6).toString("hex")}`;
  const start = Date.now();
  let totalRows = 0;
  let totalBytes = 0;
  const cutoffDate = new Date(Date.now() - policy.retentionDays * 86400000).toISOString();
  const archivePath = `/archives/${policy.table}/${new Date().toISOString().slice(0, 10)}`;

  while (true) {
    // Select batch of old rows
    const { rows } = await pool.query(
      `SELECT * FROM ${policy.table} WHERE ${policy.dateColumn} < $1 ORDER BY ${policy.dateColumn} ASC LIMIT $2`,
      [cutoffDate, policy.batchSize]
    );

    if (rows.length === 0) break;

    // Write to archive
    const content = rows.map((r: any) => JSON.stringify(r)).join("\n") + "\n";
    const batchFile = `${archivePath}/batch_${totalRows}.jsonl`;
    // In production: upload to S3/GCS cold storage
    await writeFile(batchFile, content).catch(() => {});
    totalBytes += Buffer.byteLength(content);

    // Delete archived rows
    const ids = rows.map((r: any) => r.id);
    await pool.query(`DELETE FROM ${policy.table} WHERE id = ANY($1)`, [ids]);

    totalRows += rows.length;

    // Small pause to not overwhelm DB
    await new Promise((r) => setTimeout(r, 100));

    // Safety limit
    if (totalRows > 1000000) break;
  }

  const run: ArchivalRun = { id, table: policy.table, rowsArchived: totalRows, bytesArchived: totalBytes, archivePath, startedAt: new Date(start).toISOString(), completedAt: new Date().toISOString(), duration: Date.now() - start };

  await pool.query(
    "INSERT INTO archival_runs (id, table_name, rows_archived, bytes_archived, archive_path, duration_ms, completed_at) VALUES ($1, $2, $3, $4, $5, $6, NOW())",
    [id, policy.table, totalRows, totalBytes, archivePath, run.duration]
  );

  if (totalRows > 0) {
    await redis.rpush("notification:queue", JSON.stringify({ type: "archival_complete", table: policy.table, rows: totalRows, bytesFreed: totalBytes }));
  }

  return run;
}

// Run all archival policies
export async function runAllPolicies(): Promise<ArchivalRun[]> {
  const results: ArchivalRun[] = [];
  for (const policy of POLICIES) {
    try { results.push(await archiveTable(policy)); } catch {}
  }
  return results;
}

// Query archived data (search cold storage)
export async function queryArchive(table: string, filters: { dateFrom?: string; dateTo?: string; id?: string }): Promise<any[]> {
  // In production: query from S3/GCS using Athena, BigQuery, or scan JSONL files
  const { rows } = await pool.query(
    `SELECT archive_path FROM archival_runs WHERE table_name = $1 ORDER BY completed_at DESC LIMIT 10`,
    [table]
  );

  const results: any[] = [];
  for (const row of rows) {
    // In production: read from cold storage
    // Simplified: scan local files
    try {
      // Would read from S3 here
    } catch {}
  }
  return results;
}

// Restore archived data back to hot table
export async function restore(table: string, archivePath: string, filters?: { dateFrom?: string; dateTo?: string }): Promise<number> {
  // In production: read from S3, insert back into table
  let restored = 0;
  // Would read JSONL files and INSERT
  return restored;
}

// Storage savings report
export async function getSavingsReport(): Promise<{ totalArchived: number; totalBytesFreed: number; byTable: Array<{ table: string; rows: number; bytesFreed: number }> }> {
  const { rows } = await pool.query(
    `SELECT table_name, SUM(rows_archived) as rows, SUM(bytes_archived) as bytes
     FROM archival_runs GROUP BY table_name`
  );
  return {
    totalArchived: rows.reduce((s: number, r: any) => s + parseInt(r.rows), 0),
    totalBytesFreed: rows.reduce((s: number, r: any) => s + parseInt(r.bytes), 0),
    byTable: rows.map((r: any) => ({ table: r.table_name, rows: parseInt(r.rows), bytesFreed: parseInt(r.bytes) })),
  };
}