import fs from "node:fs";
import path from "node:path";
import Database from "better-sqlite3";

export interface DatabaseVerification {
  integrityCheck: "ok";
  foreignKeyViolations: number;
}

function resolveDatabasePath(filename: string): string {
  return path.resolve(filename);
}

export function verifyDatabaseFile(filename: string): DatabaseVerification {
  const databasePath = resolveDatabasePath(filename);
  const sqlite = new Database(databasePath, {
    readonly: true,
    fileMustExist: true,
  });

  try {
    const integrityCheck = sqlite.pragma("integrity_check", {
      simple: true,
    });
    if (integrityCheck !== "ok") {
      throw new Error(
        `SQLite integrity check failed for ${databasePath}: ${String(integrityCheck)}`
      );
    }

    const foreignKeyCheck = sqlite.pragma("foreign_key_check") as unknown[];
    const foreignKeyViolations = foreignKeyCheck.length;
    if (foreignKeyViolations > 0) {
      throw new Error(
        `SQLite foreign-key check failed for ${databasePath}: ${foreignKeyViolations} violation(s)`
      );
    }

    return {
      integrityCheck: "ok",
      foreignKeyViolations,
    };
  } finally {
    sqlite.close();
  }
}

export async function createVerifiedDatabaseBackup(
  sourceFilename: string,
  destinationFilename: string
): Promise<DatabaseVerification> {
  const sourcePath = resolveDatabasePath(sourceFilename);
  const destinationPath = resolveDatabasePath(destinationFilename);

  if (sourcePath === destinationPath) {
    throw new Error("Backup source and destination must be different files.");
  }
  if (!fs.existsSync(sourcePath)) {
    throw new Error(`Database file not found: ${sourcePath}`);
  }
  if (fs.existsSync(destinationPath)) {
    throw new Error(`Backup destination already exists: ${destinationPath}`);
  }

  fs.mkdirSync(path.dirname(destinationPath), { recursive: true });

  const source = new Database(sourcePath, {
    readonly: true,
    fileMustExist: true,
  });
  try {
    await source.backup(destinationPath);
  } finally {
    source.close();
  }

  return verifyDatabaseFile(destinationPath);
}