import { createHash } from "node:crypto";
import { readdir, readFile } from "node:fs/promises";
import path from "node:path";
import process from "node:process";
import { createInterface } from "node:readline";
import { fileURLToPath } from "node:url";
import pg from "pg";

const { Client } = pg;
const EXPECTED_DATABASE = "booking_test";
const TARGET_SCHEMA = "condon";
const scriptDirectory = path.dirname(fileURLToPath(import.meta.url));
const migrationsDirectory = path.resolve(scriptDirectory, "..", "migrations");

async function readStandardInput() {
  const lines = createInterface({ input: process.stdin, terminal: false });
  for await (const line of lines) {
    lines.close();
    return line.trim();
  }
  throw Object.assign(new Error("Missing connection input"), {
    code: "MISSING_CONNECTION_INPUT"
  });
}

function sanitizeError(error) {
  const errorCode = typeof error?.code === "string" ? error.code : "MIGRATION_FAILED";
  const connectionErrorCodes = new Set([
    "ECONNREFUSED",
    "ECONNRESET",
    "ENOTFOUND",
    "ETIMEDOUT"
  ]);
  return {
    ok: false,
    errorCode,
    errorMessage: connectionErrorCodes.has(errorCode)
      ? "Database connection failed"
      : typeof error?.message === "string"
      ? error.message.replace(/\s+/g, " ").slice(0, 240)
      : "Migration failed"
  };
}

async function loadMigrations() {
  const names = (await readdir(migrationsDirectory))
    .filter(name => name.endsWith(".up.sql"))
    .sort();
  if (names.length === 0) {
    throw Object.assign(new Error("No up migrations found"), {
      code: "NO_MIGRATIONS_FOUND"
    });
  }
  return Promise.all(names.map(async fileName => {
    const sql = await readFile(path.join(migrationsDirectory, fileName), "utf8");
    return {
      fileName,
      version: fileName.slice(0, -".up.sql".length),
      sql,
      checksum: createHash("sha256").update(sql).digest("hex")
    };
  }));
}

let client;
let transactionStarted = false;

try {
  const [rawInput, migrations] = await Promise.all([
    readStandardInput(),
    loadMigrations()
  ]);
  const input = JSON.parse(rawInput);

  client = new Client({
    host: input.host,
    port: input.port,
    user: input.user,
    password: input.password,
    database: input.database,
    ssl: input.ssl ? { rejectUnauthorized: false } : undefined,
    application_name: "condon_guarded_migration",
    connectionTimeoutMillis: 10_000,
    query_timeout: 60_000,
    options: "-c statement_timeout=60000 -c lock_timeout=2000"
  });

  await client.connect();
  await client.query("BEGIN");
  transactionStarted = true;

  const identityResult = await client.query(`
    SELECT
      current_database() AS database_name,
      current_user AS role_name,
      current_setting('transaction_read_only') AS transaction_read_only
  `);
  const identity = identityResult.rows[0];
  if (identity.database_name !== EXPECTED_DATABASE) {
    throw Object.assign(new Error("Unexpected database"), {
      code: "UNEXPECTED_DATABASE"
    });
  }
  if (identity.role_name !== input.user) {
    throw Object.assign(new Error("Unexpected database role"), {
      code: "UNEXPECTED_DATABASE_ROLE"
    });
  }
  if (identity.transaction_read_only !== "off") {
    throw Object.assign(new Error("Migration transaction is read-only"), {
      code: "MIGRATION_TRANSACTION_READ_ONLY"
    });
  }

  const schemaResult = await client.query(`
    SELECT EXISTS (
      SELECT 1 FROM pg_catalog.pg_namespace WHERE nspname = $1
    ) AS exists
  `, [TARGET_SCHEMA]);
  const schemaExists = schemaResult.rows[0].exists === true;
  if (schemaExists) {
    const migrationTableResult = await client.query(`
      SELECT to_regclass('condon.schema_migrations') IS NOT NULL AS exists
    `);
    if (!migrationTableResult.rows[0].exists) {
      throw Object.assign(new Error("Migration table is missing"), {
        code: "MIGRATION_TABLE_MISSING"
      });
    }
  }

  const applied = [];
  const skipped = [];
  for (const migration of migrations) {
    let existing = null;
    if (schemaExists || migration !== migrations[0]) {
      const result = await client.query(
        "SELECT checksum FROM condon.schema_migrations WHERE version = $1",
        [migration.version]
      );
      existing = result.rows[0] ?? null;
    }
    if (existing) {
      if (existing.checksum !== migration.checksum) {
        throw Object.assign(new Error(`Checksum mismatch for ${migration.version}`), {
          code: "MIGRATION_CHECKSUM_MISMATCH"
        });
      }
      skipped.push(migration.version);
      continue;
    }

    await client.query(migration.sql);
    await client.query(
      `INSERT INTO condon.schema_migrations (version, checksum) VALUES ($1, $2)`,
      [migration.version, migration.checksum]
    );
    applied.push(migration.version);
  }

  const verificationResult = await client.query(`
    SELECT
      (SELECT count(*)::integer FROM condon.room_types) AS room_type_count,
      (SELECT count(*)::integer FROM condon.owner_accounts) AS owner_account_count,
      (SELECT count(*)::integer FROM condon.entitlement_periods) AS entitlement_period_count,
      (SELECT count(*)::integer FROM condon.usage_records) AS usage_record_count,
      (SELECT count(*)::integer FROM condon.entitlement_ledger) AS ledger_count,
      (SELECT count(*)::integer FROM condon.schema_migrations) AS migration_count,
      (SELECT count(*)::integer FROM condon.bookings) AS booking_count
  `);
  const counts = verificationResult.rows[0];
  await client.query("COMMIT");
  transactionStarted = false;

  process.stdout.write(`${JSON.stringify({
    ok: true,
    databaseVerified: true,
    targetSchema: TARGET_SCHEMA,
    applied,
    skipped,
    migrations: migrations.map(migration => ({
      version: migration.version,
      checksum: migration.checksum
    })),
    counts
  }, null, 2)}\n`);
} catch (error) {
  if (client && transactionStarted) {
    try {
      await client.query("ROLLBACK");
      transactionStarted = false;
    } catch {
      // Keep the sanitized migration failure authoritative.
    }
  }
  process.stdout.write(`${JSON.stringify(sanitizeError(error), null, 2)}\n`);
  process.exitCode = 1;
} finally {
  if (client) {
    await client.end().catch(() => {
      process.exitCode = 1;
    });
  }
}