// Import required modules
import { Client } from "@db/postgres";
import { load } from "@std/dotenv";
import { crypto } from "@std/crypto";

// Load environment variables from .env file or system environment
const env = await load();

// Validate required environment variables
for (const key of ["DB_USER", "DB_PASSWORD", "DB_NAME", "ANONYMIZATION_KEY"]) {
  if (!env[key]) {
    console.error(`Missing ${key} in .env or environment variables`);
    Deno.exit(1);
  }
}

// Adjust based on database capacity
const BATCH_SIZE = parseInt(env.BATCH_SIZE) || 10;
// Maximum number of invoices to process per user
// Skip user if exceeded (likely the case for streaming payments e.g.)
const MAX_INVOICES = parseInt(env.MAX_INVOICES) || 21000;

// Database connection configuration from .env or environment variables
const dbConfig = {
  user: env.DB_USER,
  password: env.DB_PASSWORD,
  database: env.DB_NAME,
  hostname: env.DB_HOST || "localhost",
  port: parseInt(env.DB_PORT || "5432", 10),
};

const client = new Client(dbConfig);

// Connect to the database
try {
  await client.connect();
  console.log(`Connected to database`);
} catch {
  console.log(`Failed to connect to database`);
  Deno.exit(1);
}

// Fetch all user IDs
const userIdsResult = await client.queryObject("SELECT id FROM users");
const userIds = userIdsResult.rows.map((row) => row.id);

// CSV file path
const csvFilePath = "./daily-stats.csv";

// CSV headers
const csvHeaders = [
  "User ID", // HMAC-SHA256 hash (truncated to 12 hex chars)
  "Date",
  "Balance Start of Day",
  "Balance End of Day",
  "Balance Max Day",
  "Balance Min Day",
  "Total Flow Out",
  "Total Flow In",
];

// Write headers to CSV (create file or overwrite if it exists)
await Deno.writeTextFile(csvFilePath, csvHeaders.join(",") + "\n");

// Function to compute HMAC-SHA256 hash of user_id, truncated to 48 bits (12 hex chars)
async function anonymizeUserId(userId) {
  const keyData = new TextEncoder().encode(env.ANONYMIZATION_KEY);
  const data = new TextEncoder().encode(userId.toString());
  const key = await crypto.subtle.importKey(
    "raw",
    keyData,
    { name: "HMAC", hash: "SHA-256" },
    false,
    ["sign"]
  );
  const signature = await crypto.subtle.sign("HMAC", key, data);
  const hashArray = Array.from(new Uint8Array(signature).slice(0, 6)); // Take first 6 bytes (48 bits)
  return hashArray.map((b) => b.toString(16).padStart(2, "0")).join("");
}

// Function to process a single user and return CSV rows
async function processUser(userId, client) {
  // Check the number of settled invoices for the user
  const countResult = await client.queryObject(
    `SELECT COUNT(*) AS count
     FROM invoices
     WHERE user_id = $1 AND settled_at IS NOT NULL`,
    [userId]
  );
  const invoiceCount = Number(countResult.rows[0].count);

  if (invoiceCount > MAX_INVOICES) {
    const anonymizedUserId = await anonymizeUserId(userId);
    console.warn(`Skipping user ${anonymizedUserId}: ${invoiceCount} invoices exceed limit of ${MAX_INVOICES}`);
    return [];
  }

  // Fetch settled invoices for the user
  const invoicesResult = await client.queryObject(
    `SELECT settled_at, amount, type, service_fee, routing_fee
     FROM invoices
     WHERE user_id = $1 AND settled_at IS NOT NULL
     ORDER BY settled_at ASC`,
    [userId]
  );
  const invoices = invoicesResult.rows;

  if (invoices.length === 0) return [];

  // Aggregate daily statistics using BigInt
  const dailyData = {};
  let runningBalance = BigInt(0); // Initialize as BigInt

  for (const invoice of invoices) {
    const day = invoice.settled_at.toISOString().split("T")[0]; // YYYY-MM-DD
    // Convert amounts to BigInt, handling NULL fees
    const amount = BigInt(invoice.amount);
    const serviceFee = invoice.service_fee ? BigInt(invoice.service_fee) : BigInt(0);
    const routingFee = invoice.routing_fee ? BigInt(invoice.routing_fee) : BigInt(0);

    // Calculate effective amount: include fees for outgoing, not for incoming
    const effectiveAmount = invoice.type === "incoming"
      ? amount
      : amount + serviceFee + routingFee; // Add fees for outgoing
    const signedAmount = invoice.type === "incoming" ? effectiveAmount : -effectiveAmount;

    if (!dailyData[day]) {
      dailyData[day] = {
        balance_start_of_day: runningBalance,
        balance_end_of_day: runningBalance,
        balance_max_day: runningBalance,
        balance_min_day: runningBalance,
        total_flow_in: BigInt(0),
        total_flow_out: BigInt(0),
      };
    }

    // Update running balance
    runningBalance += signedAmount;
    dailyData[day].balance_end_of_day = runningBalance;

    // Update min/max balance
    dailyData[day].balance_max_day = runningBalance > dailyData[day].balance_max_day
      ? runningBalance
      : dailyData[day].balance_max_day;
    dailyData[day].balance_min_day = runningBalance < dailyData[day].balance_min_day
      ? runningBalance
      : dailyData[day].balance_min_day;

    // Update flows
    if (signedAmount > 0) {
      dailyData[day].total_flow_in += signedAmount;
    } else {
      dailyData[day].total_flow_out += -signedAmount; // Positive outflow value
    }
  }

  // Generate CSV rows for this user with anonymized user_id
  const anonymizedUserId = await anonymizeUserId(userId);
  const rows = [];
  for (const [day, stats] of Object.entries(dailyData)) {
    rows.push([
      anonymizedUserId,
      day,
      stats.balance_start_of_day.toString(),
      stats.balance_end_of_day.toString(),
      stats.balance_max_day.toString(),
      stats.balance_min_day.toString(),
      stats.total_flow_out.toString(),
      stats.total_flow_in.toString(),
    ].join(","));
  }

  return rows;
}

// Process users in parallel with batching
async function processUsersInParallel(userIds) {
  for (let i = 0; i < userIds.length; i += BATCH_SIZE) {
    const batch = userIds.slice(i, i + BATCH_SIZE);
    console.log(`Processing batch ${i / BATCH_SIZE + 1} of ${Math.ceil(userIds.length / BATCH_SIZE)}`);

    // Process users in parallel and collect rows
    const promises = batch.map(async (userId) => {
      const batchClient = new Client(dbConfig); // Use shared dbConfig
      await batchClient.connect();
      try {
        return await processUser(userId, batchClient);
      } finally {
        await batchClient.end();
      }
    });

    // Wait for all users in the batch to complete
    const batchRows = (await Promise.all(promises)).flat();

    // Write all rows for the batch to CSV in one operation
    if (batchRows.length > 0) {
      await Deno.writeTextFile(csvFilePath, batchRows.join("\n") + "\n", { append: true });
    }
  }
}

// Run parallel processing
await processUsersInParallel(userIds);

// Close the main database connection
await client.end();

console.log("Daily statistics written to", csvFilePath);