import { prisma } from "@/lib/prisma";
import { promises as fs } from "fs";
import path from "path";
import { existsSync } from "fs";
import { createHash } from "crypto";

const MAX_BACKUPS = 10;
const BACKUP_DIR = path.join(process.cwd(), "prisma", "backups");

export interface BackupSettings {
  enabled: boolean;
  frequency: "hourly" | "daily" | "weekly" | "monthly";
  lastBackup?: string;
  nextBackup?: string;
}

const SETTINGS_FILE = path.join(
  process.cwd(),
  "prisma",
  "backup-settings.json",
);

async function ensureBackupDir() {
  if (!existsSync(BACKUP_DIR)) {
    await fs.mkdir(BACKUP_DIR, { recursive: true });
  }
}

async function loadSettings(): Promise<BackupSettings> {
  try {
    if (existsSync(SETTINGS_FILE)) {
      const content = await fs.readFile(SETTINGS_FILE, "utf-8");
      return JSON.parse(content);
    }
  } catch (error) {
    console.error("Error loading backup settings:", error);
  }
  return {
    enabled: true,
    frequency: "hourly",
  };
}

async function saveSettings(settings: BackupSettings): Promise<void> {
  await fs.writeFile(SETTINGS_FILE, JSON.stringify(settings, null, 2), "utf-8");
}

function getDatabasePath(): string {
  const dbUrl = process.env.DATABASE_URL;
  if (!dbUrl) {
    throw new Error("DATABASE_URL not set");
  }
  // Remove "file:" prefix if present
  let cleanUrl = dbUrl.replace(/^file:/, "");

  // Handle absolute paths
  if (path.isAbsolute(cleanUrl)) {
    return cleanUrl;
  }

  // Handle relative paths - normalize "./" prefix
  if (cleanUrl.startsWith("./")) {
    cleanUrl = cleanUrl.substring(2);
  }

  // Resolve relative to process.cwd()
  const resolvedPath = path.resolve(process.cwd(), cleanUrl);

  // If file doesn't exist, try common locations
  if (!existsSync(resolvedPath)) {
    // Try in prisma/ directory
    const prismaPath = path.resolve(process.cwd(), "prisma", cleanUrl);
    if (existsSync(prismaPath)) {
      return prismaPath;
    }

    // Try just the filename in prisma/
    const filename = path.basename(cleanUrl);
    const prismaFilenamePath = path.resolve(process.cwd(), "prisma", filename);
    if (existsSync(prismaFilenamePath)) {
      return prismaFilenamePath;
    }
  }

  return resolvedPath;
}

function getNextBackupDate(frequency: BackupSettings["frequency"]): Date {
  const now = new Date();
  const next = new Date(now);

  switch (frequency) {
    case "hourly":
      next.setHours(next.getHours() + 1);
      next.setMinutes(0, 0, 0);
      break;
    case "daily":
      next.setDate(next.getDate() + 1);
      next.setHours(2, 0, 0, 0); // 2 AM
      break;
    case "weekly":
      next.setDate(next.getDate() + 7);
      next.setHours(2, 0, 0, 0);
      break;
    case "monthly":
      next.setMonth(next.getMonth() + 1);
      next.setDate(1);
      next.setHours(2, 0, 0, 0);
      break;
  }

  return next;
}

async function calculateDataHash(): Promise<string> {
  // Calculate hash of actual business data (excluding Backup table)
  // We do this by querying all the data and hashing it
  const [accounts, transactions, folders, categories] = await Promise.all([
    prisma.account.findMany({ orderBy: { id: "asc" } }),
    prisma.transaction.findMany({ orderBy: { id: "asc" } }),
    prisma.folder.findMany({ orderBy: { id: "asc" } }),
    prisma.category.findMany({ orderBy: { id: "asc" } }),
  ]);

  // Create a deterministic string representation of all data
  const dataString = JSON.stringify({
    accounts: accounts.map((a) => ({
      id: a.id,
      name: a.name,
      bankId: a.bankId,
      accountNumber: a.accountNumber,
      type: a.type,
      folderId: a.folderId,
      balance: a.balance,
      currency: a.currency,
      lastImport: a.lastImport,
      externalUrl: a.externalUrl,
    })),
    transactions: transactions.map((t) => ({
      id: t.id,
      accountId: t.accountId,
      date: t.date,
      amount: t.amount,
      description: t.description,
      type: t.type,
      categoryId: t.categoryId,
      isReconciled: t.isReconciled,
      fitId: t.fitId,
      memo: t.memo,
      checkNum: t.checkNum,
    })),
    folders: folders.map((f) => ({
      id: f.id,
      name: f.name,
      parentId: f.parentId,
      color: f.color,
      icon: f.icon,
    })),
    categories: categories.map((c) => ({
      id: c.id,
      name: c.name,
      color: c.color,
      icon: c.icon,
      keywords: c.keywords,
      parentId: c.parentId,
    })),
  });

  return createHash("sha256").update(dataString).digest("hex");
}

export const backupService = {
  async createBackup(force: boolean = false): Promise<{
    id: string;
    filename: string;
    size: number;
    skipped?: boolean;
  }> {
    await ensureBackupDir();

    const dbPath = getDatabasePath();
    if (!existsSync(dbPath)) {
      throw new Error(`Database file not found: ${dbPath}`);
    }

    // Get the most recent backup first (to check if we have a dataHash stored)
    const lastBackup = await prisma.backup.findFirst({
      orderBy: { createdAt: "desc" },
    });

    // Calculate hash of actual business data (excluding Backup table)
    // This hash represents the actual data state, not the database file state
    let currentDataHash: string;
    try {
      currentDataHash = await calculateDataHash();
    } catch (error) {
      console.error("Error calculating data hash:", error);
      throw new Error("Failed to calculate data hash");
    }

    // If a backup exists and not forcing, compare data hashes
    if (!force && lastBackup && lastBackup.dataHash) {
      if (currentDataHash === lastBackup.dataHash) {
        // Update settings to reflect that backup is still current
        const settings = await loadSettings();
        settings.lastBackup = new Date().toISOString();
        settings.nextBackup = getNextBackupDate(
          settings.frequency,
        ).toISOString();
        await saveSettings(settings);

        // Return existing backup without creating a new file
        return {
          id: lastBackup.id,
          filename: lastBackup.filename,
          size: lastBackup.size,
          skipped: true,
        };
      }
    }

    // Hashes are different or no backup exists, create new backup
    const timestamp = new Date().toISOString().replace(/[:.]/g, "-");
    const filename = `backup-${timestamp}.db`;
    const backupPath = path.join(BACKUP_DIR, filename);

    // Copy database file
    await fs.copyFile(dbPath, backupPath);

    // Get file size
    const stats = await fs.stat(backupPath);
    const size = stats.size;

    // Save metadata to database (including dataHash)
    const backup = await prisma.backup.create({
      data: {
        filename,
        filePath: backupPath,
        size,
        dataHash: currentDataHash,
      },
    });

    // Update settings
    const settings = await loadSettings();
    settings.lastBackup = new Date().toISOString();
    settings.nextBackup = getNextBackupDate(settings.frequency).toISOString();
    await saveSettings(settings);

    // Rotate old backups
    await this.rotateBackups();

    return {
      id: backup.id,
      filename: backup.filename,
      size: backup.size,
    };
  },

  async rotateBackups(): Promise<void> {
    // Get all backups ordered by creation date (oldest first)
    const backups = await prisma.backup.findMany({
      orderBy: { createdAt: "asc" },
    });

    // If we have more than MAX_BACKUPS, delete the oldest ones
    if (backups.length > MAX_BACKUPS) {
      const toDelete = backups.slice(0, backups.length - MAX_BACKUPS);

      for (const backup of toDelete) {
        // Delete file
        try {
          if (existsSync(backup.filePath)) {
            await fs.unlink(backup.filePath);
          }
        } catch (error) {
          console.error(
            `Error deleting backup file ${backup.filePath}:`,
            error,
          );
        }

        // Delete metadata
        await prisma.backup.delete({
          where: { id: backup.id },
        });
      }
    }
  },

  async getAllBackups() {
    return prisma.backup.findMany({
      orderBy: { createdAt: "desc" },
    });
  },

  async getBackup(id: string) {
    return prisma.backup.findUnique({
      where: { id },
    });
  },

  async deleteBackup(id: string): Promise<void> {
    const backup = await prisma.backup.findUnique({
      where: { id },
    });

    if (!backup) {
      throw new Error("Backup not found");
    }

    // Delete file
    try {
      if (existsSync(backup.filePath)) {
        await fs.unlink(backup.filePath);
      }
    } catch (error) {
      console.error(`Error deleting backup file ${backup.filePath}:`, error);
    }

    // Delete metadata
    await prisma.backup.delete({
      where: { id },
    });
  },

  async restoreBackup(id: string): Promise<void> {
    const backup = await prisma.backup.findUnique({
      where: { id },
    });

    if (!backup) {
      throw new Error("Backup not found");
    }

    if (!existsSync(backup.filePath)) {
      throw new Error("Backup file not found");
    }

    const dbPath = getDatabasePath();

    // Create a backup of current database before restoring
    const currentBackupPath = `${dbPath}.pre-restore-${Date.now()}`;
    if (existsSync(dbPath)) {
      await fs.copyFile(dbPath, currentBackupPath);
    }

    // Restore backup
    await fs.copyFile(backup.filePath, dbPath);
  },

  async getSettings(): Promise<BackupSettings> {
    return loadSettings();
  },

  async updateSettings(
    settings: Partial<BackupSettings>,
  ): Promise<BackupSettings> {
    const current = await loadSettings();
    const updated = { ...current, ...settings };

    // Recalculate next backup if frequency changed
    if (settings.frequency && settings.frequency !== current.frequency) {
      updated.nextBackup = getNextBackupDate(settings.frequency).toISOString();
    }

    await saveSettings(updated);
    return updated;
  },

  async shouldRunAutomaticBackup(): Promise<boolean> {
    const settings = await loadSettings();

    if (!settings.enabled) {
      return false;
    }

    if (!settings.nextBackup) {
      return true; // First backup
    }

    const nextBackupDate = new Date(settings.nextBackup);
    return new Date() >= nextBackupDate;
  },
};