import { Low } from "lowdb";
import { JSONFile } from "lowdb/node";
import { v4 as uuidv4 } from "uuid";
import path from "path";
import os from "os";
import fs from "fs";
// Get app name - fixed constant to avoid Windows path issues in standalone build
function getAppName() {
  return "9router";
}

// Get user data directory based on platform
function getUserDataDir() {
  const platform = process.platform;
  const homeDir = os.homedir();
  const appName = getAppName();
  
  if (platform === "win32") {
    return path.join(process.env.APPDATA || path.join(homeDir, "AppData", "Roaming"), appName);
  } else {
    // macOS & Linux: ~/.{appName}
    return path.join(homeDir, `.${appName}`);
  }
}

// Data file path - stored in user home directory
const DATA_DIR = getUserDataDir();
const DB_FILE = path.join(DATA_DIR, "db.json");

// Ensure data directory exists
if (!fs.existsSync(DATA_DIR)) {
  fs.mkdirSync(DATA_DIR, { recursive: true });
}

// Default data structure
const defaultData = {
  providerConnections: [],
  modelAliases: {},
  combos: [],
  apiKeys: [],
  settings: {
    cloudEnabled: false
  }
};

// Singleton instance
let dbInstance = null;

/**
 * Get database instance (singleton)
 */
export async function getDb() {
  if (!dbInstance) {
    const adapter = new JSONFile(DB_FILE);
    dbInstance = new Low(adapter, defaultData);
    
    // Try to read DB with error recovery for corrupt JSON
    try {
      await dbInstance.read();
    } catch (error) {
      if (error instanceof SyntaxError) {
        console.warn('[DB] Corrupt JSON detected, resetting to defaults...');
        dbInstance.data = defaultData;
        await dbInstance.write();
      } else {
        throw error;
      }
    }
    
    // Initialize with default data if empty
    if (!dbInstance.data) {
      dbInstance.data = defaultData;
      await dbInstance.write();
    }
  }
  return dbInstance;
}

// ============ Provider Connections ============

/**
 * Get all provider connections
 */
export async function getProviderConnections(filter = {}) {
  const db = await getDb();
  let connections = db.data.providerConnections || [];
  
  if (filter.provider) {
    connections = connections.filter(c => c.provider === filter.provider);
  }
  if (filter.isActive !== undefined) {
    connections = connections.filter(c => c.isActive === filter.isActive);
  }
  
  // Sort by priority (lower = higher priority)
  connections.sort((a, b) => (a.priority || 999) - (b.priority || 999));
  
  return connections;
}

/**
 * Get provider connection by ID
 */
export async function getProviderConnectionById(id) {
  const db = await getDb();
  return db.data.providerConnections.find(c => c.id === id) || null;
}

/**
 * Create or update provider connection (upsert by provider + email/name)
 */
export async function createProviderConnection(data) {
  const db = await getDb();
  const now = new Date().toISOString();
  
  // Check for existing connection with same provider and email (for OAuth)
  // or same provider and name (for API key)
  let existingIndex = -1;
  if (data.authType === "oauth" && data.email) {
    existingIndex = db.data.providerConnections.findIndex(
      c => c.provider === data.provider && c.authType === "oauth" && c.email === data.email
    );
  } else if (data.authType === "apikey" && data.name) {
    existingIndex = db.data.providerConnections.findIndex(
      c => c.provider === data.provider && c.authType === "apikey" && c.name === data.name
    );
  }
  
  // If exists, update instead of create
  if (existingIndex !== -1) {
    db.data.providerConnections[existingIndex] = {
      ...db.data.providerConnections[existingIndex],
      ...data,
      updatedAt: now,
    };
    await db.write();
    return db.data.providerConnections[existingIndex];
  }
  
  // Generate name for OAuth if not provided
  let connectionName = data.name || null;
  if (!connectionName && data.authType === "oauth") {
    if (data.email) {
      connectionName = data.email;
    } else {
      // Count existing connections for this provider to generate index
      const existingCount = db.data.providerConnections.filter(
        c => c.provider === data.provider
      ).length;
      connectionName = `Account ${existingCount + 1}`;
    }
  }

  // Auto-increment priority if not provided
  let connectionPriority = data.priority;
  if (!connectionPriority) {
    const providerConnections = db.data.providerConnections.filter(
      c => c.provider === data.provider
    );
    const maxPriority = providerConnections.reduce((max, c) => Math.max(max, c.priority || 0), 0);
    connectionPriority = maxPriority + 1;
  }
  
  // Create new connection - only save fields with actual values
  const connection = {
    id: uuidv4(),
    provider: data.provider,
    authType: data.authType || "oauth",
    name: connectionName,
    priority: connectionPriority,
    isActive: data.isActive !== undefined ? data.isActive : true,
    createdAt: now,
    updatedAt: now,
  };

  // Only add optional fields if they have values
  const optionalFields = [
    "displayName", "email", "globalPriority", "defaultModel",
    "accessToken", "refreshToken", "expiresAt", "tokenType",
    "scope", "idToken", "projectId", "apiKey", "testStatus",
    "lastTested", "lastError", "lastErrorAt", "rateLimitedUntil", "expiresIn", "errorCode"
  ];
  
  for (const field of optionalFields) {
    if (data[field] !== undefined && data[field] !== null) {
      connection[field] = data[field];
    }
  }

  // Only add providerSpecificData if it has content
  if (data.providerSpecificData && Object.keys(data.providerSpecificData).length > 0) {
    connection.providerSpecificData = data.providerSpecificData;
  }
  
  db.data.providerConnections.push(connection);
  await db.write();
  
  return connection;
}

/**
 * Update provider connection
 */
export async function updateProviderConnection(id, data) {
  const db = await getDb();
  const index = db.data.providerConnections.findIndex(c => c.id === id);
  
  if (index === -1) return null;
  
  db.data.providerConnections[index] = {
    ...db.data.providerConnections[index],
    ...data,
    updatedAt: new Date().toISOString(),
  };
  
  await db.write();
  return db.data.providerConnections[index];
}

/**
 * Delete provider connection
 */
export async function deleteProviderConnection(id) {
  const db = await getDb();
  const index = db.data.providerConnections.findIndex(c => c.id === id);
  
  if (index === -1) return false;
  
  db.data.providerConnections.splice(index, 1);
  await db.write();
  
  return true;
}

// ============ Model Aliases ============

/**
 * Get all model aliases
 */
export async function getModelAliases() {
  const db = await getDb();
  return db.data.modelAliases || {};
}

/**
 * Set model alias
 */
export async function setModelAlias(alias, model) {
  const db = await getDb();
  db.data.modelAliases[alias] = model;
  await db.write();
}

/**
 * Delete model alias
 */
export async function deleteModelAlias(alias) {
  const db = await getDb();
  delete db.data.modelAliases[alias];
  await db.write();
}

// ============ Combos ============

/**
 * Get all combos
 */
export async function getCombos() {
  const db = await getDb();
  return db.data.combos || [];
}

/**
 * Get combo by ID
 */
export async function getComboById(id) {
  const db = await getDb();
  return (db.data.combos || []).find(c => c.id === id) || null;
}

/**
 * Get combo by name
 */
export async function getComboByName(name) {
  const db = await getDb();
  return (db.data.combos || []).find(c => c.name === name) || null;
}

/**
 * Create combo
 */
export async function createCombo(data) {
  const db = await getDb();
  if (!db.data.combos) db.data.combos = [];
  
  const now = new Date().toISOString();
  const combo = {
    id: uuidv4(),
    name: data.name,
    models: data.models || [],
    createdAt: now,
    updatedAt: now,
  };
  
  db.data.combos.push(combo);
  await db.write();
  return combo;
}

/**
 * Update combo
 */
export async function updateCombo(id, data) {
  const db = await getDb();
  if (!db.data.combos) db.data.combos = [];
  
  const index = db.data.combos.findIndex(c => c.id === id);
  if (index === -1) return null;
  
  db.data.combos[index] = {
    ...db.data.combos[index],
    ...data,
    updatedAt: new Date().toISOString(),
  };
  
  await db.write();
  return db.data.combos[index];
}

/**
 * Delete combo
 */
export async function deleteCombo(id) {
  const db = await getDb();
  if (!db.data.combos) return false;
  
  const index = db.data.combos.findIndex(c => c.id === id);
  if (index === -1) return false;
  
  db.data.combos.splice(index, 1);
  await db.write();
  return true;
}

// ============ API Keys ============

/**
 * Get all API keys
 */
export async function getApiKeys() {
  const db = await getDb();
  return db.data.apiKeys || [];
}

/**
 * Generate short random key (8 chars)
 */
function generateShortKey() {
  const chars = "abcdefghijklmnopqrstuvwxyz0123456789";
  let result = "";
  for (let i = 0; i < 8; i++) {
    result += chars.charAt(Math.floor(Math.random() * chars.length));
  }
  return result;
}

/**
 * Create API key
 * @param {string} name - Key name
 * @param {string} machineId - MachineId (required)
 */
export async function createApiKey(name, machineId) {
  if (!machineId) {
    throw new Error("machineId is required");
  }
  
  const db = await getDb();
  const now = new Date().toISOString();
  
  // Always use new format: sk-{machineId}-{keyId}-{crc8}
  const { generateApiKeyWithMachine } = await import("@/shared/utils/apiKey");
  const result = generateApiKeyWithMachine(machineId);
  
  const apiKey = {
    id: uuidv4(),
    name: name,
    key: result.key,
    machineId: machineId,
    createdAt: now,
  };
  
  db.data.apiKeys.push(apiKey);
  await db.write();
  
  return apiKey;
}

/**
 * Delete API key
 */
export async function deleteApiKey(id) {
  const db = await getDb();
  const index = db.data.apiKeys.findIndex(k => k.id === id);
  
  if (index === -1) return false;
  
  db.data.apiKeys.splice(index, 1);
  await db.write();
  
  return true;
}

/**
 * Validate API key
 */
export async function validateApiKey(key) {
  const db = await getDb();
  return db.data.apiKeys.some(k => k.key === key);
}

// ============ Data Cleanup ============

/**
 * Remove null/empty fields from all provider connections to reduce db size
 */
export async function cleanupProviderConnections() {
  const db = await getDb();
  const fieldsToCheck = [
    "displayName", "email", "globalPriority", "defaultModel",
    "accessToken", "refreshToken", "expiresAt", "tokenType",
    "scope", "idToken", "projectId", "apiKey", "testStatus",
    "lastTested", "lastError", "lastErrorAt", "rateLimitedUntil", "expiresIn"
  ];

  let cleaned = 0;
  for (const connection of db.data.providerConnections) {
    for (const field of fieldsToCheck) {
      if (connection[field] === null || connection[field] === undefined) {
        delete connection[field];
        cleaned++;
      }
    }
    // Remove empty providerSpecificData
    if (connection.providerSpecificData && Object.keys(connection.providerSpecificData).length === 0) {
      delete connection.providerSpecificData;
      cleaned++;
    }
  }

  if (cleaned > 0) {
    await db.write();
  }
  return cleaned;
}

// ============ Settings ============

/**
 * Get settings
 */
export async function getSettings() {
  const db = await getDb();
  return db.data.settings || { cloudEnabled: false };
}

/**
 * Update settings
 */
export async function updateSettings(updates) {
  const db = await getDb();
  db.data.settings = {
    ...db.data.settings,
    ...updates
  };
  await db.write();
  return db.data.settings;
}

/**
 * Check if cloud is enabled
 */
export async function isCloudEnabled() {
  const settings = await getSettings();
  return settings.cloudEnabled === true;
}