/**
 * @license
 * Copyright 2026 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import * as fs from 'node:fs/promises';
import * as path from 'node:path';
import * as crypto from 'node:crypto';
import { fileURLToPath } from 'node:url';
import { Storage } from '../config/storage.js';
import {
  ApprovalMode,
  type PolicyEngineConfig,
  PolicyDecision,
  type PolicyRule,
  type PolicySettings,
  type SafetyCheckerRule,
  ALWAYS_ALLOW_PRIORITY_OFFSET,
} from './types.js';
import type { PolicyEngine } from './policy-engine.js';
import { loadPoliciesFromToml, type PolicyFileError } from './toml-loader.js';
import { buildArgsPatterns, isSafeRegExp } from './utils.js';
import toml from '@iarna/toml';
import {
  MessageBusType,
  type UpdatePolicy,
} from '../confirmation-bus/types.js';
import { type MessageBus } from '../confirmation-bus/message-bus.js';
import { coreEvents } from '../utils/events.js';
import { debugLogger } from '../utils/debugLogger.js';
import { SHELL_TOOL_NAMES } from '../utils/shell-utils.js';
import {
  SHELL_TOOL_NAME,
  TOOLS_REQUIRING_NARROWING,
} from '../tools/tool-names.js';
import { isNodeError } from '../utils/errors.js';
import { MCP_TOOL_PREFIX } from '../tools/mcp-tool.js';

import { isDirectorySecure } from '../utils/security.js';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);
export const DEFAULT_CORE_POLICIES_DIR = path.join(__dirname, 'policies');

// Cache to prevent duplicate warnings in the same process
const emittedWarnings = new Set<string>();

/**
 * Emits a warning feedback event only once per process.
 */
function emitWarningOnce(message: string): void {
  if (!emittedWarnings.has(message)) {
    coreEvents.emitFeedback('warning', message);
    emittedWarnings.add(message);
  }
}

/**
 * Clears the emitted warnings cache. Used primarily for tests.
 */
export function clearEmittedPolicyWarnings(): void {
  emittedWarnings.clear();
}

// Policy tier constants for priority calculation
export const DEFAULT_POLICY_TIER = 1;
export const EXTENSION_POLICY_TIER = 2;
export const WORKSPACE_POLICY_TIER = 3;
export const USER_POLICY_TIER = 4;
export const ADMIN_POLICY_TIER = 5;

// Specific priority offsets and derived priorities for dynamic/settings rules.

export const MCP_EXCLUDED_PRIORITY = USER_POLICY_TIER + 0.9;
export const EXCLUDE_TOOLS_FLAG_PRIORITY = USER_POLICY_TIER + 0.4;
export const ALLOWED_TOOLS_FLAG_PRIORITY = USER_POLICY_TIER + 0.3;
export const TRUSTED_MCP_SERVER_PRIORITY = USER_POLICY_TIER + 0.2;
export const ALLOWED_MCP_SERVER_PRIORITY = USER_POLICY_TIER + 0.1;

// These are added to the tier base (e.g., USER_POLICY_TIER).
// Workspace tier (3) + high priority (950/1000) = ALWAYS_ALLOW_PRIORITY
export const ALWAYS_ALLOW_PRIORITY =
  WORKSPACE_POLICY_TIER + ALWAYS_ALLOW_PRIORITY_OFFSET;

/**
 * Returns the fractional priority of ALWAYS_ALLOW_PRIORITY scaled to 1000.
 */
export function getAlwaysAllowPriorityFraction(): number {
  return Math.round((ALWAYS_ALLOW_PRIORITY % 1) * 1000);
}

/**
 * Gets the list of directories to search for policy files, in order of increasing priority
 * (Default -> Extension -> Workspace -> User -> Admin).
 *
 * Note: Extension policies are loaded separately by the extension manager.
 *
 * @param defaultPoliciesDir Optional path to a directory containing default policies.
 * @param policyPaths Optional user-provided policy paths (from --policy flag).
 *   When provided, these replace the default user policies directory.
 * @param workspacePoliciesDir Optional path to a directory containing workspace policies.
 * @param adminPolicyPaths Optional admin-provided policy paths (from --admin-policy flag).
 *   When provided, these supplement the default system policies directory.
 */
export function getPolicyDirectories(
  defaultPoliciesDir?: string,
  policyPaths?: string[],
  workspacePoliciesDir?: string,
  adminPolicyPaths?: string[],
): string[] {
  return [
    // Admin tier (highest priority)
    Storage.getSystemPoliciesDir(),
    ...(adminPolicyPaths ?? []),

    // User tier (second highest priority)
    ...(policyPaths && policyPaths.length > 0
      ? policyPaths
      : [Storage.getUserPoliciesDir()]),

    // Workspace Tier (third highest)
    workspacePoliciesDir,

    // Default tier (lowest priority)
    defaultPoliciesDir ?? DEFAULT_CORE_POLICIES_DIR,
  ].filter((dir): dir is string => !!dir);
}

/**
 * Determines the policy tier (1=default, 2=extension, 3=workspace, 4=user, 5=admin) for a given directory.
 * This is used by the TOML loader to assign priority bands.
 */
export function getPolicyTier(
  dir: string,
  context: {
    defaultPoliciesDir?: string;
    workspacePoliciesDir?: string;
    adminPolicyPaths?: Set<string>;
    systemPoliciesDir: string;
    userPoliciesDir: string;
  },
): number {
  const normalizedDir = path.resolve(dir);

  if (normalizedDir === context.systemPoliciesDir) {
    return ADMIN_POLICY_TIER;
  }
  if (context.adminPolicyPaths?.has(normalizedDir)) {
    return ADMIN_POLICY_TIER;
  }
  if (normalizedDir === context.userPoliciesDir) {
    return USER_POLICY_TIER;
  }
  if (
    context.workspacePoliciesDir &&
    normalizedDir === path.resolve(context.workspacePoliciesDir)
  ) {
    return WORKSPACE_POLICY_TIER;
  }
  if (
    context.defaultPoliciesDir &&
    normalizedDir === path.resolve(context.defaultPoliciesDir)
  ) {
    return DEFAULT_POLICY_TIER;
  }
  if (normalizedDir === path.resolve(DEFAULT_CORE_POLICIES_DIR)) {
    return DEFAULT_POLICY_TIER;
  }

  return DEFAULT_POLICY_TIER;
}

/**
 * Formats a policy file error for console logging.
 */
export function formatPolicyError(error: PolicyFileError): string {
  const tierLabel = error.tier.toUpperCase();
  const severityLabel = error.severity === 'warning' ? 'warning' : 'error';
  let message = `[${tierLabel}] Policy file ${severityLabel} in ${error.fileName}:\n`;
  message += `  ${error.message}`;
  if (error.details) {
    message += `\n${error.details}`;
  }
  if (error.suggestion) {
    message += `\n  Suggestion: ${error.suggestion}`;
  }
  return message;
}

/**
 * Filters out insecure policy directories (specifically the system policy directory).
 * Supplemental admin policy paths are NOT subject to strict security checks as they
 * are explicitly provided by the user/administrator via flags or settings.
 * Emits warnings if insecure directories are found.
 */
async function filterSecurePolicyDirectories(
  dirs: string[],
  systemPoliciesDir: string,
): Promise<string[]> {
  const results = await Promise.all(
    dirs.map(async (dir) => {
      const normalizedDir = path.resolve(dir);
      const isSystemPolicy = normalizedDir === systemPoliciesDir;

      if (isSystemPolicy) {
        const { secure, reason } = await isDirectorySecure(dir);
        if (!secure) {
          const msg = `Security Warning: Skipping system policies from ${dir}: ${reason}`;
          emitWarningOnce(msg);
          return null;
        }
      }
      return dir;
    }),
  );

  return results.filter((dir): dir is string => dir !== null);
}

/**
 * Loads and sanitizes policies from an extension's policies directory.
 * Security: Filters out 'ALLOW' rules and YOLO mode configurations.
 */
export async function loadExtensionPolicies(
  extensionName: string,
  policyDir: string,
): Promise<{
  rules: PolicyRule[];
  checkers: SafetyCheckerRule[];
  errors: PolicyFileError[];
}> {
  const result = await loadPoliciesFromToml(
    [policyDir],
    () => EXTENSION_POLICY_TIER,
  );

  const rules = result.rules.filter((rule) => {
    // Security: Extensions are not allowed to automatically approve tool calls.
    if (rule.decision === PolicyDecision.ALLOW) {
      debugLogger.warn(
        `[PolicyConfig] Extension "${extensionName}" attempted to contribute an ALLOW rule for tool "${rule.toolName}". Ignoring this rule for security.`,
      );
      return false;
    }

    // Security: Extensions are not allowed to contribute YOLO mode rules.
    if (rule.modes?.includes(ApprovalMode.YOLO)) {
      debugLogger.warn(
        `[PolicyConfig] Extension "${extensionName}" attempted to contribute a rule for YOLO mode. Ignoring this rule for security.`,
      );
      return false;
    }

    // Prefix source with extension name to avoid collisions and double prefixing.
    // toml-loader.ts adds "Extension: file.toml", we transform it to "Extension (name): file.toml".
    rule.source = rule.source?.replace(
      /^Extension: /,
      `Extension (${extensionName}): `,
    );
    return true;
  });

  const checkers = result.checkers.filter((checker) => {
    // Security: Extensions are not allowed to contribute YOLO mode checkers.
    if (checker.modes?.includes(ApprovalMode.YOLO)) {
      debugLogger.warn(
        `[PolicyConfig] Extension "${extensionName}" attempted to contribute a safety checker for YOLO mode. Ignoring this checker for security.`,
      );
      return false;
    }

    // Prefix source with extension name.
    checker.source = checker.source?.replace(
      /^Extension: /,
      `Extension (${extensionName}): `,
    );
    return true;
  });

  return { rules, checkers, errors: result.errors };
}

export async function createPolicyEngineConfig(
  settings: PolicySettings,
  approvalMode: ApprovalMode,
  defaultPoliciesDir?: string,
  interactive: boolean = true,
): Promise<PolicyEngineConfig> {
  const systemPoliciesDir = path.resolve(Storage.getSystemPoliciesDir());
  const userPoliciesDir = path.resolve(Storage.getUserPoliciesDir());
  let adminPolicyPaths = settings.adminPolicyPaths;

  // Security: Ignore supplemental admin policies if the system directory already contains policies.
  // This prevents flag-based overrides when a central system policy is established.
  if (adminPolicyPaths?.length) {
    try {
      const files = await fs.readdir(systemPoliciesDir);
      if (files.some((f) => f.endsWith('.toml'))) {
        const msg = `Security Warning: Ignoring --admin-policy because system policies are already defined in ${systemPoliciesDir}`;
        emitWarningOnce(msg);
        adminPolicyPaths = undefined;
      }
    } catch (e) {
      if (!isNodeError(e) || e.code !== 'ENOENT') {
        debugLogger.warn(
          `Failed to check system policies in ${systemPoliciesDir}`,
          e,
        );
      }
    }
  }

  const policyDirs = getPolicyDirectories(
    defaultPoliciesDir,
    settings.policyPaths,
    settings.workspacePoliciesDir,
    adminPolicyPaths,
  );

  const adminPolicyPathsSet = adminPolicyPaths
    ? new Set(adminPolicyPaths.map((p) => path.resolve(p)))
    : undefined;

  const securePolicyDirs = await filterSecurePolicyDirectories(
    policyDirs,
    systemPoliciesDir,
  );

  const tierContext = {
    defaultPoliciesDir,
    workspacePoliciesDir: settings.workspacePoliciesDir,
    adminPolicyPaths: adminPolicyPathsSet,
    systemPoliciesDir,
    userPoliciesDir,
  };

  const userProvidedPaths = settings.policyPaths
    ? new Set(settings.policyPaths.map((p) => path.resolve(p)))
    : new Set<string>();

  // Load policies from TOML files
  const {
    rules: tomlRules,
    checkers: tomlCheckers,
    errors,
  } = await loadPoliciesFromToml(securePolicyDirs, (p) => {
    const normalizedPath = path.resolve(p);
    const tier = getPolicyTier(normalizedPath, tierContext);

    // If it's a user-provided path that isn't already categorized as ADMIN, treat it as USER tier.
    if (userProvidedPaths.has(normalizedPath) && tier !== ADMIN_POLICY_TIER) {
      return USER_POLICY_TIER;
    }

    return tier;
  });

  // Emit any errors encountered during TOML loading to the UI
  // coreEvents has a buffer that will display these once the UI is ready
  if (errors.length > 0) {
    for (const error of errors) {
      coreEvents.emitFeedback(
        error.severity ?? 'error',
        formatPolicyError(error),
      );
    }
  }

  const rules: PolicyRule[] = [...tomlRules];
  const checkers = [...tomlCheckers];

  // Priority system for policy rules:

  // - Higher priority numbers win over lower priority numbers
  // - When multiple rules match, the highest priority rule is applied
  // - Rules are evaluated in order of priority (highest first)
  //
  // Priority bands (tiers):
  // - Default policies (TOML): 1 + priority/1000 (e.g., priority 100 → 1.100)
  // - Extension policies (TOML): 2 + priority/1000 (e.g., priority 100 → 2.100)
  // - Workspace policies (TOML): 3 + priority/1000 (e.g., priority 100 → 3.100)
  // - User policies (TOML): 4 + priority/1000 (e.g., priority 100 → 4.100)
  // - Admin policies (TOML): 5 + priority/1000 (e.g., priority 100 → 5.100)
  //
  // This ensures Admin > User > Workspace > Extension > Default hierarchy is always preserved,
  // while allowing user-specified priorities to work within each tier.
  //
  // Settings-based and dynamic rules (mixed tiers):
  //   MCP_EXCLUDED_PRIORITY:        MCP servers excluded list (security: persistent server blocks)
  //   EXCLUDE_TOOLS_FLAG_PRIORITY:  Command line flag --exclude-tools (explicit temporary blocks)
  //   ALLOWED_TOOLS_FLAG_PRIORITY:  Command line flag --allowed-tools (explicit temporary allows)
  //   TRUSTED_MCP_SERVER_PRIORITY:  MCP servers with trust=true (persistent trusted servers)
  //   ALLOWED_MCP_SERVER_PRIORITY:  MCP servers allowed list (persistent general server allows)
  //   ALWAYS_ALLOW_PRIORITY:        Tools that the user has selected as "Always Allow" in the interactive UI
  //                                 (Workspace tier 3.x - scoped to the project)
  //
  // TOML policy priorities (before transformation):
  //   10: Write tools default to ASK_USER (becomes 1.010 in default tier)
  //   15: Auto-edit tool override (becomes 1.015 in default tier)
  //   50: Read-only tools (becomes 1.050 in default tier)
  //   60: Plan mode catch-all DENY override (becomes 1.060 in default tier)
  //   70: Plan mode explicit ALLOW override (becomes 1.070 in default tier)
  //   999: YOLO mode allow-all (becomes 1.999 in default tier)

  // MCP servers that are explicitly excluded in settings.mcp.excluded
  // Priority: MCP_EXCLUDED_PRIORITY (highest in user tier for security - persistent server blocks)
  if (settings.mcp?.excluded) {
    for (const serverName of settings.mcp.excluded) {
      rules.push({
        toolName:
          serverName === '*'
            ? `${MCP_TOOL_PREFIX}*`
            : `${MCP_TOOL_PREFIX}${serverName}_*`,
        mcpName: serverName,
        decision: PolicyDecision.DENY,
        priority: MCP_EXCLUDED_PRIORITY,
        source: 'Settings (MCP Excluded)',
      });
    }
  }

  // Tools that are explicitly excluded in the settings.
  // Priority: EXCLUDE_TOOLS_FLAG_PRIORITY (user tier - explicit temporary blocks)
  if (settings.tools?.exclude) {
    for (const tool of settings.tools.exclude) {
      rules.push({
        toolName: tool,
        decision: PolicyDecision.DENY,
        priority: EXCLUDE_TOOLS_FLAG_PRIORITY,
        source: 'Settings (Tools Excluded)',
      });
    }
  }

  // Tools that are explicitly allowed in the settings.
  // Priority: ALLOWED_TOOLS_FLAG_PRIORITY (user tier - explicit temporary allows)
  if (settings.tools?.allowed) {
    for (const tool of settings.tools.allowed) {
      // Check for legacy format: toolName(args)
      const match = tool.match(/^([a-zA-Z0-9_-]+)\((.*)\)$/);
      if (match) {
        const [, rawToolName, args] = match;
        // Normalize shell tool aliases
        const toolName = SHELL_TOOL_NAMES.includes(rawToolName)
          ? SHELL_TOOL_NAME
          : rawToolName;

        // Treat args as a command prefix for shell tool
        if (toolName === SHELL_TOOL_NAME) {
          const patterns = buildArgsPatterns(undefined, args);
          for (const pattern of patterns) {
            if (pattern) {
              rules.push({
                toolName,
                decision: PolicyDecision.ALLOW,
                priority: ALLOWED_TOOLS_FLAG_PRIORITY,
                argsPattern: new RegExp(pattern),
                source: 'Settings (Tools Allowed)',
              });
            }
          }
        } else {
          // For non-shell tools, we allow the tool itself but ignore args
          // as args matching was only supported for shell tools historically.
          rules.push({
            toolName,
            decision: PolicyDecision.ALLOW,
            priority: ALLOWED_TOOLS_FLAG_PRIORITY,
            source: 'Settings (Tools Allowed)',
          });
        }
      } else {
        // Standard tool name
        const toolName = SHELL_TOOL_NAMES.includes(tool)
          ? SHELL_TOOL_NAME
          : tool;
        rules.push({
          toolName,
          decision: PolicyDecision.ALLOW,
          priority: ALLOWED_TOOLS_FLAG_PRIORITY,
          source: 'Settings (Tools Allowed)',
        });
      }
    }
  }

  // MCP servers that are trusted in the settings.
  // Priority: TRUSTED_MCP_SERVER_PRIORITY (user tier - persistent trusted servers)
  if (settings.mcpServers) {
    for (const [serverName, serverConfig] of Object.entries(
      settings.mcpServers,
    )) {
      if (serverConfig.trust) {
        // Trust all tools from this MCP server
        // Using explicit mcpName metadata and FQN mcp_{serverName}_*
        rules.push({
          toolName: `${MCP_TOOL_PREFIX}${serverName}_*`,
          mcpName: serverName,
          decision: PolicyDecision.ALLOW,
          priority: TRUSTED_MCP_SERVER_PRIORITY,
          source: 'Settings (MCP Trusted)',
        });
      }
    }
  }

  // MCP servers that are explicitly allowed in settings.mcp.allowed
  // Priority: ALLOWED_MCP_SERVER_PRIORITY (user tier - persistent general server allows)
  if (settings.mcp?.allowed) {
    for (const serverName of settings.mcp.allowed) {
      rules.push({
        toolName:
          serverName === '*'
            ? `${MCP_TOOL_PREFIX}*`
            : `${MCP_TOOL_PREFIX}${serverName}_*`,
        mcpName: serverName,
        decision: PolicyDecision.ALLOW,
        priority: ALLOWED_MCP_SERVER_PRIORITY,
        source: 'Settings (MCP Allowed)',
      });
    }
  }

  return {
    rules,
    checkers,
    defaultDecision: interactive
      ? PolicyDecision.ASK_USER
      : PolicyDecision.DENY,
    nonInteractive: !interactive,
    approvalMode,
    disableAlwaysAllow: settings.disableAlwaysAllow,
  };
}

interface TomlRule {
  toolName?: string;
  mcpName?: string;
  decision?: string;
  priority?: number;
  commandPrefix?: string | string[];
  argsPattern?: string;
  allowRedirection?: boolean;
  // Index signature to satisfy Record type if needed for toml.stringify
  [key: string]: unknown;
}

export function createPolicyUpdater(
  policyEngine: PolicyEngine,
  messageBus: MessageBus,
  storage: Storage,
) {
  // Use a sequential queue for persistence to avoid lost updates from concurrent events.
  let persistenceQueue = Promise.resolve();

  messageBus.subscribe(
    MessageBusType.UPDATE_POLICY,
    async (message: UpdatePolicy) => {
      const toolName = message.toolName;

      if (message.commandPrefix) {
        // Convert commandPrefix(es) to argsPatterns for in-memory rules
        const patterns = buildArgsPatterns(undefined, message.commandPrefix);
        const tier =
          message.persistScope === 'user'
            ? USER_POLICY_TIER
            : WORKSPACE_POLICY_TIER;
        const priority = tier + getAlwaysAllowPriorityFraction() / 1000;

        if (TOOLS_REQUIRING_NARROWING.has(toolName) && !message.commandPrefix) {
          debugLogger.warn(
            `Attempted to update policy for sensitive tool '${toolName}' without a commandPrefix. Skipping.`,
          );
          return;
        }

        for (const pattern of patterns) {
          if (pattern) {
            // Note: patterns from buildArgsPatterns are derived from escapeRegex,
            // which is safe and won't contain ReDoS patterns.
            policyEngine.addRule({
              toolName,
              decision: PolicyDecision.ALLOW,
              priority,
              argsPattern: new RegExp(pattern),
              mcpName: message.mcpName,
              source: 'Dynamic (Confirmed)',
              allowRedirection: message.allowRedirection,
            });
          }
        }
      } else {
        if (message.argsPattern && !isSafeRegExp(message.argsPattern)) {
          coreEvents.emitFeedback(
            'error',
            `Invalid or unsafe regular expression for tool ${toolName}: ${message.argsPattern}`,
          );
          return;
        }

        const argsPattern = message.argsPattern
          ? new RegExp(message.argsPattern)
          : undefined;

        const tier =
          message.persistScope === 'user'
            ? USER_POLICY_TIER
            : WORKSPACE_POLICY_TIER;
        const priority = tier + getAlwaysAllowPriorityFraction() / 1000;

        if (TOOLS_REQUIRING_NARROWING.has(toolName) && !message.argsPattern) {
          debugLogger.warn(
            `Attempted to update policy for sensitive tool '${toolName}' without an argsPattern. Skipping.`,
          );
          return;
        }

        policyEngine.addRule({
          toolName,
          decision: PolicyDecision.ALLOW,
          priority,
          argsPattern,
          mcpName: message.mcpName,
          source: 'Dynamic (Confirmed)',
          allowRedirection: message.allowRedirection,
        });
      }

      if (message.persist) {
        persistenceQueue = persistenceQueue.then(async () => {
          try {
            const policyFile =
              message.persistScope === 'workspace'
                ? storage.getWorkspaceAutoSavedPolicyPath()
                : storage.getAutoSavedPolicyPath();
            await fs.mkdir(path.dirname(policyFile), { recursive: true });

            // Read existing file
            let existingData: { rule?: TomlRule[] } = {};
            try {
              const fileContent = await fs.readFile(policyFile, 'utf-8');
              const parsed = toml.parse(fileContent);
              if (
                typeof parsed === 'object' &&
                parsed !== null &&
                (!('rule' in parsed) || Array.isArray(parsed['rule']))
              ) {
                existingData = parsed as { rule?: TomlRule[] };
              }
            } catch (error) {
              if (!isNodeError(error) || error.code !== 'ENOENT') {
                debugLogger.warn(
                  `Failed to parse ${policyFile}, overwriting with new policy.`,
                  error,
                );
              }
            }

            // Initialize rule array if needed
            if (!existingData.rule) {
              existingData.rule = [];
            }

            // Create new rule object
            const newRule: TomlRule = {
              decision: 'allow',
              priority: getAlwaysAllowPriorityFraction(),
            };

            if (message.mcpName) {
              newRule.mcpName = message.mcpName;

              const expectedPrefix = `${MCP_TOOL_PREFIX}${message.mcpName}_`;
              if (toolName.startsWith(expectedPrefix)) {
                newRule.toolName = toolName.slice(expectedPrefix.length);
              } else {
                newRule.toolName = toolName;
              }
            } else {
              newRule.toolName = toolName;
            }

            if (message.commandPrefix) {
              newRule.commandPrefix = message.commandPrefix;
            } else if (message.argsPattern) {
              // message.argsPattern was already validated above
              newRule.argsPattern = message.argsPattern;
            }

            if (message.allowRedirection !== undefined) {
              newRule.allowRedirection = message.allowRedirection;
            }

            // Add to rules
            existingData.rule.push(newRule);

            // Serialize back to TOML
            // @iarna/toml stringify might not produce beautiful output but it handles escaping correctly
            // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
            const newContent = toml.stringify(existingData as toml.JsonMap);

            // Atomic write: write to a unique tmp file then rename to the target file.
            // Using a unique suffix avoids race conditions where concurrent processes
            // overwrite each other's temporary files, leading to ENOENT errors on rename.
            const tmpSuffix = crypto.randomBytes(8).toString('hex');
            const tmpFile = `${policyFile}.${tmpSuffix}.tmp`;

            let handle: fs.FileHandle | undefined;
            try {
              // Use 'wx' to create the file exclusively (fails if exists) for security.
              handle = await fs.open(tmpFile, 'wx');
              await handle.writeFile(newContent, 'utf-8');
            } finally {
              await handle?.close();
            }
            await fs.rename(tmpFile, policyFile);
          } catch (error) {
            coreEvents.emitFeedback(
              'error',
              `Failed to persist policy for ${toolName}`,
              error,
            );
          }
        });
      }
    },
  );
}
