/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import fs from 'node:fs';
import path from 'node:path';
import os from 'node:os';
import * as crypto from 'node:crypto';
import type { Config } from '../config/config.js';
import { isNodeError } from './errors.js';

export const QWEN_DIR = '.qwen';
export const GOOGLE_ACCOUNTS_FILENAME = 'google_accounts.json';

/**
 * Special characters that need to be escaped in file paths for shell compatibility.
 * Includes: spaces, parentheses, brackets, braces, semicolons, ampersands, pipes,
 * asterisks, question marks, dollar signs, backticks, quotes, hash, and other shell metacharacters.
 */
export const SHELL_SPECIAL_CHARS = /[ \t()[\]{};|*?$`'"#&<>!~]/;

/**
 * Replaces the home directory with a tilde.
 * @param path - The path to tildeify.
 * @returns The tildeified path.
 */
export function tildeifyPath(path: string): string {
  const homeDir = os.homedir();
  if (path.startsWith(homeDir)) {
    return path.replace(homeDir, '~');
  }
  return path;
}

/**
 * Shortens a path string if it exceeds maxLen, prioritizing the start and end segments.
 * Example: /path/to/a/very/long/file.txt -> /path/.../long/file.txt
 */
export function shortenPath(filePath: string, maxLen: number = 35): string {
  if (filePath.length <= maxLen) {
    return filePath;
  }

  const parsedPath = path.parse(filePath);
  const root = parsedPath.root;
  const separator = path.sep;

  // Get segments of the path *after* the root
  const relativePath = filePath.substring(root.length);
  const segments = relativePath.split(separator).filter((s) => s !== ''); // Filter out empty segments

  // Handle cases with no segments after root (e.g., "/", "C:\") or only one segment
  if (segments.length <= 1) {
    // Fall back to simple start/end truncation for very short paths or single segments
    const keepLen = Math.floor((maxLen - 3) / 2);
    // Ensure keepLen is not negative if maxLen is very small
    if (keepLen <= 0) {
      return filePath.substring(0, maxLen - 3) + '...';
    }
    const start = filePath.substring(0, keepLen);
    const end = filePath.substring(filePath.length - keepLen);
    return `${start}...${end}`;
  }

  const firstDir = segments[0];
  const lastSegment = segments[segments.length - 1];
  const startComponent = root + firstDir;

  const endPartSegments: string[] = [];
  // Base length: separator + "..." + lastDir
  let currentLength = separator.length + lastSegment.length;

  // Iterate backwards through segments (excluding the first one)
  for (let i = segments.length - 2; i >= 0; i--) {
    const segment = segments[i];
    // Length needed if we add this segment: current + separator + segment
    const lengthWithSegment = currentLength + separator.length + segment.length;

    if (lengthWithSegment <= maxLen) {
      endPartSegments.unshift(segment); // Add to the beginning of the end part
      currentLength = lengthWithSegment;
    } else {
      break;
    }
  }

  let result = endPartSegments.join(separator) + separator + lastSegment;

  if (currentLength > maxLen) {
    return result;
  }

  // Construct the final path
  result = startComponent + separator + result;

  // As a final check, if the result is somehow still too long
  // truncate the result string from the beginning, prefixing with "...".
  if (result.length > maxLen) {
    return '...' + result.substring(result.length - maxLen - 3);
  }

  return result;
}

/**
 * Calculates the relative path from a root directory to a target path.
 * Ensures both paths are resolved before calculating.
 * Returns '.' if the target path is the same as the root directory.
 *
 * @param targetPath The absolute or relative path to make relative.
 * @param rootDirectory The absolute path of the directory to make the target path relative to.
 * @returns The relative path from rootDirectory to targetPath.
 */
export function makeRelative(
  targetPath: string,
  rootDirectory: string,
): string {
  const resolvedTargetPath = path.resolve(targetPath);
  const resolvedRootDirectory = path.resolve(rootDirectory);

  const relativePath = path.relative(resolvedRootDirectory, resolvedTargetPath);

  // If the paths are the same, path.relative returns '', return '.' instead
  return relativePath || '.';
}

/**
 * Escapes special characters in a file path like macOS terminal does.
 * Escapes: spaces, parentheses, brackets, braces, semicolons, ampersands, pipes,
 * asterisks, question marks, dollar signs, backticks, quotes, hash, and other shell metacharacters.
 */
export function escapePath(filePath: string): string {
  let result = '';
  for (let i = 0; i < filePath.length; i++) {
    const char = filePath[i];

    // Count consecutive backslashes before this character
    let backslashCount = 0;
    for (let j = i - 1; j >= 0 && filePath[j] === '\\'; j--) {
      backslashCount++;
    }

    // Character is already escaped if there's an odd number of backslashes before it
    const isAlreadyEscaped = backslashCount % 2 === 1;

    // Only escape if not already escaped
    if (!isAlreadyEscaped && SHELL_SPECIAL_CHARS.test(char)) {
      result += '\\' + char;
    } else {
      result += char;
    }
  }
  return result;
}

/**
 * Unescapes special characters in a file path.
 * Removes backslash escaping from shell metacharacters.
 */
export function unescapePath(filePath: string): string {
  return filePath.replace(
    new RegExp(`\\\\([${SHELL_SPECIAL_CHARS.source.slice(1, -1)}])`, 'g'),
    '$1',
  );
}

/**
 * Generates a unique hash for a project based on its root path.
 * @param projectRoot The absolute path to the project's root directory.
 * @returns A SHA256 hash of the project root path.
 */
export function getProjectHash(projectRoot: string): string {
  return crypto.createHash('sha256').update(projectRoot).digest('hex');
}

/**
 * Checks if a path is a subpath of another path.
 * @param parentPath The parent path.
 * @param childPath The child path.
 * @returns True if childPath is a subpath of parentPath, false otherwise.
 */
export function isSubpath(parentPath: string, childPath: string): boolean {
  const isWindows = os.platform() === 'win32';
  const pathModule = isWindows ? path.win32 : path;

  // On Windows, path.relative is case-insensitive. On POSIX, it's case-sensitive.
  const relative = pathModule.relative(parentPath, childPath);

  return (
    !relative.startsWith(`..${pathModule.sep}`) &&
    relative !== '..' &&
    !pathModule.isAbsolute(relative)
  );
}

/**
 * Resolves a path with tilde (~) expansion and relative path resolution.
 * Handles tilde expansion for home directory and resolves relative paths
 * against the provided base directory or current working directory.
 *
 * @param baseDir The base directory to resolve relative paths against (defaults to current working directory)
 * @param relativePath The path to resolve (can be relative, absolute, or tilde-prefixed)
 * @returns The resolved absolute path
 */
export function resolvePath(
  baseDir: string | undefined = process.cwd(),
  relativePath: string,
): string {
  const homeDir = os.homedir();

  if (relativePath === '~') {
    return homeDir;
  } else if (relativePath.startsWith('~/')) {
    return path.join(homeDir, relativePath.slice(2));
  } else if (path.isAbsolute(relativePath)) {
    return relativePath;
  } else {
    return path.resolve(baseDir, relativePath);
  }
}

export interface PathValidationOptions {
  /**
   * If true, allows both files and directories. If false (default), only allows directories.
   */
  allowFiles?: boolean;
}

/**
 * Validates that a resolved path exists within the workspace boundaries.
 *
 * @param config The configuration object containing workspace context
 * @param resolvedPath The absolute path to validate
 * @param options Validation options
 * @throws Error if the path is outside workspace boundaries, doesn't exist, or is not a directory (when allowFiles is false)
 */
export function validatePath(
  config: Config,
  resolvedPath: string,
  options: PathValidationOptions = {},
): void {
  const { allowFiles = false } = options;
  const workspaceContext = config.getWorkspaceContext();

  if (!workspaceContext.isPathWithinWorkspace(resolvedPath)) {
    throw new Error('Path is not within workspace');
  }

  try {
    const stats = fs.statSync(resolvedPath);
    if (!allowFiles && !stats.isDirectory()) {
      throw new Error(`Path is not a directory: ${resolvedPath}`);
    }
  } catch (error: unknown) {
    if (isNodeError(error) && error.code === 'ENOENT') {
      throw new Error(`Path does not exist: ${resolvedPath}`);
    }
    throw error;
  }
}

/**
 * Resolves a path relative to the workspace root and verifies that it exists
 * within the workspace boundaries defined in the config.
 *
 * @param config The configuration object
 * @param relativePath The relative path to resolve (optional, defaults to target directory)
 * @param options Validation options (e.g., allowFiles to permit file paths)
 */
export function resolveAndValidatePath(
  config: Config,
  relativePath?: string,
  options: PathValidationOptions = {},
): string {
  const targetDir = config.getTargetDir();

  if (!relativePath) {
    return targetDir;
  }

  const resolvedPath = resolvePath(targetDir, relativePath);
  validatePath(config, resolvedPath, options);
  return resolvedPath;
}
