import * as plugins from './plugins.js';
import type {
  ISshConfigFile,
  ISshConfigHost,
  ISshConfigOptions,
  ISshConfigReadResult,
} from './types.js';

export class SshConfig {
  public readonly homeDir: string;
  public readonly mainConfigPath: string;

  constructor(options: ISshConfigOptions = {}) {
    this.homeDir = options.homeDir ?? plugins.os.homedir();
    this.mainConfigPath = this.expandHome(options.mainConfigPath ?? plugins.path.join(this.homeDir, '.ssh', 'config'));
  }

  public async read(): Promise<ISshConfigReadResult> {
    const files: ISshConfigFile[] = [];
    const hosts: ISshConfigHost[] = [];
    const visitedFiles = new Set<string>();
    await this.readFileRecursive(this.mainConfigPath, visitedFiles, files, hosts, true);
    return {
      mainConfigPath: this.mainConfigPath,
      files,
      hosts,
    };
  }

  public async getHost(alias: string): Promise<ISshConfigHost | undefined> {
    const result = await this.read();
    return result.hosts.find((host) => host.patterns.includes(alias));
  }

  public getDisplayHosts(result: ISshConfigReadResult): ISshConfigHost[] {
    return result.hosts.filter((host) => host.patterns.some((pattern) => !this.patternHasWildcard(pattern)));
  }

  public getFirstOption(host: ISshConfigHost, optionName: string): string | undefined {
    return host.options[optionName.toLowerCase()]?.[0];
  }

  public expandHome(filePath: string): string {
    if (filePath === '~') {
      return this.homeDir;
    }
    if (filePath.startsWith('~/')) {
      return plugins.path.join(this.homeDir, filePath.slice(2));
    }
    return filePath;
  }

  private async readFileRecursive(
    filePath: string,
    visitedFiles: Set<string>,
    files: ISshConfigFile[],
    hosts: ISshConfigHost[],
    required: boolean
  ): Promise<void> {
    const resolvedPath = plugins.path.resolve(this.expandHome(filePath));
    if (visitedFiles.has(resolvedPath)) {
      return;
    }
    visitedFiles.add(resolvedPath);

    let content = '';
    try {
      content = await plugins.fs.readFile(resolvedPath, 'utf8');
    } catch (error) {
      const nodeError = error as NodeJS.ErrnoException;
      if (nodeError.code === 'ENOENT' && !required) {
        return;
      }
      if (nodeError.code === 'ENOENT' && required) {
        files.push({ filePath: resolvedPath, lines: [] });
        return;
      }
      throw error;
    }

    const lines = content.split(/\r?\n/);
    files.push({ filePath: resolvedPath, lines });
    const includePatterns: string[] = [];
    this.parseHostsInFile(resolvedPath, lines, hosts, includePatterns);

    for (const includePattern of includePatterns) {
      const includeFiles = await this.expandIncludePattern(includePattern, resolvedPath);
      for (const includeFile of includeFiles) {
        await this.readFileRecursive(includeFile, visitedFiles, files, hosts, false);
      }
    }
  }

  private parseHostsInFile(
    filePath: string,
    lines: string[],
    hosts: ISshConfigHost[],
    includePatterns: string[]
  ): void {
    let currentHost: ISshConfigHost | undefined;

    const closeCurrentHost = (endLine: number) => {
      if (!currentHost) {
        return;
      }
      currentHost.endLine = endLine;
      currentHost.rawLines = lines.slice(currentHost.startLine - 1, endLine);
      hosts.push(currentHost);
      currentHost = undefined;
    };

    lines.forEach((rawLine, index) => {
      const lineNumber = index + 1;
      const withoutComment = this.stripInlineComment(rawLine).trim();
      if (!withoutComment) {
        return;
      }

      const directiveMatch = withoutComment.match(/^([^\s]+)\s+(.*)$/);
      if (!directiveMatch) {
        return;
      }

      const directive = directiveMatch[1].toLowerCase();
      const value = directiveMatch[2].trim();

      if (directive === 'include') {
        includePatterns.push(...this.shellSplit(value));
        return;
      }

      if (directive === 'host' || directive === 'match') {
        closeCurrentHost(lineNumber - 1);
      }

      if (directive === 'host') {
        const previousLine = lines[index - 1] ?? '';
        const dapBeginMatch = previousLine.match(/^\s*#\s*dap:begin\s+(.+)\s*$/i);
        currentHost = {
          patterns: this.shellSplit(value),
          filePath,
          startLine: lineNumber,
          endLine: lineNumber,
          options: {},
          rawLines: [],
          dapManaged: Boolean(dapBeginMatch),
          dapManagedName: dapBeginMatch?.[1]?.trim(),
        };
        return;
      }

      if (currentHost) {
        const normalizedDirective = directive.toLowerCase();
        currentHost.options[normalizedDirective] = currentHost.options[normalizedDirective] ?? [];
        currentHost.options[normalizedDirective].push(value);
      }
    });

    closeCurrentHost(lines.length);
  }

  private stripInlineComment(line: string): string {
    let quote: string | undefined;
    let escaped = false;
    for (let i = 0; i < line.length; i++) {
      const char = line[i];
      if (escaped) {
        escaped = false;
        continue;
      }
      if (char === '\\') {
        escaped = true;
        continue;
      }
      if ((char === '"' || char === "'") && !quote) {
        quote = char;
        continue;
      }
      if (char === quote) {
        quote = undefined;
        continue;
      }
      if (char === '#' && !quote && (i === 0 || /\s/.test(line[i - 1]))) {
        return line.slice(0, i);
      }
    }
    return line;
  }

  public shellSplit(input: string): string[] {
    const tokens: string[] = [];
    let current = '';
    let quote: string | undefined;
    let escaped = false;

    for (const char of input) {
      if (escaped) {
        current += char;
        escaped = false;
        continue;
      }
      if (char === '\\') {
        escaped = true;
        continue;
      }
      if ((char === '"' || char === "'") && !quote) {
        quote = char;
        continue;
      }
      if (char === quote) {
        quote = undefined;
        continue;
      }
      if (/\s/.test(char) && !quote) {
        if (current) {
          tokens.push(current);
          current = '';
        }
        continue;
      }
      current += char;
    }

    if (current) {
      tokens.push(current);
    }
    return tokens;
  }

  private async expandIncludePattern(pattern: string, includingFilePath: string): Promise<string[]> {
    const expandedPattern = this.expandHome(pattern);
    const absolutePattern = plugins.path.isAbsolute(expandedPattern)
      ? expandedPattern
      : plugins.path.join(plugins.path.dirname(includingFilePath), expandedPattern);
    return this.expandGlob(absolutePattern);
  }

  private async expandGlob(pattern: string): Promise<string[]> {
    const absolutePattern = plugins.path.resolve(pattern);
    if (!this.pathHasWildcard(absolutePattern)) {
      return plugins.fsSync.existsSync(absolutePattern) ? [absolutePattern] : [];
    }

    const parsedPath = plugins.path.parse(absolutePattern);
    const segments = absolutePattern.slice(parsedPath.root.length).split(plugins.path.sep).filter(Boolean);
    const matches: string[] = [];

    const walk = async (currentPath: string, segmentIndex: number): Promise<void> => {
      if (segmentIndex >= segments.length) {
        try {
          const stat = await plugins.fs.stat(currentPath);
          if (stat.isFile()) {
            matches.push(currentPath);
          }
        } catch {
          return;
        }
        return;
      }

      const segment = segments[segmentIndex];
      if (!this.pathHasWildcard(segment)) {
        await walk(plugins.path.join(currentPath, segment), segmentIndex + 1);
        return;
      }

      let entries: plugins.fsSync.Dirent[];
      try {
        entries = await plugins.fs.readdir(currentPath, { withFileTypes: true });
      } catch {
        return;
      }

      const matcher = this.globSegmentToRegExp(segment);
      for (const entry of entries) {
        if (!matcher.test(entry.name)) {
          continue;
        }
        const nextPath = plugins.path.join(currentPath, entry.name);
        if (segmentIndex === segments.length - 1 || entry.isDirectory()) {
          await walk(nextPath, segmentIndex + 1);
        }
      }
    };

    await walk(parsedPath.root, 0);
    return matches.sort();
  }

  private globSegmentToRegExp(segment: string): RegExp {
    const source = segment
      .replace(/[.+^${}()|[\]\\]/g, '\\$&')
      .replace(/\*/g, '[^/]*')
      .replace(/\?/g, '[^/]');
    return new RegExp(`^${source}$`);
  }

  private patternHasWildcard(pattern: string): boolean {
    return /[*?]/.test(pattern);
  }

  private pathHasWildcard(filePath: string): boolean {
    return /[*?]/.test(filePath);
  }
}