#!/usr/bin/env ts-node

import * as path from 'path';

import {
  createLanguageService,
  DiagnosticLevel,
  DiagnosticOptions,
  ILogger
} from '@dsanders11/vscode-markdown-languageservice';
import * as minimist from 'minimist';
import fetch from 'node-fetch';
import { CancellationTokenSource } from 'vscode-languageserver';
import { URI } from 'vscode-uri';

import {
  DocsWorkspace,
  MarkdownLinkComputer,
  MarkdownParser
} from './lib/markdown';

class NoOpLogger implements ILogger {
  log (): void {}
}

const diagnosticOptions: DiagnosticOptions = {
  ignoreLinks: [],
  validateDuplicateLinkDefinitions: DiagnosticLevel.error,
  validateFileLinks: DiagnosticLevel.error,
  validateFragmentLinks: DiagnosticLevel.error,
  validateMarkdownFileLinkFragments: DiagnosticLevel.error,
  validateReferences: DiagnosticLevel.error,
  validateUnusedLinkDefinitions: DiagnosticLevel.error
};

async function fetchExternalLink (link: string, checkRedirects = false) {
  try {
    const response = await fetch(link);
    if (response.status !== 200) {
      console.log('Broken link', link, response.status, response.statusText);
    } else {
      if (checkRedirects && response.redirected) {
        const wwwUrl = new URL(link);
        wwwUrl.hostname = `www.${wwwUrl.hostname}`;

        // For now cut down on noise to find meaningful redirects
        const wwwRedirect = wwwUrl.toString() === response.url;
        const trailingSlashRedirect = `${link}/` === response.url;

        if (!wwwRedirect && !trailingSlashRedirect) {
          console.log('Link redirection', link, '->', response.url);
        }
      }

      return true;
    }
  } catch {
    console.log('Broken link', link);
  }

  return false;
}

async function main ({ fetchExternalLinks = false, checkRedirects = false }) {
  const workspace = new DocsWorkspace(path.resolve(__dirname, '..', 'docs'));
  const parser = new MarkdownParser();
  const linkComputer = new MarkdownLinkComputer(workspace);
  const languageService = createLanguageService({
    workspace,
    parser,
    logger: new NoOpLogger(),
    linkComputer
  });

  const cts = new CancellationTokenSource();
  let errors = false;

  const externalLinks = new Set<string>();

  try {
    // Collect diagnostics for all documents in the workspace
    for (const document of await workspace.getAllMarkdownDocuments()) {
      for (let link of await languageService.getDocumentLinks(
        document,
        cts.token
      )) {
        if (link.target === undefined) {
          link =
            (await languageService.resolveDocumentLink(link, cts.token)) ??
            link;
        }

        if (
          link.target &&
          link.target.startsWith('http') &&
          new URL(link.target).hostname !== 'localhost'
        ) {
          externalLinks.add(link.target);
        }
      }
      const diagnostics = await languageService.computeDiagnostics(
        document,
        diagnosticOptions,
        cts.token
      );

      if (diagnostics.length) {
        console.log(
          'File Location:',
          path.relative(workspace.root, URI.parse(document.uri).path)
        );
      }

      for (const diagnostic of diagnostics) {
        console.log(
          `\tBroken link on line ${diagnostic.range.start.line + 1}:`,
          diagnostic.message
        );
        errors = true;
      }
    }
  } finally {
    cts.dispose();
  }

  if (fetchExternalLinks) {
    const externalLinkStates = await Promise.all(
      Array.from(externalLinks).map((link) =>
        fetchExternalLink(link, checkRedirects)
      )
    );

    errors = errors || !externalLinkStates.every((x) => x);
  }

  return errors;
}

function parseCommandLine () {
  const showUsage = (arg?: string): boolean => {
    if (!arg || arg.startsWith('-')) {
      console.log(
        'Usage: script/lint-docs-links.ts [-h|--help] [--fetch-external-links] ' +
          '[--check-redirects]'
      );
      process.exit(0);
    }

    return true;
  };

  const opts = minimist(process.argv.slice(2), {
    boolean: ['help', 'fetch-external-links', 'check-redirects'],
    stopEarly: true,
    unknown: showUsage
  });

  if (opts.help) showUsage();

  return opts;
}

if (process.mainModule === module) {
  const opts = parseCommandLine();

  main({
    fetchExternalLinks: opts['fetch-external-links'],
    checkRedirects: opts['check-redirects']
  })
    .then((errors) => {
      if (errors) process.exit(1);
    })
    .catch((error) => {
      console.error(error);
      process.exit(1);
    });
}