Add plugin to fetch most voted solution.

Signed-off-by: Eric Wang <skygragon@gmail.com>

Author: skygragon

solution.discuss.js

@@ -0,0 +1,61 @@
+var _ = require('underscore');
+var request = require('request');
+
+var log = require('../log');
+var chalk = require('../chalk');
+var Plugin = require('../plugin');
+var session = require('../session');
+
+var plugin = new Plugin(200, 'solution.discuss', '2017.07.29',
+    'Plugin to fetch most voted solution in discussions.');
+
+var URL_DISCUSSES = 'https://discuss.leetcode.com/api/category/';
+var URL_DISCUSS_TOPIC = 'https://discuss.leetcode.com/topic/';
+
+plugin.getProblem = function(problem, cb) {
+  plugin.next.getProblem(problem, function(e, problem) {
+    if (e || !session.argv.solution) return cb(e, problem);
+
+    var opts = {
+      url: URL_DISCUSSES + problem.discuss
+    };
+    request(opts, function(e, resp, body) {
+      if (e) return cb(e);
+      if (resp.statusCode !== 200)
+        return cb({msg: 'http error', statusCode: resp.statusCode});
+
+      var lang = session.argv.lang;
+      var langs = [lang];
+      // try to find more compatible langs
+      if (lang === 'cpp') langs.push('c++');
+      if (lang === 'csharp') langs.push('c#');
+      if (lang === 'golang') langs.push('go');
+      if (lang === 'javascript') langs.push('js');
+      if (lang === 'python3') langs.push('python');
+
+      var data = JSON.parse(body);
+      var solution = _.find(data.topics, function(x) {
+        var keys = x.title.toLowerCase().split(' ');
+        for (var i = 0; i < keys.length; ++i) {
+          if (langs.indexOf(keys[i]) >= 0) return true;
+        }
+        return false;
+      });
+
+      if (!solution) {
+        return log.error('Solution not found for ' + lang);
+      }
+
+      log.info(solution._imported_title);
+      log.info();
+      log.info(chalk.underline(URL_DISCUSS_TOPIC + solution.slug));
+      log.info();
+      log.info('* Lang:  ' + lang);
+      log.info('* Votes: ' + solution.votes);
+      log.info();
+      log.info(chalk.yellow(solution._imported_content));
+    });
+  });
+};
+
+module.exports = plugin;