src/docs/LuceneDocsPlugins/EnvironmentVariableInlineRule.cs

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

using System;
using System.Collections.Immutable;
using System.Text.RegularExpressions;
using Microsoft.DocAsCode.MarkdownLite;

namespace LuceneDocsPlugins
{
    public class EnvironmentVariableInlineRule : IMarkdownRule
    {
        // give it a name
        public string Name => "EnvVarToken";

        // define my regex to match
        private static readonly Regex _envVarRegex = new Regex(@"^\<EnvVar:(\w+?)\>", RegexOptions.Compiled);

        // process the match
        public IMarkdownToken TryMatch(IMarkdownParser parser, IMarkdownParsingContext context)
        {
            // TODO: This does not process this token from within a code block like

            // ```
            // dotnet tool install lucene-cli -g --version [EnvVar: LuceneNetVersion]
            // ```

            var match = _envVarRegex.Match(context.CurrentMarkdown);
            if (match.Length == 0) return null;

            var envVar = match.Groups[1].Value;
            var text = Environment.GetEnvironmentVariable(envVar);
            if (text == null) return null;

            // 'eat' the characters of the current markdown token so they anr
            var sourceInfo = context.Consume(match.Length);
            return new MarkdownTextToken(this, parser.Context, text, sourceInfo);
        }
    }
}