mfgames-nitride-cil/src/Nitride.Markdown/IdentifyMarkdown.cs

using System;
using System.Collections.Generic;
using Gallium;
using Nitride.Contents;
using Zio;

namespace Nitride.Markdown
{
    /// <summary>
    /// An operation that identifies Markdown files by their common extensions
    /// and converts them to text input while also adding the IsMarkdown
    /// component to identify them.
    /// </summary>
    [WithProperties]
    public partial class IdentifyMarkdown : INitrideOperation
    {
        public IdentifyMarkdown()
        {
            this.IsMarkdownTest = DefaultIsMarkdown;
        }

        public Func<Entity, UPath, bool> IsMarkdownTest { get; set; }

        /// <inheritdoc />
        public IEnumerable<Entity> Run(IEnumerable<Entity> input)
        {
            return input
                .ForEachEntity<UPath, ITextContent>(
                    (entity, path, _) =>
                    {
                        // If we aren't a Markdown file, then there is nothing
                        // we can do about that.
                        if (!this.IsMarkdownTest(entity, path))
                        {
                            return entity;
                        }

                        // We are already text, so just mark it as Markdown.
                        entity = entity
                            .Set(IsMarkdown.Instance);

                        return entity;
                    })
                .ForEachEntity<UPath, IBinaryContent>(
                    (entity, path, binary) =>
                    {
                        // If we aren't a Markdown file, then there is nothing
                        // we can do about that.
                        if (!this.IsMarkdownTest(entity, path))
                        {
                            return entity;
                        }

                        // Convert the file as a binary.
                        if (binary is ITextContentConvertable textConvertable)
                        {
                            entity = entity
                                .SetTextContent(textConvertable.ToTextContent())
                                .Set(IsMarkdown.Instance);
                        }
                        else
                        {
                            throw new InvalidOperationException(
                                "Cannot convert a binary content to a "
                                + "text without ITextContentConvertable.");
                        }

                        return entity;
                    });
        }

        private static bool DefaultIsMarkdown(Entity entity, UPath path)
        {
            return (path.GetExtensionWithDot() ?? string.Empty)
                .ToLowerInvariant() switch
                {
                    ".md" => true,
                    ".markdown" => true,
                    _ => false,
                };
        }
    }
}