using System;
using System.Collections.Generic;
using System.Threading;

using FluentValidation;

using MfGames.Gallium;
using MfGames.Nitride.Contents;
using MfGames.Nitride.Generators;

using Zio;

namespace MfGames.Nitride.Html;

/// <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 IdentifyHtml : IOperation
{
    private readonly IValidator<IdentifyHtml> validator;

    public IdentifyHtml(IValidator<IdentifyHtml> validator)
    {
        this.validator = validator;
    }

    public Func<Entity, UPath, bool> IsHtmlTest { get; set; } = null!;

    /// <inheritdoc />
    public IEnumerable<Entity> Run(
        IEnumerable<Entity> input,
        CancellationToken cancellationToken = default)
    {
        this.validator.ValidateAndThrow(this);

        return input.SelectEntity<UPath, ITextContent>(this.MarkTextEntities)
            .SelectEntity<UPath, IBinaryContent>(this.MarkBinaryEntities);
    }

    private Entity MarkBinaryEntities(
        Entity entity,
        UPath path,
        IBinaryContent binary)
    {
        // If we aren't a Markdown file, then there is nothing we can do about that.
        if (!this.IsHtmlTest(entity, path))
        {
            return entity;
        }

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

        return entity;
    }

    private Entity MarkTextEntities(
        Entity entity,
        UPath path,
        ITextContent _)
    {
        return this.IsHtmlTest(entity, path)
            ? entity.SetIsHtml()
            : entity;
    }
}