using System;
using System.Collections.Generic;

using HandlebarsDotNet;

namespace MfGames.Nitride.Handlebars.Configuration;

/// <summary>
/// </summary>
/// <typeparam name="TModel">A typesafe model of the template.</typeparam>
public class ForEachHandlebarsBlock<TModel> : HandlebarsBlockBase
{
    public ForEachHandlebarsBlock(string helperName)
    {
        this.HelperName = helperName;
    }

    /// <summary>
    /// Gets or sets the list that needs to be rendered.
    /// </summary>
    public Func<TModel, IEnumerable<object>>? GetList { get; set; }

    /// <summary>
    /// Gets or sets the callback that is called when nothing is found.
    /// </summary>
    public Action<EncodedTextWriter, BlockHelperOptions, Context, Arguments>? NothingFound { get; set; }

    /// <inheritdoc />
    protected override string HelperName { get; }

    public ForEachHandlebarsBlock<TModel> WithGetList(Func<TModel, IEnumerable<object>>? callback)
    {
        this.GetList = callback;

        return this;
    }

    public ForEachHandlebarsBlock<TModel> WithNothingFoundText(
        Action<EncodedTextWriter, BlockHelperOptions, Context, Arguments>? callback)
    {
        this.NothingFound = callback;

        return this;
    }

    /// <summary>
    /// Sets the output to write out text when no items are found.
    /// </summary>
    /// <param name="text">The text to write out.</param>
    /// <returns>The same object for chained methods.</returns>
    public ForEachHandlebarsBlock<TModel> WithNothingFoundText(string text)
    {
        this.NothingFound = (
            output,
            _1,
            _2,
            _3) => output.Write(text);

        return this;
    }

    /// <inheritdoc />
    protected override void Render(
        EncodedTextWriter output,
        BlockHelperOptions options,
        Context context,
        Arguments input)
    {
        if (context.Value is not TModel model)
        {
            throw new InvalidOperationException(
                string.Format(
                    "Cannot apply the {0} on context value because it is {1}.",
                    nameof(ForEachHandlebarsBlock<TModel>),
                    context.Value.GetType()));
        }

        IEnumerable<object>? list = this.GetList?.Invoke(model);
        bool hasItems = false;

        if (list != null)
        {
            foreach (object item in list)
            {
                hasItems = true;
                options.Template(output, item);
            }
        }

        if (!hasItems)
        {
            this.NothingFound?.Invoke(output, options, context, input);
        }
    }
}