using System;
using System.Text.RegularExpressions;

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

using Zio;

namespace MfGames.Nitride.Temporal.Schedules;

/// <summary>
/// A common base for a schedule that is built off the path associated with
/// the entity.
/// </summary>
[WithProperties]
public abstract partial class PathRegexScheduleBase : ISchedule
{
    protected PathRegexScheduleBase()
    {
        this.PathRegex = @"^.*?(\d+)[^\d]*$";
        this.GetPath = entity => entity.Get<UPath>().ToString();
        this.CaptureGroup = 1;
    }

    /// <summary>
    /// Gets or sets the group number of the capture group with 1 being being the
    /// first group in PathRegex.
    /// </summary>
    public int CaptureGroup { get; set; }

    /// <summary>
    /// Gets or sets the offset to make the resulting capture group a zero-based
    /// number.
    /// </summary>
    public int CaptureOffset { get; set; }

    /// <summary>
    /// Gets or sets the method for retrieving the path for the entity.
    /// </summary>
    public Func<Entity, string> GetPath { get; set; }

    /// <summary>
    /// Gets or sets the regular expression to identify a matching path.
    /// </summary>
    public string? PathRegex { get; set; }

    /// <inheritdoc />
    public virtual Entity Apply(
        Entity entity,
        TimeService timeService)
    {
        // Get the path and match it.
        string path = this.GetPath(entity);
        Regex? regex = this.GetRegex();
        Match match = regex?.Match(path)
            ?? throw new NullReferenceException(
                "PathRegex was not configured for the "
                + this.GetType().Name
                + ".");

        if (!match.Success)
        {
            return entity;
        }

        if (match.Groups.Count < 2)
        {
            throw new InvalidOperationException(
                "There must be at least one capture group in '"
                + this.PathRegex
                + "'.");
        }

        // Figure out the index/number of this entry.
        string numberValue = match.Groups[this.CaptureGroup].Value;

        if (!int.TryParse(numberValue, out int number))
        {
            throw new FormatException(
                path + ": Cannot parse '" + numberValue + "' as integer.");
        }

        number += this.CaptureOffset;

        // Pass it onto the extending class.
        return this.Apply(entity, number, timeService);
    }

    /// <inheritdoc />
    public virtual bool CanApply(Entity entity)
    {
        string path = this.GetPath(entity);
        Regex? regex = this.GetRegex();
        Match match = regex?.Match(path)
            ?? throw new NullReferenceException(
                "PathRegex was not configured for the "
                + this.GetType().Name
                + ".");

        return match.Success;
    }

    /// <summary>
    /// Applies the schedule according to the normalized number (after
    /// CaptureOffset).
    /// </summary>
    protected abstract Entity Apply(
        Entity entity,
        int number,
        TimeService timeService);

    private Regex? GetRegex()
    {
        return this.PathRegex == null
            ? null
            : new Regex(this.PathRegex);
    }
}