McBitFont/McBitFont/ChangeHistory.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using static McBitFont.ChangeHistory;
using static McBitFont.MainForm;

namespace McBitFont {
    internal class ChangeHistory(int depth = 50) {
        private List<ChangeEvent> timeline = [];
        private List<FrameMiniature> canvasChanges = [];
        private List<List<FrameMiniature>> fontChanges = [];
        public int Depth { get; set; } = depth;
        public int Index { get; set; } = -1;
        public int Count {
            get { return timeline.Count; }
        }

        public enum ChangeType {
            None   = 0,
            Canvas = 1, // Changes made to canvas
            Font   = 2  // Symbol width has been changed
        }
        public class ChangeEvent(ChangeType type, int index) {
            public ChangeType Type { get; set; } = type;
            public int Index { get; set; } = index;
        }

        private static FrameMiniature CopyFrameSimple(FrameMiniature f) {
            FrameMiniature newf = new(f.code, f.width, f.height);
            Array.Copy(f.data, newf.data, f.data.Length);
            return newf;
        }

        public void Clear() {
            timeline.Clear();
            canvasChanges.Clear();
            fontChanges.Clear();
            Index = -1;
        }

        // Remove oldest event and recalculate indices
        private bool RemoveOldest() {
            if (Count == 0) return false;
            ChangeType ct = timeline.First().Type;
            
            switch (ct) {
                case ChangeType.Canvas:
                    if (canvasChanges.Count == 0) return false;
                    canvasChanges.RemoveAt(0);
                    break;
                case ChangeType.Font:
                    if (fontChanges.Count == 0) return false;
                    fontChanges.RemoveAt(0);
                    break;
                default:
                    return false;
            }
            timeline.RemoveAt(0);
            for (int i = 0; i < Count; i++) {
                if (timeline[i].Type == ct) timeline[i].Index--;
            }
            return true;
        }

        public bool Remove(bool useIndex = true) {
            if (Index == -1) return false;
            var ce = timeline.Last();
            switch (ce.Type) {
                case ChangeType.Canvas:
                    canvasChanges.RemoveAt(ce.Index);
                    break;
                case ChangeType.Font:
                    fontChanges.RemoveAt(ce.Index);
                    break;
                default:
                    return false;
            }
            timeline.Remove(ce);
            if (useIndex) Index--;
            return true;
        }

        // Remove history tail
        private void TruncateTail() {
            // Check if the Index does not point to the last event
            if (Index >= 0 && Index < Count - 1) {
                timeline.RemoveRange(Index + 1, Count - Index - 1);
            }
        }

        // Add canvas change
        public void Add(FrameMiniature f) {
            TruncateTail();

            canvasChanges.Add(CopyFrameSimple(f));
            timeline.Add(new ChangeEvent(ChangeType.Canvas, canvasChanges.Count - 1));
            if (Count > Depth) RemoveOldest();
            else Index++;
        }

        // Add Font change
        public void Add(List<FrameMiniature> ff) {
            //TruncateTail();

            //fontChanges.Add(CopyFrameSimple(f));
            //timeline.Add(new ChangeEvent(ChangeType.Canvas, canvasChanges.Count - 1));
            //if (Count > Depth) RemoveOldest();
            //else Index++;
        }
    }
}