ZonyLrcToolsX/src/ZonyLrcTools.Common/Lyrics/LyricsItemCollection.cs

using System.Text;
using ZonyLrcTools.Common.Configuration;
using ZonyLrcTools.Common.Infrastructure.Extensions;

namespace ZonyLrcTools.Common.Lyrics
{
    /// <summary>
    /// 歌词数据，包含多条歌词行对象(<see cref="LyricsItem"/>)。
    /// </summary>
    public class LyricsItemCollection : List<LyricsItem>
    {
        /// <summary>
        /// 是否为纯音乐，当没有任何歌词数据的时候，属性值为 True。
        /// </summary>
        public bool IsPruneMusic => Count == 0;

        public GlobalLyricsConfigOptions? Options { get; }

        public LyricsItemCollection(GlobalLyricsConfigOptions? options)
        {
            Options = options;
        }

        public static LyricsItemCollection operator +(LyricsItemCollection left, LyricsItemCollection right)
        {
            if (right.IsPruneMusic)
            {
                return left;
            }

            var option = left.Options;
            if (option == null)
            {
                throw new NullReferenceException("LyricsItemCollection.Options");
            }

            var newCollection = new LyricsItemCollection(option);
            var indexDiff = left.Count - right.Count;
            if (!option.IsOneLine)
            {
                left.ForEach(item => newCollection.Add(item));
                right.ForEach(item => newCollection.Add(item));

                newCollection.Sort();
                return newCollection;
            }

            // 如果索引相等，直接根据索引快速匹配构建。
            if (indexDiff == 0)
            {
                newCollection.AddRange(left.Select((t, index) => t + right[index]));

                return newCollection;
            }

            // 首先按照时间轴进行合并。
            var leftMarkDict = BuildMarkDictionary(left);
            var rightMarkDict = BuildMarkDictionary(right);

            for (var leftIndex = 0; leftIndex < left.Count; leftIndex++)
            {
                var rightItem = right.Find(lyric => Math.Abs(lyric.SortScore - left[leftIndex].SortScore) < 0.001);
                if (rightItem != null)
                {
                    newCollection.Add(left[leftIndex] + rightItem);
                    var rightIndex = right.FindIndex(item => item == rightItem);
                    rightMarkDict[rightIndex] = true;
                }
                else
                {
                    newCollection.Add(left[leftIndex]);
                }

                leftMarkDict[leftIndex] = true;
            }

            // 遍历未处理的歌词项，将其添加到返回集合当中。
            var leftWaitProcessIndex = leftMarkDict
                .Where(item => !item.Value)
                .Select(pair => pair.Key);
            var rightWaitProcessIndex = rightMarkDict
                .Where(item => !item.Value)
                .Select(pair => pair.Key);

            leftWaitProcessIndex.Foreach(index => newCollection.Add(left[index]));
            rightWaitProcessIndex.Foreach(index => newCollection.Add(right[index]));

            newCollection.Sort();
            return newCollection;
        }

        /// <summary>
        /// 根据歌词集合构建一个索引状态字典。
        /// </summary>
        /// <remarks>
        /// 这个索引字典用于标识每个索引的歌词是否被处理，为 True 则为已处理，为 False 为未处理。
        /// </remarks>
        /// <param name="items">等待构建的歌词集合实例。</param>
        private static Dictionary<int, bool> BuildMarkDictionary(LyricsItemCollection items)
        {
            return items
                .Select((item, index) => new { index, item })
                .ToDictionary(item => item.index, item => false);
        }

        public override string ToString()
        {
            if (Options == null)
            {
                throw new NullReferenceException("LyricsItemCollection.Options");
            }

            var lyricBuilder = new StringBuilder();
            ForEach(lyric => lyricBuilder.Append(lyric).Append(Options.LineBreak));
            return lyricBuilder.ToString().TrimEnd(Options.LineBreak);
        }

        public byte[] GetUtf8Bytes()
        {
            return Encoding.UTF8.GetBytes(ToString());
        }
    }
}