Brc/BrcReader.cs at master · OLDRedstone/Brc · GitHub

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#nullable enable
using System.Collections.Generic;
using System.IO;
using System.Linq;
using static Brc.BrcGlobal;

namespace Brc
{
	public class BrcReader
	{
		private readonly StringReader reader;
		private readonly List<BrcSentence> sentences = [];
		private List<List<BrcWord>> words = [];
		private BrcReader(string filepath) => reader = new(File.ReadAllText(filepath));
		private bool Read(out char value)
		{
			value = '\0';
			int r = reader.Read();
			if (r == -1) return false;
			value = (char)r;
			return true;
		}
		private bool Peek(out char value)
		{
			value = '\0';
			int r = reader.Peek();
			if (r == -1) return false;
			value = (char)r;
			return true;
		}
		private bool CheckRead(in char b)
		{
			if (Peek(out char c) && c == b)
			{ Read(out c); return true; }
			return false;
		}
		private void ReadWhitespace()
		{
			while (Peek(out char c) && char.IsWhiteSpace(c))
				Read(out char _);
		}
		private bool Read(out int value)
		{
			value = 0;
			bool r = false;
			while (Peek(out char c) && char.IsDigit(c))
			{
				Read(out c);
				value *= 10;
				value += c - '0';
				r = true;
			}
			return r;
		}
		private bool Read(out float value)
		{
			value = 0;
			bool r = false;
			while (Peek(out char c) && char.IsDigit(c))
			{
				Read(out c);
				value *= 10;
				value += c - '0';
				r = true;
			}
			int id = 0;
			if (CheckRead('.'))
				while (Peek(out char c) && char.IsDigit(c))
				{
					Read(out c);
					value *= 10;
					value += c - '0';
					id++;
				}
			for (; id > 0; id--)
				value /= 10;
			return r;
		}
		private void Read(int fpb, out BrcWord value)
		{
			string w = string.Empty;
			int interval = 1;
			while (Peek(out char c)
				&& c is not (_separator or _sentence or _leftbucket or _rightbucket or _connect))
			{
				Read(out c);
				if (c is _escape)
				{
					if (Peek(out char t))
					{
						Read(out t);
						w += t;
					}
				}
				else
					w += c;
			}
			while (Peek(out char c) && c is _connect)
			{
				Read(out char _);
				interval++;
			}
			value = new() { Word = w, Duration = (float)interval / fpb };
		}
		private void Wrap(int offset, int bpb, int fpb, float bpm)
		{
			BrcSentence brcSentence = new([.. words.Select(i => new BrcLine([.. i]))])
			{
				BeatsPerMinute = bpm,
				BeatsPerBar = bpb,
				NotePerBeat = fpb,
				Offset = offset
			};
			words = [];
			sentences.Add(brcSentence);
		}
		private Brc Read()
		{
			int off = 0, bpb = 8, fpb = 4, offl = 0;
			float bpm = 120;
			if (Peek(out char tmp1) && char.IsDigit(tmp1))
				Read(out off);
			ReadWhitespace();
			bool flag = Peek(out char t);
			while (flag)
			{
				ReadWhitespace();
				switch (t)
				{
					case _sentence:
						Read(out char _);
						ReadWhitespace();
						Wrap(offl, bpb, fpb, bpm);
						break;
					case _separator:
						Read(out char _);
						break;
					case _leftbucket:
						Read(out char _);
						ReadWhitespace();
						flag &= Read(out bpb);
						ReadWhitespace();
						flag &= CheckRead(_comma);
						ReadWhitespace();
						flag &= Read(out fpb);
						ReadWhitespace();
						if (CheckRead(_comma))
							flag &= Read(out bpm);
						ReadWhitespace();
						if (CheckRead(_comma))
							flag &= Read(out offl);
						ReadWhitespace();
						flag &= CheckRead(_rightbucket);
						break;
					case _newLine:
						Read(out char _);
						words.Add([]);
						break;
					case _escape or _connect or _:
						Read(fpb, out BrcWord word);
						if (words.Count == 0)
							words.Add([]);
						words.Last().Add(word);
						break;
				}
				flag &= Peek(out t);
			}
			if (words.Count != 0)
				Wrap(offl, bpb, fpb, bpm);
			return new([.. sentences]) { Offset = off };
		}
		public static Brc Read(string filepath) => new BrcReader(filepath).Read();
	}
}