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LinesParser.cs
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LinesParser.cs
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using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using YetAnotherPacketParser.Ast;
using YetAnotherPacketParser.Lexer;
namespace YetAnotherPacketParser.Parser
{
public class LinesParser : IParser
{
private const int FailureSnippetCharacterLimit = 40;
private const int MaximumFailureMessagesPerSection = 10;
public LinesParser(LinesParserOptions? options = null)
{
if (options == null)
{
options = LinesParserOptions.Default;
}
this.Options = options;
}
public LinesParserOptions Options { get; }
/// <summary>
/// Converts the list of lines into an abstract syntax tree, with the PacketNode as a root.
/// </summary>
/// <param name="lines">Lines of the packet to parse</param>
/// <returns>If parsing was successful, a PacketNode representing the structure of the packet. Otherwise, an
/// error message explaining what went wrong.</returns>
public IResult<PacketNode> Parse(IEnumerable<ILine> lines)
{
Verify.IsNotNull(lines, nameof(lines));
using (LinesEnumerator enumerator = new LinesEnumerator(lines))
{
if (!enumerator.MoveNext())
{
return new FailureResult<PacketNode>(Strings.CannotParseEmptyPacket);
}
List<string> errorMessages = new List<string>();
IResult<List<TossupNode>> tossupsResult = ParseTossups(enumerator, out bool moreLinesExist);
if (!tossupsResult.Success)
{
errorMessages.AddRange(tossupsResult.ErrorMessages);
}
if (!moreLinesExist)
{
if (!tossupsResult.Success)
{
return new FailureResult<PacketNode>(tossupsResult.ErrorMessages);
}
return new SuccessResult<PacketNode>(new PacketNode(tossupsResult.Value, bonuses: null));
}
IResult<List<BonusNode>> bonusesResult = ParseBonuses(enumerator);
if (!bonusesResult.Success)
{
errorMessages.AddRange(bonusesResult.ErrorMessages);
}
if (errorMessages.Count > 0)
{
return new FailureResult<PacketNode>(errorMessages);
}
return new SuccessResult<PacketNode>(new PacketNode(tossupsResult.Value, bonusesResult.Value));
}
}
private static IResult<FormattedText> GetTextFromLines(
LinesEnumerator lines, string context, LineType nextExpectedLineType)
{
FormattedText formattedText = lines.Current.Text;
IEnumerable<FormattedTextSegment> formattedTextSegments = formattedText.Segments;
if (lines.Current.Type == nextExpectedLineType)
{
return new SuccessResult<FormattedText>(formattedText);
}
// The question number + question stays the same. We should do this in a loop (move next, is answer line, etc.)
int linesChecked = 0;
bool foundNextToken = false;
while (lines.MoveNext())
{
if (lines.Current.Type == nextExpectedLineType)
{
foundNextToken = true;
break;
}
else if (lines.Current.Type != LineType.Unclassified)
{
return new FailureResult<FormattedText>(GetFailureMessage(
lines, Strings.UnexpectedToken(nextExpectedLineType, lines.Current.Type)));
}
// Keep adding to the question text, since it's not done
formattedTextSegments = formattedTextSegments.Concat(lines.Current.Text.Segments);
linesChecked++;
}
if (!foundNextToken)
{
return new FailureResult<FormattedText>(GetFailureMessage(
lines, Strings.NoMoreLinesFound(context, linesChecked + 1)));
}
// The question needs to be pieced together from different lines, so create a new FormattedText
formattedText = new FormattedText(formattedTextSegments);
return new SuccessResult<FormattedText>(formattedText);
}
private static string? GetMetadataText(LinesEnumerator lines)
{
if (!TryGetPostQuestionMetadata(lines, out PostQuestionMetadataLine? metadataLine) || metadataLine == null)
{
return null;
}
string metadata = metadataLine.Text.UnformattedText;
if (metadata.Length > 2)
{
int metadataStart = metadata.IndexOf('<', StringComparison.Ordinal);
int metadataEnd = metadata.LastIndexOf('>');
if (metadataStart >= 0 && metadataStart < metadata.Length + 1 && metadataEnd > metadataStart)
{
metadata = metadata.Substring(metadataStart + 1, metadataEnd - 1);
}
}
return metadata;
}
private static string GetFailureMessage(LinesEnumerator lines, string message)
{
StringBuilder snippet = new StringBuilder(10);
ILine? currentLine = null;
try
{
currentLine = lines.Current;
}
catch (InvalidOperationException)
{
// We're at the end. No more lines
}
if (currentLine != null)
{
int remainingLength = FailureSnippetCharacterLimit;
foreach (FormattedTextSegment segment in lines.Current.Text.Segments)
{
if (segment.Text.Length <= remainingLength)
{
snippet.Append(segment.Text);
}
else
{
snippet.Append(segment.Text.AsSpan(0, remainingLength));
}
remainingLength = checked(FailureSnippetCharacterLimit - snippet.Length);
if (remainingLength < 0)
{
break;
}
}
}
return Strings.ParseFailureMessage(message, lines.LineNumber, snippet.ToString());
}
private static bool TryGetPostQuestionMetadata(LinesEnumerator lines, out PostQuestionMetadataLine? line)
{
line = null;
try
{
if (lines.Current == null)
{
return false;
}
}
catch (InvalidOperationException)
{
return false;
}
do
{
switch (lines.Current.Type)
{
// Post-question metadata normally follows an answer, though there could be some unclassified lines
// in-between if there are some extra newlines between them.
case LineType.Answer:
case LineType.Unclassified:
continue;
case LineType.PostQuestionMetadata:
if (lines.Current is PostQuestionMetadataLine metadataLine)
{
line = metadataLine;
return true;
}
return false;
default:
return false;
}
} while (lines.MoveNext());
return false;
}
private static bool TryGetNextQuestionLine(LinesEnumerator lines, out NumberedQuestionLine? line)
{
// Skip lines until we get to the next question
line = null;
try
{
// In certain cases (split bonus part line), we'll seek out a new line even if we've reached the end.
// Instead of failing, report that we can't get the next question line.
if (lines.Current == null)
{
return false;
}
}
catch (InvalidOperationException)
{
return false;
}
do
{
if (lines.Current.Type == LineType.NumberedQuestion &&
lines.Current is NumberedQuestionLine numberedLine)
{
line = numberedLine;
return true;
}
} while (lines.MoveNext());
return false;
}
private static bool TryGetQuestionNumber(ILine line, out int questionNumber)
{
questionNumber = 0;
if (!(line.Type == LineType.NumberedQuestion && line is NumberedQuestionLine numberedLine))
{
return false;
}
questionNumber = numberedLine.Number;
return true;
}
private static IResult<List<TossupNode>> ParseTossups(LinesEnumerator lines, out bool moreLinesExist)
{
int currentQuestionNumber = -1;
List<TossupNode> tossupNodes = new List<TossupNode>();
List<string>? errorMessages = null;
// If the question number drops, it means we're in bonuses now, so stop parsing tossups
NumberedQuestionLine? line;
while (TryGetNextQuestionLine(lines, out line) && line != null && line.Number > currentQuestionNumber)
{
currentQuestionNumber = line.Number;
IResult<TossupNode> tossupResult = ParseTossup(lines, tossupNodes.Count + 1);
if (!tossupResult.Success)
{
if (errorMessages == null)
{
errorMessages = new List<string>();
}
errorMessages.AddRange(tossupResult.ErrorMessages);
if (errorMessages.Count == MaximumFailureMessagesPerSection)
{
break;
}
continue;
}
tossupNodes.Add(tossupResult.Value);
}
if (tossupNodes.Count == 0 && errorMessages != null && errorMessages.Count != MaximumFailureMessagesPerSection)
{
errorMessages.Add(GetFailureMessage(lines, Strings.NoTossupsFound));
}
moreLinesExist = line != null;
if (errorMessages != null)
{
return new FailureResult<List<TossupNode>>(errorMessages);
}
return new SuccessResult<List<TossupNode>>(tossupNodes);
}
private static IResult<List<BonusNode>> ParseBonuses(LinesEnumerator lines)
{
List<BonusNode> bonusNodes = new List<BonusNode>();
List<string>? errorMessages = null;
while (TryGetNextQuestionLine(lines, out _))
{
IResult<BonusNode> bonusResult = ParseBonus(lines, bonusNodes.Count + 1);
if (!bonusResult.Success)
{
if (errorMessages == null)
{
errorMessages = new List<string>();
}
errorMessages.AddRange(bonusResult.ErrorMessages);
if (errorMessages.Count > MaximumFailureMessagesPerSection)
{
break;
}
continue;
}
bonusNodes.Add(bonusResult.Value);
}
if (errorMessages != null)
{
return new FailureResult<List<BonusNode>>(errorMessages);
}
// It's okay if bonuses are empty, since bonuses may be optional
return new SuccessResult<List<BonusNode>>(bonusNodes);
}
private static IResult<TossupNode> ParseTossup(LinesEnumerator lines, int tossupNumber)
{
if (!TryGetQuestionNumber(lines.Current, out int questionNumber))
{
return new FailureResult<TossupNode>(GetFailureMessage(
lines, Strings.NoTossupQuestionNumberFound(tossupNumber)));
}
IResult<QuestionNode> questionResult = ParseQuestion(lines, $"tossup #{tossupNumber}");
if (!questionResult.Success)
{
return new FailureResult<TossupNode>(questionResult.ErrorMessages);
}
string? metadata = GetMetadataText(lines);
return new SuccessResult<TossupNode>(new TossupNode(questionNumber, questionResult.Value, metadata));
}
private static IResult<BonusNode> ParseBonus(LinesEnumerator lines, int bonusNumber)
{
if (!TryGetQuestionNumber(lines.Current, out int questionNumber))
{
return new FailureResult<BonusNode>(GetFailureMessage(
lines, Strings.NoBonusQuestionNumberFound(bonusNumber)));
}
IResult<FormattedText> leadinResult = GetTextFromLines(
lines, $"Bonus leadin (#{bonusNumber})", LineType.BonusPart);
if (!leadinResult.Success)
{
return new FailureResult<BonusNode>(leadinResult.ErrorMessages);
}
IResult<List<BonusPartNode>> bonusPartsResult = ParseBonusParts(lines);
if (!bonusPartsResult.Success)
{
return new FailureResult<BonusNode>(bonusPartsResult.ErrorMessages);
}
// Metadata is always at the end of all of the bonus parts
string? metadata = GetMetadataText(lines);
return new SuccessResult<BonusNode>(new BonusNode(
questionNumber, leadinResult.Value, bonusPartsResult.Value, metadata));
}
private static IResult<List<BonusPartNode>> ParseBonusParts(LinesEnumerator lines)
{
List<BonusPartNode> parts = new List<BonusPartNode>();
do
{
if (lines.Current.Type != LineType.BonusPart)
{
// We're no longer on bonus parts, so get out of the loop
break;
}
IResult<BonusPartNode> bonusPartResult = ParseBonusPart(lines, parts.Count + 1);
if (!bonusPartResult.Success)
{
return new FailureResult<List<BonusPartNode>>(bonusPartResult.ErrorMessages);
}
parts.Add(bonusPartResult.Value);
} while (lines.MoveNext());
if (parts.Count == 0)
{
return new FailureResult<List<BonusPartNode>>(GetFailureMessage(
lines, Strings.CouldntFindBonusPartValueInFirstBlock));
}
return new SuccessResult<List<BonusPartNode>>(parts);
}
private static IResult<BonusPartNode> ParseBonusPart(LinesEnumerator lines, int bonusPartNumber)
{
// Should follow the format
// [value] question
// ANSWER: xxx
if (!(lines.Current.Type == LineType.BonusPart && lines.Current is BonusPartLine bonusPartLine))
{
return new FailureResult<BonusPartNode>(GetFailureMessage(
lines, Strings.CouldntFindBonusPartValue));
}
int partValue = bonusPartLine.Value;
IResult<QuestionNode> questionResult = ParseQuestion(lines, $"bonus part #{bonusPartNumber}");
if (!questionResult.Success)
{
return new FailureResult<BonusPartNode>(questionResult.ErrorMessages);
}
return new SuccessResult<BonusPartNode>(
new BonusPartNode(questionResult.Value, partValue, bonusPartLine.DifficultyModifier));
}
private static IResult<QuestionNode> ParseQuestion(LinesEnumerator lines, string context)
{
IResult<FormattedText> questionResult = GetTextFromLines(lines, context, LineType.Answer);
if (!questionResult.Success)
{
return new FailureResult<QuestionNode>(questionResult.ErrorMessages);
}
else if (lines.Current.Type != LineType.Answer)
{
return new FailureResult<QuestionNode>(GetFailureMessage(
lines, Strings.UnknownLineTypeforAnswer(context, lines.Current.Type)));
}
// We can't support multi-line answers, since the answer is the last part of the unit (tossup or bonus).
// There maybe extra text (editor's notes, headers) that come after, and we don't have a good way of
// deciding if it belongs to the answer or not
FormattedText answer = lines.Current.Text;
// TODO: Support editor's notes. Would require changing the lexer, or having some look-behind so we can
// see if the previous line starts with an editor's note tag.
return new SuccessResult<QuestionNode>(new QuestionNode(questionResult.Value, answer));
}
private class LinesEnumerator : IEnumerator<ILine>
{
public LinesEnumerator(IEnumerable<ILine> lines)
{
this.Enumerator = lines.GetEnumerator();
this.LineNumber = 1;
}
public ILine Current => this.Enumerator.Current;
public int LineNumber { get; private set; }
private IEnumerator<ILine> Enumerator { get; }
object? IEnumerator.Current => this.Enumerator.Current;
public void Dispose()
{
this.Enumerator.Dispose();
}
public bool MoveNext()
{
bool moveNext = this.Enumerator.MoveNext();
if (moveNext)
{
this.LineNumber++;
}
return moveNext;
}
public void Reset()
{
this.Enumerator.Reset();
this.LineNumber = 1;
}
}
}
}