/// <summary>
/// Reads <see cref="SyntaxToken" />s from a GraphQL
/// <paramref name="source" /> and returns the first token.
/// </summary>
/// <param name="source">
/// The GraphQL source that shall be tokenized.
/// </param>
/// <returns>
/// Returns the first token of the given
/// GraphQL <paramref name="source" />.
/// </returns>
/// <exception cref="SyntaxException">
/// There are unexpected tokens in the given <paramref name="source" />.
/// </exception>
/// <exception cref="ArgumentNullException">
/// <paramref name="source" /> is null.
/// </exception>
public SyntaxToken Read(ISource source)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
var state = new LexerState(source.Text);
try
{
var start = new SyntaxToken(TokenKind.StartOfFile,
0, 0, state.Line, state.Column, null);
SyntaxToken current = start;
do
{
SyntaxToken previous = current;
current = ReadNextToken(state, previous);
previous.Next = current;
}while (current.Kind != TokenKind.EndOfFile);
return(start);
}
catch (Exception ex)
{
throw new SyntaxException(state,
"Unexpected token sequence.",
ex);
}
}
internal SyntaxException(LexerState context, string message)
: base(message)
{
Position = context.Position;
Line = context.Line;
Column = context.Column;
SourceText = context.SourceText;
}
internal SyntaxException(LexerState context, string message)
: base(message)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
Position = context.Position;
Line = context.Line;
Column = context.Column;
SourceText = context.SourceText;
}
/// <summary>
/// Reads the token that comes after the
/// <paramref name="previous"/>-token.
/// </summary>
/// <returns>
/// Returns token that comes after the
/// <paramref name="previous"/>-token.
/// </returns>
/// <param name="state">The lexer state.</param>
/// <param name="previous">The previous-token.</param>
private static SyntaxToken ReadNextToken(
LexerState state,
SyntaxToken previous)
{
SkipWhitespaces(state);
state.UpdateColumn();
if (state.IsEndOfStream())
{
return(new SyntaxToken(TokenKind.EndOfFile, state.Column,
previous.End, state.Line, state.Column,
previous));
}
var code = state.SourceText[state.Position];
if (code.IsLetterOrUnderscore())
{
return(ReadNameToken(state, previous));
}
if (code.IsPunctuator())
{
return(ReadPunctuatorToken(state, previous, in code));
}
if (code.IsDigitOrMinus())
{
return(ReadNumberToken(state, previous, in code));
}
if (code.IsHash())
{
return(ReadCommentToken(state, previous));
}
if (code.IsQuote())
{
if (state.SourceText[state.Position + 1].IsQuote() &&
state.SourceText[state.Position + 2].IsQuote())
{
state.Position += 2;
return(ReadBlockStringToken(state, previous));
}
return(ReadStringValueToken(state, previous));
}
throw new SyntaxException(state, "Unexpected character.");
}
/// <summary>
/// Reads punctuator tokens as specified in
/// http://facebook.github.io/graphql/October2016/#sec-Punctuators
/// one of ! $ ( ) ... : = @ [ ] { | }
/// additionaly the reader will tokenize ampersands.
/// </summary>
/// <param name="state">
/// The lexer state.
/// </param>
/// <param name="previous">
/// The previous-token.
/// </param>
/// <param name="firstCode">
/// The first character of the punctuator.
/// </param>
/// <returns>
/// Returns the punctuator token read from the current lexer state.
/// </returns>
private static SyntaxToken ReadPunctuatorToken(
LexerState state,
SyntaxToken previous,
in char firstCode)