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// Copyright (c) 2017 Fabian Schuiki

use moore_common::errors::*;
use moore_common::source::*;


/// A generalized stream of tokens that accepts emission of diagnostics and
/// tracking of the severity of issues encountered.
pub trait TokenStream<T> {
	/// Look ahead at a token in the stream.
	fn peek(&mut self, offset: usize) -> Spanned<T>;

	/// Consume the current token.
	fn bump(&mut self);

	/// Skip the current token. Usually the same as `bump`, but may be used to
	/// keep skipped tokens out of the consumed tokens count by some parsers.
	fn skip(&mut self) {
		self.bump()
	}

	/// Get the number of tokens consumed. Excludes tokens skipped with `skip`.
	fn consumed(&self) -> usize;

	/// Get the span of the last token consumed token (bumped or skipped).
	fn last_span(&self) -> Span;

	/// Get the tail location of the last consumed token (bumped or skipped).
	fn last_loc(&self) -> Location {
		self.last_span().end()
	}

	/// Emit a diagnostic.
	fn emit(&mut self, diag: DiagBuilder2);

	/// Get the severity of the worst diagnostic emitted so far.
	fn severity(&self) -> Severity;

	/// Check whether a fatal diagnostic has been emitted.
	fn is_fatal(&self) -> bool {
		self.severity() >= Severity::Fatal
	}

	/// Check whether an error diagnostic has been emitted.
	fn is_error(&self) -> bool {
		self.severity() >= Severity::Error
	}
}