1 files changed, 91 insertions, 0 deletions
diff --git a/backend/lib/Support/TextDiagnostic.cpp b/backend/lib/Support/TextDiagnostic.cpp
new file mode 100644
index 0000000..1c027c3
--- /dev/null
+++ b/backend/lib/Support/TextDiagnostic.cpp
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/Support/TextDiagnostic.h"
+
+#include <algorithm>
+#include <iterator>
+#include <sstream>
+#include <utility>
+
+namespace rcc {
+
+std::string_view getDiagnosticSeverityName(DiagnosticSeverity Severity) noexcept {
+  switch (Severity) {
+  case DiagnosticSeverity::Note:
+    return "note";
+  case DiagnosticSeverity::Warning:
+    return "warning";
+  case DiagnosticSeverity::Error:
+    return "error";
+  }
+
+  return "unknown";
+}
+
+TextSource::TextSource(std::string Name, std::string Text)
+    : Name(std::move(Name)), Text(std::move(Text)), LineOffsets{0} {
+  for (std::size_t Index = 0; Index < this->Text.size(); ++Index) {
+    if (this->Text[Index] == '\n')
+      LineOffsets.push_back(Index + 1);
+  }
+}
+
+TextPosition TextSource::positionAt(std::size_t Offset) const noexcept {
+  Offset = std::min(Offset, Text.size());
+  const auto LineIterator = std::upper_bound(LineOffsets.begin(), LineOffsets.end(), Offset);
+  const std::size_t LineIndex =
+      static_cast<std::size_t>(std::distance(LineOffsets.begin(), LineIterator) - 1);
+  return TextPosition{
+      .Offset = Offset,
+      .Line = LineIndex + 1,
+      .Column = Offset - LineOffsets[LineIndex] + 1,
+  };
+}
+
+TextRange TextSource::range(std::size_t Begin, std::size_t End) const noexcept {
+  Begin = std::min(Begin, Text.size());
+  End = std::clamp(End, Begin, Text.size());
+  return TextRange{.Begin = positionAt(Begin), .End = positionAt(End)};
+}
+
+std::string_view TextSource::line(std::size_t OneBasedLine) const noexcept {
+  if (OneBasedLine == 0 || OneBasedLine > LineOffsets.size())
+    return {};
+
+  const std::size_t Begin = LineOffsets[OneBasedLine - 1];
+  std::size_t End = OneBasedLine < LineOffsets.size() ? LineOffsets[OneBasedLine] - 1 : Text.size();
+  if (End > Begin && Text[End - 1] == '\r')
+    --End;
+  return std::string_view(Text).substr(Begin, End - Begin);
+}
+
+std::string formatTextDiagnostic(const TextDiagnostic &Diagnostic, const TextSource &Source) {
+  std::ostringstream Output;
+  const TextPosition Position = Diagnostic.Range.Begin;
+  const std::string_view SourceName =
+      Diagnostic.SourceName.empty() ? Source.name() : std::string_view(Diagnostic.SourceName);
+
+  Output << SourceName << ':' << Position.Line << ':' << Position.Column << ": "
+         << getDiagnosticSeverityName(Diagnostic.Severity);
+  if (!Diagnostic.Category.empty())
+    Output << '[' << Diagnostic.Category << ']';
+  Output << ": " << Diagnostic.Message;
+
+  const std::string_view SourceLine = Source.line(Position.Line);
+  if (SourceLine.empty())
+    return Output.str();
+
+  Output << '\n' << SourceLine << '\n';
+  const std::size_t PrefixWidth = Position.Column > 0 ? Position.Column - 1 : 0;
+  for (std::size_t Index = 0; Index < PrefixWidth && Index < SourceLine.size(); ++Index)
+    Output << (SourceLine[Index] == '\t' ? '\t' : ' ');
+
+  Output << '^';
+  if (Diagnostic.Range.End.Line == Position.Line &&
+      Diagnostic.Range.End.Column > Position.Column + 1) {
+    Output << std::string(Diagnostic.Range.End.Column - Position.Column - 1, '~');
+  }
+  return Output.str();
+}
+
+} // namespace rcc