Method handleSignatureHelp

pkg/lsp/handler.go:1331–1360

handleSignatureHelp provides signature help for SQL functions. This handler displays function parameter information when the user types an opening parenthesis or comma. It helps users understand function signatures without leaving their editor. Supported Functions (20+): - Aggregates: COUNT, SUM,

(params json.RawMessage)

//   - Empty SignatureHelp if cursor not in function call
//   - Error if document not found or params invalid
func (h *Handler) handleSignatureHelp(params json.RawMessage) (*SignatureHelp, error) {
	var p TextDocumentPositionParams
	if err := json.Unmarshal(params, &p); err != nil {
		return nil, err
	}

	doc, ok := h.server.Documents().Get(p.TextDocument.URI)
	if !ok {
		return &SignatureHelp{}, nil
	}

	// Get the function name at position
	content := doc.Content
	funcName, paramIndex := h.getFunctionAtPosition(content, p.Position)
	if funcName == "" {
		return &SignatureHelp{}, nil
	}

	// Look up function signature
	sig := getSQLFunctionSignature(strings.ToUpper(funcName))
	if sig == nil {
		return &SignatureHelp{}, nil
	}

	return &SignatureHelp{
		Signatures:      []SignatureInformation{*sig},
		ActiveSignature: 0,
		ActiveParameter: paramIndex,
	}, nil
}

// getFunctionAtPosition finds the function name and parameter index at a position
func (h *Handler) getFunctionAtPosition(content string, pos Position) (string, int) {