feat: grlx LSP server in Go

LSP server for grlx recipe files (.grlx) providing:

- Completion for ingredients, methods, properties, requisite types,
  and step ID references
- Diagnostics for unknown ingredients/methods, missing required
  properties, unknown properties, and invalid requisite types
- Hover documentation for all ingredients and methods with property
  tables
- Full schema for all 6 grlx ingredients (cmd, file, group, pkg,
  service, user) with accurate properties from the grlx source

internal/lsp/handler.go

@@ -0,0 +1,145 @@
+// Package lsp implements the Language Server Protocol handler for grlx recipes.
+package lsp
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+	"sync"
+
+	"go.lsp.dev/jsonrpc2"
+	"go.lsp.dev/protocol"
+
+	"github.com/gogrlx/grlx-lsp/internal/recipe"
+	"github.com/gogrlx/grlx-lsp/internal/schema"
+)
+
+// Handler implements the LSP server.
+type Handler struct {
+	conn     jsonrpc2.Conn
+	registry *schema.Registry
+	mu       sync.RWMutex
+	docs     map[string]*document // URI -> document
+}
+
+type document struct {
+	content string
+	recipe  *recipe.Recipe
+}
+
+// NewHandler creates a new LSP handler.
+func NewHandler(registry *schema.Registry) *Handler {
+	return &Handler{
+		registry: registry,
+		docs:     make(map[string]*document),
+	}
+}
+
+// SetConn sets the jsonrpc2 connection for sending notifications.
+func (h *Handler) SetConn(conn jsonrpc2.Conn) {
+	h.conn = conn
+}
+
+// Handle dispatches LSP requests.
+func (h *Handler) Handle(ctx context.Context, reply jsonrpc2.Replier, req jsonrpc2.Request) error {
+	switch req.Method() {
+	case "initialize":
+		return h.handleInitialize(ctx, reply, req)
+	case "initialized":
+		return reply(ctx, nil, nil)
+	case "shutdown":
+		return reply(ctx, nil, nil)
+	case "exit":
+		return reply(ctx, nil, nil)
+	case "textDocument/didOpen":
+		return h.handleDidOpen(ctx, reply, req)
+	case "textDocument/didChange":
+		return h.handleDidChange(ctx, reply, req)
+	case "textDocument/didClose":
+		return h.handleDidClose(ctx, reply, req)
+	case "textDocument/didSave":
+		return reply(ctx, nil, nil)
+	case "textDocument/completion":
+		return h.handleCompletion(ctx, reply, req)
+	case "textDocument/hover":
+		return h.handleHover(ctx, reply, req)
+	case "textDocument/diagnostic":
+		return reply(ctx, nil, nil)
+	default:
+		return reply(ctx, nil, jsonrpc2.NewError(jsonrpc2.MethodNotFound, "method not supported: "+req.Method()))
+	}
+}
+
+func (h *Handler) handleInitialize(_ context.Context, reply jsonrpc2.Replier, _ jsonrpc2.Request) error {
+	return reply(context.Background(), protocol.InitializeResult{
+		Capabilities: protocol.ServerCapabilities{
+			TextDocumentSync: protocol.TextDocumentSyncOptions{
+				OpenClose: true,
+				Change:    protocol.TextDocumentSyncKindFull,
+			},
+			CompletionProvider: &protocol.CompletionOptions{
+				TriggerCharacters: []string{".", ":", "-", " "},
+			},
+			HoverProvider: true,
+		},
+		ServerInfo: &protocol.ServerInfo{
+			Name:    "grlx-lsp",
+			Version: "0.1.0",
+		},
+	}, nil)
+}
+
+func (h *Handler) handleDidOpen(ctx context.Context, reply jsonrpc2.Replier, req jsonrpc2.Request) error {
+	var params protocol.DidOpenTextDocumentParams
+	if err := json.Unmarshal(req.Params(), &params); err != nil {
+		return reply(ctx, nil, err)
+	}
+	h.updateDocument(string(params.TextDocument.URI), params.TextDocument.Text)
+	h.publishDiagnostics(ctx, string(params.TextDocument.URI))
+	return reply(ctx, nil, nil)
+}
+
+func (h *Handler) handleDidChange(ctx context.Context, reply jsonrpc2.Replier, req jsonrpc2.Request) error {
+	var params protocol.DidChangeTextDocumentParams
+	if err := json.Unmarshal(req.Params(), &params); err != nil {
+		return reply(ctx, nil, err)
+	}
+	if len(params.ContentChanges) > 0 {
+		h.updateDocument(string(params.TextDocument.URI), params.ContentChanges[len(params.ContentChanges)-1].Text)
+		h.publishDiagnostics(ctx, string(params.TextDocument.URI))
+	}
+	return reply(ctx, nil, nil)
+}
+
+func (h *Handler) handleDidClose(_ context.Context, reply jsonrpc2.Replier, req jsonrpc2.Request) error {
+	var params protocol.DidCloseTextDocumentParams
+	if err := json.Unmarshal(req.Params(), &params); err != nil {
+		return reply(context.Background(), nil, err)
+	}
+	h.mu.Lock()
+	delete(h.docs, string(params.TextDocument.URI))
+	h.mu.Unlock()
+	return reply(context.Background(), nil, nil)
+}
+
+func (h *Handler) updateDocument(uri, content string) {
+	r := recipe.Parse([]byte(content))
+	h.mu.Lock()
+	h.docs[uri] = &document{content: content, recipe: r}
+	h.mu.Unlock()
+}
+
+func (h *Handler) getDocument(uri string) *document {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+	return h.docs[uri]
+}
+
+// lineAt returns the text of the given line (0-indexed).
+func lineAt(content string, line int) string {
+	lines := strings.Split(content, "\n")
+	if line < 0 || line >= len(lines) {
+		return ""
+	}
+	return lines[line]
+}