feat: add the snippets plugin (B2)

plugins/snippets/src/frontend/snippet-variables.ts

@@ -0,0 +1,75 @@
+export interface SnippetInput {
+  key: string;
+  label: string;
+}
+
+export interface SnippetHostContext {
+  ip?: string;
+  username?: string;
+  port?: number | string;
+  name?: string;
+}
+
+const INPUT_PATTERN =
+  /\$\{INPUT_(\d+)(?::([^}$]+))?\}|\$INPUT_(\d+)(?![a-zA-Z0-9_])/g;
+
+export function extractSnippetInputs(content: string): SnippetInput[] {
+  const seen = new Map<string, SnippetInput>();
+  let match: RegExpExecArray | null;
+  INPUT_PATTERN.lastIndex = 0;
+  while ((match = INPUT_PATTERN.exec(content)) !== null) {
+    const digits = match[1] ?? match[3];
+    const key = `INPUT_${digits}`;
+    if (!seen.has(key)) {
+      seen.set(key, { key, label: match[2]?.trim() || `Input ${digits}` });
+    }
+  }
+  return Array.from(seen.values());
+}
+
+export function hasSnippetInputs(content: string): boolean {
+  INPUT_PATTERN.lastIndex = 0;
+  return INPUT_PATTERN.test(content);
+}
+
+function replaceVar(
+  content: string,
+  name: string,
+  value: string | undefined,
+): string {
+  if (value === undefined) return content;
+  const pattern = new RegExp(`\\$\\{?${name}\\}?`, "g");
+  return content.replace(pattern, value);
+}
+
+export function resolveSnippetContent(
+  content: string,
+  host: SnippetHostContext | null,
+  inputValues: Record<string, string> = {},
+): string {
+  let resolved = content;
+
+  resolved = replaceVar(resolved, "HOST", host?.ip);
+  resolved = replaceVar(resolved, "USER", host?.username);
+  resolved = replaceVar(
+    resolved,
+    "PORT",
+    host?.port !== undefined ? String(host.port) : undefined,
+  );
+  resolved = replaceVar(resolved, "NAME", host?.name);
+
+  resolved = resolved.replace(
+    INPUT_PATTERN,
+    (
+      fullMatch,
+      braceDigits: string | undefined,
+      _label,
+      plainDigits: string | undefined,
+    ) => {
+      const key = `INPUT_${braceDigits ?? plainDigits}`;
+      return key in inputValues ? inputValues[key] : fullMatch;
+    },
+  );
+
+  return resolved;
+}