feat: initial Lam Agent extension (#1)

src/lib/markdown.ts

@@ -0,0 +1,98 @@
+import type { ChatTurn } from "./types";
+
+/**
+ * Renders a turn as markdown for the detail panel.
+ *
+ * Kept as a pure function so the transcript layout can be tested without
+ * mounting a component, and so the same renderer can serve both a finished
+ * turn and one that is still streaming.
+ */
+
+export const STREAMING_CURSOR = "▍";
+
+export interface TurnMarkdownInput {
+  prompt: string;
+  response: string;
+  thinking?: string;
+  toolCalls?: ChatTurn["toolCalls"];
+  error?: string;
+  model?: string;
+  createdAt?: number;
+  isStreaming?: boolean;
+}
+
+/** Prefixes every line so a multi-line prompt renders as one continuous quote block. */
+function quote(text: string): string {
+  return text
+    .split("\n")
+    .map((line) => `> ${line}`.trimEnd())
+    .join("\n");
+}
+
+export function buildTurnMarkdown(input: TurnMarkdownInput): string {
+  const sections: string[] = [];
+
+  sections.push(quote(input.prompt));
+  sections.push("");
+
+  const body = input.response.trim() || (input.isStreaming ? "_Thinking…_" : "_No response._");
+  sections.push(input.isStreaming ? `${body} ${STREAMING_CURSOR}` : body);
+
+  if (input.error) {
+    sections.push("", `**Error** — ${input.error}`);
+  }
+
+  const toolCalls = input.toolCalls ?? [];
+  if (toolCalls.length > 0) {
+    const lines = toolCalls.map((call) => `- \`${call.name}\`${call.isError ? " — failed" : ""}`);
+    sections.push("", "**Tools used**", ...lines);
+  }
+
+  if (input.thinking && input.thinking.trim().length > 0) {
+    sections.push("", "---", "", "**Reasoning**", "", quote(input.thinking.trim()));
+  }
+
+  const footer: string[] = [];
+  if (input.model) footer.push(`\`${input.model}\``);
+  if (input.createdAt) footer.push(new Date(input.createdAt).toLocaleString());
+
+  if (footer.length > 0) {
+    sections.push("", "---", "", footer.join(" · "));
+  }
+
+  return sections.join("\n");
+}
+
+/** The placeholder shown while the first tokens are still in flight. */
+export function pendingMarkdown(prompt: string, status?: string): string {
+  const lines = [quote(prompt), ""];
+  lines.push(status ? `_${status}…_` : "_Thinking…_");
+  return lines.join("\n");
+}
+
+/** A short one-line preview of an answer, for a collapsed row. */
+export function previewText(text: string, max: number): string {
+  const collapsed = text.replace(/\s+/g, " ").trim();
+  if (collapsed.length <= max) return collapsed;
+  return `${collapsed.slice(0, Math.max(0, max - 1)).trimEnd()}…`;
+}
+
+/**
+ * Flattens a whole conversation into plain text for the clipboard.
+ *
+ * This has to load the full transcript rather than reuse the index summary —
+ * copying a truncated preview and calling it "the conversation" would be a
+ * quiet lie.
+ */
+export function sessionToPlainText(turns: ChatTurn[]): string {
+  if (turns.length === 0) return "";
+
+  return turns
+    .map((turn) => {
+      const header = `## ${turn.prompt}`;
+      const body = turn.response.trim() || (turn.error ? "" : "_(no response)_");
+      const failure = turn.error ? `\n\n**[error]** ${turn.error}` : "";
+      return `${header}\n\n${body}${failure}`;
+    })
+    .join("\n\n---\n\n");
+}