/**
 * LiveTurn — the minimal machine-edit ingress (spec §6.2): one @cline/sdk
 * Agent turn on the built-in `claude-code` provider, which rides the
 * operator's local Claude Code Pro/Max login — the extension holds NO
 * credentials of any kind (INV-8). vscode-free; the editSelection command
 * (extension.ts) feeds the result into the applyAgentEdit seam (INV-9).
 *
 * Like src/cline.ts: @cline/sdk is ESM-only, loaded via dynamic import(),
 * never bundled (esbuild keeps it external).
 */

export interface EditTurnResult {
  replacement: string;
  model: string;
  /** the SDK run id — recorded as provenance sessionId. */
  sessionId: string;
}

const SYSTEM_PROMPT = [
  "You are a precise text editor embedded in VS Code.",
  "You will be given a piece of text and an instruction.",
  "Respond with ONLY the edited replacement text — no explanation, no preamble,",
  "no markdown code fences. Preserve the original's leading/trailing whitespace",
  "unless the instruction says otherwise.",
].join(" ");

/**
 * Strip a wrapping markdown code fence if the model added one anyway.
 * If `selectedText` itself was fence-wrapped (i.e. the user's selection was a
 * fenced block), the model mirroring that format is correct — return
 * `outputText` unchanged so the fence is preserved.
 */
export function extractReplacement(outputText: string, selectedText: string): string {
  const fencePattern = /^\s*```[^\n]*\n[\s\S]*?\n?```\s*$/;
  if (fencePattern.test(selectedText)) return outputText;
  const m = outputText.match(/^\s*```[^\n]*\n([\s\S]*?)\n?```\s*$/);
  return m ? m[1] : outputText;
}

export async function runEditTurn(
  instruction: string,
  selectedText: string,
  opts?: { modelId?: string },
): Promise<EditTurnResult> {
  const sdk = await import("@cline/sdk");
  const modelId = opts?.modelId ?? "sonnet";
  const agent = new sdk.Agent({
    providerId: "claude-code",
    modelId,
    systemPrompt: SYSTEM_PROMPT,
  });
  const result = await agent.run(
    `<instruction>\n${instruction}\n</instruction>\n<text>\n${selectedText}\n</text>`,
  );
  // The SDK's AgentRunResult.status union is "completed" | "aborted" | "failed"
  // (@cline/shared agent.d.ts) — "completed" is the success status.
  if (result.status !== "completed") {
    throw new Error(
      `claude-code turn ${result.status}: ${result.error?.message ?? "unknown error"} ` +
        "(is Claude Code installed and signed in?)",
    );
  }
  return { replacement: extractReplacement(result.outputText, selectedText), model: modelId, sessionId: result.runId };
}