/**
 * Prompt text for the goal comprehension step (pure).
 *
 * Both system prompts are sent only on the nested clarifier calls, so they are
 * not part of Pi's always-on prompt budget. The model's job is to understand and
 * restate the user's goal — not to improve it — and, when it cannot yet, to ask
 * only what it needs from the user. The second call folds the answers into the
 * final restatement.
 */

import type { UserMessage } from "@earendil-works/pi-ai";
import { MAX_QUESTIONS, type ClarifyAnswer } from "./clarify-parse.ts";

/** The comprehension system prompt: understand the goal, ask only what is missing. */
export const CLARIFY_SYSTEM_PROMPT = `You are establishing a shared understanding of the user's goal for this session.

Reply with ONLY a JSON object, no prose and no code fence:
{
  "understood": boolean,
  "goal": "the goal as you understand it, in the user's own terms",
  "questions": [
    {
      "question": "what you need the user to tell you",
      "options": [{ "label": "an answer" }]
    }
  ]
}

Rules:
- Set "understood" to true when you know what the user wants to achieve well enough to act on it.
- "goal" restates the user's intent as one sentence: the outcome they want, not how to build it. Never add requirements, tools, files, or scope they did not state. If they already said it clearly, keep their wording.
- When "understood" is false, ask at most ${MAX_QUESTIONS} questions that resolve the ambiguity in intent — the smallest set whose answers would change what the work does.
- Ask only what only the user can answer: purpose, scope, preference, or priority. Never ask for a fact the work itself would reveal, and never ask the user to restate the goal.
- Give a question 2-4 concrete options when the answers are a small known set, or no options at all when free-form.`;

/** The re-comprehension system prompt: fold the answers into one goal statement. */
export const REFINE_SYSTEM_PROMPT = `The user has answered questions about their goal. Restate the goal as you now understand it.

Reply with ONLY the goal as one sentence, no prose and no code fence.
Use their answers and the original request; add nothing they did not state.`;

/** The user message sent to the clarifier alongside {@link CLARIFY_SYSTEM_PROMPT}. */
export function buildClarifyUserText(text: string): string {
	return `Understand this session goal:\n\n${text}`;
}

/** The request sent to the clarifier. */
export function buildClarifyMessages(
	text: string,
	now = Date.now(),
): { systemPrompt: string; messages: UserMessage[] } {
	return {
		systemPrompt: CLARIFY_SYSTEM_PROMPT,
		messages: [{ role: "user", content: [{ type: "text", text: buildClarifyUserText(text) }], timestamp: now }],
	};
}

/** The user message that carries the original request, the first restatement, and the answers. */
export function buildRefineUserText(original: string, goal: string, answers: readonly ClarifyAnswer[]): string {
	const lines = [`Original request:\n${original}`];
	if (goal) lines.push(`First restatement: ${goal}`);
	lines.push("The user was asked, and answered:");
	for (const item of answers) lines.push(`- ${item.question}\n  ${item.answer}`);
	return lines.join("\n");
}

/** The request sent to the clarifier after the user answers. */
export function buildRefineMessages(
	original: string,
	goal: string,
	answers: readonly ClarifyAnswer[],
	now = Date.now(),
): { systemPrompt: string; messages: UserMessage[] } {
	return {
		systemPrompt: REFINE_SYSTEM_PROMPT,
		messages: [
			{ role: "user", content: [{ type: "text", text: buildRefineUserText(original, goal, answers) }], timestamp: now },
		],
	};
}