import * as db from './db';
import { callLLM, cachedSystem } from './llm';
import { EMIT_THEME_SESSION_TOOL } from './llmTools';

const THEME_SESSION_SYSTEM = `You are an expert learning content writer for Respellion, an internal IT company.
You produce theme-level weekly learning sessions for the perpetual 26-week curriculum.
A weekly session is a single, coherent piece of learning that covers every topic the curriculum has slotted for that week's theme — not a list of separate articles.
Write in clear, professional English. Each topic section must be detailed (at least four sentences) and include a concrete workplace example or application.
Emit content only through the emit_theme_session tool.`;

function buildUserPrompt(weekContent) {
  const topicLines = weekContent.topics
    .map((t, idx) => `${idx + 1}. id=${t.id} | label="${t.label}" | type=${t.type} | description=${t.description}`)
    .join('\n');

  return `Theme: ${weekContent.theme}
Week ${weekContent.weekNumber} of the 26-week curriculum.
Estimated duration: ${weekContent.estimatedDuration || 30} minutes.
Rationale for this week's position: ${weekContent.rationale || '—'}

Topics in this theme this week (you MUST cover every one of them, one section each, reusing the exact topic_id):
${topicLines}

Produce a detailed theme session that synthesises these topics into a single coherent learning experience. Cover every topic in its own section, finish with a "how these connect" paragraph, and at least 3 takeaways for the theme.`;
}

/**
 * Get the cached theme session for the active curriculum version + week,
 * or generate one with the LLM and cache it.
 *
 * @param {string} curriculumVersionId — id of the active curriculum_versions row
 * @param {object} weekContent — output of getCurrentWeekContent: { weekNumber, theme, topics[], estimatedDuration, rationale }
 * @param {object} [opts]
 * @param {boolean} [opts.force=false] — regenerate even if cached
 */
export async function getOrGenerateThemeSession(curriculumVersionId, weekContent, { force = false } = {}) {
  if (!curriculumVersionId) throw new Error('Theme session requires an active curriculum version.');
  if (!weekContent || !Array.isArray(weekContent.topics) || weekContent.topics.length === 0) {
    throw new Error('Theme session requires at least one topic for the week.');
  }

  if (!force) {
    const cached = await db.getThemeSession(curriculumVersionId, weekContent.weekNumber);
    if (cached) return cached;
  }

  const result = await callLLM({
    task: 'theme_session.generate',
    tier: 'standard',
    system: cachedSystem(THEME_SESSION_SYSTEM),
    user: buildUserPrompt(weekContent),
    tools: [EMIT_THEME_SESSION_TOOL],
    toolChoice: { type: 'tool', name: EMIT_THEME_SESSION_TOOL.name },
    maxTokens: 8192,
    timeoutMs: 180_000,
  });

  const emitted = result.toolUses[0]?.input;
  if (!emitted) throw new Error('AI did not return a theme session. Please try again.');

  return db.setThemeSession(curriculumVersionId, weekContent.weekNumber, weekContent.theme, emitted);
}