// Phase 5B §2 — programs: first-class learning products (distinct from curriculum JSON, which
// stays just the content a program points at). CRUD here mirrors assessments.js's definition
// pattern (a slug primary key, a plain incrementing version, active/inactive status) rather
// than inventing a new convention.

async function listPrograms(pool, { activeOnly } = {}) {
  const { rows } = await pool.query(
    `SELECT p.*, count(e.enrollment_id)::int AS enrollment_count
     FROM programs p LEFT JOIN enrollments e ON e.program_id = p.program_id
     ${activeOnly ? "WHERE p.status = 'active'" : ''}
     GROUP BY p.program_id ORDER BY p.family, p.name`
  );
  return rows;
}

async function getProgram(pool, programId) {
  const { rows } = await pool.query(`SELECT * FROM programs WHERE program_id = $1`, [programId]);
  return rows[0] || null;
}

async function createProgram(pool, { programId, name, description, family, deliveryMode, curriculumPath, completionAssessmentId, estimatedDurationHours, createdBy }) {
  const { rows } = await pool.query(
    `INSERT INTO programs (program_id, name, description, family, delivery_mode, curriculum_path, completion_assessment_id, estimated_duration_hours, created_by)
     VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9) RETURNING *`,
    [programId, name, description || null, family, deliveryMode || 'self_paced', curriculumPath || 'rootnode-path', completionAssessmentId || null, estimatedDurationHours || null, createdBy || null]
  );
  return rows[0];
}

// Bumps version whenever a field an enrollment snapshots (curriculum_path, delivery_mode)
// actually changes — matches assessment_definitions' "edit later never changes what an
// already-drawn session is graded against" principle. Editing only cosmetic fields (name,
// description, estimated_duration_hours) does not bump the version.
async function updateProgram(pool, programId, fields) {
  const current = await getProgram(pool, programId);
  if (!current) return null;
  const snapshotChanged = (fields.curriculum_path && fields.curriculum_path !== current.curriculum_path)
    || (fields.delivery_mode && fields.delivery_mode !== current.delivery_mode);
  const map = { ...fields };
  if (snapshotChanged) map.version = current.version + 1;
  const cols = Object.keys(map);
  if (!cols.length) return current;
  const setClause = cols.map((c, i) => `${c} = $${i + 2}`).join(', ');
  const { rows } = await pool.query(
    `UPDATE programs SET ${setClause}, updated_at = now() WHERE program_id = $1 RETURNING *`,
    [programId, ...cols.map((c) => map[c])]
  );
  return rows[0];
}

module.exports = { listPrograms, getProgram, createProgram, updateProgram };