/**
 * Templates routes module.
 * 
 * Punkt 8: Uses transactions for template updates (delete+insert steps).
 * Punkt 6: Uses better-sqlite3 synchronous API.
 */
const express = require('express');
const db = require('../db');
const { auditLog } = require('../auditLog');
const { authMiddleware, adminMiddleware } = require('../middleware/auth');
const { validate, createTemplateSchema, updateTemplateSchema } = require('../middleware/validation');

const router = express.Router();

router.use(authMiddleware);

// List templates
router.get('/', async (req, res) => {
  const templates = await db.prepare('SELECT * FROM templates ORDER BY id DESC').all();
  if (templates.length === 0) return res.json([]);

  const templateIds = templates.map(t => t.id).filter(id => Number.isInteger(id));
  if (templateIds.length === 0) return res.json(templates.map(t => ({ ...t, steps: [] })));
  const placeholders = templateIds.map(() => '?').join(',');
  const steps = await db.prepare(`SELECT * FROM template_steps WHERE template_id IN (${placeholders}) ORDER BY step_order ASC`).all(...templateIds);

  const result = templates.map(t => ({
    ...t,
    steps: steps.filter(s => s.template_id === t.id)
  }));
  res.json(result);
});

// Create template (admin only) - Punkt 8: Transaction
router.post('/', adminMiddleware, validate(createTemplateSchema), async (req, res) => {
  const { name, description, is_assignable, allows_file_upload, ad_create, steps } = req.validatedBody;

  const assignable = is_assignable ? 1 : 0;
  const fileUpload = allows_file_upload ? 1 : 0;
  const adCreate = ad_create ? 1 : 0;

  // H2: Alle Statements innerhalb der Transaktion über txDb erzeugen
  // (fn erhält txDb als this) — sonst kein Rollback möglich.
  const createTemplate = db.transaction(async function () {
    const txDb = this;
    const insertTemplate = txDb.prepare('INSERT INTO templates (name, description, is_assignable, allows_file_upload, ad_create) VALUES (?, ?, ?, ?, ?)');
    const insertStep = txDb.prepare('INSERT INTO template_steps (template_id, page_num, label, type, step_order, email_domain, email_source_fields, dropdown_options, ad_field, hidden, ad_prefix) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)');

    const info = await insertTemplate.run(name, description, assignable, fileUpload, adCreate);
    const templateId = info.lastInsertRowid;

    for (const [idx, step] of steps.entries()) {
      await insertStep.run(
        templateId, step.page_num || 1, step.label, step.type, idx + 1,
        step.email_domain || null, step.email_source_fields || null,
        step.dropdown_options || null, step.ad_field || null,
        step.hidden ? 1 : 0, step.ad_prefix || null
      );
    }
    return templateId;
  });

  try {
    const templateId = await createTemplate();
    auditLog(req.user?.id, 'create_template', 'template', templateId, `Created template: ${name}`, req);
    res.status(201).json({ id: templateId, name, description, is_assignable: !!assignable, allows_file_upload: !!fileUpload, ad_create: !!adCreate, steps });
  } catch (err) {
    res.status(500).json({ error: 'Interner Serverfehler.' });
  }
});

// Update template (admin only) - Punkt 8: Transaction
router.put('/:id', adminMiddleware, validate(updateTemplateSchema), async (req, res) => {
  const templateId = parseInt(req.params.id);
  const { name, description, is_assignable, allows_file_upload, ad_create, steps } = req.validatedBody;

  const assignable = is_assignable ? 1 : 0;
  const fileUpload = allows_file_upload ? 1 : 0;
  const adCreate = ad_create ? 1 : 0;

  // H2: Statements innerhalb der Transaktion über txDb erzeugen
  const updateTemplateTransaction = db.transaction(async function () {
    const txDb = this;
    const updateTemplate = txDb.prepare('UPDATE templates SET name = ?, description = ?, is_assignable = ?, allows_file_upload = ?, ad_create = ? WHERE id = ?');
    const deleteSteps = txDb.prepare('DELETE FROM template_steps WHERE template_id = ?');
    const insertStep = txDb.prepare('INSERT INTO template_steps (template_id, page_num, label, type, step_order, email_domain, email_source_fields, dropdown_options, ad_field, hidden, ad_prefix) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)');

    const info = await updateTemplate.run(name, description, assignable, fileUpload, adCreate, templateId);
    if (info.changes === 0) throw new Error('NOT_FOUND');

    await deleteSteps.run(templateId);

    for (const [idx, step] of steps.entries()) {
      await insertStep.run(
        templateId, step.page_num || 1, step.label, step.type, idx + 1,
        step.email_domain || null, step.email_source_fields || null,
        step.dropdown_options || null, step.ad_field || null,
        step.hidden ? 1 : 0, step.ad_prefix || null
      );
    }
  });

  try {
    await updateTemplateTransaction();
    auditLog(req.user?.id, 'update_template', 'template', templateId, `Updated template: ${name}`, req);
    res.json({ id: templateId, name, description, is_assignable: !!assignable, allows_file_upload: !!fileUpload, ad_create: !!adCreate, steps });
  } catch (err) {
    if (err.message === 'NOT_FOUND') return res.status(404).json({ error: 'Vorlage nicht gefunden.' });
    res.status(500).json({ error: 'Interner Serverfehler.' });
  }
});

// Delete template (admin only)
router.delete('/:id', adminMiddleware, async (req, res) => {
  const templateId = parseInt(req.params.id);
  const info = await db.prepare('DELETE FROM templates WHERE id = ?').run(templateId);
  if (info.changes === 0) return res.status(404).json({ error: 'Vorlage nicht gefunden.' });
  auditLog(req.user?.id, 'delete_template', 'template', templateId, null, req);
  res.json({ message: 'Vorlage gelöscht.' });
});

module.exports = router;