const express = require('express');
const router = express.Router();
const { getDb } = require('../models/db');
const { authMiddleware, adminMiddleware } = require('../middleware/auth');

module.exports = function(io) {

// ── Helpers ───────────────────────────────────────────────────────────────────

function postSysMsg(db, groupId, userId, content) {
  const r = db.prepare(`INSERT INTO messages (group_id, user_id, content, type) VALUES (?, ?, ?, 'system')`).run(groupId, userId, content);
  const msg = db.prepare(`
    SELECT m.*, u.name as user_name, u.display_name as user_display_name,
      u.avatar as user_avatar, u.role as user_role, u.status as user_status,
      u.hide_admin_tag as user_hide_admin_tag, u.about_me as user_about_me, u.allow_dm as user_allow_dm
    FROM messages m JOIN users u ON m.user_id = u.id WHERE m.id = ?
  `).get(r.lastInsertRowid);
  if (msg) { msg.reactions = []; io.to(`group:${groupId}`).emit('message:new', msg); }
}

function addUserToDmGroup(db, dmGroupId, userId, actorId) {
  db.prepare("INSERT OR IGNORE INTO group_members (group_id, user_id, joined_at) VALUES (?, ?, datetime('now'))").run(dmGroupId, userId);
  io.in(`user:${userId}`).socketsJoin(`group:${dmGroupId}`);
  const dmGroup = db.prepare('SELECT * FROM groups WHERE id = ?').get(dmGroupId);
  io.to(`user:${userId}`).emit('group:new', { group: dmGroup });
  const u = db.prepare('SELECT name, display_name FROM users WHERE id = ?').get(userId);
  postSysMsg(db, dmGroupId, actorId, `${u?.display_name || u?.name || 'A user'} has joined the conversation.`);
}

function removeUserFromDmGroup(db, dmGroupId, userId, actorId) {
  db.prepare('DELETE FROM group_members WHERE group_id = ? AND user_id = ?').run(dmGroupId, userId);
  io.in(`user:${userId}`).socketsLeave(`group:${dmGroupId}`);
  io.to(`user:${userId}`).emit('group:deleted', { groupId: dmGroupId });
  const u = db.prepare('SELECT name, display_name FROM users WHERE id = ?').get(userId);
  postSysMsg(db, dmGroupId, actorId, `${u?.display_name || u?.name || 'A user'} has been removed from the conversation.`);
}

// Get all user_ids for a user group
function getUserIdsForGroup(db, userGroupId) {
  return db.prepare('SELECT user_id FROM user_group_members WHERE user_group_id = ?').all(userGroupId).map(r => r.user_id);
}

// ── USER GROUPS ───────────────────────────────────────────────────────────────

router.get('/', authMiddleware, adminMiddleware, (req, res) => {
  const db = getDb();
  const groups = db.prepare(`
    SELECT ug.*,
      (SELECT COUNT(*) FROM user_group_members WHERE user_group_id = ug.id) as member_count
    FROM user_groups ug ORDER BY ug.name ASC
  `).all();
  res.json({ groups });
});

// ── MULTI-GROUP DMs ───────────────────────────────────────────────────────────

router.get('/multigroup', authMiddleware, adminMiddleware, (req, res) => {
  const db = getDb();
  const dms = db.prepare(`
    SELECT mgd.*,
      (SELECT COUNT(*) FROM multi_group_dm_members WHERE multi_group_dm_id = mgd.id) as group_count
    FROM multi_group_dms mgd ORDER BY mgd.name ASC
  `).all();
  // Attach member user group IDs
  for (const dm of dms) {
    dm.memberGroupIds = db.prepare('SELECT user_group_id FROM multi_group_dm_members WHERE multi_group_dm_id = ?').all(dm.id).map(r => r.user_group_id);
  }
  res.json({ dms });
});

router.post('/multigroup', authMiddleware, adminMiddleware, (req, res) => {
  const { name, userGroupIds = [] } = req.body;
  if (!name?.trim()) return res.status(400).json({ error: 'Name required' });
  if (userGroupIds.length < 2) return res.status(400).json({ error: 'At least two user groups required' });
  const db = getDb();
  if (db.prepare('SELECT id FROM multi_group_dms WHERE LOWER(name) = LOWER(?)').get(name.trim())) {
    return res.status(400).json({ error: 'Name already in use' });
  }
  const admin = db.prepare('SELECT id FROM users WHERE is_default_admin = 1').get();
  const dmResult = db.prepare(`INSERT INTO groups (name, type, owner_id, is_managed) VALUES (?, 'private', ?, 1)`).run(name.trim(), admin?.id || req.user.id);
  const dmGroupId = dmResult.lastInsertRowid;
  const mgResult = db.prepare(`INSERT INTO multi_group_dms (name, dm_group_id) VALUES (?, ?)`).run(name.trim(), dmGroupId);
  const mgId = mgResult.lastInsertRowid;

  const validGroupIds = userGroupIds.map(Number).filter(Boolean);
  const addedUsers = new Set();
  for (const ugId of validGroupIds) {
    db.prepare('INSERT OR IGNORE INTO multi_group_dm_members (multi_group_dm_id, user_group_id) VALUES (?, ?)').run(mgId, ugId);
    const uids = getUserIdsForGroup(db, ugId);
    for (const uid of uids) {
      if (!addedUsers.has(uid)) {
        addedUsers.add(uid);
        addUserToDmGroup(db, dmGroupId, uid, req.user.id);
      }
    }
    const ug = db.prepare('SELECT name FROM user_groups WHERE id = ?').get(ugId);
    if (ug) postSysMsg(db, dmGroupId, req.user.id, `Group "${ug.name}" has been added to this conversation.`);
  }

  const dm = db.prepare('SELECT * FROM multi_group_dms WHERE id = ?').get(mgId);
  dm.memberGroupIds = validGroupIds;
  res.json({ dm });
});

router.patch('/multigroup/:id', authMiddleware, adminMiddleware, (req, res) => {
  const db = getDb();
  const mg = db.prepare('SELECT * FROM multi_group_dms WHERE id = ?').get(req.params.id);
  if (!mg) return res.status(404).json({ error: 'Not found' });
  const { name, userGroupIds } = req.body;

  if (name && name.trim() !== mg.name) {
    if (db.prepare('SELECT id FROM multi_group_dms WHERE LOWER(name) = LOWER(?) AND id != ?').get(name.trim(), mg.id)) {
      return res.status(400).json({ error: 'Name already in use' });
    }
    db.prepare("UPDATE multi_group_dms SET name = ?, updated_at = datetime('now') WHERE id = ?").run(name.trim(), mg.id);
    if (mg.dm_group_id) {
      db.prepare("UPDATE groups SET name = ?, updated_at = datetime('now') WHERE id = ?").run(name.trim(), mg.dm_group_id);
    }
  }

  if (Array.isArray(userGroupIds) && mg.dm_group_id) {
    const newGroupIds = new Set(userGroupIds.map(Number).filter(Boolean));
    const currentGroupIds = new Set(db.prepare('SELECT user_group_id FROM multi_group_dm_members WHERE multi_group_dm_id = ?').all(mg.id).map(r => r.user_group_id));

    // Add new user groups
    for (const ugId of newGroupIds) {
      if (!currentGroupIds.has(ugId)) {
        db.prepare("INSERT OR IGNORE INTO multi_group_dm_members (multi_group_dm_id, user_group_id) VALUES (?, ?)").run(mg.id, ugId);
        const uids = getUserIdsForGroup(db, ugId);
        for (const uid of uids) addUserToDmGroup(db, mg.dm_group_id, uid, req.user.id);
        const ug = db.prepare('SELECT name FROM user_groups WHERE id = ?').get(ugId);
        if (ug) postSysMsg(db, mg.dm_group_id, req.user.id, `Group "${ug.name}" has been added to this conversation.`);
      }
    }
    // Remove dropped user groups
    for (const ugId of currentGroupIds) {
      if (!newGroupIds.has(ugId)) {
        db.prepare('DELETE FROM multi_group_dm_members WHERE multi_group_dm_id = ? AND user_group_id = ?').run(mg.id, ugId);
        const uids = getUserIdsForGroup(db, ugId);
        for (const uid of uids) {
          const stillInOtherGroup = db.prepare('SELECT 1 FROM multi_group_dm_members mgdm JOIN user_group_members ugm ON ugm.user_group_id = mgdm.user_group_id WHERE mgdm.multi_group_dm_id = ? AND ugm.user_id = ?').get(mg.id, uid);
          if (!stillInOtherGroup) removeUserFromDmGroup(db, mg.dm_group_id, uid, req.user.id);
        }
        const ug = db.prepare('SELECT name FROM user_groups WHERE id = ?').get(ugId);
        if (ug) postSysMsg(db, mg.dm_group_id, req.user.id, `Group "${ug.name}" has been removed from this conversation.`);
      }
    }
  }

  const updated = db.prepare('SELECT * FROM multi_group_dms WHERE id = ?').get(req.params.id);
  updated.memberGroupIds = db.prepare('SELECT user_group_id FROM multi_group_dm_members WHERE multi_group_dm_id = ?').all(mg.id).map(r => r.user_group_id);
  res.json({ dm: updated });
});

router.delete('/multigroup/:id', authMiddleware, adminMiddleware, (req, res) => {
  const db = getDb();
  const mg = db.prepare('SELECT * FROM multi_group_dms WHERE id = ?').get(req.params.id);
  if (!mg) return res.status(404).json({ error: 'Not found' });
  if (mg.dm_group_id) {
    const members = db.prepare('SELECT user_id FROM group_members WHERE group_id = ?').all(mg.dm_group_id).map(r => r.user_id);
    db.prepare('DELETE FROM groups WHERE id = ?').run(mg.dm_group_id);
    for (const uid of members) io.to(`user:${uid}`).emit('group:deleted', { groupId: mg.dm_group_id });
  }
  db.prepare('DELETE FROM multi_group_dms WHERE id = ?').run(mg.id);
  res.json({ success: true });
});

return router;
};

router.get('/:id', authMiddleware, adminMiddleware, (req, res) => {
  const db = getDb();
  const group = db.prepare('SELECT * FROM user_groups WHERE id = ?').get(req.params.id);
  if (!group) return res.status(404).json({ error: 'Not found' });
  const members = db.prepare(`
    SELECT u.id, u.name, u.display_name, u.avatar, u.role, u.status
    FROM user_group_members ugm JOIN users u ON u.id = ugm.user_id
    WHERE ugm.user_group_id = ? ORDER BY u.name ASC
  `).all(req.params.id);
  res.json({ group, members });
});

router.post('/', authMiddleware, adminMiddleware, (req, res) => {
  const { name, memberIds = [] } = req.body;
  if (!name?.trim()) return res.status(400).json({ error: 'Name required' });
  const db = getDb();
  if (db.prepare('SELECT id FROM user_groups WHERE LOWER(name) = LOWER(?)').get(name.trim())) {
    return res.status(400).json({ error: 'A group with that name already exists' });
  }
  const admin = db.prepare('SELECT id FROM users WHERE is_default_admin = 1').get();
  const dmResult = db.prepare(`
    INSERT INTO groups (name, type, owner_id, is_readonly, is_direct, is_managed)
    VALUES (?, 'private', ?, 0, 0, 1)
  `).run(name.trim(), admin?.id || req.user.id);
  const dmGroupId = dmResult.lastInsertRowid;
  const ugResult = db.prepare(`INSERT INTO user_groups (name, dm_group_id) VALUES (?, ?)`).run(name.trim(), dmGroupId);
  const ugId = ugResult.lastInsertRowid;

  const validIds = Array.isArray(memberIds) ? memberIds.map(Number).filter(Boolean) : [];
  for (const uid of validIds) {
    db.prepare("INSERT OR IGNORE INTO user_group_members (user_group_id, user_id) VALUES (?, ?)").run(ugId, uid);
    addUserToDmGroup(db, dmGroupId, uid, req.user.id);
  }
  const group = db.prepare('SELECT * FROM user_groups WHERE id = ?').get(ugId);
  res.json({ group });
});

router.patch('/:id', authMiddleware, adminMiddleware, (req, res) => {
  const db = getDb();
  const ug = db.prepare('SELECT * FROM user_groups WHERE id = ?').get(req.params.id);
  if (!ug) return res.status(404).json({ error: 'Not found' });
  const { name, memberIds } = req.body;

  if (name && name.trim() !== ug.name) {
    if (db.prepare('SELECT id FROM user_groups WHERE LOWER(name) = LOWER(?) AND id != ?').get(name.trim(), ug.id)) {
      return res.status(400).json({ error: 'Name already in use' });
    }
    db.prepare("UPDATE user_groups SET name = ?, updated_at = datetime('now') WHERE id = ?").run(name.trim(), ug.id);
    if (ug.dm_group_id) {
      db.prepare("UPDATE groups SET name = ?, updated_at = datetime('now') WHERE id = ?").run(name.trim(), ug.dm_group_id);
    }
  }

  if (Array.isArray(memberIds) && ug.dm_group_id) {
    const newIds = new Set(memberIds.map(Number).filter(Boolean));
    const current = db.prepare('SELECT user_id FROM user_group_members WHERE user_group_id = ?').all(ug.id).map(r => r.user_id);
    const currentSet = new Set(current);
    for (const uid of newIds) {
      if (!currentSet.has(uid)) {
        db.prepare("INSERT OR IGNORE INTO user_group_members (user_group_id, user_id) VALUES (?, ?)").run(ug.id, uid);
        addUserToDmGroup(db, ug.dm_group_id, uid, req.user.id);
        // Also add to any multi-group DMs that include this user group
        const mgDms = db.prepare('SELECT mgd.dm_group_id FROM multi_group_dm_members mgdm JOIN multi_group_dms mgd ON mgd.id = mgdm.multi_group_dm_id WHERE mgdm.user_group_id = ?').all(ug.id);
        for (const mg of mgDms) {
          if (mg.dm_group_id) addUserToDmGroup(db, mg.dm_group_id, uid, req.user.id);
        }
      }
    }
    for (const uid of currentSet) {
      if (!newIds.has(uid)) {
        db.prepare('DELETE FROM user_group_members WHERE user_group_id = ? AND user_id = ?').run(ug.id, uid);
        // Only remove from DM group if user isn't in another user group that also has access
        const otherUgMemberships = db.prepare(`
          SELECT ugm.user_group_id FROM user_group_members ugm
          WHERE ugm.user_id = ? AND ugm.user_group_id != ?
            AND EXISTS (SELECT 1 FROM group_members gm WHERE gm.group_id = ? AND gm.user_id = ?)
        `).all(uid, ug.id, ug.dm_group_id, uid);
        if (otherUgMemberships.length === 0) {
          removeUserFromDmGroup(db, ug.dm_group_id, uid, req.user.id);
          // Remove from multi-group DMs they got access through this group
          const mgDms = db.prepare('SELECT mgd.dm_group_id FROM multi_group_dm_members mgdm JOIN multi_group_dms mgd ON mgd.id = mgdm.multi_group_dm_id WHERE mgdm.user_group_id = ?').all(ug.id);
          for (const mg of mgDms) {
            if (mg.dm_group_id) {
              const stillMember = db.prepare('SELECT 1 FROM group_members WHERE group_id = ? AND user_id = ?').get(mg.dm_group_id, uid);
              if (stillMember) removeUserFromDmGroup(db, mg.dm_group_id, uid, req.user.id);
            }
          }
        }
      }
    }
  }

  const updated = db.prepare('SELECT * FROM user_groups WHERE id = ?').get(req.params.id);
  res.json({ group: updated });
});

router.delete('/:id', authMiddleware, adminMiddleware, (req, res) => {
  const db = getDb();
  const ug = db.prepare('SELECT * FROM user_groups WHERE id = ?').get(req.params.id);
  if (!ug) return res.status(404).json({ error: 'Not found' });
  if (ug.dm_group_id) {
    const members = db.prepare('SELECT user_id FROM group_members WHERE group_id = ?').all(ug.dm_group_id).map(r => r.user_id);
    db.prepare('DELETE FROM groups WHERE id = ?').run(ug.dm_group_id);
    for (const uid of members) io.to(`user:${uid}`).emit('group:deleted', { groupId: ug.dm_group_id });
  }
  db.prepare('DELETE FROM user_groups WHERE id = ?').run(ug.id);
  res.json({ success: true });
});