// lib/syncService.ts
import { getDatabase } from '@/lib/database';

// ── Types ─────────────────────────────────────────────────────────────────────

export interface SyncPartner {
  id: string;
  name: string;
  address: string; // IP:port
}

export interface Contact {
  id: string;
  owner_id: string;
  full_name: string;
  address?: string;
  household_count?: number;
  gender?: string;
  category: string;
  status?: string;
  tags?: string;
  notes?: string;
  territory_code?: string;
  latitude?: number;
  longitude?: number;
  created_at: number;
  updated_at: number;
  deleted_at?: number | null;
}

export interface Visit {
  id: string;
  contact_id: string;
  visited_by_name: string;
  visited_by_id: string;
  visit_date: number;
  topic?: string;
  response?: string;
  remarks?: string;
  next_visit_date?: number;
  created_at: number;
  updated_at: number;
}

export interface Territory {
  id: string;
  territory_code: string;
  municipality?: string;
  barangay?: string;
  area?: string;
  block?: string;
  assigned_to?: string;
  created_at: number;
  updated_at: number;
}

export interface SyncPayload {
  contacts: Contact[];
  visits: Visit[];
  territories: Territory[];
  exportedAt: number;
  exportedBy: string;
}

export interface SyncResult {
  sent: number;
  received: number;
  conflicts: number;
}

// ── STUB: mDNS Discovery ──────────────────────────────────────────────────────
// TODO: Implement with react-native-zeroconf in bare workflow (expo-dev-client).
// This requires native modules that are not available in managed Expo Go.
// Steps to activate:
// 1. Run `npx expo eject` or use a bare workflow
// 2. Install: npm install react-native-zeroconf
// 3. Run `npx pod-install` (iOS) and rebuild
// 4. Replace this stub with actual Zeroconf implementation

export async function discoverPartners(): Promise<SyncPartner[]> {
  // STUB — bare workflow required
  throw new Error(
    'mDNS discovery requires expo-dev-client and bare workflow. ' +
    'Install react-native-zeroconf after ejecting from managed workflow.'
  );
}

// ── STUB: TCP Sync Server ─────────────────────────────────────────────────────
// TODO: Implement with react-native-tcp-socket in bare workflow.
// Steps to activate:
// 1. Run `npx expo eject` or use a bare workflow
// 2. Install: npm install react-native-tcp-socket
// 3. Run `npx pod-install` (iOS) and rebuild
// 4. Replace this stub with actual TCP server implementation

export async function startSyncServer(port: number): Promise<void> {
  // STUB — bare workflow required
  throw new Error(
    'TCP server requires expo-dev-client and bare workflow. ' +
    'Install react-native-tcp-socket after ejecting from managed workflow.'
  );
}

// ── Merge Logic (FULLY IMPLEMENTED) ──────────────────────────────────────────

/**
 * Merges two arrays of records, resolving conflicts using updated_at timestamp.
 * - Latest updated_at wins per record (by id)
 * - Soft deletes (deleted_at != null) are respected
 */
export function mergeRecords<T extends {
  id: string;
  updated_at: number;
  deleted_at?: number | null;
}>(local: T[], remote: T[]): T[] {
  const merged = new Map<string, T>();

  // Load all local records
  for (const record of local) {
    merged.set(record.id, record);
  }

  // Merge remote records: remote wins if updated_at is newer or equal
  for (const remoteRecord of remote) {
    const localRecord = merged.get(remoteRecord.id);
    if (!localRecord) {
      // New record from remote
      merged.set(remoteRecord.id, remoteRecord);
    } else {
      // Conflict: pick the most recently updated
      if (remoteRecord.updated_at >= localRecord.updated_at) {
        merged.set(remoteRecord.id, remoteRecord);
      }
      // else: keep local (it's newer)
    }
  }

  return Array.from(merged.values());
}

// ── Serialize for Sync (FULLY IMPLEMENTED) ────────────────────────────────────

/**
 * Serializes local data into a SyncPayload for transmission.
 */
export function serializeForSync(
  contacts: Contact[],
  visits: Visit[],
  territories: Territory[],
  exportedBy: string
): SyncPayload {
  return {
    contacts,
    visits,
    territories,
    exportedAt: Math.floor(Date.now() / 1000),
    exportedBy,
  };
}

// ── Apply Incoming Sync (FULLY IMPLEMENTED) ────────────────────────────────────

/**
 * Applies a received SyncPayload to the local database.
 * Merges records using updated_at conflict resolution.
 * Returns a SyncResult with counts.
 */
export async function applyIncomingSync(
  payload: SyncPayload,
  localUserId: string
): Promise<SyncResult> {
  const db = await getDatabase();
  let received = 0;
  let conflicts = 0;

  // ── Territories ────────────────────────────────────────────────────────────
  const localTerritories = await db.getAllAsync<Territory>(
    'SELECT * FROM territories'
  );
  const mergedTerritories = mergeRecords(localTerritories, payload.territories);

  for (const territory of mergedTerritories) {
    const existing = localTerritories.find((t) => t.id === territory.id);
    if (existing) {
      if (territory.updated_at > existing.updated_at) {
        conflicts++;
        await db.runAsync(
          `UPDATE territories SET
            territory_code=?, municipality=?, barangay=?, area=?, block=?,
            assigned_to=?, updated_at=?
          WHERE id=?`,
          [
            territory.territory_code,
            territory.municipality ?? null,
            territory.barangay ?? null,
            territory.area ?? null,
            territory.block ?? null,
            territory.assigned_to ?? null,
            territory.updated_at,
            territory.id,
          ]
        );
        received++;
      }
    } else {
      await db.runAsync(
        `INSERT OR IGNORE INTO territories
          (id, territory_code, municipality, barangay, area, block, assigned_to, created_at, updated_at)
         VALUES (?,?,?,?,?,?,?,?,?)`,
        [
          territory.id,
          territory.territory_code,
          territory.municipality ?? null,
          territory.barangay ?? null,
          territory.area ?? null,
          territory.block ?? null,
          territory.assigned_to ?? null,
          territory.created_at,
          territory.updated_at,
        ]
      );
      received++;
    }
  }

  // ── Contacts ───────────────────────────────────────────────────────────────
  const localContacts = await db.getAllAsync<Contact>(
    'SELECT * FROM contacts'
  );
  const mergedContacts = mergeRecords(localContacts, payload.contacts);

  for (const contact of mergedContacts) {
    const existing = localContacts.find((c) => c.id === contact.id);
    if (existing) {
      if (contact.updated_at > existing.updated_at) {
        conflicts++;
        await db.runAsync(
          `UPDATE contacts SET
            owner_id=?, full_name=?, address=?, household_count=?, gender=?,
            category=?, status=?, tags=?, notes=?, territory_code=?,
            latitude=?, longitude=?, updated_at=?, deleted_at=?
          WHERE id=?`,
          [
            contact.owner_id,
            contact.full_name,
            contact.address ?? null,
            contact.household_count ?? 1,
            contact.gender ?? null,
            contact.category,
            contact.status ?? 'Active',
            contact.tags ?? '[]',
            contact.notes ?? null,
            contact.territory_code ?? null,
            contact.latitude ?? null,
            contact.longitude ?? null,
            contact.updated_at,
            contact.deleted_at ?? null,
            contact.id,
          ]
        );
        received++;
      }
    } else {
      await db.runAsync(
        `INSERT OR IGNORE INTO contacts
          (id, owner_id, full_name, address, household_count, gender, category,
           status, tags, notes, territory_code, latitude, longitude,
           created_at, updated_at, deleted_at)
         VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)`,
        [
          contact.id,
          contact.owner_id,
          contact.full_name,
          contact.address ?? null,
          contact.household_count ?? 1,
          contact.gender ?? null,
          contact.category,
          contact.status ?? 'Active',
          contact.tags ?? '[]',
          contact.notes ?? null,
          contact.territory_code ?? null,
          contact.latitude ?? null,
          contact.longitude ?? null,
          contact.created_at,
          contact.updated_at,
          contact.deleted_at ?? null,
        ]
      );
      received++;
    }
  }

  // ── Visits ─────────────────────────────────────────────────────────────────
  const localVisits = await db.getAllAsync<Visit>(
    'SELECT * FROM visits'
  );
  const mergedVisits = mergeRecords(
    localVisits.map((v) => ({ ...v, deleted_at: undefined })),
    payload.visits.map((v) => ({ ...v, deleted_at: undefined }))
  );

  for (const visit of mergedVisits) {
    const existing = localVisits.find((v) => v.id === visit.id);
    if (existing) {
      if (visit.updated_at > existing.updated_at) {
        conflicts++;
        await db.runAsync(
          `UPDATE visits SET
            contact_id=?, visited_by_name=?, visited_by_id=?, visit_date=?,
            topic=?, response=?, remarks=?, next_visit_date=?, updated_at=?
          WHERE id=?`,
          [
            visit.contact_id,
            visit.visited_by_name,
            visit.visited_by_id,
            visit.visit_date,
            visit.topic ?? null,
            visit.response ?? null,
            visit.remarks ?? null,
            visit.next_visit_date ?? null,
            visit.updated_at,
            visit.id,
          ]
        );
        received++;
      }
    } else {
      await db.runAsync(
        `INSERT OR IGNORE INTO visits
          (id, contact_id, visited_by_name, visited_by_id, visit_date,
           topic, response, remarks, next_visit_date, created_at, updated_at)
         VALUES (?,?,?,?,?,?,?,?,?,?,?)`,
        [
          visit.id,
          visit.contact_id,
          visit.visited_by_name,
          visit.visited_by_id,
          visit.visit_date,
          visit.topic ?? null,
          visit.response ?? null,
          visit.remarks ?? null,
          visit.next_visit_date ?? null,
          visit.created_at,
          visit.updated_at,
        ]
      );
      received++;
    }
  }

  return {
    sent: 0, // sent is tracked by the caller
    received,
    conflicts,
  };
}

// ── Local data fetch helpers ───────────────────────────────────────────────────

export async function getLocalSyncData(): Promise<{
  contacts: Contact[];
  visits: Visit[];
  territories: Territory[];
}> {
  const db = await getDatabase();
  const contacts = await db.getAllAsync<Contact>('SELECT * FROM contacts WHERE deleted_at IS NULL');
  const visits = await db.getAllAsync<Visit>('SELECT * FROM visits');
  const territories = await db.getAllAsync<Territory>('SELECT * FROM territories');
  return { contacts, visits, territories };
}

// ── Sync Log helpers ──────────────────────────────────────────────────────────

export interface SyncLogEntry {
  id: string;
  partner_id: string;
  partner_name: string | null;
  synced_at: number;
  sent_count: number;
  received_count: number;
}

export async function getSyncHistory(): Promise<SyncLogEntry[]> {
  const db = await getDatabase();
  return db.getAllAsync<SyncLogEntry>(
    'SELECT * FROM sync_log ORDER BY synced_at DESC LIMIT 50'
  );
}

export async function recordSync(
  partnerId: string,
  partnerName: string | null,
  sentCount: number,
  receivedCount: number
): Promise<void> {
  const db = await getDatabase();
  const id = `sync_${Date.now()}`;
  await db.runAsync(
    'INSERT INTO sync_log (id, partner_id, partner_name, synced_at, sent_count, received_count) VALUES (?,?,?,?,?,?)',
    [id, partnerId, partnerName, Math.floor(Date.now() / 1000), sentCount, receivedCount]
  );
}