// Tests for watcher diff logic
// We test the core diffing behaviour by exercising the internals directly
// without needing to spin up a real OGraph server.

import { describe, it, expect, vi, beforeEach } from 'vitest';
import type { DispatcherConfig, PendingEntry, OGraphEvent } from '../src/types.js';

// ── helpers ──────────────────────────────────────────────────────────────────

function makeConfig(overrides: Partial<DispatcherConfig['intervals']> = {}): DispatcherConfig {
  return {
    ograph: { endpoint: 'http://localhost', token: undefined, projections: [] },
    oc: { statusEndpoint: 'http://localhost', statusToken: 'tok', minAvailable: 2 },
    intervals: {
      watcherIdle: 30_000,
      watcherActive: 5_000,
      schedulerIdle: 60_000,
      schedulerActive: 5_000,
      cooldownAfterPush: 60_000,
      ...overrides,
    },
  };
}

// Minimal inline diff engine extracted from the watcher logic so we can unit-test
// it without I/O dependencies.
function runDiff(
  snapshot: Map<string, unknown>,
  current: Map<string, unknown>,
  pending: Map<string, PendingEntry>,
): { changed: boolean } {
  let changed = false;
  const now = Date.now();

  for (const [name, value] of current.entries()) {
    if (!snapshot.has(name)) {
      // first-run: initialise snapshot, no change
      snapshot.set(name, value);
      continue;
    }

    const prev = snapshot.get(name);
    if (JSON.stringify(prev) !== JSON.stringify(value)) {
      changed = true;
      const existing = pending.get(name);
      if (existing) {
        existing.currentValue = value;
        existing.lastDetectedAt = now;
        existing.changeCount += 1;
      } else {
        pending.set(name, {
          name,
          previousValue: prev,
          currentValue: value,
          firstDetectedAt: now,
          lastDetectedAt: now,
          changeCount: 1,
        });
      }
      snapshot.set(name, value);
    }
  }

  // projections that disappeared
  for (const name of snapshot.keys()) {
    if (!current.has(name)) {
      const prev = snapshot.get(name);
      if (prev !== undefined) {
        changed = true;
        snapshot.set(name, undefined);
        pending.set(name, {
          name,
          previousValue: prev,
          currentValue: undefined,
          firstDetectedAt: now,
          lastDetectedAt: now,
          changeCount: 1,
        });
      }
    }
  }

  return { changed };
}

// ── tests ─────────────────────────────────────────────────────────────────────

describe('watcher diff logic', () => {
  let snapshot: Map<string, unknown>;
  let pending: Map<string, PendingEntry>;

  beforeEach(() => {
    snapshot = new Map();
    pending = new Map();
  });

  it('first run: initialises snapshot without reporting changes', () => {
    const current = new Map([['proj-a', { count: 1 }]]);
    const { changed } = runDiff(snapshot, current, pending);

    expect(changed).toBe(false);
    expect(pending.size).toBe(0);
    expect(snapshot.get('proj-a')).toEqual({ count: 1 });
  });

  it('second run: no diff when value unchanged', () => {
    const current = new Map([['proj-a', { count: 1 }]]);
    runDiff(snapshot, current, pending); // first run — init
    const { changed } = runDiff(snapshot, current, pending); // second run — same value

    expect(changed).toBe(false);
    expect(pending.size).toBe(0);
  });

  it('detects a value change between runs', () => {
    const v1 = new Map([['proj-a', { count: 1 }]]);
    const v2 = new Map([['proj-a', { count: 2 }]]);

    runDiff(snapshot, v1, pending); // init
    const { changed } = runDiff(snapshot, v2, pending);

    expect(changed).toBe(true);
    expect(pending.has('proj-a')).toBe(true);
    expect(pending.get('proj-a')!.previousValue).toEqual({ count: 1 });
    expect(pending.get('proj-a')!.currentValue).toEqual({ count: 2 });
  });

  it('merges multiple changes into one pending entry', () => {
    runDiff(snapshot, new Map([['proj-a', 1]]), pending); // init
    runDiff(snapshot, new Map([['proj-a', 2]]), pending); // change 1
    runDiff(snapshot, new Map([['proj-a', 3]]), pending); // change 2

    expect(pending.get('proj-a')!.changeCount).toBe(2);
    expect(pending.get('proj-a')!.currentValue).toBe(3);
    expect(pending.get('proj-a')!.previousValue).toBe(1); // kept from first change
  });

  it('detects a disappeared projection', () => {
    runDiff(snapshot, new Map([['proj-a', 42]]), pending); // init
    const { changed } = runDiff(snapshot, new Map(), pending); // proj-a gone

    expect(changed).toBe(true);
    expect(pending.get('proj-a')!.currentValue).toBeUndefined();
  });

  it('does not re-fire when a disappeared projection stays absent', () => {
    runDiff(snapshot, new Map([['proj-a', 42]]), pending); // init
    runDiff(snapshot, new Map(), pending);                  // gone → change
    pending.clear();
    const { changed } = runDiff(snapshot, new Map(), pending); // still gone → no change

    expect(changed).toBe(false);
    expect(pending.size).toBe(0);
  });
});

// ── Event stream diff logic tests ───────────────────────────────────────────────────────────────────

// Helper function for testing event stream diff logic
function runEventDiff(
  lastSeenEventId: number,
  events: OGraphEvent[],
  eventTypes: string[] | undefined,
  pending: Map<string, PendingEntry>,
): { newLastSeenEventId: number; filtered: OGraphEvent[] } {
  // 过滤：只取 id > lastSeenEventId 的（client-side，因为 API 可能不支持 after）
  const newEvents = events.filter(e => e.id > lastSeenEventId);
  
  // 按 eventTypes 过滤（如果配置了）
  const filtered = eventTypes?.length 
    ? newEvents.filter(e => eventTypes.includes(e.type_name))
    : newEvents;
  
  let newLastSeenEventId = lastSeenEventId;
  if (filtered.length > 0) {
    // 更新 lastSeenEventId
    newLastSeenEventId = Math.max(...filtered.map(e => e.id));
    
    // 合并到 pending queue
    for (const event of filtered) {
      const key = `event:${event.type_name}:${event.id}`;
      pending.set(key, {
        name: `event:${event.type_name}`,
        previousValue: null,
        currentValue: event.payload,
        firstDetectedAt: Date.now(),
        lastDetectedAt: Date.now(),
        changeCount: 1,
        events: [event],
      });
    }
  }
  
  return { newLastSeenEventId, filtered };
}

describe('event stream diff logic', () => {
  let pending: Map<string, PendingEntry>;

  beforeEach(() => {
    pending = new Map();
  });

  it('filters events by lastSeenEventId', () => {
    const events: OGraphEvent[] = [
      { id: 1, type_hash: 'h1', type_name: 'task_created', payload: { id: 100 }, created_at: 1000 },
      { id: 2, type_hash: 'h2', type_name: 'task_updated', payload: { id: 101 }, created_at: 2000 },
      { id: 3, type_hash: 'h3', type_name: 'task_created', payload: { id: 102 }, created_at: 3000 },
    ];

    const { newLastSeenEventId, filtered } = runEventDiff(1, events, undefined, pending);

    expect(newLastSeenEventId).toBe(3);
    expect(filtered).toHaveLength(2);
    expect(filtered.map(e => e.id)).toEqual([2, 3]);
    expect(pending.size).toBe(2);
  });

  it('filters events by eventTypes when configured', () => {
    const events: OGraphEvent[] = [
      { id: 1, type_hash: 'h1', type_name: 'task_created', payload: { id: 100 }, created_at: 1000 },
      { id: 2, type_hash: 'h2', type_name: 'task_updated', payload: { id: 101 }, created_at: 2000 },
      { id: 3, type_hash: 'h3', type_name: 'user_login', payload: { user: 'alice' }, created_at: 3000 },
    ];

    const { filtered } = runEventDiff(0, events, ['task_created', 'task_updated'], pending);

    expect(filtered).toHaveLength(2);
    expect(filtered.map(e => e.type_name)).toEqual(['task_created', 'task_updated']);
    expect(pending.size).toBe(2);
  });

  it('handles empty event list gracefully', () => {
    const { newLastSeenEventId, filtered } = runEventDiff(5, [], undefined, pending);

    expect(newLastSeenEventId).toBe(5); // unchanged
    expect(filtered).toHaveLength(0);
    expect(pending.size).toBe(0);
  });

  it('creates pending entries with event metadata', () => {
    const events: OGraphEvent[] = [
      { id: 10, type_hash: 'h1', type_name: 'task_created', payload: { id: 200, title: 'Test' }, created_at: 1000 },
    ];

    runEventDiff(0, events, undefined, pending);

    const entry = pending.get('event:task_created:10');
    expect(entry).toBeDefined();
    expect(entry!.name).toBe('event:task_created');
    expect(entry!.currentValue).toEqual({ id: 200, title: 'Test' });
    expect(entry!.previousValue).toBeNull();
    expect(entry!.events).toHaveLength(1);
    expect(entry!.events![0].id).toBe(10);
  });
});