"""
Performance and Latency Tests
==============================
Tests for p95 latency thresholds, concurrent request handling, and SLA compliance.
"""
import pytest
import time
import statistics
import concurrent.futures
from typing import List


# Performance thresholds (in seconds)
THRESHOLDS = {
    "comparisons_p95": 0.5,      # 500ms for comparison reads
    "dashboard_p95": 0.3,        # 300ms for dashboard
    "export_p95": 2.0,           # 2000ms for exports
    "search_p95": 1.0,           # 1000ms for hotel search
    "auth_p95": 0.2,             # 200ms for auth operations
}

# Number of iterations for latency tests
LATENCY_ITERATIONS = 20


def calculate_p95(latencies: List[float]) -> float:
    """Calculate p95 latency from a list of latencies"""
    if not latencies:
        return 0.0
    sorted_latencies = sorted(latencies)
    index = int(len(sorted_latencies) * 0.95)
    return sorted_latencies[min(index, len(sorted_latencies) - 1)]


class TestLatencyThresholds:
    """Tests for API endpoint latency SLAs"""

    @pytest.mark.performance
    def test_comparisons_endpoint_p95_latency(self, client, auth_headers):
        """Test that comparisons endpoint meets p95 latency SLA"""
        latencies = []
        
        for _ in range(LATENCY_ITERATIONS):
            start = time.perf_counter()
            response = client.get("/api/comparisons", headers=auth_headers)
            end = time.perf_counter()
            
            if response.status_code in [200, 404]:
                latencies.append(end - start)
        
        if latencies:
            p95 = calculate_p95(latencies)
            avg = statistics.mean(latencies)
            
            print(f"Comparisons - p95: {p95*1000:.1f}ms, avg: {avg*1000:.1f}ms")
            assert p95 < THRESHOLDS["comparisons_p95"], f"p95 latency {p95:.3f}s exceeds threshold"

    @pytest.mark.performance
    def test_dashboard_endpoint_p95_latency(self, client, auth_headers):
        """Test that dashboard endpoint meets p95 latency SLA"""
        latencies = []
        
        for _ in range(LATENCY_ITERATIONS):
            start = time.perf_counter()
            response = client.get("/api/dashboard", headers=auth_headers)
            end = time.perf_counter()
            
            if response.status_code in [200, 403, 404]:
                latencies.append(end - start)
        
        if latencies:
            p95 = calculate_p95(latencies)
            print(f"Dashboard - p95: {p95*1000:.1f}ms")
            assert p95 < THRESHOLDS["dashboard_p95"], f"p95 latency {p95:.3f}s exceeds threshold"

    @pytest.mark.performance
    def test_export_endpoint_p95_latency(self, client, auth_headers):
        """Test that export endpoint meets p95 latency SLA"""
        latencies = []
        
        export_data = {
            "format": "excel",
            "data": [{"hotel": f"Hotel {i}", "price": 100 + i} for i in range(10)]
        }
        
        for _ in range(10):  # Fewer iterations for expensive operation
            start = time.perf_counter()
            response = client.post("/api/export", json=export_data, headers=auth_headers)
            end = time.perf_counter()
            
            if response.status_code in [200, 400, 422]:
                latencies.append(end - start)
        
        if latencies:
            p95 = calculate_p95(latencies)
            print(f"Export - p95: {p95*1000:.1f}ms")
            assert p95 < THRESHOLDS["export_p95"], f"p95 latency {p95:.3f}s exceeds threshold"

    @pytest.mark.performance
    def test_auth_endpoint_p95_latency(self, client):
        """Test that auth endpoints meet p95 latency SLA"""
        latencies = []
        
        for _ in range(LATENCY_ITERATIONS):
            start = time.perf_counter()
            response = client.get("/api/health")  # Lightweight auth check
            end = time.perf_counter()
            
            if response.status_code == 200:
                latencies.append(end - start)
        
        if latencies:
            p95 = calculate_p95(latencies)
            print(f"Health/Auth - p95: {p95*1000:.1f}ms")
            assert p95 < THRESHOLDS["auth_p95"], f"p95 latency {p95:.3f}s exceeds threshold"


class TestConcurrentRequests:
    """Tests for concurrent request handling"""

    @pytest.mark.performance
    def test_concurrent_reads(self, client, auth_headers):
        """Test that API handles concurrent read requests"""
        num_concurrent = 10
        
        def make_request():
            start = time.perf_counter()
            response = client.get("/api/dashboard", headers=auth_headers)
            end = time.perf_counter()
            return response.status_code, end - start
        
        with concurrent.futures.ThreadPoolExecutor(max_workers=num_concurrent) as executor:
            futures = [executor.submit(make_request) for _ in range(num_concurrent)]
            results = [f.result() for f in futures]
        
        # All requests should succeed or return consistent status
        status_codes = [r[0] for r in results]
        latencies = [r[1] for r in results]
        
        # Should not have server errors
        assert 500 not in status_codes
        
        # Average latency should still be reasonable
        avg_latency = statistics.mean(latencies)
        print(f"Concurrent reads - avg latency: {avg_latency*1000:.1f}ms")
        assert avg_latency < 2.0, "Concurrent request latency too high"

    @pytest.mark.performance
    def test_concurrent_writes(self, client, auth_headers):
        """Test that API handles concurrent write requests"""
        num_concurrent = 5  # Fewer concurrent writes
        
        def make_request(i):
            start = time.perf_counter()
            response = client.post("/api/export", json={
                "format": "excel",
                "data": [{"hotel": f"Test {i}", "price": 100}]
            }, headers=auth_headers)
            end = time.perf_counter()
            return response.status_code, end - start
        
        with concurrent.futures.ThreadPoolExecutor(max_workers=num_concurrent) as executor:
            futures = [executor.submit(make_request, i) for i in range(num_concurrent)]
            results = [f.result() for f in futures]
        
        status_codes = [r[0] for r in results]
        
        # Should not crash
        assert 500 not in status_codes

    @pytest.mark.performance
    def test_connection_pool_under_load(self, client, auth_headers):
        """Test that connection pooling handles load"""
        num_requests = 50
        successful = 0
        
        for _ in range(num_requests):
            response = client.get("/api/health")
            if response.status_code == 200:
                successful += 1
        
        success_rate = successful / num_requests
        print(f"Connection pool - success rate: {success_rate*100:.1f}%")
        assert success_rate >= 0.95, "Success rate too low under load"


class TestScraperPerformance:
    """Tests for scraper job performance"""

    @pytest.mark.performance
    def test_scrape_request_timeout(self, client, auth_headers):
        """Test that scrape requests have appropriate timeouts"""
        start = time.perf_counter()
        
        response = client.post("/api/scrape", json={
            "url": "https://example.com/slow-page"
        }, headers=auth_headers, timeout=30)
        
        end = time.perf_counter()
        elapsed = end - start
        
        # Should not take longer than timeout
        assert elapsed < 30, "Scrape request exceeded timeout"
        
        # Should return quickly with validation error or queued status
        if response.status_code != 404:
            assert elapsed < 5, "Scrape validation should be fast"

    @pytest.mark.performance
    def test_scraper_retry_backoff(self, client, auth_headers):
        """Test that scraper implements proper retry backoff"""
        # This is more of an integration test
        # Verifies that retries don't overwhelm the system
        
        response = client.post("/api/scrape", json={
            "url": "https://httpstat.us/503"  # Will return 503
        }, headers=auth_headers)
        
        # Should handle gracefully
        assert response.status_code != 500


class TestDatabasePerformance:
    """Tests for database query performance"""

    @pytest.mark.performance
    def test_user_lookup_performance(self, client, auth_headers):
        """Test that user lookup is fast"""
        latencies = []
        
        for _ in range(10):
            start = time.perf_counter()
            response = client.get("/api/auth/me", headers=auth_headers)
            end = time.perf_counter()
            
            if response.status_code == 200:
                latencies.append(end - start)
        
        if latencies:
            avg = statistics.mean(latencies)
            print(f"User lookup - avg: {avg*1000:.1f}ms")
            assert avg < 0.1, "User lookup too slow"

    @pytest.mark.performance
    def test_hotel_list_performance(self, client, auth_headers):
        """Test that hotel listing is performant"""
        latencies = []
        
        for _ in range(10):
            start = time.perf_counter()
            response = client.get("/api/hotels", headers=auth_headers)
            end = time.perf_counter()
            
            if response.status_code in [200, 404]:
                latencies.append(end - start)
        
        if latencies:
            avg = statistics.mean(latencies)
            print(f"Hotel list - avg: {avg*1000:.1f}ms")
            assert avg < 0.5, "Hotel listing too slow"


class TestResourceUsage:
    """Tests for resource usage patterns"""

    @pytest.mark.performance
    def test_memory_stable_under_load(self, client, auth_headers):
        """Test that memory usage is stable under repeated requests"""
        import gc
        
        # Force garbage collection before test
        gc.collect()
        
        # Make many requests
        for i in range(100):
            client.get("/api/health")
            
            if i % 20 == 0:
                gc.collect()
        
        # Should complete without memory issues
        # (Python's GC should handle this)

    @pytest.mark.performance
    def test_no_connection_leaks(self, client, auth_headers):
        """Test that connections are properly closed"""
        # Make requests in a loop
        for _ in range(50):
            response = client.get("/api/dashboard", headers=auth_headers)
            # Connection should be reused or properly closed
        
        # Final request should still work
        response = client.get("/api/health")
        assert response.status_code == 200


# Custom pytest markers
def pytest_configure(config):
    config.addinivalue_line(
        "markers", "performance: mark test as performance test"
    )
    config.addinivalue_line(
        "markers", "slow: mark test as slow running"
    )