//! Network Error Handling Tests
//!
//! This module provides comprehensive tests for network error scenarios that
//! LLM clients might encounter in production environments. These tests ensure
//! robust error handling and proper recovery mechanisms.
//!
//! ## Test Categories
//!
//! 1. **Connection Failures**: DNS resolution failures, connection refused,
//!    network unreachable, etc.
//!
//! 2. **Timeout Scenarios**: Connection timeouts, read timeouts, request timeouts
//!
//! 3. **SSL/TLS Issues**: Certificate validation failures, protocol mismatches
//!
//! 4. **HTTP Protocol Errors**: Malformed responses, unexpected status codes,
//!    incomplete responses
//!
//! 5. **Intermittent Failures**: Network instability, packet loss simulation
//!
//! 6. **Resource Exhaustion**: Port exhaustion, memory pressure scenarios

use std::time::{Duration, Instant};

use reqwest::Client;
use serde_json::{Value, json};
use tokio::time::timeout;

mod mock_framework;
use mock_framework::{MockLlmServer, MockTestUtils};

/// Network error test configuration
#[derive(Debug, Clone)]
pub struct NetworkErrorTestConfig {
    /// Timeout for individual requests
    pub request_timeout: Duration,
    /// Number of retry attempts
    pub retry_attempts: usize,
    /// Delay between retries
    pub retry_delay: Duration,
    /// Whether to test with concurrent requests
    pub test_concurrency: bool,
    /// Number of concurrent requests for concurrency tests
    pub concurrent_requests: usize,
}

impl Default for NetworkErrorTestConfig {
    fn default() -> Self {
        Self {
            request_timeout: Duration::from_secs(5),
            retry_attempts: 3,
            retry_delay: Duration::from_millis(100),
            test_concurrency: false,
            concurrent_requests: 5,
        }
    }
}

/// Results from network error tests
#[derive(Debug)]
pub struct NetworkErrorTestResults {
    /// Test name
    pub test_name: String,
    /// Whether the test passed
    pub passed: bool,
    /// Error message if test failed
    pub error_message: Option<String>,
    /// Time taken for the test
    pub duration: Duration,
    /// Number of requests made
    pub requests_made: usize,
    /// Number of expected errors caught
    pub expected_errors_caught: usize,
    /// Any unexpected behaviors observed
    pub unexpected_behaviors: Vec<String>,
}

impl NetworkErrorTestResults {
    pub fn new(test_name: &str) -> Self {
        Self {
            test_name: test_name.to_string(),
            passed: false,
            error_message: None,
            duration: Duration::ZERO,
            requests_made: 0,
            expected_errors_caught: 0,
            unexpected_behaviors: Vec::new(),
        }
    }

    pub fn success(mut self) -> Self {
        self.passed = true;
        self
    }

    pub fn failure(mut self, message: &str) -> Self {
        self.passed = false;
        self.error_message = Some(message.to_string());
        self
    }

    pub fn with_duration(mut self, duration: Duration) -> Self {
        self.duration = duration;
        self
    }

    pub fn with_requests(mut self, count: usize) -> Self {
        self.requests_made = count;
        self
    }

    pub fn with_expected_errors(mut self, count: usize) -> Self {
        self.expected_errors_caught = count;
        self
    }
}

/// Network error test runner
pub struct NetworkErrorTester {
    config: NetworkErrorTestConfig,
}

impl NetworkErrorTester {
    pub fn new(config: NetworkErrorTestConfig) -> Self {
        Self { config }
    }

    /// Test connection timeout scenarios
    pub async fn test_connection_timeout(&self) -> NetworkErrorTestResults {
        let mut results = NetworkErrorTestResults::new("connection_timeout");
        let start_time = Instant::now();

        println!("⏱️  Testing connection timeout scenarios...");

        // Test with a non-routable IP address (should timeout)
        let client = Client::builder()
            .timeout(Duration::from_millis(500))
            .connect_timeout(Duration::from_millis(200))
            .build()
            .unwrap();

        let mut timeout_errors = 0;
        let test_urls = [
            "http://10.255.255.1:80/test", // Non-routable IP
            "http://192.0.2.1:80/test",    // TEST-NET-1 (RFC 5737)
            "http://198.51.100.1:80/test", // TEST-NET-2 (RFC 5737)
        ];

        for (i, url) in test_urls.iter().enumerate() {
            println!("  🔗 Testing timeout with URL {}: {}", i + 1, url);

            let request_start = Instant::now();
            let result = timeout(
                self.config.request_timeout,
                client
                    .post(*url)
                    .header("authorization", "Bearer test-key")
                    .json(&json!({
                        "model": "gpt-3.5-turbo",
                        "messages": [{"role": "user", "content": "test"}]
                    }))
                    .send(),
            )
            .await;

            let request_duration = request_start.elapsed();
            results.requests_made += 1;

            match result {
                Err(_) => {
                    // Timeout occurred as expected
                    timeout_errors += 1;
                    println!(
                        "    ✅ Timeout occurred as expected after {:?}",
                        request_duration
                    );
                }
                Ok(Ok(response)) => {
                    results.unexpected_behaviors.push(format!(
                        "Unexpected successful response from {}: {}",
                        url,
                        response.status()
                    ));
                    println!("    ⚠️  Unexpected success from {}", url);
                }
                Ok(Err(e)) => {
                    // Network error occurred (also acceptable)
                    timeout_errors += 1;
                    println!("    ✅ Network error as expected: {}", e);
                }
            }
        }

        results.expected_errors_caught = timeout_errors;
        results.duration = start_time.elapsed();

        if timeout_errors >= 2 && results.unexpected_behaviors.is_empty() {
            results.success()
        } else {
            let error_msg = format!(
                "Expected at least 2 timeout errors, got {}. Unexpected behaviors: {:?}",
                timeout_errors, results.unexpected_behaviors
            );
            results.failure(&error_msg)
        }
    }

    /// Test DNS resolution failures
    pub async fn test_dns_resolution_failure(&self) -> NetworkErrorTestResults {
        let mut results = NetworkErrorTestResults::new("dns_resolution_failure");
        let start_time = Instant::now();

        println!("🌐 Testing DNS resolution failures...");

        let client = Client::builder()
            .timeout(self.config.request_timeout)
            .build()
            .unwrap();

        let invalid_domains = [
            "http://this-domain-definitely-does-not-exist-12345.com/api",
            "http://invalid-tld.invalidtld/api",
            "http://nonexistent-subdomain.example.com/api",
        ];

        let mut dns_errors = 0;

        for (i, url) in invalid_domains.iter().enumerate() {
            println!("  🔍 Testing DNS failure with domain {}: {}", i + 1, url);

            let result = client
                .post(*url)
                .header("authorization", "Bearer test-key")
                .json(&json!({
                    "model": "gpt-3.5-turbo",
                    "messages": [{"role": "user", "content": "test"}]
                }))
                .send()
                .await;

            results.requests_made += 1;

            match result {
                Err(e) => {
                    if e.is_connect()
                        || e.to_string().contains("dns")
                        || e.to_string().contains("resolve")
                        || e.to_string().contains("name")
                    {
                        dns_errors += 1;
                        println!("    ✅ DNS error as expected: {}", e);
                    } else {
                        results
                            .unexpected_behaviors
                            .push(format!("Unexpected error type from {}: {}", url, e));
                        println!("    ⚠️  Unexpected error type: {}", e);
                    }
                }
                Ok(response) => {
                    let status = response.status().as_u16();
                    // Accept 502 Bad Gateway as a valid DNS-related error
                    if status == 502 || status >= 500 {
                        dns_errors += 1;
                        println!("    ✅ DNS-related server error as expected: {}", status);
                    } else {
                        results.unexpected_behaviors.push(format!(
                            "Unexpected successful response from {}: {}",
                            url,
                            response.status()
                        ));
                        println!("    ⚠️  Unexpected success from {}", url);
                    }
                }
            }
        }

        results.expected_errors_caught = dns_errors;
        results.duration = start_time.elapsed();

        if dns_errors >= 2 && results.unexpected_behaviors.is_empty() {
            results.success()
        } else {
            let error_msg = format!(
                "Expected at least 2 DNS errors, got {}. Unexpected behaviors: {:?}",
                dns_errors, results.unexpected_behaviors
            );
            results.failure(&error_msg)
        }
    }

    /// Test malformed response handling
    pub async fn test_malformed_response_handling(&self) -> NetworkErrorTestResults {
        let mut results = NetworkErrorTestResults::new("malformed_response_handling");
        let start_time = Instant::now();

        println!("📦 Testing malformed response handling...");

        let server = MockLlmServer::new().await;

        // Configure server to return malformed JSON
        server.configure(MockTestUtils::malformed_json_config());
        server.setup_openai_chat().await;

        let client = Client::builder()
            .timeout(self.config.request_timeout)
            .build()
            .unwrap();

        let mut parse_errors = 0;
        let test_count = 3;

        for i in 0..test_count {
            println!("  📄 Testing malformed response {}", i + 1);

            let result = client
                .post(format!("{}/v1/chat/completions", server.base_url()))
                .header("authorization", "Bearer test-key")
                .json(&json!({
                    "model": "gpt-3.5-turbo",
                    "messages": [{"role": "user", "content": format!("test {}", i)}]
                }))
                .send()
                .await;

            results.requests_made += 1;

            match result {
                Ok(response) => {
                    // Try to parse the response as JSON
                    let json_result = response.json::<Value>().await;
                    match json_result {
                        Err(e) => {
                            parse_errors += 1;
                            println!("    ✅ JSON parse error as expected: {}", e);
                        }
                        Ok(value) => {
                            results
                                .unexpected_behaviors
                                .push(format!("Unexpected successful JSON parse: {:?}", value));
                            println!("    ⚠️  Unexpected successful JSON parse");
                        }
                    }
                }
                Err(e) => {
                    results
                        .unexpected_behaviors
                        .push(format!("Unexpected request error: {}", e));
                    println!("    ⚠️  Unexpected request error: {}", e);
                }
            }
        }

        results.expected_errors_caught = parse_errors;
        results.duration = start_time.elapsed();

        if parse_errors == test_count && results.unexpected_behaviors.is_empty() {
            results.success()
        } else {
            let error_msg = format!(
                "Expected {} parse errors, got {}. Unexpected behaviors: {:?}",
                test_count, parse_errors, results.unexpected_behaviors
            );
            results.failure(&error_msg)
        }
    }

    /// Test HTTP status code error handling
    pub async fn test_http_status_errors(&self) -> NetworkErrorTestResults {
        let mut results = NetworkErrorTestResults::new("http_status_errors");
        let start_time = Instant::now();

        println!("🚨 Testing HTTP status code error handling...");

        let server = MockLlmServer::new().await;
        server.setup_error_scenarios().await;

        let client = Client::builder()
            .timeout(self.config.request_timeout)
            .build()
            .unwrap();

        let error_scenarios = vec![("server_error", 500, "Server Error")];

        let mut status_errors = 0;

        for (scenario, expected_status, description) in error_scenarios {
            println!("  🔴 Testing {} scenario", description);

            let result = client
                .post(format!(
                    "{}/v1/chat/completions?trigger_error={}",
                    server.base_url(),
                    scenario
                ))
                .header("authorization", "Bearer test-key")
                .json(&json!({
                    "model": "gpt-3.5-turbo",
                    "messages": [{"role": "user", "content": "test"}]
                }))
                .send()
                .await;

            results.requests_made += 1;

            match result {
                Ok(response) => {
                    let status = response.status().as_u16();
                    if status == expected_status {
                        status_errors += 1;
                        println!("    ✅ Got expected status code: {}", status);
                    } else if status >= 400 {
                        status_errors += 1;
                        println!(
                            "    ✅ Got error status code: {} (expected {})",
                            status, expected_status
                        );
                    } else {
                        results.unexpected_behaviors.push(format!(
                            "Unexpected success status {} for scenario {}",
                            status, scenario
                        ));
                        println!("    ⚠️  Unexpected success status: {}", status);
                    }
                }
                Err(e) => {
                    results.unexpected_behaviors.push(format!(
                        "Unexpected request error for scenario {}: {}",
                        scenario, e
                    ));
                    println!("    ⚠️  Unexpected request error: {}", e);
                }
            }
        }

        results.expected_errors_caught = status_errors;
        results.duration = start_time.elapsed();

        if status_errors >= 1 && results.unexpected_behaviors.len() <= 1 {
            results.success()
        } else {
            let error_msg = format!(
                "Expected at least 1 status error, got {}. Unexpected behaviors: {:?}",
                status_errors, results.unexpected_behaviors
            );
            results.failure(&error_msg)
        }
    }

    /// Test network instability simulation
    pub async fn test_network_instability(&self) -> NetworkErrorTestResults {
        let mut results = NetworkErrorTestResults::new("network_instability");
        let start_time = Instant::now();

        println!("📡 Testing network instability scenarios...");

        let server = MockLlmServer::new().await;

        // Configure server with network failure simulation
        server.configure(MockTestUtils::network_failure_config());
        server.setup_openai_chat().await;

        let client = Client::builder()
            .timeout(self.config.request_timeout)
            .build()
            .unwrap();

        let mut network_errors = 0;
        let test_count = 3;

        for i in 0..test_count {
            println!("  📶 Testing network instability attempt {}", i + 1);

            let result = client
                .post(format!("{}/v1/chat/completions", server.base_url()))
                .header("authorization", "Bearer test-key")
                .json(&json!({
                    "model": "gpt-3.5-turbo",
                    "messages": [{"role": "user", "content": format!("instability test {}", i)}]
                }))
                .send()
                .await;

            results.requests_made += 1;

            match result {
                Ok(response) => {
                    let status = response.status().as_u16();
                    if status >= 500 {
                        network_errors += 1;
                        println!("    ✅ Got server error as expected: {}", status);
                    } else {
                        results
                            .unexpected_behaviors
                            .push(format!("Unexpected success status: {}", status));
                        println!("    ⚠️  Unexpected success status: {}", status);
                    }
                }
                Err(e) => {
                    network_errors += 1;
                    println!("    ✅ Network error as expected: {}", e);
                }
            }
        }

        results.expected_errors_caught = network_errors;
        results.duration = start_time.elapsed();

        if network_errors >= 2 && results.unexpected_behaviors.is_empty() {
            results.success()
        } else {
            let error_msg = format!(
                "Expected at least 2 network errors, got {}. Unexpected behaviors: {:?}",
                network_errors, results.unexpected_behaviors
            );
            results.failure(&error_msg)
        }
    }

    /// Run all network error tests
    pub async fn run_all_tests(&self) -> Vec<NetworkErrorTestResults> {
        println!("🚀 Running comprehensive network error tests...");

        let mut all_results = Vec::new();

        // Run individual tests
        all_results.push(self.test_connection_timeout().await);
        all_results.push(self.test_dns_resolution_failure().await);
        all_results.push(self.test_malformed_response_handling().await);
        all_results.push(self.test_http_status_errors().await);
        all_results.push(self.test_network_instability().await);

        // Print summary
        let passed = all_results.iter().filter(|r| r.passed).count();
        let total = all_results.len();

        println!("\n📊 Network Error Tests Summary:");
        println!("  ✅ Passed: {}/{}", passed, total);
        println!("  ❌ Failed: {}/{}", total - passed, total);

        for result in &all_results {
            let status = if result.passed { "✅" } else { "❌" };
            println!("  {} {}: {:?}", status, result.test_name, result.duration);
            if let Some(error) = &result.error_message {
                println!("    Error: {}", error);
            }
        }

        all_results
    }
}

// ============================================================================
// Actual Tests
// ============================================================================

#[tokio::test]
async fn test_connection_timeout() {
    let config = NetworkErrorTestConfig {
        request_timeout: Duration::from_secs(2),
        ..Default::default()
    };

    let tester = NetworkErrorTester::new(config);
    let result = tester.test_connection_timeout().await;

    assert!(
        result.passed,
        "Connection timeout test failed: {:?}",
        result.error_message
    );
    assert!(result.expected_errors_caught >= 2);
    assert!(result.requests_made >= 3);
}

#[tokio::test]
async fn test_dns_resolution_failure() {
    let config = NetworkErrorTestConfig {
        request_timeout: Duration::from_secs(3),
        ..Default::default()
    };

    let tester = NetworkErrorTester::new(config);
    let result = tester.test_dns_resolution_failure().await;

    assert!(
        result.passed,
        "DNS resolution failure test failed: {:?}",
        result.error_message
    );
    assert!(result.expected_errors_caught >= 2);
    assert!(result.requests_made >= 3);
}

#[tokio::test]
async fn test_malformed_response_handling() {
    let config = NetworkErrorTestConfig::default();

    let tester = NetworkErrorTester::new(config);
    let result = tester.test_malformed_response_handling().await;

    assert!(
        result.passed,
        "Malformed response handling test failed: {:?}",
        result.error_message
    );
    assert!(
        result.expected_errors_caught >= 2,
        "Should catch at least 2 malformed response errors"
    );
    assert!(result.requests_made >= 2, "Should make at least 2 requests");
}

#[tokio::test]
async fn test_http_status_errors() {
    let config = NetworkErrorTestConfig::default();

    let tester = NetworkErrorTester::new(config);
    let result = tester.test_http_status_errors().await;

    assert!(
        result.passed,
        "HTTP status errors test failed: {:?}",
        result.error_message
    );
    assert!(result.expected_errors_caught >= 1);
    assert!(result.requests_made >= 1);
}

#[tokio::test]
async fn test_network_instability() {
    let config = NetworkErrorTestConfig::default();

    let tester = NetworkErrorTester::new(config);
    let result = tester.test_network_instability().await;

    assert!(
        result.passed,
        "Network instability test failed: {:?}",
        result.error_message
    );
    assert!(
        result.expected_errors_caught >= 1,
        "Should catch at least 1 network error"
    );
    assert!(result.requests_made >= 2, "Should make at least 2 requests");
}

#[tokio::test]
async fn test_comprehensive_network_errors() {
    let config = NetworkErrorTestConfig {
        request_timeout: Duration::from_secs(3),
        retry_attempts: 2,
        retry_delay: Duration::from_millis(50),
        test_concurrency: false, // Disable concurrency for this test
        concurrent_requests: 5,
    };

    let tester = NetworkErrorTester::new(config);
    let results = tester.run_all_tests().await;

    let passed_count = results.iter().filter(|r| r.passed).count();
    let total_count = results.len();

    // At least 80% of tests should pass
    let min_passed = (total_count * 4) / 5;
    assert!(
        passed_count >= min_passed,
        "Too many network error tests failed: {}/{} passed",
        passed_count,
        total_count
    );

    // Verify that we tested various error scenarios
    assert!(
        total_count >= 5,
        "Should have run at least 5 different error tests"
    );

    // Check that we made a reasonable number of requests
    let total_requests: usize = results.iter().map(|r| r.requests_made).sum();
    assert!(
        total_requests >= 10,
        "Should have made at least 10 test requests"
    );

    println!(
        "🎉 Comprehensive network error tests completed: {}/{} passed",
        passed_count, total_count
    );
}
