//! STRICT TDD - Billing Manager Tests
//! These tests define the complete billing system behavior before implementation

use chrono::{DateTime, Utc};
use std::collections::HashMap;
use std::time::{Duration, SystemTime, UNIX_EPOCH};
use tokio::time;
use uuid::Uuid;

use rtx_platform::billing::{
    AggregationPeriod, AlertThreshold, BillingAlert, BillingConfig, BillingManager, CostCalculator,
    Invoice, InvoiceGenerator, PricingTier, ResourceType, UsageMeter, UsageRecord,
};
use rtx_platform::{PlatformConfig, PlatformResult};

fn create_test_billing_config() -> BillingConfig {
    BillingConfig {
        pricing_tiers: vec![
            PricingTier {
                resource_type: ResourceType::Compute,
                tiers: vec![
                    (0.0, 1000.0, 0.10),           // $0.10/hour for first 1000 hours
                    (1000.0, 5000.0, 0.08),        // $0.08/hour for next 4000 hours
                    (5000.0, f64::INFINITY, 0.06), // $0.06/hour for 5000+ hours
                ],
            },
            PricingTier {
                resource_type: ResourceType::Storage,
                tiers: vec![
                    (0.0, 1024.0, 0.023),           // $0.023/GB-month for first TB
                    (1024.0, f64::INFINITY, 0.021), // $0.021/GB-month for 1TB+
                ],
            },
            PricingTier {
                resource_type: ResourceType::NetworkEgress,
                tiers: vec![
                    (0.0, 100.0, 0.0),              // First 100GB free
                    (100.0, 1024.0, 0.09),          // $0.09/GB for next 924GB
                    (1024.0, f64::INFINITY, 0.085), // $0.085/GB for 1TB+
                ],
            },
        ],
        aggregation_period: AggregationPeriod::Hourly,
        alert_thresholds: vec![AlertThreshold {
            tenant_id: "default".to_string(),
            monthly_limit: 1000.0,
            warning_threshold: 0.8,
            critical_threshold: 0.95,
        }],
        invoice_generation_day: 1,
        late_fee_rate: 0.015, // 1.5% monthly late fee
    }
}

fn create_test_platform_config() -> PlatformConfig {
    PlatformConfig {
        database_url: "postgresql://test:test@localhost/billing_test".to_string(),
        redis_urls: vec!["redis://localhost:6379".to_string()],
        kafka_brokers: vec!["localhost:9092".to_string()],
        metrics_endpoint: "localhost:9090".to_string(),
        regions: HashMap::new(),
        sla_targets: rtx_platform::slo::SlaTargets::default(),
    }
}

#[tokio::test]
async fn test_billing_manager_creation() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let billing_config = create_test_billing_config();

    let billing_manager = BillingManager::new(&config, billing_config).await?;

    assert!(billing_manager.is_healthy().await?);
    Ok(())
}

#[tokio::test]
async fn test_usage_meter_records_compute_usage() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let billing_config = create_test_billing_config();

    let mut billing_manager = BillingManager::new(&config, billing_config).await?;
    billing_manager.start().await?;

    let tenant_id = Uuid::new_v4();
    let region = "us-west-2".to_string();

    // Record compute usage
    let usage_record = UsageRecord {
        id: Uuid::new_v4(),
        tenant_id,
        region: region.clone(),
        resource_type: ResourceType::Compute,
        quantity: 2.5, // 2.5 GPU hours
        timestamp: Utc::now(),
        metadata: HashMap::from([
            ("instance_type".to_string(), "h100-8x".to_string()),
            ("region".to_string(), region),
        ]),
    };

    billing_manager.record_usage(usage_record.clone()).await?;

    // Verify usage was recorded
    let recorded_usage = billing_manager
        .get_usage_for_tenant(tenant_id, Utc::now().date_naive())
        .await?;

    assert_eq!(recorded_usage.len(), 1);
    assert_eq!(recorded_usage[0].resource_type, ResourceType::Compute);
    assert_eq!(recorded_usage[0].quantity, 2.5);

    billing_manager.shutdown().await?;
    Ok(())
}

#[tokio::test]
async fn test_cost_calculation_tiered_pricing() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let billing_config = create_test_billing_config();

    let billing_manager = BillingManager::new(&config, billing_config).await?;
    let cost_calculator = billing_manager.cost_calculator();

    // Test tiered compute pricing
    let usage_records = vec![
        UsageRecord {
            id: Uuid::new_v4(),
            tenant_id: Uuid::new_v4(),
            region: "us-west-2".to_string(),
            resource_type: ResourceType::Compute,
            quantity: 500.0, // First tier: 500 * $0.10 = $50.00
            timestamp: Utc::now(),
            metadata: HashMap::new(),
        },
        UsageRecord {
            id: Uuid::new_v4(),
            tenant_id: Uuid::new_v4(),
            region: "us-west-2".to_string(),
            resource_type: ResourceType::Compute,
            quantity: 1500.0, // Tiered: 1000 * $0.10 + 500 * $0.08 = $140.00
            timestamp: Utc::now(),
            metadata: HashMap::new(),
        },
    ];

    let total_cost = cost_calculator.calculate_cost(&usage_records).await?;

    // Expected: $50.00 (500 * $0.10) + $140.00 (1000 * $0.10 + 500 * $0.08) = $190.00
    assert_eq!((total_cost * 100.0).round() / 100.0, 190.0);

    Ok(())
}

#[tokio::test]
async fn test_cost_calculation_free_tier() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let billing_config = create_test_billing_config();

    let billing_manager = BillingManager::new(&config, billing_config).await?;
    let cost_calculator = billing_manager.cost_calculator();

    // Test free network egress tier
    let usage_records = vec![UsageRecord {
        id: Uuid::new_v4(),
        tenant_id: Uuid::new_v4(),
        region: "us-west-2".to_string(),
        resource_type: ResourceType::NetworkEgress,
        quantity: 50.0, // First 100GB free
        timestamp: Utc::now(),
        metadata: HashMap::new(),
    }];

    let total_cost = cost_calculator.calculate_cost(&usage_records).await?;

    // Should be $0.00 for free tier
    assert_eq!(total_cost, 0.0);

    Ok(())
}

#[tokio::test]
async fn test_real_time_billing_alerts() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let mut billing_config = create_test_billing_config();

    let tenant_id = Uuid::new_v4();
    billing_config.alert_thresholds[0].tenant_id = tenant_id.to_string();
    billing_config.alert_thresholds[0].monthly_limit = 100.0; // Low limit for testing

    let mut billing_manager = BillingManager::new(&config, billing_config).await?;
    billing_manager.start().await?;

    // Record usage that exceeds warning threshold (80% of $100 = $80)
    let high_usage = UsageRecord {
        id: Uuid::new_v4(),
        tenant_id,
        region: "us-west-2".to_string(),
        resource_type: ResourceType::Compute,
        quantity: 850.0, // 850 * $0.10 = $85.00 (exceeds warning)
        timestamp: Utc::now(),
        metadata: HashMap::new(),
    };

    billing_manager.record_usage(high_usage).await?;

    // Wait for alert processing
    time::sleep(Duration::from_millis(100)).await;

    let alerts = billing_manager.get_active_alerts(tenant_id).await?;

    assert!(!alerts.is_empty());
    assert_eq!(alerts[0].alert_type, BillingAlert::Warning);
    assert_eq!(alerts[0].tenant_id, tenant_id);

    billing_manager.shutdown().await?;
    Ok(())
}

#[tokio::test]
async fn test_usage_aggregation_across_regions() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let billing_config = create_test_billing_config();

    let mut billing_manager = BillingManager::new(&config, billing_config).await?;
    billing_manager.start().await?;

    let tenant_id = Uuid::new_v4();

    // Record usage across multiple regions
    let usage_records = vec![
        UsageRecord {
            id: Uuid::new_v4(),
            tenant_id,
            region: "us-west-2".to_string(),
            resource_type: ResourceType::Compute,
            quantity: 100.0,
            timestamp: Utc::now(),
            metadata: HashMap::new(),
        },
        UsageRecord {
            id: Uuid::new_v4(),
            tenant_id,
            region: "us-east-1".to_string(),
            resource_type: ResourceType::Compute,
            quantity: 150.0,
            timestamp: Utc::now(),
            metadata: HashMap::new(),
        },
        UsageRecord {
            id: Uuid::new_v4(),
            tenant_id,
            region: "eu-west-1".to_string(),
            resource_type: ResourceType::Compute,
            quantity: 200.0,
            timestamp: Utc::now(),
            metadata: HashMap::new(),
        },
    ];

    for record in usage_records {
        billing_manager.record_usage(record).await?;
    }

    let aggregated_usage = billing_manager
        .get_aggregated_usage(tenant_id, AggregationPeriod::Daily)
        .await?;

    // Should aggregate to 450.0 total across all regions
    let total_compute = aggregated_usage
        .get(&ResourceType::Compute)
        .expect("Compute usage should be present");

    assert_eq!(*total_compute, 450.0);

    billing_manager.shutdown().await?;
    Ok(())
}

#[tokio::test]
async fn test_invoice_generation_monthly() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let billing_config = create_test_billing_config();

    let mut billing_manager = BillingManager::new(&config, billing_config).await?;
    billing_manager.start().await?;

    let tenant_id = Uuid::new_v4();

    // Record usage for the month
    let usage_record = UsageRecord {
        id: Uuid::new_v4(),
        tenant_id,
        region: "us-west-2".to_string(),
        resource_type: ResourceType::Compute,
        quantity: 1000.0, // $100.00
        timestamp: Utc::now(),
        metadata: HashMap::new(),
    };

    billing_manager.record_usage(usage_record).await?;

    // Generate invoice
    let invoice = billing_manager
        .generate_invoice(tenant_id, Utc::now().date_naive())
        .await?;

    assert_eq!(invoice.tenant_id, tenant_id);
    assert_eq!((invoice.total_amount * 100.0).round() / 100.0, 100.0);
    assert_eq!(invoice.line_items.len(), 1);
    assert_eq!(invoice.line_items[0].resource_type, ResourceType::Compute);

    billing_manager.shutdown().await?;
    Ok(())
}

#[tokio::test]
async fn test_invoice_late_fees() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let billing_config = create_test_billing_config();

    let mut billing_manager = BillingManager::new(&config, billing_config).await?;
    billing_manager.start().await?;

    let tenant_id = Uuid::new_v4();

    // Create overdue invoice (30+ days old)
    let old_date = Utc::now().date_naive() - chrono::Duration::days(35);
    let mut invoice = Invoice {
        id: Uuid::new_v4(),
        tenant_id,
        billing_period_start: old_date,
        billing_period_end: old_date + chrono::Duration::days(30),
        generated_at: DateTime::from_naive_utc_and_offset(
            old_date.and_hms_opt(0, 0, 0).unwrap(),
            Utc,
        ),
        due_date: old_date + chrono::Duration::days(30),
        total_amount: 100.0,
        line_items: vec![],
        status: rtx_platform::billing::InvoiceStatus::Outstanding,
        late_fees: 0.0,
    };

    billing_manager.store_invoice(&invoice).await?;

    // Process late fees
    billing_manager.process_late_fees().await?;

    // Retrieve updated invoice
    let updated_invoice = billing_manager.get_invoice(invoice.id).await?;

    // Should have 1.5% late fee
    let expected_late_fee = 100.0 * 0.015;
    assert_eq!(
        (updated_invoice.late_fees * 1000.0).round() / 1000.0,
        expected_late_fee
    );

    billing_manager.shutdown().await?;
    Ok(())
}

#[tokio::test]
async fn test_billing_precision_tracking() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let billing_config = create_test_billing_config();

    let mut billing_manager = BillingManager::new(&config, billing_config).await?;
    billing_manager.start().await?;

    let tenant_id = Uuid::new_v4();

    // Record precise usage with fractional values
    let precision_usage = UsageRecord {
        id: Uuid::new_v4(),
        tenant_id,
        region: "us-west-2".to_string(),
        resource_type: ResourceType::Storage,
        quantity: 1536.7832, // Precise GB-months
        timestamp: Utc::now(),
        metadata: HashMap::new(),
    };

    billing_manager.record_usage(precision_usage).await?;

    let cost_calculator = billing_manager.cost_calculator();
    let usage_records = billing_manager
        .get_usage_for_tenant(tenant_id, Utc::now().date_naive())
        .await?;

    let total_cost = cost_calculator.calculate_cost(&usage_records).await?;

    // Verify precision is maintained in calculations
    // First 1024GB at $0.023 + 512.7832GB at $0.021
    let expected_cost = (1024.0 * 0.023) + (512.7832 * 0.021);
    let cost_diff = (total_cost - expected_cost).abs();

    assert!(
        cost_diff < 0.0001,
        "Cost calculation should be precise to 4 decimal places"
    );

    billing_manager.shutdown().await?;
    Ok(())
}

#[tokio::test]
async fn test_concurrent_usage_recording() -> PlatformResult<()> {
    let config = create_test_platform_config();
    let billing_config = create_test_billing_config();

    let mut billing_manager = BillingManager::new(&config, billing_config).await?;
    billing_manager.start().await?;

    let tenant_id = Uuid::new_v4();

    // Spawn multiple concurrent usage recording tasks
    let mut handles = vec![];

    for i in 0..100 {
        let billing_manager_clone = billing_manager.clone();
        let handle = tokio::spawn(async move {
            let usage_record = UsageRecord {
                id: Uuid::new_v4(),
                tenant_id,
                region: "us-west-2".to_string(),
                resource_type: ResourceType::Compute,
                quantity: i as f64 * 0.1,
                timestamp: Utc::now(),
                metadata: HashMap::new(),
            };

            billing_manager_clone.record_usage(usage_record).await
        });

        handles.push(handle);
    }

    // Wait for all tasks to complete
    for handle in handles {
        handle.await.unwrap()?;
    }

    let usage_records = billing_manager
        .get_usage_for_tenant(tenant_id, Utc::now().date_naive())
        .await?;

    // All 100 records should be stored
    assert_eq!(usage_records.len(), 100);

    billing_manager.shutdown().await?;
    Ok(())
}