//! NightLight (Nightlight) integration for usage metrics
//!
//! This module provides a client for querying usage metrics from NightLight,
//! enabling the billing batch process to calculate charges based on actual
//! resource consumption.

use crate::billing::{ResourceUsage, UsageMetrics, UsageMetricsProvider};
use async_trait::async_trait;
use chrono::{DateTime, Utc};
use creditservice_types::{Error, ResourceType, Result};
use reqwest::Client;
use serde::Deserialize;
use std::collections::HashMap;
use std::sync::Arc;
use tracing::{debug, info, warn};

/// NightLight (Nightlight) client for usage metrics queries
#[derive(Clone)]
pub struct NightLightClient {
    client: Client,
    base_url: String,
}

/// Prometheus API response format
#[derive(Debug, Deserialize)]
struct PrometheusResponse {
    status: String,
    data: Option<PrometheusData>,
    error: Option<String>,
}

#[derive(Debug, Deserialize)]
struct PrometheusData {
    #[serde(rename = "resultType")]
    result_type: String,
    result: Vec<PrometheusResult>,
}

#[derive(Debug, Clone, Deserialize)]
struct PrometheusResult {
    metric: HashMap<String, String>,
    value: Option<(f64, String)>,       // For instant queries
    values: Option<Vec<(f64, String)>>, // For range queries
}

impl NightLightClient {
    /// Create a new NightLight client
    pub fn new(endpoint: &str) -> Self {
        Self {
            client: Client::new(),
            base_url: endpoint.trim_end_matches('/').to_string(),
        }
    }

    /// Create a NightLight client wrapped in Arc for sharing
    pub fn new_shared(endpoint: &str) -> Arc<Self> {
        Arc::new(Self::new(endpoint))
    }

    /// Query usage for a specific resource type
    async fn query_resource_usage(
        &self,
        project_id: &str,
        resource_type: ResourceType,
        period_start: DateTime<Utc>,
        period_end: DateTime<Utc>,
    ) -> Result<Option<ResourceUsage>> {
        let (query, unit) = Self::build_promql(project_id, resource_type, period_start, period_end);

        debug!(
            project_id = %project_id,
            resource_type = ?resource_type,
            query = %query,
            "Executing PromQL query"
        );

        let response = self
            .client
            .get(format!("{}/api/v1/query", self.base_url))
            .query(&[
                ("query", query.as_str()),
                ("time", &period_end.timestamp_millis().to_string()),
            ])
            .send()
            .await
            .map_err(|e| Error::Internal(format!("NightLight request failed: {}", e)))?;

        if !response.status().is_success() {
            return Err(Error::Internal(format!(
                "NightLight returned error status: {}",
                response.status()
            )));
        }

        let prom_response: PrometheusResponse = response
            .json()
            .await
            .map_err(|e| Error::Internal(format!("Failed to parse NightLight response: {}", e)))?;

        if prom_response.status != "success" {
            return Err(Error::Internal(format!(
                "NightLight query failed: {}",
                prom_response.error.unwrap_or_default()
            )));
        }

        // Extract the value from the response
        let quantity = prom_response
            .data
            .and_then(|d| d.result.first().cloned())
            .and_then(|r| r.value)
            .map(|(_, v)| v.parse::<f64>().unwrap_or(0.0))
            .unwrap_or(0.0);

        if quantity > 0.0 {
            Ok(Some(ResourceUsage {
                resource_type,
                quantity,
                unit,
            }))
        } else {
            Ok(None)
        }
    }

    /// Build PromQL query for a resource type
    fn build_promql(
        project_id: &str,
        resource_type: ResourceType,
        period_start: DateTime<Utc>,
        period_end: DateTime<Utc>,
    ) -> (String, String) {
        let duration_hours = (period_end - period_start).num_hours().max(1);
        let duration_str = format!("{}h", duration_hours);

        match resource_type {
            ResourceType::VmCpu => {
                // CPU hours: sum of CPU seconds converted to hours
                let query = format!(
                    r#"sum by (project_id) (increase(vm_cpu_seconds_total{{project_id="{}"}}[{}])) / 3600"#,
                    project_id, duration_str
                );
                (query, "cpu-hours".to_string())
            }
            ResourceType::VmMemoryGb => {
                // Memory GB-hours: average memory over time
                let query = format!(
                    r#"sum by (project_id) (avg_over_time(vm_memory_bytes{{project_id="{}"}}[{}])) / (1024*1024*1024)"#,
                    project_id, duration_str
                );
                (query, "gb-hours".to_string())
            }
            ResourceType::StorageGb => {
                // Storage GB-hours: average storage over time
                let query = format!(
                    r#"sum by (project_id) (avg_over_time(storage_bytes_total{{project_id="{}"}}[{}])) / (1024*1024*1024)"#,
                    project_id, duration_str
                );
                (query, "gb-hours".to_string())
            }
            ResourceType::VmInstance => {
                // Instance hours: count of running instances over time
                let query = format!(
                    r#"sum by (project_id) (count_over_time(vm_instance_running{{project_id="{}"}}[{}])) / (60 * {})"#,
                    project_id, duration_str, duration_hours
                );
                (query, "instance-hours".to_string())
            }
            ResourceType::NetworkPort => {
                let query = format!(
                    r#"sum by (project_id) (count_over_time(network_port_active{{project_id="{}"}}[{}])) / (60 * {})"#,
                    project_id, duration_str, duration_hours
                );
                (query, "port-hours".to_string())
            }
            ResourceType::LoadBalancer => {
                let query = format!(
                    r#"sum by (project_id) (count_over_time(lb_instance_active{{project_id="{}"}}[{}])) / (60 * {})"#,
                    project_id, duration_str, duration_hours
                );
                (query, "lb-hours".to_string())
            }
            ResourceType::DnsZone => {
                let query = format!(
                    r#"count(dns_zone_active{{project_id="{}"}})"#,
                    project_id
                );
                (query, "zones".to_string())
            }
            ResourceType::DnsRecord => {
                let query = format!(
                    r#"count(dns_record_active{{project_id="{}"}})"#,
                    project_id
                );
                (query, "records".to_string())
            }
            ResourceType::K8sCluster => {
                let query = format!(
                    r#"sum by (project_id) (count_over_time(k8s_cluster_running{{project_id="{}"}}[{}])) / (60 * {})"#,
                    project_id, duration_str, duration_hours
                );
                (query, "cluster-hours".to_string())
            }
            ResourceType::K8sNode => {
                let query = format!(
                    r#"sum by (project_id) (count_over_time(k8s_node_running{{project_id="{}"}}[{}])) / (60 * {})"#,
                    project_id, duration_str, duration_hours
                );
                (query, "node-hours".to_string())
            }
        }
    }

    /// Health check - verify NightLight connectivity
    pub async fn health_check(&self) -> Result<()> {
        let response = self
            .client
            .get(format!("{}/api/v1/query", self.base_url))
            .query(&[("query", "up")])
            .send()
            .await
            .map_err(|e| Error::Internal(format!("NightLight health check failed: {}", e)))?;

        if response.status().is_success() {
            Ok(())
        } else {
            Err(Error::Internal(format!(
                "NightLight health check returned: {}",
                response.status()
            )))
        }
    }
}

#[async_trait]
impl UsageMetricsProvider for NightLightClient {
    async fn get_usage_metrics(
        &self,
        project_id: &str,
        period_start: DateTime<Utc>,
        period_end: DateTime<Utc>,
    ) -> Result<UsageMetrics> {
        info!(
            project_id = %project_id,
            period_start = %period_start,
            period_end = %period_end,
            "Querying NightLight for usage metrics"
        );

        let mut resource_usage = HashMap::new();

        // Query each resource type
        for resource_type in [
            ResourceType::VmInstance,
            ResourceType::VmCpu,
            ResourceType::VmMemoryGb,
            ResourceType::StorageGb,
            ResourceType::NetworkPort,
            ResourceType::LoadBalancer,
            ResourceType::DnsZone,
            ResourceType::DnsRecord,
            ResourceType::K8sCluster,
            ResourceType::K8sNode,
        ] {
            match self
                .query_resource_usage(project_id, resource_type, period_start, period_end)
                .await
            {
                Ok(Some(usage)) => {
                    resource_usage.insert(resource_type, usage);
                }
                Ok(None) => {
                    // No usage for this resource type
                }
                Err(e) => {
                    warn!(
                        project_id = %project_id,
                        resource_type = ?resource_type,
                        error = %e,
                        "Failed to query resource usage, skipping"
                    );
                }
            }
        }

        Ok(UsageMetrics {
            project_id: project_id.to_string(),
            resource_usage,
            period_start,
            period_end,
        })
    }

    async fn list_projects_with_usage(
        &self,
        period_start: DateTime<Utc>,
        period_end: DateTime<Utc>,
    ) -> Result<Vec<String>> {
        let duration_hours = (period_end - period_start).num_hours().max(1);
        let duration_str = format!("{}h", duration_hours);

        // Query for all project_ids with any metric in the period
        let query = format!(
            r#"group by (project_id) ({{project_id=~".+"}}[{}])"#,
            duration_str
        );

        debug!(query = %query, "Listing projects with usage");

        let response = self
            .client
            .get(format!("{}/api/v1/query", self.base_url))
            .query(&[
                ("query", query.as_str()),
                ("time", &period_end.timestamp_millis().to_string()),
            ])
            .send()
            .await
            .map_err(|e| Error::Internal(format!("NightLight request failed: {}", e)))?;

        if !response.status().is_success() {
            return Err(Error::Internal(format!(
                "NightLight returned error status: {}",
                response.status()
            )));
        }

        let prom_response: PrometheusResponse = response
            .json()
            .await
            .map_err(|e| Error::Internal(format!("Failed to parse NightLight response: {}", e)))?;

        if prom_response.status != "success" {
            return Err(Error::Internal(format!(
                "NightLight query failed: {}",
                prom_response.error.unwrap_or_default()
            )));
        }

        // Extract project_ids from results
        let project_ids: Vec<String> = prom_response
            .data
            .map(|d| {
                d.result
                    .into_iter()
                    .filter_map(|r| r.metric.get("project_id").cloned())
                    .collect()
            })
            .unwrap_or_default();

        Ok(project_ids)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_build_promql_cpu() {
        let start = DateTime::parse_from_rfc3339("2025-12-11T00:00:00Z")
            .unwrap()
            .with_timezone(&Utc);
        let end = DateTime::parse_from_rfc3339("2025-12-11T01:00:00Z")
            .unwrap()
            .with_timezone(&Utc);

        let (query, unit) =
            NightLightClient::build_promql("proj-1", ResourceType::VmCpu, start, end);

        assert!(query.contains("vm_cpu_seconds_total"));
        assert!(query.contains("project_id=\"proj-1\""));
        assert!(query.contains("[1h]"));
        assert_eq!(unit, "cpu-hours");
    }

    #[test]
    fn test_build_promql_storage() {
        let start = DateTime::parse_from_rfc3339("2025-12-11T00:00:00Z")
            .unwrap()
            .with_timezone(&Utc);
        let end = DateTime::parse_from_rfc3339("2025-12-11T12:00:00Z")
            .unwrap()
            .with_timezone(&Utc);

        let (query, unit) =
            NightLightClient::build_promql("proj-2", ResourceType::StorageGb, start, end);

        assert!(query.contains("storage_bytes_total"));
        assert!(query.contains("project_id=\"proj-2\""));
        assert!(query.contains("[12h]"));
        assert_eq!(unit, "gb-hours");
    }

    #[test]
    fn test_build_promql_vm_instance() {
        let start = DateTime::parse_from_rfc3339("2025-12-11T00:00:00Z")
            .unwrap()
            .with_timezone(&Utc);
        let end = DateTime::parse_from_rfc3339("2025-12-11T06:00:00Z")
            .unwrap()
            .with_timezone(&Utc);

        let (query, unit) =
            NightLightClient::build_promql("proj-3", ResourceType::VmInstance, start, end);

        assert!(query.contains("vm_instance_running"));
        assert!(query.contains("project_id=\"proj-3\""));
        assert!(query.contains("[6h]"));
        assert_eq!(unit, "instance-hours");
    }

    #[test]
    fn test_client_creation() {
        let client = NightLightClient::new("http://nightlight:8080");
        assert_eq!(client.base_url, "http://nightlight:8080");

        let client2 = NightLightClient::new("http://nightlight:8080/");
        assert_eq!(client2.base_url, "http://nightlight:8080");
    }
}