//! Example: Push metrics to Nightlight using Prometheus remote_write
//!
//! This example demonstrates how to send metrics to a Nightlight server
//! using the Prometheus remote_write protocol with snappy compression
//! and protobuf encoding.
//!
//! # Usage
//!
//! 1. Start the Nightlight server:
//!    ```bash
//!    cargo run --bin nightlight-server
//!    ```
//!
//! 2. In another terminal, run this example:
//!    ```bash
//!    cargo run --example push_metrics
//!    ```
//!
//! # Protocol
//!
//! The remote_write protocol involves:
//! 1. Create WriteRequest protobuf with time series data
//! 2. Encode to protobuf binary format
//! 3. Compress with Snappy compression
//! 4. POST to /api/v1/write endpoint
//!
//! # Expected Output
//!
//! ```text
//! Pushing metrics to http://127.0.0.1:9101/api/v1/write...
//! Response status: 204 No Content
//! Successfully pushed 3 samples across 2 time series
//! ```

use nightlight_api::prometheus::{Label, Sample, TimeSeries, WriteRequest};
use prost::Message;
use snap::raw::Encoder as SnappyEncoder;
use std::time::{SystemTime, UNIX_EPOCH};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create HTTP client
    let client = reqwest::Client::new();

    // Server URL (default Nightlight HTTP address)
    let url = "http://127.0.0.1:9101/api/v1/write";

    println!("Pushing metrics to {}...", url);

    // Get current timestamp in milliseconds
    let now = SystemTime::now()
        .duration_since(UNIX_EPOCH)?
        .as_millis() as i64;

    // Create WriteRequest with sample metrics
    let write_request = WriteRequest {
        timeseries: vec![
            // Example 1: HTTP request counter
            TimeSeries {
                labels: vec![
                    Label {
                        name: "__name__".to_string(),
                        value: "http_requests_total".to_string(),
                    },
                    Label {
                        name: "job".to_string(),
                        value: "example_app".to_string(),
                    },
                    Label {
                        name: "method".to_string(),
                        value: "GET".to_string(),
                    },
                    Label {
                        name: "status".to_string(),
                        value: "200".to_string(),
                    },
                ],
                samples: vec![
                    Sample {
                        value: 1234.0,
                        timestamp: now,
                    },
                ],
            },
            // Example 2: Request duration histogram
            TimeSeries {
                labels: vec![
                    Label {
                        name: "__name__".to_string(),
                        value: "http_request_duration_seconds".to_string(),
                    },
                    Label {
                        name: "job".to_string(),
                        value: "example_app".to_string(),
                    },
                    Label {
                        name: "method".to_string(),
                        value: "GET".to_string(),
                    },
                ],
                samples: vec![
                    Sample {
                        value: 0.042,
                        timestamp: now,
                    },
                    Sample {
                        value: 0.055,
                        timestamp: now + 1000, // 1 second later
                    },
                ],
            },
        ],
    };

    // Count total samples
    let total_samples: usize = write_request
        .timeseries
        .iter()
        .map(|ts| ts.samples.len())
        .sum();

    // Encode to protobuf
    let mut buf = Vec::new();
    write_request.encode(&mut buf)?;
    println!("Encoded {} bytes of protobuf data", buf.len());

    // Compress with snappy
    let mut encoder = SnappyEncoder::new();
    let compressed = encoder.compress_vec(&buf)?;
    println!("Compressed to {} bytes with Snappy", compressed.len());

    // Send to Nightlight
    let response = client
        .post(url)
        .header("Content-Type", "application/x-protobuf")
        .header("Content-Encoding", "snappy")
        .body(compressed)
        .send()
        .await?;

    println!("Response status: {}", response.status());

    if response.status().is_success() {
        println!(
            "Successfully pushed {} samples across {} time series",
            total_samples,
            write_request.timeseries.len()
        );
    } else {
        let error_text = response.text().await?;
        eprintln!("Error response: {}", error_text);
        std::process::exit(1);
    }

    Ok(())
}