use futures_util::StreamExt;
use reqwest::Client;
use std::env;
use std::time::Duration;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    tracing_subscriber::fmt::init();

    let target = env::var("MCP_TARGET").unwrap_or_else(|_| "http://127.0.0.1:3000".to_string());
    let token = env::var("MCP_AUTH_TOKEN")
        .unwrap_or_else(|_| "jP76lUJ5DtFRZmcvXH8LKdCTIkp29eAf".to_string());

    tracing::info!("Starting skeletal client to {}", target);

    let client = Client::new();

    let sse_url = format!("{target}/sse");

    tracing::info!("Connecting to SSE: {}", sse_url);

    let res = client.get(&sse_url).bearer_auth(&token).send().await?;

    if !res.status().is_success() {
        tracing::error!("Failed to connect to SSE: {}", res.status());
        return Err("SSE connection failed".into());
    }

    tracing::info!("SSE Connected. Reading stream...");

    let mut stream = res.bytes_stream();
    let mut buffer = Vec::new();
    let mut post_endpoint = None;

    // Read the initial event containing the POST endpoint
    while let Some(chunk) = stream.next().await {
        let bytes = chunk?;
        buffer.extend_from_slice(&bytes);

        while let Some(pos) = buffer.windows(2).position(|w| w == b"\n\n" || w == b"\r\n") {
            let msg_bytes = buffer.drain(..pos).collect::<Vec<_>>();
            buffer.drain(..2);

            let text = String::from_utf8_lossy(&msg_bytes);
            let mut is_endpoint = false;
            let mut data_content = String::new();

            for line in text.lines() {
                if line.starts_with("event: endpoint") {
                    is_endpoint = true;
                } else if let Some(data) = line.strip_prefix("data: ") {
                    data_content.push_str(data);
                }
            }

            if is_endpoint && !data_content.is_empty() {
                tracing::info!("Received POST endpoint: {}", data_content);
                post_endpoint = Some(data_content);
                break;
            }
            tracing::info!("Received early SSE data: {}", text);
        }
        if post_endpoint.is_some() {
            break;
        }
    }

    let post_endpoint = post_endpoint.ok_or("Did not receive endpoint from SSE stream")?;
    let post_url = format!("{target}{post_endpoint}");

    let payload = r#"{"jsonrpc":"2.0","id":999,"method":"server/discover","params":{}}"#;

    tracing::info!("Sending test payload to {}", post_url);
    tracing::info!("Payload: {}", payload);

    let post_res = client
        .post(&post_url)
        .bearer_auth(&token)
        .header("Content-Type", "application/json")
        .body(payload.to_string())
        .send()
        .await?;

    tracing::info!("POST Response Status: {}", post_res.status());
    let post_body = post_res.text().await?;
    tracing::info!("POST Response Body: {}", post_body);

    // Wait for the SSE stream to deliver the response
    tracing::info!("Waiting 2 seconds for SSE response delivery...");

    let mut timeout = tokio::time::interval(Duration::from_secs(2));
    timeout.tick().await; // first tick is immediate

    tokio::select! {
        _ = timeout.tick() => {
            tracing::warn!("Timed out waiting for SSE response.");
        }
        () = async {
            while let Some(chunk) = stream.next().await {
                if let Ok(bytes) = chunk {
                    tracing::info!("Received SSE Chunk: {}", String::from_utf8_lossy(&bytes));
                    break;
                }
            }
        } => {
            tracing::info!("Successfully read SSE response from stream.");
        }
    }

    tracing::info!("Skeletal client test complete.");
    Ok(())
}