// api/ — LLM API client (OpenAI-compatible)
//
// Works with any provider that implements the OpenAI chat completions
// API: OpenRouter, vLLM, llama.cpp, Fireworks, Together, etc.
//
// Diagnostics: anomalies always logged to debug panel.
// Set POC_DEBUG=1 for verbose per-turn logging.

pub mod http;

use std::time::{Duration, Instant};
use anyhow::Result;
use tokio::sync::mpsc;
use serde::Deserialize;

use http::{HttpClient, HttpResponse};

#[derive(Debug, Clone, Deserialize)]
pub struct Usage {
    pub prompt_tokens: u32,
    pub completion_tokens: u32,
    pub total_tokens: u32,
}

/// A JoinHandle that aborts its task when dropped.
pub(crate) struct AbortOnDrop(tokio::task::JoinHandle<()>);

impl Drop for AbortOnDrop {
    fn drop(&mut self) {
        self.0.abort();
    }
}

/// Sampling parameters for model generation.
#[derive(Clone, Copy)]
pub(crate) struct SamplingParams {
    pub temperature: f32,
    pub top_p: f32,
    pub top_k: u32,
}

// ─────────────────────────────────────────────────────────────
//  Stream events — yielded by backends, consumed by the runner
// ─────────────────────────────────────────────────────────────

/// One token from the streaming completions API.
pub(crate) enum StreamToken {
    Token { text: String, id: u32 },
    Done { usage: Option<Usage> },
    Error(String),
}

#[derive(Clone)]
pub struct ApiClient {
    client: HttpClient,
    api_key: String,
    pub model: String,
    base_url: String,
}

impl ApiClient {
    pub fn new(base_url: &str, api_key: &str, model: &str) -> Self {
        let client = HttpClient::builder()
            .connect_timeout(Duration::from_secs(30))
            .timeout(Duration::from_secs(600))
            .build();

        Self {
            client,
            api_key: api_key.to_string(),
            model: model.to_string(),
            base_url: base_url.trim_end_matches('/').to_string(),
        }
    }

    pub(crate) fn stream_completion(
        &self,
        prompt_tokens: &[u32],
        sampling: SamplingParams,
        priority: Option<i32>,
    ) -> (mpsc::UnboundedReceiver<StreamToken>, AbortOnDrop) {
        let (tx, rx) = mpsc::unbounded_channel();
        let client = self.client.clone();
        let api_key = self.api_key.clone();
        let model = self.model.clone();
        let prompt_tokens = prompt_tokens.to_vec();
        let base_url = self.base_url.clone();

        let handle = tokio::spawn(async move {
            let result = stream_completions(
                &client, &base_url, &api_key, &model,
                &prompt_tokens, &tx, sampling, priority,
            ).await;
            if let Err(e) = result {
                let _ = tx.send(StreamToken::Error(e.to_string()));
            }
        });

        (rx, AbortOnDrop(handle))
    }

    pub fn base_url(&self) -> &str { &self.base_url }
    pub fn api_key(&self) -> &str { &self.api_key }

}

async fn stream_completions(
    client: &HttpClient,
    base_url: &str,
    api_key: &str,
    model: &str,
    prompt_tokens: &[u32],
    tx: &mpsc::UnboundedSender<StreamToken>,
    sampling: SamplingParams,
    priority: Option<i32>,
) -> anyhow::Result<()> {
    let mut request = serde_json::json!({
        "model": model,
        "prompt": prompt_tokens,
        "max_tokens": 16384,
        "temperature": sampling.temperature,
        "top_p": sampling.top_p,
        "top_k": sampling.top_k,
        "stream": true,
        "return_token_ids": true,
        "skip_special_tokens": false,
        "stop_token_ids": [super::tokenizer::IM_END],
    });
    if let Some(p) = priority {
        request["priority"] = serde_json::json!(p);
    }

    let url = format!("{}/completions", base_url);
    let debug_label = format!("{} prompt tokens, model={}", prompt_tokens.len(), model);

    let mut response = send_and_check(
        client, &url, &request,
        ("Authorization", &format!("Bearer {}", api_key)),
        &[], &debug_label, None,
    ).await?;

    let mut reader = SseReader::new();
    let mut usage = None;

    while let Some(event) = reader.next_event(&mut response).await? {
        if let Some(err_msg) = event["error"]["message"].as_str() {
            anyhow::bail!("API error in stream: {}", err_msg);
        }

        if let Some(u) = event["usage"].as_object() {
            if let Ok(u) = serde_json::from_value::<Usage>(serde_json::Value::Object(u.clone())) {
                usage = Some(u);
            }
        }

        let choices = match event["choices"].as_array() {
            Some(c) => c,
            None => continue,
        };

        for choice in choices {
            let text = choice["text"].as_str().unwrap_or("");
            let token_ids = choice["token_ids"].as_array();

            if let Some(ids) = token_ids {
                for (i, id_val) in ids.iter().enumerate() {
                    if let Some(id) = id_val.as_u64() {
                        let _ = tx.send(StreamToken::Token {
                            text: if i == 0 { text.to_string() } else { String::new() },
                            id: id as u32,
                        });
                    }
                }
            } else if !text.is_empty() {
                let _ = tx.send(StreamToken::Token { text: text.to_string(), id: 0 });
            }
        }
    }

    let _ = tx.send(StreamToken::Done { usage });
    Ok(())
}

/// Send an HTTP request and check for errors.
pub(crate) async fn send_and_check(
    client: &HttpClient,
    url: &str,
    body: &impl serde::Serialize,
    auth_header: (&str, &str),
    extra_headers: &[(&str, &str)],
    debug_label: &str,
    request_json: Option<&str>,
) -> Result<HttpResponse> {
    let debug = std::env::var("POC_DEBUG").is_ok();
    let start = Instant::now();

    if debug {
        let payload_size = serde_json::to_string(body)
            .map(|s| s.len())
            .unwrap_or(0);
        dbglog!(
            "request: {}K payload, {}",
            payload_size / 1024, debug_label,
        );
    }

    let mut headers: Vec<(&str, &str)> = Vec::with_capacity(extra_headers.len() + 1);
    headers.push(auth_header);
    headers.extend_from_slice(extra_headers);

    let response = client
        .send_json("POST", url, &headers, body)
        .await
        .map_err(|e| {
            let msg = e.to_string();
            let cause = if msg.contains("connect timeout") || msg.contains("TCP connect") {
                "connection refused"
            } else if msg.contains("request timeout") {
                "request timed out"
            } else {
                "request error"
            };
            anyhow::anyhow!("{} ({}): {}", cause, url, msg)
        })?;

    let status = response.status();
    let elapsed = start.elapsed();

    if debug {
        for name in [
            "x-ratelimit-remaining",
            "x-ratelimit-limit",
            "x-request-id",
        ] {
            if let Some(val) = response.header(name) {
                dbglog!("header {}: {}", name, val);
            }
        }
    }

    if !status.is_success() {
        let body = response.text().await.unwrap_or_default();
        dbglog!(
            "HTTP {} after {:.1}s ({}): {}",
            status,
            elapsed.as_secs_f64(),
            url,
            &body[..body.len().min(500)]
        );
        if let Some(json) = request_json {
            let log_dir = dirs::home_dir()
                .unwrap_or_default()
                .join(".consciousness/logs/failed-requests");
            let _ = std::fs::create_dir_all(&log_dir);
            let ts = chrono::Local::now().format("%Y%m%dT%H%M%S");
            let path = log_dir.join(format!("{}.json", ts));
            if std::fs::write(&path, json).is_ok() {
                dbglog!(
                    "saved failed request to {} (HTTP {})", path.display(), status
                );
            }
        }
        anyhow::bail!("HTTP {} ({}): {}", status, url, &body[..body.len().min(1000)]);
    }

    if debug {
        dbglog!(
            "connected in {:.1}s (HTTP {})",
            elapsed.as_secs_f64(),
            status.as_u16()
        );
    }

    Ok(response)
}

/// SSE stream reader. Handles the generic SSE plumbing shared by both
/// backends: chunk reading with timeout, line buffering, `data:` prefix
/// stripping, `[DONE]` detection, JSON parsing, and parse error diagnostics.
/// Yields parsed events as serde_json::Value — each backend handles its
/// own event types.
pub(crate) struct SseReader {
    line_buf: String,
    chunk_timeout: Duration,
    pub stream_start: Instant,
    pub chunks_received: u64,
    pub sse_lines_parsed: u64,
    pub sse_parse_errors: u64,
    debug: bool,
    done: bool,
    /// Serialized request payload — saved to disk on errors for replay debugging.
    pub(crate) request_json: Option<String>,
}

impl SseReader {
    pub(crate) fn new() -> Self {
        Self {
            line_buf: String::new(),
            chunk_timeout: Duration::from_secs(crate::config::get().api_stream_timeout_secs),
            stream_start: Instant::now(),
            chunks_received: 0,
            sse_lines_parsed: 0,
            sse_parse_errors: 0,
            debug: std::env::var("POC_DEBUG").is_ok(),
            done: false,
            request_json: None,
        }
    }

    /// Attach the serialized request payload for error diagnostics.
    /// Save the request payload to disk for replay debugging.
    fn save_failed_request(&self, reason: &str) {
        let Some(ref json) = self.request_json else { return };
        let log_dir = dirs::home_dir()
            .unwrap_or_default()
            .join(".consciousness/logs/failed-requests");
        let _ = std::fs::create_dir_all(&log_dir);
        let ts = chrono::Local::now().format("%Y%m%dT%H%M%S");
        let path = log_dir.join(format!("{}.json", ts));
        if std::fs::write(&path, json).is_ok() {
            dbglog!(
                "saved failed request to {} ({})", path.display(), reason
            );
        }
    }

    /// Read the next SSE event from the response stream.
    /// Returns Ok(Some(value)) for each parsed data line,
    /// Ok(None) when the stream ends or [DONE] is received.
    pub(crate) async fn next_event(
        &mut self,
        response: &mut HttpResponse,
    ) -> Result<Option<serde_json::Value>> {
        loop {
            // Drain complete lines from the buffer before reading more chunks
            while let Some(newline_pos) = self.line_buf.find('\n') {
                let line = self.line_buf[..newline_pos].trim().to_string();
                self.line_buf = self.line_buf[newline_pos + 1..].to_string();

                if line == "data: [DONE]" {
                    self.done = true;
                    return Ok(None);
                }
                if line.is_empty()
                    || line.starts_with("event: ")
                    || !line.starts_with("data: ")
                {
                    continue;
                }

                let json_str = &line[6..];
                self.sse_lines_parsed += 1;

                match serde_json::from_str(json_str) {
                    Ok(v) => return Ok(Some(v)),
                    Err(e) => {
                        self.sse_parse_errors += 1;
                        if self.sse_parse_errors == 1 || self.debug {
                            let preview = if json_str.len() > 200 {
                                format!("{}...", &json_str[..200])
                            } else {
                                json_str.to_string()
                            };
                            dbglog!(
                                "SSE parse error (#{}) {}: {}",
                                self.sse_parse_errors, e, preview
                            );
                        }
                        continue;
                    }
                }
            }

            if self.done {
                return Ok(None);
            }

            // Read more data from the response stream
            match tokio::time::timeout(self.chunk_timeout, response.chunk()).await {
                Ok(Ok(Some(chunk))) => {
                    self.chunks_received += 1;
                    self.line_buf.push_str(&String::from_utf8_lossy(&chunk));
                }
                Ok(Ok(None)) => return Ok(None),
                Ok(Err(e)) => {
                    let buf_preview = if self.line_buf.is_empty() {
                        "(empty)".to_string()
                    } else {
                        let n = self.line_buf.len().min(500);
                        format!("{}B: {}", self.line_buf.len(), &self.line_buf[..n])
                    };
                    let msg = format!(
                        "stream error after {} chunks, {:.1}s, {} sse lines: {} | buf: {}",
                        self.chunks_received,
                        self.stream_start.elapsed().as_secs_f64(),
                        self.sse_lines_parsed,
                        e, buf_preview,
                    );
                    dbglog!("{}", msg);
                    self.save_failed_request(&msg);
                    return Err(e.into());
                }
                Err(_) => {
                    let buf_preview = if self.line_buf.is_empty() {
                        "(empty)".to_string()
                    } else {
                        let n = self.line_buf.len().min(500);
                        format!("{}B: {}", self.line_buf.len(), &self.line_buf[..n])
                    };
                    let msg = format!(
                        "stream timeout: {}s, {} chunks, {} sse lines, {:.1}s elapsed | buf: {}",
                        self.chunk_timeout.as_secs(),
                        self.chunks_received,
                        self.sse_lines_parsed,
                        self.stream_start.elapsed().as_secs_f64(),
                        buf_preview,
                    );
                    dbglog!("{}", msg);
                    self.save_failed_request(&msg);
                    anyhow::bail!(
                        "stream timeout: no data for {}s ({} chunks received)",
                        self.chunk_timeout.as_secs(),
                        self.chunks_received
                    );
                }
            }
        }
    }
}