use bytes::Bytes;
use common::configuration::{Agent, AgentFilterChain};
use http_body_util::combinators::BoxBody;
use http_body_util::StreamBody;
use hyper::body::Frame;
use hyper::header::HeaderMap;
use opentelemetry::trace::TraceContextExt;
use opentelemetry::KeyValue;
use std::collections::HashMap;
use std::time::Instant;
use tokio::sync::mpsc;
use tokio_stream::wrappers::ReceiverStream;
use tokio_stream::StreamExt;
use tracing::{debug, info, warn, Instrument};
use tracing_opentelemetry::OpenTelemetrySpanExt;

use super::pipeline_processor::PipelineProcessor;
use crate::signals::{InteractionQuality, SignalAnalyzer, TextBasedSignalAnalyzer, FLAG_MARKER};
use crate::tracing::{llm, set_service_name, signals as signal_constants};
use hermesllm::apis::openai::{Message, MessageContent, Role};

/// Trait for processing streaming chunks
/// Implementors can inject custom logic during streaming (e.g., hallucination detection, logging)
pub trait StreamProcessor: Send + 'static {
    /// Process an incoming chunk of bytes
    fn process_chunk(&mut self, chunk: Bytes) -> Result<Option<Bytes>, String>;

    /// Called when the first bytes are received (for time-to-first-token tracking)
    fn on_first_bytes(&mut self) {}

    /// Called when streaming completes successfully
    fn on_complete(&mut self) {}

    /// Called when streaming encounters an error
    fn on_error(&mut self, _error: &str) {}
}

/// A processor that tracks streaming metrics
pub struct ObservableStreamProcessor {
    service_name: String,
    operation_name: String,
    total_bytes: usize,
    chunk_count: usize,
    start_time: Instant,
    time_to_first_token: Option<u128>,
    messages: Option<Vec<Message>>,
}

impl ObservableStreamProcessor {
    /// Create a new passthrough processor
    ///
    /// # Arguments
    /// * `service_name` - The service name for this span (e.g., "plano(llm)")
    ///   This will be set as the `service.name.override` attribute on the current span,
    ///   allowing the ServiceNameOverrideExporter to route spans to different services.
    /// * `operation_name` - The current span operation name (e.g., "POST /v1/chat/completions gpt-4")
    ///   Used to append the flag marker when concerning signals are detected.
    /// * `start_time` - When the request started (for duration calculation)
    /// * `messages` - Optional conversation messages for signal analysis
    pub fn new(
        service_name: impl Into<String>,
        operation_name: impl Into<String>,
        start_time: Instant,
        messages: Option<Vec<Message>>,
    ) -> Self {
        let service_name = service_name.into();

        // Set the service name override on the current span for OpenTelemetry export
        // This allows the ServiceNameOverrideExporter to route this span to the correct service
        set_service_name(&service_name);

        Self {
            service_name,
            operation_name: operation_name.into(),
            total_bytes: 0,
            chunk_count: 0,
            start_time,
            time_to_first_token: None,
            messages,
        }
    }
}

impl StreamProcessor for ObservableStreamProcessor {
    fn process_chunk(&mut self, chunk: Bytes) -> Result<Option<Bytes>, String> {
        self.total_bytes += chunk.len();
        self.chunk_count += 1;
        Ok(Some(chunk))
    }

    fn on_first_bytes(&mut self) {
        // Record time to first token (only for streaming)
        if self.time_to_first_token.is_none() {
            self.time_to_first_token = Some(self.start_time.elapsed().as_millis());
        }
    }

    fn on_complete(&mut self) {
        // Record time-to-first-token as an OTel span attribute + event (streaming only)
        if let Some(ttft) = self.time_to_first_token {
            let span = tracing::Span::current();
            let otel_context = span.context();
            let otel_span = otel_context.span();
            otel_span.set_attribute(KeyValue::new(llm::TIME_TO_FIRST_TOKEN_MS, ttft as i64));
            otel_span.add_event(
                llm::TIME_TO_FIRST_TOKEN_MS,
                vec![KeyValue::new(llm::TIME_TO_FIRST_TOKEN_MS, ttft as i64)],
            );
        }

        // Analyze signals if messages are available and record as span attributes
        if let Some(ref messages) = self.messages {
            let analyzer: Box<dyn SignalAnalyzer> = Box::new(TextBasedSignalAnalyzer::new());
            let report = analyzer.analyze(messages);

            // Get the current OTel span to set signal attributes
            let span = tracing::Span::current();
            let otel_context = span.context();
            let otel_span = otel_context.span();

            // Add overall quality
            otel_span.set_attribute(KeyValue::new(
                signal_constants::QUALITY,
                format!("{:?}", report.overall_quality),
            ));

            // Add repair/follow-up metrics if concerning
            if report.follow_up.is_concerning || report.follow_up.repair_count > 0 {
                otel_span.set_attribute(KeyValue::new(
                    signal_constants::REPAIR_COUNT,
                    report.follow_up.repair_count as i64,
                ));
                otel_span.set_attribute(KeyValue::new(
                    signal_constants::REPAIR_RATIO,
                    format!("{:.3}", report.follow_up.repair_ratio),
                ));
            }

            // Add frustration metrics
            if report.frustration.has_frustration {
                otel_span.set_attribute(KeyValue::new(
                    signal_constants::FRUSTRATION_COUNT,
                    report.frustration.frustration_count as i64,
                ));
                otel_span.set_attribute(KeyValue::new(
                    signal_constants::FRUSTRATION_SEVERITY,
                    report.frustration.severity as i64,
                ));
            }

            // Add repetition metrics
            if report.repetition.has_looping {
                otel_span.set_attribute(KeyValue::new(
                    signal_constants::REPETITION_COUNT,
                    report.repetition.repetition_count as i64,
                ));
            }

            // Add escalation metrics
            if report.escalation.escalation_requested {
                otel_span
                    .set_attribute(KeyValue::new(signal_constants::ESCALATION_REQUESTED, true));
            }

            // Add positive feedback metrics
            if report.positive_feedback.has_positive_feedback {
                otel_span.set_attribute(KeyValue::new(
                    signal_constants::POSITIVE_FEEDBACK_COUNT,
                    report.positive_feedback.positive_count as i64,
                ));
            }

            // Flag the span name if any concerning signal is detected
            let should_flag = report.frustration.has_frustration
                || report.repetition.has_looping
                || report.escalation.escalation_requested
                || matches!(
                    report.overall_quality,
                    InteractionQuality::Poor | InteractionQuality::Severe
                );

            if should_flag {
                otel_span.update_name(format!("{} {}", self.operation_name, FLAG_MARKER));
            }
        }

        info!(
            service = %self.service_name,
            total_bytes = self.total_bytes,
            chunk_count = self.chunk_count,
            duration_ms = self.start_time.elapsed().as_millis(),
            time_to_first_token_ms = ?self.time_to_first_token,
            "streaming completed"
        );
    }

    fn on_error(&mut self, error_msg: &str) {
        warn!(
            service = %self.service_name,
            error = error_msg,
            duration_ms = self.start_time.elapsed().as_millis(),
            "stream error"
        );
    }
}

/// Result of creating a streaming response
pub struct StreamingResponse {
    pub body: BoxBody<Bytes, hyper::Error>,
    pub processor_handle: tokio::task::JoinHandle<()>,
}

pub fn create_streaming_response<S, P>(
    mut byte_stream: S,
    mut processor: P,
    buffer_size: usize,
) -> StreamingResponse
where
    S: StreamExt<Item = Result<Bytes, reqwest::Error>> + Send + Unpin + 'static,
    P: StreamProcessor,
{
    let (tx, rx) = mpsc::channel::<Bytes>(buffer_size);

    // Capture the current span so the spawned task inherits the request context
    let current_span = tracing::Span::current();

    // Spawn a task to process and forward chunks
    let processor_handle = tokio::spawn(
        async move {
            let mut is_first_chunk = true;

            while let Some(item) = byte_stream.next().await {
                let chunk = match item {
                    Ok(chunk) => chunk,
                    Err(err) => {
                        let err_msg = format!("Error receiving chunk: {:?}", err);
                        warn!(error = %err_msg, "stream error");
                        processor.on_error(&err_msg);
                        break;
                    }
                };

                // Call on_first_bytes for the first chunk
                if is_first_chunk {
                    processor.on_first_bytes();
                    is_first_chunk = false;
                }

                // Process the chunk
                match processor.process_chunk(chunk) {
                    Ok(Some(processed_chunk)) => {
                        if tx.send(processed_chunk).await.is_err() {
                            warn!("receiver dropped");
                            break;
                        }
                    }
                    Ok(None) => {
                        // Skip this chunk
                        continue;
                    }
                    Err(err) => {
                        warn!("processor error: {}", err);
                        processor.on_error(&err);
                        break;
                    }
                }
            }

            processor.on_complete();
        }
        .instrument(current_span),
    );

    // Convert channel receiver to HTTP stream
    let stream = ReceiverStream::new(rx).map(|chunk| Ok::<_, hyper::Error>(Frame::data(chunk)));
    let stream_body = BoxBody::new(StreamBody::new(stream));

    StreamingResponse {
        body: stream_body,
        processor_handle,
    }
}

/// Extract content text from an SSE chunk line (the JSON part after "data: ").
/// Returns the content string and whether it was found.
fn extract_sse_content(json_str: &str) -> Option<String> {
    let value: serde_json::Value = serde_json::from_str(json_str).ok()?;
    value
        .get("choices")?
        .get(0)?
        .get("delta")?
        .get("content")?
        .as_str()
        .map(|s| s.to_string())
}

/// Replace content in an SSE JSON chunk with new content.
fn replace_sse_content(json_str: &str, new_content: &str) -> Option<String> {
    let mut value: serde_json::Value = serde_json::from_str(json_str).ok()?;
    value
        .get_mut("choices")?
        .get_mut(0)?
        .get_mut("delta")?
        .as_object_mut()?
        .insert(
            "content".to_string(),
            serde_json::Value::String(new_content.to_string()),
        );
    serde_json::to_string(&value).ok()
}

/// Process an SSE chunk through the output filter chain.
/// Parses each `data: ` line, extracts content, sends through filters, and reconstructs.
async fn filter_sse_chunk(
    chunk_str: &str,
    pipeline_processor: &mut PipelineProcessor,
    filter_chain: &AgentFilterChain,
    filter_agents: &HashMap<String, Agent>,
    request_headers: &HeaderMap,
) -> String {
    let mut result = String::new();
    for line in chunk_str.split('\n') {
        if let Some(json_str) = line.strip_prefix("data: ") {
            if json_str.trim() == "[DONE]" {
                result.push_str(line);
                result.push('\n');
                continue;
            }
            if let Some(content) = extract_sse_content(json_str) {
                if content.is_empty() {
                    result.push_str(line);
                    result.push('\n');
                    continue;
                }
                // Send content through output filter chain
                let messages = vec![Message {
                    role: Role::Assistant,
                    content: Some(MessageContent::Text(content)),
                    name: None,
                    tool_calls: None,
                    tool_call_id: None,
                }];
                match pipeline_processor
                    .process_filter_chain(&messages, filter_chain, filter_agents, request_headers)
                    .await
                {
                    Ok(filtered_messages) => {
                        if let Some(msg) = filtered_messages.first() {
                            let filtered_content = match &msg.content {
                                Some(MessageContent::Text(t)) => Some(t.clone()),
                                _ => None,
                            };
                            if let Some(filtered_content) = filtered_content {
                                if let Some(new_json) =
                                    replace_sse_content(json_str, &filtered_content)
                                {
                                    result.push_str("data: ");
                                    result.push_str(&new_json);
                                    result.push('\n');
                                    continue;
                                }
                            }
                        }
                        // Fallback: pass through original
                        result.push_str(line);
                        result.push('\n');
                    }
                    Err(e) => {
                        warn!(error = %e, "output filter chain error, passing through original chunk");
                        result.push_str(line);
                        result.push('\n');
                    }
                }
            } else {
                // No content in this SSE line, pass through
                result.push_str(line);
                result.push('\n');
            }
        } else {
            result.push_str(line);
            result.push('\n');
        }
    }
    // Remove trailing extra newline if the original didn't end with one
    if !chunk_str.ends_with('\n') && result.ends_with('\n') {
        result.pop();
    }
    result
}

/// Process a non-streaming JSON response through the output filter chain.
/// Extracts assistant message content, filters it, and reconstructs the response.
pub async fn filter_non_streaming_response(
    response_bytes: &[u8],
    pipeline_processor: &mut PipelineProcessor,
    filter_chain: &AgentFilterChain,
    filter_agents: &HashMap<String, Agent>,
    request_headers: &HeaderMap,
) -> Bytes {
    let response_str = match std::str::from_utf8(response_bytes) {
        Ok(s) => s,
        Err(_) => return Bytes::from(response_bytes.to_vec()),
    };

    let mut value: serde_json::Value = match serde_json::from_str(response_str) {
        Ok(v) => v,
        Err(_) => return Bytes::from(response_bytes.to_vec()),
    };

    // Extract content from choices[0].message.content
    let content = value
        .get("choices")
        .and_then(|c| c.get(0))
        .and_then(|c| c.get("message"))
        .and_then(|m| m.get("content"))
        .and_then(|c| c.as_str())
        .map(|s| s.to_string());

    if let Some(content) = content {
        let messages = vec![Message {
            role: Role::Assistant,
            content: Some(MessageContent::Text(content)),
            name: None,
            tool_calls: None,
            tool_call_id: None,
        }];
        match pipeline_processor
            .process_filter_chain(&messages, filter_chain, filter_agents, request_headers)
            .await
        {
            Ok(filtered_messages) => {
                if let Some(msg) = filtered_messages.first() {
                    let filtered_content = match &msg.content {
                        Some(MessageContent::Text(t)) => Some(t.clone()),
                        _ => None,
                    };
                    if let Some(filtered_content) = filtered_content {
                        if let Some(choices) = value.get_mut("choices") {
                            if let Some(choice) = choices.get_mut(0) {
                                if let Some(message) = choice.get_mut("message") {
                                    message.as_object_mut().unwrap().insert(
                                        "content".to_string(),
                                        serde_json::Value::String(filtered_content),
                                    );
                                }
                            }
                        }
                    }
                }
            }
            Err(e) => {
                warn!(error = %e, "output filter chain error on non-streaming response");
            }
        }
    }

    Bytes::from(serde_json::to_string(&value).unwrap_or_else(|_| response_str.to_string()))
}

/// Creates a streaming response that processes each chunk through output filters.
/// The output filter is called asynchronously for each SSE chunk's content.
pub fn create_streaming_response_with_output_filter<S, P>(
    mut byte_stream: S,
    mut inner_processor: P,
    buffer_size: usize,
    output_filters: Vec<String>,
    output_filter_agents: HashMap<String, Agent>,
    request_headers: HeaderMap,
) -> StreamingResponse
where
    S: StreamExt<Item = Result<Bytes, reqwest::Error>> + Send + Unpin + 'static,
    P: StreamProcessor,
{
    let (tx, rx) = mpsc::channel::<Bytes>(buffer_size);
    let current_span = tracing::Span::current();

    let processor_handle = tokio::spawn(
        async move {
            let mut is_first_chunk = true;
            let mut pipeline_processor = PipelineProcessor::default();
            let temp_filter_chain = AgentFilterChain {
                id: "output_filter".to_string(),
                default: None,
                description: None,
                filter_chain: Some(output_filters),
            };

            while let Some(item) = byte_stream.next().await {
                let chunk = match item {
                    Ok(chunk) => chunk,
                    Err(err) => {
                        let err_msg = format!("Error receiving chunk: {:?}", err);
                        warn!(error = %err_msg, "stream error");
                        inner_processor.on_error(&err_msg);
                        break;
                    }
                };

                if is_first_chunk {
                    inner_processor.on_first_bytes();
                    is_first_chunk = false;
                }

                // Try to process through output filter chain
                let processed_chunk = if let Ok(chunk_str) = std::str::from_utf8(&chunk) {
                    if chunk_str.contains("data: ") {
                        let filtered = filter_sse_chunk(
                            chunk_str,
                            &mut pipeline_processor,
                            &temp_filter_chain,
                            &output_filter_agents,
                            &request_headers,
                        )
                        .await;
                        Bytes::from(filtered)
                    } else {
                        // Non-SSE chunk (could be non-streaming JSON response)
                        let filtered = filter_non_streaming_response(
                            &chunk,
                            &mut pipeline_processor,
                            &temp_filter_chain,
                            &output_filter_agents,
                            &request_headers,
                        )
                        .await;
                        filtered
                    }
                } else {
                    chunk
                };

                // Pass through inner processor for metrics/observability
                match inner_processor.process_chunk(processed_chunk) {
                    Ok(Some(final_chunk)) => {
                        if tx.send(final_chunk).await.is_err() {
                            warn!("receiver dropped");
                            break;
                        }
                    }
                    Ok(None) => continue,
                    Err(err) => {
                        warn!("processor error: {}", err);
                        inner_processor.on_error(&err);
                        break;
                    }
                }
            }

            inner_processor.on_complete();
            debug!("output filter streaming completed");
        }
        .instrument(current_span),
    );

    let stream = ReceiverStream::new(rx).map(|chunk| Ok::<_, hyper::Error>(Frame::data(chunk)));
    let stream_body = BoxBody::new(StreamBody::new(stream));

    StreamingResponse {
        body: stream_body,
        processor_handle,
    }
}

/// Truncates a message to the specified maximum length, adding "..." if truncated.
pub fn truncate_message(message: &str, max_length: usize) -> String {
    if message.chars().count() > max_length {
        let truncated: String = message.chars().take(max_length).collect();
        format!("{}...", truncated)
    } else {
        message.to_string()
    }
}