use crate::bus::message::ContentBlock;
use crate::bus::ChatMessage;
use crate::config::LLMProviderConfig;
use crate::observability::{
    truncate_args, Observer, ObserverEvent, ToolExecutionOutcome,
};
use crate::providers::{create_provider, LLMProvider, ChatCompletionRequest, Message, ToolCall};
use crate::tools::ToolRegistry;
use std::io::Read;
use std::sync::Arc;
use std::time::Instant;

/// Build content blocks from text and media paths
fn build_content_blocks(text: &str, media_paths: &[String]) -> Vec<ContentBlock> {
    let mut blocks = Vec::new();

    // Add text block if there's text
    if !text.is_empty() {
        blocks.push(ContentBlock::text(text));
    }

    // Add image blocks for media paths
    for path in media_paths {
        if let Ok((mime_type, base64_data)) = encode_image_to_base64(path) {
            let url = format!("data:{};base64,{}", mime_type, base64_data);
            blocks.push(ContentBlock::image_url(url));
        }
    }

    // If nothing, add empty text block
    if blocks.is_empty() {
        blocks.push(ContentBlock::text(""));
    }

    blocks
}

/// Encode an image file to base64 data URL
fn encode_image_to_base64(path: &str) -> Result<(String, String), std::io::Error> {
    use base64::{Engine as _, engine::general_purpose::STANDARD};

    let mut file = std::fs::File::open(path)?;
    let mut buffer = Vec::new();
    file.read_to_end(&mut buffer)?;

    let mime = mime_guess::from_path(path)
        .first_or_octet_stream()
        .to_string();

    let encoded = STANDARD.encode(&buffer);
    Ok((mime, encoded))
}

/// Convert ChatMessage to LLM Message format
fn chat_message_to_llm_message(m: &ChatMessage) -> Message {
    let content = if m.media_refs.is_empty() {
        vec![ContentBlock::text(&m.content)]
    } else {
        build_content_blocks(&m.content, &m.media_refs)
    };

    Message {
        role: m.role.clone(),
        content,
        tool_call_id: m.tool_call_id.clone(),
        name: m.tool_name.clone(),
    }
}

/// AgentLoop - Stateless agent that processes messages with tool calling support.
/// History is managed externally by SessionManager.
pub struct AgentLoop {
    provider: Box<dyn LLMProvider>,
    tools: Arc<ToolRegistry>,
    observer: Option<Arc<dyn Observer>>,
    max_iterations: usize,
}

impl AgentLoop {
    pub fn new(provider_config: LLMProviderConfig) -> Result<Self, AgentError> {
        let max_iterations = provider_config.max_tool_iterations;
        let provider = create_provider(provider_config)
            .map_err(|e| AgentError::ProviderCreation(e.to_string()))?;

        Ok(Self {
            provider,
            tools: Arc::new(ToolRegistry::new()),
            observer: None,
            max_iterations,
        })
    }

    pub fn with_tools(provider_config: LLMProviderConfig, tools: Arc<ToolRegistry>) -> Result<Self, AgentError> {
        let max_iterations = provider_config.max_tool_iterations;
        let provider = create_provider(provider_config)
            .map_err(|e| AgentError::ProviderCreation(e.to_string()))?;

        Ok(Self {
            provider,
            tools,
            observer: None,
            max_iterations,
        })
    }

    /// Set an observer for tracking events.
    pub fn with_observer(mut self, observer: Arc<dyn Observer>) -> Self {
        self.observer = Some(observer);
        self
    }

    pub fn tools(&self) -> &Arc<ToolRegistry> {
        &self.tools
    }

    /// Process a message using the provided conversation history.
    /// History management is handled externally by SessionManager.
    ///
    /// This method supports multi-round tool calling: after executing tools,
    /// it loops back to the LLM with the tool results until either:
    /// - The LLM returns no more tool calls (final response)
    /// - Maximum iterations are reached
    pub async fn process(&self, mut messages: Vec<ChatMessage>) -> Result<ChatMessage, AgentError> {
        #[cfg(debug_assertions)]
        tracing::debug!(history_len = messages.len(), max_iterations = self.max_iterations, "Starting agent process");

        for iteration in 0..self.max_iterations {
            #[cfg(debug_assertions)]
            tracing::debug!(iteration, "Agent iteration started");

            // Convert messages to LLM format
            let messages_for_llm: Vec<Message> = messages
                .iter()
                .map(chat_message_to_llm_message)
                .collect();

            // Build request
            let tools = if self.tools.has_tools() {
                Some(self.tools.get_definitions())
            } else {
                None
            };

            let request = ChatCompletionRequest {
                messages: messages_for_llm,
                temperature: None,
                max_tokens: None,
                tools,
            };

            // Call LLM
            let response = (*self.provider).chat(request).await
                .map_err(|e| {
                    tracing::error!(error = %e, "LLM request failed");
                    AgentError::LlmError(e.to_string())
                })?;

            #[cfg(debug_assertions)]
            tracing::debug!(
                iteration,
                response_len = response.content.len(),
                tool_calls_len = response.tool_calls.len(),
                "LLM response received"
            );

            // If no tool calls, this is the final response
            if response.tool_calls.is_empty() {
                let assistant_message = ChatMessage::assistant(response.content);
                return Ok(assistant_message);
            }

            // Execute tool calls
            tracing::info!(iteration, count = response.tool_calls.len(), "Tool calls detected, executing tools");

            // Add assistant message with tool calls
            let assistant_message = ChatMessage::assistant(response.content.clone());
            messages.push(assistant_message.clone());

            // Execute tools and add results to messages
            let tool_results = self.execute_tools(&response.tool_calls).await;

            for (tool_call, result) in response.tool_calls.iter().zip(tool_results.iter()) {
                let tool_message = ChatMessage::tool(
                    tool_call.id.clone(),
                    tool_call.name.clone(),
                    result.output.clone(),
                );
                messages.push(tool_message);
            }

            // Loop continues to next iteration with updated messages
            #[cfg(debug_assertions)]
            tracing::debug!(iteration, message_count = messages.len(), "Tool execution complete, continuing to next iteration");
        }

        // Max iterations reached
        let final_message = ChatMessage::assistant(
            format!("I reached the maximum number of tool call iterations ({}) without completing the task. Please try breaking the task into smaller steps.", self.max_iterations)
        );
        Ok(final_message)
    }

    /// Determine whether to execute tools in parallel or sequentially.
    ///
    /// Returns true if:
    /// - There are multiple tool calls
    /// - None of the tools require sequential execution (tool_search, non-concurrency-safe)
    fn should_execute_in_parallel(&self, tool_calls: &[ToolCall]) -> bool {
        if tool_calls.len() <= 1 {
            return false;
        }

        // tool_search must run sequentially to avoid MCP activation race conditions
        if tool_calls.iter().any(|tc| tc.name == "tool_search") {
            return false;
        }

        // All tools must be concurrency-safe to run in parallel
        tool_calls.iter().all(|tc| {
            self.tools
                .get(&tc.name)
                .map(|t| t.concurrency_safe())
                .unwrap_or(false)
        })
    }

    /// Execute multiple tool calls, choosing parallel or sequential based on conditions.
    async fn execute_tools(&self, tool_calls: &[ToolCall]) -> Vec<ToolExecutionOutcome> {
        if self.should_execute_in_parallel(tool_calls) {
            tracing::debug!("Executing {} tools in parallel", tool_calls.len());
            self.execute_tools_parallel(tool_calls).await
        } else {
            tracing::debug!("Executing {} tools sequentially", tool_calls.len());
            self.execute_tools_sequential(tool_calls).await
        }
    }

    /// Execute tools in parallel using join_all.
    async fn execute_tools_parallel(&self, tool_calls: &[ToolCall]) -> Vec<ToolExecutionOutcome> {
        let futures: Vec<_> = tool_calls
            .iter()
            .map(|tc| self.execute_one_tool(tc))
            .collect();

        futures_util::future::join_all(futures).await
    }

    /// Execute tools sequentially.
    async fn execute_tools_sequential(&self, tool_calls: &[ToolCall]) -> Vec<ToolExecutionOutcome> {
        let mut outcomes = Vec::with_capacity(tool_calls.len());

        for tool_call in tool_calls {
            outcomes.push(self.execute_one_tool(tool_call).await);
        }

        outcomes
    }

    /// Execute a single tool and return the outcome with event tracking.
    async fn execute_one_tool(&self, tool_call: &ToolCall) -> ToolExecutionOutcome {
        let start = Instant::now();
        let tool_name = tool_call.name.clone();

        // Record ToolCallStart event
        if let Some(ref observer) = self.observer {
            observer.record_event(&ObserverEvent::ToolCallStart {
                tool: tool_name.clone(),
                arguments: Some(truncate_args(&tool_call.arguments, 300)),
            });
        }

        let result = self.execute_tool_internal(tool_call).await;
        let duration = start.elapsed();

        // Record ToolCall event
        if let Some(ref observer) = self.observer {
            observer.record_event(&ObserverEvent::ToolCall {
                tool: tool_name.clone(),
                duration,
                success: result.success,
            });
        }

        // Apply duration
        ToolExecutionOutcome {
            duration,
            ..result
        }
    }

    /// Internal tool execution without event tracking.
    async fn execute_tool_internal(&self, tool_call: &ToolCall) -> ToolExecutionOutcome {
        let tool = match self.tools.get(&tool_call.name) {
            Some(t) => t,
            None => {
                tracing::warn!(tool = %tool_call.name, "Tool not found");
                return ToolExecutionOutcome::failure(
                    format!("Error: Tool '{}' not found", tool_call.name),
                    Some(format!("Tool '{}' not found", tool_call.name)),
                );
            }
        };

        match tool.execute(tool_call.arguments.clone()).await {
            Ok(result) => {
                if result.success {
                    ToolExecutionOutcome::success(result.output)
                } else {
                    let error = result.error.unwrap_or_default();
                    ToolExecutionOutcome::failure(
                        format!("Error: {}", error),
                        Some(error),
                    )
                }
            }
            Err(e) => {
                tracing::error!(tool = %tool_call.name, error = %e, "Tool execution failed");
                ToolExecutionOutcome::failure(
                    format!("Error: {}", e),
                    Some(e.to_string()),
                )
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::observability::{MultiObserver, Observer};

    struct TestObserver {
        events: std::sync::Mutex<Vec<ObserverEvent>>,
    }

    impl TestObserver {
        fn new() -> Self {
            Self {
                events: std::sync::Mutex::new(Vec::new()),
            }
        }
    }

    impl Observer for TestObserver {
        fn record_event(&self, event: &ObserverEvent) {
            self.events.lock().unwrap().push(event.clone());
        }

        fn name(&self) -> &str {
            "test_observer"
        }
    }

    #[tokio::test]
    async fn test_observer_receives_tool_events() {
        // Verify MultiObserver works
        let mut multi = MultiObserver::new();
        multi.add_observer(Box::new(TestObserver::new()));

        let event = ObserverEvent::ToolCallStart {
            tool: "test".to_string(),
            arguments: Some("{}".to_string()),
        };
        multi.record_event(&event);

        // Just verify the structure works
        assert_eq!(multi.len(), 1);
    }

    #[test]
    fn test_should_execute_in_parallel_single_tool() {
        // Would need a proper setup with AgentLoop to test fully
        // For now, just verify the logic: single tool should return false
        let calls = vec![ToolCall {
            id: "1".to_string(),
            name: "test".to_string(),
            arguments: serde_json::json!({}),
        }];

        // If there's only 1 tool, should return false regardless
        assert_eq!(calls.len() <= 1, true);
    }
}

#[derive(Debug)]
pub enum AgentError {
    ProviderCreation(String),
    LlmError(String),
    Other(String),
}

impl std::fmt::Display for AgentError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            AgentError::ProviderCreation(e) => write!(f, "Provider creation error: {}", e),
            AgentError::LlmError(e) => write!(f, "LLM error: {}", e),
            AgentError::Other(e) => write!(f, "{}", e),
        }
    }
}

impl std::error::Error for AgentError {}