use std::collections::HashMap;
use std::sync::Arc;

use mistralai_client::v1::client::Client as MistralClient;
use mistralai_client::v1::conversations::{
    AppendConversationRequest, ConversationInput, ConversationResponse,
    CreateConversationRequest,
};
use tokio::sync::Mutex;
use tracing::{debug, info, warn};

use crate::persistence::Store;

/// Maps Matrix room IDs to Mistral conversation IDs.
/// Group rooms get a shared conversation; DMs are per-room (already unique per DM pair).
/// State is persisted to SQLite so mappings survive reboots.
pub struct ConversationRegistry {
    /// room_id → conversation_id (in-memory cache, backed by SQLite)
    mapping: Mutex<HashMap<String, ConversationState>>,
    /// Agent ID to use when creating new conversations (orchestrator or None for model-only).
    agent_id: Mutex<Option<String>>,
    /// Model to use when no agent is configured.
    model: String,
    /// Token budget before compaction triggers (% of model context window).
    compaction_threshold: u32,
    /// SQLite persistence.
    store: Arc<Store>,
}

struct ConversationState {
    conversation_id: String,
    /// Estimated token count (incremented per message, reset on compaction).
    estimated_tokens: u32,
}

impl ConversationRegistry {
    pub fn new(model: String, compaction_threshold: u32, store: Arc<Store>) -> Self {
        // Load existing mappings from SQLite
        let persisted = store.load_all_conversations();
        let mut mapping = HashMap::new();
        for (room_id, conversation_id, estimated_tokens) in persisted {
            mapping.insert(
                room_id,
                ConversationState {
                    conversation_id,
                    estimated_tokens,
                },
            );
        }
        let count = mapping.len();
        if count > 0 {
            info!(count, "Restored conversation mappings from database");
        }

        Self {
            mapping: Mutex::new(mapping),
            agent_id: Mutex::new(None),
            model,
            compaction_threshold,
            store,
        }
    }

    /// Set the orchestrator agent ID (called after agent registry creates it).
    pub async fn set_agent_id(&self, agent_id: String) {
        let mut id = self.agent_id.lock().await;
        *id = Some(agent_id);
    }

    /// Get or create a conversation for a room. Returns the conversation ID.
    /// If a conversation doesn't exist yet, creates one with the first message.
    pub async fn send_message(
        &self,
        room_id: &str,
        message: ConversationInput,
        is_dm: bool,
        mistral: &MistralClient,
    ) -> Result<ConversationResponse, String> {
        let mut mapping = self.mapping.lock().await;

        if let Some(state) = mapping.get_mut(room_id) {
            // Existing conversation — append
            let req = AppendConversationRequest {
                inputs: message,
                completion_args: None,
                handoff_execution: None,
                store: Some(true),
                tool_confirmations: None,
                stream: false,
            };

            let response = mistral
                .append_conversation_async(&state.conversation_id, &req)
                .await
                .map_err(|e| format!("append_conversation failed: {}", e.message))?;

            // Update token estimate
            state.estimated_tokens += response.usage.total_tokens;
            self.store.update_tokens(room_id, state.estimated_tokens);

            debug!(
                room = room_id,
                conversation_id = state.conversation_id.as_str(),
                tokens = state.estimated_tokens,
                "Appended to conversation"
            );

            Ok(response)
        } else {
            // New conversation — create
            let agent_id = self.agent_id.lock().await.clone();

            let req = CreateConversationRequest {
                inputs: message,
                model: if agent_id.is_none() {
                    Some(self.model.clone())
                } else {
                    None
                },
                agent_id,
                agent_version: None,
                name: Some(format!("sol-{}", room_id)),
                description: None,
                instructions: None,
                completion_args: None,
                tools: None,
                handoff_execution: None,
                metadata: None,
                store: Some(true),
                stream: false,
            };

            let response = mistral
                .create_conversation_async(&req)
                .await
                .map_err(|e| format!("create_conversation failed: {}", e.message))?;

            let conv_id = response.conversation_id.clone();
            let tokens = response.usage.total_tokens;
            info!(
                room = room_id,
                conversation_id = conv_id.as_str(),
                "Created new conversation"
            );

            self.store.upsert_conversation(room_id, &conv_id, tokens);

            mapping.insert(
                room_id.to_string(),
                ConversationState {
                    conversation_id: conv_id,
                    estimated_tokens: tokens,
                },
            );

            Ok(response)
        }
    }

    /// Send a function result back to a conversation.
    pub async fn send_function_result(
        &self,
        room_id: &str,
        entries: Vec<mistralai_client::v1::conversations::ConversationEntry>,
        mistral: &MistralClient,
    ) -> Result<ConversationResponse, String> {
        let mapping = self.mapping.lock().await;
        let state = mapping
            .get(room_id)
            .ok_or_else(|| format!("no conversation for room {room_id}"))?;

        let req = AppendConversationRequest {
            inputs: ConversationInput::Entries(entries),
            completion_args: None,
            handoff_execution: None,
            store: Some(true),
            tool_confirmations: None,
            stream: false,
        };

        mistral
            .append_conversation_async(&state.conversation_id, &req)
            .await
            .map_err(|e| format!("append_conversation (function result) failed: {}", e.message))
    }

    /// Check if a room's conversation needs compaction.
    pub async fn needs_compaction(&self, room_id: &str) -> bool {
        let mapping = self.mapping.lock().await;
        if let Some(state) = mapping.get(room_id) {
            state.estimated_tokens >= self.compaction_threshold
        } else {
            false
        }
    }

    /// Reset a room's conversation (e.g., after compaction).
    /// Removes the mapping so the next message creates a fresh conversation.
    pub async fn reset(&self, room_id: &str) {
        let mut mapping = self.mapping.lock().await;
        if let Some(state) = mapping.remove(room_id) {
            self.store.delete_conversation(room_id);
            info!(
                room = room_id,
                conversation_id = state.conversation_id.as_str(),
                tokens = state.estimated_tokens,
                "Reset conversation (compaction)"
            );
        }
    }

    /// Get the conversation ID for a room, if one exists.
    pub async fn get_conversation_id(&self, room_id: &str) -> Option<String> {
        let mapping = self.mapping.lock().await;
        mapping.get(room_id).map(|s| s.conversation_id.clone())
    }

    /// Number of active conversations.
    pub async fn active_count(&self) -> usize {
        self.mapping.lock().await.len()
    }
}

/// Merge multiple buffered user messages into a single conversation input.
/// For DMs: raw text concatenation with newlines.
/// For group rooms: prefix each line with `<sender_matrix_id>`.
pub fn merge_user_messages(
    messages: &[(String, String)], // (sender_matrix_id, body)
    is_dm: bool,
) -> String {
    if messages.is_empty() {
        return String::new();
    }

    if is_dm {
        // DMs: just concatenate
        messages
            .iter()
            .map(|(_, body)| body.as_str())
            .collect::<Vec<_>>()
            .join("\n")
    } else {
        // Group rooms: prefix with sender
        messages
            .iter()
            .map(|(sender, body)| format!("<{sender}> {body}"))
            .collect::<Vec<_>>()
            .join("\n")
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_merge_dm_messages() {
        let msgs = vec![
            ("@alice:example.com".to_string(), "hello".to_string()),
            ("@alice:example.com".to_string(), "how are you?".to_string()),
        ];
        let merged = merge_user_messages(&msgs, true);
        assert_eq!(merged, "hello\nhow are you?");
    }

    #[test]
    fn test_merge_group_messages() {
        let msgs = vec![
            ("@sienna:sunbeam.pt".to_string(), "what's the error rate?".to_string()),
            ("@lonni:sunbeam.pt".to_string(), "also check memory".to_string()),
            ("@sienna:sunbeam.pt".to_string(), "and disk too".to_string()),
        ];
        let merged = merge_user_messages(&msgs, false);
        assert_eq!(
            merged,
            "<@sienna:sunbeam.pt> what's the error rate?\n<@lonni:sunbeam.pt> also check memory\n<@sienna:sunbeam.pt> and disk too"
        );
    }

    #[test]
    fn test_merge_empty() {
        let merged = merge_user_messages(&[], true);
        assert_eq!(merged, "");
    }

    #[test]
    fn test_merge_single_dm() {
        let msgs = vec![("@user:x".to_string(), "hi".to_string())];
        let merged = merge_user_messages(&msgs, true);
        assert_eq!(merged, "hi");
    }

    #[test]
    fn test_merge_single_group() {
        let msgs = vec![("@user:x".to_string(), "hi".to_string())];
        let merged = merge_user_messages(&msgs, false);
        assert_eq!(merged, "<@user:x> hi");
    }
}