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

use codex_core::ConversationManager;
use codex_core::NewConversation;
use codex_core::config::Config;
use codex_core::config::ConfigOverrides;
use mcp_types::JSONRPCErrorError;
use mcp_types::RequestId;
use tokio::sync::oneshot;
use uuid::Uuid;

use crate::error_code::INTERNAL_ERROR_CODE;
use crate::error_code::INVALID_REQUEST_ERROR_CODE;
use crate::json_to_toml::json_to_toml;
use crate::outgoing_message::OutgoingMessageSender;
use crate::outgoing_message::OutgoingNotificationMeta;
use crate::wire_format::AddConversationListenerParams;
use crate::wire_format::AddConversationSubscriptionResponse;
use crate::wire_format::CodexRequest;
use crate::wire_format::ConversationId;
use crate::wire_format::InputItem as WireInputItem;
use crate::wire_format::NewConversationParams;
use crate::wire_format::NewConversationResponse;
use crate::wire_format::RemoveConversationListenerParams;
use crate::wire_format::RemoveConversationSubscriptionResponse;
use crate::wire_format::SendUserMessageParams;
use crate::wire_format::SendUserMessageResponse;
use codex_core::protocol::InputItem as CoreInputItem;
use codex_core::protocol::Op;

/// Handles JSON-RPC messages for Codex conversations.
pub(crate) struct CodexMessageProcessor {
    conversation_manager: Arc<ConversationManager>,
    outgoing: Arc<OutgoingMessageSender>,
    codex_linux_sandbox_exe: Option<PathBuf>,
    conversation_listeners: HashMap<Uuid, oneshot::Sender<()>>,
}

impl CodexMessageProcessor {
    pub fn new(
        conversation_manager: Arc<ConversationManager>,
        outgoing: Arc<OutgoingMessageSender>,
        codex_linux_sandbox_exe: Option<PathBuf>,
    ) -> Self {
        Self {
            conversation_manager,
            outgoing,
            codex_linux_sandbox_exe,
            conversation_listeners: HashMap::new(),
        }
    }

    pub async fn process_request(&mut self, request: CodexRequest) {
        match request {
            CodexRequest::NewConversation { request_id, params } => {
                // Do not tokio::spawn() to process new_conversation()
                // asynchronously because we need to ensure the conversation is
                // created before processing any subsequent messages.
                self.process_new_conversation(request_id, params).await;
            }
            CodexRequest::SendUserMessage { request_id, params } => {
                self.send_user_message(request_id, params).await;
            }
            CodexRequest::AddConversationListener { request_id, params } => {
                self.add_conversation_listener(request_id, params).await;
            }
            CodexRequest::RemoveConversationListener { request_id, params } => {
                self.remove_conversation_listener(request_id, params).await;
            }
        }
    }

    async fn process_new_conversation(&self, request_id: RequestId, params: NewConversationParams) {
        let config = match derive_config_from_params(params, self.codex_linux_sandbox_exe.clone()) {
            Ok(config) => config,
            Err(err) => {
                let error = JSONRPCErrorError {
                    code: INVALID_REQUEST_ERROR_CODE,
                    message: format!("error deriving config: {err}"),
                    data: None,
                };
                self.outgoing.send_error(request_id, error).await;
                return;
            }
        };

        match self.conversation_manager.new_conversation(config).await {
            Ok(conversation_id) => {
                let NewConversation {
                    conversation_id,
                    session_configured,
                    ..
                } = conversation_id;
                let response = NewConversationResponse {
                    conversation_id: ConversationId(conversation_id),
                    model: session_configured.model,
                };
                self.outgoing.send_response(request_id, response).await;
            }
            Err(err) => {
                let error = JSONRPCErrorError {
                    code: INTERNAL_ERROR_CODE,
                    message: format!("error creating conversation: {err}"),
                    data: None,
                };
                self.outgoing.send_error(request_id, error).await;
            }
        }
    }

    async fn send_user_message(&self, request_id: RequestId, params: SendUserMessageParams) {
        let SendUserMessageParams {
            conversation_id,
            items,
        } = params;
        let Ok(conversation) = self
            .conversation_manager
            .get_conversation(conversation_id.0)
            .await
        else {
            let error = JSONRPCErrorError {
                code: INVALID_REQUEST_ERROR_CODE,
                message: format!("conversation not found: {conversation_id}"),
                data: None,
            };
            self.outgoing.send_error(request_id, error).await;
            return;
        };

        let mapped_items: Vec<CoreInputItem> = items
            .into_iter()
            .map(|item| match item {
                WireInputItem::Text { text } => CoreInputItem::Text { text },
                WireInputItem::Image { image_url } => CoreInputItem::Image { image_url },
                WireInputItem::LocalImage { path } => CoreInputItem::LocalImage { path },
            })
            .collect();

        // Submit user input to the conversation.
        let _ = conversation
            .submit(Op::UserInput {
                items: mapped_items,
            })
            .await;

        // Acknowledge with an empty result.
        self.outgoing
            .send_response(request_id, SendUserMessageResponse {})
            .await;
    }

    async fn add_conversation_listener(
        &mut self,
        request_id: RequestId,
        params: AddConversationListenerParams,
    ) {
        let AddConversationListenerParams { conversation_id } = params;
        let Ok(conversation) = self
            .conversation_manager
            .get_conversation(conversation_id.0)
            .await
        else {
            let error = JSONRPCErrorError {
                code: INVALID_REQUEST_ERROR_CODE,
                message: format!("conversation not found: {}", conversation_id.0),
                data: None,
            };
            self.outgoing.send_error(request_id, error).await;
            return;
        };

        let subscription_id = Uuid::new_v4();
        let (cancel_tx, mut cancel_rx) = oneshot::channel();
        self.conversation_listeners
            .insert(subscription_id, cancel_tx);
        let outgoing_for_task = self.outgoing.clone();
        let add_listener_request_id = request_id.clone();
        tokio::spawn(async move {
            loop {
                tokio::select! {
                    _ = &mut cancel_rx => {
                        // User has unsubscribed, so exit this task.
                        break;
                    }
                    event = conversation.next_event() => {
                        let event = match event {
                            Ok(event) => event,
                            Err(err) => {
                                tracing::warn!("conversation.next_event() failed with: {err}");
                                break;
                            }
                        };

                        outgoing_for_task.send_event_as_notification(
                            &event,
                            Some(OutgoingNotificationMeta::new(Some(add_listener_request_id.clone()))),
                        )
                        .await;
                    }
                }
            }
        });
        let response = AddConversationSubscriptionResponse { subscription_id };
        self.outgoing.send_response(request_id, response).await;
    }

    async fn remove_conversation_listener(
        &mut self,
        request_id: RequestId,
        params: RemoveConversationListenerParams,
    ) {
        let RemoveConversationListenerParams { subscription_id } = params;
        match self.conversation_listeners.remove(&subscription_id) {
            Some(sender) => {
                // Signal the spawned task to exit and acknowledge.
                let _ = sender.send(());
                let response = RemoveConversationSubscriptionResponse {};
                self.outgoing.send_response(request_id, response).await;
            }
            None => {
                let error = JSONRPCErrorError {
                    code: INVALID_REQUEST_ERROR_CODE,
                    message: format!("subscription not found: {subscription_id}"),
                    data: None,
                };
                self.outgoing.send_error(request_id, error).await;
            }
        }
    }
}

fn derive_config_from_params(
    params: NewConversationParams,
    codex_linux_sandbox_exe: Option<PathBuf>,
) -> std::io::Result<Config> {
    let NewConversationParams {
        model,
        profile,
        cwd,
        approval_policy,
        sandbox,
        config: cli_overrides,
        base_instructions,
        include_plan_tool,
    } = params;
    let overrides = ConfigOverrides {
        model,
        config_profile: profile,
        cwd: cwd.map(PathBuf::from),
        approval_policy: approval_policy.map(Into::into),
        sandbox_mode: sandbox.map(Into::into),
        model_provider: None,
        codex_linux_sandbox_exe,
        base_instructions,
        include_plan_tool,
        disable_response_storage: None,
        show_raw_agent_reasoning: None,
    };

    let cli_overrides = cli_overrides
        .unwrap_or_default()
        .into_iter()
        .map(|(k, v)| (k, json_to_toml(v)))
        .collect();

    Config::load_with_cli_overrides(cli_overrides, overrides)
}