//! Scheduled message handler on `MessageService`.
//!
//! Provides:
//! - Client-facing CRUD: schedule, cancel, list pending scheduled messages
//! - Background dispatcher: periodically scans for due scheduled messages
//!   and sends them through the normal message path.

use std::sync::Arc;
use std::time::Duration;

use chrono::{DateTime, Utc};
use uuid::Uuid;

use crate::repo::CreateMessageInput;
use crate::socket::socket::Socket;
use crate::{ImksError, ImksResult};

use super::message::MessageService;

impl MessageService {
    // ── Client-facing scheduled message CRUD ──

    /// Handle `message:schedule` — schedule a message to be sent at a future time.
    pub async fn schedule_message(
        &self,
        socket: Arc<Socket>,
        data: &serde_json::Value,
    ) -> ImksResult<()> {
        let user_id = self.user_id(&socket)?;
        let payload = Self::first_payload(data)?;

        let channel_id: Uuid = Self::parse_field(payload, "channel_id")?;
        let body: String = Self::parse_field(payload, "body")?;
        let thread_id: Option<Uuid> = Self::parse_optional(payload, "thread_id")?;
        let reply_to_message_id: Option<Uuid> =
            Self::parse_optional(payload, "reply_to_message_id")?;
        let metadata: Option<serde_json::Value> = Self::parse_optional(payload, "metadata")?;
        let scheduled_at_str: String = Self::parse_field(payload, "scheduled_at")?;

        let scheduled_at: DateTime<Utc> = chrono::DateTime::parse_from_rfc3339(&scheduled_at_str)
            .map_err(|e| ImksError::InvalidInput(format!("Invalid scheduled_at: {e}")))?
            .into();

        let channel_id_str = channel_id.to_string();
        let user_id_str = user_id.to_string();

        self.validate_body_size(&body)?;
        self.ensure_readable(&channel_id_str, &user_id_str).await?;
        self.ensure_member(&channel_id_str, &user_id_str).await?;

        // Validate scheduled_at is in the future
        if scheduled_at <= Utc::now() {
            return Err(ImksError::InvalidInput(
                "scheduled_at must be in the future".into(),
            ));
        }

        let scheduled = self
            .repo
            .schedule_message(
                channel_id,
                user_id,
                thread_id,
                reply_to_message_id,
                &body,
                metadata,
                scheduled_at,
            )
            .await?;

        tracing::info!(
            scheduled_id = %scheduled.id,
            channel_id = %channel_id,
            user_id = %user_id,
            scheduled_at = %scheduled_at,
            "Message scheduled"
        );
        Ok(())
    }

    /// Handle `message:cancel_scheduled` — cancel a pending scheduled message.
    pub async fn cancel_scheduled(
        &self,
        socket: Arc<Socket>,
        data: &serde_json::Value,
    ) -> ImksResult<()> {
        let user_id = self.user_id(&socket)?;
        let payload = Self::first_payload(data)?;
        let scheduled_id: Uuid = Self::parse_field(payload, "scheduled_id")?;

        let cancelled = self.repo.cancel_scheduled(scheduled_id).await?;

        if !cancelled {
            return Err(ImksError::NotFound(format!(
                "scheduled message {scheduled_id} not found or already processed"
            )));
        }

        tracing::info!(%scheduled_id, %user_id, "Scheduled message cancelled");
        Ok(())
    }

    /// Handle `message:list_scheduled` — list pending scheduled messages for a channel.
    pub async fn list_scheduled(
        &self,
        socket: Arc<Socket>,
        data: &serde_json::Value,
    ) -> ImksResult<()> {
        let user_id = self.user_id(&socket)?;
        let payload = Self::first_payload(data)?;
        let channel_id: Uuid = Self::parse_field(payload, "channel_id")?;

        let channel_id_str = channel_id.to_string();
        let user_id_str = user_id.to_string();

        self.ensure_readable(&channel_id_str, &user_id_str).await?;

        let scheduled = self.repo.list_scheduled(channel_id, user_id).await?;

        let _ = socket.emit(
            "scheduled:loaded",
            serde_json::to_value(&scheduled).unwrap_or_default(),
        );
        Ok(())
    }

    // ── Background dispatcher ──

    /// Start the background scheduled-message dispatcher.
    /// Scans every 30 seconds for pending messages whose `scheduled_at` has passed.
    pub fn start_scheduled_dispatcher(self: std::sync::Arc<Self>) {
        tokio::spawn(async move {
            tracing::info!("Scheduled message dispatcher started (interval: 30s)");
            loop {
                tokio::time::sleep(Duration::from_secs(30)).await;

                match self.process_due_scheduled().await {
                    Ok(count) => {
                        if count > 0 {
                            tracing::info!(count, "Dispatched scheduled messages");
                        }
                    }
                    Err(e) => {
                        tracing::error!(error = %e, "Scheduled message dispatch failed");
                    }
                }
            }
        });
    }

    /// Fetch and dispatch all due scheduled messages.
    async fn process_due_scheduled(&self) -> crate::ImksResult<usize> {
        let due = self.repo.get_due_scheduled().await?;
        let mut dispatched = 0;

        for scheduled in due {
            let input = CreateMessageInput {
                channel_id: scheduled.channel_id,
                author_id: scheduled.author_id,
                thread_id: scheduled.thread_id,
                reply_to_message_id: scheduled.reply_to_message_id,
                message_type: "text".into(),
                body: scheduled.body.clone(),
                metadata: scheduled.metadata.clone(),
                system: false,
            };

            match self.repo.create(&input).await {
                Ok(message) => {
                    self.repo
                        .mark_scheduled_sent(scheduled.id, message.id)
                        .await?;

                    if let Some(ns) = self.namespaces.get_namespace("/") {
                        ns.emit_to_room(
                            &scheduled.channel_id.to_string(),
                            "message:new",
                            serde_json::to_value(&message).unwrap_or_default(),
                        )
                        .await;
                    }
                    dispatched += 1;
                }
                Err(e) => {
                    tracing::error!(scheduled_id = %scheduled.id, error = %e, "Failed to send scheduled message");
                    self.repo
                        .mark_scheduled_failed(scheduled.id, &e.to_string())
                        .await?;
                }
            }
        }

        Ok(dispatched)
    }
}