//! Push notifications (SPEC §14.6). M2a defined the trait; M4 owns `src/push/**` and implements it with the bounded
//! queue [`PushHub`] drained by the FCM [`Sender`] (started by `tasks::start`). [`NoopPushQueue`] remains for push
//! disabled (no credentials file).
//!
//! [`PushQueue::enqueue`] never blocks and never fails the caller: sending happens on a background task and never
//! delays an HTTP response (SPEC §14.6). Call it after the write transaction has committed.

use uuid::Uuid;

pub mod fcm;
pub mod queue;
pub mod sender;

pub use fcm::{Endpoints, FcmClient};
pub use queue::PushHub;
pub use sender::{RetryPolicy, Sender};

/// The notification types of SPEC §14.6 (exhaustive).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum PushType {
    ExpenseCreated,
    ExpenseUpdated,
    ExpenseDeleted,
    SettlementCreated,
    SettlementUpdated,
    SettlementDeleted,
    RecurringExpenseCreated,
    SyncBatch,
}

impl PushType {
    /// The `type` value of the data message.
    pub fn as_str(self) -> &'static str {
        match self {
            Self::ExpenseCreated => "expense_created",
            Self::ExpenseUpdated => "expense_updated",
            Self::ExpenseDeleted => "expense_deleted",
            Self::SettlementCreated => "settlement_created",
            Self::SettlementUpdated => "settlement_updated",
            Self::SettlementDeleted => "settlement_deleted",
            Self::RecurringExpenseCreated => "recurring_expense_created",
            Self::SyncBatch => "sync_batch",
        }
    }
}

/// One notification to send. Ids only, never personal content (SPEC §8.7).
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PushMessage {
    pub push_type: PushType,
    /// `None` for `sync_batch` (sent as `""` with `entity_type` `""`).
    pub entity_id: Option<Uuid>,
    /// The creator, editor, deleter, template creator or pusher.
    pub actor_user_id: Uuid,
    /// 1, or the number of notifiable changes for `sync_batch`.
    pub count: u32,
}

/// Queues notifications for the background sender, which resolves the target devices per SPEC §14.6.
pub trait PushQueue: Send + Sync + 'static {
    fn enqueue(&self, message: PushMessage);
}

/// Drops every message: push disabled (no FCM credentials).
#[derive(Debug, Clone, Copy, Default)]
pub struct NoopPushQueue;

impl PushQueue for NoopPushQueue {
    fn enqueue(&self, message: PushMessage) {
        tracing::debug!(
            push_type = message.push_type.as_str(),
            "push disabled, message dropped"
        );
    }
}