//! Unified dashboard event channel — all near-real-time browser events
//! flow through `Coordinator.dashboard_events`. Each event carries a
//! monotonic `seq` for client-side dedupe against `/api/state` snapshots.
//! Design rationale (single channel, broker forwarder isolation):
//! `docs/web-ui/shape.md::One unified channel`.

use serde::Serialize;

use crate::container_view::ContainerView;
use crate::dashboard::{MetaInputView, TombstoneView};
use crate::rebuild_queue::QueueEntry;

#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "snake_case", tag = "kind")]
pub enum DashboardEvent {
    /// Broker `Sent` event mirrored onto the dashboard channel.
    /// `file_refs` carries every path-shaped token in `body` that
    /// hive-c0re verified is a regular file under the allow-listed
    /// roots (per-agent `state/` + `shared/`). The forwarder
    /// pre-validates so the dashboard doesn't need a probe
    /// endpoint — the client renders anchors only for tokens that
    /// appear in this list, everything else stays plain text.
    Sent {
        seq: u64,
        /// Broker row id. Allows the dashboard to track reply threads.
        id: i64,
        from: String,
        to: String,
        body: String,
        at: i64,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        in_reply_to: Option<i64>,
        #[serde(default, skip_serializing_if = "Vec::is_empty")]
        file_refs: Vec<String>,
    },
    /// Broker `Delivered` event mirrored onto the dashboard channel.
    /// `file_refs` is the same shape as `Sent`.
    Delivered {
        seq: u64,
        /// Broker row id. Allows the dashboard to track reply threads.
        id: i64,
        from: String,
        to: String,
        body: String,
        at: i64,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        in_reply_to: Option<i64>,
        #[serde(default, skip_serializing_if = "Vec::is_empty")]
        file_refs: Vec<String>,
    },
    /// A new approval landed in the pending queue. Payload carries
    /// enough to render the dashboard row without a `/api/state`
    /// refetch (`diff` is the raw unified diff text, same shape the
    /// snapshot ships).
    ///
    /// The approval's own kind (`"apply_commit"` / `"spawn"`) lives on
    /// `approval_kind` rather than `kind` because the latter is taken
    /// by the serde tag identifying which `DashboardEvent` variant
    /// this is.
    ApprovalAdded {
        seq: u64,
        id: i64,
        agent: String,
        approval_kind: &'static str,
        sha_short: Option<String>,
        diff: Option<String>,
        description: Option<String>,
    },
    /// A pending approval transitioned to a terminal state
    /// (approved / denied / failed). Clients move the row out of the
    /// pending list and into history.
    ApprovalResolved {
        seq: u64,
        id: i64,
        agent: String,
        approval_kind: &'static str,
        sha_short: Option<String>,
        /// `"approved"` / `"denied"` / `"failed"`.
        status: &'static str,
        resolved_at: i64,
        note: Option<String>,
        description: Option<String>,
    },
    /// A question landed in the queue. `target = None` means
    /// operator-targeted (`Ask { to: None | Some("operator") }`);
    /// `target = Some(<agent>)` means a peer-to-peer question. Both
    /// are surfaced on the dashboard so the operator can monitor /
    /// override-answer stuck threads.
    QuestionAdded {
        seq: u64,
        id: i64,
        asker: String,
        question: String,
        options: Vec<String>,
        multi: bool,
        asked_at: i64,
        deadline_at: Option<i64>,
        target: Option<String>,
        /// Verified file-path tokens that appear in `question`.
        /// Same shape as broker `Sent`/`Delivered` events; the
        /// client linkifies only what hive-c0re vouched for.
        #[serde(default, skip_serializing_if = "Vec::is_empty")]
        question_refs: Vec<String>,
    },
    /// A question was answered (operator answer, peer answer,
    /// operator override on a peer thread, or ttl watchdog
    /// `[expired]`). Clients move the row from pending to history.
    /// `cancelled = true` when the operator dismissed via the cancel
    /// button.
    QuestionResolved {
        seq: u64,
        id: i64,
        answer: String,
        answerer: String,
        answered_at: i64,
        cancelled: bool,
        target: Option<String>,
        /// Verified file-path tokens that appear in `answer`.
        #[serde(default, skip_serializing_if = "Vec::is_empty")]
        answer_refs: Vec<String>,
    },
    /// A lifecycle action started for an agent (spawn / start / stop
    /// / restart / rebuild / destroy). Clients render a spinner next
    /// to the row; the client computes "seconds in this state"
    /// locally from `since_unix` so a slow rebuild's elapsed time
    /// ticks without polling.
    TransientSet {
        seq: u64,
        name: String,
        /// Lifecycle kind: `"spawning"` / `"starting"` / `"stopping"` /
        /// `"restarting"` / `"rebuilding"` / `"destroying"`.
        transient_kind: &'static str,
        since_unix: i64,
    },
    /// The matching lifecycle action resolved (success or failure).
    /// Clients drop the spinner row.
    TransientCleared { seq: u64, name: String },
    /// One container row changed — new container appeared (post-spawn
    /// finalise), an existing one flipped `running` / `needs_update` /
    /// `sha`, etc. Clients upsert by `container.name`. Payload carries
    /// the full row so cold-loaded clients and event-driven clients
    /// converge on the same render.
    ///
    /// Fired by `Coordinator::rescan_containers_and_emit`, which diffs
    /// a fresh `nixos-container list`–derived snapshot against the
    /// last one cached on the coordinator. Mutation sites (lifecycle
    /// endpoints, `actions::destroy` / approve, `crash_watch`'s poll loop)
    /// call the rescan after their work lands.
    ContainerStateChanged { seq: u64, container: ContainerView },
    /// A container that was in the previous snapshot is gone. Clients
    /// drop the row by name. Fired alongside any
    /// `nixos-container destroy` (operator-driven or otherwise) on the
    /// next rescan.
    ContainerRemoved { seq: u64, name: String },
    /// Full snapshot of the tombstones list. Emitted on every
    /// mutation that could add / remove a tombstone: destroy
    /// (with or without purge), purge-tombstone, spawn approval
    /// (which can consume a tombstone of the same name). Snapshot
    /// shape (not diff) because the list is tiny (single-digit
    /// typical) and recomputing avoids the add/remove races a
    /// per-row event would have.
    TombstonesChanged {
        seq: u64,
        tombstones: Vec<TombstoneView>,
    },
    /// Full snapshot of `meta/flake.lock`'s root inputs. Emitted
    /// after every operation that bumps a lock: `meta-update`,
    /// `rebuild_agent` (lock bumps via two-phase staging),
    /// `update-all`. Same snapshot-shape rationale as
    /// `TombstonesChanged` — the list is small (one row per agent
    /// plus their fetched inputs).
    MetaInputsChanged {
        seq: u64,
        inputs: Vec<MetaInputView>,
    },
    /// A dashboard-triggered `meta-update` started (`running: true`) or
    /// finished (`running: false`). `post_meta_update` returns 200
    /// immediately and runs the `nix flake update` + agent-rebuild
    /// ripple in a background task — this event lets the META INPUTS
    /// panel show a disabled "updating…" state for that whole window
    /// instead of looking idle. Emitted by
    /// `Coordinator::meta_update_guard` / `MetaUpdateGuard::drop` only
    /// when the active-run count crosses 0, so concurrent updates flip
    /// the flag exactly once.
    MetaUpdateRunning { seq: u64, running: bool },
    /// Full snapshot of the rebuild queue (`hive-c0re::rebuild_queue`)
    /// — every entry, in enqueue order, including the few most-recent
    /// terminal entries the queue retains for history. Same
    /// snapshot-shape rationale as `TombstonesChanged` /
    /// `MetaInputsChanged`: the list is small, snapshot semantics avoid
    /// the add/remove races a per-row event would have, and the
    /// dashboard's grouping (`parent_id`) is most naturally re-derived
    /// from the full list.
    RebuildQueueChanged { seq: u64, queue: Vec<QueueEntry> },
}

impl DashboardEvent {
    /// Snake-case identifier matching this variant's serde `tag`
    /// (e.g. `Sent` → `"sent"`, `ContainerStateChanged` →
    /// `"container_state_changed"`). Lets `/dashboard/stream`'s
    /// `?kinds=` filter decide whether to forward a frame without
    /// paying the JSON-serialise cost first.
    ///
    /// Keep in sync with `#[serde(rename_all = "snake_case", tag =
    /// "kind")]` on `DashboardEvent` — if a new variant lands above,
    /// add it here too. `cargo test` covers this via the
    /// `kind_tag_matches_serde_kind_field` round-trip test.
    #[must_use]
    pub fn kind_tag(&self) -> &'static str {
        match self {
            DashboardEvent::Sent { .. } => "sent",
            DashboardEvent::Delivered { .. } => "delivered",
            DashboardEvent::ApprovalAdded { .. } => "approval_added",
            DashboardEvent::ApprovalResolved { .. } => "approval_resolved",
            DashboardEvent::QuestionAdded { .. } => "question_added",
            DashboardEvent::QuestionResolved { .. } => "question_resolved",
            DashboardEvent::TransientSet { .. } => "transient_set",
            DashboardEvent::TransientCleared { .. } => "transient_cleared",
            DashboardEvent::ContainerStateChanged { .. } => "container_state_changed",
            DashboardEvent::ContainerRemoved { .. } => "container_removed",
            DashboardEvent::TombstonesChanged { .. } => "tombstones_changed",
            DashboardEvent::MetaInputsChanged { .. } => "meta_inputs_changed",
            DashboardEvent::MetaUpdateRunning { .. } => "meta_update_running",
            DashboardEvent::RebuildQueueChanged { .. } => "rebuild_queue_changed",
        }
    }
}

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

    /// Round-trip representative variants through serde and confirm
    /// the `kind` JSON field matches `kind_tag()`. The exhaustive
    /// `match` in `kind_tag` already provides compile-time variant
    /// coverage — this test is the value-side guard against
    /// typos in the `snake_case` strings vs serde's `rename_all`
    /// output. `ContainerStateChanged` is omitted from the sample
    /// list only because `ContainerView` has no `Default` impl and
    /// constructing one inline here is more boilerplate than the
    /// test is worth; the variant is still covered by the
    /// `kind_tag` match arm.
    #[test]
    #[allow(
        clippy::too_many_lines,
        reason = "exhaustive coverage of every DashboardEvent variant — the \
                  length is the point"
    )]
    fn kind_tag_matches_serde_kind_field() {
        let samples: Vec<DashboardEvent> = vec![
            DashboardEvent::Sent {
                seq: 1,
                id: 1,
                from: "a".into(),
                to: "b".into(),
                body: String::new(),
                at: 0,
                in_reply_to: None,
                file_refs: Vec::new(),
            },
            DashboardEvent::Delivered {
                seq: 1,
                id: 1,
                from: "a".into(),
                to: "b".into(),
                body: String::new(),
                at: 0,
                in_reply_to: None,
                file_refs: Vec::new(),
            },
            DashboardEvent::ApprovalAdded {
                seq: 1,
                id: 1,
                agent: "x".into(),
                approval_kind: "apply_commit",
                sha_short: None,
                diff: None,
                description: None,
            },
            DashboardEvent::ApprovalResolved {
                seq: 1,
                id: 1,
                agent: "x".into(),
                approval_kind: "apply_commit",
                sha_short: None,
                status: "approved",
                resolved_at: 0,
                note: None,
                description: None,
            },
            DashboardEvent::QuestionAdded {
                seq: 1,
                id: 1,
                asker: "a".into(),
                question: String::new(),
                options: Vec::new(),
                multi: false,
                asked_at: 0,
                deadline_at: None,
                target: None,
                question_refs: Vec::new(),
            },
            DashboardEvent::QuestionResolved {
                seq: 1,
                id: 1,
                answer: String::new(),
                answerer: "a".into(),
                answered_at: 0,
                cancelled: false,
                target: None,
                answer_refs: Vec::new(),
            },
            DashboardEvent::TransientSet {
                seq: 1,
                name: "x".into(),
                transient_kind: "rebuilding",
                since_unix: 0,
            },
            DashboardEvent::TransientCleared {
                seq: 1,
                name: "x".into(),
            },
            DashboardEvent::ContainerRemoved {
                seq: 1,
                name: "x".into(),
            },
            DashboardEvent::TombstonesChanged {
                seq: 1,
                tombstones: Vec::new(),
            },
            DashboardEvent::MetaInputsChanged {
                seq: 1,
                inputs: Vec::new(),
            },
            DashboardEvent::MetaUpdateRunning {
                seq: 1,
                running: false,
            },
            DashboardEvent::RebuildQueueChanged {
                seq: 1,
                queue: Vec::new(),
            },
        ];
        for ev in samples {
            let v: serde_json::Value = serde_json::to_value(&ev).expect("serialise");
            let serde_kind = v
                .get("kind")
                .and_then(|k| k.as_str())
                .expect("kind field present");
            assert_eq!(ev.kind_tag(), serde_kind, "kind_tag() drift on {ev:?}",);
        }
    }
}