//! A model-authored roster for a mission — Slice 5.
//!
//! The Master Planner has been proposing teams (2-6 members, a model each) since
//! it shipped, and none of it reached a mission: the proposal lived in React
//! state. A mission's shape came instead from a team template — fixed roles, and
//! every claw minted `claude-sonnet-5`, which is why no mission has ever run
//! heterogeneous providers.
//!
//! This is the seam. A roster is `(topology_kind, [(role, backend)])`, which is
//! exactly what the composed executor consumes: `composed_graph` turns it into a
//! `TopologyGraph`, and `MicroVmTurnExecutor` reads `attrs["backend"]` per node,
//! so a `validator` role on a different provider's rootfs is a first-class graph
//! node rather than a bolt-on.
//!
//! # Why the backend is validated here and not at boot
//!
//! Placement already refuses a mission whose backend no online node can run —
//! but it refuses it at LAUNCH, after the roster was approved, the mission was
//! created and someone believed it was going to run. A model that invents
//! `rootfs-opus` is a normal thing for a model to do; discovering it three steps
//! later is not. So a roster naming a backend the fleet cannot run is rejected
//! when it is proposed, naming the backends that do exist.
//!
//! # What it deliberately does not do
//!
//! It does not mint claws. A composed mission's nodes are VMs, and provisioning
//! containers for them would create agents and `.brain` files nothing ever
//! dials — the same reason `on_launch` returns early for a microVM mission.

use serde::{Deserialize, Serialize};
use uuid::Uuid;

/// One member of a proposed roster.
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct RosterMember {
    /// The node's role, e.g. `implementer`, `verifier`. Becomes the graph node's
    /// role, which is what the per-node prompt is written around.
    pub role: String,
    /// Which rootfs image this node's VM boots (`missions.backend` per node).
    /// `None` inherits the mission's.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub backend: Option<String>,
    /// One line on why this member exists. Not consumed by anything — kept
    /// because a roster nobody can read is a roster nobody can refuse.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub rationale: Option<String>,
}

/// A proposed shape for a mission.
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct Roster {
    /// A `cm_topology::TopologyKind` name — `pipeline`, `hub_spoke`, …
    pub topology_kind: String,
    pub members: Vec<RosterMember>,
}

/// Ceiling on a proposed roster.
///
/// Each member is a whole VM: a boot, an inject, an agent session and a collect.
/// Anthropic's own guidance tops out at 3-5 subagents, and every member here
/// costs far more than a subagent does. A model asked to size a team will
/// cheerfully propose twelve.
pub const MAX_MEMBERS: usize = 6;

/// Why a roster was refused.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Refusal {
    Empty,
    TooMany(usize),
    BlankRole(usize),
    /// A backend no online node can run, with the ones that exist.
    UnknownBackend { backend: String, available: Vec<String> },
    UnknownTopology(String),
}

impl std::fmt::Display for Refusal {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Refusal::Empty => write!(f, "the roster has no members, so there is nothing to run"),
            Refusal::TooMany(n) => write!(
                f,
                "the roster has {n} members and the ceiling is {MAX_MEMBERS} — each one is a whole \
                 VM, not a subagent"
            ),
            Refusal::BlankRole(i) => write!(f, "member {i} has no role"),
            Refusal::UnknownBackend { backend, available } => write!(
                f,
                "no online node can run backend {backend:?}; the fleet has: {}",
                if available.is_empty() {
                    "(none — no node reports a microvm rootfs)".to_string()
                } else {
                    available.join(", ")
                }
            ),
            Refusal::UnknownTopology(k) => write!(
                f,
                "{k:?} is not a topology kind this platform can plan; use one of: {}",
                cm_topology::TopologyKind::ALL
                    .iter()
                    .map(|k| k.as_str())
                    .collect::<Vec<_>>()
                    .join(", ")
            ),
        }
    }
}

impl Roster {
    /// Check a roster against the platform and the fleet.
    ///
    /// `available` is the set of backends at least one ONLINE node can boot.
    /// Fail-closed on every axis: an unrecognised topology, a blank role and an
    /// unbuildable backend are all refusals, because each of them becomes a
    /// failure much later and much more expensively.
    pub fn validate(&self, available: &[String]) -> Result<(), Refusal> {
        if self.members.is_empty() {
            return Err(Refusal::Empty);
        }
        if self.members.len() > MAX_MEMBERS {
            return Err(Refusal::TooMany(self.members.len()));
        }
        if parse_kind(&self.topology_kind).is_none() {
            return Err(Refusal::UnknownTopology(self.topology_kind.clone()));
        }
        for (i, m) in self.members.iter().enumerate() {
            if m.role.trim().is_empty() {
                return Err(Refusal::BlankRole(i));
            }
            if let Some(b) = m.backend.as_deref().map(str::trim).filter(|b| !b.is_empty()) {
                if !available.iter().any(|a| a == b) {
                    return Err(Refusal::UnknownBackend {
                        backend: b.to_string(),
                        available: available.to_vec(),
                    });
                }
            }
        }
        Ok(())
    }

    /// The graph a composed run executes.
    ///
    /// Node ids follow `cm_topology::build`'s `n0..` convention so the graph is
    /// indistinguishable from a template-built one — the executor, the planners
    /// and the checkpoint all treat it the same. The per-member backend rides in
    /// `attrs`, which is the channel `MicroVmTurnExecutor` already reads.
    pub fn graph(&self) -> Result<serde_json::Value, String> {
        let kind = parse_kind(&self.topology_kind)
            .ok_or_else(|| format!("unknown topology kind {:?}", self.topology_kind))?;
        let roles: Vec<&str> = self.members.iter().map(|m| m.role.trim()).collect();
        let mut graph =
            cm_topology::build(kind, &roles).map_err(|e| format!("build topology: {e}"))?;
        for (node, member) in graph.nodes.iter_mut().zip(self.members.iter()) {
            if let Some(b) = member
                .backend
                .as_deref()
                .map(str::trim)
                .filter(|b| !b.is_empty())
            {
                node.attrs.insert("backend".to_string(), b.to_string());
            }
        }
        serde_json::to_value(&graph).map_err(|e| format!("serialize graph: {e}"))
    }
}

/// Topology kind by name, accepting exactly what the catalog declares.
///
/// Deliberately not `unwrap_or(HubSpoke)`. `mission_orchestrator::
/// parse_topology_kind` does default, which is right for a stored template
/// written by us and wrong for a string a model just invented: silently running
/// a `pipeline` proposal as a hub-and-spoke would change what every node sees
/// and nothing would say so.
fn parse_kind(s: &str) -> Option<cm_topology::TopologyKind> {
    let want = s.trim();
    cm_topology::TopologyKind::ALL
        .iter()
        .copied()
        .find(|k| k.as_str().eq_ignore_ascii_case(want))
}

/// Backends at least one online node can actually boot.
///
/// Read from the nodes' reported `rootfs` capability, so it answers "what can
/// run today" rather than "what images did someone build once".
pub async fn available_backends(
    pool: &sqlx::PgPool,
    workspace_id: Uuid,
) -> Result<Vec<String>, String> {
    let rows: Vec<(serde_json::Value,)> = sqlx::query_as(
        "SELECT capabilities -> 'rootfs'
           FROM nodes
          WHERE workspace_id = $1 AND status = 'online'
            AND capabilities @> '{\"microvm\": true}'::jsonb",
    )
    .bind(workspace_id)
    .fetch_all(pool)
    .await
    .map_err(|e| format!("read node rootfs capabilities: {e}"))?;

    let mut out: Vec<String> = rows
        .into_iter()
        .filter_map(|(v,)| v.as_array().cloned())
        .flatten()
        .filter_map(|v| v.as_str().map(str::to_string))
        // A node reports every rootfs it has BUILT, which is not the same as
        // every rootfs a mission can run in. `agent-terminal` is on tank right
        // now: bootable, and with no credential contract, so an agent inside it
        // has nothing to authenticate with. Offering it to the planner would
        // produce a roster that validates, approves, launches, and then fails at
        // the agent turn — the expensive kind of late.
        .filter(|b| crate::mission_runtime::backend_can_run_a_mission(b))
        .collect();
    out.sort();
    out.dedup();
    Ok(out)
}

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

    fn member(role: &str, backend: Option<&str>) -> RosterMember {
        RosterMember {
            role: role.into(),
            backend: backend.map(str::to_string),
            rationale: None,
        }
    }

    fn roster(kind: &str, members: Vec<RosterMember>) -> Roster {
        Roster {
            topology_kind: kind.into(),
            members,
        }
    }

    /// A backend the fleet cannot boot must be refused where it is PROPOSED.
    /// Placement would refuse it too — at launch, after the roster was approved
    /// and someone believed the mission was going to run.
    #[test]
    fn a_backend_no_node_can_run_is_refused_with_the_ones_that_exist() {
        let have = vec!["claude".to_string(), "kimi".to_string()];
        let r = roster(
            "pipeline",
            vec![member("implementer", Some("claude")), member("verifier", Some("rootfs-opus"))],
        );
        let err = r.validate(&have).unwrap_err();
        assert_eq!(
            err,
            Refusal::UnknownBackend {
                backend: "rootfs-opus".into(),
                available: have.clone()
            }
        );
        // The message must name what IS available, or the operator's next move
        // is a guess.
        let msg = err.to_string();
        assert!(msg.contains("claude") && msg.contains("kimi"), "{msg}");

        // And the same roster passes once every backend is one the fleet has.
        let ok = roster(
            "pipeline",
            vec![member("implementer", Some("claude")), member("verifier", Some("kimi"))],
        );
        assert!(ok.validate(&have).is_ok());
    }

    /// A member with no backend inherits the mission's, which is legitimate —
    /// the whole roster does not have to be heterogeneous to be useful.
    #[test]
    fn a_member_without_a_backend_is_not_a_refusal() {
        let r = roster("pipeline", vec![member("implementer", None)]);
        assert!(r.validate(&["claude".to_string()]).is_ok());
        // Blank counts as absent, not as a backend named "".
        let r = roster("pipeline", vec![member("implementer", Some("   "))]);
        assert!(r.validate(&["claude".to_string()]).is_ok());
    }

    /// A bootable image is not necessarily a runnable one. tank reports
    /// `agent-terminal` in its rootfs list today: a real image, with no
    /// credential contract, so an agent booted into it has nothing to
    /// authenticate with. Offering it to the planner would produce a roster that
    /// validates, approves, launches and then fails at the agent turn.
    #[test]
    fn only_backends_that_can_authenticate_are_offered() {
        assert!(crate::mission_runtime::backend_can_run_a_mission("claude"));
        assert!(crate::mission_runtime::backend_can_run_a_mission("default"));
        for unrunnable in ["agent-terminal", "agent-browser", "rootfs-opus"] {
            assert!(
                !crate::mission_runtime::backend_can_run_a_mission(unrunnable),
                "{unrunnable} has no credential contract and must not be proposable"
            );
        }
    }

    /// The ceiling. Each member is a VM boot, an inject, a full agent session
    /// and a collect — a model asked to size a team proposes twelve happily.
    #[test]
    fn a_roster_is_bounded_and_non_empty() {
        let have = vec!["claude".to_string()];
        assert_eq!(roster("pipeline", vec![]).validate(&have), Err(Refusal::Empty));

        let many: Vec<_> = (0..MAX_MEMBERS + 1)
            .map(|i| member(&format!("r{i}"), None))
            .collect();
        assert_eq!(
            roster("pipeline", many).validate(&have),
            Err(Refusal::TooMany(MAX_MEMBERS + 1))
        );

        let exactly: Vec<_> = (0..MAX_MEMBERS).map(|i| member(&format!("r{i}"), None)).collect();
        assert!(roster("pipeline", exactly).validate(&have).is_ok());
    }

    /// An invented topology kind must be refused, NOT defaulted. Running a
    /// `pipeline` proposal as a hub-and-spoke changes what every node sees and
    /// nothing would say so — the same silent-substitution shape as a backend
    /// that quietly falls back to the default image.
    #[test]
    fn an_invented_topology_kind_is_refused_rather_than_defaulted() {
        let have = vec!["claude".to_string()];
        let r = roster("assembly_line", vec![member("implementer", None)]);
        assert_eq!(
            r.validate(&have),
            Err(Refusal::UnknownTopology("assembly_line".into()))
        );
        // Every kind the catalog declares is accepted, so this cannot drift out
        // of sync with what the orchestrator can actually plan.
        for kind in cm_topology::TopologyKind::ALL {
            let r = roster(kind.as_str(), vec![member("implementer", None)]);
            assert!(r.validate(&have).is_ok(), "{}", kind.as_str());
        }
    }

    /// The graph is the handoff to the composed executor: node ids in
    /// `cm_topology`'s own convention, and the backend in the `attrs` channel
    /// `MicroVmTurnExecutor` reads. If this drifts, a heterogeneous roster runs
    /// every node on the mission default and looks fine.
    #[test]
    fn the_graph_carries_each_members_backend_where_the_executor_reads_it() {
        let r = roster(
            "pipeline",
            vec![
                member("implementer", Some("claude")),
                member("verifier", Some("kimi")),
                member("scribe", None),
            ],
        );
        let g = r.graph().expect("a runnable graph");
        let nodes = g["nodes"].as_array().expect("nodes");
        assert_eq!(nodes.len(), 3);
        assert_eq!(nodes[0]["role"], "implementer");
        assert_eq!(nodes[0]["attrs"]["backend"], "claude");
        assert_eq!(nodes[1]["attrs"]["backend"], "kimi");
        assert!(
            nodes[2]["attrs"].get("backend").is_none(),
            "a member with no backend must inherit the mission's, not be stamped with one"
        );

        // And it deserializes as the real thing the worker will parse — a graph
        // that only looks right as JSON fails at claim time with "missing or
        // invalid graph", which reads as a runtime fault rather than a bad
        // roster.
        let parsed: cm_topology::TopologyGraph =
            serde_json::from_value(g).expect("the worker must be able to parse it");
        assert_eq!(parsed.nodes.len(), 3);
        assert_eq!(
            parsed.nodes[1].attrs.get("backend").map(String::as_str),
            Some("kimi")
        );
    }
}