converge-ferrox-solver 0.5.0

use async_trait::async_trait;
use converge_pack::{AgentEffect, Context, ContextKey, ProposedFact, Suggestor};
use std::time::Instant;
use tracing::warn;

use super::problem::{SchedulingPlan, SchedulingRequest, TaskAssignment};

pub(super) const REQUEST_PREFIX: &str = "scheduling-request:";
const PLAN_PREFIX: &str = "scheduling-plan-greedy:";

/// Schedules tasks via Earliest-Deadline-First + earliest-available skilled agent.
///
/// **Algorithm:** O(n·m·log n) where n = tasks, m = agents.
///
/// **When to use:** latency-sensitive pipelines where a good schedule is needed
/// in microseconds. Use alongside [`CpSatSchedulerSuggestor`] in a Formation;
/// the Engine will emit both plans and the highest-confidence one (CP-SAT optimal)
/// will be accepted for execution.
///
/// **Confidence:** capped at 0.65 — greedy cannot prove optimality.
///
/// [`CpSatSchedulerSuggestor`]: super::cpsat::CpSatSchedulerSuggestor
pub struct GreedySchedulerSuggestor;

#[async_trait]
impl Suggestor for GreedySchedulerSuggestor {
    fn name(&self) -> &'static str {
        "GreedySchedulerSuggestor"
    }

    fn dependencies(&self) -> &[ContextKey] {
        &[ContextKey::Seeds]
    }

    fn complexity_hint(&self) -> Option<&'static str> {
        Some("O(n·m·log n) — EDF + earliest-available; deterministic, sub-ms for n ≤ 10 000 tasks")
    }

    fn accepts(&self, ctx: &dyn Context) -> bool {
        ctx.get(ContextKey::Seeds).iter().any(|f| {
            f.id().starts_with(REQUEST_PREFIX) && !own_plan_exists(ctx, request_id(f.id()))
        })
    }

    async fn execute(&self, ctx: &dyn Context) -> AgentEffect {
        let mut proposals = Vec::new();

        for fact in ctx
            .get(ContextKey::Seeds)
            .iter()
            .filter(|f| f.id().starts_with(REQUEST_PREFIX))
        {
            let rid = request_id(fact.id());
            if own_plan_exists(ctx, rid) {
                continue;
            }

            match serde_json::from_str::<SchedulingRequest>(fact.content()) {
                Ok(req) => {
                    let plan = solve_greedy(&req);
                    // Greedy is fast but can't prove optimality — cap confidence at 0.65.
                    let confidence = (plan.throughput_ratio() * 0.65).min(0.65);
                    proposals.push(
                        ProposedFact::new(
                            ContextKey::Strategies,
                            format!("{PLAN_PREFIX}{rid}"),
                            serde_json::to_string(&plan).unwrap_or_default(),
                            self.name(),
                        )
                        .with_confidence(confidence),
                    );
                }
                Err(e) => {
                    warn!(id = %fact.id(), error = %e, "malformed scheduling-request");
                }
            }
        }

        if proposals.is_empty() {
            AgentEffect::empty()
        } else {
            AgentEffect::with_proposals(proposals)
        }
    }
}

fn request_id(fact_id: &str) -> &str {
    fact_id.trim_start_matches(REQUEST_PREFIX)
}

fn own_plan_exists(ctx: &dyn Context, request_id: &str) -> bool {
    let plan_id = format!("{PLAN_PREFIX}{request_id}");
    ctx.get(ContextKey::Strategies)
        .iter()
        .any(|f| f.id() == plan_id.as_str())
}

/// Pure EDF + earliest-available scheduling.  No OR-Tools dependency.
pub fn solve_greedy(req: &SchedulingRequest) -> SchedulingPlan {
    let t0 = Instant::now();

    // Sort tasks by earliest deadline first.
    let mut ordered: Vec<_> = req.tasks.iter().collect();
    ordered.sort_by_key(|t| t.deadline_min);

    let mut next_free = vec![0i64; req.agents.len()];
    let mut assignments: Vec<TaskAssignment> = Vec::new();

    for task in &ordered {
        // Find capable agent whose earliest available time after release is smallest.
        let best = req
            .agents
            .iter()
            .filter(|a| a.capabilities.contains(&task.required_capability))
            .min_by_key(|a| next_free[a.id].max(task.release_min));

        if let Some(agent) = best {
            let start = next_free[agent.id].max(task.release_min);
            let end = start + task.duration_min;
            if end <= task.deadline_min {
                next_free[agent.id] = end;
                assignments.push(TaskAssignment {
                    task_id: task.id,
                    task_name: task.name.clone(),
                    agent_id: agent.id,
                    agent_name: agent.name.clone(),
                    start_min: start,
                    end_min: end,
                });
            }
        }
    }

    assignments.sort_by_key(|a| a.start_min);
    let makespan = assignments.iter().map(|a| a.end_min).max().unwrap_or(0);
    let scheduled = assignments.len();

    SchedulingPlan {
        request_id: req.id.clone(),
        assignments,
        tasks_total: req.tasks.len(),
        tasks_scheduled: scheduled,
        makespan_min: makespan,
        solver: "greedy-edf".to_string(),
        status: "feasible".to_string(),
        wall_time_seconds: t0.elapsed().as_secs_f64(),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::scheduling::problem::{SchedulingAgent, SchedulingTask};
    use crate::test_support::MockContext;
    use converge_pack::Suggestor;

    fn agent(id: usize, name: &str, caps: &[&str]) -> SchedulingAgent {
        SchedulingAgent {
            id,
            name: name.into(),
            capabilities: caps.iter().map(|s| (*s).into()).collect(),
        }
    }

    fn task(
        id: usize,
        name: &str,
        cap: &str,
        duration: i64,
        release: i64,
        deadline: i64,
    ) -> SchedulingTask {
        SchedulingTask {
            id,
            name: name.into(),
            required_capability: cap.into(),
            duration_min: duration,
            release_min: release,
            deadline_min: deadline,
        }
    }

    fn req_with(tasks: Vec<SchedulingTask>, agents: Vec<SchedulingAgent>) -> SchedulingRequest {
        SchedulingRequest {
            id: "r1".into(),
            agents,
            tasks,
            horizon_min: 480,
            time_limit_seconds: 1.0,
        }
    }

    #[test]
    fn empty_request_yields_empty_plan() {
        let req = req_with(vec![], vec![]);
        let plan = solve_greedy(&req);
        assert_eq!(plan.tasks_total, 0);
        assert_eq!(plan.tasks_scheduled, 0);
        assert_eq!(plan.makespan_min, 0);
        assert!((plan.throughput_ratio() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn single_capable_agent_schedules_in_order() {
        let req = req_with(
            vec![
                task(1, "t1", "py", 30, 0, 60),
                task(2, "t2", "py", 30, 0, 120),
            ],
            vec![agent(0, "alice", &["py"])],
        );
        let plan = solve_greedy(&req);
        assert_eq!(plan.tasks_scheduled, 2);
        assert_eq!(plan.makespan_min, 60);
        assert_eq!(plan.assignments[0].task_id, 1);
        assert!((plan.throughput_ratio() - 1.0).abs() < f64::EPSILON);
    }

    #[test]
    fn drops_task_with_unsatisfiable_deadline() {
        let req = req_with(
            vec![task(1, "tight", "py", 100, 0, 30)],
            vec![agent(0, "alice", &["py"])],
        );
        let plan = solve_greedy(&req);
        assert_eq!(plan.tasks_scheduled, 0);
        assert_eq!(plan.tasks_total, 1);
    }

    #[test]
    fn skips_task_when_no_capable_agent() {
        let req = req_with(
            vec![task(1, "rs-only", "rust", 30, 0, 120)],
            vec![agent(0, "alice", &["py"])],
        );
        let plan = solve_greedy(&req);
        assert_eq!(plan.tasks_scheduled, 0);
    }

    #[test]
    fn picks_earliest_available_agent() {
        let req = req_with(
            vec![
                task(1, "t1", "py", 60, 0, 120),
                task(2, "t2", "py", 30, 0, 120),
            ],
            vec![agent(0, "alice", &["py"]), agent(1, "bob", &["py"])],
        );
        let plan = solve_greedy(&req);
        assert_eq!(plan.tasks_scheduled, 2);
        let agents: std::collections::HashSet<_> =
            plan.assignments.iter().map(|a| a.agent_id).collect();
        assert_eq!(agents.len(), 2, "should distribute across both agents");
    }

    #[test]
    fn release_time_delays_start() {
        let req = req_with(
            vec![task(1, "t1", "py", 30, 100, 200)],
            vec![agent(0, "alice", &["py"])],
        );
        let plan = solve_greedy(&req);
        assert_eq!(plan.assignments[0].start_min, 100);
        assert_eq!(plan.assignments[0].end_min, 130);
    }

    #[tokio::test]
    async fn suggestor_emits_proposal_for_seed() {
        let req = req_with(
            vec![task(1, "t1", "py", 30, 0, 60)],
            vec![agent(0, "alice", &["py"])],
        );
        let body = serde_json::to_string(&req).unwrap();
        let ctx = MockContext::empty().with_seed(&format!("{REQUEST_PREFIX}r1"), &body);
        let s = GreedySchedulerSuggestor;
        assert_eq!(s.name(), "GreedySchedulerSuggestor");
        assert_eq!(s.dependencies(), &[ContextKey::Seeds]);
        assert!(s.complexity_hint().is_some());
        assert!(s.accepts(&ctx));
        let effect = s.execute(&ctx).await;
        assert_eq!(effect.proposals().len(), 1);
    }

    #[tokio::test]
    async fn suggestor_skips_if_plan_already_present() {
        let req = req_with(
            vec![task(1, "t1", "py", 30, 0, 60)],
            vec![agent(0, "alice", &["py"])],
        );
        let body = serde_json::to_string(&req).unwrap();
        let ctx = MockContext::empty()
            .with_seed(&format!("{REQUEST_PREFIX}r1"), &body)
            .with_strategy("scheduling-plan-greedy:r1", "{}");
        let s = GreedySchedulerSuggestor;
        assert!(!s.accepts(&ctx));
        let effect = s.execute(&ctx).await;
        assert_eq!(effect.proposals().len(), 0);
    }

    #[tokio::test]
    async fn suggestor_handles_malformed_seed() {
        let ctx = MockContext::empty().with_seed(&format!("{REQUEST_PREFIX}bad"), "not json");
        let s = GreedySchedulerSuggestor;
        let effect = s.execute(&ctx).await;
        assert_eq!(effect.proposals().len(), 0);
    }

    #[tokio::test]
    async fn suggestor_ignores_other_seed_prefixes() {
        let ctx = MockContext::empty().with_seed("unrelated:r1", "{}");
        let s = GreedySchedulerSuggestor;
        assert!(!s.accepts(&ctx));
    }
}