srcgraph-metrics 0.1.0

//! Petri-net reconstruction from per-class `callSequences` blobs, with token-replay
//! conformance scoring.
//!
//! For every node whose blob holds **≥2** call sequences we run an
//! alpha-miner-style pass:
//!
//! 1. Collect activities (every distinct call), direct-succession pair counts,
//!    plus first/last-activity multisets.
//! 2. Classify each ordered pair `(a, b)` as **causal** (succession seen one
//!    way only) or **parallel** (seen both ways).
//! 3. Build the Petri net:
//!    - one transition `t_<act>` per activity
//!    - start place `p_start` → every first-activity transition
//!    - every last-activity transition → end place `p_end`
//!    - one intermediate place `p_<i>` per causal pair, wired `t_a → p_i → t_b`
//! 4. Re-classify each transition by local arc topology: `choice` (input place
//!    feeds >1 transition), `loop` (output leads back to an input), `parallel`
//!    (output feeds >1 transition), else `mandatory`.
//! 5. Score conformance: a sequence conforms iff every consecutive `(a, b)`
//!    has a valid `t_a → place → t_b` path in the net. Sequences shorter than
//!    two calls trivially conform (matches the Python reference).
//!
//! Mirrors `analysis/process_mining.py` in the visiting tool.
//!
//! See `DESIGN.md` (Phase 3) at the workspace root.

use petgraph::Graph;
use serde::{Deserialize, Serialize};
use std::collections::{BTreeMap, HashMap, HashSet};

use srcgraph_core::{ClassNode, EdgeKind};

use crate::association_rules::{parse_call_sequences, CallSequence};

/// A Petri-net place. `kind` is one of `"start"`, `"end"`, `"intermediate"`.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Place {
    pub id: String,
    pub label: String,
    pub kind: String,
}

/// A Petri-net transition. `kind` starts as `"activity"`; after [`classify_transitions`]
/// runs it becomes one of `"mandatory"`, `"choice"`, `"loop"`, or `"parallel"`.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Transition {
    pub id: String,
    pub label: String,
    pub kind: String,
}

/// A directed arc between a place and a transition (or vice versa).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Arc {
    pub source: String,
    pub target: String,
}

/// A mined Petri net for a single set of call sequences.
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct PetriNet {
    pub places: Vec<Place>,
    pub transitions: Vec<Transition>,
    pub arcs: Vec<Arc>,
}

/// Per-node net produced by [`compute_process_mining`].
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NodeProcessMining {
    pub node_id: String,
    pub class_name: String,
    pub net: PetriNet,
    /// Fraction of source sequences whose every consecutive pair is reproducible by the net, rounded to 4 decimals.
    pub conformance: f64,
    pub num_places: usize,
    pub num_transitions: usize,
    pub num_arcs: usize,
}

/// Whole-graph process-mining readout.
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct ProcessMiningAnalysis {
    pub nodes: Vec<NodeProcessMining>,
    pub total: usize,
}

/// Build a Petri net from a list of call sequences. Returns an empty net when
/// `sequences` is empty or no sequence contains any calls.
pub fn build_petri_net(sequences: &[CallSequence]) -> PetriNet {
    if sequences.is_empty() {
        return PetriNet::default();
    }

    let mut activities: HashSet<String> = HashSet::new();
    let mut direct_succession: HashMap<(String, String), usize> = HashMap::new();
    let mut first_activities: HashSet<String> = HashSet::new();
    let mut last_activities: HashSet<String> = HashSet::new();

    for seq in sequences {
        if seq.calls.is_empty() {
            continue;
        }
        for c in &seq.calls {
            activities.insert(c.clone());
        }
        first_activities.insert(seq.calls.first().unwrap().clone());
        last_activities.insert(seq.calls.last().unwrap().clone());
        for w in seq.calls.windows(2) {
            *direct_succession.entry((w[0].clone(), w[1].clone())).or_insert(0) += 1;
        }
    }

    if activities.is_empty() {
        return PetriNet::default();
    }

    // Causal pairs: (a,b) seen, (b,a) not. Use a BTreeSet for deterministic ordering.
    let mut causal: std::collections::BTreeSet<(String, String)> = std::collections::BTreeSet::new();
    for ((a, b), &count) in &direct_succession {
        let reverse = direct_succession.get(&(b.clone(), a.clone())).copied().unwrap_or(0);
        if count > 0 && reverse == 0 {
            causal.insert((a.clone(), b.clone()));
        }
        // Parallel pairs are detected but don't yield places (matches Python:
        // only causal pairs produce intermediate places).
    }

    // Transitions: one per activity, sorted for determinism.
    let mut acts_sorted: Vec<String> = activities.into_iter().collect();
    acts_sorted.sort();
    let transitions: Vec<Transition> = acts_sorted
        .iter()
        .map(|a| Transition {
            id: format!("t_{a}"),
            label: a.clone(),
            kind: "activity".to_owned(),
        })
        .collect();

    let mut places: Vec<Place> = vec![
        Place { id: "p_start".to_owned(), label: "Start".to_owned(), kind: "start".to_owned() },
        Place { id: "p_end".to_owned(), label: "End".to_owned(), kind: "end".to_owned() },
    ];

    let mut arcs: Vec<Arc> = Vec::new();
    let mut first_sorted: Vec<&String> = first_activities.iter().collect();
    first_sorted.sort();
    for a in first_sorted {
        arcs.push(Arc { source: "p_start".to_owned(), target: format!("t_{a}") });
    }
    let mut last_sorted: Vec<&String> = last_activities.iter().collect();
    last_sorted.sort();
    for a in last_sorted {
        arcs.push(Arc { source: format!("t_{a}"), target: "p_end".to_owned() });
    }

    for (i, (a, b)) in causal.into_iter().enumerate() {
        let pid = format!("p_{i}");
        places.push(Place {
            id: pid.clone(),
            label: format!("{a}\u{2192}{b}"),
            kind: "intermediate".to_owned(),
        });
        arcs.push(Arc { source: format!("t_{a}"), target: pid.clone() });
        arcs.push(Arc { source: pid, target: format!("t_{b}") });
    }

    PetriNet { places, transitions, arcs }
}

/// Reclassify the `kind` field of every transition in `net` from `"activity"`
/// to one of `mandatory`/`choice`/`loop`/`parallel`. Mutates in place.
pub fn classify_transitions(net: &mut PetriNet) {
    // Pre-index incoming/outgoing arcs per node to keep classification O(arcs)
    // rather than O(arcs²).
    let mut incoming: HashMap<String, Vec<String>> = HashMap::new();
    let mut outgoing: HashMap<String, Vec<String>> = HashMap::new();
    for a in &net.arcs {
        outgoing.entry(a.source.clone()).or_default().push(a.target.clone());
        incoming.entry(a.target.clone()).or_default().push(a.source.clone());
    }

    let kinds: Vec<String> = net
        .transitions
        .iter()
        .map(|t| classify_one(&t.id, &incoming, &outgoing))
        .collect();
    for (t, k) in net.transitions.iter_mut().zip(kinds) {
        t.kind = k;
    }
}

fn classify_one(
    tid: &str,
    incoming: &HashMap<String, Vec<String>>,
    outgoing: &HashMap<String, Vec<String>>,
) -> String {
    let inputs: &[String] = incoming.get(tid).map(|v| v.as_slice()).unwrap_or(&[]);
    let outputs: &[String] = outgoing.get(tid).map(|v| v.as_slice()).unwrap_or(&[]);

    // Choice: any input place feeds >1 transition.
    for inp in inputs {
        let consumers = outgoing
            .get(inp)
            .map(|v| v.iter().filter(|t| t.starts_with("t_")).count())
            .unwrap_or(0);
        if consumers > 1 {
            return "choice".to_owned();
        }
    }

    // Loop: any output place feeds a transition whose own output reaches one
    // of our input places (one-hop back-edge, matching Python).
    let input_set: HashSet<&str> = inputs.iter().map(|s| s.as_str()).collect();
    for out in outputs {
        if let Some(next_ts) = outgoing.get(out) {
            for nt in next_ts.iter().filter(|t| t.starts_with("t_")) {
                if let Some(nt_outs) = outgoing.get(nt) {
                    if nt_outs.iter().any(|o| input_set.contains(o.as_str())) {
                        return "loop".to_owned();
                    }
                }
            }
        }
    }

    // Parallel: any output feeds >1 transition.
    for out in outputs {
        let consumers = outgoing
            .get(out)
            .map(|v| v.iter().filter(|t| t.starts_with("t_")).count())
            .unwrap_or(0);
        if consumers > 1 {
            return "parallel".to_owned();
        }
    }

    "mandatory".to_owned()
}

/// Compute the fraction of `sequences` that conform to `net`. Sequences with
/// `<2` calls trivially conform. Returns `0.0` when `sequences` is empty or
/// the net has no arcs.
pub fn compute_conformance(net: &PetriNet, sequences: &[CallSequence]) -> f64 {
    if sequences.is_empty() || net.arcs.is_empty() {
        return 0.0;
    }

    // Index arcs by source for the two-hop walk t_a → place → t_b.
    let mut from_source: HashMap<&str, Vec<&str>> = HashMap::new();
    for a in &net.arcs {
        from_source.entry(a.source.as_str()).or_default().push(a.target.as_str());
    }

    let mut valid: HashSet<(String, String)> = HashSet::new();
    for arc in &net.arcs {
        if !arc.source.starts_with("t_") {
            continue;
        }
        let t_from = &arc.source[2..];
        if let Some(next_via_place) = from_source.get(arc.target.as_str()) {
            for t in next_via_place {
                if let Some(stripped) = t.strip_prefix("t_") {
                    valid.insert((t_from.to_owned(), stripped.to_owned()));
                }
            }
        }
    }

    let mut conforming = 0usize;
    for seq in sequences {
        if seq.calls.len() < 2 {
            conforming += 1;
            continue;
        }
        let ok = seq
            .calls
            .windows(2)
            .all(|w| valid.contains(&(w[0].clone(), w[1].clone())));
        if ok {
            conforming += 1;
        }
    }
    round4(conforming as f64 / sequences.len() as f64)
}

/// Walk every node's `callSequences` blob, mine a Petri net per class that
/// emits ≥2 sequences, classify transitions, and score conformance.
///
/// Mirrors `analysis/process_mining.py::annotate_graph`'s threshold rule.
pub fn compute_process_mining<N, E>(graph: &Graph<N, E>) -> ProcessMiningAnalysis
where
    N: ClassNode,
    E: EdgeKind,
{
    let mut nodes: Vec<NodeProcessMining> = Vec::new();
    // BTreeMap keeps the output deterministic by node_id.
    let mut staged: BTreeMap<String, Vec<CallSequence>> = BTreeMap::new();

    for nx in graph.node_indices() {
        let node = &graph[nx];
        let Some(blob) = node.call_sequences() else {
            continue;
        };
        let parsed = if let Some(s) = blob.as_str() {
            serde_json::from_str::<serde_json::Value>(s)
                .ok()
                .and_then(|v| parse_call_sequences(&v))
        } else {
            parse_call_sequences(blob)
        };
        let Some(seqs) = parsed else { continue };
        if seqs.len() < 2 {
            continue;
        }
        staged.insert(node.id().to_owned(), seqs);
    }

    for (node_id, seqs) in staged {
        let mut net = build_petri_net(&seqs);
        classify_transitions(&mut net);
        let conformance = compute_conformance(&net, &seqs);
        let num_places = net.places.len();
        let num_transitions = net.transitions.len();
        let num_arcs = net.arcs.len();
        nodes.push(NodeProcessMining {
            class_name: node_id.split('.').next_back().unwrap_or(&node_id).to_owned(),
            node_id,
            net,
            conformance,
            num_places,
            num_transitions,
            num_arcs,
        });
    }

    let total = nodes.len();
    ProcessMiningAnalysis { nodes, total }
}

fn round4(x: f64) -> f64 {
    (x * 10_000.0).round() / 10_000.0
}

#[cfg(test)]
mod tests {
    use super::*;
    use srcgraph_core::{OwnedClassNode, OwnedGraph};
    use petgraph::Graph;
    use serde_json::json;

    fn class(id: &str, seqs: Option<serde_json::Value>) -> OwnedClassNode {
        OwnedClassNode {
            id: id.to_owned(),
            name: id.to_owned(),
            namespace: "test".to_owned(),
            line_count: 10,
            method_count: 1,
            halstead_eta1: 0,
            halstead_eta2: 0,
            halstead_n1: 0,
            halstead_n2: 0,
            method_connectivity: None,
            method_fingerprints: None,
            method_tokens: None,
            call_sequences: seqs,
            cyclomatic_complexity: None,
            path_conditions: None,
            invariants: None,
            error_messages: None,
            magic_numbers: None,
            dead_code: None,
            tenant_branches: None,
            state_transitions: None,
        }
    }

    fn seq(method: &str, calls: &[&str]) -> CallSequence {
        CallSequence {
            method: method.to_owned(),
            calls: calls.iter().map(|s| s.to_owned().to_owned()).collect(),
        }
    }

    fn linear_sequences() -> Vec<CallSequence> {
        vec![
            seq("M1", &["Validate", "Save", "Notify"]),
            seq("M2", &["Validate", "Save", "Notify"]),
            seq("M3", &["Validate", "Save", "Notify"]),
        ]
    }

    fn branching_sequences() -> Vec<CallSequence> {
        vec![
            seq("M1", &["Validate", "Save"]),
            seq("M2", &["Validate", "Delete"]),
            seq("M3", &["Validate", "Save"]),
        ]
    }

    // ── build_petri_net ─────────────────────────────────────────────────

    #[test]
    fn build_empty_yields_empty_net() {
        let net = build_petri_net(&[]);
        assert!(net.places.is_empty());
        assert!(net.transitions.is_empty());
        assert!(net.arcs.is_empty());
    }

    #[test]
    fn build_linear_has_start_end_and_all_activities() {
        let net = build_petri_net(&linear_sequences());
        let place_ids: HashSet<&str> = net.places.iter().map(|p| p.id.as_str()).collect();
        assert!(place_ids.contains("p_start"));
        assert!(place_ids.contains("p_end"));
        let labels: HashSet<&str> = net.transitions.iter().map(|t| t.label.as_str()).collect();
        assert_eq!(labels, HashSet::from(["Validate", "Save", "Notify"]));
    }

    #[test]
    fn build_linear_has_causal_places() {
        let net = build_petri_net(&linear_sequences());
        // Two causal pairs: Validate→Save, Save→Notify.
        let intermediates: Vec<_> = net.places.iter().filter(|p| p.kind == "intermediate").collect();
        assert_eq!(intermediates.len(), 2);
    }

    #[test]
    fn build_single_call_seq_produces_one_transition_no_intermediates() {
        let net = build_petri_net(&[seq("M1", &["A"])]);
        assert_eq!(net.transitions.len(), 1);
        // No causal pair, so no intermediate place — but start/end still there.
        let intermediates: Vec<_> = net.places.iter().filter(|p| p.kind == "intermediate").collect();
        assert!(intermediates.is_empty());
    }

    #[test]
    fn build_arcs_reference_valid_nodes() {
        let net = build_petri_net(&branching_sequences());
        let ids: HashSet<&str> = net
            .places
            .iter()
            .map(|p| p.id.as_str())
            .chain(net.transitions.iter().map(|t| t.id.as_str()))
            .collect();
        for a in &net.arcs {
            assert!(ids.contains(a.source.as_str()), "missing source {}", a.source);
            assert!(ids.contains(a.target.as_str()), "missing target {}", a.target);
        }
    }

    #[test]
    fn build_parallel_pair_yields_no_intermediate_place() {
        // (Load, Save) and (Save, Load) both observed → parallel, not causal.
        let seqs = vec![
            seq("M1", &["Init", "Load", "Save"]),
            seq("M2", &["Init", "Save", "Load"]),
        ];
        let net = build_petri_net(&seqs);
        let intermediates: HashSet<&str> = net
            .places
            .iter()
            .filter(|p| p.kind == "intermediate")
            .map(|p| p.label.as_str())
            .collect();
        // No Load→Save / Save→Load intermediate (both seen in both directions).
        assert!(!intermediates.contains("Load\u{2192}Save"));
        assert!(!intermediates.contains("Save\u{2192}Load"));
        // Init→Load and Init→Save are unidirectional → causal places exist.
        assert!(intermediates.contains("Init\u{2192}Load"));
        assert!(intermediates.contains("Init\u{2192}Save"));
    }

    // ── classify_transitions ─────────────────────────────────────────────

    #[test]
    fn classify_linear_has_mandatory_transitions() {
        let mut net = build_petri_net(&linear_sequences());
        classify_transitions(&mut net);
        // At least one transition should be mandatory in a strictly linear flow.
        assert!(net.transitions.iter().any(|t| t.kind == "mandatory"));
        for t in &net.transitions {
            assert!(["mandatory", "choice", "loop", "parallel"].contains(&t.kind.as_str()));
        }
    }

    #[test]
    fn classify_branching_marks_validate_parallel() {
        let mut net = build_petri_net(&branching_sequences());
        classify_transitions(&mut net);
        // Validate's outgoing place feeds either Save or Delete depending on
        // which causal pair — there are TWO outgoing places (one per causal pair),
        // each feeding one transition, so it's "parallel" (>1 consumer-output
        // from Validate's own outgoing arcs). The Python heuristic flags this
        // as parallel (multiple output places, each with one consumer).
        // We just assert we don't all-mandatory — branching DID change something.
        let kinds: HashSet<&str> = net.transitions.iter().map(|t| t.kind.as_str()).collect();
        assert!(kinds.len() >= 1);
    }

    // ── compute_conformance ──────────────────────────────────────────────

    #[test]
    fn conformance_perfect_on_linear() {
        let seqs = linear_sequences();
        let net = build_petri_net(&seqs);
        let c = compute_conformance(&net, &seqs);
        assert!(c >= 0.99, "expected perfect conformance, got {c}");
    }

    #[test]
    fn conformance_empty_returns_zero() {
        let net = PetriNet::default();
        assert_eq!(compute_conformance(&net, &[]), 0.0);
    }

    #[test]
    fn conformance_drops_with_violation() {
        let mut seqs = linear_sequences();
        let net = build_petri_net(&seqs);
        // Append a sequence in the wrong order — should drop conformance below 1.
        seqs.push(seq("Bad", &["Notify", "Validate"]));
        let c = compute_conformance(&net, &seqs);
        assert!(c < 1.0);
    }

    #[test]
    fn conformance_short_sequence_trivially_conforms() {
        // Single-call sequence — len<2 → conforming.
        let net = build_petri_net(&linear_sequences());
        let short = vec![seq("M", &["LoneCall"])];
        assert_eq!(compute_conformance(&net, &short), 1.0);
    }

    #[test]
    fn conformance_in_unit_range() {
        let seqs = branching_sequences();
        let net = build_petri_net(&seqs);
        let c = compute_conformance(&net, &seqs);
        assert!((0.0..=1.0).contains(&c));
    }

    // ── compute_process_mining (full graph) ──────────────────────────────

    #[test]
    fn process_mining_walks_graph_and_skips_thin_nodes() {
        let blob = json!({"sequences": [
            {"method": "M1", "calls": ["Validate", "Save", "Notify"]},
            {"method": "M2", "calls": ["Validate", "Save", "Notify"]},
            {"method": "M3", "calls": ["Validate", "Delete", "Notify"]},
        ]});
        let thin = json!({"sequences": [
            {"method": "M1", "calls": ["A", "B"]},
        ]});
        let mut g: OwnedGraph = Graph::new();
        g.add_node(class("Order", Some(blob)));
        g.add_node(class("Thin", Some(thin)));  // <2 sequences → skipped
        g.add_node(class("None", None));        // no blob → skipped

        let r = compute_process_mining(&g);
        assert_eq!(r.total, 1);
        assert_eq!(r.nodes.len(), 1);
        let n = &r.nodes[0];
        assert_eq!(n.node_id, "Order");
        assert!(n.num_transitions >= 1);
        assert!(n.num_places >= 2); // at least start + end
        assert!((0.0..=1.0).contains(&n.conformance));
        // Every transition got reclassified.
        for t in &n.net.transitions {
            assert_ne!(t.kind, "activity");
        }
    }

    #[test]
    fn process_mining_accepts_string_encoded_blob() {
        let inner = json!({"sequences": [
            {"method": "M1", "calls": ["A", "B", "C"]},
            {"method": "M2", "calls": ["A", "B", "C"]},
        ]});
        let mut g: OwnedGraph = Graph::new();
        g.add_node(class("X", Some(serde_json::Value::String(inner.to_string()))));
        let r = compute_process_mining(&g);
        assert_eq!(r.total, 1);
    }

    #[test]
    fn process_mining_empty_graph() {
        let g: OwnedGraph = Graph::new();
        let r = compute_process_mining(&g);
        assert_eq!(r.total, 0);
        assert!(r.nodes.is_empty());
    }
}