tramli 3.8.0

use std::collections::HashSet;
use std::time::Instant;

use crate::context::FlowContext;
use crate::definition::FlowDefinition;
use crate::types::FlowState;

pub struct FlowInstance<S: FlowState> {
    pub id: String,
    pub session_id: String,
    pub definition: std::sync::Arc<FlowDefinition<S>>,
    pub context: FlowContext,
    current_state: S,
    guard_failure_count: usize,
    guard_failure_counts: std::collections::HashMap<String, usize>,
    version: u32,
    pub created_at: Instant,
    pub expires_at: Instant,
    state_entered_at: Instant,
    last_error: Option<String>,
    exit_state: Option<String>,
}

impl<S: FlowState> FlowInstance<S> {
    pub fn new(
        id: String, session_id: String,
        definition: std::sync::Arc<FlowDefinition<S>>,
        context: FlowContext, current_state: S, expires_at: Instant,
    ) -> Self {
        let now = Instant::now();
        Self {
            id, session_id, definition, context, current_state,
            guard_failure_count: 0, guard_failure_counts: std::collections::HashMap::new(),
            version: 0, created_at: now, expires_at, state_entered_at: now,
            last_error: None, exit_state: None,
        }
    }

    /// Restore from persisted state.
    pub fn restore(
        id: String, session_id: String,
        definition: std::sync::Arc<FlowDefinition<S>>,
        context: FlowContext, current_state: S,
        created_at: Instant, expires_at: Instant,
        guard_failure_count: usize, version: u32,
        exit_state: Option<String>,
    ) -> Self {
        Self {
            id, session_id, definition, context, current_state,
            guard_failure_count, guard_failure_counts: std::collections::HashMap::new(),
            version, created_at, expires_at,
            state_entered_at: created_at, last_error: None, exit_state,
        }
    }

    pub fn current_state(&self) -> S { self.current_state }
    pub fn guard_failure_count(&self) -> usize { self.guard_failure_count }
    /// Guard failure count for a specific guard (by name).
    pub fn guard_failure_count_for(&self, guard_name: &str) -> usize {
        self.guard_failure_counts.get(guard_name).copied().unwrap_or(0)
    }
    pub fn version(&self) -> u32 { self.version }
    pub fn exit_state(&self) -> Option<&str> { self.exit_state.as_deref() }
    pub fn is_completed(&self) -> bool { self.exit_state.is_some() }
    /// Last error message (set when a processor throws and error transition fires).
    pub fn last_error(&self) -> Option<&str> { self.last_error.as_deref() }

    /// State path from root. E.g. ["PAYMENT", "CONFIRM"].
    pub fn state_path(&self) -> Vec<String> {
        vec![format!("{:?}", self.current_state)]
    }

    /// State path as slash-separated string.
    pub fn state_path_string(&self) -> String {
        self.state_path().join("/")
    }

    /// Data types available in context at current state (from data-flow graph).
    pub fn available_data(&self) -> HashSet<std::any::TypeId> {
        self.definition.data_flow_graph().available_at(self.current_state)
    }

    /// Data types that the next transition requires but are not yet in context.
    pub fn missing_for(&self) -> Vec<std::any::TypeId> {
        let mut missing = Vec::new();
        for t in self.definition.transitions_from(self.current_state) {
            if let Some(g) = &t.guard {
                for r in g.requires() { if !self.context.has_type_id(&r) { missing.push(r); } }
            }
            if let Some(p) = &t.processor {
                for r in p.requires() { if !self.context.has_type_id(&r) { missing.push(r); } }
            }
        }
        missing.sort();
        missing.dedup();
        missing
    }

    /// Types required by the next external transition.
    pub fn waiting_for(&self) -> Vec<std::any::TypeId> {
        if let Some(ext) = self.definition.external_from(self.current_state) {
            if let Some(g) = &ext.guard {
                return g.requires();
            }
        }
        Vec::new()
    }

    /// Update the version in-place. For FlowStore optimistic locking after save.
    pub fn set_version_public(&mut self, new_version: u32) {
        self.version = new_version;
    }

    pub fn state_entered_at(&self) -> Instant { self.state_entered_at }
    pub(crate) fn transition_to(&mut self, state: S) {
        let changed = self.current_state != state;
        self.current_state = state;
        self.state_entered_at = Instant::now();
        if changed { self.guard_failure_count = 0; self.guard_failure_counts.clear(); }
    }
    pub(crate) fn increment_guard_failure(&mut self) { self.guard_failure_count += 1; }
    pub(crate) fn increment_guard_failure_named(&mut self, guard_name: &str) {
        self.guard_failure_count += 1;
        *self.guard_failure_counts.entry(guard_name.to_string()).or_default() += 1;
    }
    pub(crate) fn set_last_error(&mut self, error: impl Into<String>) { self.last_error = Some(error.into()); }
    pub(crate) fn complete(&mut self, exit_state: impl Into<String>) { self.exit_state = Some(exit_state.into()); }
}