#ifndef INCLUDED_C_BELLMANFORDSP_H
#define INCLUDED_C_BELLMANFORDSP_H

#ifndef INCLUDED_C_EDGEWEIGHTEDDIGRAPH_H
#include <c_EdgeWeightedDigraph.h>
#endif /*INCLUDED_C_EDGEWEIGHTEDDIGRAPH_H*/


#ifndef INCLUDED_C_VERTEXIDLIST_H
#include <c_VertexIdList.h>
#endif /*INCLUDED_C_VERTEXIDLIST_H*/


/* ------------------------------------------------------------------------------------------------------------------ */
/*  */

typedef struct {
    c_size_t*          edge_to;       /* edge_to[w] = entering directed edge_id on shortest path to w */
    c_size_t*          from_vertex;   /* from_vertex[w] = source vertex parent link on path to w */
    double*            dist_to;       /* dist_to[w] = cumulative distance from source s to w */
    c_bool_t*          on_queue;      /* on_queue[v] = is vertex v currently sitting inside the processing FIFO queue */
    c_VertexIdList_t   cycle;         /* Catches and stores the negative cycle path sequence if found */
    c_size_t           cost_counter;  /* Tracks number of relax calls to gauge periodic cycle check steps */
    c_size_t           s;             /* The source vertex index */
    c_size_t           V;             /* Total number of vertices in the digraph */
    c_Allocator_t      allocator;     /* Deep copy of the user-provided allocator */
} c_BellmanFordSP_t;

/* ------------------------------------------------------------------------------------------------------------------ */
/*  */

/**
 * @brief Computes a shortest-paths tree from the source vertex 's' in the edge-weighted digraph.
 * @param allocator Explicit allocator context used to configure internal tracking state memory
 */
c_err_t c_BellmanFordSP_Init(c_BellmanFordSP_t* self, c_EdgeWeightedDigraph_t* graph, c_size_t s, c_Allocator_t* allocator);

/**
 * @brief Releases internal tracking buffers safely.
 */
void c_BellmanFordSP_Destroy(c_BellmanFordSP_t* self);

/**
 * @brief Is there a directed path from the source vertex 's' to vertex 'v'?
 */
C_STATIC_FORCE_INLINE
c_bool_t c_BellmanFordSP_HasPathTo(c_BellmanFordSP_t* self, c_size_t v) {
    if (!self || v >= self->V || !self->dist_to) return C_FALSE;
    return self->dist_to[v] < DBL_MAX;
}

/**
 * @brief Returns the distance of the shortest path from the source vertex 's' to vertex 'v'.
 */
C_STATIC_FORCE_INLINE
double c_BellmanFordSP_DistTo(c_BellmanFordSP_t* self, c_size_t v) {
    if (!self || v >= self->V || !self->dist_to) return DBL_MAX;
    return self->dist_to[v];
}

/**
 * @brief Does the edge-weighted digraph contain a negative cycle reachable from the source vertex?
 */
C_STATIC_FORCE_INLINE
c_bool_t c_BellmanFordSP_HasNegativeCycle(c_BellmanFordSP_t* self) {
    if (!self) return C_FALSE;
    return !c_VertexIdList_IsEmpty(&self->cycle);
}

/**
 * @brief Reconstructs the exact shortest path from the source vertex 's' to vertex 'v' and appends it to out_path.
 */
c_err_t c_BellmanFordSP_PathTo(c_BellmanFordSP_t* self, c_size_t v, c_VertexIdList_t* out_path);

/**
 * @brief Extracts the vertices forming the detected negative cycle loop if present.
 */
c_err_t c_BellmanFordSP_GetNegativeCycle(c_BellmanFordSP_t* self, c_VertexIdList_t* out_cycle);


#endif /*INCLUDED_C_BELLMANFORDSP_H*/