#ifndef INCLUDED_C_DIJKSTRASP_H
#define INCLUDED_C_DIJKSTRASP_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 tracking matrix */
    c_size_t           s;             /* The starting 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_DijkstraSP_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_DijkstraSP_Init(c_DijkstraSP_t* self, c_EdgeWeightedDigraph_t* graph, c_size_t s, c_Allocator_t* allocator);

/**
 * @brief Releases internal tracking buffers safely.
 */
void c_DijkstraSP_Destroy(c_DijkstraSP_t* self);

/**
 * @brief Is there a directed path from the source vertex 's' to vertex 'v'?
 */
C_STATIC_FORCE_INLINE
c_bool_t c_DijkstraSP_HasPathTo(c_DijkstraSP_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'.
 * @return Distance value, or DBL_MAX if unreachable / parameter error
 */
C_STATIC_FORCE_INLINE
double c_DijkstraSP_DistTo(c_DijkstraSP_t* self, c_size_t v) {
    if (!self || v >= self->V || !self->dist_to) return DBL_MAX;
    return self->dist_to[v];
}

/**
 * @brief Reconstructs the exact shortest path from the source vertex 's' to vertex 'v' and appends it to out_path.
 * @param out_path An initialized c_VertexIdList_t container to collect the sequence of global directed edge_ids.
 */
c_err_t c_DijkstraSP_PathTo(c_DijkstraSP_t* self, c_size_t v, c_VertexIdList_t* out_path);



#endif /*INCLUDED_C_DIJKSTRASP_H*/