#include <c_Topological.h>
#include "c_DirectedCycle.h"
#include "c_DepthFirstOrder.h"

c_err_t c_Topological_Init(c_Topological_t* self, c_Digraph_t* graph, c_Allocator_t* allocator) {
    if (!self || !graph) return C_ERR_PARAM;

    self->allocator = allocator ? *allocator : c_DefaultAllocator;
    self->has_order = C_FALSE;
    c_VertexIdList_Init(&self->order, 0, allocator);

    /* 1. Cycle Check: Verify the graph is a Directed Acyclic Graph (DAG) */
    c_DirectedCycle_t cycle_detector;
    c_err_t err = c_DirectedCycle_Init(&cycle_detector, graph, allocator);
    if (err != C_SUCCESS) return err;

    c_bool_t has_cycle = c_DirectedCycle_HasCycle(&cycle_detector);
    c_DirectedCycle_Destroy(&cycle_detector);

    /* If a cycle is present, it is not a DAG; skip order calculation and return success */
    if (has_cycle) {
        return C_SUCCESS;
    }

    /* 2. Compute Depth-First Order streams */
    c_DepthFirstOrder_t dfs_order;
    err = c_DepthFirstOrder_Init(&dfs_order, graph, allocator);
    if (err != C_SUCCESS) return err;

    /* 3. Extract the Reverse Post-Order stream directly using high-speed copy */
    err = c_DepthFirstOrder_GetReversePost(&dfs_order, &self->order);
    c_DepthFirstOrder_Destroy(&dfs_order);

    if (err != C_SUCCESS) return err;

    self->has_order = C_TRUE;
    return C_SUCCESS;
}

void c_Topological_Destroy(c_Topological_t* self) {
    if (!self) return;
    c_VertexIdList_Destroy(&self->order);
    self->has_order = C_FALSE;
}

c_err_t c_Topological_GetOrder(c_Topological_t* self, c_VertexIdList_t* out_order) {
    if (!self || !out_order) return C_ERR_PARAM;
    if (!self->has_order) return C_ERR_FAIL;

    /* High-speed block copy of the pre-computed topological sequence */
    return c_VertexIdList_Copy(out_order, (c_UIntArray_t*)&self->order);
}