#pragma once

struct GraphData; // forward declare

struct ForceLayoutConfig {
    float repulsion    = 500.0f;  // repulsion strength between all nodes
    float attraction   = 0.01f;   // spring constant for edges
    float damping      = 0.85f;   // velocity decay per step
    float min_distance = 1.0f;    // minimum distance (avoid division by zero)
    float theta        = 0.5f;    // Barnes-Hut threshold (0 = exact, 1 = fast)
    float gravity      = 0.1f;    // pull toward center (prevents drift)
    float max_velocity = 50.0f;   // cap velocity per axis
    int   iterations   = 1;       // steps per call
};

// Perform one (or more) steps of force-directed layout.
// Modifies node positions (x, y) and velocities (vx, vy) in-place.
// Returns the total kinetic energy (sum of |v|^2). When energy < threshold,
// layout has converged.
float graph_force_layout_step(GraphData& graph, const ForceLayoutConfig& config = {});

// Reset: randomize positions within [-spread, spread], zero velocities.
void graph_force_layout_reset(GraphData& graph, float spread = 200.0f);

// Preset layouts (non-iterative, instant positioning)
void graph_layout_circular(GraphData& graph, float radius = 100.0f);
void graph_layout_grid(GraphData& graph, float spacing = 20.0f);