fn_registry/cpp/functions/viz/graph_viewport.cpp

#include "viz/graph_viewport.h"
#include "viz/graph_types.h"
#include "viz/graph_renderer.h"
#include "viz/graph_force_layout.h"
#include "core/graph_spatial_hash.h"
#include "imgui.h"

#include <cstdio>   // snprintf
#include <cstring>  // memset
#include <vector>

// ---------------------------------------------------------------------------
// Internal helpers
// ---------------------------------------------------------------------------

static void viewport_to_graph(float vx, float vy,
                               float widget_x, float widget_y,
                               float widget_w, float widget_h,
                               float cam_x, float cam_y, float zoom,
                               float& gx, float& gy)
{
    gx = (vx - widget_x - widget_w * 0.5f) / zoom + cam_x;
    gy = (vy - widget_y - widget_h * 0.5f) / zoom + cam_y;
}

// ---------------------------------------------------------------------------
// graph_viewport_fit
// ---------------------------------------------------------------------------

void graph_viewport_fit(GraphData& graph, GraphViewportState& state)
{
    graph.update_bounds();
    if (graph.node_count == 0) {
        state.cam_x = 0.0f;
        state.cam_y = 0.0f;
        state.zoom  = 1.0f;
        return;
    }

    float cx = (graph.min_x + graph.max_x) * 0.5f;
    float cy = (graph.min_y + graph.max_y) * 0.5f;
    state.cam_x = cx;
    state.cam_y = cy;

    float span_x = graph.max_x - graph.min_x;
    float span_y = graph.max_y - graph.min_y;
    float span   = (span_x > span_y ? span_x : span_y);

    // Use render dimensions if available; fall back to a safe default.
    float view_px = (state.render_w > 0 ? (float)state.render_w : 600.0f);
    float view_py = (state.render_h > 0 ? (float)state.render_h : 400.0f);
    float view_min = (view_px < view_py ? view_px : view_py);

    if (span > 0.0f) {
        state.zoom = (view_min * 0.9f) / span;
    } else {
        state.zoom = 1.0f;
    }

    // Clamp to allowed range
    if (state.zoom < state.zoom_min) state.zoom = state.zoom_min;
    if (state.zoom > state.zoom_max) state.zoom = state.zoom_max;
}

// ---------------------------------------------------------------------------
// graph_viewport_destroy
// ---------------------------------------------------------------------------

void graph_viewport_destroy(GraphViewportState& state)
{
    if (state.renderer) {
        graph_renderer_destroy(state.renderer);
        state.renderer = nullptr;
    }
    if (state.spatial) {
        delete state.spatial;
        state.spatial = nullptr;
    }
    state.initialized = false;
}

// ---------------------------------------------------------------------------
// graph_viewport — main widget
// ---------------------------------------------------------------------------

bool graph_viewport(const char* id, GraphData& graph, GraphViewportState& state,
                    ImVec2 size)
{
    bool interacted = false;

    // Resolve size
    ImVec2 avail = ImGui::GetContentRegionAvail();
    float w = (size.x > 0.0f) ? size.x : avail.x;
    float h = (size.y > 0.0f) ? size.y : avail.y;
    if (w < 1.0f) w = 1.0f;
    if (h < 1.0f) h = 1.0f;

    int iw = (int)w, ih = (int)h;

    // -------------------------------------------------------------------
    // 1. Lazy init
    // -------------------------------------------------------------------
    if (!state.initialized) {
        state.renderer  = graph_renderer_create(iw, ih);
        state.spatial   = new SpatialHash(20.0f, 4096);
        state.render_w  = iw;
        state.render_h  = ih;
        state.initialized = true;
        graph_viewport_fit(graph, state);
    }

    // -------------------------------------------------------------------
    // 2. Resize
    // -------------------------------------------------------------------
    if (iw != state.render_w || ih != state.render_h) {
        graph_renderer_resize(state.renderer, iw, ih);
        state.render_w = iw;
        state.render_h = ih;
    }

    // -------------------------------------------------------------------
    // 3. Force layout step
    // -------------------------------------------------------------------
    if (state.layout_running && graph.node_count > 0) {
        state.layout_energy = graph_force_layout_step(graph);
        if (state.layout_energy < 0.01f) {
            state.layout_running = false;
        }
    }

    // -------------------------------------------------------------------
    // 4. Build spatial hash
    // -------------------------------------------------------------------
    if (graph.node_count > 0) {
        static std::vector<float> xs_buf, ys_buf, sz_buf;
        xs_buf.resize(graph.node_count);
        ys_buf.resize(graph.node_count);
        sz_buf.resize(graph.node_count);
        for (int i = 0; i < graph.node_count; ++i) {
            xs_buf[i] = graph.nodes[i].x;
            ys_buf[i] = graph.nodes[i].y;
            sz_buf[i] = graph.nodes[i].size;
        }
        state.spatial->build(xs_buf.data(), ys_buf.data(), sz_buf.data(), graph.node_count);
    }

    // -------------------------------------------------------------------
    // 5. Invisible button to capture input
    // -------------------------------------------------------------------
    ImGui::PushID(id);

    ImVec2 widget_pos = ImGui::GetCursorScreenPos();
    ImGui::InvisibleButton("canvas", ImVec2(w, h),
                           ImGuiButtonFlags_MouseButtonLeft  |
                           ImGuiButtonFlags_MouseButtonMiddle|
                           ImGuiButtonFlags_MouseButtonRight);

    bool hovered  = ImGui::IsItemHovered();
    bool lm_down  = ImGui::IsMouseDown(ImGuiMouseButton_Left);
    bool lm_click = ImGui::IsMouseClicked(ImGuiMouseButton_Left);
    bool mm_down  = ImGui::IsMouseDown(ImGuiMouseButton_Middle);
    bool rm_down  = ImGui::IsMouseDown(ImGuiMouseButton_Right);

    ImVec2 mouse_pos = ImGui::GetMousePos();
    float  mx = mouse_pos.x, my = mouse_pos.y;

    // Convert mouse to graph space
    float gx_mouse, gy_mouse;
    viewport_to_graph(mx, my,
                      widget_pos.x, widget_pos.y, w, h,
                      state.cam_x, state.cam_y, state.zoom,
                      gx_mouse, gy_mouse);

    // -------------------------------------------------------------------
    // 5a. Pan (middle or right mouse drag)
    // -------------------------------------------------------------------
    if (hovered && (mm_down || rm_down)) {
        ImVec2 delta = ImGui::GetIO().MouseDelta;
        if (delta.x != 0.0f || delta.y != 0.0f) {
            state.cam_x -= delta.x / state.zoom;
            state.cam_y -= delta.y / state.zoom;
            interacted = true;
        }
    }

    // -------------------------------------------------------------------
    // 5b. Zoom (scroll wheel)
    // -------------------------------------------------------------------
    if (hovered) {
        float wheel = ImGui::GetIO().MouseWheel;
        if (wheel != 0.0f) {
            float old_zoom = state.zoom;
            float new_zoom = old_zoom * (1.0f + wheel * 0.1f);
            if (new_zoom < state.zoom_min) new_zoom = state.zoom_min;
            if (new_zoom > state.zoom_max) new_zoom = state.zoom_max;

            // Zoom toward cursor: keep gx_mouse/gy_mouse fixed in graph space
            float rel_x = (mx - widget_pos.x - w * 0.5f);
            float rel_y = (my - widget_pos.y - h * 0.5f);
            state.cam_x += rel_x / old_zoom - rel_x / new_zoom;
            state.cam_y += rel_y / old_zoom - rel_y / new_zoom;
            state.zoom   = new_zoom;
            interacted   = true;
        }
    }

    // -------------------------------------------------------------------
    // 5c. Hover — query nearest node
    // -------------------------------------------------------------------
    state.hovered_node = -1;
    if (hovered && graph.node_count > 0) {
        float hit_radius = 10.0f / state.zoom;
        int nearest = state.spatial->query_nearest(gx_mouse, gy_mouse, hit_radius);
        if (nearest >= 0) {
            state.hovered_node = nearest;
            interacted = true;
        }
    }

    // -------------------------------------------------------------------
    // 5d. Node drag (left mouse down on a node)
    // -------------------------------------------------------------------
    if (hovered && lm_down) {
        if (state.drag_node == -1 && state.hovered_node >= 0) {
            state.drag_node   = state.hovered_node;
            state.is_dragging = true;
        }
    } else {
        // Release drag
        if (state.drag_node >= 0 && state.drag_node < graph.node_count) {
            graph.nodes[state.drag_node].pinned = false;
        }
        state.drag_node   = -1;
        state.is_dragging = false;
    }

    if (state.drag_node >= 0 && state.drag_node < graph.node_count) {
        GraphNode& n = graph.nodes[state.drag_node];
        n.x      = gx_mouse;
        n.y      = gy_mouse;
        n.vx     = 0.0f;
        n.vy     = 0.0f;
        n.pinned = true;
        interacted = true;
    }

    // -------------------------------------------------------------------
    // 5e. Click — select node
    // -------------------------------------------------------------------
    if (hovered && lm_click && state.drag_node == -1) {
        state.selected_node = state.hovered_node;
        interacted = true;
    }

    // -------------------------------------------------------------------
    // 5f. Keyboard shortcuts (only when widget is active/hovered)
    // -------------------------------------------------------------------
    if (hovered) {
        if (ImGui::IsKeyPressed(ImGuiKey_Space)) {
            state.layout_running = !state.layout_running;
        }
        if (ImGui::IsKeyPressed(ImGuiKey_F)) {
            graph_viewport_fit(graph, state);
            interacted = true;
        }
    }

    // -------------------------------------------------------------------
    // 6. Render to GPU texture
    // -------------------------------------------------------------------
    unsigned int tex_id = graph_renderer_draw(state.renderer, graph,
                                              state.cam_x, state.cam_y,
                                              state.zoom);

    // -------------------------------------------------------------------
    // 7. Display texture (flip UV for OpenGL FBO convention)
    // -------------------------------------------------------------------
    ImDrawList* draw_list = ImGui::GetWindowDrawList();
    draw_list->AddImage(
        (ImTextureID)(intptr_t)tex_id,
        widget_pos,
        ImVec2(widget_pos.x + w, widget_pos.y + h),
        ImVec2(0.0f, 1.0f),   // UV top-left   (flipped Y)
        ImVec2(1.0f, 0.0f)    // UV bottom-right
    );

    // -------------------------------------------------------------------
    // 8. Tooltip on hovered node
    // -------------------------------------------------------------------
    if (state.hovered_node >= 0 && state.hovered_node < graph.node_count) {
        const GraphNode& n = graph.nodes[state.hovered_node];

        // Count degree
        int degree = 0;
        for (int i = 0; i < graph.edge_count; ++i) {
            if ((int)graph.edges[i].source == state.hovered_node ||
                (int)graph.edges[i].target == state.hovered_node) {
                ++degree;
            }
        }

        ImGui::BeginTooltip();
        if (n.label) ImGui::TextUnformatted(n.label);
        ImGui::Text("ID: %u", n.id);
        ImGui::Text("Community: %u", n.community);
        ImGui::Text("Degree: %d", degree);
        ImGui::Text("Value: %.3f", n.value);
        ImGui::EndTooltip();
    }

    // -------------------------------------------------------------------
    // 9. Status bar overlay
    // -------------------------------------------------------------------
    {
        char status[128];
        snprintf(status, sizeof(status),
                 "Nodes: %d | Edges: %d | Zoom: %.2fx | Energy: %.4f | [Space] layout [F] fit",
                 graph.node_count, graph.edge_count,
                 state.zoom, state.layout_energy);

        ImVec2 text_pos = ImVec2(widget_pos.x + 6.0f, widget_pos.y + h - 18.0f);
        draw_list->AddText(text_pos, IM_COL32(180, 180, 180, 200), status);
    }

    ImGui::PopID();
    return interacted;
}