#include "graph_widget.hpp"
#include "xtc/xtc_plugin.h"
#include <FL/Fl.H>
#include <FL/Fl_Box.H>
#include <FL/Fl_Group.H>
#include <FL/fl_draw.H>
#include <FL/Fl_Menu_Item.H>
#include <algorithm>
#include <cmath>
#include <cstdio>

namespace {
constexpr int node_width = 150, node_height = 74;

/**
 * @brief Returns the display label for a node type.
 *
 * @param type Node type to describe.
 * @return Borrowed static string; never NULL, falling back to "Unknown".
 */
const char *node_name(xtc_node_type type)
{
    switch (type) {
    case XTC_NODE_OSCILLATOR:
        return "Oscillator";
    case XTC_NODE_GAIN:
        return "Gain / bus";
    case XTC_NODE_METER:
        return "Meter";
    case XTC_NODE_PLUGIN:
        return "LADSPA plugin";
    case XTC_NODE_NATIVE:
        return "Native processor";
    case XTC_NODE_INSTRUMENT:
        return "MIDI mix";
    case XTC_NODE_AUDIO:
        return "Audio mix";
    case XTC_NODE_OUTPUT:
        return "Output sum";
    }
    return "Unknown";
}
} // namespace

/**
 * @brief Constructs the widget and initializes its cached layout from the graph.
 *
 * The graph, handler, context, and feedback box are stored without taking
 * ownership. Layout population is delegated to set_graph().
 *
 * @param left Left coordinate in FLTK screen space.
 * @param top Top coordinate in FLTK screen space.
 * @param width Widget width in pixels.
 * @param height Widget height in pixels.
 * @param graph Borrowed graph snapshot; must outlive the widget's use of it.
 * @param handler Edit callback invoked for every graph mutation.
 * @param context Opaque pointer passed back to @p handler; may be NULL.
 * @param feedback_box Borrowed label used to report edit results.
 */
GraphWidget::GraphWidget(int left, int top, int width, int height, const xtc_graph *graph, EditHandler handler,
                         void *context, Fl_Box *feedback_box)
    : Fl_Widget(left, top, width, height), graph_(graph), handler_(handler), context_(context), feedback_(feedback_box)
{
    set_graph(graph);
}

/**
 * @brief Replaces the graph snapshot and rebuilds cached node positions.
 *
 * Existing positions are preserved by node ID. New nodes get grid slots that do
 * not overlap previously known nodes. The selection is dropped when the selected
 * node or wire is no longer present. The widget does not take ownership of the
 * graph.
 *
 * @param graph Borrowed graph that must outlive the widget's use of it.
 */
void GraphWidget::set_graph(const xtc_graph *graph)
{
    graph_ = graph;
    routing_count_ = 0;
    (void)xtc_graph_analyze(graph_, routing_.data(), routing_.size(), &routing_count_);
    size_t nodes = 0U, edges = 0U;
    if (xtc_graph_get_counts(graph_, &nodes, &edges) != XTC_OK) {
        count_ = 0U;
        redraw();
        return;
    }
    auto old = positions_;
    size_t old_count = count_;
    count_ = 0U;
    for (size_t i = 0U; i < nodes && i < positions_.size(); ++i) {
        xtc_node_info node{};
        if (xtc_graph_get_node(graph_, i, &node) != XTC_OK)
            continue;
        Position position;
        position.id = node.id;
        bool found = false;
        for (size_t j = 0U; j < old_count; ++j)
            if (old[j].id == node.id) {
                position = old[j];
                found = true;
                break;
            }
        if (!found) {
            for (size_t slot = 0U; slot <= positions_.size(); ++slot) {
                position.left = 40 + static_cast<int>(slot % 8U) * 210;
                position.top = 40 + static_cast<int>(slot / 8U) * 115;
                bool occupied = false;
                for (size_t j = 0U; j < old_count; ++j)
                    if (std::abs(old[j].left - position.left) < node_width + 12 &&
                        std::abs(old[j].top - position.top) < node_height + 12)
                        occupied = true;
                for (size_t j = 0U; j < count_; ++j)
                    if (std::abs(positions_[j].left - position.left) < node_width + 12 &&
                        std::abs(positions_[j].top - position.top) < node_height + 12)
                        occupied = true;
                if (!occupied)
                    break;
            }
        }
        positions_[count_++] = position;
    }
    int left, top;
    if (!node_position(selected_node_, left, top))
        selected_node_ = SIZE_MAX;
    if (edge_selected_ && !select_connection(selected_edge_.source_node, selected_edge_.destination_node))
        edge_selected_ = false;
    grow_canvas();
    redraw();
}

/**
 * @brief Looks up the cached position of a node.
 *
 * @param id Stable node identifier.
 * @param left Receives the left position in widget-local coordinates.
 * @param top Receives the top position in widget-local coordinates.
 * @return True when the node has a cached position, false otherwise.
 */
bool GraphWidget::node_position(size_t id, int &left, int &top) const
{
    for (size_t i = 0U; i < count_; ++i)
        if (positions_[i].id == id) {
            left = positions_[i].left;
            top = positions_[i].top;
            return true;
        }
    return false;
}

/**
 * @brief Moves a node within the widget, clamped to the visible bounds.
 *
 * The node keeps a 12-pixel margin from the widget edges.
 *
 * @param id Stable node identifier.
 * @param left Requested left position in widget-local coordinates.
 * @param top Requested top position in widget-local coordinates.
 * @return True when the node has a cached position, false otherwise.
 */
bool GraphWidget::move_node(size_t id, int left, int top)
{
    for (size_t i = 0U; i < count_; ++i)
        if (positions_[i].id == id) {
            positions_[i].left = std::max(12, std::min(left, w() - node_width - 12));
            positions_[i].top = std::max(12, std::min(top, h() - node_height - 12));
            redraw();
            return true;
        }
    return false;
}

/**
 * @brief Selects a node by ID and clears any wire selection.
 *
 * @param id Stable node identifier.
 * @return True when the node has a cached position, false otherwise.
 */
bool GraphWidget::select_node(size_t id)
{
    int left, top;
    if (!node_position(id, left, top))
        return false;
    selected_node_ = id;
    edge_selected_ = false;
    describe_selection();
    redraw();
    return true;
}

/**
 * @brief Selects a wire between two nodes and clears the node selection.
 *
 * @param source Source node identifier.
 * @param destination Destination node identifier.
 * @return True when a matching connection exists, false otherwise.
 */
bool GraphWidget::select_connection(size_t source, size_t destination)
{
    size_t nodes, edges;
    if (xtc_graph_get_counts(graph_, &nodes, &edges) != XTC_OK)
        return false;
    for (size_t i = 0U; i < edges; ++i) {
        xtc_connection_info edge{};
        if (xtc_graph_get_connection(graph_, i, &edge) == XTC_OK && edge.source_node == source &&
            edge.destination_node == destination) {
            selected_edge_ = edge;
            edge_selected_ = true;
            selected_node_ = SIZE_MAX;
            describe_selection();
            redraw();
            return true;
        }
    }
    return false;
}

/**
 * @brief Shows the outcome of an edit in the feedback label.
 *
 * @param result Result returned by the edit handler.
 * @param success Text shown when @p result is XTC_OK; must be valid then and is ignored otherwise.
 */
void GraphWidget::feedback(xtc_result result, const char *success)
{
    char text[256];
    if (result == XTC_OK)
        std::snprintf(text, sizeof(text), "%s", success);
    else if (result == XTC_ERR_CAPACITY)
        std::snprintf(
            text, sizeof(text),
            "Graph unchanged: capacity exceeded (node limit or pending edit). Retry after the next audio block.");
    else if (result == XTC_ERR_GRAPH_CYCLE)
        std::snprintf(text, sizeof(text), "Graph unchanged: %s. Feedback loops are unsupported.", xtc_result_string(result));
    else
        std::snprintf(text, sizeof(text), "Graph unchanged: %s. Connect an audio output (right) to an input (left); duplicate wires are rejected.", xtc_result_string(result));
    feedback_->copy_label(text);
}

/**
 * @brief Requests creation of a node through the edit handler.
 *
 * Selects the new node when the edit succeeds.
 *
 * @param type Kind of node to add.
 * @return Result reported by the edit handler.
 */
xtc_result GraphWidget::add_node(xtc_node_type type)
{
    xtc_graph_edit edit{};
    edit.kind = XTC_EDIT_ADD_NODE;
    edit.data.add.type = type;
    edit.data.add.value = type == XTC_NODE_OSCILLATOR ? 440.0f : type == XTC_NODE_GAIN ? 0.1f : 0.0f;
    size_t added = SIZE_MAX;
    xtc_result result = handler_(context_, edit, &added);
    if (result == XTC_OK)
        select_node(added);
    feedback(result, "Node added. Drag its title to move; drag an output port to an input to connect.");
    return result;
}

/**
 * @brief Requests a connection between two ports through the edit handler.
 *
 * @param connection Connection describing the source and destination node/port pairs.
 * @return Result reported by the edit handler.
 */
xtc_result GraphWidget::connect_ports(const xtc_connection_info &connection)
{
    xtc_graph_edit edit{};
    edit.kind = XTC_EDIT_CONNECT;
    edit.data.connection = connection;
    xtc_result result = handler_(context_, edit, nullptr);
    feedback(result, "Connection added. Click a wire and press Delete to disconnect.");
    return result;
}

/**
 * @brief Requests removal of the selected wire or node through the edit handler.
 *
 * @return Result reported by the edit handler, or XTC_ERR_INVALID_STATE when
 *         nothing is selected.
 */
xtc_result GraphWidget::delete_selected()
{
    xtc_graph_edit edit{};
    if (edge_selected_) {
        edit.kind = XTC_EDIT_DISCONNECT;
        edit.data.connection = selected_edge_;
    } else if (selected_node_ != SIZE_MAX) {
        edit.kind = XTC_EDIT_REMOVE_NODE;
        edit.data.node_id = selected_node_;
    } else {
        feedback_->copy_label("Select a node or wire first.");
        return XTC_ERR_INVALID_STATE;
    }
    xtc_result result = handler_(context_, edit, nullptr);
    feedback(result, "Selection deleted. Unwired inputs use external audio; select a node to inspect routing.");
    return result;
}

/**
 * @brief Computes the widget-local center of a node port.
 *
 * @param id Stable node identifier.
 * @param port Port index; 0 selects the input and 1 the output.
 * @param left Receives the port center x coordinate.
 * @param top Receives the port center y coordinate.
 * @return True when the node and port exist, false otherwise.
 */
bool GraphWidget::port_position(size_t id, size_t port, int &left, int &top) const
{
    xtc_port_info info{};
    if (xtc_graph_get_port(graph_, id, port, &info) != XTC_OK || !node_position(id, left, top))
        return false;
    left += info.direction == XTC_PORT_OUTPUT ? node_width : 0;
    top += 48;
    return true;
}

/**
 * @brief Finds the port nearest to a widget-local point.
 *
 * Searches nodes in reverse draw order and accepts points within 9 pixels of a
 * port center.
 *
 * @param left Widget-local x coordinate to test.
 * @param top Widget-local y coordinate to test.
 * @param node Receives the matching node ID when true is returned.
 * @param port Receives the matching port index (0 input, 1 output) when true is returned.
 * @return True when a port is within range, false otherwise.
 */
bool GraphWidget::hit_port(int left, int top, size_t &node, size_t &port) const
{
    for (size_t i = count_; i > 0U; --i)
        for (size_t p = 0U; p < 2U; ++p) {
            int px, py;
            if (port_position(positions_[i - 1U].id, p, px, py) && std::abs(px - left) <= 9 &&
                std::abs(py - top) <= 9) {
                node = positions_[i - 1U].id;
                port = p;
                return true;
            }
        }
    return false;
}

/**
 * @brief Draws the background, wires, nodes, ports, and any pending wire.
 */
void GraphWidget::draw()
{
    fl_push_clip(x(), y(), w(), h());
    fl_color(fl_rgb_color(25, 28, 33));
    fl_rectf(x(), y(), w(), h());
    size_t nodes = 0U, edges = 0U;
    (void)xtc_graph_get_counts(graph_, &nodes, &edges);
    for (size_t i = 0U; i < edges; ++i) {
        xtc_connection_info edge{};
        int sx, sy, dx, dy;
        if (xtc_graph_get_connection(graph_, i, &edge) != XTC_OK || !port_position(edge.source_node, 1U, sx, sy) ||
            !port_position(edge.destination_node, 0U, dx, dy))
            continue;
        bool selected = (edge_selected_ && selected_edge_.source_node == edge.source_node &&
                         selected_edge_.destination_node == edge.destination_node) ||
                        selected_node_ == edge.source_node || selected_node_ == edge.destination_node;
        xtc_routing_info route{};
        bool audible_path = routing(edge.destination_node, route) && route.reaches_output;
        fl_color(selected ? FL_YELLOW : audible_path ? fl_rgb_color(100, 200, 190) : fl_rgb_color(110, 115, 125));
        fl_line_style(FL_SOLID, selected ? 3 : 2);
        fl_line(x() + sx, y() + sy, x() + dx, y() + dy);
        double length = std::hypot(dx-sx, dy-sy);
        if (length > 20) {
            double ux = (dx-sx)/length, uy = (dy-sy)/length;
            int ax = x() + (sx+dx)/2, ay = y() + (sy+dy)/2;
            fl_line(ax, ay, ax-static_cast<int>(ux*9-uy*5), ay-static_cast<int>(uy*9+ux*5));
            fl_line(ax, ay, ax-static_cast<int>(ux*9+uy*5), ay-static_cast<int>(uy*9-ux*5));
        }
    }
    fl_line_style(0);
    for (size_t i = 0U; i < count_; ++i) {
        xtc_node_info node{};
        if (xtc_graph_get_node(graph_, i, &node) != XTC_OK)
            continue;
        int left = x() + positions_[i].left, top = y() + positions_[i].top;
        fl_color(node.type == XTC_NODE_OUTPUT ? fl_rgb_color(100, 50, 55)
                 : node.type == XTC_NODE_GAIN ? fl_rgb_color(75, 55, 95)
                 : node.type == XTC_NODE_OSCILLATOR || node.type == XTC_NODE_AUDIO || node.type == XTC_NODE_INSTRUMENT
                     ? fl_rgb_color(35, 80, 75) : fl_rgb_color(49, 65, 85));
        fl_rectf(left, top, node_width, node_height);
        fl_color(selected_node_ == node.id ? FL_YELLOW : fl_rgb_color(115, 130, 145));
        fl_rect(left, top, node_width, node_height);
        fl_color(FL_WHITE);
        fl_font(FL_HELVETICA_BOLD, 12);
        char text[96];
        std::snprintf(text, sizeof(text), "%s #%zu", node_name(node.type), node.id);
        fl_push_clip(left+6, top+2, node_width-12, 40);
        fl_draw(text, left + 10, top + 20);
        fl_font(FL_HELVETICA, 12);
        if (node.type == XTC_NODE_OSCILLATOR)
            std::snprintf(text, sizeof(text), "%.0f Hz", static_cast<double>(node.value));
        else if (node.type == XTC_NODE_GAIN)
            std::snprintf(text, sizeof(text), "x %.2f", static_cast<double>(node.value));
        else if (node.type == XTC_NODE_PLUGIN) {
            xtc_plugin_spec plugin{};
            if (xtc_graph_get_plugin(graph_,node.id,&plugin) == XTC_OK)
                std::snprintf(text,sizeof(text),"%.20s",plugin.label);
        } else
            std::snprintf(text, sizeof(text), "%s",
                          node.type == XTC_NODE_METER        ? "Peak pass-through"
                          : node.type == XTC_NODE_INSTRUMENT ? "MIDI sine source"
                          : node.type == XTC_NODE_AUDIO      ? "Timeline mix source"
                                                             : "Summed engine output");
        fl_draw(text, left + 10, top + 37);
        fl_pop_clip();
        xtc_routing_info route{};
        if (routing(node.id, route) && !route.reaches_output) {
            fl_color(FL_YELLOW);
            fl_draw("! no output path", left + 10, top + 72);
        }
        for (size_t port = 0U; port < 2U; ++port) {
            int px, py;
            if (!port_position(node.id, port, px, py))
                continue;
            fl_color(fl_rgb_color(110, 220, 185));
            fl_pie(x() + px - 5, y() + py - 5, 10, 10, 0, 360);
            fl_color(FL_WHITE);
            fl_draw(port == 0U ? (route.external_input ? "ext in" : "sum in") : "audio out", left + (port == 0U ? 10 : 90), top + 56);
        }
    }
    if (wiring_) {
        int px, py;
        if (port_position(wire_node_, wire_port_, px, py)) {
            fl_color(FL_YELLOW);
            fl_line(x() + px, y() + py, x() + mouse_x_, y() + mouse_y_);
        }
    }
    fl_pop_clip();
}

/**
 * @brief Handles mouse and keyboard events for selection, dragging, and wiring.
 *
 * @param event FLTK event code.
 * @return 1 when the event was consumed, 0 for unsupported left-button input,
 *         or the result of Fl_Widget::handle() for unhandled events.
 */
int GraphWidget::handle(int event)
{
    const int left = Fl::event_x() - x(), top = Fl::event_y() - y();
    switch (event) {
    case FL_FOCUS:
    case FL_UNFOCUS:
        return 1;
    case FL_PUSH: {
        if (Fl::event_button() == FL_RIGHT_MOUSE) {
            Fl_Menu_Item items[5]{};
            items[0].text = "Inspect selection";
            items[1].text = "Arrange by signal flow (L)";
            items[2].text = "Insert unity gain in selected wire (I)";
            items[3].text = "Delete selection";
            const auto *picked = items->popup(Fl::event_x(), Fl::event_y());
            if (picked == items) describe_selection();
            else if (picked == items+1) auto_layout();
            else if (picked == items+2) insert_gain();
            else if (picked == items+3) delete_selected();
            return 1;
        }
        if (Fl::event_button() != FL_LEFT_MOUSE) return 0;
        take_focus();
        mouse_x_ = left;
        mouse_y_ = top;
        dragging_ = false;
        wiring_ = false;
        if (hit_port(left, top, wire_node_, wire_port_)) {
            wiring_ = true;
            redraw();
            return 1;
        }
        for (size_t i = count_; i > 0U; --i) {
            const Position &pos = positions_[i - 1U];
            if (left >= pos.left && left <= pos.left + node_width && top >= pos.top && top <= pos.top + node_height) {
                select_node(pos.id);
                dragging_ = true;
                drag_x_ = left - pos.left;
                drag_y_ = top - pos.top;
                return 1;
            }
        }
        size_t nodes, edges;
        (void)xtc_graph_get_counts(graph_, &nodes, &edges);
        for (size_t i = 0U; i < edges; ++i) {
            xtc_connection_info edge{};
            int sx, sy, dx, dy;
            (void)xtc_graph_get_connection(graph_, i, &edge);
            if (!port_position(edge.source_node, 1U, sx, sy) || !port_position(edge.destination_node, 0U, dx, dy))
                continue;
            double vx = dx - sx, vy = dy - sy;
            double length = vx * vx + vy * vy;
            double t =
                length == 0.0 ? 0.0 : std::max(0.0, std::min(1.0, ((left - sx) * vx + (top - sy) * vy) / length));
            if (std::hypot(left - sx - t * vx, top - sy - t * vy) <= 6.0) {
                select_connection(edge.source_node, edge.destination_node);
                return 1;
            }
        }
        selected_node_ = SIZE_MAX;
        edge_selected_ = false;
        redraw();
        return 1;
    }
    case FL_DRAG:
        mouse_x_ = left;
        mouse_y_ = top;
        if (dragging_)
            move_node(selected_node_, left - drag_x_, top - drag_y_);
        if (wiring_)
            redraw();
        return 1;
    case FL_RELEASE:
        dragging_ = false;
        if (wiring_) {
            size_t node, port;
            wiring_ = false;
            if (hit_port(left, top, node, port))
                connect_ports({wire_node_, wire_port_, node, port});
            else
                feedback_->copy_label("Connection cancelled. Drag an output port to an input port.");
            redraw();
        }
        return 1;
    case FL_KEYDOWN:
        if (Fl::event_key() == 'l' && !Fl::event_state(FL_CTRL | FL_ALT)) { auto_layout(); return 1; }
        if (Fl::event_key() == 'i' && !Fl::event_state(FL_CTRL | FL_ALT)) { insert_gain(); return 1; }
        if ((Fl::event_key() == FL_Left || Fl::event_key() == FL_Right) && count_) {
            size_t selected = 0;
            for (size_t i = 0; i < count_; ++i) if (positions_[i].id == selected_node_) {
                selected = Fl::event_key() == FL_Left ? (i+count_-1)%count_ : (i+1)%count_; break;
            }
            select_node(positions_[selected].id);
            return 1;
        }
        if (Fl::event_key() == FL_Delete || Fl::event_key() == FL_BackSpace) {
            delete_selected();
            return 1;
        }
        if (Fl::event_key() == FL_Escape) {
            wiring_ = dragging_ = false;
            redraw();
            return 1;
        }
        break;
    default:
        break;
    }
    return Fl_Widget::handle(event);
}

bool GraphWidget::routing(size_t id, xtc_routing_info &info) const
{
    for (size_t i = 0; i < routing_count_; ++i) if (routing_[i].id == id) { info = routing_[i]; return true; }
    return false;
}

void GraphWidget::grow_canvas()
{
    int width = 2000, height = 4000;
    for (size_t i = 0; i < count_; ++i) {
        width = std::max(width, positions_[i].left + node_width + 40);
        height = std::max(height, positions_[i].top + node_height + 40);
    }
    size(width, height);
    if (parent()) parent()->redraw();
}

bool GraphWidget::auto_layout()
{
    if (routing_count_ != count_) return false;
    std::array<size_t, 256> rows{};
    for (size_t i = 0; i < count_; ++i) {
        xtc_routing_info info{};
        if (!routing(positions_[i].id, info) || info.level >= rows.size()) return false;
        positions_[i].left = 40 + static_cast<int>(info.level) * 210;
        positions_[i].top = 40 + static_cast<int>(rows[info.level]++) * 115;
    }
    wiring_ = dragging_ = false;
    grow_canvas();
    feedback_->copy_label("Arranged left to right by signal flow. Layout is session-only; no audio or routing changes.");
    redraw();
    return true;
}

xtc_result GraphWidget::insert_gain()
{
    if (!edge_selected_) {
        feedback_->copy_label("Select a wire first, then insert a unity gain/bus node.");
        return XTC_ERR_INVALID_STATE;
    }
    xtc_graph_edit edit{};
    edit.kind = XTC_EDIT_INSERT_GAIN;
    edit.data.connection = selected_edge_;
    size_t added = SIZE_MAX;
    xtc_result result = handler_(context_, edit, &added);
    if (result == XTC_OK) select_node(added);
    feedback(result, "Unity gain inserted into wire as one edit. Inputs sum; fan-out copies the signal without normalization.");
    return result;
}

void GraphWidget::describe_selection()
{
    char text[320];
    if (edge_selected_) {
        std::snprintf(text, sizeof(text), "Wire: #%zu audio out -> #%zu sum in. Delete disconnects; I inserts a unity gain. Destination sums its inputs.",
                      selected_edge_.source_node, selected_edge_.destination_node);
    } else {
        xtc_routing_info info{};
        if (!routing(selected_node_, info)) { feedback_->copy_label("Select a node or wire to inspect routing."); return; }
        std::snprintf(text, sizeof(text), "Node #%zu: %zu incoming, %zu outgoing | %s | %s. Ports are audio lanes; stereo uses paired independent processing.",
                      info.id, info.inputs, info.outputs,
                      info.reaches_output ? "path to engine output" : "NO output path",
                      info.external_input ? "unwired input uses external audio" : "wired sum or source");
    }
    feedback_->copy_label(text);
}