// SPDX-FileCopyrightText: 2022 Geoffrey D. Bennett <g@b4.vu>
// SPDX-License-Identifier: GPL-3.0-or-later

#include "alsa.h"
#include "routing-lines.h"

// dotted dash when a sink is going to be removed by a drag
static const double dash_dotted[] = { 1, 10 };

// dash when dragging and not connected
static const double dash[] = { 4 };

static void choose_line_colour(
  struct routing_src *r_src,
  struct routing_snk *r_snk,
  double             *r,
  double             *g,
  double             *b
) {
  // left channels have odd numbers
  // right channels have even numbers
  int odd_src = r_src->lr_num & 1;
  int odd_snk = r_snk->elem->lr_num & 1;

  // for colouring, pair channels up
  // 0 for odd pairs, 1 for even pairs
  int src2 = ((r_src->lr_num - 1) / 2 & 1);
  int snk2 = ((r_snk->elem->lr_num - 1) / 2 & 1);

  // left -> left, black
  if (odd_src && odd_snk) {
    *r = 0;
    *g = 0;
    *b = 0;

  // right -> right, red
  } else if (!odd_src && !odd_snk) {
    *r = 1;
    *g = 0;
    *b = 0;

  // left -> right, dark green
  } else if (odd_src) {
    *r = 0;
    *g = 0.25;
    *b = 0;

  // right -> left, dark brown/olive
  } else {
    *r = 0.25;
    *g = 0.25;
    *b = 0;
  }

  // mix <-> non-mix, add blue
  if ((r_src->port_category == PC_MIX) !=
      (r_snk->port_category == PC_MIX)) {
    *b = 0.5;
  }

  // even input pairs, lighten red and green components
  if (src2) {
    *r = (*r + 1) / 2;
    *g = (*g + 1) / 2;
  }

  // even output pairs, lighten blue component
  if (snk2) {
    *b = (*b + 1) / 2;
  }
}

// draw a bezier curve given the end and control points
static void curve(
  cairo_t *cr,
  double   x1,
  double   y1,
  double   x2,
  double   y2,
  double   x3,
  double   y3,
  double   x4,
  double   y4
) {
  cairo_move_to(cr, x1, y1);
  cairo_curve_to(cr, x2, y2, x3, y3, x4, y4);
}

// given the bezier end & control points and t-value, return the
// position and tangent angle at that point
static void point_and_angle_on_bezier(
  double x1,
  double y1,
  double x2,
  double y2,
  double x3,
  double y3,
  double x4,
  double y4,
  double t,
  double *x,
  double *y,
  double *a
) {
  double t2 = t * t;
  double t3 = t2 * t;
  double ti = 1 - t;
  double ti2 = ti * ti;

  *x = x1 +
       (-x1 * 3 + t * (3 * x1 - x1 * t)) * t +
       (3 * x2 + t * (-6 * x2 + x2 * 3 * t)) * t +
       (x3 * 3 - x3 * 3 * t) * t2 +
       x4 * t3;
  *y = y1 +
       (-y1 * 3 + t * (3 * y1 - y1 * t)) * t +
       (3 * y2 + t * (-6 * y2 + y2 * 3 * t)) * t +
       (y3 * 3 - y3 * 3 * t) * t2 +
       y4 * t3;

  double dx = ti2 * (x2 - x1) +
              2 * ti * t * (x3 - x2) +
              t2 * (x4 - x3);
  double dy = ti2 * (y2 - y1) +
              2 * ti * t * (y3 - y2) +
              t2 * (y4 - y3);
  *a = atan2(dy, dx);
}

// draw an arrow in the middle of the line drawn by curve()
static void arrow(
  cairo_t *cr,
  double   x1,
  double   y1,
  double   x2,
  double   y2,
  double   x3,
  double   y3,
  double   x4,
  double   y4
) {
  // get midpoint and angle
  double mx, my, a;
  point_and_angle_on_bezier(x1, y1, x2, y2, x3, y3, x4, y4, 0.5, &mx, &my, &a);

  // calculate point of arrow
  double px = mx + cos(a) * 12;
  double py = my + sin(a) * 12;

  // calculate sides of arrow
  double s1x = mx + cos(a - M_PI_2) * 2;
  double s1y = my + sin(a - M_PI_2) * 2;
  double s2x = mx + cos(a + M_PI_2) * 2;
  double s2y = my + sin(a + M_PI_2) * 2;

  // draw triangle
  cairo_move_to(cr, px, py);
  cairo_line_to(cr, s1x, s1y);
  cairo_line_to(cr, s2x, s2y);
  cairo_close_path(cr);
}

// draw a nice curved line connecting a source at (x1, y1) and a sink
// at (x2, y2)
static void draw_connection(
  cairo_t *cr,
  double   x1,
  double   y1,
  int      src_is_mixer,
  double   x2,
  double   y2,
  int      snk_is_mixer,
  double   r,
  double   g,
  double   b,
  double   w
) {
  double x3 = x1, y3 = y1, x4 = x2, y4 = y2;

  // vertical/horizontal?
  if (src_is_mixer == snk_is_mixer) {
    double f1 = 0.3;
    double f2 = 1 - f1;

    // vertical
    if (src_is_mixer) {
      y3 = y1 * f2 + y2 * f1;
      y4 = y1 * f1 + y2 * f2;

    // horizontal
    } else {
      x3 = x1 * f2 + x2 * f1;
      x4 = x1 * f1 + x2 * f2;
    }

  // diagonal
  } else {
    // calculate a fraction f1 close to 0 when approaching 45°
    // and close to 0.5 when approaching 0°/90°
    double a = fmod((atan2(y1 - y2, x2 - x1) * 180 / M_PI) + 360, 360);
    double f1 = fabs(fmod(a, 90) - 45) / 90;
    double f2 = 1 - f1;

    // bottom to right
    if (src_is_mixer) {
      y3 = y1 * f2 + y2 * f1;
      x4 = x1 * f1 + x2 * f2;

    // left to top
    } else {
      x3 = x1 * f2 + x2 * f1;
      y4 = y1 * f1 + y2 * f2;
    }
  }

  cairo_set_source_rgb(cr, r, g, b);
  cairo_set_line_width(cr, w);
  curve(cr, x1, y1, x3, y3, x4, y4, x2, y2);
  arrow(cr, x1, y1, x3, y3, x4, y4, x2, y2);
  cairo_stroke(cr);
}

// locate the center of a widget in the parent coordinates
// used for drawing lines to/from the "socket" widget of routing
// sources and sinks
static void get_widget_center(
  GtkWidget *w,
  GtkWidget *parent,
  double    *x,
  double    *y
) {
  double src_x = gtk_widget_get_allocated_width(w) / 2;
  double src_y = gtk_widget_get_allocated_height(w) / 2;
  gtk_widget_translate_coordinates(w, parent, src_x, src_y, x, y);
}

static void get_src_center(
  struct routing_src *r_src,
  GtkWidget          *parent,
  double             *x,
  double             *y
) {
  get_widget_center(r_src->widget2, parent, x, y);
  if (r_src->port_category == PC_MIX)
    (*y)++;
}

static void get_snk_center(
  struct routing_snk *r_snk,
  GtkWidget          *parent,
  double             *x,
  double             *y
) {
  get_widget_center(r_snk->elem->widget2, parent, x, y);
  if (r_snk->port_category == PC_MIX)
    (*y)++;
}

// redraw the overlay lines between the routing sources and sinks
void draw_routing_lines(
  GtkDrawingArea *drawing_area,
  cairo_t        *cr,
  int             width,
  int             height,
  void           *user_data
) {
  struct alsa_card *card = user_data;
  GtkWidget *parent = card->routing_lines;

  cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND);

  int dragging = card->drag_type != DRAG_TYPE_NONE;

  // go through all the routing sinks
  for (int i = 0; i < card->routing_snks->len; i++) {
    struct routing_snk *r_snk = &g_array_index(
      card->routing_snks, struct routing_snk, i
    );

    // if dragging and a routing sink is being reconnected then draw
    // it with dots
    int dragging_this = dragging && card->snk_drag == r_snk;
    if (dragging_this)
      cairo_set_dash(cr, dash_dotted, 2, 0);
    else
      cairo_set_dash(cr, NULL, 0, 0);

    // get the sink and skip if it's "Off"
    int r_src_idx = alsa_get_elem_value(r_snk->elem);
    if (!r_src_idx)
      continue;

    // look up the source
    struct routing_src *r_src = &g_array_index(
      card->routing_srcs, struct routing_src, r_src_idx
    );

    // locate the source and sink coordinates
    double x1, y1, x2, y2;
    get_src_center(r_src, parent, &x1, &y1);
    get_snk_center(r_snk, parent, &x2, &y2);

    // pick a colour
    double r, g, b;
    choose_line_colour(r_src, r_snk, &r, &g, &b);

    // make the colour lighter if it's being shown dotted
    if (dragging_this) {
      r = (r + 1) / 2;
      g = (g + 1) / 2;
      b = (b + 1) / 2;
    }

    // draw the connection
    draw_connection(
      cr,
      x1, y1, r_src->port_category == PC_MIX,
      x2, y2, r_snk->port_category == PC_MIX,
      r, g, b, 2
    );
  }
}

// draw the overlay dragging line
void draw_drag_line(
  GtkDrawingArea *drawing_area,
  cairo_t        *cr,
  int             width,
  int             height,
  void           *user_data
) {
  struct alsa_card *card = user_data;
  GtkWidget *parent = card->drag_line;

  // if not dragging or routing src & snk not specified or drag out of
  // bounds then do nothing
  if (card->drag_type == DRAG_TYPE_NONE ||
      (!card->src_drag && !card->snk_drag) ||
      card->drag_x < 0 ||
      card->drag_y < 0)
    return;

  // the drag mouse position is relative to card->routing_grid
  // translate it to the overlay card->drag_line
  // (don't need to do this if both src_drag and snk_drag are set)
  double drag_x, drag_y;
  if (!card->src_drag || !card->snk_drag)
    gtk_widget_translate_coordinates(
      card->routing_grid, parent,
      card->drag_x, card->drag_y,
      &drag_x, &drag_y
    );

  // get the line start position; either a routing source socket
  // widget or the drag mouse position
  double x1, y1;
  if (card->src_drag) {
    get_src_center(card->src_drag, parent, &x1, &y1);
  } else {
    x1 = drag_x;
    y1 = drag_y;
  }

  // get the line end position; either a routing sink socket widget or
  // the drag mouse position
  double x2, y2;
  if (card->snk_drag) {
    get_snk_center(card->snk_drag, parent, &x2, &y2);
  } else {
    x2 = drag_x;
    y2 = drag_y;
  }

  // if routing src & snk both specified then draw a curved line as if
  // it was connected (except black)
  if (card->src_drag && card->snk_drag) {
    draw_connection(
      cr,
      x1, y1, card->src_drag->port_category == PC_MIX,
      x2, y2, card->snk_drag->port_category == PC_MIX,
      0, 0, 0, 2
    );

  // otherwise draw a straight line
  } else {
    cairo_set_dash(cr, dash, 1, 0);

    cairo_set_source_rgb(cr, 0, 0, 0);
    cairo_set_line_width(cr, 2);
    cairo_move_to(cr, x1, y1);
    cairo_line_to(cr, x2, y2);
    cairo_stroke(cr);
  }
}
