void fill_cell        (btk_cell_t *, cairo_t *, btk_rgb_t);
void guard_scroll     (int *, int, int, unsigned int, int);
void render_button    (btk_cell_t *, cairo_t *);
void render_editor    (btk_cell_t *);
void render_gauge     (btk_cell_t *, cairo_t *);
void render_input     (btk_cell_t *, cairo_t *);
void render_list      (btk_cell_t *);
void render_mark      (btk_cell_t *, cairo_t *);
void render_prompt    (btk_cell_t *, cairo_t *);
void render_table     (btk_cell_t *);
void render_table_row (btk_cell_t *, char *, int, btk_rgb_t, btk_rgb_t);
void render_text      (btk_cell_t *);
void render_switch    (btk_cell_t *, cairo_t *);
void render_wheel     (btk_cell_t *, cairo_t *);
void reset_field      (btk_cell_t *);
void write_label      (cairo_t *, int, int, unsigned int, int, char *, btk_rgb_t);

static cairo_font_options_t *font_opt;
static btk_pos_t             label_offset;
static btk_size_t            glyph;

/* ch is a modifier to force the heigth of a rendered cell to 1 cell unit */
void
fill_cell(btk_cell_t *c, cairo_t *c_ctx, btk_rgb_t cl)
{
	cairo_set_source_rgb(c_ctx, cl.r, cl.g, cl.b);
	cairo_rectangle(c_ctx, c->pa.x, c->pa.y, c->pa.w, c->pa.h);
	cairo_fill(c_ctx);
}

/* pi = pixel indent, of each scrollable element in the considered axis */
/* cl = cell length, in the considered axis */
void
guard_scroll(int *scroll_var, int pi, int cl, unsigned int items_n, int extra)
{
	if (*scroll_var < 0 || !items_n) { /* no negative scroll position */
		*scroll_var = 0;
	} else if (cl >= pi * items_n + extra) { /* reset scroll pos if everything fits in */
		*scroll_var = 0;
	} else if (*scroll_var + cl > pi * items_n + extra) {
		*scroll_var = pi * items_n - cl + extra;
	}
}

void
render_button(btk_cell_t *c, cairo_t *c_ctx)
{
	btk_rgb_t clt, cl;
	if ((c->state & BTK_CELL_STATE_DISABLED)) {
		cl  = btk_cl_dyn_disabled;
		clt = btk_cl_text_disabled;
	} else if ((c->state & BTK_CELL_STATE_PRESSED)) {
		cl  = btk_cl_dyn_pressed;
		clt = btk_cl_text_hilight;
	} else {
		cl  = btk_cl_dyn_idle;
		clt = btk_cl_text_normal;
	}

	fill_cell(c, c_ctx, cl);
	write_label(c_ctx, c->pa.x, c->pa.y, c->pa.w, BTK_JUSTIFY_LEFT, c->label, clt);
}

void
render_editor(btk_cell_t *c)
{
	btk_pp_editor_t *pp = PP_EDITOR(c);

	cairo_set_source_rgb(c->fd->c_ctx, btk_cl_field.r, btk_cl_field.g, btk_cl_field.b);
	cairo_paint(c->fd->c_ctx);

	int text_n = 0;
	if (*pp->text)
		text_n = strlen(pp->text);

	guard_scroll(&pp->scroll, glyph.h + btk_text_spacing, c->pa.h, pp->par->rows_n, label_offset.y);

	/* render caret */
	if (!(c->state & BTK_CELL_STATE_DISABLED)) {
		cairo_set_source_rgb(c->fd->c_ctx,
		                     btk_cl_bell.r,
		                     btk_cl_bell.g,
		                     btk_cl_bell.b);
		cairo_move_to(c->fd->c_ctx,
		              label_offset.x + pp->caret_2d.x * glyph.w,
		              pp->caret_2d.y * (glyph.h + btk_text_spacing) +
					  	btk_caret_offset + label_offset.y - pp->scroll);
		cairo_show_text(c->fd->c_ctx, "_");
	}

	/* just render label if there are no rows to draw */
	if (!text_n || !pp->par) {
		write_label(c->fd->c_ctx,
		            0,
		            0,
		            c->pa.w,
		            BTK_JUSTIFY_LEFT,
		            c->label,
		            btk_cl_text_lolight);
		return;
	}

	btk_rgb_t cl;
	/* else render row by row */
	for (int i = 0; i < pp->par->rows_n; i++) {
		cl = btk_cl[pp->par->rows_spot[i]];
		cairo_set_source_rgb(c->fd->c_ctx, cl.r, cl.g, cl.b);
		cairo_move_to(c->fd->c_ctx,
		              label_offset.x,
		              label_offset.y - pp->scroll + i * (glyph.h + btk_text_spacing));
		cairo_show_text(c->fd->c_ctx, pp->par->rows + i * pp->par->rows_max_w);
	}
}

void
render_input(btk_cell_t *c, cairo_t *c_ctx)
{
	btk_pp_input_t *pp = PP_INPUT(c);
	int text_n = strlen(pp->text);
	btk_rgb_t clt, clt2;

	/* passive components */
	clt = (c->state & BTK_CELL_STATE_DISABLED) ? btk_cl_dyn_disabled : btk_cl_pass_on;
	fill_cell(c, c_ctx, btk_cl_field);
	cairo_set_source_rgb(c_ctx, clt.r, clt.g, clt.b);
	cairo_move_to(c_ctx, c->pa.x + label_offset.x, c->pa.y + label_offset.y);
	cairo_show_text(c_ctx, "►");

	/* limits */
	int max_n = (c->pa.w - 3 * label_offset.x ) / glyph.w - 1;
	if (pp->caret > pp->scroll + max_n - 1)
		pp->scroll = pp->caret - max_n + 1;
	if (pp->caret < pp->scroll)
		pp->scroll = pp->caret;
	if (text_n > max_n && pp->scroll + max_n > text_n)
		pp->scroll -= pp->scroll + max_n - text_n;

	/* render caret */
	if (!(c->state & BTK_CELL_STATE_DISABLED)) {
		cairo_set_source_rgb(c_ctx, btk_cl_bell.r, btk_cl_bell.g, btk_cl_bell.b);
		cairo_move_to(c_ctx,
		              c->pa.x + 2 * label_offset.x + (1 + pp->caret - pp->scroll) * glyph.w,
		              c->pa.y + label_offset.y + btk_caret_offset);
		cairo_show_text(c_ctx, "_");
	}

	/* prepare text to render */
	char cut_text[max_n + 1];
	if (text_n) {
		strncpy(cut_text, pp->text + pp->scroll, max_n);
		cut_text[max_n] = '\0';
		clt2 = btk_cl_text_disabled;
	} else {
		strcpy(cut_text, c->label);
		clt2 = btk_cl_text_lolight;
	}

	/* render text */
	cairo_set_source_rgb(c_ctx, clt2.r, clt2.g, clt2.b);
	cairo_move_to(c_ctx,
	              c->pa.x + 2 * label_offset.x + glyph.w,
	              c->pa.y + label_offset.y);
	cairo_show_text(c_ctx, cut_text);
}

void
render_list(btk_cell_t *c)
{
	reset_field(c);
	guard_scroll(&(PP_LIST(c)->scroll),
	             btk_cp.h + btk_frame,
	             c->pa.h,
	             *(PP_LIST(c)->items_n),
	             0);

	/* compute item range to render */
	int item_min = PP_LIST(c)->scroll / (btk_cp.h + btk_frame);
	int item_max = (PP_LIST(c)->scroll + c->pa.h) / (btk_cp.h + btk_frame) + 1;
	item_max = BTK_MIN(item_max, *(PP_LIST(c)->items_n));

	/* just render label if there are no rows to draw */
	if (!*(PP_LIST(c)->items_n)) {
		write_label(c->fd->c_ctx,
		            0,
		            0,
		            c->pa.w,
		            BTK_JUSTIFY_LEFT,
		            c->label,
		            btk_cl_text_lolight);
		return;
	}

	/* render sub cells */
	btk_rgb_t cl, clt;
	int row_pos;
	for (int i = item_min; i < item_max; i++) {
		if (i == PP_LIST(c)->item_sel) {
			if ((c->state & BTK_CELL_STATE_PRESSED)) {
				cl  = btk_cl_dyn_pressed;
				clt = btk_cl_text_hilight;
			} else {
				clt = btk_cl_text_select;
				cl  = btk_cl_select;
			}
		} else {
			cl = btk_cl_field;
			clt = btk_cl_text_disabled;
			if (PP_LIST(c)->spot)
				clt = btk_cl[*(*(PP_LIST(c)->spot) + i)];
		}
		row_pos = (btk_cp.h + btk_frame) * i - PP_LIST(c)->scroll;
		cairo_set_source_rgb(c->fd->c_ctx, cl.r, cl.g, cl.b);
		cairo_rectangle(c->fd->c_ctx, 0, row_pos, c->pa.w, btk_cp.h);
		cairo_fill(c->fd->c_ctx);
		write_label(c->fd->c_ctx,
		            0,
		            row_pos,
		            c->pa.w,
		            BTK_JUSTIFY_LEFT,
		            *(PP_LIST(c)->items) + i * PP_LIST(c)->items_w,
		            clt);
	}
}

void
render_mark(btk_cell_t *c, cairo_t *c_ctx)
{
	fill_cell(c, c_ctx, btk_cl_pass_off);

	btk_rgb_t clt, cl = {0.0f, 0.0f, 0.0f};
	if ((c->state & BTK_CELL_STATE_BELL)) {
		cl  = btk_cl_bell;
		clt = btk_cl_text_bell;
	} else if ((c->state & BTK_CELL_STATE_ON)) {
		cl  = btk_cl_pass_on;
		clt = btk_cl_text_hilight;
	} else {
		clt = c->state & BTK_CELL_STATE_DISABLED ?
			btk_cl_text_disabled : btk_cl_text_normal;
	}

	if ((c->state & (BTK_CELL_STATE_BELL | BTK_CELL_STATE_ON))) {
		cairo_set_source_rgb(c_ctx, cl.r, cl.g, cl.b);
		cairo_rectangle(c_ctx,
		                c->pa.x + btk_frame,
		                c->pa.y + btk_frame,
		                c->pa.w - 2 * btk_frame,
		                c->pa.h - 2 * btk_frame);
		cairo_fill(c_ctx);
	}

	write_label(c_ctx, c->pa.x, c->pa.y, c->pa.w, PP_MARK(c)->justify, c->label, clt);
}

void
render_switch(btk_cell_t *c, cairo_t *c_ctx)
{
	btk_rgb_t clt, cl;
	if ((c->state & BTK_CELL_STATE_DISABLED)) {
		cl  = btk_cl_dyn_disabled;
		clt = btk_cl_text_disabled;
	} else if ((c->state & BTK_CELL_STATE_PRESSED)) {
		cl  = btk_cl_dyn_pressed;
		clt = btk_cl_text_hilight;
	} else {
		cl  = btk_cl_dyn_idle;
		clt = btk_cl_text_normal;
	}

	fill_cell(c, c_ctx, cl);
	write_label(c_ctx,
	            c->pa.x,
	            c->pa.y,
	            c->pa.w - btk_cp.h,
	            BTK_JUSTIFY_LEFT,
	            c->label,
	            clt);

	/* state indicator */
	cl = (c->state & BTK_CELL_STATE_ON) ? btk_cl_pass_on : btk_cl_pass_off;
	cairo_set_source_rgb(c_ctx, btk_cl_frame.r, btk_cl_frame.g, btk_cl_frame.b);
	cairo_rectangle(c_ctx,
	                c->pa.x + c->pa.w - btk_cp.h + btk_padding,
					c->pa.y + btk_padding,
	                btk_cp.h - 2 * btk_padding,
					btk_cp.h - 2 * btk_padding);
	cairo_fill(c_ctx);
	cairo_set_source_rgb(c_ctx, cl.r, cl.g, cl.b);
	cairo_rectangle(c_ctx,
	                c->pa.x + c->pa.w - btk_cp.h + btk_padding + btk_frame,
					c->pa.y + btk_padding + btk_frame,
	                btk_cp.h - 2 * (btk_padding + btk_frame),
					btk_cp.h - 2 * (btk_padding + btk_frame));
	cairo_fill(c_ctx);
}

void
render_table(btk_cell_t *c)
{
	reset_field(c);
	btk_pp_table_t *pp = PP_TABLE(c);
	
	/* horizontal then vertical scroll */
	guard_scroll(&pp->scroll.x, pp->tw, c->pa.w, 1, 0);
	guard_scroll(&pp->scroll.y, btk_cp.h + btk_frame, c->pa.h, *pp->rows_n + 1, 0);

	int header_indent = pp->header ? 1 : 0; 

	/* compute item range to render */
	int item_min = pp->scroll.y / (btk_cp.h + btk_frame);
	int item_max = (pp->scroll.y + c->pa.h) / (btk_cp.h + btk_frame);
	item_max = BTK_MIN(item_max, *pp->rows_n);

	/* just render label if there are no rows to draw */
	if (!*pp->rows_n) {
		write_label(c->fd->c_ctx,
		            0,
		            header_indent * (btk_cp.h + btk_frame),
		            c->pa.w,
		            BTK_JUSTIFY_LEFT,
		            c->label,
		            btk_cl_text_lolight);
		goto header;
	}

	/* render rows */
	btk_rgb_t cl, clt;
	int row_pos;
	for (int i = item_min; i < item_max; i++) {
		if (i == pp->row_sel) {
			if ((c->state & BTK_CELL_STATE_PRESSED)) {
				cl  = btk_cl_dyn_pressed;
				clt = btk_cl_text_hilight;
			} else {
				clt = btk_cl_text_select;
				cl  = btk_cl_select;
			}
		} else {
			cl = btk_cl_field;
			clt = btk_cl_text_disabled;
			if (pp->spot)
				clt = btk_cl[*(*(PP_TABLE(c)->spot) + i)];
		}
		row_pos = (btk_cp.h + btk_frame) * (i + header_indent) - pp->scroll.y;
		render_table_row(c, btk_cell_table_get_item(c, 0, i), row_pos, cl, clt);
	}

	/* render header */
header:
	if (pp->header)
		render_table_row(c, pp->header, 0, btk_cl_pass_off, btk_cl_text_normal);
}

void
render_table_row(btk_cell_t *c,
                 char *row_data_start,
                 int row_pos,
                 btk_rgb_t cl,
                 btk_rgb_t clt)
{
	btk_pp_table_t *pp = PP_TABLE(c);
	char label[pp->items_w];
	btk_rgb_t clt2;

	for (int i = 0; i < pp->cols_n; i++) {
		cairo_set_source_rgb(c->fd->c_ctx, cl.r, cl.g, cl.b);
		cairo_rectangle(c->fd->c_ctx,
		                pp->cols_px[i] - pp->scroll.x,
		                row_pos, pp->cols_pw[i],
		                btk_cp.h);
		cairo_fill(c->fd->c_ctx);

		clt2 = clt;
		strcpy(label, row_data_start + i * pp->items_w);
		if (label[0] == '\n' || label[0] == '\0') {
			clt2 = btk_cl_text_lolight;
			strncpy(label, "-/-", pp->items_w);
		}
		write_label(c->fd->c_ctx,
		            pp->cols_px[i] - pp->scroll.x,
		            row_pos,
		            pp->cols_pw[i],
		            BTK_JUSTIFY_LEFT,
		            label,
		            clt2);
	}
}

void
reset_field(btk_cell_t *c)
{
	if (!c->fd) {
		btk_log_warning(BTK_WARNING_DRAW_NO_FIELD);
		return;
	}

	cairo_set_source_rgb(c->fd->c_ctx, btk_cl_empty.r, btk_cl_empty.g, btk_cl_empty.b);
	cairo_paint(c->fd->c_ctx);
}

void
write_label(cairo_t *c_ctx,
            int px,
            int py,
            unsigned int pw,
            int justify,
			char *label,
            btk_rgb_t clt)
{
	int n = strlen(label);
	int max_n = (pw - 2 * label_offset.x) / glyph.w;
	char cut_label[max_n];

	/* make label fit in cell if needed */
	if (n > max_n) {
		int caret;
		if (justify == BTK_JUSTIFY_LEFT) {
			caret = max_n - 3;
			strncpy(cut_label, label, max_n);
		} else {
			caret = 0;
			strncpy(cut_label, label + n - max_n, max_n);
		}
		cut_label[caret]   = '.';
		cut_label[++caret] = '.';
		cut_label[++caret] = '.';
		cut_label[max_n]   = '\0';
	}
		
	/* draw label */
	cairo_set_source_rgb(c_ctx, clt.r, clt.g, clt.b); 
	if (justify == BTK_JUSTIFY_LEFT) {
		cairo_move_to(c_ctx, px + label_offset.x, py + label_offset.y);
	} else {
		int a = n > max_n ? max_n : n;
		cairo_move_to(c_ctx, px + pw - label_offset.x - glyph.w * a, py + label_offset.y);
	}

	char *l = n > max_n ? cut_label : label;
	cairo_show_text(c_ctx, l);
}