From a8c9f29787372b15c1f4c0072393399b468bbce1 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Mon, 7 Oct 2019 12:35:05 +0200
Subject: [PATCH] LOLWUT: version 6 initial concept.

---
 src/lolwut5.c |  4 +--
 src/lolwut6.c | 96 +++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 95 insertions(+), 5 deletions(-)

diff --git a/src/lolwut5.c b/src/lolwut5.c
index 4e9828145..0200fece6 100644
--- a/src/lolwut5.c
+++ b/src/lolwut5.c
@@ -106,7 +106,7 @@ lwCanvas *lwDrawSchotter(int console_cols, int squares_per_row, int squares_per_
  * logical canvas. The actual returned string will require a terminal that is
  * width/2 large and height/4 tall in order to hold the whole image without
  * overflowing or scrolling, since each Barille character is 2x4. */
-sds lwRenderCanvas(lwCanvas *canvas) {
+static sds renderCanvas(lwCanvas *canvas) {
     sds text = sdsempty();
     for (int y = 0; y < canvas->height; y += 4) {
         for (int x = 0; x < canvas->width; x += 2) {
@@ -166,7 +166,7 @@ void lolwut5Command(client *c) {
 
     /* Generate some computer art and reply. */
     lwCanvas *canvas = lwDrawSchotter(cols,squares_per_row,squares_per_col);
-    sds rendered = lwRenderCanvas(canvas);
+    sds rendered = renderCanvas(canvas);
     rendered = sdscat(rendered,
         "\nGeorg Nees - schotter, plotter on paper, 1968. Redis ver. ");
     rendered = sdscat(rendered,REDIS_VERSION);
diff --git a/src/lolwut6.c b/src/lolwut6.c
index 68f09036a..8cc8d6e04 100644
--- a/src/lolwut6.c
+++ b/src/lolwut6.c
@@ -36,6 +36,94 @@
 #include "server.h"
 #include "lolwut.h"
 
+/* Render the canvas using the four gray levels of the standard color
+ * terminal: they match very well to the grayscale display of the gameboy. */
+static sds renderCanvas(lwCanvas *canvas) {
+    sds text = sdsempty();
+    for (int y = 0; y < canvas->height; y++) {
+        for (int x = 0; x < canvas->width; x++) {
+            int color = lwGetPixel(canvas,x,y);
+            char *ce; /* Color escape sequence. */
+
+            /* Note that we set both the foreground and background color.
+             * This way we are able to get a more consistent result among
+             * different terminals implementations. */
+            switch(color) {
+            case 0: ce = "0;30;40m"; break;    /* Black */
+            case 1: ce = "0;90;100m"; break;   /* Gray 1 */
+            case 2: ce = "0;37;47m"; break;    /* Gray 2 */
+            case 3: ce = "0;97;107m"; break;   /* White */
+            }
+            text = sdscatprintf(text,"\033[%s \033[0m",ce);
+        }
+        if (y != canvas->height-1) text = sdscatlen(text,"\n",1);
+    }
+    return text;
+}
+
+/* Draw a skyscraper on the canvas, according to the parameters in the
+ * 'skyscraper' structure. Window colors are random and are always selected
+ * to be different than the color of the skyscraper itsefl. */
+struct skyscraper {
+    int xoff;       /* X offset. */
+    int width;      /* Pixels width. */
+    int height;     /* Pixels height. */
+    int windows;    /* Draw windows if true. */
+    int color;      /* Color of the skyscraper. */
+};
+
+void generateSkyscraper(lwCanvas *canvas, struct skyscraper *si) {
+    int starty = canvas->height-1;
+    int endy = starty - si->height + 1;
+    for (int y = starty; y >= endy; y--) {
+        for (int x = si->xoff; x < si->xoff+si->width; x++) {
+            /* The roof is four pixels less wide. */
+            if (y == endy && (x <= si->xoff+1 || x >= si->xoff+si->width-2))
+                continue;
+            int color = si->color;
+            /* Alter the color if this is a place where we want to
+             * draw a window. We check that we are in the inner part of the
+             * skyscraper, so that windows are far from the borders. */
+            if (si->windows &&
+                x > si->xoff+1 &&
+                x < si->xoff+si->width-2 &&
+                y > endy+1 &&
+                y < starty-1)
+            {
+                /* Calculate the x,y position relative to the start of
+                 * the window area. */
+                int relx = x - (si->xoff+1);
+                int rely = y - (endy+1);
+
+                /* Note that we want the windows to be two pixels wide
+                 * but just one pixel tall, because terminal "pixels"
+                 * (characters) are not square. */
+                if (relx/2 % 2 && rely % 2) {
+                    do {
+                        color = rand() % 4;
+                    } while (color == si->color);
+                    /* Except we want adjacent pixels creating the same
+                     * window to be the same color. */
+                    if (relx % 2) color = lwGetPixel(canvas,x-1,y);
+                }
+            }
+            lwDrawPixel(canvas,x,y,color);
+        }
+    }
+}
+
+/* Generate a skyline inspired by the parallax backgrounds of 8 bit games. */
+void generateSkyline(lwCanvas *canvas) {
+    struct skyscraper si = {
+        .xoff = 4,
+        .width = 13,
+        .height = 15,
+        .windows = 1,
+        .color = 1
+    };
+    generateSkyscraper(canvas, &si);
+}
+
 /* The LOLWUT 6 command:
  *
  * LOLWUT [columns] [rows]
@@ -45,7 +133,7 @@
  */
 void lolwut6Command(client *c) {
     long cols = 80;
-    long rows = 40;
+    long rows = 20;
 
     /* Parse the optional arguments if any. */
     if (c->argc > 1 &&
@@ -64,12 +152,14 @@ void lolwut6Command(client *c) {
     if (rows > 1000) rows = 1000;
 
     /* Generate the city skyline and reply. */
-    sds rendered = sdsempty();
+    lwCanvas *canvas = lwCreateCanvas(cols,rows);
+    generateSkyline(canvas);
+    sds rendered = renderCanvas(canvas);
     rendered = sdscat(rendered,
         "\nDedicated to the 8 bit game developers of the past. Redis ver. ");
     rendered = sdscat(rendered,REDIS_VERSION);
     rendered = sdscatlen(rendered,"\n",1);
     addReplyVerbatim(c,rendered,sdslen(rendered),"txt");
     sdsfree(rendered);
-    // lwFreeCanvas(canvas);
+    lwFreeCanvas(canvas);
 }