inital work on pong

src/subcmds/arcade/arcade.zig

@@ -2,11 +2,21 @@ const std = @import("std");
 const gpa = std.heap.page_allocator;
 
 const Conway = @import("conway.zig");
+const Pong = @import("pong.zig");
 
 const games = enum(u16) {
     @"Conways Game of Life",
+    // Pong,
 };
 
+fn run_game(game: i64, width: u32, height: u32, writer: *std.Io.Writer) !void {
+    switch (game) {
+        @intFromEnum(games.@"Conways Game of Life") => try Conway.play(width, height, writer),
+        // @intFromEnum(games.Pong) => try Pong.play(width, height, writer),
+        else => @panic("Game does not exist."),
+    }
+}
+
 fn ui(width: u32, height: u32, writer: *std.Io.Writer) !void {
     var fd = [_]std.posix.pollfd{.{
         .fd = std.posix.STDIN_FILENO,
@@ -42,7 +52,7 @@ fn ui(width: u32, height: u32, writer: *std.Io.Writer) !void {
         cursor_y = @intCast(std.math.clamp(cursor_y, 0, @typeInfo(games).@"enum".fields.len - 1));
         inline for (@typeInfo(games).@"enum".fields, 0..) |f, i| {
             try writer.print("\x1B[{};{}H", .{ // y, x
-                ((height + i) / 2) + 3,
+                ((height) / 2) + 3 + i,
                 (width - f.name.len) / 2,
             });
             try writer.print("{s} {s} \x1B[0m\n", .{
@@ -65,7 +75,7 @@ fn ui(width: u32, height: u32, writer: *std.Io.Writer) !void {
             'k' => cursor_y -= 1,
             'g' => cursor_y = 1,
             'G' => cursor_y = @intFromEnum(games.@"Conways Game of Life"),
-            ' ' => {
+            ' ', '\n' => {
                 // reset the terminal state for the game
                 try std.posix.tcsetattr(std.posix.STDIN_FILENO, std.posix.TCSA.NOW, oldios);
                 _ = try writer.write("\x1B[?25h"); // show cursor
@@ -73,10 +83,7 @@ fn ui(width: u32, height: u32, writer: *std.Io.Writer) !void {
                     // not much we can do
                 };
 
-                switch (cursor_y) {
+                try run_game(cursor_y, width, height, writer);
-                    @intFromEnum(games.@"Conways Game of Life") => try Conway.play(width, height, writer),
-                    else => @panic("Game does not exist."),
-                }
 
                 _ = try writer.write("\x1B[?25l"); // hide cursor
                 try writer.flush();

src/subcmds/arcade/pong.zig

@@ -0,0 +1,146 @@
+const Pong = @This();
+
+const std = @import("std");
+const gpa = std.heap.page_allocator;
+
+width: u64,
+height: u64,
+writer: *std.io.Writer,
+players: []Player,
+ball: Ball,
+mode: Mode,
+cps: f32,
+
+const Player = struct {
+    score: u8 = 0,
+    /// top y position
+    paddle_y: u64,
+    paddle_x: u64,
+
+    const paddle_height = 4;
+};
+const Ball = struct { x: f32, y: f32, vx: f16, vy: f16 };
+const Mode = enum{ easy, hard };
+
+pub fn init(mode: Mode, width: u64, height: u64, writer: *std.Io.Writer) !Pong {
+    std.debug.assert(width > 0);
+    std.debug.assert(height > 0);
+
+    const self: Pong = .{
+        .width = width,
+        .height = height,
+        .writer = writer,
+
+        .players = try gpa.alloc(Player, 2),
+        .mode = mode,
+        .ball = .{
+            .x = @as(f32, @floatFromInt(width)) / 2.0,
+            .y = @as(f32, @floatFromInt(height)) / 2.0,
+            .vx = 0.5,
+            .vy = 0.2,
+        },
+        .cps = switch (mode) {
+            Mode.easy => @as(f32, @floatFromInt(width)) / 1.3,
+            Mode.hard => @as(f32, @floatFromInt(width)) / 0.65,
+        },
+    };
+
+    self.players[0] = Player{
+        .paddle_y = height / 2,
+        .paddle_x = 0,
+        .score = 0,
+    };
+    self.players[1] = .{
+        .paddle_y = height / 2,
+        .paddle_x = width - 1,
+        .score = 0,
+    };
+
+    return self;
+}
+
+/// must be called self.cps times per second
+pub fn step(self: *Pong) !void {
+    const next_x = self.ball.x + 1 / self.ball.vx;
+    const next_y = self.ball.y + 1 / self.ball.vy;
+
+    if (next_y < 0 or next_y > @as(f32, @floatFromInt(self.height - 1))) self.ball.vy = -self.ball.vy;
+    for (self.players) |p| {
+        if ((@floor(next_x) == @as(f32, @floatFromInt(p.paddle_x))) and
+            (@floor(next_y) >= @as(f32, @floatFromInt(p.paddle_y)) and
+             @floor(next_y) <= @as(f32, @floatFromInt(p.paddle_y + Player.paddle_height)))) {
+            self.ball.vx = -self.ball.vx;
+
+            // The paddle is 4 high but divided into 8 sections.
+            // This is done so that we may change the vy of the ball after its
+            // hit the paddle which allows the ball to traverse an arbitrary
+            // path.
+            //
+            // I've encoded it in the struct below which allows us to generate
+            // the if branching at comptime.
+            const strong = 0.8;
+            const medium = 0.4;
+            const weak = 0.2;
+            const zero = 0;
+            const result_vy = .{
+                .{ 0.5, strong },
+                .{ 1, medium },
+                .{ 1.5, weak },
+                .{ 2, zero },
+                .{ 2.5, zero },
+                .{ 3, weak },
+                .{ 3.5, medium },
+                .{ 4, strong },
+            };
+            self.ball.vy = vy: {
+                inline for (result_vy) |f| {
+                    if (next_y <= @as(f32, @floatFromInt(p.paddle_y)) + f[0]) {
+                        break: vy f[1];
+                    }
+                }
+                unreachable; // it should be impossible to be outside of the paddle
+            };
+        } else if (@floor(next_x) == @as(f32, @floatFromInt(p.paddle_x))) {
+            // scored
+            var mult: f16 = 1;
+            if (std.meta.eql(p, self.players[0])) {
+                self.players[1].score += 1;
+                mult = -mult;
+            } else {
+                self.players[0].score += 1;
+                mult = mult;
+            }
+
+            self.ball = .{
+                .x = @as(f32, @floatFromInt(self.width)) / 2.0,
+                .y = @as(f32, @floatFromInt(self.height)) / 2.0,
+                .vx = 0.5 * mult,
+                .vy = self.ball.vy,
+            };
+        }
+    }
+
+    self.ball.x += self.ball.vx;
+    self.ball.y += self.ball.vy;
+}
+
+pub fn play(width: u32, height: u32, writer: *std.Io.Writer) !void {
+    var pong = try Pong.init(.hard, width, height, writer);
+
+    // var fd = [_]std.posix.pollfd{.{
+    //     .fd = std.posix.STDIN_FILENO,
+    //     .events = std.posix.POLL.IN,
+    //     .revents = 0
+    // }};
+
+
+
+    while (true) {
+        try pong.writer.print("\x1B[{}A", .{height});
+
+        try pong.writer.print("\x1B[{};{}H", .{pong.ball.y, pong.ball.x});
+        try pong.writer.writeAll("o");
+        try pong.writer.flush();
+        try pong.step();
+    }
+}