zig-learn/primitives.zig

const std = @import("std");
const term = @import("term.zig");
const Winsize = term.Winsize;

pub const Direction = struct {
    x: i8 = 1,
    y: i8 = 1,
    z: i8 = 1,
};
pub const Point = struct {
    x: i32 = 0,
    y: i32 = 0,
    z: i32 = 0,
    direction: Direction = .{ .x = 1, .y = 1, .z = 1 }, //for movement state
};
pub const Vec3 = struct {
    a: Point = .{ .x = 0, .y = 0, .z = 0, .direction = .{ .x = 0, .y = 0, .z = 0 } },
    b: Point = .{ .x = 0, .y = 0, .z = 0, .direction = .{ .x = 0, .y = 0, .z = 0 } },
    c: Point = .{ .x = 0, .y = 0, .z = 0, .direction = .{ .x = 0, .y = 0, .z = 0 } },
};
pub const Triangle = struct {
    bufa: *i32,
    bufb: *i32,
    bufc: *i32,
};

pub fn LinkedList() type {
    return struct {
        const Self = @This(); //means this struc,ref to the most inner scope

        const Node = struct { point: Point, next: ?*Node };
        head: ?*Node,
        length: u32,

        pub fn new() Self {
            return .{
                .head = null,
                .length = 0,
            };
        }
        pub fn add(self: *Self, allocator: std.mem.Allocator, point: Point) void {
            var newNode = allocator.create(Node) catch |err| {
                std.debug.print("error allocation, {}", .{err});
                return;
            };

            newNode.point = point;
            newNode.next = self.head;

            self.head = newNode;
            self.length += 1;
        }
        pub fn dump(self: *Self) ![]Point {
            const allocator = std.heap.page_allocator;
            var node = self.head;
            var point: []Point = &.{}; //empty slice
            var i: usize = 0;

            while (node != null) : (i += 1) {
                point = allocator.realloc(point, i + 1) catch |err| {
                    std.debug.print("error allocation for slice:{}\n", .{err});
                    return err;
                };
                point[i] = node.?.point;
                node = node.?.next;
            }
            //TODO: free memory but how to?, when out of scope or dont use slices? or copy them, or outsource allocation?
            return point;
        }
    };
}
test "test linked list" {
    var polygon = LinkedList().new();
    polygon.add(std.heap.page_allocator, .{ .x = 10, .y = 11, .z = 0 });
    polygon.add(std.heap.page_allocator, .{ .x = 11, .y = 12, .z = 0 });
    polygon.add(std.heap.page_allocator, .{ .x = 12, .y = 13, .z = 0 });
    polygon.add(std.heap.page_allocator, .{ .x = 12, .y = 14, .z = 0 });
    polygon.add(std.heap.page_allocator, .{ .x = 12, .y = 15, .z = 0 });
    polygon.add(std.heap.page_allocator, .{ .x = 12, .y = 16, .z = 0 });
    const points: []Point = try polygon.dump();
    for (points) |point| {
        std.debug.print("x:{}\n", .{point.x});
        std.debug.print("y:{}\n", .{point.y});
        std.debug.print("z:{}\n", .{point.z});
    }
    std.heap.page_allocator.free(points);
}

pub fn pixel(buffer: []u8, w: Winsize, x: i64, y: i64, symbol: u21) !void {
    const i: usize = @intCast(4 * (x + y * w.ws_col));
    if (i < buffer.len) { //-1 ??
        const slice = buffer[i .. i + 4];
        _ = try std.unicode.utf8Encode(symbol, slice);
        //TODO: check length, set not used bytes to zero
    } else {
        //print("Error illegal memory access\n", .{});
    }
}
pub fn bresenham(buf: []u8, w: Winsize, p1: Point, p2: Point) !void {
    var x: i32 = p1.x;
    var y: i32 = p1.y;
    const dx = (p2.x - p1.x);
    const dy = (p2.y - p1.y);
    var er: i64 = 0;
    if (dx >= dy and dy > 0 and dx > 0) {
        while (x <= p2.x) : (x += 1) {
            _ = try pixel(buf, w, x, y, '█');
            er += dy;
            if (2 * er >= dx) {
                y += 1;
                er -= dx;
            }
        }
    } else if (dx <= dy and dy >= 0 and dx >= 0) {
        while (y <= p2.y) : (y += 1) {
            _ = try pixel(buf, w, x, y, '█');
            er += dx;
            if (2 * er >= dy) {
                x += 1;
                er -= dy;
            }
        }
    } else if (@abs(dy) <= dx and dy <= 0 and dx >= 0) {
        while (x <= p2.x) : (x += 1) {
            _ = try pixel(buf, w, x, y, '█');
            er -= dy;
            if (2 * er >= dx) {
                y -= 1;
                er -= dx;
            }
        }
    } else if (@abs(dy) >= dx and dy <= 0 and dx >= 0) {
        while (y >= p2.y) : (y -= 1) {
            _ = try pixel(buf, w, x, y, '█');
            er += dx;
            if (2 * er >= dy) {
                x += 1;
                er += dy;
            }
        }
    } else if (@abs(dx) <= dy and dx <= 0 and dy >= 0) {
        while (y <= p2.y) : (y += 1) {
            _ = try pixel(buf, w, x, y, '█');
            er += @abs(dx);
            if (2 * er >= dy) {
                x -= 1;
                er -= dy;
            }
        }
    } else if (@abs(dx) >= dy and dy >= 0 and dx <= 0) {
        while (x >= p2.x) : (x -= 1) {
            _ = try pixel(buf, w, x, y, '█');
            er += dy;
            if (2 * er >= @abs(dx)) {
                y += 1;
                er -= @abs(dx);
            }
        }
    } else if (dx <= dy and dx <= 0 and dy <= 0) {
        while (x >= p2.x) : (x -= 1) {
            _ = try pixel(buf, w, x, y, '█');
            er += @abs(dy);
            if (2 * er >= @abs(dx)) {
                y -= 1;
                er -= @abs(dx);
            }
        }
    } else if (dx >= dy and dy <= 0 and dx <= 0) {
        while (y >= p2.y) : (y -= 1) {
            //print("x:{},y:{},er:{},dx:{},dy:{}\n", .{ x, y, er, dx, dy });
            _ = try pixel(buf, w, x, y, '█');
            er += @abs(dx);
            if (2 * er >= @abs(dx)) {
                x -= 1;
                er -= @abs(dy);
            }
        }
    }
}
pub fn triangle(buffer: []u8, w: Winsize, vector: Vec3) !void {
    try bresenham(buffer, w, vector.a, vector.b);
    try bresenham(buffer, w, vector.b, vector.c);
    try bresenham(buffer, w, vector.c, vector.a);
}