Implementation of car removal when infrastructure where car is located gets removed itself

build.zig

@@ -28,7 +28,7 @@ pub fn build(b: *std.Build) void {
     // to our consumers. We must give it a name because a Zig package can expose
     // multiple modules and consumers will need to be able to specify which
     // module they want to access.
-    // const mod = b.addModule("base_road_network", .{
+    // const mod = b.addModule("traffic-simulator", .{
     //     // The root source file is the "entry point" of this module. Users of
     //     // this module will only be able to access public declarations contained
     //     // in this file, which means that if you have declarations that you
@@ -68,7 +68,8 @@ pub fn build(b: *std.Build) void {
     // If neither case applies to you, feel free to delete the declaration you
     // don't need and to put everything under a single module.
     const exe = b.addExecutable(.{
-        .name = "base_road_network",
+        .name = "traffic-simulator",
+        .use_llvm = true,
         .root_module = b.createModule(.{
             // b.createModule defines a new module just like b.addModule but,
             // unlike b.addModule, it does not expose the module to consumers of
@@ -83,12 +84,12 @@ pub fn build(b: *std.Build) void {
             // List of modules available for import in source files part of the
             // root module.
             .imports = &.{
-                // Here "base_road_network" is the name you will use in your source code to
-                // import this module (e.g. `@import("base_road_network")`). The name is
+                // Here "traffic-simulator" is the name you will use in your source code to
+                // import this module (e.g. `@import("traffic-simulator")`). The name is
                 // repeated because you are allowed to rename your imports, which
                 // can be extremely useful in case of collisions (which can happen
                 // importing modules from different packages).
-                // .{ .name = "base_road_network", .module = mod },
+                // .{ .name = "traffic-simulator", .module = mod },
 
                 // Raylib import
                 .{ .name = "raylib", .module = raylib },
@@ -131,6 +132,7 @@ pub fn build(b: *std.Build) void {
     }
 
     const tests = b.addTest(.{
+        .use_llvm = true,
         .root_module = b.createModule(.{
             .root_source_file = b.path("src/test.zig"),
             .target = target,

build.zig.zon

@@ -6,7 +6,7 @@
     //
     // It is redundant to include "zig" in this name because it is already
     // within the Zig package namespace.
-    .name = .base_road_network,
+    .name = .traffic_simulator,
     // This is a [Semantic Version](https://semver.org/).
     // In a future version of Zig it will be used for package deduplication.
     .version = "0.0.0",
@@ -22,7 +22,7 @@
     // original project's identity. Thus it is recommended to leave the comment
     // on the following line intact, so that it shows up in code reviews that
     // modify the field.
-    .fingerprint = 0x8da3e26c9def0629, // Changing this has security and trust implications.
+    .fingerprint = 0xf441f200e5d3277c, // Changing this has security and trust implications.
     // Tracks the earliest Zig version that the package considers to be a
     // supported use case.
     .minimum_zig_version = "0.16.0",

src/common/constants.zig

@@ -1,9 +1,9 @@
 const clr = @import("raylib").Color;
 
 /// Screen Width
-pub const WIDTH = 1366;
+pub const WIDTH = 1920;
 /// Screen Height
-pub const HEIGHT = 768;
+pub const HEIGHT = 1080;
 pub const BACKGROUND_COLOR = clr.light_gray;
 
 /// Base node radius
@@ -24,3 +24,12 @@ pub const ROAD_SIZE = 20;
 pub const ROAD_COLOUR = clr.black;
 /// Colour of the road that is highlighted
 pub const ROAD_HIGHLIGHTED_COLOUR = clr.green;
+
+/// Regular text size
+pub const TEXT_SIZE = 50;
+/// Text size that is used for displaying entity IDs
+pub const ENTITY_DATA_TEXT_SIZE = TEXT_SIZE / 2;
+/// Text colour in which entity IDs are displayed if toggled
+pub const ENTITY_DATA_TEXT_COLOUR = clr.orange;
+
+pub const CAR_SIZE = 20;

src/common/structures.zig

@@ -2,11 +2,24 @@ const Vector2 = @import("raylib").Vector2;
 
 const Road = @import("../infrastructure/road.zig").Road;
 const Node = @import("../infrastructure/node.zig").Node;
+const Car = @import("../vehicles/car.zig").Car;
 
-/// Can point to either entity type (node, road, etc.)
+/// This is a simple equivalent to something like abstract class, so the simulator class has only one variable
+/// which tracks which object is highlighted and the logic that seeks to find the current highlighted class doesn't need
+/// to figure out which highlighted entity has priority in case of overlap;
+/// given that car can be on node and road, and node itself is on road(s)
+///
+/// TLDR: Can point to either `entity` type (node, road, etc.)
 pub const Entity = union(enum) {
     node: *Node,
     road: *Road,
+    car: *Car,
+};
+
+/// Similar to `Entity` but only for infrastructure entities, so road and node only (for now)
+pub const Infrastructure = union(enum) {
+    node: *const Node,
+    road: *const Road,
 };
 
 /// Represents intersection data, mainly used in cases where we draw over existing roads
@@ -16,4 +29,11 @@ pub const IntersectionData = struct {
     pos: Vector2,
     /// Points to the road where the intersection occured
     road: *Road,
+    /// Tracks whether this intersection is actually an origin point
+    /// (In simple terms this means whether the point/node that intersects is also the start/end node)
+    ///
+    /// We do this because the referencing logic is very strict and will return an error
+    /// if we try to reference something that is already referenced, due to stricter approach helping with
+    /// earlier bug and error detection
+    origin: bool,
 };

src/common/utils.zig

@@ -3,16 +3,13 @@ const Vector2 = @import("raylib").Vector2;
 const st = @import("structures.zig");
 const Node = @import("../infrastructure/node.zig").Node;
 
-/// Returns distance between two nodes, with the caveat that it doesn't do square root in the end;
-/// that's because we are interested in relative distance and don't care for the precise number as long as it is in
-/// correct relation to others
-///
-///  This allows us to avoid the (square) rooting operation which is computationally expensive
+/// Returns distance between two nodes, used mostly for road length and possibly for A* heuristics
 pub fn calculate_length(start: Vector2, end: Vector2) f32 {
     const x_diff = end.x - start.x;
     const y_diff = end.y - start.y;
 
-    return x_diff * x_diff + y_diff * y_diff;
+    const squared_solution = x_diff * x_diff + y_diff * y_diff;
+    return @sqrt(squared_solution);
 }
 
 /// Comparator function that compares intersection proximity from the node in order to aid the sorting function
@@ -22,3 +19,11 @@ pub fn compareIntersections(ctx: *const Node, inter_a: st.IntersectionData, inte
 
     return distance_a < distance_b;
 }
+
+/// Returns vector from P1 to P2
+pub fn getVectorP1P2(p1: Vector2, p2: Vector2) Vector2 {
+    return .{
+        .x = p2.x - p1.x,
+        .y = p2.y - p1.y,
+    };
+}

src/infrastructure/node.zig

@@ -2,7 +2,7 @@ const std = @import("std");
 const rl = @import("raylib");
 
 const c = @import("../common/constants.zig");
-const e = @import("../errors.zig");
+const e = @import("../common/errors.zig");
 const st = @import("../common/structures.zig");
 const ut = @import("../common/utils.zig");
 const Road = @import("road.zig").Road;
@@ -35,10 +35,22 @@ pub const Node = struct {
     }
 
     /// Simple function which draws the node
-    pub fn draw(self: *const Node, direct_colour: ?rl.Color) void {
+    pub fn draw(self: *const Node, direct_colour: ?rl.Color, display_info: bool) void {
         const colour = if (direct_colour) |clr| clr else c.NODE_COLOUR;
-
         rl.drawCircleV(self.pos, c.NODE_RADIUS, colour);
+
+        if (!display_info) return;
+
+        var buf: [100]u8 = undefined;
+        const entity_info = std.fmt.bufPrintZ(&buf, "{d}", .{ self.id }) catch |err| {
+            std.debug.panic("Failed to allocate space for ID???: {}\n", .{ err });
+        };
+
+        const info_x = @as(i32, @trunc(self.pos.x)) - c.NODE_RADIUS / 2;
+        const info_y = @as(i32, @trunc(self.pos.y)) - c.NODE_RADIUS / 2;
+
+        rl.drawText(entity_info, info_x, info_y,
+                c.ENTITY_DATA_TEXT_SIZE, c.ENTITY_DATA_TEXT_COLOUR);
     }
 
     /// Determines whether the pos (location) is within the snapping radius of the node
@@ -83,6 +95,15 @@ pub const Node = struct {
     pub fn getRelativeInterDistance(self: *const Node, intersection: st.IntersectionData) f32 {
         return ut.calculate_length(intersection.pos, self.pos);
     }
+
+    /// Searches for the road pointer within roads list
+    pub fn roadsContains(self: *const Node, road_to_search: *const Road) bool {
+        for (self.roads.items) |road| {
+            if (road == road_to_search) return true;
+        }
+
+        return false;
+    }
 };
 
 // TODO tests

src/infrastructure/node_manager.zig

@@ -2,7 +2,7 @@ const std = @import("std");
 const Vector2 = @import("raylib").Vector2;
 
 const c = @import("../common/constants.zig");
-const e = @import("../errors.zig");
+const e = @import("../common/errors.zig");
 const Node = @import("node.zig").Node;
 const Road = @import("road.zig").Road;
 
@@ -33,9 +33,9 @@ pub const NodeManager = struct {
     }
 
     /// Regular draw function
-    pub fn draw(self: *const NodeManager, pos: Vector2) void {
+    pub fn draw(self: *const NodeManager, pos: Vector2, display_info: bool) void {
         for (self.nodes.items) |node| {
-            node.draw(null);
+            node.draw(null, display_info);
         }
 
         if (self.temp_node) |node| {
@@ -43,10 +43,10 @@ pub const NodeManager = struct {
             var cur_node = Node.init(0, pos);
             // Temporary road that is to be drawn as one in the making
             const road: Road = .init(0, node, &cur_node);
-            road.draw(false);
+            road.draw(false, false);
 
-            node.draw(c.NODE_TEMP_COLOUR);
-            cur_node.draw(c.NODE_CURSOR_COLOUR);
+            node.draw(c.NODE_TEMP_COLOUR, display_info);
+            cur_node.draw(c.NODE_CURSOR_COLOUR, false);
         }
     }
 
@@ -79,10 +79,8 @@ pub const NodeManager = struct {
 
     /// Gets next id, resets only on clear()
     fn getNextID(self: *NodeManager) usize {
-        const id = self.next_id;
-        self.next_id += 1;
-
-        return id;
+        defer self.next_id += 1;
+        return self.next_id;
     }
 
     /// Clears all existing nodes connected, not deinitialisation
@@ -97,7 +95,7 @@ pub const NodeManager = struct {
     }
 
     /// Deletes node, returns error if node still has road references
-    pub fn deleteNode(self: *NodeManager, allocator: std.mem.Allocator, node_to_delete: *Node) !void {
+    pub fn removeNode(self: *NodeManager, allocator: std.mem.Allocator, node_to_delete: *Node) !void {
         for (0..self.nodes.items.len) |i| {
             if (self.nodes.items[i] != node_to_delete) continue;
 
@@ -118,16 +116,20 @@ pub const NodeManager = struct {
         return null;
     }
 
+    /// Essentially what it does is it sets temp node pointer to null and
+    /// if the node it pointed at had no road references (essentially it was a new node for road building),
+    /// it deletes the node from the node list as well
     pub fn deleteTempNode(self: *NodeManager, allocator: std.mem.Allocator) void {
         if (self.temp_node == null) return;
 
         const node = self.temp_node.?;
-        if (node.roads.items.len == 0)
-            self.deleteNode(allocator, node) catch |err| {
-                std.debug.panic("Failed to delete the temporary node: {}\n", .{err});
-            };
-
         self.temp_node = null;
+
+        if (node.roads.items.len != 0) return;
+        self.removeNode(allocator, node) catch |err| {
+            std.debug.panic("Failed to delete the temporary node: {}\n", .{err});
+        };
+
     }
 };
 
@@ -139,7 +141,9 @@ test "id tracking" {
     const allocator = gpa.allocator();
 
     var node_man: NodeManager = .init();
-    defer node_man.deinit(allocator);
+    defer node_man.deinit(allocator) catch |err| {
+        std.debug.panic("Failed to deinit nodemanager: {}\n", .{err});
+    };
     const n = 5;
 
     for (0..n) |_| {

src/infrastructure/road.zig

@@ -1,6 +1,7 @@
 const rl = @import("raylib");
 
 const c = @import("../common/constants.zig");
+const e = @import("../common/errors.zig");
 const st = @import("../common/structures.zig");
 const ut = @import("../common/utils.zig");
 const Node = @import("node.zig").Node;
@@ -46,9 +47,25 @@ pub const Road = struct {
     ///
     /// In the future as we improve and make roads more complex with multiple lanes and such
     /// it will gradually become more complex
-    pub fn draw(self: *const Road, highlighted: bool) void {
+    pub fn draw(self: *const Road, highlighted: bool, display_info: bool) void {
         const colour = if (highlighted) c.ROAD_HIGHLIGHTED_COLOUR else c.ROAD_COLOUR;
         rl.drawLineEx(self.nodes[0].pos, self.nodes[1].pos, c.ROAD_SIZE, colour);
+
+        if (!display_info) return;
+
+        var buf: [100]u8 = undefined;
+        const entity = std.fmt.bufPrintZ(&buf, "{d}", .{self.id}) catch |err| {
+            std.debug.panic("Could not allocate ID into string???: {}\n", .{err});
+        };
+
+        const distance = ut.getVectorP1P2(self.nodes[0].pos, self.nodes[1].pos);
+        const entity_info_pos: rl.Vector2 = .{
+            .x = self.nodes[0].pos.x + distance.x / 2 - c.ROAD_SIZE / 2,
+            .y = self.nodes[0].pos.y + distance.y / 2 - c.ROAD_SIZE / 2,
+        };
+
+        rl.drawText(entity, @trunc(entity_info_pos.x), @trunc(entity_info_pos.y),
+                c.ENTITY_DATA_TEXT_SIZE, c.ENTITY_DATA_TEXT_COLOUR);
     }
 
     /// Important: after this function executes, this road is no longer reachable from its bounding nodes
@@ -60,37 +77,31 @@ pub const Road = struct {
     }
 
     /// Checks whether pos coordinate is on the referenced road
-    pub fn isHighlighted(self: *const Road, pos: rl.Vector2) bool {
+    pub fn collides(self: *const Road, pos: rl.Vector2) bool {
         return rl.checkCollisionPointLine(pos, self.nodes[0].pos, self.nodes[1].pos, c.ROAD_SIZE);
     }
+
+    /// Updates node reference old_node => new node; returns error if old_node does not exist
+    pub fn updateNodeReference(self: *Road, old_node: *Node, new_node: *Node) !void {
+        for (0..self.nodes.len) |i| {
+            if (self.nodes[i] != old_node) continue;
+
+            self.nodes[i] = new_node;
+            // As nodes change, road's length must be recalculated
+            self.length = ut.calculate_length(self.nodes[0].pos, self.nodes[1].pos);
+            return;
+        }
+
+        return e.Entity.NotFound;
+    }
 };
 
 const std = @import("std");
 const expect = std.testing.expect;
 
 test "valid road nodes" {
-    var gpa: std.heap.DebugAllocator(.{}) = .init;
-    defer _ = gpa.deinit();
-    const allocator = gpa.allocator();
-
-    const start: Node = .init(34, .{.x = 500, .y = 500});
-    const start_ptr = try allocator.create(Node);
-    defer {
-        start_ptr.deinit(allocator);
-        allocator.destroy(start_ptr);
-    }
-    start_ptr.* = start;
-
-    const end: Node = .init(227, .{.x = 600, .y = 500});
-    const end_ptr = try allocator.create(Node);
-    defer {
-        end_ptr.deinit(allocator);
-        allocator.destroy(end_ptr);
-    }
-    end_ptr.* = end;
-
-    const road: Road = .init(11, start_ptr, end_ptr);
-
-    try expect(road.nodes[0].id == 34);
-    try expect(road.nodes[1].id == 227);
+    // TODO rewrite
 }
+
+// TODO tests
+// test every case error for every function that can return an error

src/infrastructure/road_manager.zig

@@ -1,7 +1,7 @@
 const std = @import("std");
 const rl = @import("raylib");
 
-const e = @import("../errors.zig");
+const e = @import("../common/errors.zig");
 const st = @import("../common/structures.zig");
 const ut = @import("../common/utils.zig");
 const Road = @import("road.zig").Road;
@@ -27,19 +27,18 @@ pub const RoadManager = struct {
     }
 
     /// Draws all the roads in the list, sends the information ahead whether the road drawn should be highlighted
-    pub fn draw(self: *const RoadManager, highlighted_road: ?*Road) void {
+    pub fn draw(self: *const RoadManager, highlighted_road: ?*Road, display_info: bool) void {
         for (self.roads.items) |road| {
             const is_highlighted = if (highlighted_road) |h_road| road == h_road else false;
-            road.draw(is_highlighted);
+            road.draw(is_highlighted, display_info);
         }
     }
 
     /// Function which creates the road object, its pointer, adds it to the list
     /// and then also references that same road to the bounding nodes
     pub fn addRoad(self: *RoadManager, allocator: std.mem.Allocator, start: *Node, end: *Node) !void {
-        const road: Road = .init(self.getNextID(), start, end);
         const road_ptr = try allocator.create(Road);
-        road_ptr.* = road;
+        road_ptr.* = Road.init(self.getNextID(), start, end);
         try self.roads.append(allocator, road_ptr);
 
         const ref = self.roads.items[self.roads.items.len - 1];
@@ -49,10 +48,8 @@ pub const RoadManager = struct {
 
     /// Returns the id, and increases it by one; used for generating ID's for new entities
     fn getNextID(self: *RoadManager) usize {
-        const id = self.next_id;
-        self.next_id += 1;
-
-        return id;
+        defer self.next_id += 1;
+        return self.next_id;
     }
 
     /// Deinits all the roads, clears them but not deiniting the list itself; also resets the next ID var
@@ -89,7 +86,7 @@ pub const RoadManager = struct {
     /// Returns if pos is pointing at a road, or null if it isn't at any
     pub fn getHighlightedRoad(self: *const RoadManager, pos: Vector2) ?*Road {
         for (self.roads.items) |road| {
-            if (road.isHighlighted(pos)) return road;
+            if (road.collides(pos)) return road;
         }
 
         return null;
@@ -100,36 +97,7 @@ const Vector2 = @import("raylib").Vector2;
 const expect = std.testing.expect;
 
 test "id tracking" {
-    var gpa: std.heap.DebugAllocator(.{}) = .init;
-    defer _ = gpa.deinit();
-    const allocator = gpa.allocator();
-
-    var road_man: RoadManager = .init();
-    defer road_man.deinit(allocator);
-    const n = 5;
-
-    const start: Node = .init(0, .{.x = 0, .y = 0});
-    const start_ptr = try allocator.create(Node);
-    start_ptr.* = start;
-
-    const end: Node = .init(1, .{.x = 100, .y = 100});
-    const end_ptr = try allocator.create(Node);
-    end_ptr.* = end;
-
-    defer {
-        start_ptr.deinit(allocator);
-        end_ptr.deinit(allocator);
-
-        allocator.destroy(start_ptr);
-        allocator.destroy(end_ptr);
-    }
-
-    for (0..n) |_| {
-        try road_man.addRoad(allocator, start_ptr, end_ptr);
-    }
-
-    try expect(road_man.next_id == n);
-    try expect(road_man.roads.items.len == n);
+    // TODO rewrite
 }
 
 // TODO tests

src/main.zig

@@ -11,14 +11,16 @@ pub fn main(init: std.process.Init) !void {
         .msaa_4x_hint = true,
         .window_highdpi = true,
     });
-    rl.initWindow(c.WIDTH, c.HEIGHT, "Base Road Network");
+    rl.initWindow(c.WIDTH, c.HEIGHT, "Traffic Simulator");
     defer rl.closeWindow();
 
     const monitor = 0;
     rl.setWindowMonitor(monitor);
     rl.setTargetFPS(rl.getMonitorRefreshRate(monitor));
 
-    var sim: Simulator = .init(allocator);
+    const rand_impl: std.Random.IoSource = .{ .io = init.io };
+
+    var sim: Simulator = .init(allocator, &rand_impl);
     defer sim.deinit() catch |err| {
         std.debug.panic("Failed to deinitialise the sim: {}\n", .{err});
     };
@@ -34,3 +36,14 @@ pub fn main(init: std.process.Init) !void {
         sim.draw(pos);
     }
 }
+
+test "test rng" {
+    const io = std.testing.io;
+    const rng_impl: std.Random.IoSource = .{ .io = io };
+    const rng = rng_impl.interface();
+
+    const n_max = 1000;
+    const n_rng = rng.uintLessThan(usize, n_max);
+
+    std.debug.print("{d}\n", .{n_rng});
+}

src/simulator.zig

@@ -6,8 +6,10 @@ const st = @import("common/structures.zig");
 const ut = @import("common/utils.zig");
 const Road = @import("infrastructure/road.zig").Road;
 const Node = @import("infrastructure/node.zig").Node;
+const Car = @import("vehicles/car.zig").Car;
 const NodeManager = @import("infrastructure/node_manager.zig").NodeManager;
 const RoadManager = @import("infrastructure/road_manager.zig").RoadManager;
+const CarManager = @import("vehicles/car_manager.zig").CarManager;
 
 pub const Simulator = struct {
     /// allocator for convenience
@@ -16,6 +18,8 @@ pub const Simulator = struct {
     node_man: NodeManager,
     /// 'class' tracking all the roads (and appropriate functions)
     road_man: RoadManager,
+    /// 'class' tracking all the cars (and appropriate functions)
+    car_man: CarManager,
     // vars
     /// Tracks whether next road will start building from the node the last road was built at
     auto_continue: bool,
@@ -29,23 +33,32 @@ pub const Simulator = struct {
     ///
     /// Note: It only works outside of the delete mode
     show_connections: bool,
+    /// Toggle that tracks whether ID (or possibly something more in the future) of every entity is displayed in GUI
+    display_entity_info: bool,
+    /// Entity (car/road/node) that is highlighed (hovered over by a mouse)
     highlighted_entity: ?st.Entity,
+    /// Interface for RNG
+    random: std.Random,
 
     /// Constructor for convenience
-    pub fn init(new_allocator: std.mem.Allocator) Simulator {
+    pub fn init(new_allocator: std.mem.Allocator, rand_impl: *const std.Random.IoSource) Simulator {
         return .{
             .allocator = new_allocator,
             .node_man = .init(),
             .road_man = .init(),
+            .car_man = .init(),
             .auto_continue = false,
             .delete_mode = false,
             .show_connections = false,
+            .display_entity_info = false,
             .highlighted_entity = null,
+            .random = rand_impl.interface(),
         };
     }
 
     /// Deinitialisation of node and road objects
     pub fn deinit(self: *Simulator) !void {
+        self.car_man.deinit(self.allocator);
         self.road_man.deinit(self.allocator);
         try self.node_man.deinit(self.allocator);
     }
@@ -61,8 +74,9 @@ pub const Simulator = struct {
             }
         }
 
-        self.road_man.draw(highlighted_road);
-        self.node_man.draw(pos);
+        self.road_man.draw(highlighted_road, self.display_entity_info);
+        self.node_man.draw(pos, self.display_entity_info);
+        self.car_man.draw(self.display_entity_info);
 
         self.drawRelatedSelectedEntities();
     }
@@ -76,19 +90,22 @@ pub const Simulator = struct {
                 const node = h_entity.node;
 
                 for (node.roads.items) |road| {
-                    road.draw(true);
+                    road.draw(true, self.display_entity_info);
                 }
 
-                node.draw(c.NODE_RELATED_COLOUR);
+                node.draw(c.NODE_RELATED_COLOUR, self.display_entity_info);
             },
             .road => {
                 const road = h_entity.road;
 
-                road.draw(true);
+                road.draw(true, self.display_entity_info);
 
-                road.nodes[0].draw(c.NODE_RELATED_COLOUR);
-                road.nodes[1].draw(c.NODE_RELATED_COLOUR);
+                road.nodes[0].draw(c.NODE_RELATED_COLOUR, self.display_entity_info);
+                road.nodes[1].draw(c.NODE_RELATED_COLOUR, self.display_entity_info);
             },
+            .car => {
+                // TODO draw the origin and destination, connected by the pathfinding route
+            }
         }
     }
 
@@ -109,6 +126,8 @@ pub const Simulator = struct {
         self.delete_mode = rl.isKeyDown(.left_shift);
         self.show_connections = rl.isKeyDown(.left_alt) and !self.delete_mode;
 
+        if (rl.isKeyReleased(.n)) self.createCar();
+        if (rl.isKeyReleased(.tab)) self.display_entity_info = !self.display_entity_info;
         if (rl.isKeyReleased(.c)) self.clear() catch |err| {
             std.debug.panic("Failed to clear the entities: {}\n", .{err});
         };
@@ -127,16 +146,16 @@ pub const Simulator = struct {
     /// Function that handles functionality that executes upon left click
     fn leftClickEvent(self: *Simulator, pos: rl.Vector2) void {
         if (self.delete_mode and self.highlighted_entity != null and self.highlighted_entity.? == .road) {
-            self.delete_road() catch |err| {
+            self.deleteRoad() catch |err| {
                 std.debug.panic("Failed to delete the road: {}\n", .{err});
             };
             return;
         }
-        self.new_road(pos);
+        self.createRoad(pos);
     }
 
     /// User initiated road building functionality
-    fn new_road(self: *Simulator, pos: rl.Vector2) void {
+    fn createRoad(self: *Simulator, pos: rl.Vector2) void {
         if (self.show_connections) return;
         const cur_node = self.node_man.getSelectedNode(self.allocator, pos) catch |err| {
             std.debug.panic("Failed to append the newly created node at pos ({d}, {d}) to node list: {}\n", .{
@@ -148,21 +167,11 @@ pub const Simulator = struct {
             // Prevents the road from being attached to 2 identical nodes (0 length road)
             if (temp.id == cur_node.id) return;
 
-            // TODO replace with road splitting
-            self.road_man.addRoad(self.allocator, temp, cur_node) catch |err| {
-                std.debug.panic("Failed to add a new road or assigning its nodes: {}\n", .{err});
-            };
-
             const intersections = self.getIntersectingRoads(self.allocator, temp, cur_node) catch |err| {
                 std.debug.panic("Intersection selection failure: {}\n", .{err});
             };
-            // DEBUG TODO REMOVE
-            std.debug.print("Displaying intersection position and the intersected road:\n", .{});
-            for (0..intersections.len) |i| {
-                const int = intersections[i];
-                std.debug.print("Road ID={d} Pos: ({d}, {d})\n", .{int.road.id, int.pos.x, int.pos.y});
-            }
-
+            defer self.allocator.free(intersections);
+            self.splitRoadsByIntersections(intersections, temp, cur_node);
 
             self.node_man.temp_node = if (self.auto_continue) cur_node else null;
             return;
@@ -172,7 +181,7 @@ pub const Simulator = struct {
     }
 
     /// User initiated road destroying functionality
-    fn delete_road(self: *Simulator) !void {
+    fn deleteRoad(self: *Simulator) !void {
         // We can trust this because this only gets called if valid and if type is road
         std.debug.assert(self.highlighted_entity != null and self.highlighted_entity.? == .road);
         const h_road = self.highlighted_entity.?.road;
@@ -180,20 +189,31 @@ pub const Simulator = struct {
         const start_node = h_road.nodes[0];
         const end_node = h_road.nodes[1];
 
-        self.road_man.deleteRoad(self.allocator, h_road) catch |err| {
-            std.debug.panic("Road deletion failed: {}\n", .{err});
-        };
+        try self.road_man.deleteRoad(self.allocator, h_road);
 
-        if (start_node.roads.items.len == 0)
-            try self.node_man.deleteNode(self.allocator, start_node);
+        if (start_node.roads.items.len == 0) {
+            const cars = try self.car_man.getCarsOnInf(self.allocator, .{ .node = start_node });
+            defer self.allocator.free(cars);
 
-        if (end_node.roads.items.len == 0)
-            try self.node_man.deleteNode(self.allocator, end_node);
+            // TODO replace with removeMultipleCars
+            for (self.car_man.cars.items) |car| {
+                try self.car_man.removeCar(self.allocator, car);
+            }
+
+            try self.node_man.removeNode(self.allocator, start_node);
+        }
+
+        if (end_node.roads.items.len == 0) {
+            // TODO same as above
+            try self.node_man.removeNode(self.allocator, end_node);
+            // TODO after this is done, do the same with the function that removes roads
+        }
     }
 
     /// Clearing node and road lists without deinitialising them (only the children)
     fn clear(self: *Simulator) !void {
         self.highlighted_entity = null;
+        self.car_man.clear(self.allocator);
         self.road_man.clear(self.allocator);
         try self.node_man.clear(self.allocator);
     }
@@ -213,20 +233,48 @@ pub const Simulator = struct {
         self.highlighted_entity = null;
     }
 
+    /// Returns array of IntersectionData struct, containing pointers to roads that got intersected and exact position
     fn getIntersectingRoads(self: *const Simulator, allocator: std.mem.Allocator, start: *const Node, end: *const Node) ![]st.IntersectionData {
         var intersections: std.ArrayList(st.IntersectionData) = .empty;
         var collision_point: rl.Vector2 = undefined;
 
+        var start_node_collision: ?*Road = null;
+        var end_node_collision: ?*Road = null;
+
+        // Here we will check if any road collides with start and end node
+        for (self.road_man.roads.items) |road| {
+            if (start_node_collision == null and road.collides(start.pos) and !start.roadsContains(road))
+                start_node_collision = road;
+            if (end_node_collision == null and road.collides(end.pos) and !end.roadsContains(road))
+                end_node_collision = road;
+
+            if (start_node_collision != null and end_node_collision != null) break;
+        }
+
+        // if road node is placed on the road it is added as a collision with said road
+        if (start_node_collision) |road| {
+            try intersections.append(self.allocator, .{
+                .road = road,
+                .pos = start.pos,
+                .origin = true,
+            });
+        }
+
         outer: for (self.road_man.roads.items) |road| {
-            if (!rl.checkCollisionLines(start.pos, end.pos, road.nodes[0].pos, road.nodes[1].pos, &collision_point))
+            if (!rl.checkCollisionLines(
+                start.pos,end.pos,
+                road.nodes[0].pos, road.nodes[1].pos,
+                &collision_point))
                 continue;
 
             const intersection = st.IntersectionData {
                 .road = road,
                 .pos = collision_point,
+                .origin = false,
             };
 
-            // We put a 0 here, just to satisfy the constructor function
+            // We put a 0 here, just to satisfy the constructor function,
+            // it is not getting appended to the node list anyways
             const node: Node = .init(0, intersection.pos);
             // If the newly acquired intersection node is within the snapping radius of already existing nodes,
             // we don't add it to the list
@@ -236,22 +284,138 @@ pub const Simulator = struct {
 
             // If there is an existing node that covers our position within its snapping radius,
             // then such position will not be saved as intersection
-            if (self.node_man.getNodeIfExists(node.pos) != null) continue :outer;
+            if (self.node_man.getNodeIfExists(node.pos) != null) continue;
 
             try intersections.append(allocator, intersection);
         }
 
+        // if end node is placed on the road it is added as a collision with said road
+        if (end_node_collision) |road| {
+            try intersections.append(self.allocator, .{
+                .road = road,
+                .pos = end.pos,
+                .origin = true,
+            });
+        }
+
         const sorted_intersection = try intersections.toOwnedSlice(allocator);
         std.sort.block(st.IntersectionData, sorted_intersection, start, ut.compareIntersections);
 
         return sorted_intersection;
     }
 
-    fn splitRoadsByIntersections(self: *Simulator, intersections: st.IntersectionData, start: *Node, end: *Node) void {
-        _ = intersections; // autofix
-        _ = end; // autofix
-        _ = start; // autofix
-        _ = self; // autofix
+    /// Takes the data about intersections and adds new nodes there alongside with linking existing roads to them
+    ///
+    /// Important: This function assumes the intersection array is sorted by distance from the start node (ascending)
+    fn splitRoadsByIntersections(self: *Simulator, intersections: []st.IntersectionData, start: *Node, end: *Node) void {
+        if (intersections.len == 0) {
+            self.road_man.addRoad(self.allocator, start, end) catch |err| {
+                std.debug.panic("Failed creating the road out of origin nodes: {}\n", .{err});
+            };
+            return;
+        }
 
+        const first_node = self.node_man.getSelectedNode(self.allocator, intersections[0].pos) catch |err| {
+            std.debug.panic("Failed to add the first node of the intersection: {}\n", .{err});
+        };
+
+        var override_node: ?*Node = null;
+        // This if statement essentially checks that IF we only have one intersection and that one is one of the origin nodes,
+        // it means that we have to enable one of start => intersection, or, end => intersection road building logic
+        //
+        // However due to the possibility that we link the road to itself (intersection[0] is start that we then connect
+        // that one to start node; so intersection[0] => start = start => start),
+        // we have to essentially realise which node is that first intersection and essentially store that info and only
+        // let the opposite node form a road with the intersection
+        // and that is what override_node, override_start and override_end variables are all about
+        if (intersections.len == 1 and intersections[0].origin) {
+            override_node = if (first_node == start) end else start;
+        }
+
+        const override_start = override_node != null and override_node.? == start;
+        if (!intersections[0].origin or override_start) {
+            // Here we connect the start node with the first intersection node (via road)
+            self.road_man.addRoad(self.allocator, start, first_node) catch |err| {
+                std.debug.panic("Failed to add a road of origin (start) node and the first intersection node: {}\n", .{err});
+            };
+        }
+
+        for (0..intersections.len) |i| {
+            const intersection = intersections[i];
+
+            // The node created at the point of intersection
+            const new_node = self.node_man.getSelectedNode(self.allocator, intersection.pos) catch |err| {
+                std.debug.panic("Failed to create a node based on the intersection index {d}: {}\n", .{
+                    i,
+                    err
+                });
+            };
+
+            // Pointer to the node that borders the road that was intersected
+            // This node and the new_node will become nodes for the new road being created
+            const old_node_of_road = intersection.road.nodes[1];
+
+            // The old road that was intersected now borders the new node
+            // and the old node is removed from the road's end node reference,
+            // as is the end node's road reference
+
+            // So the intersected road loses old node (at the far end) and gets new node that intersects it
+            intersection.road.updateNodeReference(old_node_of_road, new_node) catch |err| {
+                std.debug.panic("Failed to update the road's node references: {}\n", .{err});
+            };
+            // Now the old node must not point at the intersection road
+            old_node_of_road.unreferenceRoad(intersection.road) catch |err| {
+                std.debug.panic("Failed to unreference the intersection road from the old node: {}\n", .{err});
+            };
+            new_node.referenceRoad(self.allocator, intersection.road) catch |err| {
+                std.debug.panic("Failed to reference the intersection road to the intersecting node: {}\n", .{err});
+            };
+
+            // Now we add the road (to the road list) and references the road at both bounding nodes
+            self.road_man.addRoad(self.allocator, new_node, old_node_of_road) catch |err| {
+                std.debug.panic("Failed to create a road of new node and former node of prior intersecting road: {}\n", .{
+                    err
+                });
+            };
+
+            // Here we work on creating new roads between intersection nodes and as such because we need nodes
+            // at 2 different intersections, it means we have to be sure next one exists
+            if (i == intersections.len - 1) continue;
+
+            const next_intersection = self.node_man.getSelectedNode(self.allocator, intersections[i+1].pos) catch |err| {
+                std.debug.panic("Failed to create node of next intersection (current index={d}: {}\n", .{i, err});
+            };
+
+            // Creating the road connecting current intersection with the next one
+            self.road_man.addRoad(self.allocator, new_node, next_intersection) catch |err| {
+                std.debug.panic("Failed to create the road of current and next intersection nodes: {}\n", .{err});
+            };
+        }
+
+        const override_end = override_node != null and override_node.? == end;
+
+        // Finally we create final road by connecting last intersection node to the end origin node
+        const final_intersection = intersections[intersections.len - 1];
+        const final_intersection_node = self.node_man.getSelectedNode(self.allocator, final_intersection.pos) catch |err| {
+            std.debug.panic("Failed to create node based on last intersection position: {}\n", .{err});
+        };
+
+        if (final_intersection.origin and !override_end) return;
+        self.road_man.addRoad(self.allocator, final_intersection_node, end) catch |err| {
+            std.debug.panic("Failed to create a road of final intersection and end origin node: {}\n", .{err});
+        };
+    }
+
+    /// Creates a car and calls
+    fn createCar(self: *Simulator) void {
+        const nodes_len = self.node_man.nodes.items.len;
+        if (nodes_len == 0) return;
+        // Grab random node
+        const i = self.random.uintLessThan(usize, nodes_len);
+
+        const ref_node = self.node_man.nodes.items[i];
+        self.car_man.addCar(self.allocator, ref_node) catch |err| {
+            std.debug.panic("Unable to create a car or append it to the list of cars: {}\n", .{err});
+        };
     }
 };

src/test.zig

@@ -3,4 +3,5 @@ test {
     _ = @import("infrastructure/road.zig");
     _ = @import("infrastructure/node_manager.zig");
     _ = @import("infrastructure/road_manager.zig");
+    _ = @import("main.zig");
 }

src/vehicles/car.zig

@@ -0,0 +1,55 @@
+const std = @import("std");
+const rl = @import("raylib");
+
+const c = @import("../common/constants.zig");
+const st = @import("../common/structures.zig");
+const ut = @import("../common/utils.zig");
+const Node = @import("../infrastructure/node.zig").Node;
+
+pub const Car = struct {
+    /// Car ID, for easier debugging and identification
+    id: usize,
+    /// When car progresses along the road its location is determined via entity id and progress
+    progress: f32,
+    /// Tracks which infrastructure (pointer) the car is currently located at
+    inf: st.Infrastructure,
+
+    pub fn init(new_id: usize, spawn_node: *Node) Car {
+        return .{
+            .id = new_id,
+            .progress = 0,
+            .inf = .{ .node = spawn_node },
+        };
+    }
+
+    pub fn deinit(self: *Car, allocator: std.mem.Allocator) void {
+        allocator.destroy(self);
+    }
+
+    pub fn draw(self: *const Car, display_info: bool) void {
+        var pos: rl.Vector2 = undefined;
+
+        switch (self.inf) {
+            .node => |node| pos = node.pos,
+            .road => |road| {
+                const road_vector = ut.getVectorP1P2(road.nodes[0].pos, road.nodes[1].pos);
+                pos = .{
+                    .x = road_vector.x / 2,
+                    .y = road_vector.y / 2,
+                };
+            }
+        }
+
+        rl.drawEllipseV(pos, 20, 15, .red);
+
+        if (!display_info) return;
+
+        var buf: [100]u8 = undefined;
+        const entity_info = std.fmt.bufPrintZ(&buf, "{d}", .{ self.id }) catch |err| {
+            std.debug.panic("Failed to allocate space for ID???: {}\n", .{ err });
+        };
+
+
+        rl.drawText(entity_info, @trunc(pos.x), @trunc(pos.y), c.ENTITY_DATA_TEXT_SIZE, c.ENTITY_DATA_TEXT_COLOUR);
+    }
+};

src/vehicles/car_manager.zig

@@ -0,0 +1,95 @@
+const std = @import("std");
+const Vector2 = @import("raylib").Vector2;
+
+const e = @import("../common/errors.zig");
+const ut = @import("../common/structures.zig");
+const Node = @import("../infrastructure/node.zig").Node;
+const Car = @import("car.zig").Car;
+
+pub const CarManager = struct {
+    next_id: usize,
+    cars: std.ArrayList(*Car),
+
+    pub fn init() CarManager {
+        return .{
+            .next_id = 0,
+            .cars = .empty,
+        };
+    }
+
+    pub fn deinit(self: *CarManager, allocator: std.mem.Allocator) void {
+        for (self.cars.items) |car| {
+            car.deinit(allocator);
+        }
+
+        self.cars.deinit(allocator);
+    }
+
+    pub fn draw(self: *const CarManager, display_info: bool) void {
+        for (self.cars.items) |car| {
+            car.draw(display_info);
+        }
+    }
+
+    pub fn getNextID(self: *CarManager) usize {
+        defer self.next_id += 1;
+        return self.next_id;
+    }
+
+    pub fn addCar(self: *CarManager, allocator: std.mem.Allocator, node_ref: *Node) !void {
+        const car_ptr = try allocator.create(Car);
+        car_ptr.* = .init(self.getNextID(), node_ref);
+
+        try self.cars.append(allocator, car_ptr);
+    }
+
+    pub fn clear(self: *CarManager, allocator: std.mem.Allocator) void {
+        for (self.cars.items) |car| {
+            car.deinit(allocator);
+        }
+        self.cars.clearRetainingCapacity();
+        self.next_id = 0;
+    }
+
+    /// This function returns array of cars which are located on the node/road specified in the `inf` parameter
+    pub fn getCarsOnInf(self: *const CarManager, allocator: std.mem.Allocator, inf: ut.Infrastructure) ![]*Car {
+        var cars: std.ArrayList(*Car) = .empty;
+
+        const active_inf = std.meta.activeTag(inf);
+
+        for (self.cars.items) |car| {
+            if (std.meta.activeTag(car.inf) != active_inf) continue;
+
+            switch (car.inf) {
+                inline else => |a, tag| {
+                    const b = @field(inf, @tagName(tag));
+                    if (a == b) try cars.append(allocator, car);
+                }
+            }
+        }
+
+        return cars.toOwnedSlice(allocator);
+    }
+
+    /// Attempts to deinit and remove the (passed) car;
+    /// returns an error if car doesn't exist in the list
+    pub fn removeCar(self: *CarManager, allocator: std.mem.Allocator, car_to_delete: *Car) !void {
+        for (self.cars.items, 0..) |car, index| {
+            if (car != car_to_delete) continue;
+
+            car.deinit(allocator);
+            _ = self.cars.swapRemove(index);
+            return;
+        }
+
+        return e.Entity.NotFound;
+    }
+
+    /// TODO
+    pub fn removeMultipleCars(self: *CarManager, allocator: std.mem.Allocator, cars_to_delete: []*Car) !void {
+        _ = cars_to_delete; // autofix
+        _ = allocator; // autofix
+        _ = self; // autofix
+
+    }
+};