NASA rover challenge

maribel/public/Class25_Exercises_NASARoverChallenge.md

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+## NASA Rover Challenge
+
+![img](../assets/clase25/9286f625-27c8-4c25-88d6-425510bb04e8.jpg)
+
+**Context**
+The purpose of this test is to enable you to demonstrate your proficiency in solving problems using software engineering tools and processes. Read the specification below and produce a solution. 
+
+Your solution should be in the form of completed code. The problem specified below requires a solution that receives input, does some processing and then returns some output.
+
+**Specification**
+A robotic rover is to be landed by NASA on a plateau on Mars. This plateau, which is curiously square, must be navigated by the rover so that its on board cameras can get a complete view of the surrounding terrain to send back to Earth.
+
+A rover's position is represented by a combination of an x and y coordinates and a letter representing one of the four cardinal compass points. 
+
+The plateau is divided up into a grid to simplify navigation. 
+
+An example position might be 0, 0, N, which means the rover is in the bottom left corner and facing North. In order to control a rover, NASA sends a simple string of letters. The possible letters are 'L', 'R' and 'M'. 
+
+'L' and 'R' makes the rover spin 90 degrees left or right respectively, without moving from its current spot. 'M' means move forward one grid point, and maintain the same heading.
+
+Assume that the square directly North from (x, y) is (x, y+1).
+
+**Input**
+The first parameter is the size of the square (the lower-left coordinates are assumed to be 0,0).
+
+The rest of parameters is information pertaining to the rover that has been deployed. 
+
+The second argument gives the rover's position, and the third is a series of instructions telling the rover how to explore the plateau. The position is made up of two integers and a letter, corresponding to the x and y coordinates and the rover's orientation.
+
+**Output**
+The output should be the final coordinates and heading.
+
+**Example**
+function setup(5, “1 2 N”, [“L”, “M”, “L”, “M”, “L”, “M”, “L”, “M”, “M”])
+Expected Output: “1 3 N”
+
+```javascript
+var machine = {
+    squareSize: 5,
+    position: {
+        x: 0,
+        y: 0
+    },
+    instructions: [],
+    state: "N",
+    transitions: {
+        "N" : {
+            M: function(){
+                this.changePositionTo(this.position.x, this.position.y + 1);
+            },
+            L: function(){
+                this.changeStateTo("W");
+            },
+            R: function(){
+                this.changeStateTo("E");
+            }
+        },
+        "E" : {
+            M: function(){
+                this.changePositionTo(this.position.x + 1, this.position.y);
+            },
+            L: function(){
+                this.changeStateTo("N");
+            },
+            R: function(){
+                this.changeStateTo("S");
+            }
+        },
+        "S": {
+            M: function(){
+                this.changePositionTo(this.position.x, this.position.y - 1);
+            },
+            L: function(){
+                this.changeStateTo("E");
+            },
+            R: function(){
+                this.changeStateTo("W");
+            }
+        },
+        "W": {
+            M: function(){
+                this.changePositionTo(this.position.x - 1, this.position.y);
+            },
+            L: function(){
+                this.changeStateTo("S");
+            },
+            R: function(){
+                this.changeStateTo("N");
+            }
+        }
+    },
+
+    dispatch(actionName) {
+        const action = this.transitions[this.state][actionName];
+
+        if (action) {
+            action.apply(machine);
+        }
+    },
+
+    changeStateTo(newState) {
+        this.state = newState;
+    },
+
+    changePositionTo(newX, newY) {
+        var newXIsValid = (newX >= 0 && newX < this.squareSize);
+        var newYIsValid = (newY >= 0 && newY < this.squareSize);
+        if (newXIsValid && newYIsValid) {
+            this.position.x = newX;
+            this.position.y = newY;
+        }
+    },
+
+    executeInstructions() {
+        this.instructions.forEach(instr => {
+            machine.dispatch(instr);
+        });
+
+        var finalResult = [this.position.x, this.position.y, this.state].join(" ");
+        console.log(finalResult);
+    }
+}
+
+function setup(squareSize, initialPosition, instructions) {
+    machine.squareSize = squareSize;
+
+    initialPosition = initialPosition.split(" ");
+    machine.position.x = parseInt(initialPosition[0]);
+    machine.position.y = parseInt(initialPosition[1]);
+    machine.state = initialPosition[2];
+
+    machine.instructions = instructions;
+}
+
+function start() {
+    machine.executeInstructions();
+}
+
+setup(5, "1 2 N", ["L", "M", "L", "M", "L", "M", "L", "M", "M"]);
+start();
+```