Add simple state machine

.eslintignore

@@ -1,2 +1,3 @@
 dist
+coverage
 node_modules

.prettierignore

@@ -1,2 +1,3 @@
 dist
+coverage
 node_modules

package.json

@@ -46,6 +46,7 @@
     "prettier": "^1.14.3",
     "ts-jest": "^23.10.4",
     "ts-loader": "^5.2.2",
+    "tslib": "^1.9.3",
     "tslint": "^5.11.0",
     "tslint-eslint-rules": "^5.4.0",
     "typescript": "^3.1.3",
@@ -54,6 +55,15 @@
     "webpack-merge": "^4.1.4"
   },
   "jest": {
+    "globals": {
+      "ts-jest": {
+        "diagnostics": {
+          "ignoreCodes": [
+            151001
+          ]
+        }
+      }
+    },
     "transform": {
       "^.+\\.ts$": "ts-jest"
     },

src/index.ts

@@ -1,11 +1,29 @@
+import { StateMachine } from 'src/state_machine';
+
 /**
  * Parses a command line string into an argument array
  *
  * @param {string} arvgString - string that you would normally pass to the command line
  * @returns {string[]} array of arguments
  */
 export default function parseArgvString(arvgString: string): string[] {
-    return arvgString.split(' ');
+    const stateMachine = new StateMachine();
+    const output: string[] = [];
+    let currentOutputIndex = 0;
+
+    for (const character of arvgString) {
+        const outputCharacter = stateMachine.handleCharacter(character);
+
+        if (outputCharacter) {
+            output[currentOutputIndex] = output[currentOutputIndex]
+                ? output[currentOutputIndex] + character
+                : character;
+        } else if (output[currentOutputIndex]) {
+            currentOutputIndex++;
+        }
+    }
+
+    return output;
 }
 
 // Allows commonjs and es6 imports at the same time.

src/state_machine/index.ts

@@ -0,0 +1 @@
+export { default as StateMachine } from './state_machine';

src/state_machine/state_machine.ts

@@ -0,0 +1,26 @@
+import { getStateByHandle, StateHandle } from './states';
+
+export default class StateMachine {
+    private currentState = getStateByHandle(StateHandle.Empty);
+
+    public handleCharacter(character: string) {
+        const [outputCharacter, nextStateHandle] = this.performTransition(character);
+
+        if (nextStateHandle) {
+            this.currentState = getStateByHandle(nextStateHandle);
+        }
+
+        return outputCharacter;
+    }
+
+    private performTransition(character: string) {
+        const currentState = this.currentState;
+
+        switch (character) {
+            case ' ':
+                return currentState.onWhitespace(character);
+            default:
+                return currentState.onCharacter(character);
+        }
+    }
+}

src/state_machine/states/empty.ts

@@ -0,0 +1,12 @@
+import baseState, { State, StateHandle } from 'src/state_machine/states/state';
+
+const emptyState: State = {
+    ...baseState,
+    stateHandle: StateHandle.Empty,
+
+    onCharacter(character: string) {
+        return [character, StateHandle.InsideToken];
+    },
+};
+
+export default emptyState;

src/state_machine/states/factory.ts

@@ -0,0 +1,17 @@
+import { StateHandle } from './state';
+
+import emptyState from './empty';
+import insideTokenState from './inside_token';
+
+const ALL_STATES = [emptyState, insideTokenState];
+
+export default function getStateByHandle(stateHandle: StateHandle) {
+    for (const state of ALL_STATES) {
+        if (state.stateHandle === stateHandle) {
+            return state;
+        }
+    }
+
+    // istanbul ignore next line - shouldn't really happen
+    throw new Error(`State with handle = ${stateHandle} cannot be found`);
+}

src/state_machine/states/index.ts

@@ -0,0 +1,2 @@
+export { State, StateHandle } from './state';
+export { default as getStateByHandle } from './factory';

src/state_machine/states/inside_token.ts

@@ -0,0 +1,15 @@
+import baseState, { State, StateHandle } from 'src/state_machine/states/state';
+
+const insiteTokenState: State = {
+    ...baseState,
+    stateHandle: StateHandle.InsideToken,
+
+    onCharacter(character: string) {
+        return [character, null];
+    },
+    onWhitespace() {
+        return [null, StateHandle.Empty];
+    },
+};
+
+export default insiteTokenState;

src/state_machine/states/state.ts

@@ -0,0 +1,27 @@
+type HandlerFunction = (character: string) => [string | null, StateHandle | null];
+
+export interface State {
+    stateHandle: StateHandle;
+    onCharacter: HandlerFunction;
+    onWhitespace: HandlerFunction;
+    onDoubleQuote: HandlerFunction;
+    onSingleQuote: HandlerFunction;
+    onEscapeCharacter: HandlerFunction;
+}
+
+export enum StateHandle {
+    Empty,
+    InsideToken,
+}
+
+const defaultHandler: HandlerFunction = (_character: string) => [null, null];
+
+const baseState = {
+    onCharacter: defaultHandler,
+    onWhitespace: defaultHandler,
+    onDoubleQuote: defaultHandler,
+    onSingleQuote: defaultHandler,
+    onEscapeCharacter: defaultHandler,
+};
+
+export default baseState;

tests/index.spec.ts

@@ -4,3 +4,8 @@ it('can parse a simple space-separated string', () => {
     const commandString = 'npm run build';
     expect(parseArgvString(commandString)).toEqual(['npm', 'run', 'build']);
 });
+
+it('can handle trailing / leading spaces', () => {
+    const commandString = '   npm run    build  ';
+    expect(parseArgvString(commandString)).toEqual(['npm', 'run', 'build']);
+});

tsconfig.json

@@ -4,6 +4,7 @@
         "moduleResolution": "node",
         "target": "es5",
         "baseUrl": ".",
+        "importHelpers": true,
 
         "strict": true,
         "alwaysStrict": true,

tslint.json

@@ -83,7 +83,7 @@
       ],
       "triple-equals": true,
       "quotemark": [true, "single"],
-      "ter-indent": [true, 4],
+      "ter-indent": [true, 4, { "SwitchCase": 1 }],
       "variable-name": [true, "ban-keywords", "check-format", "allow-leading-underscore", "allow-pascal-case"],
       "whitespace": [true, "check-branch", "check-operator", "check-typecast", "check-decl", "check-separator"]
     }