Program complete

index.js

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+/*
+Creative Cash Draw Solutions - Cash Register (demo program for SoftWriters)
+https://github.com/SoftWriters/CashRegister
+
+CLIENT GOALS / REQUIREMENTS
+Please write a program which accomplishes the clients goals. The program should:
+  * Accept a flat file as input
+    * Each line will contain the total due and the amount paid separated by a comma (for example: 2.13,3.00)
+    * Expect that there will be multiple lines
+  * Output the change the cashier should return to the customer
+    * The return string should look like: 1 dollar,2 quarters,1 nickel, etc ...
+    * Each new line in the input file should be a new line in the output file
+
+
+Author: Greg Goodhile
+
+TECHNOLOGIES
+  Node
+  JavaScript
+
+TO RUN
+  node index.js  -OR-  npm run start
+
+*/
+
+'use strict';
+
+( () => {
+
+  const { readFile, writeFile } = require( './shared/FileSys' );
+  const { parseRecords, makeChangePhrase } = require( './shared/ChangeBuilder' );
+
+  const inputDataPath = './records/due-paid.csv';
+  const outDataPath = './records/change.csv';
+
+  const inputData = readFile( inputDataPath );
+
+  if ( inputData ) {
+    try {
+      // parse records from input file as amount due and amount paid; values converted to cents
+      const inputRecords = parseRecords( inputData );
+      // create output records in the form of comma-separated change denomination phrases
+      const outputRecords = inputRecords.map( makeChangePhrase );
+      // convert records array to a string with a newline character after each record
+      const outData = outputRecords.join( '\n' );
+
+      writeFile( outDataPath, outData );
+      console.log( 'Output file written' );
+    } catch ( err ) {
+      console.log( err.message );
+    }
+  } else {
+    console.log( 'No data to retrieve' );
+  }
+
+} )();

package.json

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+{
+  "name": "cashregister",
+  "version": "1.0.0",
+  "description": "Cash register service that will parse a flat file, perform logic to get the value of change owed to customer, convert value to change denominations equaling that value, write a new file to disk with that value.",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index.js"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/solarsnail/CashRegister.git"
+  },
+  "author": "Greg Goodhile",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/solarsnail/CashRegister/issues"
+  },
+  "homepage": "https://github.com/solarsnail/CashRegister#readme"
+}

records/change.csv

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+1 quarter,1 nickel,2 pennies
+6 dollars,1 quarter,1 nickel,1 penny
+136 dimes,8 pennies
+1 dollar,1 penny
+1 dollar
+10 dollars,1 quarter,1 dime,2 pennies

records/due-paid.csv

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+4.68,5.00
+3.69,10.00
+6.32,20.00
+8.99,10.00
+4.01,5.01
+9.63,20.00

shared/ChangeBuilder.js

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+/*
+Author: Greg Goodhile
+*/
+
+'use strict';
+
+/*
+Parse data as a list of records and evaluate the change owed back to customer.
+data <String>
+Returns <Array>
+*/
+const parseRecords = ( data ) => {
+	// Convert "number" string into cents/pennies; this removes a decimal point from the string; no need to worry about math precision using float numbers.
+	// Removing decimal from "number" string emulates multiplying a number by 100 to get cents/pennies.
+	// v <String>
+	// Returns <Number> | <NaN>
+	const toCents = ( v ) => {
+		// length must be at least 3 which signifies a valid currency decimal, ex: .45
+		// if a decimal is not found two places from the right, v is not an expected currency value
+		const vlen = v.length;
+		if ( vlen < 3 || v.indexOf( '.' ) !== vlen - 3 ) {
+			return NaN;
+		}
+
+		return Number( v.replace( '.', '' ) );
+	};
+
+	let recordList = [];
+	let dataLine = 1;
+	for ( const record of data.split( /\r?\n/ ) ) {
+		const recordSet = record.split( ',' );
+		if ( recordSet.length !== 2 ) {
+			throw new Error( `Invalid record set at line ${dataLine} : missing two values separated by a comma.` );
+		}
+
+		const due = toCents( recordSet[ 0 ] );
+		const paid = toCents( recordSet[ 1 ] );
+
+		if ( Number.isNaN( due ) || Number.isNaN( paid ) ) {
+			throw new Error( `Invalid record set at line ${dataLine} : invalid float value found while parsing.` );
+		}
+
+		if ( paid < due ) {
+			throw new Error( `Invalid record set at line ${dataLine} : amount paid is less than amount due.` );
+		}
+		// calculate the change owed
+		recordList.push( paid - due );
+		dataLine++;
+	}
+
+	return recordList;
+};
+
+/*
+	Create a comma-separated change denomination phrase
+	cents <Number>
+	Returns <String>
+*/
+const makeChangePhrase = ( cents ) => {
+	// Mapping for change quantity phrases
+	const phraseMap = {
+		noun100: ( qty ) => {
+			if ( qty === 0 ) return '';
+			return qty === 1 ? '1 dollar,' : `${qty} dollars,`;
+		},
+		noun25: ( qty ) => {
+			if ( qty === 0 ) return '';
+			return qty === 1 ? '1 quarter,' : `${qty} quarters,`;
+		},
+		noun10: ( qty ) => {
+			if ( qty === 0 ) return '';
+			return qty === 1 ? '1 dime,' : `${qty} dimes,`;
+		},
+		noun5: ( qty ) => {
+			if ( qty === 0 ) return '';
+			return qty === 1 ? '1 nickel,' : `${qty} nickels,`;
+		},
+		noun1: ( qty ) => {
+			if ( qty === 0 ) return '';
+			return qty === 1 ? '1 penny,' : `${qty} pennies,`;
+		}
+	};
+
+	// get cent count at centSize and leftOver cents
+	const denominationMap = ( leftOver, centSize ) => {
+		return {
+			centSize,
+			leftOver: leftOver % centSize,
+			count: Math.floor( leftOver / centSize )
+		};
+	};
+
+	// order of change denominations
+	let denomOrderList = [ 100, 25, 10, 5, 1 ];
+
+	// "DIVISIBLE BY 3 ~ TWIST CHECK"
+	if ( cents % 3 === 0 ) {
+		// shuffle denomOrderList
+		let tmpOrder = [];
+		for ( let i = denomOrderList.length - 1; i >= 0; i-- ) {
+			const randIndex = Math.floor( Math.random() * ( i + .99 ) );
+			tmpOrder.push( denomOrderList[ randIndex ] );
+			denomOrderList.splice( randIndex, 1 );
+		}
+		denomOrderList = tmpOrder;
+	}
+
+	// list of change mappings
+	let changeList = denomOrderList.map( ( v ) => {
+		let tmpCounter = denominationMap( cents, v );
+		cents = tmpCounter.leftOver;
+		return tmpCounter;
+	} );
+
+	let phrase = phraseMap.noun100( changeList.find( v => v.centSize === 100 ).count );
+	phrase += phraseMap.noun25( changeList.find( v => v.centSize === 25 ).count );
+	phrase += phraseMap.noun10( changeList.find( v => v.centSize === 10 ).count );
+	phrase += phraseMap.noun5( changeList.find( v => v.centSize === 5 ).count );
+	phrase += phraseMap.noun1( changeList.find( v => v.centSize === 1 ).count );
+
+	return phrase.slice( 0, -1 );
+};
+
+module.exports = { parseRecords, makeChangePhrase };

shared/FileSys.js

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+/*
+Author: Greg Goodhile
+*/
+
+'use strict';
+
+const fs = require( 'fs' );
+
+/*
+Read input file
+path <String>
+Returns <String>
+*/
+const readFile = ( path ) => {
+	try {
+		const data = fs.readFileSync( path, 'utf8' );
+		return data.length > 0 ? data : null;
+	} catch ( err ) {
+		console.log( err.message );
+		return null;
+	}
+};
+
+/*
+write output file
+path <String>
+Returns <String>
+*/
+const writeFile = ( path, data ) => {
+	try {
+		fs.writeFileSync( path, data, 'utf8' );
+	} catch ( err ) {
+		console.log( err.message );
+		throw new Error( 'Cannot write output file' );
+	}
+};
+
+module.exports = { readFile, writeFile };