Add parser for simple range expression

Implement parsing of ranges of the form "1, 3-5" into a set of all the
numbers it represents.

packages/lib/src/helpers.ts

@@ -230,6 +230,14 @@ export function formatBytes(bytes: number) {
 	return (power > 0 ? (bytes / factor ** power).toFixed(2) : bytes) + units[power];
 }
 
+function skipWhitespace(pos: number, input: string) {
+	// whitespace = 1*" "
+	while (pos < input.length && input.charAt(pos) === " ") {
+		pos += 1;
+	}
+	return pos;
+}
+
 function parseSearchIdentifier(pos: number, input: string): [number, string] {
 	// character = ? all characters excluding space : " ?
 	// identifier = 1*character
@@ -393,7 +401,6 @@ export function parseSearchString(
 	input: string,
 	attributes: Record<string, string> = {}
 ): ParsedSearch {
-	// whitespace = 1*" "
 	// search = [ term, *( [ whitespace ], term ) ]
 	input = input.trim();
 	let parsed = {
@@ -407,9 +414,7 @@ export function parseSearchString(
 		if (term) {
 			parsed.terms.push(term);
 		}
-		while (pos < input.length && input.charAt(pos) === " ") {
-			pos += 1;
-		}
+		pos = skipWhitespace(pos, input);
 	}
 	// istanbul ignore if (should not be possible)
 	if (pos !== input.length) {
@@ -417,3 +422,101 @@ export function parseSearchString(
 	}
 	return parsed;
 }
+
+function isDigit(pos: number, input: string) {
+	const code = input.charCodeAt(pos);
+	return "0".charCodeAt(0) <= code && code <= "9".charCodeAt(0);
+}
+
+function parseNumber(pos: number, input: string): [number, number] {
+	// number = 1*('0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9')
+	let startPos = pos;
+	let endPos = pos;
+	while (pos < input.length && isDigit(pos, input)) {
+		pos += 1;
+		endPos += 1;
+	}
+	return [pos, Number.parseInt(input.slice(startPos, endPos), 10)];
+}
+
+function parseRange(pos: number, input: string, min: number, max: number): [number, Set<number>] {
+	// range = number, [ whitespace ], [ '-', [ whitespace ], number ]
+	const range = new Set<number>();
+	if (!isDigit(pos, input)) {
+		throw new Error(`Expected digit but got '${input[pos]}' at pos ${pos} while parsing "${input}"`);
+	}
+	let start: number;
+	([pos, start] = parseNumber(pos, input));
+	pos = skipWhitespace(pos, input);
+	if (pos < input.length && input[pos] === "-") {
+		pos += 1; // Skip dash
+		pos = skipWhitespace(pos, input);
+		if (pos === input.length) {
+			throw new Error(`Expected digit but got end of input while parsing "${input}"`);
+		}
+		if (!isDigit(pos, input)) {
+			throw new Error(`Expected digit but got '${input[pos]}' at pos ${pos} while parsing "${input}"`);
+		}
+		let end: number;
+		([pos, end] = parseNumber(pos, input));
+
+		if (start > end) {
+			([start, end] = [end, start]);
+		}
+		if (start < min) {
+			throw new Error(`start of range ${start}-${end} is below the minimum value ${min}`);
+		}
+		if (end > max) {
+			throw new Error(`end of range ${start}-${end} is above the maximum value ${max}`);
+		}
+		for (let i = start; i <= end; i++) {
+			range.add(i);
+		}
+	} else { // Single value range
+		if (start < min) {
+			throw new Error(`value ${start} is below the minimum value ${min}`);
+		}
+		if (start > max) {
+			throw new Error(`value ${start} is above the maximum value ${max}`);
+		}
+		range.add(start);
+	}
+	return [pos, range];
+}
+
+/**
+ * Parse a comma separated range expression
+ *
+ * Parses the given input as a series of comma sepparated number ranges
+ * where each range can consist of either a whole number or a whole number
+ * of where the range starts, a dash and then a whole number of where the
+ * range ends inclusively.
+ *
+ * @param input - Range expression to parse
+ * @param min - Minimum accepted input value.
+ * @param max - Maximum accepted input value.
+ * @returns Set of all numbers in the parsed range.
+ */
+export function parseRanges(
+	input: string,
+	min: number,
+	max: number,
+) {
+	// ranges = [ range, *( [ whitespace ],  [ ',', [ whitespace ] ], range ) ]
+	input = input.trim();
+	const parsed = new Set<number>();
+	let pos = 0;
+	while (pos < input.length) {
+		let range: Set<number>;
+		([pos, range] = parseRange(pos, input, min, max));
+		for (const i of range) {
+			parsed.add(i);
+		}
+		pos = skipWhitespace(pos, input);
+		if (pos < input.length && input[pos] === ",") {
+			pos += 1;
+			pos = skipWhitespace(pos, input);
+		}
+	}
+	return parsed;
+}

test/lib/helpers.js

@@ -300,4 +300,57 @@ describe("lib/helpers", function() {
 			);
 		});
 	});
+	describe("parseRanges()", function() {
+		function range(input, min=1, max=10) {
+			return [...lib.parseRanges(input, min, max)];
+		}
+		function expectedRange(start, end) {
+			const items = new Set();
+			for (let i = start; i <= end; i++) {
+				items.add(i);
+			}
+			return [...items];
+		}
+		it("should parse numbers separated by spaces and or commas", function() {
+			assert.deepEqual(range("1"), [1]);
+			assert.deepEqual(range(" 1"), [1]);
+			assert.deepEqual(range("1 "), [1]);
+			assert.deepEqual(range(" 1 "), [1]);
+			assert.deepEqual(range("1 2"), [1, 2]);
+			assert.deepEqual(range("1, 2"), [1, 2]);
+			assert.deepEqual(range("1 , 2"), [1, 2]);
+			assert.deepEqual(range(" 1 2 "), [1, 2]);
+		});
+		it("should parse ranges", function() {
+			assert.deepEqual(range("1-4"), [1, 2, 3, 4]);
+			assert.deepEqual(range(" 1-4 "), [1, 2, 3, 4]);
+			assert.deepEqual(range(" 1 - 4 "), [1, 2, 3, 4]);
+			assert.deepEqual(range("1- 4"), [1, 2, 3, 4]);
+			assert.deepEqual(range("1 -4"), [1, 2, 3, 4]);
+			assert.deepEqual(range(" 1, 2-4"), [1, 2, 3, 4]);
+			assert.deepEqual(range("4-1"), [1, 2, 3, 4]);
+		});
+		it("should ignore duplicates in ranges", function() {
+			assert.deepEqual(range("1, 2, 2, 2"), [1, 2]);
+			assert.deepEqual(range("1-4, 3, 4"), [1, 2, 3, 4]);
+			assert.deepEqual(range("3, 1-4"), [3, 1, 2, 4]);
+		});
+		it("should throw on bad input", function() {
+			assert.throws(() => range("1-"), new Error('Expected digit but got end of input while parsing "1-"'));
+			assert.throws(() => range("a1-4"), new Error('Expected digit but got \'a\' at pos 0 while parsing "a1-4"'));
+			assert.throws(() => range("1a-4"), new Error('Expected digit but got \'a\' at pos 1 while parsing "1a-4"'));
+			assert.throws(() => range("1-a4"), new Error('Expected digit but got \'a\' at pos 2 while parsing "1-a4"'));
+			assert.throws(() => range("1-4a"), new Error('Expected digit but got \'a\' at pos 3 while parsing "1-4a"'));
+		});
+		it("should throw if out of range", function() {
+			assert.throws(() => range("0"), new Error("value 0 is below the minimum value 1"));
+			assert.throws(() => range("110"), new Error("value 110 is above the maximum value 10"));
+			assert.throws(() => range("1-999"), new Error("end of range 1-999 is above the maximum value 10"));
+			assert.throws(() => range("0-1"), new Error("start of range 0-1 is below the minimum value 1"));
+		});
+		it("should handle 16-bit ranges", function() {
+			assert.deepEqual(range("1-65535", 1, 2**16 - 1), expectedRange(1, 2**16 - 1));
+			assert.deepEqual(range("20000-20002", 1, 2**16 - 1), [20000, 20001, 20002]);
+		});
+	});
 });