Plug the constellation generator into the toolbox

index.html

@@ -25,6 +25,7 @@
 					<span>Color</span>
 					<select id="colors" class="color0"></select>
 				</li>
+				<button id="scatter">Scatter stars</button>
 			</ul>
 			<button id="load">Load</button>
 			<table id="grid"></table>

js/Constellation.js

@@ -0,0 +1,65 @@
+import generate from Grid.Util;
+
+return {
+	random: random
+};
+
+function random(size) {
+	var indices = Array.from({length: size}).map(function(x, i) {return i;});
+	var previousColumn;
+	var columns = []
+	while(columns.length < 8) {
+		previousColumn = pickNextColumn(indices, previousColumn)
+		columns.push(previousColumn);
+	}
+	return generate(size, size, function(cell) {
+		return columns[cell.row] == cell.column;
+	});
+}
+
+function pickNextColumn(columnsLeft, previousColumn) {
+	var parts = contiguousParts(columnsLeft);
+	if(parts.length == 1 && columnsLeft.length == 4) {
+		var candidateColumns = [null, columnsLeft[1], columnsLeft[2], null];
+	} else if(parts.length == 2 && columnsLeft.length < 5
+		&& Math.min(parts[0].length, parts[1].length) < 2) {
+		candidateColumns = parts[0].length == 1 ? [null].concat(parts[1]) : parts[0];
+	} else {
+		var candidateColumns = columnsLeft;
+	}
+	candidateColumns = candidateColumns.map(maskAround(previousColumn));
+	return columnsLeft.splice(pickIndex(candidateColumns), 1)[0];
+}
+
+function maskAround(c0) {
+	return function(c1) {
+		return Math.abs(c1 - c0) < 2 ? null : c1;
+	};
+}
+
+function pickIndex(t) {
+	var o = {};
+	var definedCount = 0;
+	for(var i = 0; i < t.length; i++) {
+		if(t[i] != undefined) {
+			o[definedCount] = i;
+			definedCount++;
+		}
+	}
+	return o[Math.floor(definedCount * Math.random())];
+}
+
+function contiguousParts(t) {
+	var parts = [];
+	var current = [];
+	for(var i = 0; i < t.length; i++) {
+		if(current.length < 1 || t[i] - current[current.length-1] == 1) {
+			current.push(t[i]);
+		} else {
+			parts.push(current);
+			current = [t[i]];
+		}
+	}
+	parts.push(current);
+	return parts;
+}

js/Toolbox.js

@@ -1,4 +1,5 @@
 import * as Dom from UnitJS.Dom;
+import Constellation;
 
 var toolbox;
 var tool;
@@ -21,6 +22,12 @@ function init(size, elementId) {
 		colors.className = color();
 	});
 	tool = toolbox.querySelector('#tool');
+	toolbox.querySelector('#scatter').addEventListener('click', function() {
+		var constellation = Constellation.random(size);
+		for(var i = 0; i < size; i++) {
+			console.log(constellation[i].map(function(x) {return x ? '*' : ' ';}).join('|'));
+		}
+	});
 }
 
 function get() {