Constellations/js/Solver/SingleCell.js

import * as CellSet from Geometry.CellSet;
import * as Strategy from Solver.Strategy;
import * as State from Solver.State;
import {diagonal, getColumn, getRow, plus} from Geometry.Vector;

return {
	find: find,
	getRange: getRange
};

function find(solvingState) {
	return Strategy.tryEach(
		State.zoneNames(solvingState).map(function(name) {
			return Strategy.map(
				stepOfCell(solvingState, name),
				Strategy.tryEach(solvingState.zones[name].map(getSingleCellIn))
			);
		})
	);
}

function getSingleCellIn(cellSet) {
	return function() {
		if(cellSet.size() == 1) {
			return cellSet.toList()[0];
		}
	};
}

function stepOfCell(solvingState, name) {
	return function(cell) {
		return {
			reason: 'singleCell',
			set: name,
			empty: getRange(solvingState, cell),
			star: new CellSet.CellSet(cell)
		};
	};
}

function getRange(solvingState, cell) {
	var union = CellSet.union([
		solvingState.zones.colors[solvingState.getColor(cell)],
		solvingState.zones.rows[getRow(cell)],
		solvingState.zones.columns[getColumn(cell)],
		CellSet.rectangle(plus(cell, diagonal(-1)), diagonal(3))
			.intersection(solvingState.missing)
	]);
	union.remove(cell);
	return union;
}