import * as Strategy from Solver.Strategy;
import {diagonal, plus} from Geometry.Vector;

return {
	find: find
};

function find(zones, lines) {
	var cellSets = zones.concat(lines.rows).concat(lines.columns);
	return Strategy.map(
		stepOfCell(cellSets),
		Strategy.tryEach(cellSets.map(getSingleCellIn))
	);
}

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

function stepOfCell(cellSets) {
	return function(cell) {
		return {
			reason: 'singleCell',
			empty: toEmpty(cell).intersection(cellSets),
			star: CellSet.cells([cell])
		};
	};
}

function toEmpty(cell) {
	var around = CellSet.rectangle(plus(cell, diagonal(-1)), diagonal(2));
	around.remove(v);
	return CellSet.union([
		around,
		CellSet.row(v.getRow()),
		CellSet.column(v.getColumn())
	]);
}