import CellSet;

return {
	step: step
};

function step(grid) {
	var zones = getZones(grid);
	var lines = getLines(grid.length);
	var rowClusters = checkRowsInclusions(grid);
	if(rowClusters.length > 0) {
		rowClusters.forEach(function(rowCluster) {
			rowCluster.toClear = difference(
				rowCluster.colors.map(function(color) {return zones[color];}),
				rowCluster.rows.map(function(row) {return lines.rows[row];})
			);
		});
	}
	return rowClusters;
}

function getZones(grid) {
	var zones = {};
	for(var row = 0; row < grid.length; row++) {
		for(var column = 0; column < grid[row].length; column++) {
			var color = grid[row][column];
			if(zones[color] == undefined) {
				zones[color] = CellSet.make(
					{type: 'isochrome', row: row, column: column, grid: grid}
				);
			}
		}
	}
	return zones;
}

function line(type, size, i) {
	if(type == 'row') {
		return CellSet.make(
			{type: 'rectangle', row: i, column: 0, width: size, height: 1}
		);
	} else if(type == 'column') {
		return CellSet.make(
			{type: 'rectangle', row: 0, column: i, width: 1, height: size}
		);
	}
}

function getLines(size) {
	var empty = Array.from({length: size});
	return {
		rows: empty.map(function(x, i) {return line('row', size, i);}),
		columns: empty.map(function(x, i) {return line('column', size, i);}),
	};
}

function getColorsByRow(grid) {
	var colorsByRow = [];
	for(var row = 0; row < grid.length; row++) {
		colorsByRow.push(
			quotient(grid[row], function(c0, c1) {return c0 == c1;}).map(
				function(colorClass) {return colorClass.specimen;}
			)
		);
	}
	return colorsByRow;
}

function checkRowsInclusions(grid) {
	var colorsByRow = getColorsByRow(grid);
	var colorSets = quotient(colorsByRow, sameColorsSet);
	return colorSets.reduce(function(commands, colorSet) {
		if(colorSet.occurrences.length == colorSet.specimen.length) {
			commands.push({
				reason: 'rowsInColors',
				rows: colorSet.occurrences,
				colors: colorSet.specimen
			});
		}
		return commands;
	}, []);
}

function quotient(elements, equivalence) {
	var classes = [];
	elements.forEach(function(element, i) {
		for(var c = 0; c < classes.length; c++) {
			if(equivalence(element, classes[c].specimen)) {
				classes[c].occurrences.push(i);
				return;
			}
		}
		classes.push({specimen: element, occurrences: [i]});
	});
	return classes;
}

function sameColorsSet(s0, s1) {
	if(s0.length != s1.length) {
		return false;
	}
	var o0 = {};
	s0.forEach(function(x) {o0[x] = true;});
	for(var i = 0; i < s1.length; i++) {
		if(!o0[s1[i]]) {
			return false;
		}
	}
	return true;
}

function difference(setsFrom, setsSubstracted) {
	return CellSet.union(setsFrom).difference(CellSet.union(setsSubstracted));
}