/**
* implement some useful random-function
*/



/**
 * generates a random integer in [{@param inclusiveMin}; {@param exclusiveMax}).
 *
 * @param inclusiveMin {number}
 * @param exclusiveMax {number}
 *
 * @return {number} a random integer in [{@param inclusiveMin}; {@param exclusiveMax}).
 *
 */
export function uniform(inclusiveMin= 0, exclusiveMax) {
	let a = inclusiveMin,
		b = exclusiveMax;
	if (arguments.length === 1) { // only the first is set => there is no left bound
		a = 0;
		b = inclusiveMin;
	}
	if ( (b <= a) || (b-a) >= Number.MAX_VALUE ) {
		throw Error(`bad range [${a}, ${b})`)
	}
	return a + (Math.floor( (b-a)*Math.random() ));
}


/**
 * generates a random discrete distribution of a given probability of distribution
 * For example: given a probability of `[0.1, 0.3, 0.6]`, then the random generate number ist
 * one of 0 (with probability of 1%) , 1 (30%) and 2(60%).
 *
 * @param distribution {Array} an array of number, sum of its element must be at most 1
 * @return {number} an integer between 0 (include) and {@param distribution.length} (exclude)
 *
 * */
export function discrete(distribution) {
	let sum = distribution.reduce( (acc,current) => acc + current);
	let dist = undefined;
	if(sum > 1) {
		throw Error(`bad distribution [${distribution}]`);
	} else if (sum < 1) {
		dist = [...distribution, 1 - sum];
	} else {
		dist = [...distribution];
	}
	let r = Math.random();
	let i = 0;
	let acc = dist[0];
	while(r >=acc ) {
		++i;
		acc += dist[i];
	}
	return i;
}