export class InterInterpolant {
	parameterPositions: any;
	_cachedIndex: number;
	resultBuffer: any;
	sampleValues: any;
	valueSize: any;
	constructor(parameterPositions, sampleValues, sampleSize, resultBuffer) {
		this.parameterPositions = parameterPositions;
		this._cachedIndex = 0;

		this.resultBuffer = resultBuffer !== undefined ?
			resultBuffer : new sampleValues.constructor(sampleSize);
		this.sampleValues = sampleValues;
		this.valueSize = sampleSize;
	}
	evaluate(t) {
		var pp = this.parameterPositions,
			i1 = this._cachedIndex,

			t1 = pp[i1],
			t0 = pp[i1 - 1];

		validate_interval: {

			seek: {

				var right;

				linear_scan: {

					//- See http://jsperf.com/comparison-to-undefined/3
					//- slower code:
					//-
					//- 				if ( t >= t1 || t1 === undefined ) {
					forward_scan: if (!(t < t1)) {

						for (var giveUpAt = i1 + 2; ;) {

							if (t1 === undefined) {

								if (t < t0) break forward_scan;

								// after end

								i1 = pp.length;
								this._cachedIndex = i1;
								return this.afterEnd_(i1 - 1/*, t, t0*/);

							}

							if (i1 === giveUpAt) break; // this loop

							t0 = t1;
							t1 = pp[++i1];

							if (t < t1) {

								// we have arrived at the sought interval
								break seek;

							}

						}

						// prepare binary search on the right side of the index
						right = pp.length;
						break linear_scan;

					}

					//- slower code:
					//-					if ( t < t0 || t0 === undefined ) {
					if (!(t >= t0)) {

						// looping?

						var t1global = pp[1];

						if (t < t1global) {

							i1 = 2; // + 1, using the scan for the details
							t0 = t1global;

						}

						// linear reverse scan

						for (var giveUpAt = i1 - 2; ;) {

							if (t0 === undefined) {

								// before start

								this._cachedIndex = 0;
								return this.beforeStart_(0/*, t, t1*/);

							}

							if (i1 === giveUpAt) break; // this loop

							t1 = t0;
							t0 = pp[--i1 - 1];

							if (t >= t0) {

								// we have arrived at the sought interval
								break seek;

							}

						}

						// prepare binary search on the left side of the index
						right = i1;
						i1 = 0;
						break linear_scan;

					}

					// the interval is valid

					break validate_interval;

				} // linear scan

				// binary search

				while (i1 < right) {

					var mid = (i1 + right) >>> 1;

					if (t < pp[mid]) {

						right = mid;

					} else {

						i1 = mid + 1;

					}

				}

				t1 = pp[i1];
				t0 = pp[i1 - 1];

				// check boundary cases, again

				if (t0 === undefined) {

					this._cachedIndex = 0;
					return this.beforeStart_(0/*, t, t1*/);

				}

				if (t1 === undefined) {

					i1 = pp.length;
					this._cachedIndex = i1;
					return this.afterEnd_(i1 - 1/*, t0, t*/);

				}

			} // seek

			this._cachedIndex = i1;

			this.intervalChanged_(i1, t0, t1);

		} // validate_interval

		return this.interpolate_(i1, t0, t, t1);

	}
	settings = null;
	DefaultSettings_ = {};
	getSettings_() {

		return this.settings || this.DefaultSettings_;

	};

	copySampleValue_(index) {

		// copies a sample value to the result buffer

		var result = this.resultBuffer,
			values = this.sampleValues,
			stride = this.valueSize,
			offset = index * stride;

		for (var i = 0; i !== stride; ++i) {

			result[i] = values[offset + i];

		}

		return result;

	};

	// Template methods for derived classes:

	interpolate_(i1, t0, t, t1) {

		throw new Error('call to abstract method');
		// implementations shall return this.resultBuffer

	};

	intervalChanged_(i1, t0, t1) {

		// empty

	}
	beforeStart_ = this.copySampleValue_;

	//( N-1, tN-1, t ), returns this.resultBuffer
	afterEnd_ = this.copySampleValue_;
}
