import { Quaternion } from '../math/Quaternion.js';

class PropertyMixer {
	constructor(binding, typeName, valueSize) {
		this.binding = binding;
		this.valueSize = valueSize;

		let mixFunction, mixFunctionAdditive, setIdentity;

		// buffer layout: [ incoming | accu0 | accu1 | orig | addAccu | (optional work) ]
		//
		// interpolators can use .buffer as their .result
		// the data then goes to 'incoming'
		//
		// 'accu0' and 'accu1' are used frame-interleaved for
		// the cumulative result and are compared to detect
		// changes
		//
		// 'orig' stores the original state of the property
		//
		// 'add' is used for additive cumulative results
		//
		// 'work' is optional and is only present for quaternion types. It is used
		// to store intermediate quaternion multiplication results

		switch (typeName) {
			case 'quaternion':
				mixFunction = this._slerp;
				mixFunctionAdditive = this._slerpAdditive;
				setIdentity = this._setAdditiveIdentityQuaternion;

				this.buffer = new Float64Array(valueSize * 6);
				this._workIndex = 5;
				break;

			case 'string':
			case 'bool':
				mixFunction = this._select;

				// Use the regular mix function and for additive on these types,
				// additive is not relevant for non-numeric types
				mixFunctionAdditive = this._select;

				setIdentity = this._setAdditiveIdentityOther;

				this.buffer = new Array(valueSize * 5);
				break;

			default:
				mixFunction = this._lerp;
				mixFunctionAdditive = this._lerpAdditive;
				setIdentity = this._setAdditiveIdentityNumeric;

				this.buffer = new Float64Array(valueSize * 5);
		}

		this._mixBufferRegion = mixFunction;
		this._mixBufferRegionAdditive = mixFunctionAdditive;
		this._setIdentity = setIdentity;
		this._origIndex = 3;
		this._addIndex = 4;

		this.cumulativeWeight = 0;
		this.cumulativeWeightAdditive = 0;

		this.useCount = 0;
		this.referenceCount = 0;
	}

	// accumulate data in the 'incoming' region into 'accu<i>'
	accumulate(accuIndex, weight) {
		// note: happily accumulating nothing when weight = 0, the caller knows
		// the weight and shouldn't have made the call in the first place

		const buffer = this.buffer,
			stride = this.valueSize,
			offset = accuIndex * stride + stride;

		let currentWeight = this.cumulativeWeight;

		if (currentWeight === 0) {
			// accuN := incoming * weight

			for (let i = 0; i !== stride; ++i) {
				buffer[offset + i] = buffer[i];
			}

			currentWeight = weight;
		} else {
			// accuN := accuN + incoming * weight

			currentWeight += weight;
			const mix = weight / currentWeight;
			this._mixBufferRegion(buffer, offset, 0, mix, stride);
		}

		this.cumulativeWeight = currentWeight;
	}

	// accumulate data in the 'incoming' region into 'add'
	accumulateAdditive(weight) {
		const buffer = this.buffer,
			stride = this.valueSize,
			offset = stride * this._addIndex;

		if (this.cumulativeWeightAdditive === 0) {
			// add = identity

			this._setIdentity();
		}

		// add := add + incoming * weight

		this._mixBufferRegionAdditive(buffer, offset, 0, weight, stride);
		this.cumulativeWeightAdditive += weight;
	}

	// apply the state of 'accu<i>' to the binding when accus differ
	apply(accuIndex) {
		const stride = this.valueSize,
			buffer = this.buffer,
			offset = accuIndex * stride + stride,
			weight = this.cumulativeWeight,
			weightAdditive = this.cumulativeWeightAdditive,
			binding = this.binding;

		this.cumulativeWeight = 0;
		this.cumulativeWeightAdditive = 0;

		if (weight < 1) {
			// accuN := accuN + original * ( 1 - cumulativeWeight )

			const originalValueOffset = stride * this._origIndex;

			this._mixBufferRegion(buffer, offset, originalValueOffset, 1 - weight, stride);
		}

		if (weightAdditive > 0) {
			// accuN := accuN + additive accuN

			this._mixBufferRegionAdditive(buffer, offset, this._addIndex * stride, 1, stride);
		}

		for (let i = stride, e = stride + stride; i !== e; ++i) {
			if (buffer[i] !== buffer[i + stride]) {
				// value has changed -> update scene graph

				binding.setValue(buffer, offset);
				break;
			}
		}
	}

	// remember the state of the bound property and copy it to both accus
	saveOriginalState() {
		const binding = this.binding;

		const buffer = this.buffer,
			stride = this.valueSize,
			originalValueOffset = stride * this._origIndex;

		binding.getValue(buffer, originalValueOffset);

		// accu[0..1] := orig -- initially detect changes against the original
		for (let i = stride, e = originalValueOffset; i !== e; ++i) {
			buffer[i] = buffer[originalValueOffset + (i % stride)];
		}

		// Add to identity for additive
		this._setIdentity();

		this.cumulativeWeight = 0;
		this.cumulativeWeightAdditive = 0;
	}

	// apply the state previously taken via 'saveOriginalState' to the binding
	restoreOriginalState() {
		const originalValueOffset = this.valueSize * 3;
		this.binding.setValue(this.buffer, originalValueOffset);
	}

	_setAdditiveIdentityNumeric() {
		const startIndex = this._addIndex * this.valueSize;
		const endIndex = startIndex + this.valueSize;

		for (let i = startIndex; i < endIndex; i++) {
			this.buffer[i] = 0;
		}
	}

	_setAdditiveIdentityQuaternion() {
		this._setAdditiveIdentityNumeric();
		this.buffer[this._addIndex * this.valueSize + 3] = 1;
	}

	_setAdditiveIdentityOther() {
		const startIndex = this._origIndex * this.valueSize;
		const targetIndex = this._addIndex * this.valueSize;

		for (let i = 0; i < this.valueSize; i++) {
			this.buffer[targetIndex + i] = this.buffer[startIndex + i];
		}
	}

	// mix functions

	_select(buffer, dstOffset, srcOffset, t, stride) {
		if (t >= 0.5) {
			for (let i = 0; i !== stride; ++i) {
				buffer[dstOffset + i] = buffer[srcOffset + i];
			}
		}
	}

	_slerp(buffer, dstOffset, srcOffset, t) {
		Quaternion.slerpFlat(buffer, dstOffset, buffer, dstOffset, buffer, srcOffset, t);
	}

	_slerpAdditive(buffer, dstOffset, srcOffset, t, stride) {
		const workOffset = this._workIndex * stride;

		// Store result in intermediate buffer offset
		Quaternion.multiplyQuaternionsFlat(buffer, workOffset, buffer, dstOffset, buffer, srcOffset);

		// Slerp to the intermediate result
		Quaternion.slerpFlat(buffer, dstOffset, buffer, dstOffset, buffer, workOffset, t);
	}

	_lerp(buffer, dstOffset, srcOffset, t, stride) {
		const s = 1 - t;

		for (let i = 0; i !== stride; ++i) {
			const j = dstOffset + i;

			buffer[j] = buffer[j] * s + buffer[srcOffset + i] * t;
		}
	}

	_lerpAdditive(buffer, dstOffset, srcOffset, t, stride) {
		for (let i = 0; i !== stride; ++i) {
			const j = dstOffset + i;

			buffer[j] = buffer[j] + buffer[srcOffset + i] * t;
		}
	}
}

export { PropertyMixer };