import { pick } from 'frptools';

import { isObject } from './comparators';

export function bufferToHexString(buffer) {
	const hexCodes = [];
	const view = new DataView(buffer);

	for (let i = 0; i < view.byteLength; i += 4) {
		// Using getUint32 reduces the number of iterations needed (we process 4 bytes each time)
		const value = view.getUint32(i);
		// toString(16) will give the hex representation of the number without padding
		// We use concatenation and slice for padding
		hexCodes.push(`00000000${value.toString(16)}`.slice(-8));
	}

	// Join all the hex strings into one
	return hexCodes.join('');
}

export function blobToArrayBuffer(blob) {
	return new Promise((resolve, reject) => {
		const f = new FileReader();
		f.onload = _ => resolve(f.result);
		f.readAsArrayBuffer(blob);
	});
}

export function blobToString(blob) {
	return new Promise((resolve, reject) => {
		const f = new FileReader();
		f.onload = _ => resolve(f.result);
		f.readAsText(blob);
	});
}

export const arrayHashWrapper = hash => arr => (Array.isArray(arr) ? arr.map(hash).join('?') : arr);

export function pouchDocHash(d) {
	return isObject(d) ? `${d._id}:${d._rev}` : d;
}

export const pouchDocArrayHash = arrayHashWrapper(pouchDocHash);

export function deepAssign(to, ...rest) {
	for (let src of rest) {
		for (let prop in src) {
			const value = src[prop];
			if (typeof value === 'object' && !Array.isArray(value)) {
				to[prop] = deepAssign(to[prop] || {}, value);
			} else if (value === undefined && to[prop] !== undefined) {
				delete to[prop];
			} else {
				to[prop] = value;
			}
		}
	}
	return to;
}

export const sum = arr => arr.reduce((acc, i) => acc + i, 0);

export const extractID = pick('_id');
export const extractREV = pick('_rev');

export function hashSet(_a) {
	if (_a instanceof Set) {
		return Array.from(_a.keys())
			.sort()
			.map(k => `${(typeof k).substr(0, 1)}:${encodeURIComponent(k)}/`)
			.join('?');
	}
	return _a;
}