ActivityReporter.swift

//
//  ActivityReporter.swift
//  C3PRO
//
//  Created by Pascal Pfiffner on 15/07/16.
//  Copyright © 2016 University Hospital Zurich. All rights reserved.
//
//  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
//

import Foundation
import SMART


/**
Protocol to which activity reporters/collectors should adhere.

See [HealthKit/README.md](https://github.com/C3-PRO/c3-pro-ios-framework/tree/master/Sources/HealthKit#activity-reporter) for detailed instructions.
*/
public protocol ActivityReporter {
	
	/**
	Retrieve activities performed between two given dates.
	
	- parameter startingAt: The start date
	- parameter until:      The end date
	- parameter callback:   The callback to call when all activities have been retrieved
	*/
	func reportForActivityPeriod(startingAt start: Date, until: Date, callback: @escaping ((ActivityReportPeriod?, Error?) -> Void))
	
	/**
	Retrieve activity data with progressively increasing time intervals (1 day -> 1 month) up until today.
	
	- parameter callback: The callback to call when all activities have been retrieved
	*/
	func progressivelyCollatedActivityData(callback: @escaping ((ActivityReport, Error?) -> Void))
}


extension ActivityReporter {
	
	/**
	Will retrieve activity data with progressively increasing time intervals (1 day -> 1 month).
	*/
	public func progressivelyCollatedActivityData(callback: @escaping ((ActivityReport, Error?) -> Void)) {
		let queue = DispatchQueue(label: "org.chip.c3-pro.activity-reporter-queue")
		queue.async {
			var calendar = Calendar.current
			calendar.timeZone = TimeZone(abbreviation: "UTC")!    // use UTC
			let intervals = calendar.c3_reverseProgressiveDateComponentsSinceToday()
			var errors = [Error]()
			
			// sample all intervals
			var periods = [ActivityReportPeriod]()
			for (from, to, numDays, name) in intervals {
				let start = calendar.date(from: from) ?? Date()
				let end = calendar.date(from: to) ?? Date()
				let semaphore = DispatchSemaphore(value: 0)
				self.reportForActivityPeriod(startingAt: start, until: end) { period, error in
					if let period = period {
						period.humanPeriod = name
						period.numberOfDays = numDays
						periods.append(period)
					}
					if let error = error {
						errors.append(error)
					}
					semaphore.signal()
				}
				semaphore.wait()
			}
			
			// all intervals collected, order and return
			let report = ActivityReport(periods: periods)
			c3_performOnMainQueue() {
				callback(report, (errors.count > 0) ? C3Error.multipleErrors(errors) : nil)
			}
		}
	}
}