//
//  OPMLFile.swift
//  Account
//
//  Created by Maurice Parker on 9/12/19.
//  Copyright © 2019 Ranchero Software, LLC. All rights reserved.
//

import Foundation
import os.log
import RSCore
import RSParser

final class OPMLFile {
	
	private var log = OSLog(subsystem: Bundle.main.bundleIdentifier!, category: "opmlFile")

	private let fileURL: URL
	private let account: Account
	private lazy var managedFile = ManagedResourceFile(fileURL: fileURL, load: loadCallback, save: saveCallback)
	
	init(filename: String, account: Account) {
		self.fileURL = URL(fileURLWithPath: filename)
		self.account = account
	}
	
	func markAsDirty() {
		managedFile.markAsDirty()
	}
	
	func load() {
		managedFile.load()
	}
	
	func save() {
		managedFile.saveIfNecessary()
	}
	
	func suspend() {
		managedFile.suspend()
	}
	
	func resume() {
		managedFile.resume()
	}
	
}

private extension OPMLFile {

	func loadCallback() {
		guard let opmlItems = parsedOPMLItems() else { return }
		BatchUpdate.shared.perform {
			account.topLevelWebFeeds.removeAll()
			account.loadOPMLItems(opmlItems, parentFolder: nil)
		}
	}
	
	func saveCallback() {
		guard !account.isDeleted else { return }
		
		let opmlDocumentString = opmlDocument()
		
		let errorPointer: NSErrorPointer = nil
		let fileCoordinator = NSFileCoordinator(filePresenter: managedFile)
		
		fileCoordinator.coordinate(writingItemAt: fileURL, options: [], error: errorPointer, byAccessor: { writeURL in
			do {
				try opmlDocumentString.write(to: writeURL, atomically: true, encoding: .utf8)
			} catch let error as NSError {
				os_log(.error, log: log, "OPML save to disk failed: %@.", error.localizedDescription)
			}
		})
		
		if let error = errorPointer?.pointee {
			os_log(.error, log: log, "OPML save to disk coordination failed: %@.", error.localizedDescription)
		}
	}
	
	func parsedOPMLItems() -> [RSOPMLItem]? {

		var fileData: Data? = nil
		let errorPointer: NSErrorPointer = nil
		let fileCoordinator = NSFileCoordinator(filePresenter: managedFile)
		
		fileCoordinator.coordinate(readingItemAt: fileURL, options: [], error: errorPointer, byAccessor: { readURL in
			do {
				fileData = try Data(contentsOf: readURL)
			} catch {
				// Commented out because it’s not an error on first run.
				// TODO: make it so we know if it’s first run or not.
				//NSApplication.shared.presentError(error)
				os_log(.error, log: log, "OPML read from disk failed: %@.", error.localizedDescription)
			}
		})
		
		if let error = errorPointer?.pointee {
			os_log(.error, log: log, "OPML read from disk coordination failed: %@.", error.localizedDescription)
		}

		guard let opmlData = fileData else {
			return nil
		}

		let parserData = ParserData(url: fileURL.absoluteString, data: opmlData)
		var opmlDocument: RSOPMLDocument?

		do {
			opmlDocument = try RSOPMLParser.parseOPML(with: parserData)
		} catch {
			os_log(.error, log: log, "OPML Import failed: %@.", error.localizedDescription)
			return nil
		}
		
		return opmlDocument?.children
		
	}
	
	func opmlDocument() -> String {
		let escapedTitle = account.nameForDisplay.rs_stringByEscapingSpecialXMLCharacters()
		let openingText =
		"""
		<?xml version="1.0" encoding="UTF-8"?>
		<!-- OPML generated by NetNewsWire -->
		<opml version="1.1">
		<head>
		<title>\(escapedTitle)</title>
		</head>
		<body>

		"""

		let middleText = account.OPMLString(indentLevel: 0, strictConformance: false)

		let closingText =
		"""
				</body>
			</opml>
			"""

		let opml = openingText + middleText + closingText
		return opml
	}
	
}
