import std.algorithm, std.conv, std.datetime, std.file, std.json;
import std.stdio, core.thread;
import progress, onedrive, util;
static import log;

private long fragmentSize = 10 * 2^^20; // 10 MiB

struct UploadSession
{
	private OneDriveApi onedrive;
	private bool verbose;
	// https://dev.onedrive.com/resources/uploadSession.htm
	private JSONValue session;
	// path where to save the session
	private string sessionFilePath;

	this(OneDriveApi onedrive, string sessionFilePath)
	{
		assert(onedrive);
		this.onedrive = onedrive;
		this.sessionFilePath = sessionFilePath;
		this.verbose = verbose;
	}

	JSONValue upload(string localPath, const(char)[] parentDriveId, const(char)[] parentId, const(char)[] filename, const(char)[] eTag = null)
	{
		// Fix https://github.com/abraunegg/onedrive/issues/2
		// More Details https://github.com/OneDrive/onedrive-api-docs/issues/778
		
		SysTime localFileLastModifiedTime = timeLastModified(localPath).toUTC();
		localFileLastModifiedTime.fracSecs = Duration.zero;
		
		JSONValue fileSystemInfo = [
				"item": JSONValue([
					"@name.conflictBehavior": JSONValue("replace"),
					"fileSystemInfo": JSONValue([
						"lastModifiedDateTime": localFileLastModifiedTime.toISOExtString()
					])
				])
			];
		
		session = onedrive.createUploadSession(parentDriveId, parentId, filename, eTag, fileSystemInfo);
		session["localPath"] = localPath;
		save();
		return upload();
	}

	/* Restore the previous upload session.
	 * Returns true if the session is valid. Call upload() to resume it.
	 * Returns false if there is no session or the session is expired. */
	bool restore()
	{
		if (exists(sessionFilePath)) {
			log.vlog("Trying to restore the upload session ...");
			session = readText(sessionFilePath).parseJSON();
			
			// Check the session resume file for expirationDateTime
			if ("expirationDateTime" in session){
				// expirationDateTime in the file
				auto expiration =  SysTime.fromISOExtString(session["expirationDateTime"].str);
				if (expiration < Clock.currTime()) {
					log.vlog("The upload session is expired");
					return false;
				}
				if (!exists(session["localPath"].str)) {
					log.vlog("The file does not exist anymore");
					return false;
				}
				// Can we read the file - as a permissions issue or file corruption will cause a failure on resume
				// https://github.com/abraunegg/onedrive/issues/113
				if (readLocalFile(session["localPath"].str)){
					// able to read the file
					// request the session status
					JSONValue response;
					try {
						response = onedrive.requestUploadStatus(session["uploadUrl"].str);
					} catch (OneDriveException e) {
						// handle any onedrive error response
						if (e.httpStatusCode == 400) {
							log.vlog("Upload session not found");
							return false;
						} else {
							throw e;
						}
					}
					
					// do we have a valid response from OneDrive?
					if (response.object()){
						// JSON object
						if (("expirationDateTime" in response) && ("nextExpectedRanges" in response)){
							// has the elements we need
							session["expirationDateTime"] = response["expirationDateTime"];
							session["nextExpectedRanges"] = response["nextExpectedRanges"];
							if (session["nextExpectedRanges"].array.length == 0) {
								log.vlog("The upload session is completed");
								return false;
							}
						} else {
							// bad data
							log.vlog("Restore file upload session failed - invalid data response from OneDrive");
							if (exists(sessionFilePath)) {
								remove(sessionFilePath);
							}
							return false;
						}
					} else {
						// not a JSON object
						log.vlog("Restore file upload session failed - invalid response from OneDrive");
						if (exists(sessionFilePath)) {
							remove(sessionFilePath);
						}
						return false;
					}
					return true;
				} else {
					// unable to read the local file
					log.vlog("Restore file upload session failed - unable to read the local file");
					if (exists(sessionFilePath)) {
						remove(sessionFilePath);
					}
					return false;
				}
			} else {
				// session file contains an error - cant resume
				log.vlog("Restore file upload session failed - cleaning up session resume");
				if (exists(sessionFilePath)) {
					remove(sessionFilePath);
				}
				return false;
			}
		}
		return false;
	}

	JSONValue upload()
	{
		long offset;
		long fileSize;
		
		if ("nextExpectedRanges" in session){
			offset = session["nextExpectedRanges"][0].str.splitter('-').front.to!long;
		}
		
		if ("localPath" in session){
			fileSize = getSize(session["localPath"].str);
		}
		
		// Upload Progress Bar
		size_t iteration = (roundTo!int(double(fileSize)/double(fragmentSize)))+1;
		Progress p = new Progress(iteration);
		p.title = "Uploading";
				
		JSONValue response;
		while (true) {
			p.next();
			long fragSize = fragmentSize < fileSize - offset ? fragmentSize : fileSize - offset;
			// If the resume upload fails, we need to check for a return code here
			try {
				response = onedrive.uploadFragment(
					session["uploadUrl"].str,
					session["localPath"].str,
					offset,
					fragSize,
					fileSize
				);
				offset += fragmentSize;
				if (offset >= fileSize) break;
				// update the session details
				session["expirationDateTime"] = response["expirationDateTime"];
				session["nextExpectedRanges"] = response["nextExpectedRanges"];
				save();
			} catch (OneDriveException e) {
				// there was an error remove session file
				if (exists(sessionFilePath)) {
					remove(sessionFilePath);
				}
				return response;
			}
		}
		// upload complete
		p.next();
		writeln();
		if (exists(sessionFilePath)) {
			remove(sessionFilePath);
		}
		return response;
	}

	private void save()
	{
		std.file.write(sessionFilePath, session.toString());
	}
}