package net.mindoverflow.webmarker.webserver.controllers;

import com.auth0.jwt.JWT;
import com.auth0.jwt.JWTVerifier;
import com.auth0.jwt.algorithms.Algorithm;
import com.auth0.jwt.exceptions.JWTVerificationException;
import com.auth0.jwt.interfaces.Claim;
import com.auth0.jwt.interfaces.DecodedJWT;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import net.mindoverflow.webmarker.utils.FileUtils;
import net.mindoverflow.webmarker.utils.config.ConfigEntries;
import net.mindoverflow.webmarker.utils.security.SafetyCheck;
import net.mindoverflow.webmarker.utils.sql.MarkerSQLUtils;
import ro.pippo.controller.Controller;
import ro.pippo.controller.POST;
import ro.pippo.controller.Path;
import ro.pippo.core.route.RouteContext;

import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.time.*;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;
import java.util.UUID;

@Path("/api/v1/store")
public class StorageController extends Controller
{

    private RouteContext routeContext;

    @POST
    public void store()
    {
        // Load RouteContext
        routeContext = getRouteContext();

        // Load JSON object from body
        String body = routeContext.getRequest().getBody();
        JsonObject jsonObject = FileUtils.stringToJson(body);

        // Load JWT element
        JsonElement jwtElement = getJwtFromJson(jsonObject);
        if(jwtElement == null) return;

        // Decrypt/Verify JWT
        DecodedJWT jwt = decryptAndVerifyJwt(jwtElement);
        if(jwt == null) return;

        // Load username from JWT
        String username = getFromJwt(jwt, "username");
        if(username == null) return;

        // Check some stuff about the user
        if(!usernameCheckPassed(username)) return;

        // Load UUID from username
        UUID uuid = MarkerSQLUtils.getUserUUID(username);
        if(uuid == null)
        {
            routeContext.send("Server error: missing UUID!");
            return;
        }

        // Load url from Json body
        String url = getFromJson(jsonObject, "url");
        if(url == null) return;

        // Verify url validity
        URI confirmedUrl = stringToURI(url);
        if(confirmedUrl == null) return;

        // Load ZonedDateTime from Json body
        String zonedDateTimeStr = getFromJson(jsonObject, "timestamp");
        if(zonedDateTimeStr == null) return;

        // Transform String to ZonedDateTime
        ZonedDateTime timestamp = stringToZDT(zonedDateTimeStr);
        if(timestamp == null) return;
        System.out.println("Zoned Timestamp: " + timestamp.toString());

        // Check if the timestamp is too old to be true
        ZonedDateTime now = ZonedDateTime.now();
        System.out.println("NOW Timestamp: " + now.toString());
        if(!dateCheckPassed(timestamp, now)) return;

        // Transform whatever GMT it's on to GMT+0
        LocalDateTime timestampUTC = LocalDateTime.ofInstant(timestamp.toInstant(), ZoneOffset.UTC);
        System.out.println("UTC Timestamp: " + timestampUTC.toString());

        MarkerSQLUtils.addHistoryRecord(uuid, confirmedUrl.toString(), timestampUTC);
        routeContext.send("OK!");

    }

    // todo: move to safety class?
    private boolean dateCheckPassed(ZonedDateTime timestamp, ZonedDateTime now)
    {
        // allow up to 5 minutes in the past and 1 minute in the future
        //if(ChronoUnit.MINUTES.between(timestamp, now) > 5) todo: decide
        if(Duration.between(timestamp, now).getSeconds() >= 5 * 60
        || Duration.between(timestamp, now).getSeconds() <= -1 * 60)
        {
            routeContext.send("Timestamp out of sync!");
            return false;
        }
        return true;
    }

    private JsonElement getJwtFromJson(JsonObject jsonObject)
    {
        JsonElement jwtElement = jsonObject.get("jwt");
        if(jwtElement == null || jwtElement.isJsonNull())
        {
            routeContext.send("Invalid JWT!"); //todo: throw exception instead?
            return null;
        }
        return jwtElement;
    }

    private DecodedJWT decryptAndVerifyJwt(JsonElement jwtElement)
    {
        String token = jwtElement.getAsString();

        try {
            Algorithm algorithm = Algorithm.HMAC256((String) ConfigEntries.JWT_SECRET.getValue());
            JWTVerifier jwtVerifier = JWT.require(algorithm)
                    .build();

            return jwtVerifier.verify(token);
        }
        catch (JWTVerificationException e)
        {
            routeContext.send("Invalid JWT!");
            return null;
        }
    }

    private String getFromJwt(DecodedJWT jwt, String claimName)
    {
        Claim claim = jwt.getClaim(claimName);
        if(claim == null || claim.isNull())
        {
            routeContext.send("JWT missing '" + claimName + "' claim!");
            return null;
        }

        return claim.asString();
    }

    // todo: move to safety class?
    private boolean usernameCheckPassed(String username)
    {
        if(!SafetyCheck.isSafeUsername(username))
        {
            routeContext.send("Invalid username!");
            return false;
        }

        if(!MarkerSQLUtils.userExists(username))
        {
            routeContext.send("User does not exist!");
            return false;
        }

        return true;
    }

    private String getFromJson(JsonObject jsonObject, String name)
    {

        JsonElement jsonElement = jsonObject.get(name);
        if(jsonElement == null || jsonElement.isJsonNull())
        {
            routeContext.send("JSON body missing '" + name + "' entry!");
            return null;
        }

        return jsonElement.getAsString();
    }

    private URI stringToURI(String url)
    {
        try {
            return new URL(url).toURI();
        } catch (URISyntaxException e) {
            routeContext.send("Invalid URI!");
        }
        catch (MalformedURLException e) {
            routeContext.send("Invalid URL!");
        }

        return null;
    }

    private ZonedDateTime stringToZDT(String timestamp)
    {
        DateTimeFormatter formatter = DateTimeFormatter.ISO_OFFSET_DATE_TIME;
        return ZonedDateTime.parse(timestamp, formatter);
        // todo: error check
    }
}