DiscordDB.java

import com.mewna.catnip.Catnip;
import com.mewna.catnip.shard.DiscordEvent;
import io.vertx.core.json.DecodeException;
import io.vertx.core.json.JsonObject;

import javax.annotation.CheckReturnValue;
import javax.annotation.Nonnull;
import java.util.HashMap;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;

public class DiscordDB {
    private final Map<String, String> tableMap = new HashMap<>();
    private final Map<String, String> revTableMap = new HashMap<>();
    private final Catnip catnip;
    
    public DiscordDB(@Nonnull final Catnip catnip, @Nonnull final String dbGuildId) {
        this.catnip = catnip;
        catnip.rest().guild().getGuildChannels(dbGuildId).thenAccept(channels -> {
            channels.forEach(c -> {
                if(c.isText()) {
                    tableMap.put(c.asTextChannel().name(), c.id());
                    revTableMap.put(c.id(), c.asTextChannel().name());
                }
            });
        });
        catnip.on(DiscordEvent.CHANNEL_CREATE, channel -> {
            if(!channel.isText() || !channel.asTextChannel().guildId().equals(dbGuildId)) {
                return;
            }
            tableMap.put(channel.asTextChannel().name(), channel.id());
            revTableMap.put(channel.id(), channel.asTextChannel().name());
        });
        catnip.on(DiscordEvent.CHANNEL_DELETE, channel -> {
            if(!channel.isText() || !channel.asTextChannel().guildId().equals(dbGuildId)) {
                return;
            }
            tableMap.remove(revTableMap.remove(channel.id()));
        });
        catnip.on(DiscordEvent.CHANNEL_UPDATE, channel -> {
            if(!channel.isText() || !channel.asTextChannel().guildId().equals(dbGuildId)) {
                return;
            }
            final String name = channel.asTextChannel().name();
            final String id = channel.id();
            tableMap.remove(revTableMap.put(id, name));
            tableMap.put(name, id);
        });
    }
    
    @Nonnull
    @CheckReturnValue
    public CompletionStage<JsonObject> fetch(@Nonnull final String table, @Nonnull final String key) {
        final CompletableFuture<JsonObject> f = new CompletableFuture<>();
        fetch0(table, key, f).thenRun(()->{
            if(!f.isDone()) {
                f.completeExceptionally(new NoSuchElementException());
            }
        });
        return f;
    }
    
    @Nonnull
    @CheckReturnValue
    public CompletionStage<JsonObject> fetchOrDefault(@Nonnull final String table, @Nonnull final String key,
                                                      @Nonnull final JsonObject defaultValue) {
        final CompletableFuture<JsonObject> f = new CompletableFuture<>();
        fetch0(table, key, f).thenRun(()->{
            if(!f.isDone()) {
                f.complete(defaultValue);
            }
        });
        return f;
    }
    
    @Nonnull
    @CheckReturnValue
    public CompletionStage<Void> write(@Nonnull final String table, @Nonnull final String key,
                                       @Nonnull final JsonObject data) {
        final String id = tableMap.get(table);
        if(id == null) {
            throw new IllegalArgumentException("No table named " + table);
        }
        return catnip.rest().channel().sendMessage(id, new JsonObject()
                .put("key", key)
                .put("data", data)
                .encode()
        ).thenRun(() -> {});
    }
    
    @Nonnull
    @CheckReturnValue
    private CompletionStage<Void> fetch0(@Nonnull final String table, @Nonnull final String key,
                                         @Nonnull final CompletableFuture<JsonObject> dest) {
        final String id = tableMap.get(table);
        if(id == null) {
            throw new IllegalArgumentException("No table named " + table);
        }
        return catnip.rest().channel().getChannelMessages(id).fetchWhile(message -> {
            try {
                final JsonObject object = new JsonObject(message.content());
                if(key.equals(object.getString("key"))) {
                    dest.complete(object.getJsonObject("data"));
                    return false;
                }
            } catch(final DecodeException ignored) {}
            return true;
        }).exceptionally(e -> {
            dest.completeExceptionally(e);
            return null;
        });
    }
}