import { z } from "zod";
import { EventBus } from "../core/EventBus";
import {
  AllPlayersStats,
  ClientID,
  ClientMessage,
  ClientSendWinnerMessage,
  PartialGameRecordSchema,
  PlayerRecord,
  ServerMessage,
  ServerStartGameMessage,
  StampedIntent,
  Turn,
} from "../core/Schemas";
import {
  createPartialGameRecord,
  decompressGameRecord,
  getClanTag,
  replacer,
} from "../core/Util";
import { getPersistentID } from "./Auth";
import { LobbyConfig } from "./ClientGameRunner";
import { ReplaySpeedChangeEvent } from "./InputHandler";
import {
  defaultReplaySpeedMultiplier,
  ReplaySpeedMultiplier,
} from "./utilities/ReplaySpeedMultiplier";

// build a small backlog so MAX can catch up.
const MAX_REPLAY_BACKLOG_TURNS = 60;

export class LocalServer {
  // All turns from the game record on replay.
  private replayTurns: Turn[] = [];

  private turns: Turn[] = [];

  private intents: StampedIntent[] = [];
  private startedAt: number;

  private paused = false;
  private rewriteFrozen = false;
  private replaySpeedMultiplier = defaultReplaySpeedMultiplier;

  private clientID: ClientID | undefined;
  private winner: ClientSendWinnerMessage | null = null;
  private allPlayersStats: AllPlayersStats = {};

  private turnsExecuted = 0;
  private turnStartTime = 0;

  private turnCheckInterval: NodeJS.Timeout;
  private clientConnect: () => void;
  private clientMessage: (message: ServerMessage) => void;

  constructor(
    private lobbyConfig: LobbyConfig,
    private isReplay: boolean,
    private eventBus: EventBus,
  ) {}

  public updateCallback(
    clientConnect: () => void,
    clientMessage: (message: ServerMessage) => void,
  ) {
    this.clientConnect = clientConnect;
    this.clientMessage = clientMessage;
  }

  start() {
    console.log("local server starting");
    this.turnCheckInterval = setInterval(() => {
      const turnIntervalMs =
        this.lobbyConfig.serverConfig.turnIntervalMs() *
        this.replaySpeedMultiplier;
      const backlog = Math.max(0, this.turns.length - this.turnsExecuted);
      const allowReplayBacklog =
        this.replaySpeedMultiplier === ReplaySpeedMultiplier.fastest &&
        this.lobbyConfig.gameRecord !== undefined;
      const maxBacklog = allowReplayBacklog ? MAX_REPLAY_BACKLOG_TURNS : 0;

      const canQueueNextTurn =
        backlog === 0 || (maxBacklog > 0 && backlog < maxBacklog);
      if (
        canQueueNextTurn &&
        Date.now() > this.turnStartTime + turnIntervalMs
      ) {
        this.turnStartTime = Date.now();
        // End turn on the server means the client will start processing the turn.
        this.endTurn();
      }
    }, 5);

    this.eventBus.on(ReplaySpeedChangeEvent, (event) => {
      this.replaySpeedMultiplier = event.replaySpeedMultiplier;
    });

    this.startedAt = Date.now();
    this.clientConnect();
    if (this.lobbyConfig.gameRecord) {
      this.replayTurns = decompressGameRecord(
        this.lobbyConfig.gameRecord,
      ).turns;
    }
    if (this.lobbyConfig.gameStartInfo === undefined) {
      throw new Error("missing gameStartInfo");
    }
    this.clientID = this.lobbyConfig.gameStartInfo.players[0]?.clientID;
    if (!this.clientID) {
      throw new Error("missing clientID");
    }
    this.clientMessage({
      type: "start",
      gameStartInfo: this.lobbyConfig.gameStartInfo,
      turns: [],
      lobbyCreatedAt: this.lobbyConfig.gameStartInfo.lobbyCreatedAt,
      myClientID: this.clientID,
    } satisfies ServerStartGameMessage);
  }

  onMessage(clientMsg: ClientMessage) {
    if (clientMsg.type === "rejoin") {
      if (!this.clientID) {
        throw new Error("missing clientID");
      }
      this.clientMessage({
        type: "start",
        gameStartInfo: this.lobbyConfig.gameStartInfo!,
        turns: this.turns,
        lobbyCreatedAt: this.lobbyConfig.gameStartInfo!.lobbyCreatedAt,
        myClientID: this.clientID,
      } satisfies ServerStartGameMessage);
    }
    if (clientMsg.type === "intent") {
      // Server stamps clientID - client doesn't send it
      const stampedIntent = {
        ...clientMsg.intent,
        clientID: this.clientID!,
      };
      if (stampedIntent.type === "toggle_pause") {
        if (stampedIntent.paused) {
          // Pausing: add intent and end turn before pause takes effect
          this.intents.push(stampedIntent);
          this.endTurn();
          this.paused = true;
        } else {
          // Unpausing: clear pause flag before adding intent so next turn can execute
          this.paused = false;
          this.intents.push(stampedIntent);
          this.endTurn();
        }
        return;
      }
      // Don't process non-pause intents during replays or while paused
      if (this.lobbyConfig.gameRecord || this.paused) {
        return;
      }

      this.intents.push(stampedIntent);
    }
    if (clientMsg.type === "hash") {
      if (!this.lobbyConfig.gameRecord) {
        if (clientMsg.turnNumber % 100 === 0) {
          // In singleplayer, only store hash every 100 turns to reduce size of game record.
          const turn = this.turns[clientMsg.turnNumber];
          if (turn) {
            turn.hash = clientMsg.hash;
          }
        }
        return;
      }
      // If we are replaying a game then verify hash.
      const archivedHash = this.replayTurns[clientMsg.turnNumber].hash;
      if (!archivedHash) {
        console.warn(
          `no archived hash found for turn ${clientMsg.turnNumber}, client hash: ${clientMsg.hash}`,
        );
        return;
      }
      if (archivedHash !== clientMsg.hash) {
        console.error(
          `desync detected on turn ${clientMsg.turnNumber}, client hash: ${clientMsg.hash}, server hash: ${archivedHash}`,
        );
        this.clientMessage({
          type: "desync",
          turn: clientMsg.turnNumber,
          correctHash: archivedHash,
          clientsWithCorrectHash: 0,
          totalActiveClients: 1,
          yourHash: clientMsg.hash,
        });
      } else {
        console.log(
          `hash verified on turn ${clientMsg.turnNumber}, client hash: ${clientMsg.hash}, server hash: ${archivedHash}`,
        );
      }
    }
    if (clientMsg.type === "winner") {
      this.winner = clientMsg;
      this.allPlayersStats = clientMsg.allPlayersStats;
    }
  }

  // This is so the client can tell us when it finished processing the turn.
  public turnComplete() {
    this.turnsExecuted++;
  }

  // endTurn in this context means the server has collected all the intents
  // and will send the turn to the client.
  private endTurn() {
    if (this.paused || this.rewriteFrozen) {
      return;
    }
    if (this.replayTurns.length > 0) {
      if (this.turns.length >= this.replayTurns.length) {
        this.endGame();
        return;
      }
      this.intents = this.replayTurns[this.turns.length].intents;
    }
    const pastTurn: Turn = {
      turnNumber: this.turns.length,
      intents: this.intents,
    };
    this.turns.push(pastTurn);
    this.intents = [];
    this.clientMessage({
      type: "turn",
      turn: pastTurn,
    });
  }

  setRewriteFrozen(frozen: boolean): void {
    this.rewriteFrozen = frozen;
  }

  truncateToTurnCount(turnCount: number): void {
    const clamped = Math.max(0, Math.min(turnCount, this.turns.length));
    this.turns = this.turns.slice(0, clamped);
    this.intents = [];

    // After rewriting history, the client will re-send turns to a fresh worker,
    // so turnsExecuted must start from 0 to keep the backlog logic correct.
    this.turnsExecuted = 0;
    this.turnStartTime = Date.now();
  }

  public endGame() {
    console.log("local server ending game");
    clearInterval(this.turnCheckInterval);
    if (this.isReplay) {
      return;
    }
    const players: PlayerRecord[] = [
      {
        persistentID: getPersistentID(),
        username: this.lobbyConfig.playerName,
        clientID: this.clientID!,
        stats: this.allPlayersStats[this.clientID!],
        cosmetics: this.lobbyConfig.gameStartInfo?.players[0].cosmetics,
        clanTag: getClanTag(this.lobbyConfig.playerName) ?? undefined,
      },
    ];
    if (this.lobbyConfig.gameStartInfo === undefined) {
      throw new Error("missing gameStartInfo");
    }
    const record = createPartialGameRecord(
      this.lobbyConfig.gameStartInfo.gameID,
      this.lobbyConfig.gameStartInfo.config,
      players,
      this.turns,
      this.startedAt,
      Date.now(),
      this.winner?.winner,
    );

    const result = PartialGameRecordSchema.safeParse(record);
    if (!result.success) {
      const error = z.prettifyError(result.error);
      console.error("Error parsing game record", error);
      return;
    }
    const workerPath = this.lobbyConfig.serverConfig.workerPath(
      this.lobbyConfig.gameStartInfo.gameID,
    );

    const jsonString = JSON.stringify(result.data, replacer);

    compress(jsonString)
      .then((compressedData) => {
        return fetch(`/${workerPath}/api/archive_singleplayer_game`, {
          method: "POST",
          headers: {
            "Content-Type": "application/json",
            "Content-Encoding": "gzip",
          },
          body: compressedData,
          keepalive: true, // Ensures request completes even if page unloads
        });
      })
      .catch((error) => {
        console.error("Failed to archive singleplayer game:", error);
      });
  }
}

async function compress(data: string): Promise<ArrayBuffer> {
  const stream = new CompressionStream("gzip");
  const writer = stream.writable.getWriter();
  const reader = stream.readable.getReader();

  // Write the data to the compression stream
  writer.write(new TextEncoder().encode(data));
  writer.close();

  // Read the compressed data
  const chunks: Uint8Array[] = [];
  let done = false;
  while (!done) {
    const { value, done: readerDone } = await reader.read();
    done = readerDone;
    if (value) {
      chunks.push(value);
    }
  }

  // Combine all chunks into a single Uint8Array
  const totalLength = chunks.reduce((acc, chunk) => acc + chunk.length, 0);
  const compressedData = new Uint8Array(totalLength);
  let offset = 0;
  for (const chunk of chunks) {
    compressedData.set(chunk, offset);
    offset += chunk.length;
  }

  return compressedData.buffer;
}