import * as plugins from './plugins.js';
import { RustBinaryLocator } from './classes.rustbinarylocator.js';
import { StreamingResponse } from './classes.streamingresponse.js';
import type {
  IRustBridgeOptions,
  IRustBridgeLogger,
  TCommandMap,
  IManagementRequest,
  IManagementResponse,
  IManagementEvent,
  TStreamingCommandKeys,
  TExtractChunk,
} from './interfaces/index.js';

const defaultLogger: IRustBridgeLogger = {
  log() {},
};

/**
 * Generic bridge between TypeScript and a Rust binary.
 * Communicates via JSON-over-stdin/stdout IPC protocol.
 *
 * @typeParam TCommands - Map of command names to their param/result types
 */
export class RustBridge<TCommands extends TCommandMap = TCommandMap> extends plugins.events.EventEmitter {
  private locator: RustBinaryLocator;
  private options: Required<Pick<IRustBridgeOptions, 'cliArgs' | 'requestTimeoutMs' | 'readyTimeoutMs' | 'readyEventName' | 'maxPayloadSize'>> & IRustBridgeOptions;
  private logger: IRustBridgeLogger;
  private childProcess: plugins.childProcess.ChildProcess | null = null;
  private stdoutBuffer: Buffer = Buffer.alloc(0);
  private stderrRemainder: string = '';
  private pendingRequests = new Map<string, {
    resolve: (value: any) => void;
    reject: (error: Error) => void;
    timer: ReturnType<typeof setTimeout>;
    streaming?: StreamingResponse<any, any>;
  }>();
  private requestCounter = 0;
  private isRunning = false;
  private binaryPath: string | null = null;

  constructor(options: IRustBridgeOptions) {
    super();
    this.logger = options.logger || defaultLogger;
    this.options = {
      cliArgs: ['--management'],
      requestTimeoutMs: 30000,
      readyTimeoutMs: 10000,
      readyEventName: 'ready',
      maxPayloadSize: 50 * 1024 * 1024,
      ...options,
    };
    this.locator = new RustBinaryLocator(options, this.logger);
  }

  /**
   * Spawn the Rust binary and wait for it to signal readiness.
   * Returns true if the binary was found and spawned successfully.
   */
  public async spawn(): Promise<boolean> {
    this.binaryPath = await this.locator.findBinary();
    if (!this.binaryPath) {
      return false;
    }

    return new Promise<boolean>((resolve) => {
      try {
        const env = this.options.env
          ? { ...process.env, ...this.options.env }
          : { ...process.env };

        this.childProcess = plugins.childProcess.spawn(this.binaryPath!, this.options.cliArgs, {
          stdio: ['pipe', 'pipe', 'pipe'],
          env,
        });

        // Handle stderr with cross-chunk buffering
        this.childProcess.stderr?.on('data', (data: Buffer) => {
          this.stderrRemainder += data.toString();
          const lines = this.stderrRemainder.split('\n');
          // Keep the last element (incomplete line) as remainder
          this.stderrRemainder = lines.pop()!;
          for (const line of lines) {
            const trimmed = line.trim();
            if (trimmed) {
              this.logger.log('debug', `[${this.options.binaryName}] ${trimmed}`);
              this.emit('stderr', trimmed);
            }
          }
        });

        // Handle stdout via Buffer-based newline scanner
        this.childProcess.stdout!.on('data', (chunk: Buffer) => {
          this.handleStdoutChunk(chunk);
        });

        // Handle process exit
        this.childProcess.on('exit', (code, signal) => {
          this.logger.log('info', `Process exited (code=${code}, signal=${signal})`);
          // Flush any remaining stderr
          if (this.stderrRemainder.trim()) {
            this.logger.log('debug', `[${this.options.binaryName}] ${this.stderrRemainder.trim()}`);
            this.emit('stderr', this.stderrRemainder.trim());
          }
          this.cleanup();
          this.emit('exit', code, signal);
        });

        this.childProcess.on('error', (err) => {
          this.logger.log('error', `Process error: ${err.message}`);
          this.cleanup();
          resolve(false);
        });

        // Wait for the ready event
        const readyTimeout = setTimeout(() => {
          this.logger.log('error', `Process did not send ready event within ${this.options.readyTimeoutMs}ms`);
          this.kill();
          resolve(false);
        }, this.options.readyTimeoutMs);

        this.once(`management:${this.options.readyEventName}`, () => {
          clearTimeout(readyTimeout);
          this.isRunning = true;
          this.logger.log('info', `Bridge connected to ${this.options.binaryName}`);
          this.emit('ready');
          resolve(true);
        });
      } catch (err: any) {
        this.logger.log('error', `Failed to spawn: ${err.message}`);
        resolve(false);
      }
    });
  }

  /**
   * Send a typed command to the Rust process and wait for the response.
   */
  public async sendCommand<K extends string & keyof TCommands>(
    method: K,
    params: TCommands[K]['params'],
  ): Promise<TCommands[K]['result']> {
    if (!this.childProcess || !this.isRunning) {
      throw new Error(`${this.options.binaryName} bridge is not running`);
    }

    const id = `req_${++this.requestCounter}`;
    const request: IManagementRequest = { id, method, params };
    const json = JSON.stringify(request);

    // Check outbound payload size
    const byteLength = Buffer.byteLength(json, 'utf8');
    if (byteLength > this.options.maxPayloadSize) {
      throw new Error(
        `Outbound message exceeds maxPayloadSize (${byteLength} > ${this.options.maxPayloadSize})`
      );
    }

    return new Promise<TCommands[K]['result']>((resolve, reject) => {
      const timer = setTimeout(() => {
        this.pendingRequests.delete(id);
        reject(new Error(`Command '${method}' timed out after ${this.options.requestTimeoutMs}ms`));
      }, this.options.requestTimeoutMs);

      this.pendingRequests.set(id, { resolve, reject, timer });

      this.writeToStdin(json + '\n').catch((err) => {
        clearTimeout(timer);
        this.pendingRequests.delete(id);
        reject(new Error(`Failed to write to stdin: ${err.message}`));
      });
    });
  }

  /**
   * Send a streaming command to the Rust process.
   * Returns a StreamingResponse that yields chunks via `for await...of`
   * and exposes `.result` for the final response.
   */
  public sendCommandStreaming<K extends string & TStreamingCommandKeys<TCommands>>(
    method: K,
    params: TCommands[K]['params'],
  ): StreamingResponse<TExtractChunk<TCommands[K]>, TCommands[K]['result']> {
    const streaming = new StreamingResponse<TExtractChunk<TCommands[K]>, TCommands[K]['result']>();

    if (!this.childProcess || !this.isRunning) {
      streaming.fail(new Error(`${this.options.binaryName} bridge is not running`));
      return streaming;
    }

    const id = `req_${++this.requestCounter}`;
    const request: IManagementRequest = { id, method, params };
    const json = JSON.stringify(request);

    const byteLength = Buffer.byteLength(json, 'utf8');
    if (byteLength > this.options.maxPayloadSize) {
      streaming.fail(
        new Error(`Outbound message exceeds maxPayloadSize (${byteLength} > ${this.options.maxPayloadSize})`)
      );
      return streaming;
    }

    const timeoutMs = this.options.streamTimeoutMs ?? this.options.requestTimeoutMs;
    const timer = setTimeout(() => {
      this.pendingRequests.delete(id);
      streaming.fail(new Error(`Streaming command '${method}' timed out after ${timeoutMs}ms`));
    }, timeoutMs);

    this.pendingRequests.set(id, {
      resolve: (result: any) => streaming.finish(result),
      reject: (error: Error) => streaming.fail(error),
      timer,
      streaming,
    });

    this.writeToStdin(json + '\n').catch((err) => {
      clearTimeout(timer);
      this.pendingRequests.delete(id);
      streaming.fail(new Error(`Failed to write to stdin: ${err.message}`));
    });

    return streaming;
  }

  /**
   * Kill the Rust process and clean up all resources.
   */
  public kill(): void {
    if (this.childProcess) {
      const proc = this.childProcess;
      this.childProcess = null;
      this.isRunning = false;

      // Clear buffers
      this.stdoutBuffer = Buffer.alloc(0);
      this.stderrRemainder = '';

      // Reject pending requests
      for (const [, pending] of this.pendingRequests) {
        clearTimeout(pending.timer);
        pending.reject(new Error(`${this.options.binaryName} process killed`));
      }
      this.pendingRequests.clear();

      // Remove all listeners
      proc.removeAllListeners();
      proc.stdout?.removeAllListeners();
      proc.stderr?.removeAllListeners();
      proc.stdin?.removeAllListeners();

      // Kill the process
      try { proc.kill('SIGTERM'); } catch { /* already dead */ }

      // Destroy stdio pipes
      try { proc.stdin?.destroy(); } catch { /* ignore */ }
      try { proc.stdout?.destroy(); } catch { /* ignore */ }
      try { proc.stderr?.destroy(); } catch { /* ignore */ }

      // Unref so Node doesn't wait
      try { proc.unref(); } catch { /* ignore */ }

      // Force kill after 5 seconds
      setTimeout(() => {
        try { proc.kill('SIGKILL'); } catch { /* already dead */ }
      }, 5000).unref();
    }
  }

  /**
   * Whether the bridge is currently running.
   */
  public get running(): boolean {
    return this.isRunning;
  }

  /**
   * Buffer-based newline scanner for stdout chunks.
   * Replaces readline to handle large payloads without buffering entire lines in a separate abstraction.
   */
  private handleStdoutChunk(chunk: Buffer): void {
    this.stdoutBuffer = Buffer.concat([this.stdoutBuffer, chunk]);

    let newlineIndex: number;
    while ((newlineIndex = this.stdoutBuffer.indexOf(0x0A)) !== -1) {
      const lineBuffer = this.stdoutBuffer.subarray(0, newlineIndex);
      this.stdoutBuffer = this.stdoutBuffer.subarray(newlineIndex + 1);

      if (lineBuffer.length > this.options.maxPayloadSize) {
        this.logger.log('error', `Inbound message exceeds maxPayloadSize (${lineBuffer.length} bytes), dropping`);
        continue;
      }

      const line = lineBuffer.toString('utf8').trim();
      this.handleLine(line);
    }

    // If accumulated buffer exceeds maxPayloadSize (sender never sends newline), clear to prevent OOM
    if (this.stdoutBuffer.length > this.options.maxPayloadSize) {
      this.logger.log('error', `Stdout buffer exceeded maxPayloadSize (${this.stdoutBuffer.length} bytes) without newline, clearing`);
      this.stdoutBuffer = Buffer.alloc(0);
    }
  }

  /**
   * Write data to stdin with backpressure support.
   * Waits for drain if the internal buffer is full.
   */
  private writeToStdin(data: string): Promise<void> {
    return new Promise<void>((resolve, reject) => {
      if (!this.childProcess?.stdin) {
        reject(new Error('stdin not available'));
        return;
      }

      const canContinue = this.childProcess.stdin.write(data, 'utf8', (err) => {
        if (err) {
          reject(err);
        }
      });

      if (canContinue) {
        resolve();
      } else {
        // Wait for drain before resolving
        this.childProcess.stdin.once('drain', () => {
          resolve();
        });
      }
    });
  }

  private handleLine(line: string): void {
    if (!line) return;

    let parsed: any;
    try {
      parsed = JSON.parse(line);
    } catch {
      this.logger.log('warn', `Non-JSON output: ${line}`);
      return;
    }

    // Check if it's an event (has 'event' field, no 'id')
    if ('event' in parsed && !('id' in parsed)) {
      const event = parsed as IManagementEvent;
      this.emit(`management:${event.event}`, event.data);
      return;
    }

    // Stream chunk (has 'id' + stream === true + 'data')
    if ('id' in parsed && parsed.stream === true && 'data' in parsed) {
      const pending = this.pendingRequests.get(parsed.id);
      if (pending?.streaming) {
        // Reset inactivity timeout
        clearTimeout(pending.timer);
        const timeoutMs = this.options.streamTimeoutMs ?? this.options.requestTimeoutMs;
        pending.timer = setTimeout(() => {
          this.pendingRequests.delete(parsed.id);
          pending.reject(new Error(`Streaming command timed out after ${timeoutMs}ms of inactivity`));
        }, timeoutMs);
        pending.streaming.pushChunk(parsed.data);
      }
      return;
    }

    // Otherwise it's a response (has 'id' field)
    if ('id' in parsed) {
      const response = parsed as IManagementResponse;
      const pending = this.pendingRequests.get(response.id);
      if (pending) {
        clearTimeout(pending.timer);
        this.pendingRequests.delete(response.id);
        if (response.success) {
          pending.resolve(response.result);
        } else {
          pending.reject(new Error(response.error || 'Unknown error from Rust process'));
        }
      }
    }
  }

  private cleanup(): void {
    this.isRunning = false;
    this.childProcess = null;
    this.stdoutBuffer = Buffer.alloc(0);
    this.stderrRemainder = '';

    // Reject all pending requests
    for (const [, pending] of this.pendingRequests) {
      clearTimeout(pending.timer);
      pending.reject(new Error(`${this.options.binaryName} process exited`));
    }
    this.pendingRequests.clear();
  }
}