import * as vscode from 'vscode';
import { handleBridgeMessage, type BridgeRequest, type BridgeResponse } from './bridge';
import { getThemeKindName } from './theme';
import type { OpenCodeManager, ConnectionStatus } from './opencode';
import { getWebviewShikiThemes } from './shikiThemes';
import { getWebviewHtml } from './webviewHtml';

export class AgentManagerPanelProvider {
  public static readonly viewType = 'openchamber.agentManager';

  private _panel?: vscode.WebviewPanel;
  
  // Cache latest status/URL for when webview is resolved after connection is ready
  private _cachedStatus: ConnectionStatus = 'connecting';
  private _cachedError?: string;
  private _sseCounter = 0;
  private _sseStreams = new Map<string, AbortController>();

  constructor(
    private readonly _context: vscode.ExtensionContext,
    private readonly _extensionUri: vscode.Uri,
    private readonly _openCodeManager?: OpenCodeManager
  ) {}

  public createOrShow(): void {
    // If panel exists, reveal it
    if (this._panel) {
      this._panel.reveal(vscode.ViewColumn.One);
      return;
    }

    const distUri = vscode.Uri.joinPath(this._extensionUri, 'dist');

    // Create new panel
    this._panel = vscode.window.createWebviewPanel(
      AgentManagerPanelProvider.viewType,
      'Agent Manager',
      vscode.ViewColumn.One,
      {
        enableScripts: true,
        retainContextWhenHidden: true,
        localResourceRoots: [this._extensionUri, distUri],
      }
    );

    this._panel.webview.html = this._getHtmlForWebview(this._panel.webview);
    
    // Send theme payload (including optional Shiki theme JSON) after the webview is set up.
    void this.updateTheme(vscode.window.activeColorTheme.kind);
    
    // Send cached connection status
    this._sendCachedState();

    // Handle panel disposal
    this._panel.onDidDispose(() => {
      // Clean up SSE streams
      for (const controller of this._sseStreams.values()) {
        controller.abort();
      }
      this._sseStreams.clear();
      this._panel = undefined;
    }, null, this._context.subscriptions);

    // Handle messages
    this._panel.webview.onDidReceiveMessage(async (message: BridgeRequest) => {
      if (message.type === 'restartApi') {
        await this._openCodeManager?.restart();
        return;
      }

      if (message.type === 'api:sse:start') {
        const response = await this._startSseProxy(message);
        this._panel?.webview.postMessage(response);
        return;
      }

      if (message.type === 'api:sse:stop') {
        const response = await this._stopSseProxy(message);
        this._panel?.webview.postMessage(response);
        return;
      }

      const response = await handleBridgeMessage(message, {
        manager: this._openCodeManager,
        context: this._context,
      });
      this._panel?.webview.postMessage(response);
    }, null, this._context.subscriptions);
  }

  public updateTheme(kind: vscode.ColorThemeKind) {
    if (this._panel) {
      const themeKind = getThemeKindName(kind);
      void getWebviewShikiThemes().then((shikiThemes) => {
        this._panel?.webview.postMessage({
          type: 'themeChange',
          theme: { kind: themeKind, shikiThemes },
        });
      });
    }
  }

  public updateConnectionStatus(status: ConnectionStatus, error?: string) {
    // Cache the latest state
    this._cachedStatus = status;
    this._cachedError = error;
    
    // Send to webview if it exists
    this._sendCachedState();
  }
  
  private _sendCachedState() {
    if (!this._panel) {
      return;
    }
    
    this._panel.webview.postMessage({
      type: 'connectionStatus',
      status: this._cachedStatus,
      error: this._cachedError,
    });
  }

  private _buildSseHeaders(extra?: Record<string, string>): Record<string, string> {
    return {
      Accept: 'text/event-stream',
      'Cache-Control': 'no-cache',
      Connection: 'keep-alive',
      ...(extra || {}),
    };
  }

  private _collectHeaders(headers: Headers): Record<string, string> {
    const result: Record<string, string> = {};
    headers.forEach((value, key) => {
      result[key] = value;
    });
    return result;
  }

  private async _startSseProxy(message: BridgeRequest): Promise<BridgeResponse> {
    const { id, type, payload } = message;
    const apiBaseUrl = this._openCodeManager?.getApiUrl();

    const { path, headers } = (payload || {}) as { path?: string; headers?: Record<string, string> };
    const normalizedPath = typeof path === 'string' && path.trim().length > 0 ? path.trim() : '/event';

    if (!apiBaseUrl) {
      return {
        id,
        type,
        success: true,
        data: { status: 503, headers: { 'content-type': 'application/json' }, streamId: null },
      };
    }

    const streamId = `sse_${++this._sseCounter}_${Date.now()}`;
    const controller = new AbortController();

    const base = `${apiBaseUrl.replace(/\/+$/, '')}/`;
    const targetUrl = new URL(normalizedPath.replace(/^\/+/, ''), base).toString();

    let response: Response;
    try {
      response = await fetch(targetUrl, {
        method: 'GET',
        headers: this._buildSseHeaders(headers || {}),
        signal: controller.signal,
      });
    } catch (error) {
      const message = error instanceof Error ? error.message : String(error);
      return {
        id,
        type,
        success: true,
        data: { status: 502, headers: { 'content-type': 'application/json' }, streamId: null, error: message },
      };
    }

    const responseHeaders = this._collectHeaders(response.headers);
    const responseBody = response.body;
    if (!response.ok || !responseBody) {
      return {
        id,
        type,
        success: true,
        data: {
          status: response.status,
          headers: responseHeaders,
          streamId: null,
          error: `SSE failed: ${response.status}`,
        },
      };
    }

    this._sseStreams.set(streamId, controller);

    (async () => {
      try {
        const reader = responseBody.getReader();
        const decoder = new TextDecoder();
        let sseBuffer = '';

        try {
          while (true) {
            const { done, value } = await reader.read();
            if (done) break;
            if (controller.signal.aborted) break;
            if (value && value.length > 0) {
              const chunk = decoder.decode(value, { stream: true });
              if (!chunk) continue;

              // Reduce webview message pressure by forwarding complete SSE blocks.
              sseBuffer += chunk;
              const blocks = sseBuffer.split('\n\n');
              sseBuffer = blocks.pop() ?? '';
              if (blocks.length > 0) {
                const joined = blocks.map((block) => `${block}\n\n`).join('');
                this._panel?.webview.postMessage({ type: 'api:sse:chunk', streamId, chunk: joined });
              }
            }
          }

          const tail = decoder.decode();
          if (tail) {
            sseBuffer += tail;
          }
          if (sseBuffer) {
            this._panel?.webview.postMessage({ type: 'api:sse:chunk', streamId, chunk: sseBuffer });
          }
        } finally {
          try {
            reader.releaseLock();
          } catch {
            // ignore
          }
        }

        this._panel?.webview.postMessage({ type: 'api:sse:end', streamId });
      } catch (error) {
        if (!controller.signal.aborted) {
          const message = error instanceof Error ? error.message : String(error);
          this._panel?.webview.postMessage({ type: 'api:sse:end', streamId, error: message });
        }
      } finally {
        this._sseStreams.delete(streamId);
      }
    })();

    return {
      id,
      type,
      success: true,
      data: {
        status: response.status,
        headers: responseHeaders,
        streamId,
      },
    };
  }

  private async _stopSseProxy(message: BridgeRequest): Promise<BridgeResponse> {
    const { id, type, payload } = message;
    const { streamId } = (payload || {}) as { streamId?: string };
    if (typeof streamId === 'string' && streamId.length > 0) {
      const controller = this._sseStreams.get(streamId);
      if (controller) {
        controller.abort();
        this._sseStreams.delete(streamId);
      }
    }
    return { id, type, success: true, data: { stopped: true } };
  }

  private _getHtmlForWebview(webview: vscode.Webview): string {
    const workspaceFolder = vscode.workspace.workspaceFolders?.[0]?.uri.fsPath || '';
    const cliAvailable = this._openCodeManager?.isCliAvailable() ?? false;

    return getWebviewHtml({
      webview,
      extensionUri: this._extensionUri,
      workspaceFolder,
      initialStatus: this._cachedStatus,
      cliAvailable,
      panelType: 'agentManager',
    });
  }
}