import { query } from '@anthropic-ai/claude-agent-sdk';
import type {
  SDKMessage,
  SDKAssistantMessage,
  SDKUserMessage,
  SDKResultMessage,
  SDKPartialAssistantMessage,
  SDKSystemMessage,
  SDKToolProgressMessage,
  Options,
  McpStdioServerConfig,
  NotificationHookInput,
  PostToolUseHookInput,
} from '@anthropic-ai/claude-agent-sdk';
import type { ClaudeStreamOptions, SSEEvent, TokenUsage, MCPServerConfig, PermissionRequestEvent } from '@/types';
import { registerPendingPermission } from './permission-registry';
import { execFileSync } from 'child_process';
import os from 'os';
import path from 'path';

let cachedClaudePath: string | null | undefined;

function findClaudePath(): string | undefined {
  if (cachedClaudePath !== undefined) return cachedClaudePath || undefined;

  const home = os.homedir();
  const candidates = [
    '/usr/local/bin/claude',
    '/opt/homebrew/bin/claude',
    path.join(home, '.npm-global', 'bin', 'claude'),
    path.join(home, '.local', 'bin', 'claude'),
    path.join(home, '.claude', 'bin', 'claude'),
  ];

  for (const p of candidates) {
    try {
      execFileSync(p, ['--version'], { timeout: 3000, stdio: 'pipe' });
      cachedClaudePath = p;
      return p;
    } catch {
      // not found
    }
  }

  // Fallback: which claude
  const extra = ['/usr/local/bin', '/opt/homebrew/bin', '/usr/bin', '/bin',
    path.join(home, '.npm-global', 'bin'), path.join(home, '.nvm', 'current', 'bin'),
    path.join(home, '.local', 'bin'), path.join(home, '.claude', 'bin')];
  const current = (process.env.PATH || '').split(':');
  for (const p of extra) { if (!current.includes(p)) current.push(p); }

  try {
    const result = execFileSync('/usr/bin/which', ['claude'], {
      timeout: 3000, stdio: 'pipe',
      env: { ...process.env, PATH: current.join(':') },
    });
    const found = result.toString().trim();
    if (found) { cachedClaudePath = found; return found; }
  } catch { /* not found */ }

  cachedClaudePath = null;
  return undefined;
}

/**
 * Convert our MCPServerConfig to the SDK's McpStdioServerConfig format
 */
function toSdkMcpConfig(
  servers: Record<string, MCPServerConfig>
): Record<string, McpStdioServerConfig> {
  const result: Record<string, McpStdioServerConfig> = {};
  for (const [name, config] of Object.entries(servers)) {
    result[name] = {
      command: config.command,
      args: config.args,
      env: config.env,
    };
  }
  return result;
}

/**
 * Format an SSE line from an event object
 */
function formatSSE(event: SSEEvent): string {
  return `data: ${JSON.stringify(event)}\n\n`;
}

/**
 * Extract text content from an SDK assistant message
 */
function extractTextFromMessage(msg: SDKAssistantMessage): string {
  const parts: string[] = [];
  for (const block of msg.message.content) {
    if (block.type === 'text') {
      parts.push(block.text);
    }
  }
  return parts.join('');
}

/**
 * Extract token usage from an SDK result message
 */
function extractTokenUsage(msg: SDKResultMessage): TokenUsage | null {
  if (!msg.usage) return null;
  return {
    input_tokens: msg.usage.input_tokens,
    output_tokens: msg.usage.output_tokens,
    cache_read_input_tokens: msg.usage.cache_read_input_tokens ?? 0,
    cache_creation_input_tokens: msg.usage.cache_creation_input_tokens ?? 0,
    cost_usd: 'total_cost_usd' in msg ? msg.total_cost_usd : undefined,
  };
}

/**
 * Stream Claude responses using the Agent SDK.
 * Returns a ReadableStream of SSE-formatted strings.
 */
export function streamClaude(options: ClaudeStreamOptions): ReadableStream<string> {
  const {
    prompt,
    sdkSessionId,
    model,
    systemPrompt,
    workingDirectory,
    mcpServers,
    abortController,
    permissionMode,
  } = options;

  return new ReadableStream<string>({
    async start(controller) {
      try {
        const queryOptions: Options = {
          cwd: workingDirectory || process.cwd(),
          abortController,
          includePartialMessages: true,
          permissionMode: (permissionMode as Options['permissionMode']) || 'acceptEdits',
        };

        // Find claude binary for packaged app where PATH is limited
        const claudePath = findClaudePath();
        if (claudePath) {
          queryOptions.pathToClaudeCodeExecutable = claudePath;
        }

        if (model) {
          queryOptions.model = model;
        }

        if (systemPrompt) {
          queryOptions.systemPrompt = systemPrompt;
        }

        if (mcpServers && Object.keys(mcpServers).length > 0) {
          queryOptions.mcpServers = toSdkMcpConfig(mcpServers);
        }

        // Resume session if we have an SDK session ID from a previous conversation turn
        if (sdkSessionId) {
          queryOptions.resume = sdkSessionId;
        }

        // Permission handler: sends SSE event and waits for user response
        queryOptions.canUseTool = async (toolName, input, opts) => {
          const permissionRequestId = `perm-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`;

          const permEvent: PermissionRequestEvent = {
            permissionRequestId,
            toolName,
            toolInput: input,
            suggestions: opts.suggestions as PermissionRequestEvent['suggestions'],
            decisionReason: opts.decisionReason,
            blockedPath: opts.blockedPath,
            toolUseId: opts.toolUseID,
            description: undefined,
          };

          // Send permission_request SSE event to the client
          controller.enqueue(formatSSE({
            type: 'permission_request',
            data: JSON.stringify(permEvent),
          }));

          // Wait for user response (resolved by POST /api/chat/permission)
          // Store original input so registry can inject updatedInput on allow
          return registerPendingPermission(permissionRequestId, input, opts.signal);
        };

        // Hooks: capture notifications and tool completion events
        queryOptions.hooks = {
          Notification: [{
            hooks: [async (input) => {
              const notif = input as NotificationHookInput;
              controller.enqueue(formatSSE({
                type: 'status',
                data: JSON.stringify({
                  notification: true,
                  title: notif.title,
                  message: notif.message,
                }),
              }));
              return {};
            }],
          }],
          PostToolUse: [{
            hooks: [async (input) => {
              const toolEvent = input as PostToolUseHookInput;
              controller.enqueue(formatSSE({
                type: 'tool_result',
                data: JSON.stringify({
                  tool_use_id: toolEvent.tool_use_id,
                  content: typeof toolEvent.tool_response === 'string'
                    ? toolEvent.tool_response
                    : JSON.stringify(toolEvent.tool_response),
                  is_error: false,
                }),
              }));
              return {};
            }],
          }],
        };

        // Capture real-time stderr output from Claude Code process
        queryOptions.stderr = (data: string) => {
          // Diagnostic: log raw stderr data length to server console
          console.log(`[stderr] received ${data.length} bytes, first 200 chars:`, data.slice(0, 200).replace(/[\x00-\x1F\x7F]/g, '?'));
          // Strip ANSI escape codes, OSC sequences, and control characters
          // but preserve tabs (\x09) and carriage returns (\x0D)
          const cleaned = data
            .replace(/\x1B\[[0-9;]*[a-zA-Z]/g, '')   // CSI sequences (colors, cursor)
            .replace(/\x1B\][^\x07\x1B]*(?:\x07|\x1B\\)/g, '') // OSC sequences
            .replace(/\x1B\([A-Z]/g, '')               // Character set selection
            .replace(/\x1B[=>]/g, '')                   // Keypad mode
            .replace(/[\x00-\x08\x0B\x0C\x0E-\x1F]/g, '') // Control chars (keep \t \n \r)
            .replace(/\r\n/g, '\n')                    // Normalize CRLF
            .replace(/\r/g, '\n')                      // Convert remaining CR to LF
            .replace(/\n{3,}/g, '\n\n')                // Collapse multiple blank lines
            .trim();
          if (cleaned) {
            controller.enqueue(formatSSE({
              type: 'tool_output',
              data: cleaned,
            }));
          }
        };

        const conversation = query({
          prompt,
          options: queryOptions,
        });

        let lastAssistantText = '';
        let tokenUsage: TokenUsage | null = null;

        for await (const message of conversation) {
          if (abortController?.signal.aborted) {
            break;
          }

          switch (message.type) {
            case 'assistant': {
              const assistantMsg = message as SDKAssistantMessage;
              const text = extractTextFromMessage(assistantMsg);
              if (text && text !== lastAssistantText) {
                // Send the new delta
                const delta = text.slice(lastAssistantText.length);
                if (delta) {
                  controller.enqueue(formatSSE({ type: 'text', data: delta }));
                }
                lastAssistantText = text;
              }

              // Check for tool use blocks
              for (const block of assistantMsg.message.content) {
                if (block.type === 'tool_use') {
                  controller.enqueue(formatSSE({
                    type: 'tool_use',
                    data: JSON.stringify({
                      id: block.id,
                      name: block.name,
                      input: block.input,
                    }),
                  }));
                }
              }
              break;
            }

            case 'user': {
              // Tool execution results come back as user messages with tool_result blocks
              const userMsg = message as SDKUserMessage;
              const content = userMsg.message.content;
              if (Array.isArray(content)) {
                for (const block of content) {
                  if (block.type === 'tool_result') {
                    const resultContent = typeof block.content === 'string'
                      ? block.content
                      : Array.isArray(block.content)
                        ? block.content
                            .filter((c: { type: string }) => c.type === 'text')
                            .map((c: { text: string }) => c.text)
                            .join('\n')
                        : String(block.content ?? '');
                    controller.enqueue(formatSSE({
                      type: 'tool_result',
                      data: JSON.stringify({
                        tool_use_id: block.tool_use_id,
                        content: resultContent,
                        is_error: block.is_error || false,
                      }),
                    }));
                  }
                }
              }
              break;
            }

            case 'stream_event': {
              const streamEvent = message as SDKPartialAssistantMessage;
              const evt = streamEvent.event;
              if (evt.type === 'content_block_delta' && 'delta' in evt) {
                const delta = evt.delta;
                if ('text' in delta && delta.text) {
                  controller.enqueue(formatSSE({ type: 'text', data: delta.text }));
                }
              }
              break;
            }

            case 'system': {
              const sysMsg = message as SDKSystemMessage;
              if ('subtype' in sysMsg) {
                if (sysMsg.subtype === 'init') {
                  controller.enqueue(formatSSE({
                    type: 'status',
                    data: JSON.stringify({
                      session_id: sysMsg.session_id,
                      model: sysMsg.model,
                      tools: sysMsg.tools,
                    }),
                  }));
                }
              }
              break;
            }

            case 'tool_progress': {
              const progressMsg = message as SDKToolProgressMessage;
              controller.enqueue(formatSSE({
                type: 'tool_output',
                data: JSON.stringify({
                  _progress: true,
                  tool_use_id: progressMsg.tool_use_id,
                  tool_name: progressMsg.tool_name,
                  elapsed_time_seconds: progressMsg.elapsed_time_seconds,
                }),
              }));
              break;
            }

            case 'result': {
              const resultMsg = message as SDKResultMessage;
              tokenUsage = extractTokenUsage(resultMsg);
              controller.enqueue(formatSSE({
                type: 'result',
                data: JSON.stringify({
                  subtype: resultMsg.subtype,
                  is_error: resultMsg.is_error,
                  num_turns: resultMsg.num_turns,
                  duration_ms: resultMsg.duration_ms,
                  usage: tokenUsage,
                  session_id: resultMsg.session_id,
                }),
              }));
              break;
            }
          }
        }

        controller.enqueue(formatSSE({ type: 'done', data: '' }));
        controller.close();
      } catch (error) {
        const errorMessage = error instanceof Error ? error.message : 'Unknown error';
        controller.enqueue(formatSSE({ type: 'error', data: errorMessage }));
        controller.enqueue(formatSSE({ type: 'done', data: '' }));
        controller.close();
      }
    },

    cancel() {
      abortController?.abort();
    },
  });
}