import { once } from 'node:events';
import path from 'node:path';

import spawn from 'cross-spawn';

import type { IProviderMcp } from '@/shared/interfaces.js';
import type { LLMProvider, McpScope, McpTransport, ProviderMcpServer, UpsertProviderMcpServerInput } from '@/shared/types.js';
import { AppError } from '@/shared/utils.js';

const resolveWorkspacePath = (workspacePath?: string): string =>
  path.resolve(workspacePath ?? process.cwd());

const normalizeServerName = (name: string): string => {
  const normalized = name.trim();
  if (!normalized) {
    throw new AppError('MCP server name is required.', {
      code: 'MCP_SERVER_NAME_REQUIRED',
      statusCode: 400,
    });
  }

  return normalized;
};

const runStdioServerProbe = async (
  server: ProviderMcpServer,
  workspacePath: string,
): Promise<{ reachable: boolean; error?: string }> => {
  if (!server.command) {
    return { reachable: false, error: 'Missing stdio command.' };
  }

  try {
    const child = spawn(server.command, server.args ?? [], {
      cwd: server.cwd ? path.resolve(workspacePath, server.cwd) : workspacePath,
      env: {
        ...process.env,
        ...(server.env ?? {}),
      },
      stdio: ['ignore', 'pipe', 'pipe'],
    });

    const timeout = setTimeout(() => {
      if (!child.killed && child.exitCode === null) {
        child.kill('SIGTERM');
      }
    }, 1_500);

    const errorPromise = once(child, 'error').then(([error]) => {
      throw error;
    });
    const closePromise = once(child, 'close');
    await Promise.race([closePromise, errorPromise]);
    clearTimeout(timeout);

    if (typeof child.exitCode === 'number' && child.exitCode !== 0) {
      return {
        reachable: false,
        error: `Process exited with code ${child.exitCode}.`,
      };
    }

    return { reachable: true };
  } catch (error) {
    return {
      reachable: false,
      error: error instanceof Error ? error.message : 'Failed to start stdio process',
    };
  }
};

const runHttpServerProbe = async (
  url: string,
): Promise<{ reachable: boolean; statusCode?: number; error?: string }> => {
  const controller = new AbortController();
  const timeout = setTimeout(() => controller.abort(), 3_000);
  try {
    const response = await fetch(url, { method: 'GET', signal: controller.signal });
    clearTimeout(timeout);
    return {
      reachable: true,
      statusCode: response.status,
    };
  } catch (error) {
    clearTimeout(timeout);
    return {
      reachable: false,
      error: error instanceof Error ? error.message : 'Network probe failed',
    };
  }
};

/**
 * Shared MCP provider for provider-specific config readers/writers.
 */
export abstract class McpProvider implements IProviderMcp {
  protected readonly provider: LLMProvider;
  protected readonly supportedScopes: McpScope[];
  protected readonly supportedTransports: McpTransport[];

  protected constructor(
    provider: LLMProvider,
    supportedScopes: McpScope[],
    supportedTransports: McpTransport[],
  ) {
    this.provider = provider;
    this.supportedScopes = supportedScopes;
    this.supportedTransports = supportedTransports;
  }

  async listServers(options?: { workspacePath?: string }): Promise<Record<McpScope, ProviderMcpServer[]>> {
    const grouped: Record<McpScope, ProviderMcpServer[]> = {
      user: [],
      local: [],
      project: [],
    };

    for (const scope of this.supportedScopes) {
      grouped[scope] = await this.listServersForScope(scope, options);
    }

    return grouped;
  }

  async listServersForScope(
    scope: McpScope,
    options?: { workspacePath?: string },
  ): Promise<ProviderMcpServer[]> {
    if (!this.supportedScopes.includes(scope)) {
      return [];
    }

    const workspacePath = resolveWorkspacePath(options?.workspacePath);
    const scopedServers = await this.readScopedServers(scope, workspacePath);
    return Object.entries(scopedServers)
      .map(([name, rawConfig]) => this.normalizeServerConfig(scope, name, rawConfig))
      .filter((entry): entry is ProviderMcpServer => entry !== null);
  }

  async upsertServer(input: UpsertProviderMcpServerInput): Promise<ProviderMcpServer> {
    const scope = input.scope ?? 'project';
    this.assertScopeAndTransport(scope, input.transport);

    const workspacePath = resolveWorkspacePath(input.workspacePath);
    const normalizedName = normalizeServerName(input.name);
    const scopedServers = await this.readScopedServers(scope, workspacePath);
    scopedServers[normalizedName] = this.buildServerConfig(input);
    await this.writeScopedServers(scope, workspacePath, scopedServers);

    return {
      provider: this.provider,
      name: normalizedName,
      scope,
      transport: input.transport,
      command: input.command,
      args: input.args,
      env: input.env,
      cwd: input.cwd,
      url: input.url,
      headers: input.headers,
      envVars: input.envVars,
      bearerTokenEnvVar: input.bearerTokenEnvVar,
      envHttpHeaders: input.envHttpHeaders,
    };
  }

  async removeServer(
    input: { name: string; scope?: McpScope; workspacePath?: string },
  ): Promise<{ removed: boolean; provider: LLMProvider; name: string; scope: McpScope }> {
    const scope = input.scope ?? 'project';
    this.assertScope(scope);

    const workspacePath = resolveWorkspacePath(input.workspacePath);
    const normalizedName = normalizeServerName(input.name);
    const scopedServers = await this.readScopedServers(scope, workspacePath);
    const removed = Object.prototype.hasOwnProperty.call(scopedServers, normalizedName);
    if (removed) {
      delete scopedServers[normalizedName];
      await this.writeScopedServers(scope, workspacePath, scopedServers);
    }

    return { removed, provider: this.provider, name: normalizedName, scope };
  }

  async runServer(
    input: { name: string; scope?: McpScope; workspacePath?: string },
  ): Promise<{
    provider: LLMProvider;
    name: string;
    scope: McpScope;
    transport: McpTransport;
    reachable: boolean;
    statusCode?: number;
    error?: string;
  }> {
    const scope = input.scope ?? 'project';
    this.assertScope(scope);

    const workspacePath = resolveWorkspacePath(input.workspacePath);
    const normalizedName = normalizeServerName(input.name);
    const scopedServers = await this.readScopedServers(scope, workspacePath);
    const rawConfig = scopedServers[normalizedName];
    if (!rawConfig || typeof rawConfig !== 'object') {
      throw new AppError(`MCP server "${normalizedName}" was not found.`, {
        code: 'MCP_SERVER_NOT_FOUND',
        statusCode: 404,
      });
    }

    const normalized = this.normalizeServerConfig(scope, normalizedName, rawConfig);
    if (!normalized) {
      throw new AppError(`MCP server "${normalizedName}" has an invalid configuration.`, {
        code: 'MCP_SERVER_INVALID_CONFIG',
        statusCode: 400,
      });
    }

    if (normalized.transport === 'stdio') {
      const result = await runStdioServerProbe(normalized, workspacePath);
      return {
        provider: this.provider,
        name: normalizedName,
        scope,
        transport: normalized.transport,
        reachable: result.reachable,
        error: result.error,
      };
    }

    const result = await runHttpServerProbe(normalized.url ?? '');
    return {
      provider: this.provider,
      name: normalizedName,
      scope,
      transport: normalized.transport,
      reachable: result.reachable,
      statusCode: result.statusCode,
      error: result.error,
    };
  }

  protected abstract readScopedServers(
    scope: McpScope,
    workspacePath: string,
  ): Promise<Record<string, unknown>>;

  protected abstract writeScopedServers(
    scope: McpScope,
    workspacePath: string,
    servers: Record<string, unknown>,
  ): Promise<void>;

  protected abstract buildServerConfig(input: UpsertProviderMcpServerInput): Record<string, unknown>;

  protected abstract normalizeServerConfig(
    scope: McpScope,
    name: string,
    rawConfig: unknown,
  ): ProviderMcpServer | null;

  protected assertScope(scope: McpScope): void {
    if (!this.supportedScopes.includes(scope)) {
      throw new AppError(`Provider "${this.provider}" does not support "${scope}" MCP scope.`, {
        code: 'MCP_SCOPE_NOT_SUPPORTED',
        statusCode: 400,
      });
    }
  }

  protected assertScopeAndTransport(scope: McpScope, transport: McpTransport): void {
    this.assertScope(scope);
    if (!this.supportedTransports.includes(transport)) {
      throw new AppError(`Provider "${this.provider}" does not support "${transport}" MCP transport.`, {
        code: 'MCP_TRANSPORT_NOT_SUPPORTED',
        statusCode: 400,
      });
    }
  }
}