import { z } from 'zod';
import type { TUser } from './types';
import { extractEnvVariable } from './utils';
import { TokenExchangeMethodEnum } from './types/agents';

const BaseOptionsSchema = z.object({
  iconPath: z.string().optional(),
  timeout: z.number().optional(),
  initTimeout: z.number().optional(),
  /** Controls visibility in chat dropdown menu (MCPSelect) */
  chatMenu: z.boolean().optional(),
  /**
   * Controls server instruction behavior:
   * - undefined/not set: No instructions included (default)
   * - true: Use server-provided instructions
   * - string: Use custom instructions (overrides server-provided)
   */
  serverInstructions: z.union([z.boolean(), z.string()]).optional(),
  /**
   * OAuth configuration for SSE and Streamable HTTP transports
   * - Optional: OAuth can be auto-discovered on 401 responses
   * - Pre-configured values will skip discovery steps
   */
  oauth: z
    .object({
      /** OAuth authorization endpoint (optional - can be auto-discovered) */
      authorization_url: z.string().url().optional(),
      /** OAuth token endpoint (optional - can be auto-discovered) */
      token_url: z.string().url().optional(),
      /** OAuth client ID (optional - can use dynamic registration) */
      client_id: z.string().optional(),
      /** OAuth client secret (optional - can use dynamic registration) */
      client_secret: z.string().optional(),
      /** OAuth scopes to request */
      scope: z.string().optional(),
      /** OAuth redirect URI (defaults to /api/mcp/{serverName}/oauth/callback) */
      redirect_uri: z.string().url().optional(),
      /** Token exchange method */
      token_exchange_method: z.nativeEnum(TokenExchangeMethodEnum).optional(),
    })
    .optional(),
  customUserVars: z
    .record(
      z.string(),
      z.object({
        title: z.string(),
        description: z.string(),
      }),
    )
    .optional(),
});

export const StdioOptionsSchema = BaseOptionsSchema.extend({
  type: z.literal('stdio').optional(),
  /**
   * The executable to run to start the server.
   */
  command: z.string(),
  /**
   * Command line arguments to pass to the executable.
   */
  args: z.array(z.string()),
  /**
   * The environment to use when spawning the process.
   *
   * If not specified, the result of getDefaultEnvironment() will be used.
   * Environment variables can be referenced using ${VAR_NAME} syntax.
   */
  env: z
    .record(z.string(), z.string())
    .optional()
    .transform((env) => {
      if (!env) {
        return env;
      }

      const processedEnv: Record<string, string> = {};
      for (const [key, value] of Object.entries(env)) {
        processedEnv[key] = extractEnvVariable(value);
      }
      return processedEnv;
    }),
  /**
   * How to handle stderr of the child process. This matches the semantics of Node's `child_process.spawn`.
   *
   * @type {import('node:child_process').IOType | import('node:stream').Stream | number}
   *
   * The default is "inherit", meaning messages to stderr will be printed to the parent process's stderr.
   */
  stderr: z.any().optional(),
});

export const WebSocketOptionsSchema = BaseOptionsSchema.extend({
  type: z.literal('websocket').optional(),
  url: z
    .string()
    .transform((val: string) => extractEnvVariable(val))
    .pipe(z.string().url())
    .refine(
      (val: string) => {
        const protocol = new URL(val).protocol;
        return protocol === 'ws:' || protocol === 'wss:';
      },
      {
        message: 'WebSocket URL must start with ws:// or wss://',
      },
    ),
});

export const SSEOptionsSchema = BaseOptionsSchema.extend({
  type: z.literal('sse').optional(),
  headers: z.record(z.string(), z.string()).optional(),
  url: z
    .string()
    .transform((val: string) => extractEnvVariable(val))
    .pipe(z.string().url())
    .refine(
      (val: string) => {
        const protocol = new URL(val).protocol;
        return protocol !== 'ws:' && protocol !== 'wss:';
      },
      {
        message: 'SSE URL must not start with ws:// or wss://',
      },
    ),
});

export const StreamableHTTPOptionsSchema = BaseOptionsSchema.extend({
  type: z.literal('streamable-http'),
  headers: z.record(z.string(), z.string()).optional(),
  url: z
    .string()
    .transform((val: string) => extractEnvVariable(val))
    .pipe(z.string().url())
    .refine(
      (val: string) => {
        const protocol = new URL(val).protocol;
        return protocol !== 'ws:' && protocol !== 'wss:';
      },
      {
        message: 'Streamable HTTP URL must not start with ws:// or wss://',
      },
    ),
});

export const MCPOptionsSchema = z.union([
  StdioOptionsSchema,
  WebSocketOptionsSchema,
  SSEOptionsSchema,
  StreamableHTTPOptionsSchema,
]);

export const MCPServersSchema = z.record(z.string(), MCPOptionsSchema);

export type MCPOptions = z.infer<typeof MCPOptionsSchema>;

/**
 * List of allowed user fields that can be used in MCP environment variables.
 * These are non-sensitive string/boolean fields from the IUser interface.
 */
const ALLOWED_USER_FIELDS = [
  'name',
  'username',
  'email',
  'provider',
  'role',
  'googleId',
  'facebookId',
  'openidId',
  'samlId',
  'ldapId',
  'githubId',
  'discordId',
  'appleId',
  'emailVerified',
  'twoFactorEnabled',
  'termsAccepted',
] as const;

/**
 * Processes a string value to replace user field placeholders
 * @param value - The string value to process
 * @param user - The user object
 * @returns The processed string with placeholders replaced
 */
function processUserPlaceholders(value: string, user?: TUser): string {
  if (!user || typeof value !== 'string') {
    return value;
  }

  for (const field of ALLOWED_USER_FIELDS) {
    const placeholder = `{{LIBRECHAT_USER_${field.toUpperCase()}}}`;
    if (value.includes(placeholder)) {
      const fieldValue = user[field as keyof TUser];
      const replacementValue = fieldValue != null ? String(fieldValue) : '';
      value = value.replace(new RegExp(placeholder, 'g'), replacementValue);
    }
  }

  return value;
}

function processSingleValue({
  originalValue,
  customUserVars,
  user,
}: {
  originalValue: string;
  customUserVars?: Record<string, string>;
  user?: TUser;
}): string {
  let value = originalValue;

  // 1. Replace custom user variables
  if (customUserVars) {
    for (const [varName, varVal] of Object.entries(customUserVars)) {
      /** Escaped varName for use in regex to avoid issues with special characters */
      const escapedVarName = varName.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
      const placeholderRegex = new RegExp(`\\{\\{${escapedVarName}\\}\\}`, 'g');
      value = value.replace(placeholderRegex, varVal);
    }
  }

  // 2.A. Special handling for LIBRECHAT_USER_ID placeholder
  // This ensures {{LIBRECHAT_USER_ID}} is replaced only if user.id is available.
  // If user.id is null/undefined, the placeholder remains
  if (user && user.id != null && value.includes('{{LIBRECHAT_USER_ID}}')) {
    value = value.replace(/\{\{LIBRECHAT_USER_ID\}\}/g, String(user.id));
  }

  // 2.B. Replace other standard user field placeholders (e.g., {{LIBRECHAT_USER_EMAIL}})
  value = processUserPlaceholders(value, user);

  // 3. Replace system environment variables
  value = extractEnvVariable(value);

  return value;
}

/**
 * Recursively processes an object to replace environment variables in string values
 * @param obj - The object to process
 * @param user - The user object containing all user fields
 * @param customUserVars - vars that user set in settings
 * @returns - The processed object with environment variables replaced
 */
export function processMCPEnv(
  obj: Readonly<MCPOptions>,
  user?: TUser,
  customUserVars?: Record<string, string>,
): MCPOptions {
  if (obj === null || obj === undefined) {
    return obj;
  }

  const newObj: MCPOptions = structuredClone(obj);

  if ('env' in newObj && newObj.env) {
    const processedEnv: Record<string, string> = {};
    for (const [key, originalValue] of Object.entries(newObj.env)) {
      processedEnv[key] = processSingleValue({ originalValue, customUserVars, user });
    }
    newObj.env = processedEnv;
  }

  // Process headers if they exist (for WebSocket, SSE, StreamableHTTP types)
  // Note: `env` and `headers` are on different branches of the MCPOptions union type.
  if ('headers' in newObj && newObj.headers) {
    const processedHeaders: Record<string, string> = {};
    for (const [key, originalValue] of Object.entries(newObj.headers)) {
      processedHeaders[key] = processSingleValue({ originalValue, customUserVars, user });
    }
    newObj.headers = processedHeaders;
  }

  // Process URL if it exists (for WebSocket, SSE, StreamableHTTP types)
  if ('url' in newObj && newObj.url) {
    newObj.url = processSingleValue({ originalValue: newObj.url, customUserVars, user });
  }

  return newObj;
}