/**
 * JSON Schema validation utilities using @cfworker/json-schema
 */

import { Validator } from '@cfworker/json-schema';
import type { TJsonSchema, IOpenApiRouteMeta, IOpenApiParamMeta } from '../decorators/decorators.types.js';
import type { IRequestContext } from '../core/smartserve.interfaces.js';
import { coerceQueryParams, coercePathParams } from './openapi.coerce.js';

/**
 * Validation error detail
 */
export interface IValidationError {
  /** JSON pointer path to the error location */
  path: string;
  /** Human-readable error message */
  message: string;
  /** JSON Schema keyword that failed */
  keyword?: string;
}

/**
 * Validation result
 */
export interface IValidationResult {
  /** Whether validation passed */
  valid: boolean;
  /** Array of validation errors */
  errors: IValidationError[];
}

/**
 * Validate data against a JSON Schema
 */
export function validateSchema(data: unknown, schema: TJsonSchema): IValidationResult {
  const validator = new Validator(schema as any, '2020-12', false);
  const result = validator.validate(data);

  return {
    valid: result.valid,
    errors: result.errors.map(err => ({
      path: err.instanceLocation || '/',
      message: err.error,
      keyword: err.keyword,
    })),
  };
}

/**
 * Validate a single parameter value
 */
export function validateParam(
  name: string,
  value: unknown,
  meta: IOpenApiParamMeta,
  location: 'path' | 'query' | 'header'
): IValidationResult {
  // Check required
  if (meta.required && (value === undefined || value === '')) {
    return {
      valid: false,
      errors: [{
        path: `/${name}`,
        message: `${location} parameter "${name}" is required`,
        keyword: 'required',
      }],
    };
  }

  // Skip validation if no value and not required
  if (value === undefined || value === '') {
    return { valid: true, errors: [] };
  }

  // Validate against schema
  if (meta.schema) {
    const result = validateSchema(value, meta.schema);
    // Prefix errors with parameter name
    return {
      valid: result.valid,
      errors: result.errors.map(err => ({
        ...err,
        path: `/${name}${err.path === '/' ? '' : err.path}`,
      })),
    };
  }

  return { valid: true, errors: [] };
}

/**
 * Create a 400 Bad Request response for validation errors
 */
export function createValidationErrorResponse(
  errors: IValidationError[],
  source: 'body' | 'params' | 'query' | 'headers'
): Response {
  const body = {
    error: 'Validation failed',
    source,
    details: errors.map(e => ({
      path: e.path,
      message: e.message,
    })),
  };

  return new Response(JSON.stringify(body), {
    status: 400,
    headers: {
      'Content-Type': 'application/json',
    },
  });
}

/**
 * Validate the full request based on OpenAPI metadata
 * Returns a Response if validation fails, undefined if valid
 */
export function validateRequest(
  ctx: IRequestContext,
  openapi: IOpenApiRouteMeta
): {
  valid: boolean;
  response?: Response;
  coercedParams?: Record<string, unknown>;
  coercedQuery?: Record<string, unknown>;
} {
  const allErrors: Array<{ errors: IValidationError[]; source: string }> = [];

  // Coerce and validate path parameters
  let coercedParams: Record<string, unknown> = ctx.params;
  if (openapi.params && openapi.params.size > 0) {
    coercedParams = coercePathParams(ctx.params, openapi.params);

    for (const [name, meta] of openapi.params) {
      const result = validateParam(name, coercedParams[name], meta, 'path');
      if (!result.valid) {
        allErrors.push({ errors: result.errors, source: 'params' });
      }
    }
  }

  // Coerce and validate query parameters
  let coercedQuery: Record<string, unknown> = ctx.query;
  if (openapi.query && openapi.query.size > 0) {
    coercedQuery = coerceQueryParams(ctx.query, openapi.query);

    for (const [name, meta] of openapi.query) {
      const result = validateParam(name, coercedQuery[name], meta, 'query');
      if (!result.valid) {
        allErrors.push({ errors: result.errors, source: 'query' });
      }
    }
  }

  // Validate header parameters
  if (openapi.headers && openapi.headers.size > 0) {
    for (const [name, meta] of openapi.headers) {
      const value = ctx.headers.get(name);
      const result = validateParam(name, value, meta, 'header');
      if (!result.valid) {
        allErrors.push({ errors: result.errors, source: 'headers' });
      }
    }
  }

  // Validate request body
  if (openapi.requestBody) {
    const required = openapi.requestBody.required !== false;
    const body = ctx.body;

    if (required && (body === undefined || body === null)) {
      allErrors.push({
        errors: [{
          path: '/',
          message: 'Request body is required',
          keyword: 'required',
        }],
        source: 'body',
      });
    } else if (body !== undefined && body !== null) {
      const result = validateSchema(body, openapi.requestBody.schema);
      if (!result.valid) {
        allErrors.push({ errors: result.errors, source: 'body' });
      }
    }
  }

  // Return first error source as response
  if (allErrors.length > 0) {
    const firstError = allErrors[0];
    return {
      valid: false,
      response: createValidationErrorResponse(
        firstError.errors,
        firstError.source as 'body' | 'params' | 'query' | 'headers'
      ),
    };
  }

  return {
    valid: true,
    coercedParams,
    coercedQuery,
  };
}

/**
 * Create a validation request interceptor for a route
 */
export function createValidationInterceptor(openapi: IOpenApiRouteMeta) {
  return async (ctx: IRequestContext): Promise<IRequestContext | Response | void> => {
    const result = validateRequest(ctx, openapi);

    if (!result.valid && result.response) {
      return result.response;
    }

    // Return modified context with coerced values
    if (result.coercedParams || result.coercedQuery) {
      // Create a new context with coerced values
      // We use Object.defineProperty to update readonly properties
      const newCtx = Object.create(ctx);

      if (result.coercedParams) {
        Object.defineProperty(newCtx, 'params', {
          value: result.coercedParams,
          writable: false,
          enumerable: true,
        });
      }

      if (result.coercedQuery) {
        Object.defineProperty(newCtx, 'query', {
          value: result.coercedQuery,
          writable: false,
          enumerable: true,
        });
      }

      return newCtx;
    }

    return;
  };
}