// Regulation mapping — configuration, capability model and runtime factory.
//
// This is the "ingestion + retrieval" slice: it consumes a Qdrant collection of
// embedded regulation-catalog chunks and, for a given finding definition,
// retrieves the best-matching atomic regulation units. It performs no LLM
// selection and persists nothing. The feature stays DISABLED unless an internal
// Qdrant endpoint and an OpenAI-compatible embedding endpoint are configured.
//
// Security: every call is backend-only, aimed at the explicitly configured
// internal endpoints. Query text, catalog text and vector values are never
// logged. Only ids, counts, versions, durations and safe error codes are safe
// to surface.

import type {
  RegulationDefinitionInput,
  RegulationRetrievalResult,
  RegulationCapability,
  RegulationCapabilityReport
} from './regulation-retrieval-types';

export type {
  RegulationDefinitionInput,
  RegulationRetrievalResult,
  RegulationCapability,
  RegulationCapabilityReport
} from './regulation-retrieval-types';

export interface RegulationMappingConfig {
  qdrantUrl: string;
  qdrantApiKey?: string;
  collection: string;
  embeddingBaseUrl: string;
  embeddingModel: string;
  embeddingApiKey?: string;
  embeddingDimensions: number;
  catalogVersion: string;
  queryPrefix?: string;
  passagePrefix?: string;
  requestTimeoutMs: number;
  retrievalChunkLimit: number;
  candidateUnitLimit: number;
  maximumQueryCharacters: number;
}

export type RegulationMappingConfigResult =
  | { state: 'disabled' }
  | { state: 'error'; detailCode: string; message: string }
  | { state: 'ready'; config: RegulationMappingConfig };

/** Thrown by retrieve() when the feature is not in a ready state. */
export class RegulationMappingUnavailableError extends Error {
  constructor(readonly report: RegulationCapabilityReport) {
    super('regulation mapping unavailable');
    this.name = 'RegulationMappingUnavailableError';
  }
}

/** Runtime contract used by the HTTP layer. Two implementations exist: a static
 * disabled/misconfigured stub, and the real retrieval service. */
export interface RegulationMapping {
  /** Last known capability without performing any network call. */
  cachedCapability(): RegulationCapabilityReport;
  /** Validate the live backend state and refresh the cached capability. */
  refreshCapability(): Promise<RegulationCapabilityReport>;
  /** Retrieve candidate regulation units; throws RegulationMappingUnavailableError when not ready. */
  retrieve(input: RegulationDefinitionInput): Promise<RegulationRetrievalResult>;
}

export interface RegulationMappingEnvironment {
  ASSESSOR_QDRANT_URL?: string;
  ASSESSOR_QDRANT_API_KEY?: string;
  ASSESSOR_QDRANT_COLLECTION?: string;
  ASSESSOR_EMBEDDING_BASE_URL?: string;
  ASSESSOR_EMBEDDING_MODEL?: string;
  ASSESSOR_EMBEDDING_API_KEY?: string;
  ASSESSOR_EMBEDDING_DIMENSIONS?: string;
  ASSESSOR_EMBEDDING_QUERY_PREFIX?: string;
  ASSESSOR_EMBEDDING_PASSAGE_PREFIX?: string;
  ASSESSOR_REGMAP_CATALOG_VERSION?: string;
  ASSESSOR_REGMAP_TIMEOUT_MS?: string;
  ASSESSOR_REGMAP_CHUNK_LIMIT?: string;
  ASSESSOR_REGMAP_CANDIDATE_LIMIT?: string;
  ASSESSOR_REGMAP_MAX_QUERY_CHARS?: string;
}

function trimmed(value: string | undefined): string | undefined {
  const result = value?.trim();
  return result ? result : undefined;
}

function boundedInteger(
  value: string | undefined,
  fallback: number,
  minimum: number,
  maximum: number,
  name: string
): number {
  if (value === undefined || value.trim() === '') return fallback;
  const parsed = Number(value);
  if (!Number.isInteger(parsed) || parsed < minimum || parsed > maximum) {
    throw new Error(`${name} muss eine Ganzzahl zwischen ${minimum} und ${maximum} sein.`);
  }
  return parsed;
}

function assertUrl(value: string, name: string): string {
  let url: URL;
  try {
    url = new URL(value);
  } catch {
    throw new Error(`${name} ist keine gültige URL.`);
  }
  if (url.protocol !== 'http:' && url.protocol !== 'https:') {
    throw new Error(`${name} muss http:// oder https:// verwenden.`);
  }
  return value.replace(/\/+$/, '');
}

const DEFAULT_COLLECTION = 'regulation_catalog_v1';

/**
 * Parse the regulation-mapping configuration from environment variables.
 * - The embedding base URL is the opt-in signal: without it the feature is
 *   intentionally disabled (the Qdrant URL may be pre-wired by deployment
 *   compose and is harmless on its own).
 * - When the embedding endpoint is set but other required values are missing or
 *   invalid, the feature is misconfigured (error) rather than silently off.
 */
export function readRegulationMappingConfig(
  env: RegulationMappingEnvironment = process.env as RegulationMappingEnvironment
): RegulationMappingConfigResult {
  const embeddingBaseUrl = trimmed(env.ASSESSOR_EMBEDDING_BASE_URL);
  if (!embeddingBaseUrl) return { state: 'disabled' };
  const qdrantUrl = trimmed(env.ASSESSOR_QDRANT_URL);

  try {
    if (!qdrantUrl) throw new Error('ASSESSOR_QDRANT_URL ist erforderlich.');
    const embeddingModel = trimmed(env.ASSESSOR_EMBEDDING_MODEL);
    if (!embeddingModel) throw new Error('ASSESSOR_EMBEDDING_MODEL ist erforderlich.');
    const catalogVersion = trimmed(env.ASSESSOR_REGMAP_CATALOG_VERSION);
    if (!catalogVersion) throw new Error('ASSESSOR_REGMAP_CATALOG_VERSION ist erforderlich.');
    const embeddingDimensions = boundedInteger(
      env.ASSESSOR_EMBEDDING_DIMENSIONS, 0, 8, 8192, 'ASSESSOR_EMBEDDING_DIMENSIONS'
    );
    if (embeddingDimensions === 0) throw new Error('ASSESSOR_EMBEDDING_DIMENSIONS ist erforderlich.');

    const config: RegulationMappingConfig = {
      qdrantUrl: assertUrl(qdrantUrl, 'ASSESSOR_QDRANT_URL'),
      qdrantApiKey: trimmed(env.ASSESSOR_QDRANT_API_KEY),
      collection: trimmed(env.ASSESSOR_QDRANT_COLLECTION) ?? DEFAULT_COLLECTION,
      embeddingBaseUrl: assertUrl(embeddingBaseUrl, 'ASSESSOR_EMBEDDING_BASE_URL'),
      embeddingModel,
      embeddingApiKey: trimmed(env.ASSESSOR_EMBEDDING_API_KEY),
      embeddingDimensions,
      catalogVersion,
      queryPrefix: trimmed(env.ASSESSOR_EMBEDDING_QUERY_PREFIX),
      passagePrefix: trimmed(env.ASSESSOR_EMBEDDING_PASSAGE_PREFIX),
      requestTimeoutMs: boundedInteger(env.ASSESSOR_REGMAP_TIMEOUT_MS, 30_000, 1_000, 120_000, 'ASSESSOR_REGMAP_TIMEOUT_MS'),
      retrievalChunkLimit: boundedInteger(env.ASSESSOR_REGMAP_CHUNK_LIMIT, 20, 1, 200, 'ASSESSOR_REGMAP_CHUNK_LIMIT'),
      candidateUnitLimit: boundedInteger(env.ASSESSOR_REGMAP_CANDIDATE_LIMIT, 5, 1, 50, 'ASSESSOR_REGMAP_CANDIDATE_LIMIT'),
      maximumQueryCharacters: boundedInteger(env.ASSESSOR_REGMAP_MAX_QUERY_CHARS, 4_000, 200, 20_000, 'ASSESSOR_REGMAP_MAX_QUERY_CHARS')
    };
    return { state: 'ready', config };
  } catch (error) {
    return {
      state: 'error',
      detailCode: 'config_incomplete',
      message: error instanceof Error ? error.message : 'Regulation-Mapping-Konfiguration ist ungültig.'
    };
  }
}

/** A static, non-networking runtime used when the feature is disabled or its
 * configuration is invalid. */
class InertRegulationMapping implements RegulationMapping {
  constructor(private readonly report: RegulationCapabilityReport) {}
  cachedCapability(): RegulationCapabilityReport {
    return this.report;
  }
  async refreshCapability(): Promise<RegulationCapabilityReport> {
    return this.report;
  }
  async retrieve(): Promise<RegulationRetrievalResult> {
    throw new RegulationMappingUnavailableError(this.report);
  }
}

export function disabledRegulationMapping(): RegulationMapping {
  return new InertRegulationMapping({ capability: 'disabled' });
}