const DEFAULT_COLLECTION = 'memind_memory';
const DEFAULT_LIMIT = 8;
const DEFAULT_TIMEOUT_MS = 3000;

function normalizeUrl(value) {
  const raw = String(value ?? '').trim();
  if (!raw) return null;
  try {
    const url = new URL(raw);
    if (!['http:', 'https:'].includes(url.protocol)) {
      throw new Error(`Unsupported Qdrant URL protocol: ${url.protocol}`);
    }
    return url.toString().replace(/\/$/, '');
  } catch (err) {
    throw new Error(`Invalid MEMORY_QDRANT_URL: ${err instanceof Error ? err.message : err}`);
  }
}

function normalizeCollection(value) {
  const collection = String(value ?? DEFAULT_COLLECTION).trim();
  if (!/^[a-zA-Z0-9_-]+$/.test(collection)) {
    throw new Error(`Invalid Qdrant collection name: ${collection}`);
  }
  return collection;
}

function normalizeVector(value) {
  if (!Array.isArray(value)) return null;
  const vector = value.map((item) => Number(item));
  if (!vector.length || vector.some((item) => !Number.isFinite(item))) return null;
  return vector;
}

function normalizePayload(payload = {}) {
  const text = String(
    payload.content ?? payload.text ?? payload.memory_text ?? payload.memoryText ?? '',
  ).trim();
  if (!text) return null;
  return {
    id: payload.id == null ? null : String(payload.id),
    label: payload.type ?? payload.label ?? 'semantic',
    text,
    createdAt: payload.created_at ?? payload.createdAt ?? null,
  };
}

function normalizePoint(point = {}) {
  const payload = normalizePayload(point.payload ?? {});
  if (!payload) return null;
  return {
    id: point.id == null ? payload.id : String(point.id),
    label: payload.label,
    text: payload.text,
    score: point.score == null ? null : Number(point.score),
    createdAt: payload.createdAt,
  };
}

function timeoutSignal(timeoutMs) {
  if (!Number.isFinite(timeoutMs) || timeoutMs <= 0) return null;
  const controller = new AbortController();
  const timeout = setTimeout(() => controller.abort(), timeoutMs);
  return {
    signal: controller.signal,
    clear() {
      clearTimeout(timeout);
    },
  };
}

export function createQdrantHttpClient({
  url,
  apiKey = null,
  fetchImpl = globalThis.fetch,
  timeoutMs = DEFAULT_TIMEOUT_MS,
} = {}) {
  const resolvedUrl = normalizeUrl(url);
  if (!resolvedUrl) throw new Error('createQdrantHttpClient requires MEMORY_QDRANT_URL');
  if (typeof fetchImpl !== 'function') {
    throw new Error('createQdrantHttpClient requires fetch');
  }

  async function requestJson(path, body) {
    const timeout = timeoutSignal(Number(timeoutMs));
    try {
      const response = await fetchImpl(`${resolvedUrl}${path}`, {
        method: 'POST',
        headers: {
          'content-type': 'application/json',
          ...(apiKey ? { 'api-key': String(apiKey) } : {}),
        },
        body: JSON.stringify(body),
        ...(timeout?.signal ? { signal: timeout.signal } : {}),
      });
      if (!response?.ok) {
        throw new Error(`Qdrant request failed: ${response?.status ?? 'unknown'}`);
      }
      return response.json();
    } finally {
      timeout?.clear();
    }
  }

  return {
    async search({ collection, vector, userId, limit = DEFAULT_LIMIT } = {}) {
      const resolvedCollection = normalizeCollection(collection);
      const resolvedVector = normalizeVector(vector);
      if (!resolvedVector) return [];
      const body = {
        vector: resolvedVector,
        limit: Math.max(1, Math.min(50, Number(limit) || DEFAULT_LIMIT)),
        with_payload: true,
        filter: userId
          ? {
              must: [
                {
                  key: 'user_id',
                  match: { value: String(userId) },
                },
              ],
            }
          : undefined,
      };
      const data = await requestJson(`/collections/${resolvedCollection}/points/search`, body);
      return Array.isArray(data?.result) ? data.result : [];
    },
  };
}

export function createQdrantMemoryBackend({
  enabled = false,
  url = null,
  collection = DEFAULT_COLLECTION,
  client = null,
  embedQuery = null,
  defaultLimit = DEFAULT_LIMIT,
  unavailableReason = null,
} = {}) {
  const resolvedUrl = normalizeUrl(url);
  const resolvedCollection = normalizeCollection(collection);
  const configured = Boolean(enabled && resolvedUrl && resolvedCollection);
  const hasClient = Boolean(client?.search);
  const hasEmbedding = typeof embedQuery === 'function';
  const wired = Boolean(configured && hasClient && hasEmbedding);
  const reason = unavailableReason
    ?? (enabled
      ? (
        !resolvedUrl
          ? 'url_not_configured'
          : (!hasClient ? 'client_not_configured' : 'embedding_module_not_configured')
      )
      : 'not_configured');

  async function resolveVector(input) {
    const explicit = normalizeVector(input?.embedding);
    if (explicit) return explicit;
    if (typeof embedQuery !== 'function' || !input?.query) return null;
    return normalizeVector(await embedQuery(input.query, input));
  }

  return {
    name: 'qdrant',
    category: 'semantic',
    role: 'scale-out-vector-store',
    flag: 'MEMORY_QDRANT_ENABLED',
    unavailableReason: reason,
    url: resolvedUrl,
    collection: resolvedCollection,

    isAvailable() {
      return Boolean(wired);
    },

    getUnavailableReason() {
      return this.isAvailable() ? null : reason;
    },

    async resolve(input = {}) {
      if (!this.isAvailable()) {
        return {
          memories: [],
          semanticMemories: [],
          behaviorSummary: null,
          activeGoals: [],
        };
      }
      const vector = await resolveVector(input);
      if (!vector) {
        return {
          memories: [],
          semanticMemories: [],
          behaviorSummary: null,
          activeGoals: [],
        };
      }
      const points = await client.search({
        collection: resolvedCollection,
        vector,
        userId: input.userId,
        limit: input.limit ?? defaultLimit,
      });
      const memories = points.map((point) => normalizePoint(point)).filter(Boolean);
      return {
        memories,
        semanticMemories: memories.map((memory) => memory.text),
        behaviorSummary: null,
        activeGoals: [],
      };
    },
  };
}