function normalizeLettaId(value, envName) {
  const raw = String(value ?? '').trim();
  if (!raw) return null;
  if (!/^[a-zA-Z0-9_-]+$/.test(raw)) {
    throw new Error(`Invalid ${envName}: ${raw}`);
  }
  return raw;
}

function normalizeMemory(item) {
  if (typeof item === 'string') {
    const text = item.trim();
    return text ? { label: 'lifecycle', text } : null;
  }
  const text = String(
    item?.text ?? item?.content ?? item?.memory_text ?? item?.memoryText ?? '',
  ).trim();
  if (!text) return null;
  return {
    id: item?.id == null ? null : String(item.id),
    label: item?.label ?? item?.type ?? 'lifecycle',
    text,
    createdAt: item?.createdAt ?? item?.created_at ?? null,
  };
}

function normalizeResolvePayload(payload = {}) {
  const memories = Array.isArray(payload?.memories)
    ? payload.memories.map((item) => normalizeMemory(item)).filter(Boolean)
    : [];
  return {
    memories,
    semanticMemories: Array.isArray(payload?.semanticMemories)
      ? payload.semanticMemories
      : memories.map((memory) => memory.text),
    behaviorSummary: payload?.behaviorSummary ?? null,
    activeGoals: Array.isArray(payload?.activeGoals) ? payload.activeGoals : [],
    profile: payload?.profile ?? null,
  };
}

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);
    },
  };
}

function joinUrl(baseUrl, path, params = {}) {
  let resolvedPath = String(path);
  for (const [key, value] of Object.entries(params)) {
    resolvedPath = resolvedPath.replaceAll(`{${key}}`, encodeURIComponent(String(value ?? '')));
  }
  return `${String(baseUrl).replace(/\/$/, '')}/${resolvedPath.replace(/^\//, '')}`;
}

export function createLettaHttpClient({
  apiKey,
  baseUrl = 'https://api.letta.com',
  agentId = null,
  projectId = null,
  resolvePath = '/v1/agents/{agentId}/memory',
  writePath = '/v1/agents/{agentId}/messages',
  compactPath = '/v1/agents/{agentId}/memory/compact',
  modelProviderKeyId = null,
  model = null,
  modelApiType = null,
  fetchImpl = globalThis.fetch,
  timeoutMs = 3000,
} = {}) {
  const resolvedApiKey = String(apiKey ?? '').trim();
  if (!resolvedApiKey) throw new Error('createLettaHttpClient requires MEMORY_LETTA_API_KEY');
  if (typeof fetchImpl !== 'function') throw new Error('createLettaHttpClient requires fetch');
  const resolvedAgentId = normalizeLettaId(agentId, 'MEMORY_LETTA_AGENT_ID');
  const resolvedProjectId = normalizeLettaId(projectId, 'MEMORY_LETTA_PROJECT_ID');

  async function requestJson(method, path, body = null) {
    const timeout = timeoutSignal(Number(timeoutMs));
    try {
      const response = await fetchImpl(joinUrl(baseUrl, path, { agentId: resolvedAgentId }), {
        method,
        headers: {
          'content-type': 'application/json',
          authorization: `Bearer ${resolvedApiKey}`,
        },
        ...(body ? { body: JSON.stringify(body) } : {}),
        ...(timeout?.signal ? { signal: timeout.signal } : {}),
      });
      if (!response?.ok) {
        throw new Error(`Letta request failed: ${response?.status ?? 'unknown'}`);
      }
      return response.json?.() ?? {};
    } finally {
      timeout?.clear();
    }
  }

  return {
    async resolve(input = {}) {
      return requestJson('POST', resolvePath, {
        user_id: input.userId,
        query: input.query,
        limit: input.limit,
        project_id: resolvedProjectId,
        model_provider_key_id: String(modelProviderKeyId ?? '').trim() || null,
        model: String(model ?? '').trim() || null,
        model_api_type: String(modelApiType ?? '').trim() || null,
      });
    },
    async write(input = {}) {
      const data = await requestJson('POST', writePath, {
        user_id: input.userId,
        session_id: input.sessionId,
        messages: Array.isArray(input.messages) ? input.messages : [],
        project_id: resolvedProjectId,
        model_provider_key_id: String(modelProviderKeyId ?? '').trim() || null,
        model: String(model ?? '').trim() || null,
        model_api_type: String(modelApiType ?? '').trim() || null,
      });
      return {
        saved: Number(data?.saved ?? data?.count ?? 1),
        analyzed: Number(data?.analyzed ?? 0),
        memories: Number(data?.memories ?? data?.memory_count ?? 0),
      };
    },
    async compact(input = {}) {
      const data = await requestJson('POST', compactPath, {
        user_id: input.userId,
        project_id: resolvedProjectId,
        model_provider_key_id: String(modelProviderKeyId ?? '').trim() || null,
        model: String(model ?? '').trim() || null,
        model_api_type: String(modelApiType ?? '').trim() || null,
      });
      return {
        analyzed: Number(data?.analyzed ?? 1),
        memories: Number(data?.memories ?? data?.memory_count ?? 0),
      };
    },
  };
}

export function createLettaMemoryBackend({
  enabled = false,
  apiKey = null,
  projectId = null,
  agentId = null,
  client = null,
  unavailableReason = null,
} = {}) {
  const hasApiKey = Boolean(String(apiKey ?? '').trim());
  const resolvedProjectId = normalizeLettaId(projectId, 'MEMORY_LETTA_PROJECT_ID');
  const resolvedAgentId = normalizeLettaId(agentId, 'MEMORY_LETTA_AGENT_ID');
  const configured = Boolean(enabled && hasApiKey);
  const hasClient = Boolean(client?.resolve && client?.write && client?.compact);
  const wired = Boolean(configured && hasClient);
  const reason = unavailableReason
    ?? (enabled
      ? (!hasApiKey ? 'api_key_not_configured' : 'client_not_configured')
      : 'not_configured');

  return {
    name: 'letta',
    category: 'lifecycle',
    role: 'long-short-term-memory-os',
    flag: 'MEMORY_LETTA_ENABLED',
    unavailableReason: reason,
    projectId: resolvedProjectId,
    agentId: resolvedAgentId,

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

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

    async resolve(input = {}) {
      if (!this.isAvailable()) {
        return {
          memories: [],
          semanticMemories: [],
          behaviorSummary: null,
          activeGoals: [],
        };
      }
      return normalizeResolvePayload(await client.resolve({
        ...input,
        projectId: resolvedProjectId,
        agentId: resolvedAgentId,
      }));
    },

    async write(input = {}) {
      if (!this.isAvailable()) return { saved: 0, analyzed: 0, memories: 0 };
      const result = await client.write({
        ...input,
        projectId: resolvedProjectId,
        agentId: resolvedAgentId,
      });
      return {
        saved: Number(result?.saved ?? 0),
        analyzed: Number(result?.analyzed ?? 0),
        memories: Number(result?.memories ?? 0),
      };
    },

    async compact(input = {}) {
      if (!this.isAvailable()) return { analyzed: 0, memories: 0 };
      const result = await client.compact({
        ...input,
        projectId: resolvedProjectId,
        agentId: resolvedAgentId,
      });
      return {
        analyzed: Number(result?.analyzed ?? 0),
        memories: Number(result?.memories ?? 0),
      };
    },
  };
}