import { wantsDocxDownload } from './wechat/intent/patterns.mjs';
import { defaultsFromEnv } from './wechat-intent-router-config.mjs';

export const WECHAT_LLM_REFINABLE_KINDS = new Set(['chat.general']);

const DEFAULT_MIN_CONFIDENCE = 0.65;
const DEFAULT_TIMEOUT_MS = 4000;

function envFlag(value, fallback = false) {
  const raw = String(value ?? '').trim().toLowerCase();
  if (!raw) return fallback;
  return ['1', 'true', 'yes', 'on'].includes(raw);
}

function boundedNumber(value, fallback, { min = 0, max = Number.POSITIVE_INFINITY } = {}) {
  if (value == null || value === '') return fallback;
  const parsed = Number(value);
  if (!Number.isFinite(parsed)) return fallback;
  return Math.min(max, Math.max(min, parsed));
}

function normalizeOpenidList(value) {
  return [...new Set(String(value ?? '')
    .split(/[\s,]+/u)
    .map((item) => item.trim())
    .filter(Boolean))].slice(0, 1000);
}

export function resolveWechatIntentRouterPolicy(env = process.env, overrides = {}) {
  const merged = { ...env, ...overrides };
  return {
    enabled: envFlag(merged.MEMIND_WECHAT_INTENT_LLM_ENABLED, false),
    shadowMode: envFlag(merged.MEMIND_WECHAT_INTENT_LLM_SHADOW, true),
    modelProviderKeyId: String(merged.MEMIND_WECHAT_INTENT_MODEL_PROVIDER_KEY_ID ?? '').trim() || null,
    model: String(merged.MEMIND_WECHAT_INTENT_MODEL ?? '').trim() || null,
    minConfidence: boundedNumber(
      merged.MEMIND_WECHAT_INTENT_MIN_CONFIDENCE,
      DEFAULT_MIN_CONFIDENCE,
      { min: 0, max: 1 },
    ),
    timeoutMs: Math.round(boundedNumber(
      merged.MEMIND_WECHAT_INTENT_TIMEOUT_MS,
      DEFAULT_TIMEOUT_MS,
      { min: 500, max: 30_000 },
    )),
    canaryOpenids: normalizeOpenidList(merged.MEMIND_WECHAT_INTENT_CANARY_OPENIDS),
  };
}

export function isWechatIntentLlmEligible({ policy, openid = null } = {}) {
  if (!policy?.enabled) return false;
  if (!Array.isArray(policy.canaryOpenids) || policy.canaryOpenids.length === 0) return true;
  const normalized = String(openid ?? '').trim();
  return normalized.length > 0 && policy.canaryOpenids.includes(normalized);
}

export function shouldRefineWechatIntent(ruleIntent, text = '') {
  const kind = String(ruleIntent?.kind ?? '').trim();
  if (!WECHAT_LLM_REFINABLE_KINDS.has(kind)) return false;
  return String(text ?? '').trim().length >= 2;
}

function buildWechatIntentSystemPrompt() {
  return [
    '你是微信服务号意图分类器，只判断用户消息更适合哪种处理通道。',
    '只输出 JSON，不要 markdown：',
    '{"kind":"page.generate|chat.general","confidence":0.0,"reason":"一句话"}',
    'page.generate：用户希望生成/整理/排版 HTML 页面、图文、推文、专题、报告页，或明确要把内容做成可发布/可转发的页面。',
    'chat.general：普通问答、闲聊、解释、建议、查询，不需要产出 HTML 页面。',
    '如果用户只是口头提到“页面/文章”但没有生成或交付页面意图，仍判 chat.general。',
  ].join('\n');
}

function buildWechatIntentUserPrompt(text) {
  return ['[User]', String(text ?? '').trim() || '(empty)'].join('\n');
}

export function parseWechatIntentJson(reply) {
  const text = String(reply ?? '').trim();
  if (!text) return null;
  const fenced = text.match(/```(?:json)?\s*([\s\S]*?)```/i);
  const candidate = (fenced?.[1] ?? text).trim();
  try {
    return JSON.parse(candidate);
  } catch {
    const start = candidate.indexOf('{');
    const end = candidate.lastIndexOf('}');
    if (start < 0 || end <= start) return null;
    try {
      return JSON.parse(candidate.slice(start, end + 1));
    } catch {
      return null;
    }
  }
}

export function normalizeWechatLlmIntent(raw) {
  const kindRaw = String(raw?.kind ?? '').trim().toLowerCase();
  const kind = kindRaw === 'page.generate' ? 'page.generate' : 'chat.general';
  const confidenceRaw = Number(raw?.confidence);
  const confidence = Number.isFinite(confidenceRaw)
    ? Math.min(1, Math.max(0, confidenceRaw))
    : 0.7;
  const reason = String(raw?.reason ?? '').trim() || '微信 LLM 意图判定';
  return { kind, confidence, reason, source: 'llm' };
}

async function withTimeout(promise, timeoutMs, label) {
  if (!timeoutMs || timeoutMs <= 0) return promise;
  let timer = null;
  try {
    return await Promise.race([
      promise,
      new Promise((_, reject) => {
        timer = setTimeout(() => {
          const err = new Error(`${label} timed out after ${timeoutMs}ms`);
          err.code = 'WECHAT_INTENT_ROUTER_TIMEOUT';
          reject(err);
        }, timeoutMs);
        timer.unref?.();
      }),
    ]);
  } finally {
    if (timer) clearTimeout(timer);
  }
}

export function createWechatIntentRouter({
  llmProviderService,
  env = process.env,
  logger = console,
  policy: policyOverride = null,
} = {}) {
  const policy = policyOverride ?? resolveWechatIntentRouterPolicy(env);

  async function classifyWithLlm(text) {
    if (typeof llmProviderService?.createChatCompletion !== 'function') return null;
    try {
      const completion = await withTimeout(
        llmProviderService.createChatCompletion({
          providerKeyId: policy.modelProviderKeyId || undefined,
          model: policy.model || undefined,
          temperature: 0,
          messages: [
            { role: 'system', content: buildWechatIntentSystemPrompt() },
            { role: 'user', content: buildWechatIntentUserPrompt(text) },
          ],
        }),
        policy.timeoutMs,
        'WeChat intent router',
      );
      if (!completion?.ok) return null;
      const parsed = parseWechatIntentJson(completion.reply);
      if (!parsed) return null;
      return normalizeWechatLlmIntent({
        ...parsed,
        model: completion.model ?? policy.model,
        providerKeyId: completion.providerKeyId ?? policy.modelProviderKeyId,
      });
    } catch (err) {
      logger?.warn?.(
        `[wechat-intent-router] LLM classify skipped: ${err instanceof Error ? err.message : err}`,
      );
      return null;
    }
  }

  function getStatus() {
    return {
      enabled: policy.enabled,
      shadowMode: policy.shadowMode,
      llmRoutingEnabled: Boolean(policy.enabled && !policy.shadowMode),
      llmRoutingShadow: Boolean(policy.enabled && policy.shadowMode),
      modelProviderKeyId: policy.modelProviderKeyId,
      model: policy.model,
      minConfidence: policy.minConfidence,
      timeoutMs: policy.timeoutMs,
      canaryOpenidCount: policy.canaryOpenids.length,
    };
  }

  async function refineIntent({
    ruleIntent,
    text = '',
    openid = null,
  } = {}) {
    const baseline = ruleIntent ?? { kind: 'chat.general' };
    if (!shouldRefineWechatIntent(baseline, text)) {
      return { ...baseline, intentSource: 'rules' };
    }
    if (!isWechatIntentLlmEligible({ policy, openid })) {
      return { ...baseline, intentSource: 'rules' };
    }

    const llmResult = await classifyWithLlm(text);
    const shadowPayload = llmResult
      ? {
        kind: llmResult.kind,
        confidence: llmResult.confidence,
        reason: llmResult.reason,
        wouldChangeKind: llmResult.kind !== baseline.kind,
      }
      : {
        skipped: true,
        reason: 'llm_unavailable_or_low_signal',
        wouldChangeKind: false,
      };

    if (policy.shadowMode) {
      logger?.info?.('[wechat-intent-router-shadow]', {
        openid: openid ?? null,
        baselineKind: baseline.kind,
        ...shadowPayload,
      });
      return {
        ...baseline,
        intentSource: 'rules',
        llmShadow: shadowPayload,
      };
    }

    if (!llmResult || llmResult.confidence < policy.minConfidence) {
      return {
        ...baseline,
        intentSource: 'rules',
        llmSuggestion: llmResult,
      };
    }

    if (llmResult.kind === baseline.kind) {
      return {
        ...baseline,
        intentSource: 'rules',
        llmSuggestion: llmResult,
      };
    }

    if (llmResult.kind === 'page.generate') {
      return {
        kind: 'page.generate',
        topic: String(text ?? '').trim(),
        wantsDocx: wantsDocxDownload(text),
        intentSource: 'llm',
        llmReason: llmResult.reason,
        llmConfidence: llmResult.confidence,
        sessionActionResult: baseline.sessionActionResult,
      };
    }

    return {
      kind: 'chat.general',
      text: String(text ?? '').trim(),
      intentSource: 'llm',
      llmReason: llmResult.reason,
      llmConfidence: llmResult.confidence,
      sessionActionResult: baseline.sessionActionResult,
    };
  }

  return {
    getStatus,
    refineIntent,
  };
}

export function createManagedWechatIntentRouter({
  llmProviderService,
  configService = null,
  env = process.env,
  logger = console,
} = {}) {
  let activeRouter = null;
  let activeFingerprint = null;
  let activeMeta = { source: 'env', updatedAt: null, updatedBy: null, configError: null };

  async function loadRouterState() {
    if (!configService?.getRuntimeState) {
      return {
        source: 'env',
        updatedAt: null,
        updatedBy: null,
        fingerprint: 'env-only',
        effectiveEnv: env,
        configError: null,
      };
    }
    try {
      const state = await configService.getRuntimeState();
      return {
        source: state?.source ?? 'admin-db',
        updatedAt: state?.updatedAt ?? null,
        updatedBy: state?.updatedBy ?? null,
        fingerprint: state?.fingerprint ?? `admin-db:${Date.now()}`,
        effectiveEnv: { ...env, ...(state?.overrides ?? {}) },
        configError: null,
      };
    } catch (err) {
      logger?.warn?.(
        `[wechat-intent-router] admin config unavailable, using process env: ${err instanceof Error ? err.message : err}`,
      );
      return {
        source: 'env-fallback',
        updatedAt: null,
        updatedBy: null,
        fingerprint: 'env-fallback',
        effectiveEnv: { ...env },
        configError: err instanceof Error ? err.message : String(err),
      };
    }
  }

  async function ensureRouter() {
    const state = await loadRouterState();
    if (activeRouter && activeFingerprint === state.fingerprint) {
      activeMeta = state;
      return activeRouter;
    }
    activeRouter = createWechatIntentRouter({
      llmProviderService,
      env: state.effectiveEnv,
      logger,
      policy: resolveWechatIntentRouterPolicy(state.effectiveEnv),
    });
    activeFingerprint = state.fingerprint;
    activeMeta = state;
    return activeRouter;
  }

  return {
    async getStatus() {
      const router = await ensureRouter();
      return {
        ...router.getStatus(),
        configSource: activeMeta.source,
        configUpdatedAt: activeMeta.updatedAt,
        configUpdatedBy: activeMeta.updatedBy,
        configError: activeMeta.configError,
      };
    },
    async refineIntent(input = {}) {
      const router = await ensureRouter();
      return router.refineIntent(input);
    },
  };
}