import { ref } from "vue";
import { sendChatStream } from "../api/chat.js";
import {
  listConversations,
  createConversation,
  getConversationMessages,
  updateConversationTitle as updateConversationTitleAPI,
  deleteConversation as deleteConversationAPI,
  exportConversation as exportConversationAPI
} from "../api/conversations.js";
import { useToast } from "./useToast.js";

let singleton;
let _streamAbort = null;

export function resetChatSingleton() {
  if (_streamAbort) {
    _streamAbort.abort();
    _streamAbort = null;
  }
  singleton = undefined;
}

export function useChat() {
  if (singleton) return singleton;

  const toast = useToast();

  const defaultMessages = [
    {
      role: "assistant",
      content: "Posso responder usando a base de conhecimento da empresa. Envie uma pergunta ou faça upload de documentos.",
      sentAt: 0
    }
  ];

  const CONV_PAGE_SIZE = 20;

  const conversations = ref([]);
  const activeConversationId = ref(null);
  const messages = ref([...defaultMessages]);
  const chatMode = ref("documentos");
  const loading = ref(false);
  const error = ref("");
  const conversationsLoading = ref(false);
  const conversationsError = ref("");
  const conversationsHasMore = ref(false);
  const conversationsOffset = ref(0);

  function normalizeApiMessages(items) {
    return (items ?? []).map((m) => {
      let sources;
      if (m.Sources) {
        if (typeof m.Sources === "string") {
          try { sources = JSON.parse(m.Sources); } catch { sources = undefined; }
        } else {
          sources = m.Sources;
        }
      }
      return {
        role: m.Role === "user" ? "user" : "assistant",
        content: String(m.Content ?? ""),
        sources,
        sentAt: m.SentAt ? new Date(m.SentAt).getTime() : 0
      };
    });
  }

  function normalizeConversation(c) {
    return {
      id: String(c.Id),
      title: c.Title || "Nova conversa",
      createdAt: new Date(c.CreatedAt).getTime(),
      updatedAt: new Date(c.UpdatedAt).getTime(),
      messageCount: Number(c.MessageCount ?? 0)
    };
  }

  async function loadConversationsList() {
    conversationsLoading.value = true;
    conversationsError.value = "";
    conversationsOffset.value = 0;
    try {
      const data = await listConversations({ limit: CONV_PAGE_SIZE, offset: 0 });
      const items = data.items ?? [];
      conversations.value = items.map(normalizeConversation);
      conversationsHasMore.value = items.length >= CONV_PAGE_SIZE;
      conversationsOffset.value = items.length;
    } catch (err) {
      conversations.value = [];
      conversationsHasMore.value = false;
      if (err?.message !== "session_expired") {
        conversationsError.value = err?.message || "Erro ao carregar conversas.";
      }
    } finally {
      conversationsLoading.value = false;
    }
  }

  async function loadMoreConversations() {
    if (!conversationsHasMore.value || conversationsLoading.value) return;
    conversationsLoading.value = true;
    try {
      const data = await listConversations({ limit: CONV_PAGE_SIZE, offset: conversationsOffset.value });
      const items = data.items ?? [];
      conversations.value = [...conversations.value, ...items.map(normalizeConversation)];
      conversationsHasMore.value = items.length >= CONV_PAGE_SIZE;
      conversationsOffset.value += items.length;
    } catch (err) {
      if (err?.message !== "session_expired") {
        toast.erro("Não foi possível carregar mais conversas.");
        console.warn("[useChat] loadMoreConversations:", err);
      }
    } finally {
      conversationsLoading.value = false;
    }
  }

  async function setActiveConversation(id) {
    const strId = String(id ?? "").trim();
    if (!strId) return;
    cancelCurrentStream();
    activeConversationId.value = strId;
    messages.value = [...defaultMessages];
    try {
      const numId = Number(strId);
      if (!numId) return;
      const data = await getConversationMessages(numId);
      if (activeConversationId.value !== strId) return;
      const normalized = normalizeApiMessages(data?.items);
      messages.value = normalized.length ? normalized : [...defaultMessages];
    } catch (err) {
      if (activeConversationId.value !== strId) return;
      messages.value = [...defaultMessages];
      if (err?.message !== "session_expired") {
        conversationsError.value = "Erro ao carregar mensagens da conversa.";
        console.warn("[useChat] setActiveConversation:", err);
      }
    }
  }

  function newConversation() {
    cancelCurrentStream();
    activeConversationId.value = null;
    messages.value = [...defaultMessages];
    return null;
  }

  async function renameConversation(id, title) {
    const strId = String(id ?? "").trim();
    const numId = Number(strId);
    if (!numId || !title?.trim()) return;
    try {
      await updateConversationTitleAPI(numId, title.trim());
      conversations.value = conversations.value.map((c) =>
        c.id === strId ? { ...c, title: title.trim() } : c
      );
    } catch {
      toast.erro("Não foi possível renomear a conversa.");
    }
  }

  async function deleteConversation(id) {
    const strId = String(id ?? "").trim();
    const numId = Number(strId);
    if (!numId) return;
    try {
      await deleteConversationAPI(numId);
      conversations.value = conversations.value.filter((c) => c.id !== strId);
      if (String(activeConversationId.value) === strId) {
        const next = conversations.value[0];
        if (next) await setActiveConversation(next.id);
        else newConversation();
      }
    } catch {
      toast.erro("Não foi possível excluir a conversa.");
    }
  }

  async function exportConversation(id) {
    const numId = Number(String(id ?? "").trim());
    if (!numId) return;
    try {
      const data = await exportConversationAPI(numId);
      const conv = conversations.value.find((c) => c.id === String(id));
      const filename = `conversa-${conv?.title?.slice(0, 40).replace(/[^a-zA-Z0-9À-ÿ\s]/g, "").trim().replace(/\s+/g, "-") || numId}.md`;
      const blob = new Blob([data.markdown ?? ""], { type: "text/markdown" });
      const url = URL.createObjectURL(blob);
      const a = document.createElement("a");
      a.href = url;
      a.download = filename;
      a.click();
      URL.revokeObjectURL(url);
    } catch (err) {
      if (err?.message !== "session_expired") {
        toast.erro("Não foi possível exportar a conversa.");
        console.warn("[useChat] exportConversation:", err);
      }
    }
  }

  function searchConversations(query) {
    const q = String(query ?? "").trim().toLowerCase();
    const sorted = conversations.value
      .slice()
      .sort((a, b) => (b.updatedAt ?? 0) - (a.updatedAt ?? 0));
    if (!q) return sorted;
    return sorted.filter((c) => String(c.title ?? "").toLowerCase().includes(q));
  }

  function clearError() {
    error.value = "";
  }

  function setMode(mode) {
    chatMode.value = mode === "atendimentos" ? "atendimentos" : "documentos";
  }

  function cancelCurrentStream() {
    if (_streamAbort) {
      _streamAbort.abort();
      _streamAbort = null;
    }
    loading.value = false;
  }

  async function send(content) {
    error.value = "";
    const trimmed = String(content ?? "").trim();
    if (!trimmed) return;

    if (_streamAbort) {
      _streamAbort.abort();
    }
    const abortController = new AbortController();
    _streamAbort = abortController;

    let convId = activeConversationId.value ? Number(activeConversationId.value) : null;

    if (!convId) {
      try {
        const title = trimmed.slice(0, 60);
        const conv = await createConversation(title);
        if (_streamAbort !== abortController) {
          return;
        }
        convId = conv.id;
        activeConversationId.value = String(convId);
        const now = Date.now();
        conversations.value = [
          { id: String(convId), title, createdAt: now, updatedAt: now, messageCount: 0 },
          ...conversations.value
        ];
      } catch {

      }
    }

    if (_streamAbort !== abortController) {
      return;
    }

    messages.value.push({ role: "user", content: trimmed, sentAt: Date.now() });

    const assistantMsg = { role: "assistant", content: "", sources: [], sentAt: Date.now(), streaming: true, statusMsg: "" };
    messages.value.push(assistantMsg);

    const liveMsg = messages.value[messages.value.length - 1];

    loading.value = true;

    try {
      await sendChatStream(trimmed, {
        conversationId: convId,
        mode: chatMode.value,
        signal: abortController.signal,
        onStatus: ({ stage, count }) => {
          if (stage === "buscando") liveMsg.statusMsg = "Buscando documentos...";
          else if (stage === "encontrou") liveMsg.statusMsg = `Encontrei ${count} fonte${count !== 1 ? "s" : ""}...`;
          else if (stage === "reordenando") liveMsg.statusMsg = "Selecionando as fontes mais relevantes...";
          else if (stage === "gerando") liveMsg.statusMsg = "Gerando resposta...";
        },
        onChunk: (delta) => {
          liveMsg.statusMsg = "";
          liveMsg.content += delta;
        },
        onSources: (sources) => {
          liveMsg.sources = sources ?? [];
        },
        onDone: () => {
          liveMsg.streaming = false;
          if (_streamAbort !== abortController) return;
          _streamAbort = null;
          loading.value = false;
          if (convId) {
            conversations.value = conversations.value
              .map((c) =>
                c.id === String(convId)
                  ? { ...c, updatedAt: Date.now(), messageCount: (c.messageCount ?? 0) + 2 }
                  : c
              )
              .sort((a, b) => (b.updatedAt ?? 0) - (a.updatedAt ?? 0));
          }
        },
        onError: (e) => {
          liveMsg.streaming = false;
          if (!liveMsg.content) {
            liveMsg.content = "Não consegui responder no momento.";
          }
          if (_streamAbort !== abortController) return;
          _streamAbort = null;
          error.value = e?.message || "erro";
          loading.value = false;
        }
      });
    } catch (e) {
      liveMsg.streaming = false;
      if (!liveMsg.content) {
        liveMsg.content = "Não consegui responder no momento.";
      }
      if (_streamAbort === abortController) {
        _streamAbort = null;
        error.value = e?.message || "erro";
        loading.value = false;
      }
    }
  }

  loadConversationsList();

  singleton = {
    conversations,
    activeConversationId,
    messages,
    chatMode,
    loading,
    error,
    conversationsLoading,
    conversationsError,
    conversationsHasMore,
    send,
    setMode,
    clearError,
    cancelCurrentStream,
    newConversation,
    setActiveConversation,
    renameConversation,
    deleteConversation,
    searchConversations,
    loadConversationsList,
    loadMoreConversations,
    exportConversation
  };

  return singleton;
}