import { IconClearAll, IconSettings } from '@tabler/icons-react';
import {
  MutableRefObject,
  memo,
  useCallback,
  useContext,
  useEffect,
  useRef,
  useState,
} from 'react';
import toast from 'react-hot-toast';

import { useTranslation } from 'next-i18next';

import { getEndpoint } from '@/utils/app/api';
import {
  saveConversation,
  saveConversations,
  updateConversation,
} from '@/utils/app/conversation';
import { throttle } from '@/utils/data/throttle';

import { ChatBody, Conversation, Message } from '@/types/chat';

import HomeContext from '@/pages/api/home/home.context';

import Spinner from '../Spinner';
import { ChatInput } from './ChatInput';
import { ChatLoader } from './ChatLoader';
import { ErrorMessageDiv } from './ErrorMessageDiv';
import { ModelSelect } from './ModelSelect';
import { SystemPrompt } from './SystemPrompt';
import { TemperatureSlider } from './Temperature';
import { MemoizedChatMessage } from './MemoizedChatMessage';

interface Props {
  stopConversationRef: MutableRefObject<boolean>;
}

export const Chat = memo(({ stopConversationRef }: Props) => {
  const { t } = useTranslation('chat');
  const {
    state: {
      selectedConversation,
      conversations,
      models,
      messageIsStreaming,
      modelError,
      loading,
      prompts,
    },
    handleUpdateConversation,
    dispatch: homeDispatch,
  } = useContext(HomeContext);

  const [currentMessage, setCurrentMessage] = useState<Message>();
  const [autoScrollEnabled, setAutoScrollEnabled] = useState<boolean>(true);
  const [showSettings, setShowSettings] = useState<boolean>(false);
  const [showScrollDownButton, setShowScrollDownButton] =
    useState<boolean>(false);

  const messagesEndRef = useRef<HTMLDivElement>(null);
  const chatContainerRef = useRef<HTMLDivElement>(null);
  const textareaRef = useRef<HTMLTextAreaElement>(null);

  const handleSend = useCallback(
    async (message: Message, deleteCount = 0 ) => {
      if (selectedConversation) {
        let updatedConversation: Conversation;
        if (deleteCount) {
          const updatedMessages = [...selectedConversation.messages];
          for (let i = 0; i < deleteCount; i++) {
            updatedMessages.pop();
          }
          updatedConversation = {
            ...selectedConversation,
            messages: [...updatedMessages, message],
          };
        } else {
          updatedConversation = {
            ...selectedConversation,
            messages: [...selectedConversation.messages, message],
          };
        }
        homeDispatch({
          field: 'selectedConversation',
          value: updatedConversation,
        });
        homeDispatch({ field: 'loading', value: true });
        homeDispatch({ field: 'messageIsStreaming', value: true });
        const chatBody: ChatBody = {
          model: updatedConversation.model.name,
          system: updatedConversation.prompt,
          prompt: updatedConversation.messages.map(message => message.content).join(' '),
          options: { temperature: updatedConversation.temperature },
        };
        const endpoint = getEndpoint();
        let body;
        body = JSON.stringify({
          ...chatBody,
        });
        const controller = new AbortController();
        const response = await fetch(endpoint, {
          method: 'POST',
          headers: {
            'Content-Type': 'application/json'
          },
          signal: controller.signal,
          body,
        });
        if (!response.ok) {
          homeDispatch({ field: 'loading', value: false });
          homeDispatch({ field: 'messageIsStreaming', value: false });
          toast.error(response.statusText);
          return;
        }
        const data = response.body;
        if (!data) {
          homeDispatch({ field: 'loading', value: false });
          homeDispatch({ field: 'messageIsStreaming', value: false });
          return;
        }
        if (!false) {
          if (updatedConversation.messages.length === 1) {
            const { content } = message;
            const customName =
              content.length > 30 ? content.substring(0, 30) + '...' : content;
            updatedConversation = {
              ...updatedConversation,
              name: customName,
            };
          }
          homeDispatch({ field: 'loading', value: false });
          const reader = data.getReader();
          const decoder = new TextDecoder();
          let done = false;
          let isFirst = true;
          let text = '';
          while (!done) {
          if (stopConversationRef.current === true) {
            controller.abort();
            done = true;
            break;
          }
          const { value, done: doneReading } = await reader.read();
          done = doneReading;
          const chunkValue = decoder.decode(value);
          text += chunkValue;
          if (isFirst) {
            isFirst = false;
            const updatedMessages: Message[] = [
              ...updatedConversation.messages,
              { role: 'assistant', content: chunkValue },
            ];
            updatedConversation = {
              ...updatedConversation,
              messages: updatedMessages,
            };
            homeDispatch({
              field: 'selectedConversation',
              value: updatedConversation,
            });
            } else {
              const updatedMessages: Message[] =
                updatedConversation.messages.map((message, index) => {
                  if (index === updatedConversation.messages.length - 1) {
                    return {
                      ...message,
                      content: text,
                    };
                  }
                  return message;
                });
              updatedConversation = {
                ...updatedConversation,
                messages: updatedMessages,
              };
              homeDispatch({
                field: 'selectedConversation',
                value: updatedConversation,
              });
            }
          } 
          saveConversation(updatedConversation);
          const updatedConversations: Conversation[] = conversations.map(
            (conversation) => {
              if (conversation.id === selectedConversation.id) {
                return updatedConversation;
              }
              return conversation;
            },
          );
          if (updatedConversations.length === 0) {
            updatedConversations.push(updatedConversation);
          }
          homeDispatch({ field: 'conversations', value: updatedConversations });
          saveConversations(updatedConversations);
          homeDispatch({ field: 'messageIsStreaming', value: false });
        } else {
          const { answer } = await response.json();
          const updatedMessages: Message[] = [
            ...updatedConversation.messages,
            { role: 'assistant', content: answer },
          ];
          updatedConversation = {
            ...updatedConversation,
            messages: updatedMessages,
          };
          homeDispatch({
            field: 'selectedConversation',
            value: updateConversation,
          });
          saveConversation(updatedConversation);
          const updatedConversations: Conversation[] = conversations.map(
            (conversation) => {
              if (conversation.id === selectedConversation.id) {
                return updatedConversation;
              }
              return conversation;
            },
          );
          if (updatedConversations.length === 0) {
            updatedConversations.push(updatedConversation);
          }
          homeDispatch({ field: 'conversations', value: updatedConversations });
          saveConversations(updatedConversations);
          homeDispatch({ field: 'loading', value: false });
          homeDispatch({ field: 'messageIsStreaming', value: false });
        }
      }
    },
    [
      conversations,
      selectedConversation,
      stopConversationRef,
      homeDispatch,
    ],
  );

  const scrollToBottom = useCallback(() => {
    if (autoScrollEnabled) {
      messagesEndRef.current?.scrollIntoView({ behavior: 'smooth' });
      textareaRef.current?.focus();
    }
  }, [autoScrollEnabled]);

  const handleScroll = () => {
    if (chatContainerRef.current) {
      const { scrollTop, scrollHeight, clientHeight } =
        chatContainerRef.current;
      const bottomTolerance = 30;

      if (scrollTop + clientHeight < scrollHeight - bottomTolerance) {
        setAutoScrollEnabled(false);
        setShowScrollDownButton(true);
      } else {
        setAutoScrollEnabled(true);
        setShowScrollDownButton(false);
      }
    }
  };

  const handleScrollDown = () => {
    chatContainerRef.current?.scrollTo({
      top: chatContainerRef.current.scrollHeight,
      behavior: 'smooth',
    });
  };

  const handleSettings = () => {
    setShowSettings(!showSettings);
  };

  const onClearAll = () => {
    if (
      confirm(t<string>('Are you sure you want to clear all messages?')) &&
      selectedConversation
    ) {
      handleUpdateConversation(selectedConversation, {
        key: 'messages',
        value: [],
      });
    }
  };

  const scrollDown = () => {
    if (autoScrollEnabled) {
      messagesEndRef.current?.scrollIntoView(true);
    }
  };
  const throttledScrollDown = throttle(scrollDown, 250);

  useEffect(() => {
    throttledScrollDown();
    selectedConversation &&
      setCurrentMessage(
        selectedConversation.messages[selectedConversation.messages.length - 2],
      );
  }, [selectedConversation, throttledScrollDown]);

  useEffect(() => {
    const observer = new IntersectionObserver(
      ([entry]) => {
        setAutoScrollEnabled(entry.isIntersecting);
        if (entry.isIntersecting) {
          textareaRef.current?.focus();
        }
      },
      {
        root: null,
        threshold: 0.5,
      },
    );
    const messagesEndElement = messagesEndRef.current;
    if (messagesEndElement) {
      observer.observe(messagesEndElement);
    }
    return () => {
      if (messagesEndElement) {
        observer.unobserve(messagesEndElement);
      }
    };
  }, [messagesEndRef]);

  return (
    <div className="relative flex-1 overflow-hidden bg-white dark:bg-[#343541]">
        <>
          <div
            className="max-h-full overflow-x-hidden"
            ref={chatContainerRef}
            onScroll={handleScroll}
          >
            {selectedConversation?.messages.length === 0 ? (
              <>
                <div className="mx-auto flex flex-col space-y-5 md:space-y-10 px-3 pt-5 md:pt-12 sm:max-w-[600px]">
                  <div className="text-center text-3xl font-semibold text-gray-800 dark:text-gray-100">
                    {models.length === 0 ? (
                      <div>
                        <Spinner size="16px" className="mx-auto" />
                      </div>
                    ) : (
                      'Chatbot Ollama'
                    )}
                  </div>

                  {models.length > 0 && (
                    <div className="flex h-full flex-col space-y-4 rounded-lg border border-neutral-200 p-4 dark:border-neutral-600">
                      <ModelSelect />

                      <SystemPrompt
                        conversation={selectedConversation}
                        prompts={prompts}
                        onChangePrompt={(prompt) =>
                          handleUpdateConversation(selectedConversation, {
                            key: 'prompt',
                            value: prompt,
                          })
                        }
                      />

                      <TemperatureSlider
                        label={t('Temperature')}
                        onChangeTemperature={(temperature) =>
                          handleUpdateConversation(selectedConversation, {
                            key: 'temperature',
                            value: temperature,
                          })
                        }
                      />
                    </div>
                  )}
                </div>
              </>
            ) : (
              <>
                <div className="sticky top-0 z-10 flex justify-center border border-b-neutral-300 bg-neutral-100 py-2 text-sm text-neutral-500 dark:border-none dark:bg-[#444654] dark:text-neutral-200">
                  {t('Model')}: {selectedConversation?.model.name} | {t('Temp')}
                  : {selectedConversation?.temperature} |
                  <button
                    className="ml-2 cursor-pointer hover:opacity-50"
                    onClick={handleSettings}
                  >
                    <IconSettings size={18} />
                  </button>
                  <button
                    className="ml-2 cursor-pointer hover:opacity-50"
                    onClick={onClearAll}
                  >
                    <IconClearAll size={18} />
                  </button>
                </div>
                {showSettings && (
                  <div className="flex flex-col space-y-10 md:mx-auto md:max-w-xl md:gap-6 md:py-3 md:pt-6 lg:max-w-2xl lg:px-0 xl:max-w-3xl">
                    <div className="flex h-full flex-col space-y-4 border-b border-neutral-200 p-4 dark:border-neutral-600 md:rounded-lg md:border">
                      <ModelSelect />
                    </div>
                  </div>
                )}

                {selectedConversation?.messages.map((message, index) => (
                  <MemoizedChatMessage
                    key={index}
                    message={message}
                    messageIndex={index}
                    onEdit={(editedMessage) => {
                      setCurrentMessage(editedMessage);
                      // discard edited message and the ones that come after then resend
                      handleSend(
                        editedMessage,
                        selectedConversation?.messages.length - index,
                      );
                    }}
                  />
                ))}

                {loading && <ChatLoader />}

                <div
                  className="h-[162px] bg-white dark:bg-[#343541]"
                  ref={messagesEndRef}
                />
              </>
            )}
          </div>

          <ChatInput
            stopConversationRef={stopConversationRef}
            textareaRef={textareaRef}
            onSend={(message) => {
              setCurrentMessage(message);
              handleSend(message, 0);
            }}
            onScrollDownClick={handleScrollDown}
            onRegenerate={() => {
              if (currentMessage) {
                handleSend(currentMessage, 2);
              }
            }}
            showScrollDownButton={showScrollDownButton}
          />
        </>
    </div>
  );
});
Chat.displayName = 'Chat';
