import React, { PureComponent } from 'react';
import Drawer from '@mui/material/Drawer';
import Box from '@mui/material/Box';
import Typography from '@mui/material/Typography';
import IconButton from '@mui/material/IconButton';
import Button from '@mui/material/Button';
import TextInput from '../TextInput';
import MenuItem from '@mui/material/MenuItem';
import Select from '@mui/material/Select';
import FormControl from '@mui/material/FormControl';
import InputLabel from '@mui/material/InputLabel';
import CircularProgress from '@mui/material/CircularProgress';
import CloseRoundedIcon from '@mui/icons-material/CloseRounded';
import SendRoundedIcon from '@mui/icons-material/SendRounded';
import AddRoundedIcon from '@mui/icons-material/AddRounded';
import AutoAwesomeRoundedIcon from '@mui/icons-material/AutoAwesomeRounded';
import DeleteOutlineRoundedIcon from '@mui/icons-material/DeleteOutlineRounded';

import chatAutomat, { selectPendingAskUser } from '../../automats/chatAutomat';
import userSettingsAutomat from '../../automats/userSettingsAutomat';
import ChatFlowList from './ChatFlowList';
import AskUserPrompt from './AskUserPrompt';
import {
  BLUE_GLOW,
  SHADOW_DRAWER,
} from '../../colors';

const DEFAULT_DRAWER_WIDTH = 460;
const MIN_DRAWER_WIDTH = 320;

export default class ChatDrawer extends PureComponent {
  constructor(props) {
    super(props);
    const s = chatAutomat.state;
    const settings = userSettingsAutomat.state;
    this.state = {
      isOpen: s.isOpen,
      conversations: s.conversations,
      selectedConversationId: s.selectedConversationId,
      draftConversation: s.draftConversation,
      conversationState: s.conversationState,
      provider: s.provider,
      model: s.model,
      messages: s.messages,
      loadingMessages: s.loadingMessages,
      streamingText: s.streamingText,
      isSending: s.isSending,
      loadingConversations: s.loadingConversations,
      sseStatus: s.sseStatus,
      sendError: s.sendError,
      inputText: '',
      drawerWidth: settings?.chatDrawerWidth || DEFAULT_DRAWER_WIDTH,
      isResizing: false,
    };
    this.inputRef = React.createRef();
    this.focusTimeout = null;
  }

  focusInput = (delay = 50) => {
    if (this.focusTimeout) clearTimeout(this.focusTimeout);
    this.focusTimeout = setTimeout(() => {
      this.inputRef.current?.focus?.();
    }, delay);
  };

  componentDidMount() {
    if (this.state.isOpen) {
      this.focusInput(150);
    }
    this.unsub = chatAutomat.subscribe(this, (state) => {
      const wasOpen = this.state.isOpen;
      const willOpen = state.isOpen;
      if (!wasOpen && willOpen) {
        this.focusInput(150);
      }
      return {
        isOpen: state.isOpen,
        conversations: state.conversations,
        selectedConversationId: state.selectedConversationId,
        draftConversation: state.draftConversation,
        conversationState: state.conversationState,
        provider: state.provider,
        model: state.model,
        messages: state.messages,
        loadingMessages: state.loadingMessages,
        streamingText: state.streamingText,
        isSending: state.isSending,
        loadingConversations: state.loadingConversations,
        sseStatus: state.sseStatus,
        sendError: state.sendError,
      };
    });

    this.unsubSettings = userSettingsAutomat.subscribe(this, (state) => {
      if (!this.state.isResizing) {
        return { drawerWidth: state.chatDrawerWidth || DEFAULT_DRAWER_WIDTH };
      }
      return null;
    });
  }

  componentWillUnmount() {
    if (this.focusTimeout) clearTimeout(this.focusTimeout);
    this.unsub?.();
    this.unsubSettings?.();
    this.cleanupResizeListeners();
  }

  handleClose = () => {
    chatAutomat.actions.closeChat();
  };

  handleResizeStart = (e) => {
    if (e.button !== undefined && e.button !== 0) return;
    e.preventDefault();
    e.stopPropagation();

    const startX = e.clientX ?? (e.touches && e.touches[0]?.clientX);
    if (startX === undefined) return;

    const startWidth = this.state.drawerWidth;
    this.setState({ isResizing: true });

    document.body.style.cursor = 'col-resize';
    document.body.style.userSelect = 'none';

    let currentWidth = startWidth;

    const onMove = (moveEvt) => {
      moveEvt.preventDefault();
      const clientX = moveEvt.clientX ?? (moveEvt.touches && moveEvt.touches[0]?.clientX);
      if (clientX === undefined) return;

      const deltaX = startX - clientX;
      const maxWidth = Math.min(window.innerWidth - 40, 1400);
      const newWidth = Math.max(MIN_DRAWER_WIDTH, Math.min(maxWidth, Math.round(startWidth + deltaX)));

      currentWidth = newWidth;
      this.setState({ drawerWidth: newWidth });
    };

    const onEnd = () => {
      document.body.style.cursor = '';
      document.body.style.userSelect = '';
      window.removeEventListener('pointermove', onMove);
      window.removeEventListener('pointerup', onEnd);
      window.removeEventListener('pointercancel', onEnd);
      window.removeEventListener('mousemove', onMove);
      window.removeEventListener('mouseup', onEnd);
      window.removeEventListener('touchmove', onMove);
      window.removeEventListener('touchend', onEnd);

      this.setState({ isResizing: false });
      userSettingsAutomat.actions.setChatDrawerWidth(currentWidth);
    };

    window.addEventListener('pointermove', onMove, { passive: false });
    window.addEventListener('pointerup', onEnd);
    window.addEventListener('pointercancel', onEnd);
    window.addEventListener('mousemove', onMove, { passive: false });
    window.addEventListener('mouseup', onEnd);
    window.addEventListener('touchmove', onMove, { passive: false });
    window.addEventListener('touchend', onEnd);
  };

  handleResizeDoubleClick = () => {
    this.setState({ drawerWidth: DEFAULT_DRAWER_WIDTH });
    userSettingsAutomat.actions.setChatDrawerWidth(DEFAULT_DRAWER_WIDTH);
  };

  cleanupResizeListeners = () => {
    document.body.style.cursor = '';
    document.body.style.userSelect = '';
  };

  handleSelectConversation = (e) => {
    const id = Number(e.target.value);
    if (id) {
      chatAutomat.actions.selectConversation(id);
      this.focusInput(50);
    }
  };

  handleNewChat = () => {
    chatAutomat.actions.startDraft();
    this.focusInput(50);
  };

  handleDeleteConversation = async (e, convId) => {
    e?.stopPropagation();
    e?.preventDefault();
    if (!convId) return;
    try {
      await chatAutomat.actions.deleteConversation(convId);
    } catch (err) {
      console.error('[ChatDrawer] Failed to delete conversation:', err);
    } finally {
      this.focusInput(50);
    }
  };

  handleSend = async (e) => {
    e?.preventDefault();
    const text = this.state.inputText.trim();
    if (!text || this.state.conversationState === 'busy' || this.state.isSending) {
      return;
    }
    this.setState({ inputText: '' });
    try {
      await chatAutomat.actions.sendMessage(text);
    } catch {
      // Error is tracked in chatAutomat state (sendError)
    }
  };

  handleKeyDown = (e) => {
    if (e.key === 'Enter' && !e.shiftKey) {
      e.preventDefault();
      void this.handleSend();
    }
  };

  handleAnswerTool = async ({ tool_call_id, answer }) => {
    try {
      await chatAutomat.actions.sendToolResponse({ tool_call_id, answer });
    } catch (err) {
      console.error('[ChatDrawer] Failed to send tool response:', err);
    }
  };

  getPendingAskUser = () => selectPendingAskUser(this.state);

  renderHeader() {
    const {
      conversations,
      selectedConversationId,
      loadingConversations,
    } = this.state;


    return (
      <Box
        sx={{
          p: 2,
          borderBottom: 1,
          borderColor: 'divider',
          bgcolor: 'background.paper',
          display: 'flex',
          flexDirection: 'column',
          gap: 1.5,
        }}
      >
        <Box sx={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between' }}>
          <Box sx={{ display: 'flex', alignItems: 'center', gap: 1 }}>
            <AutoAwesomeRoundedIcon sx={{ fontSize: 22, color: 'primary.main' }} />
            <Typography variant="subtitle1" fontWeight={700}>
              KI-Assistent
            </Typography>
          </Box>

          <IconButton size="small" onClick={this.handleClose} aria-label="Chat schließen">
            <CloseRoundedIcon fontSize="small" />
          </IconButton>
        </Box>

        {/* Conversation Selector Bar */}
        {conversations.length > 0 && (
          <Box sx={{ display: 'flex', alignItems: 'center', gap: 1 }}>
            <FormControl fullWidth size="small">
              <InputLabel id="chat-conversation-label">Konversation</InputLabel>
              <Select
                labelId="chat-conversation-label"
                value={selectedConversationId || ''}
                label="Konversation"
                onChange={this.handleSelectConversation}
                disabled={loadingConversations || conversations.length === 0}
                sx={{ borderRadius: 2 }}
                renderValue={(selectedId) => {
                  const conv = conversations.find((c) => c.id === selectedId);
                  if (!conv) return '';
                  return (
                    <Box sx={{ display: 'flex', alignItems: 'center', gap: 1, overflow: 'hidden' }}>
                      <Typography variant="body2" fontWeight={600} noWrap>
                        #{conv.id}
                      </Typography>
                      <Typography variant="caption" color="text.secondary" noWrap>
                        {conv.model || 'Standard'}
                      </Typography>
                    </Box>
                  );
                }}
              >
                {conversations.map((c) => (
                  <MenuItem key={c.id} value={c.id}>
                    <Box sx={{ display: 'flex', alignItems: 'center', gap: 1, width: '100%', overflow: 'hidden' }}>
                      <Typography variant="body2" fontWeight={600} noWrap>
                        #{c.id}
                      </Typography>
                      <Typography variant="caption" color="text.secondary" noWrap sx={{ flexGrow: 1 }}>
                        {c.model || 'Standard'}
                      </Typography>
                    </Box>
                  </MenuItem>
                ))}
              </Select>
            </FormControl>

            <IconButton
              size="small"
              color="error"
              disabled={!selectedConversationId}
              onClick={(e) => this.handleDeleteConversation(e, selectedConversationId)}
              aria-label="Konversation löschen"
              sx={{
                borderRadius: 2,
                border: 1,
                borderColor: 'divider',
                p: 0.9,
                flexShrink: 0,
              }}
            >
              <DeleteOutlineRoundedIcon fontSize="small" />
            </IconButton>

            <IconButton
              size="small"
              color="primary"
              disabled={!selectedConversationId}
              onClick={this.handleNewChat}
              aria-label="Neuer Chat"
              sx={{
                borderRadius: 2,
                border: 1,
                borderColor: 'divider',
                p: 0.9,
                flexShrink: 0,
              }}
            >
              <AddRoundedIcon fontSize="small" />
            </IconButton>
          </Box>
        )}
      </Box>
    );
  }

  renderBody() {
    const {
      conversations,
      selectedConversationId,
      draftConversation,
      conversationState,
      messages,
      streamingText,
      loadingConversations,
      model,
    } = this.state;

    if (loadingConversations && conversations.length === 0) {
      return (
        <Box sx={{ flexGrow: 1, display: 'flex', flexDirection: 'column', alignItems: 'center', justifyContent: 'center', p: 3, gap: 2 }}>
          <CircularProgress size={32} />
          <Typography variant="body2" color="text.secondary">
            Lade Konversationen…
          </Typography>
        </Box>
      );
    }

    if (conversations.length === 0 && !draftConversation) {
      return (
        <Box
          sx={{
            flexGrow: 1,
            display: 'flex',
            flexDirection: 'column',
            alignItems: 'center',
            justifyContent: 'center',
            p: 4,
            textAlign: 'center',
            gap: 2,
          }}
        >
          <AutoAwesomeRoundedIcon sx={{ fontSize: 44, color: 'primary.main', opacity: 0.85 }} />
          <Typography variant="h6" fontWeight={700}>
            Willkommen im Chat
          </Typography>
          <Typography variant="body2" color="text.secondary" sx={{ maxWidth: 280 }}>
            Starte eine Unterhaltung mit dem KI-Modell, um Fragen zu stellen oder Daten abzufragen.
          </Typography>
          <Button
            variant="contained"
            startIcon={<AddRoundedIcon />}
            onClick={this.handleNewChat}
            sx={{ borderRadius: 2, mt: 1 }}
          >
            Neuen Chat starten
          </Button>
        </Box>
      );
    }

    const pendingAsk = this.getPendingAskUser();

    return (
      <Box sx={{ flexGrow: 1, display: 'flex', flexDirection: 'column', minHeight: 0, overflow: 'hidden' }}>
        {messages.length === 0 ? (
          <Box sx={{ flexGrow: 1 }} />
        ) : (
          <ChatFlowList
            messages={
              streamingText
                ? [
                    ...messages,
                    {
                      id: 'streaming',
                      conversation_id: selectedConversationId,
                      role: 'assistant',
                      message: streamingText,
                      streaming: true,
                    },
                  ]
                : messages
            }
            conversationState={conversationState}
            model={model}
          />
        )}

        {pendingAsk && (
          <AskUserPrompt
            askData={pendingAsk}
            onAnswer={this.handleAnswerTool}
            disabled={this.state.isSending}
          />
        )}
      </Box>
    );
  }

  renderFooter() {
    const {
      conversationState,
      isSending,
      selectedConversationId,
      draftConversation,
      inputText,
      sendError,
    } = this.state;

    const pendingAsk = this.getPendingAskUser();
    const isBusy = conversationState === 'busy';
    const isWorking = isBusy || isSending;
    const canChat = (Boolean(selectedConversationId) || draftConversation) && !pendingAsk;
    const canSend = !isWorking && canChat && Boolean(inputText.trim());

    return (
      <Box
        component="form"
        onSubmit={this.handleSend}
        sx={{
          p: 2,
          borderTop: 1,
          borderColor: 'divider',
          bgcolor: 'background.paper',
          display: 'flex',
          flexDirection: 'column',
          gap: 1,
        }}
      >
        {sendError && (
          <Box
            sx={{
              p: 1,
              borderRadius: 1.5,
              bgcolor: 'error.light',
              color: 'error.contrastText',
              fontSize: '0.75rem',
              display: 'flex',
              justifyContent: 'space-between',
              alignItems: 'center',
            }}
          >
            <Typography variant="caption">{sendError}</Typography>
            <IconButton
              size="small"
              onClick={() => chatAutomat.setState({ sendError: null })}
              sx={{ color: 'inherit', p: 0.2 }}
            >
              <CloseRoundedIcon sx={{ fontSize: 14 }} />
            </IconButton>
          </Box>
        )}

        <Box sx={{ display: 'flex', alignItems: 'flex-end', gap: 1 }}>
          <TextInput
            inputRef={this.inputRef}
            multiline
            maxRows={4}
            fullWidth
            value={inputText}
            onChange={(e) => this.setState({ inputText: e.target.value })}
            onKeyDown={this.handleKeyDown}
            disabled={!canChat}
            placeholder={
              pendingAsk
                ? 'Bitte Frage oben beantworten…'
                : 'Nachricht eingeben…'
            }
          />

          <IconButton
            type="submit"
            color="primary"
            disabled={!canSend}
            title={
              isWorking
                ? 'Modell antwortet gerade…'
                : 'Senden (Enter)'
            }
            sx={{
              bgcolor: isWorking ? 'action.hover' : 'primary.main',
              color: isWorking ? 'warning.main' : 'primary.contrastText',
              width: 40,
              height: 40,
              borderRadius: 2.5,
              '&:hover': {
                bgcolor: 'primary.dark',
              },
              '&.Mui-disabled': {
                bgcolor: isWorking ? 'action.hover' : 'primary.main',
                color: isWorking ? 'warning.main' : 'primary.contrastText',
                cursor: 'default',
              },
            }}
          >
            {isWorking ? (
              <CircularProgress size={18} color="inherit" thickness={4.5} />
            ) : (
              <SendRoundedIcon sx={{ fontSize: 20 }} />
            )}
          </IconButton>
        </Box>

        <Typography variant="caption" sx={{ color: 'text.disabled', fontSize: '0.68rem', textAlign: 'center' }}>
          Enter zum Senden • Shift+Enter für Zeilenumbruch
        </Typography>
      </Box>
    );
  }

  render() {
    const { isOpen, drawerWidth, isResizing } = this.state;

    return (
      <>
        <Drawer
          anchor="right"
          open={isOpen}
          onClose={this.handleClose}
          sx={(theme) => ({
            zIndex: theme.zIndex.drawer + 2,
            '& .MuiDrawer-paper': {
              width: { xs: '100vw', sm: `${drawerWidth}px` },
              maxWidth: '100vw',
              display: 'flex',
              flexDirection: 'column',
              boxShadow: SHADOW_DRAWER,
              position: 'fixed',
              overflow: 'visible',
              transition: isResizing ? 'none !important' : undefined,
            },
          })}
          slotProps={{
            transition: {
              onEntered: () => this.focusInput(20),
            },
            paper: {
              sx: {
                width: { xs: '100vw', sm: `${drawerWidth}px` },
                maxWidth: '100vw',
                display: 'flex',
                flexDirection: 'column',
                boxShadow: SHADOW_DRAWER,
                position: 'fixed',
                overflow: 'visible',
                transition: isResizing ? 'none !important' : undefined,
              },
            },
          }}
        >
          {/* Draggable Resizer Handle */}
          <Box
            onPointerDown={this.handleResizeStart}
            onMouseDown={this.handleResizeStart}
            onTouchStart={this.handleResizeStart}
            onDoubleClick={this.handleResizeDoubleClick}
            title="Ziehen zum Anpassen der Breite • Doppelklick zum Zurücksetzen"
            sx={{
              position: 'absolute',
              top: 0,
              bottom: 0,
              left: 0,
              width: 16,
              cursor: 'col-resize',
              zIndex: 9999,
              display: { xs: 'none', sm: 'flex' },
              alignItems: 'center',
              justifyContent: 'center',
              touchAction: 'none',
              userSelect: 'none',
              '&:hover .drawer-resizer-line, &:active .drawer-resizer-line': {
                bgcolor: 'primary.main',
                height: 56,
                width: 4,
                opacity: 1,
                boxShadow: `0 0 10px ${BLUE_GLOW}`,
              },
            }}
          >
            <Box
              className="drawer-resizer-line"
              sx={{
                width: isResizing ? 4 : 3,
                height: isResizing ? 56 : 36,
                borderRadius: 2,
                bgcolor: isResizing ? 'primary.main' : 'divider',
                opacity: isResizing ? 1 : 0.6,
                transition: 'background-color 0.15s, height 0.15s, width 0.15s, opacity 0.15s, box-shadow 0.15s',
                boxShadow: isResizing ? `0 0 10px ${BLUE_GLOW}` : 'none',
              }}
            />
          </Box>

          {this.renderHeader()}
          {this.renderBody()}
          {this.renderFooter()}
        </Drawer>
      </>
    );
  }
}