import React, { useState, useMemo, useRef, useCallback } from 'react';
import {
    DndContext, DragOverlay, PointerSensor, TouchSensor,
    useSensor, useSensors, pointerWithin, rectIntersection
} from '@dnd-kit/core';
import { motion, AnimatePresence } from 'framer-motion';
import { useTheme } from '../context/ThemeContext';
import { useAuth, ROLES } from '../context/AuthContext';
import { useMockStore } from '../data/mockStore';
import { toast } from 'sonner';
import { LayoutGrid, Search, Filter, X, Send, Pencil, Plus } from 'lucide-react';

import KanbanCard, { KanbanCardDisplay } from '../components/kanban/KanbanCard';
import KanbanColumn from '../components/kanban/KanbanColumn';
import LeadInfoDrawer from '../components/kanban/LeadInfoDrawer';
import ColumnManagerModal from '../components/kanban/ColumnManagerModal';

// Campaign toast with countdown + Edit option
function fireCampaignToast(lead, column, onEdit) {
    if (!column?.campaignMessage) return;
    const msg = column.campaignMessage.replace('{name}', lead.name.split(' ')[0]);

    // Sonner v2: toast.custom(fn) where fn receives the toast ID directly (string)
    toast.custom((toastId) => {
        const [secs, setSecs] = React.useState(20);
        React.useEffect(() => {
            const t = setInterval(() => setSecs(s => {
                if (s <= 1) { clearInterval(t); toast.dismiss(toastId); return 0; }
                return s - 1;
            }), 1000);
            return () => clearInterval(t);
        }, []);
        return (
            <div className="flex flex-col gap-2 w-full bg-white dark:bg-zinc-900 border border-zinc-200 dark:border-white/10 rounded-2xl shadow-xl p-4">
                <div className="flex items-center justify-between gap-2">
                    <div className="flex items-center gap-1.5">
                        <Send size={13} className="text-blue-500 shrink-0" />
                        <p className="text-xs font-bold text-zinc-800 dark:text-zinc-100">Campaign Message</p>
                    </div>
                    <span className="text-[11px] font-bold text-zinc-400">Sending in {secs}s</span>
                </div>
                <p className="text-[11px] text-zinc-500 dark:text-zinc-400 line-clamp-2 leading-relaxed">{msg}</p>
                <div className="flex gap-2">
                    <button
                        onClick={() => { toast.dismiss(toastId); onEdit(msg, lead, column); }}
                        className="flex items-center gap-1 px-3 py-1.5 rounded-lg bg-blue-600 text-white text-[11px] font-semibold hover:bg-blue-700 transition-colors"
                    >
                        <Pencil size={10} /> Edit
                    </button>
                    <button
                        onClick={() => { toast.dismiss(toastId); toast.success('Campaign message sent'); }}
                        className="px-3 py-1.5 rounded-lg bg-zinc-100 dark:bg-zinc-800 text-zinc-600 dark:text-zinc-300 text-[11px] font-semibold hover:bg-zinc-200 dark:hover:bg-zinc-700 transition-colors"
                    >
                        Send Now
                    </button>
                </div>
            </div>
        );
    }, { duration: 20000, position: 'bottom-right' });
}

// Campaign Edit Modal
function CampaignEditModal({ message, lead, column, onClose }) {
    const [text, setText] = useState(message);
    return (
        <div className="fixed inset-0 z-[90] flex items-center justify-center p-4 bg-black/50 backdrop-blur-sm">
            <motion.div
                initial={{ scale: 0.95, opacity: 0 }}
                animate={{ scale: 1, opacity: 1 }}
                className="bg-white dark:bg-zinc-900 border border-zinc-200 dark:border-white/10 rounded-2xl shadow-2xl w-full max-w-md p-5"
                onClick={e => e.stopPropagation()}
            >
                <div className="flex items-center justify-between mb-4">
                    <div>
                        <h3 className="font-bold text-zinc-900 dark:text-white text-sm">Edit Campaign Message</h3>
                        <p className="text-[11px] text-zinc-400 mt-0.5">To: {lead?.name} · via {column?.name}</p>
                    </div>
                    <button onClick={onClose} className="p-1.5 rounded-lg text-zinc-400 hover:bg-zinc-100 dark:hover:bg-white/10 transition-colors"><X size={15} /></button>
                </div>
                <textarea
                    value={text}
                    onChange={e => setText(e.target.value)}
                    rows={5}
                    className="w-full px-3 py-2.5 rounded-xl border border-zinc-200 dark:border-zinc-700 bg-white dark:bg-zinc-800 text-zinc-900 dark:text-zinc-100 text-sm outline-none focus:ring-2 focus:ring-blue-500/30 resize-none mb-4"
                />
                <div className="flex gap-3">
                    <button onClick={onClose} className="flex-1 px-4 py-2 rounded-xl border border-zinc-200 dark:border-zinc-700 text-sm font-semibold text-zinc-600 dark:text-zinc-300 hover:bg-zinc-50 dark:hover:bg-white/5 transition-colors">Cancel</button>
                    <button
                        onClick={() => { toast.success('Campaign message sent'); onClose(); }}
                        className="flex-1 px-4 py-2 rounded-xl bg-blue-600 hover:bg-blue-700 text-white text-sm font-semibold transition-colors"
                    >
                        Send
                    </button>
                </div>
            </motion.div>
        </div>
    );
}

export default function KanbanPage() {
    const { theme } = useTheme();
    const { user } = useAuth();
    const {
        kanbanColumns, kanbanLeads,
        moveKanbanLead, addKanbanColumn, updateKanbanColumn, deleteKanbanColumn,
    } = useMockStore();

    const canManage = user?.role === ROLES.OWNER || user?.role === ROLES.ADMIN;

    const [search, setSearch] = useState('');
    const [selectedLead, setSelectedLead] = useState(null);
    const [drawerOpen, setDrawerOpen] = useState(false);

    // Column manager modal
    const [colModal, setColModal] = useState(null); // { mode: 'add'|'rename'|'delete', column?, leadsCount? }

    // Campaign edit modal
    const [campaignEdit, setCampaignEdit] = useState(null); // { message, lead, column }

    // Active drag — tracked so DragOverlay can render the floating clone
    const [draggingLead, setDraggingLead] = useState(null); // { lead, columnColor }

    const sensors = useSensors(
        useSensor(PointerSensor, { activationConstraint: { distance: 6 } }),
        useSensor(TouchSensor, { activationConstraint: { delay: 200, tolerance: 8 } })
    );

    const stageColumns = useMemo(() =>
        [...kanbanColumns].filter(c => c.type === 'stage').sort((a, b) => a.order - b.order),
    [kanbanColumns]);

    const bucketColumns = useMemo(() =>
        [...kanbanColumns].filter(c => c.type === 'bucket').sort((a, b) => a.order - b.order),
    [kanbanColumns]);

    const allColumns = useMemo(() => [...stageColumns, ...bucketColumns], [stageColumns, bucketColumns]);

    const filteredLeads = useMemo(() => {
        if (!search.trim()) return kanbanLeads;
        const q = search.toLowerCase();
        return kanbanLeads.filter(l =>
            l.name.toLowerCase().includes(q) ||
            l.address.toLowerCase().includes(q) ||
            (l.assignedAgentName || '').toLowerCase().includes(q) ||
            l.jobType.toLowerCase().includes(q)
        );
    }, [kanbanLeads, search]);

    const leadsForColumn = useCallback((colId) => {
        return filteredLeads.filter(l => {
            const col = kanbanColumns.find(c => c.id === colId);
            if (col?.type === 'bucket') return l.bucketId === colId;
            return l.columnId === colId && !l.bucketId;
        });
    }, [filteredLeads, kanbanColumns]);

    const handleDragStart = ({ active }) => {
        const lead = kanbanLeads.find(l => l.id === active.id);
        if (!lead) return;
        const col = kanbanColumns.find(c => c.id === lead.columnId);
        setDraggingLead({ lead, columnColor: col?.color ?? '#6366f1' });
    };

    const handleDragEnd = ({ active, over }) => {
        setDraggingLead(null);
        if (!over || active.id === over.id) return;

        const targetCol = kanbanColumns.find(c => c.id === over.id);
        if (!targetCol) return;

        const lead = kanbanLeads.find(l => l.id === active.id);
        if (!lead) return;

        const isBucket = targetCol.type === 'bucket';
        const newColumnId = isBucket ? lead.columnId : targetCol.id;
        const newBucketId = isBucket ? targetCol.id : null;

        if (newColumnId === lead.columnId && newBucketId === lead.bucketId) return;

        moveKanbanLead(active.id, newColumnId, newBucketId);

        // Fire campaign toast for stage drops only
        if (!isBucket) {
            setTimeout(() => {
                fireCampaignToast(lead, targetCol, (msg, l, col) => {
                    setCampaignEdit({ message: msg, lead: l, column: col });
                });
            }, 300);
        }
    };

    const openCard = (lead) => {
        setSelectedLead(lead);
        setDrawerOpen(true);
    };

    // Column manager handlers
    const handleAddColumn = () => setColModal({ mode: 'add' });
    const handleRenameColumn = (col) => setColModal({ mode: 'rename', column: col });
    const handleDeleteColumn = (col) => {
        const count = leadsForColumn(col.id).length;
        setColModal({ mode: 'delete', column: col, leadsCount: count });
    };

    const handleColModalSave = (data) => {
        const { mode, column } = colModal;
        if (mode === 'add') {
            const maxOrder = Math.max(...stageColumns.map(c => c.order), 0);
            addKanbanColumn({ ...data, type: 'stage', order: maxOrder + 1 });
            toast.success(`"${data.name}" stage added`);
        } else if (mode === 'rename') {
            updateKanbanColumn(column.id, data);
            toast.success('Stage updated');
        } else if (mode === 'delete') {
            deleteKanbanColumn(column.id);
            toast.success(`"${column.name}" deleted`);
        }
        setColModal(null);
    };

    return (
        <DndContext
            sensors={sensors}
            collisionDetection={(args) => pointerWithin(args).length > 0 ? pointerWithin(args) : rectIntersection(args)}
            onDragStart={handleDragStart}
            onDragEnd={handleDragEnd}
        >
        <div className={`h-full flex flex-col bg-zinc-50 dark:bg-[#09090b] ${theme === 'dark' ? 'dark' : ''}`}>
            {/* Page header */}
            <div className="shrink-0 px-4 sm:px-6 py-4 border-b border-zinc-200 dark:border-white/[0.07] bg-white dark:bg-zinc-950 z-20">
                <div className="flex items-center gap-3 flex-wrap">
                    <div className="flex items-center gap-3 shrink-0">
                        <div className="w-8 h-8 rounded-xl bg-blue-50 dark:bg-blue-500/10 flex items-center justify-center">
                            <LayoutGrid size={16} className="text-blue-600 dark:text-blue-400" />
                        </div>
                        <div>
                            <h1 className="text-xl font-black uppercase tracking-tight text-zinc-900 dark:text-white leading-none"
                                style={{ fontFamily: 'Barlow Condensed, sans-serif' }}>
                                Pipeline
                            </h1>
                            <p className="text-xs text-zinc-400 mt-0.5">{kanbanLeads.length} leads · {stageColumns.length} stages</p>
                        </div>
                    </div>

                    {/* Add Stage — header shortcut for owners/admins */}
                    {canManage && (
                        <button
                            onClick={handleAddColumn}
                            className="shrink-0 flex items-center gap-1.5 px-3 py-2 rounded-xl border border-dashed border-zinc-300 dark:border-zinc-700 text-zinc-500 dark:text-zinc-400 hover:text-zinc-700 dark:hover:text-zinc-200 hover:border-zinc-400 dark:hover:border-zinc-500 text-xs font-semibold transition-colors"
                        >
                            <Plus size={12} /> Add Stage
                        </button>
                    )}

                    {/* Search */}
                    <div className="relative flex-1 min-w-[180px] max-w-xs ml-auto">
                        <Search size={13} className="absolute left-3 top-1/2 -translate-y-1/2 text-zinc-400 pointer-events-none" />
                        <input
                            value={search}
                            onChange={e => setSearch(e.target.value)}
                            placeholder="Search leads..."
                            className="w-full pl-8 pr-4 py-2 rounded-xl border border-zinc-200 dark:border-zinc-700 bg-zinc-50 dark:bg-zinc-900 text-zinc-900 dark:text-zinc-100 text-sm outline-none focus:ring-2 focus:ring-blue-500/30 focus:border-blue-500 transition-shadow"
                        />
                        {search && (
                            <button onClick={() => setSearch('')} className="absolute right-2.5 top-1/2 -translate-y-1/2 text-zinc-400 hover:text-zinc-600 dark:hover:text-zinc-200">
                                <X size={12} />
                            </button>
                        )}
                    </div>
                </div>
            </div>

            {/* Board — fills remaining height, horizontal scroll only */}
            <div className="flex-1 overflow-x-auto overflow-y-hidden min-h-0">
                <div className="flex gap-4 px-4 sm:px-6 py-5 min-w-max h-full">
                        {/* Stage columns */}
                        {stageColumns.map((col, i) => (
                            <KanbanColumn
                                key={col.id}
                                column={col}
                                leads={leadsForColumn(col.id)}
                                stageColumns={stageColumns}
                                canManage={canManage}
                                onCardClick={openCard}
                                onAddColumn={handleAddColumn}
                                onRenameColumn={handleRenameColumn}
                                onDeleteColumn={handleDeleteColumn}
                                isLast={i === stageColumns.length - 1}
                            />
                        ))}

                        {/* Divider */}
                        <div className="shrink-0 self-stretch flex items-stretch px-2">
                            <div className="w-px bg-zinc-200 dark:bg-zinc-800" />
                        </div>

                        {/* Bucket columns */}
                        {bucketColumns.map((col) => (
                            <KanbanColumn
                                key={col.id}
                                column={col}
                                leads={leadsForColumn(col.id)}
                                stageColumns={allColumns}
                                canManage={false}
                                onCardClick={openCard}
                                onAddColumn={() => {}}
                                onRenameColumn={() => {}}
                                onDeleteColumn={() => {}}
                                isLast={false}
                            />
                        ))}
                </div>
            </div>

            {/* Lead info drawer */}
            <LeadInfoDrawer
                lead={selectedLead}
                columns={kanbanColumns}
                isOpen={drawerOpen}
                onClose={() => setDrawerOpen(false)}
            />

            {/* Column manager modal */}
            <AnimatePresence>
                {colModal && (
                    <ColumnManagerModal
                        mode={colModal.mode}
                        column={colModal.column}
                        leadsInColumn={colModal.leadsCount ?? 0}
                        onSave={handleColModalSave}
                        onClose={() => setColModal(null)}
                    />
                )}
            </AnimatePresence>

            {/* Campaign edit modal */}
            <AnimatePresence>
                {campaignEdit && (
                    <CampaignEditModal
                        {...campaignEdit}
                        onClose={() => setCampaignEdit(null)}
                    />
                )}
            </AnimatePresence>
        </div>

        {/* DragOverlay — dnd-kit already portals this to document.body internally,
            so position:fixed is always viewport-relative regardless of ancestors. */}
        <DragOverlay dropAnimation={null}>
            {draggingLead ? (
                <KanbanCardDisplay
                    lead={draggingLead.lead}
                    columnColor={draggingLead.columnColor}
                    isOverlay
                />
            ) : null}
        </DragOverlay>
        </DndContext>
    );
}