'use client';

import { useState, useEffect, useMemo } from 'react';
import { useRouter } from 'next/navigation';
import {
  Plus,
  Search,
  GripVertical,
  ChevronRight,
  Pencil,
  Trash2,
  X,
  AlertTriangle,
  Package,
} from 'lucide-react';
import {
  DndContext,
  closestCenter,
  KeyboardSensor,
  PointerSensor,
  useSensor,
  useSensors,
  DragEndEvent,
} from '@dnd-kit/core';
import {
  SortableContext,
  sortableKeyboardCoordinates,
  verticalListSortingStrategy,
  useSortable,
} from '@dnd-kit/sortable';
import { CSS } from '@dnd-kit/utilities';
import { useProductStore } from '@/stores/useProductStore';
import { ProductForm } from '@/components/product/ProductForm';
import { VersionChip } from '@/components/version/VersionChip';
import type { VersionStatus } from '@/lib/version-status';

type ProductOverview = {
  id: string;
  name: string;
  description: string;
  projects: { id: string; name: string; description: string; createdAt: string }[];
  versions: {
    id: string;
    name: string;
    status?: string;
    releaseDate: string | null;
    createdAt: string;
  }[];
  _count?: { requirements: number; projects: number; versions?: number };
};

/* ─── Sortable Product Row ─── */
function SortableProductRow({
  product,
  expanded,
  onToggle,
  onEdit,
  onDelete,
  router,
}: {
  product: ProductOverview;
  expanded: boolean;
  onToggle: () => void;
  onEdit: () => void;
  onDelete: () => void;
  router: ReturnType<typeof useRouter>;
}) {
  const { attributes, listeners, setNodeRef, transform, transition, isDragging } =
    useSortable({ id: product.id });

  const style = {
    transform: CSS.Transform.toString(transform),
    transition,
    opacity: isDragging ? 0.5 : 1,
  };

  const activeVersions = product.versions.filter(
    (v) => v.status === 'developing'
  );
  const releasedCount = product.versions.filter((v) => v.status === 'released').length;

  return (
    <div
      ref={setNodeRef}
      style={style}
      className="border-b border-[var(--line-soft)] last:border-b-0"
    >
      <div className="flex items-center gap-2 px-4 py-3 group">
        <button
          {...attributes}
          {...listeners}
          className="cursor-grab active:cursor-grabbing p-1 rounded hover:bg-[var(--bg-hover)] text-[var(--ink-muted)] opacity-0 group-hover:opacity-100 transition-opacity"
          aria-label="拖拽排序"
        >
          <GripVertical className="w-4 h-4" />
        </button>

        <div
          className="flex-1 flex items-center gap-2 cursor-pointer min-w-0"
          onClick={onToggle}
        >
          <ChevronRight
            className={`w-4 h-4 text-[var(--ink-muted)] transition-transform duration-150 ${
              expanded ? 'rotate-90' : ''
            }`}
          />
          <span className="text-[13px] font-medium truncate">{product.name}</span>
          {product.description && (
            <span className="text-[12px] text-[var(--ink-muted)] truncate hidden sm:inline">
              {product.description}
            </span>
          )}
        </div>

        <div className="flex items-center gap-1">
          <button
            onClick={onEdit}
            className="p-1.5 rounded-md hover:bg-[var(--bg-hover)] text-[var(--ink-muted)] hover:text-[var(--ink)] opacity-0 group-hover:opacity-100 transition-all"
            aria-label="编辑"
          >
            <Pencil className="w-3.5 h-3.5" />
          </button>
          <button
            onClick={onDelete}
            className="p-1.5 rounded-md hover:bg-red-50 text-[var(--ink-muted)] hover:text-red-600 opacity-0 group-hover:opacity-100 transition-all"
            aria-label="删除"
          >
            <Trash2 className="w-3.5 h-3.5" />
          </button>
        </div>

        <div className="flex items-center gap-3 text-[11px] text-[var(--ink-muted)] ml-2 pl-2 border-l border-[var(--line-soft)]">
          <span className="hidden md:inline">{product._count?.projects ?? product.projects.length} 项目</span>
          <span className="hidden md:inline">{product._count?.versions ?? product.versions.length} 版本</span>
          {product._count?.requirements != null && (
            <span className="hidden md:inline">{product._count.requirements} 需求</span>
          )}
        </div>
      </div>

      {expanded && (
        <div className="bg-[var(--bg-subtle)] border-t border-[var(--line-soft)]">
          {product.projects.length === 0 ? (
            <div className="px-12 py-6 text-[12px] text-[var(--ink-muted)] text-center">
              暂无项目
            </div>
          ) : (
            <div className="px-12 py-2">
              {product.projects.map((proj) => {
                const projVersions = product.versions.filter((v) =>
                  v.name.toLowerCase().startsWith(proj.name.toLowerCase())
                );
                const projActive = projVersions.filter(
                  (v) => v.status === 'developing'
                );
                const projReleased = projVersions.filter((v) => v.status === 'released').length;
                return (
                  <div
                    key={proj.id}
                    className="flex items-center gap-3 py-2 border-b border-[var(--line-soft)] last:border-b-0"
                  >
                    <button
                      onClick={() => router.push(`/projects/${proj.id}`)}
                      className="text-[12px] font-medium text-[var(--ink-soft)] hover:text-[var(--accent)] hover:underline min-w-0 flex-shrink-0 cursor-pointer"
                    >
                      {proj.name}
                    </button>
                    {proj.description && (
                      <span className="text-[11px] text-[var(--ink-muted)] truncate hidden lg:inline">
                        {proj.description}
                      </span>
                    )}
                    <div className="flex-1 flex items-center gap-1.5 flex-wrap justify-end">
                      {projActive.map((v) => (
                        <button
                          key={v.id}
                          onClick={() => router.push(`/versions/${v.id}`)}
                          className="hover:opacity-80 transition-opacity"
                        >
                          <VersionChip
                            name={v.name}
                            status={(v.status as VersionStatus) ?? 'developing'}
                          />
                        </button>
                      ))}
                      {projReleased > 0 && (
                        <span className="text-[11px] text-[var(--ink-muted)] px-1.5">
                          已发布 {projReleased}
                        </span>
                      )}
                    </div>
                  </div>
                );
              })}
            </div>
          )}
        </div>
      )}
    </div>
  );
}

/* ─── Edit Product Modal ─── */
function EditProductModal({
  product,
  onClose,
  onSubmit,
}: {
  product: ProductOverview;
  onClose: () => void;
  onSubmit: (data: { name: string; description: string }) => void | Promise<void>;
}) {
  return (
    <div
      className="fixed inset-0 z-50 flex items-center justify-center bg-black/40 p-4"
      onClick={onClose}
    >
      <div
        className="w-full max-w-md rounded-2xl bg-[var(--bg-card)] border border-[var(--line)] shadow-[var(--shadow-md)] overflow-hidden"
        onClick={(e) => e.stopPropagation()}
      >
        <div className="flex items-center justify-between px-5 py-3.5 border-b border-[var(--line)]">
          <h3 className="text-[13px] font-semibold">编辑产品</h3>
          <button
            onClick={onClose}
            className="p-1 rounded-md hover:bg-[var(--bg-hover)] text-[var(--ink-muted)] hover:text-[var(--ink)]"
            aria-label="关闭"
          >
            <X className="w-4 h-4" />
          </button>
        </div>
        <div className="p-5">
          <ProductForm
            initialData={{ name: product.name, description: product.description }}
            onSubmit={onSubmit}
            onCancel={onClose}
          />
        </div>
      </div>
    </div>
  );
}

/* ─── Migrate Dialog ─── */
function MigrateDialog({
  source,
  others,
  onClose,
  onConfirm,
}: {
  source: ProductOverview;
  others: ProductOverview[];
  onClose: () => void;
  onConfirm: (targetId: string) => void | Promise<void>;
}) {
  const [targetId, setTargetId] = useState('');
  const activeVersions = source.versions.filter(
    (v) => v.status === 'developing' || v.status === 'planned'
  );

  return (
    <div
      className="fixed inset-0 z-50 flex items-center justify-center bg-black/40 p-4"
      onClick={onClose}
    >
      <div
        className="w-full max-w-md rounded-2xl bg-[var(--bg-card)] border border-[var(--line)] shadow-[var(--shadow-md)] overflow-hidden"
        onClick={(e) => e.stopPropagation()}
      >
        <div className="flex items-center justify-between px-5 py-3.5 border-b border-[var(--line)]">
          <h3 className="text-[13px] font-semibold">删除产品</h3>
          <button
            onClick={onClose}
            className="p-1 rounded-md hover:bg-[var(--bg-hover)] text-[var(--ink-muted)] hover:text-[var(--ink)]"
            aria-label="关闭"
          >
            <X className="w-4 h-4" />
          </button>
        </div>
        <div className="p-5 space-y-4">
          <div className="flex items-start gap-3 p-3 rounded-xl bg-amber-50 border border-amber-200">
            <AlertTriangle className="w-5 h-5 text-amber-600 flex-shrink-0 mt-0.5" />
            <div className="text-[13px] text-amber-800">
              <p className="font-medium mb-1">
                该产品下还有 {activeVersions.length} 个未发布版本
              </p>
              <ul className="space-y-0.5 text-[12px]">
                {activeVersions.map((v) => (
                  <li key={v.id}>· {v.name}</li>
                ))}
              </ul>
            </div>
          </div>

          <div>
            <label className="block text-[12px] text-[var(--ink-soft)] mb-1.5 font-medium">
              迁移至
            </label>
            <select
              value={targetId}
              onChange={(e) => setTargetId(e.target.value)}
              className="w-full h-9 px-3 rounded-lg border border-[var(--line)] bg-[var(--bg-card)] text-[13px] focus:outline-none focus:border-[var(--accent)] focus:ring-2 focus:ring-[var(--accent-ring)]"
            >
              <option value="">选择目标产品...</option>
              {others.map((p) => (
                <option key={p.id} value={p.id}>{p.name}</option>
              ))}
            </select>
          </div>

          <div className="flex items-center justify-end gap-2 pt-1">
            <button
              onClick={onClose}
              className="h-8 px-3 rounded-lg border border-[var(--line)] bg-[var(--bg-card)] hover:bg-[var(--bg-hover)] text-[13px] text-[var(--ink-soft)] transition-colors"
            >
              取消
            </button>
            <button
              onClick={() => targetId && onConfirm(targetId)}
              disabled={!targetId || others.length === 0}
              className="h-8 px-3 rounded-lg bg-red-600 hover:bg-red-700 disabled:bg-zinc-300 disabled:cursor-not-allowed text-white text-[13px] font-medium transition-colors"
            >
              迁移并删除
            </button>
          </div>
        </div>
      </div>
    </div>
  );
}

/* ─── Main Page ─── */
export default function ProductsPage() {
  const router = useRouter();
  const {
    overview,
    loading,
    fetchOverview,
    createProduct,
    updateProduct,
    deleteProduct,
    reorderProducts,
    migrateAndDeleteProduct,
  } = useProductStore();

  const [search, setSearch] = useState('');
  const [showCreate, setShowCreate] = useState(false);
  const [expanded, setExpanded] = useState<Set<string>>(new Set());
  const [editing, setEditing] = useState<ProductOverview | null>(null);
  const [migrateTarget, setMigrateTarget] = useState<ProductOverview | null>(null);
  const [hasInitialized, setHasInitialized] = useState(false);

  useEffect(() => {
    fetchOverview();
  }, [fetchOverview]);

  useEffect(() => {
    if (!hasInitialized && overview.length > 0) {
      setExpanded(new Set([overview[0].id]));
      setHasInitialized(true);
    }
  }, [overview, hasInitialized]);

  const sensors = useSensors(
    useSensor(PointerSensor, { activationConstraint: { distance: 5 } }),
    useSensor(KeyboardSensor, { coordinateGetter: sortableKeyboardCoordinates })
  );

  const filtered = useMemo(() => {
    if (!search.trim()) return overview;
    const q = search.toLowerCase();
    return overview.filter(
      (p) =>
        p.name.toLowerCase().includes(q) ||
        (p.description ?? '').toLowerCase().includes(q)
    );
  }, [overview, search]);

  const handleDragEnd = (event: DragEndEvent) => {
    const { active, over } = event;
    if (!over || active.id === over.id) return;
    const oldIndex = overview.findIndex((p) => p.id === active.id);
    const newIndex = overview.findIndex((p) => p.id === over.id);
    if (oldIndex < 0 || newIndex < 0) return;
    const next = [...overview];
    const [moved] = next.splice(oldIndex, 1);
    next.splice(newIndex, 0, moved);
    reorderProducts(next.map((p) => p.id));
  };

  const toggleExpand = (id: string) => {
    setExpanded((prev) => {
      const n = new Set(prev);
      if (n.has(id)) n.delete(id);
      else n.add(id);
      return n;
    });
  };

  const handleDelete = (product: ProductOverview) => {
    const active = product.versions.filter(
      (v) => v.status === 'developing' || v.status === 'planned'
    );
    if (active.length === 0) {
      if (confirm(`确认删除产品「${product.name}」？此操作不可撤销。`)) {
        deleteProduct(product.id);
      }
    } else {
      setMigrateTarget(product);
    }
  };

  return (
    <div className="flex h-full flex-col bg-[var(--bg)] text-[var(--ink)]">
      {/* Header */}
      <div className="h-14 shrink-0 flex items-center justify-between px-5 border-b border-[var(--line)] bg-[var(--bg-card)]">
        <div className="flex items-center gap-2.5">
          <h1 className="text-[15px] font-semibold tracking-tight">产品</h1>
          <span className="inline-flex items-center justify-center min-w-[22px] h-[22px] px-1.5 rounded-full bg-[var(--bg-subtle)] text-[var(--ink-soft)] text-[11px] font-medium">
            {overview.length}
          </span>
        </div>
        <button
          onClick={() => setShowCreate((v) => !v)}
          className="inline-flex items-center gap-1.5 h-8 px-3 rounded-lg bg-[var(--accent)] hover:bg-[var(--accent-hover)] text-white text-[13px] font-medium shadow-[var(--shadow-sm)] transition-colors"
        >
          <Plus className="w-4 h-4" />
          新建产品
        </button>
      </div>

      {/* Filters */}
      <div className="flex shrink-0 items-center gap-3 border-b border-[var(--line)] bg-[var(--bg-card)] px-5 py-3">
        <div className="relative flex-1 max-w-sm">
          <Search className="absolute left-3 top-1/2 -translate-y-1/2 w-4 h-4 text-[var(--ink-muted)]" />
          <input
            value={search}
            onChange={(e) => setSearch(e.target.value)}
            placeholder="搜索产品..."
            className="w-full h-8 pl-9 pr-3 rounded-lg border border-[var(--line)] bg-[var(--bg)] text-[13px] placeholder:text-[var(--ink-muted)] focus:outline-none focus:border-[var(--accent)] focus:ring-2 focus:ring-[var(--accent-ring)] transition-colors"
          />
        </div>
        <div className="ml-auto flex items-center gap-3 text-[12px] text-[var(--ink-muted)]">
          <span className="inline-flex items-center gap-1.5">
            <span className="w-1.5 h-1.5 rounded-full bg-[#2563eb]" />开发中
          </span>
          <span className="inline-flex items-center gap-1.5">
            <span className="w-1.5 h-1.5 rounded-full bg-zinc-400" />已发布
          </span>
        </div>
      </div>

      {/* Content */}
      <div className="flex-1 overflow-y-auto bg-[var(--bg)] px-5 py-4">

        {/* Inline Create Form */}
        {showCreate && (
          <div className="mb-3 rounded-2xl border border-[var(--line)] bg-[var(--bg-card)] p-4 shadow-[var(--shadow-sm)]">
            <div className="flex items-center justify-between mb-3">
              <h3 className="text-[13px] font-semibold">新建产品</h3>
              <button
                onClick={() => setShowCreate(false)}
                className="p-1 rounded-md hover:bg-[var(--bg-hover)] text-[var(--ink-muted)] hover:text-[var(--ink)]"
              >
                <X className="w-4 h-4" />
              </button>
            </div>
            <ProductForm
              onSubmit={async (data) => {
                await createProduct(data);
                setShowCreate(false);
              }}
              onCancel={() => setShowCreate(false)}
            />
          </div>
        )}

        {/* Product List */}
        <div className="rounded-2xl border border-[var(--line)] bg-[var(--bg-card)] overflow-hidden shadow-[var(--shadow-sm)]">
          {loading && overview.length === 0 ? (
            <div className="py-16 text-center text-[13px] text-[var(--ink-muted)]">加载中...</div>
          ) : filtered.length === 0 ? (
            <div className="py-16 text-center text-[13px] text-[var(--ink-muted)]">
              <Package className="w-10 h-10 mx-auto mb-2 opacity-40" />
              暂无产品
            </div>
          ) : (
            <DndContext
              sensors={sensors}
              collisionDetection={closestCenter}
              onDragEnd={handleDragEnd}
            >
              <SortableContext
                items={filtered.map((p) => p.id)}
                strategy={verticalListSortingStrategy}
              >
                {filtered.map((product) => (
                  <SortableProductRow
                    key={product.id}
                    product={product}
                    expanded={expanded.has(product.id)}
                    onToggle={() => toggleExpand(product.id)}
                    onEdit={() => setEditing(product)}
                    onDelete={() => handleDelete(product)}
                    router={router}
                  />
                ))}
              </SortableContext>
            </DndContext>
          )}
        </div>
      </div>

      {/* Edit Modal */}
      {editing && (
        <EditProductModal
          product={editing}
          onClose={() => setEditing(null)}
          onSubmit={async (data) => {
            await updateProduct(editing.id, data);
            setEditing(null);
          }}
        />
      )}

      {/* Migrate Dialog */}
      {migrateTarget && (
        <MigrateDialog
          source={migrateTarget}
          others={overview.filter((p) => p.id !== migrateTarget.id)}
          onClose={() => setMigrateTarget(null)}
          onConfirm={async (targetId) => {
            await migrateAndDeleteProduct(migrateTarget.id, targetId);
            setMigrateTarget(null);
          }}
        />
      )}
    </div>
  );
}