import React, { useState, useEffect } from 'react';
import {
  Shield,
  Plus,
  Save,
  X,
  Edit2,
  Trash2,
  Loader2,
  Check,
  Users,
  Key,
} from 'lucide-react';
import { useAuth } from '../../src/contexts/AuthContext';
import { useConfirm } from '../../contexts/ConfirmContext';
import { useToast } from '../../contexts/ToastContext';
import { useLanguage } from '../../contexts/LanguageContext';
import { cn } from '../../src/utils/cn';

interface PermissionMeta {
  key: string;
  category: string;
  label: string;
  description: string;
}

interface Role {
  id: string;
  name: string;
  description?: string;
  isSystem: boolean;
  baseRole?: string;
  tenantId?: string;
}

/** 按分类分组的权限 */
interface PermissionsByCategory {
  [category: string]: PermissionMeta[];
}

export const PermissionSettingsView: React.FC = () => {
  const { apiKey, activeTenant } = useAuth();
  const { confirm } = useConfirm();
  const { showError, showSuccess } = useToast();
  const { t } = useLanguage();

  const [roles, setRoles] = useState<Role[]>([]);
  const [allPermissions, setAllPermissions] = useState<PermissionsByCategory>({});
  const [selectedRoleId, setSelectedRoleId] = useState<string | null>(null);
  const [rolePermissions, setRolePermissions] = useState<Set<string>>(new Set());
  const [isLoadingRoles, setIsLoadingRoles] = useState(true);
  const [isLoadingPerms, setIsLoadingPerms] = useState(false);
  const [isSaving, setIsSaving] = useState(false);
  const [showCreateRole, setShowCreateRole] = useState(false);
  const [newRoleName, setNewRoleName] = useState('');
  const [newRoleDesc, setNewRoleDesc] = useState('');
  const [editingPermissions, setEditingPermissions] = useState<Set<string>>(new Set());
  const [hasChanges, setHasChanges] = useState(false);

  const headers = {
    'x-api-key': apiKey,
    'x-tenant-id': activeTenant?.tenantId || '',
  };

  // 加载角色列表
  const fetchRoles = async () => {
    try {
      setIsLoadingRoles(true);
      const res = await fetch('/api/roles', { headers });
      if (res.ok) {
        const data = await res.json();
        setRoles(data);
      }
    } catch (err: any) {
      console.error('Failed to fetch roles:', err);
    } finally {
      setIsLoadingRoles(false);
    }
  };

  // 加载权限元数据
  const fetchPermissions = async () => {
    try {
      const res = await fetch('/api/permissions', { headers });
      if (res.ok) {
        const data = await res.json();
        setAllPermissions(data);
      }
    } catch (err: any) {
      console.error('Failed to fetch permissions:', err);
    }
  };

  // 加载选中角色的权限
  const fetchRolePermissions = async (roleId: string) => {
    try {
      setIsLoadingPerms(true);
      const res = await fetch(`/api/roles/${roleId}/permissions`, { headers });
      if (res.ok) {
        const data = await res.json();
        const permSet = new Set<string>(data.permissions || []);
        setRolePermissions(permSet);
        setEditingPermissions(new Set(permSet));
      }
    } catch (err: any) {
      console.error('Failed to fetch role permissions:', err);
    } finally {
      setIsLoadingPerms(false);
    }
  };

  useEffect(() => {
    fetchRoles();
    fetchPermissions();
  }, [apiKey, activeTenant]);

  useEffect(() => {
    if (selectedRoleId) {
      fetchRolePermissions(selectedRoleId);
    }
  }, [selectedRoleId]);

  // 切换权限
  const togglePermission = (key: string) => {
    setEditingPermissions(prev => {
      const next = new Set(prev);
      if (next.has(key)) {
        next.delete(key);
      } else {
        next.add(key);
      }
      setHasChanges(true);
      return next;
    });
  };

  // 全选/取消分类
  const toggleCategory = (category: string, perms: PermissionMeta[]) => {
    const keys = perms.map(p => p.key);
    const allChecked = keys.every(k => editingPermissions.has(k));
    setEditingPermissions(prev => {
      const next = new Set(prev);
      keys.forEach(k => {
        if (allChecked) next.delete(k);
        else next.add(k);
      });
      setHasChanges(true);
      return next;
    });
  };

  // 保存权限
  const savePermissions = async () => {
    if (!selectedRoleId) return;
    try {
      setIsSaving(true);
      const res = await fetch(`/api/roles/${selectedRoleId}/permissions`, {
        method: 'PUT',
        headers: { ...headers, 'Content-Type': 'application/json' },
        body: JSON.stringify({ permissions: [...editingPermissions] }),
      });
      if (res.ok) {
        setRolePermissions(new Set(editingPermissions));
        setHasChanges(false);
        showSuccess?.('权限已保存');
      } else {
        const err = await res.json();
        throw new Error(err.message || '保存失败');
      }
    } catch (err: any) {
      showError?.(err.message);
    } finally {
      setIsSaving(false);
    }
  };

  // 创建角色
  const createRole = async () => {
    if (!newRoleName.trim()) return;
    try {
      const res = await fetch('/api/roles', {
        method: 'POST',
        headers: { ...headers, 'Content-Type': 'application/json' },
        body: JSON.stringify({ name: newRoleName.trim(), description: newRoleDesc.trim() }),
      });
      if (res.ok) {
        await fetchRoles();
        setShowCreateRole(false);
        setNewRoleName('');
        setNewRoleDesc('');
        showSuccess?.('角色已创建');
      } else {
        const err = await res.json();
        throw new Error(err.message || '创建失败');
      }
    } catch (err: any) {
      showError?.(err.message);
    }
  };

  // 删除角色
  const deleteRole = async (role: Role) => {
    const confirmed = await confirm?.(`确定删除角色"${role.name}"？`);
    if (!confirmed) return;
    try {
      const res = await fetch(`/api/roles/${role.id}`, { method: 'DELETE', headers });
      if (res.ok) {
        if (selectedRoleId === role.id) setSelectedRoleId(null);
        await fetchRoles();
        showSuccess?.('角色已删除');
      } else {
        const err = await res.json();
        throw new Error(err.message || '删除失败');
      }
    } catch (err: any) {
      showError?.(err.message);
    }
  };

  const selectedRole = roles.find(r => r.id === selectedRoleId);

  return (
    <div className="flex h-full gap-6">
      {/* 左：角色列表 */}
      <div className="w-72 flex-none space-y-3">
        <div className="flex items-center justify-between mb-4">
          <h3 className="text-sm font-black text-slate-900 flex items-center gap-2 uppercase tracking-widest">
            <Shield size={16} className="text-indigo-600" />
            角色
          </h3>
          <button
            onClick={() => setShowCreateRole(true)}
            className="p-1.5 rounded-lg bg-indigo-50 text-indigo-600 hover:bg-indigo-100 transition-colors"
            title="新建角色"
          >
            <Plus size={16} />
          </button>
        </div>

        {isLoadingRoles ? (
          <div className="flex justify-center py-8">
            <Loader2 size={20} className="animate-spin text-slate-400" />
          </div>
        ) : (
          <div className="space-y-1">
            {roles.map(role => (
              <button
                key={role.id}
                onClick={() => setSelectedRoleId(role.id)}
                className={cn(
                  'w-full text-left px-4 py-3 rounded-xl text-sm font-medium transition-all flex items-center justify-between',
                  selectedRoleId === role.id
                    ? 'bg-indigo-50 text-indigo-700 border border-indigo-200 shadow-sm'
                    : 'text-slate-600 hover:bg-slate-50 border border-transparent',
                )}
              >
                <div className="flex items-center gap-2 min-w-0">
                  <span className="truncate">{role.name}</span>
                  {role.isSystem && (
                    <span className="text-xs font-black text-indigo-400 bg-indigo-100/50 px-1.5 py-0.5 rounded uppercase tracking-wider shrink-0">
                      系统
                    </span>
                  )}
                </div>
                {!role.isSystem && (
                  <button
                    onClick={(e) => { e.stopPropagation(); deleteRole(role); }}
                    className="p-1 text-slate-300 hover:text-rose-500 transition-colors shrink-0"
                  >
                    <Trash2 size={14} />
                  </button>
                )}
              </button>
            ))}
          </div>
        )}

        {/* 创建角色弹窗 */}
        {showCreateRole && (
          <div className="bg-slate-50 rounded-xl p-4 border border-slate-200 space-y-3">
            <input
              value={newRoleName}
              onChange={e => setNewRoleName(e.target.value)}
              placeholder="角色名称"
              className="w-full px-3 py-2 text-sm bg-white border border-slate-200 rounded-lg focus:ring-2 focus:ring-indigo-500/20 focus:border-indigo-500 outline-none"
            />
            <input
              value={newRoleDesc}
              onChange={e => setNewRoleDesc(e.target.value)}
              placeholder="角色描述（可选）"
              className="w-full px-3 py-2 text-sm bg-white border border-slate-200 rounded-lg focus:ring-2 focus:ring-indigo-500/20 focus:border-indigo-500 outline-none"
            />
            <div className="flex gap-2">
              <button
                onClick={createRole}
                disabled={!newRoleName.trim()}
                className="flex-1 py-2 bg-indigo-600 text-white text-xs font-bold rounded-lg hover:bg-indigo-700 disabled:bg-slate-300 disabled:cursor-not-allowed transition-colors"
              >
                创建
              </button>
              <button
                onClick={() => setShowCreateRole(false)}
                className="px-3 py-2 text-xs font-bold text-slate-500 hover:text-slate-700 bg-white border border-slate-200 rounded-lg transition-colors"
              >
                取消
              </button>
            </div>
          </div>
        )}
      </div>

      {/* 右：权限矩阵 */}
      <div className="flex-1 min-w-0">
        {!selectedRole ? (
          <div className="flex flex-col items-center justify-center h-full text-slate-400 space-y-3">
            <Shield size={40} className="opacity-30" />
            <p className="text-sm font-bold">选择一个角色查看权限</p>
          </div>
        ) : isLoadingPerms ? (
          <div className="flex justify-center py-12">
            <Loader2 size={24} className="animate-spin text-slate-400" />
          </div>
        ) : (
          <div className="space-y-4">
            {/* 角色标题 */}
            <div className="flex items-center justify-between">
              <div>
                <h3 className="text-lg font-black text-slate-900 flex items-center gap-2">
                  <Key size={18} className="text-indigo-600" />
                  {selectedRole.name}
                  {selectedRole.isSystem && (
                    <span className="text-xs font-black text-slate-400 bg-slate-100 px-2 py-0.5 rounded-full uppercase tracking-wider">
                      系统角色
                    </span>
                  )}
                </h3>
                {selectedRole.description && (
                  <p className="text-xs text-slate-500 mt-1">{selectedRole.description}</p>
                )}
              </div>
              <div className="flex items-center gap-2">
                <button
                  onClick={() => {
                    setEditingPermissions(new Set(rolePermissions));
                    setHasChanges(false);
                  }}
                  disabled={!hasChanges}
                  className="px-3 py-2 text-xs font-bold text-slate-500 bg-white border border-slate-200 rounded-lg hover:bg-slate-50 disabled:opacity-30 disabled:cursor-not-allowed transition-colors"
                >
                  重置
                </button>
                <button
                  onClick={savePermissions}
                  disabled={!hasChanges || isSaving || selectedRole.isSystem}
                  className={cn(
                    'px-4 py-2 rounded-lg text-xs font-bold flex items-center gap-1.5 transition-all',
                    hasChanges && !selectedRole.isSystem
                      ? 'bg-indigo-600 text-white hover:bg-indigo-700 shadow-sm'
                      : 'bg-slate-100 text-slate-400 cursor-not-allowed',
                  )}
                >
                  {isSaving ? (
                    <Loader2 size={14} className="animate-spin" />
                  ) : (
                    <Save size={14} />
                  )}
                  保存
                </button>
              </div>
            </div>

            {selectedRole.isSystem && (
              <div className="px-4 py-3 bg-amber-50 border border-amber-200 rounded-xl text-xs text-amber-700 font-medium">
                系统角色的权限不可修改。可以创建自定义角色，然后分配所需权限。
              </div>
            )}

            {/* 权限矩阵 */}
            <div className="space-y-4 max-h-[60vh] overflow-y-auto pr-2 custom-scrollbar">
              {Object.entries(allPermissions).map(([category, perms]) => {
                const allChecked = perms.every(p => editingPermissions.has(p.key));
                const someChecked = perms.some(p => editingPermissions.has(p.key));

                return (
                  <div key={category} className="bg-white border border-slate-100 rounded-2xl overflow-hidden">
                    {/* 分类标题 */}
                    <button
                      onClick={() => toggleCategory(category, perms)}
                      className="w-full flex items-center justify-between px-5 py-3 bg-slate-50/80 hover:bg-slate-100 transition-colors"
                    >
                      <span className="text-xs font-black text-slate-700 uppercase tracking-wider">
                        {category}
                      </span>
                      <span className={cn(
                        'text-xs font-bold px-2 py-0.5 rounded-full',
                        allChecked
                          ? 'bg-indigo-100 text-indigo-600'
                          : someChecked
                            ? 'bg-amber-100 text-amber-600'
                            : 'bg-slate-100 text-slate-400',
                      )}>
                        {perms.filter(p => editingPermissions.has(p.key)).length}/{perms.length}
                      </span>
                    </button>

                    {/* 权限列表 */}
                    <div className="divide-y divide-slate-50">
                      {perms.map(perm => (
                        <label
                          key={perm.key}
                          className={cn(
                            'flex items-center gap-3 px-5 py-2.5 cursor-pointer transition-colors hover:bg-slate-50',
                            !selectedRole.isSystem ? 'cursor-pointer' : 'cursor-not-allowed opacity-60',
                          )}
                        >
                          <div className={cn(
                            'w-5 h-5 rounded-md flex items-center justify-center border-2 transition-all shrink-0',
                            editingPermissions.has(perm.key)
                              ? 'bg-indigo-600 border-indigo-600 text-white'
                              : 'border-slate-300 bg-white',
                            selectedRole.isSystem ? 'opacity-40' : '',
                          )}>
                            {editingPermissions.has(perm.key) && <Check size={14} strokeWidth={3} />}
                          </div>
                          {/* hidden native checkbox for a11y */}
                          <input
                            type="checkbox"
                            checked={editingPermissions.has(perm.key)}
                            onChange={() => togglePermission(perm.key)}
                            disabled={selectedRole.isSystem}
                            className="sr-only"
                          />
                          <div className="flex-1 min-w-0">
                            <div className="text-sm font-bold text-slate-800">{perm.label}</div>
                            <div className="text-xs text-slate-400">{perm.description}</div>
                          </div>
                          <code className="text-xs text-slate-300 font-mono shrink-0">{perm.key}</code>
                        </label>
                      ))}
                    </div>
                  </div>
                );
              })}
            </div>
          </div>
        )}
      </div>
    </div>
  );
};