'use client';

import { useEffect, useState } from 'react';
import Link from 'next/link';
import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
import { Button } from '@/components/ui/button';
import { Tabs, TabsContent, TabsList, TabsTrigger } from '@/components/ui/tabs';
import { StatusBadge } from '@/components/status-badge';
import { useUser } from '@/components/user-context';
import { formatDateRange } from '@/lib/kr-utils';
import type { Task, TaskStep, User } from '@/types/database';
import { CheckSquare, Clock, Calendar, AlertTriangle, User as UserIcon, Plus } from 'lucide-react';
import { TaskEditDialog } from '@/components/task-edit-dialog';
import { toast } from 'sonner';
import { fetchApi } from '@/lib/api-client';

interface TaskWithRelations extends Task {
  steps: TaskStep[];
  owner: User | null;
  // We might want project info too, but the API doesn't return it joined yet.
  // We can fetch projects separately or just show task details.
}

interface HelpStepWithRelations extends TaskStep {
  task: Pick<Task, 'id' | 'title' | 'project_id' | 'kr_id' | 'owner_user_id' | 'help_requested_to_user_id' | 'help_requested_by_user_id' | 'help_requested_at'> | null;
}

export default function MyTasksPage() {
  const { currentUser, users } = useUser();
  const [tasks, setTasks] = useState<TaskWithRelations[]>([]);
  const [helpSteps, setHelpSteps] = useState<HelpStepWithRelations[]>([]);
  const [isLoading, setIsLoading] = useState(true);
  
  // Dialog state
  const [isTaskDialogOpen, setIsTaskDialogOpen] = useState(false);
  const [editingTask, setEditingTask] = useState<(Task & { steps: TaskStep[] }) | null>(null);

  const fetchTasks = async () => {
    try {
      const isOwnerView = currentUser?.role === 'owner';
      const url = isOwnerView
        ? '/api/tasks'
        : `/api/tasks?user_id=${currentUser?.id}&include_help=true`;

      const res = await fetchApi(url);
      if (res.ok) {
        const data = await res.json();
        // Enrich with owner info locally since API doesn't join
        const enrichedData = data.map((t: any) => ({
          ...t,
          owner: users.find(u => u.id === t.owner_user_id) || null
        }));
        setTasks(enrichedData);
      }
    } catch (error) {
      console.error('Failed to fetch tasks:', error);
    } finally {
      setIsLoading(false);
    }
  };

  const fetchHelpSteps = async () => {
    if (!currentUser?.id || currentUser.role === 'owner') return;
    try {
      const res = await fetchApi(`/api/task-steps?help_requested_to_user_id=${currentUser.id}`);
      if (res.ok) {
        const data = await res.json();
        setHelpSteps(data);
      }
    } catch (error) {
      console.error('Failed to fetch help steps:', error);
    }
  };

  useEffect(() => {
    if (users.length > 0 && currentUser) {
      fetchTasks();
      fetchHelpSteps();
    }
  }, [users, currentUser]);

  const handleTaskStatusChange = async (taskId: string, newStatus: string) => {
    try {
      const res = await fetchApi(`/api/tasks/${taskId}`, {
        method: 'PATCH',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ status: newStatus }),
      });
      if (res.ok) {
        setTasks(tasks.map(t => t.id === taskId ? { ...t, status: newStatus as any } : t));
        toast.success('计划状态已更新');
      }
    } catch (error) {
      toast.error('更新失败');
    }
  };

  // Group Tasks by owner for owner view
  const tasksByOwner = users.map(user => ({
    user,
    tasks: tasks.filter(t => t.owner_user_id === user.id && t.status !== 'done')
  })).filter(group => group.tasks.length > 0 || group.user.role !== 'owner')
  .sort((a, b) => {
    if (a.tasks.length > 0 && b.tasks.length === 0) return -1;
    if (a.tasks.length === 0 && b.tasks.length > 0) return 1;
    return 0;
  });

  const myTasks = tasks.filter(t => t.owner_user_id === currentUser?.id);
  const incomingHelpTasks = tasks.filter(t => t.help_requested_to_user_id === currentUser?.id && t.owner_user_id !== currentUser?.id);
  const activeTasks = myTasks.filter(t => t.status !== 'done');
  const completedTasks = myTasks.filter(t => t.status === 'done');
  
  // "Pending" tasks can be defined as todo/in_progress/expected
  const todoTasks = activeTasks.filter(t => t.status === 'todo');
  const inProgressTasks = activeTasks.filter(t => t.status === 'in_progress');

  const isOwner = currentUser?.role === 'owner';

  if (isLoading) {
    return (
      <div className="max-w-5xl mx-auto px-4 py-8">
        <div className="animate-pulse space-y-6">
          <div className="h-8 bg-slate-200 rounded w-32" />
          <div className="space-y-4">
            {[1, 2, 3].map(i => (
              <div key={i} className="h-24 bg-slate-200 rounded-lg" />
            ))}
          </div>
        </div>
      </div>
    );
  }

  return (
    <div className="max-w-5xl mx-auto px-4 py-8">
      <div className="mb-8 flex justify-between items-center">
        <div>
          <h1 className="text-2xl font-bold text-slate-800">
              {isOwner ? '全员计划概览' : '我的计划'}
          </h1>
          <p className="text-muted-foreground mt-1">
            {isOwner 
              ? '查看所有成员的计划执行情况' 
              : `${currentUser?.name} 的计划清单`
            }
          </p>
        </div>
        {!isOwner && (
          <Button onClick={() => {
            setEditingTask(null);
            setIsTaskDialogOpen(true);
          }} className="bg-indigo-600 hover:bg-indigo-700">
            <Plus className="h-4 w-4 mr-2" />
            新建计划
          </Button>
        )}
      </div>

      {isOwner ? (
        <div className="space-y-8">
          {tasksByOwner.map(({ user, tasks }) => (
            <div key={user.id} className="space-y-4">
              <div className="flex items-center gap-3 border-b pb-2">
                <div className="h-8 w-8 rounded-full bg-slate-200 flex items-center justify-center text-sm font-medium text-slate-600">
                    {user.name[0]}
                </div>
                <div>
                    <h2 className="text-lg font-semibold text-slate-800">{user.name}</h2>
                    <p className="text-xs text-muted-foreground">
                        {tasks.length} 个进行中的计划
                    </p>
                </div>
              </div>
              
              {tasks.length === 0 ? (
                <div className="p-8 text-center bg-slate-50 rounded-lg border border-dashed">
                    <p className="text-muted-foreground text-sm">暂无进行中的计划</p>
                </div>
              ) : (
                <div className="grid grid-cols-1 gap-3">
                    {tasks.map(task => (
                      <TaskCard 
                        key={task.id} 
                        task={task} 
                        onStatusChange={handleTaskStatusChange}
                        onClick={() => {
                          setEditingTask(task);
                          setIsTaskDialogOpen(true);
                        }}
                      />
                    ))}
                </div>
              )}
            </div>
          ))}
          
          {tasksByOwner.length === 0 && (
              <div className="text-center py-12">
                  <p className="text-muted-foreground">没有任何成员有正在进行的计划</p>
              </div>
          )}
        </div>
      ) : (
        <>
        <div className="grid grid-cols-3 gap-4 mb-8">
        <Card>
          <CardContent className="pt-6 text-center">
            <CheckSquare className="h-8 w-8 text-slate-300 mx-auto mb-2" />
            <p className="text-3xl font-bold text-slate-800">{activeTasks.length}</p>
            <p className="text-sm text-muted-foreground">待完成</p>
          </CardContent>
        </Card>
        <Card>
          <CardContent className="pt-6 text-center">
            <Clock className="h-8 w-8 text-indigo-300 mx-auto mb-2" />
            <p className="text-3xl font-bold text-indigo-600">{inProgressTasks.length}</p>
            <p className="text-sm text-muted-foreground">进行中</p>
          </CardContent>
        </Card>
        <Card>
          <CardContent className="pt-6 text-center">
            <AlertTriangle className="h-8 w-8 text-rose-300 mx-auto mb-2" />
            <p className="text-3xl font-bold text-rose-600">
              {activeTasks.filter(t => t.priority >= 4).length}
            </p>
            <p className="text-sm text-muted-foreground">高优先级</p>
          </CardContent>
        </Card>
      </div>

      <Tabs defaultValue="active" className="space-y-6">
        <TabsList>
          <TabsTrigger value="active">进行中 ({activeTasks.length})</TabsTrigger>
          <TabsTrigger value="help_plans">协助我的计划 ({incomingHelpTasks.length})</TabsTrigger>
          <TabsTrigger value="help_steps">协助我的步骤 ({helpSteps.length})</TabsTrigger>
          <TabsTrigger value="completed">已完成 ({completedTasks.length})</TabsTrigger>
          <TabsTrigger value="all">全部 ({myTasks.length})</TabsTrigger>
        </TabsList>

        <TabsContent value="active" className="space-y-4">
          {activeTasks.length === 0 ? (
            <Card>
              <CardContent className="py-12 text-center">
                <CheckSquare className="h-12 w-12 text-slate-300 mx-auto mb-4" />
                <p className="text-muted-foreground">暂无进行中的计划</p>
              </CardContent>
            </Card>
          ) : (
            activeTasks.map(task => (
              <TaskCard 
                key={task.id} 
                task={task} 
                onStatusChange={handleTaskStatusChange}
                onClick={() => {
                  setEditingTask(task);
                  setIsTaskDialogOpen(true);
                }}
              />
            ))
          )}
        </TabsContent>

        <TabsContent value="help_plans" className="space-y-4">
          {incomingHelpTasks.length === 0 ? (
            <Card>
              <CardContent className="py-12 text-center">
                <CheckSquare className="h-12 w-12 text-slate-300 mx-auto mb-4" />
                <p className="text-muted-foreground">暂无需要你协助的计划</p>
              </CardContent>
            </Card>
          ) : (
            incomingHelpTasks.map(task => (
              <TaskCard
                key={task.id}
                task={task}
                onStatusChange={handleTaskStatusChange}
                onClick={() => {
                  setEditingTask(task);
                  setIsTaskDialogOpen(true);
                }}
                variant="help"
              />
            ))
          )}
        </TabsContent>

        <TabsContent value="help_steps" className="space-y-4">
          {helpSteps.length === 0 ? (
            <Card>
              <CardContent className="py-12 text-center">
                <CheckSquare className="h-12 w-12 text-slate-300 mx-auto mb-4" />
                <p className="text-muted-foreground">暂无需要你协助的步骤</p>
              </CardContent>
            </Card>
          ) : (
            helpSteps.map(step => (
              <Card
                key={step.id}
                className="border-amber-200 bg-amber-50/40 hover:shadow-md transition-shadow cursor-pointer"
                onClick={() => {
                  if (step.task) {
                    const task = tasks.find(t => t.id === step.task?.id);
                    if (task) {
                      setEditingTask(task);
                      setIsTaskDialogOpen(true);
                    }
                  }
                }}
              >
                <CardContent className="p-4">
                  <div className="flex items-start justify-between gap-4">
                    <div className="min-w-0">
                      <div className="flex items-center gap-2 mb-1">
                        <span className="text-xs bg-amber-100 text-amber-800 px-2 py-0.5 rounded border border-amber-200">
                          协助步骤
                        </span>
                        {step.help_requested_by_user_id && (
                          <span className="text-xs text-muted-foreground">
                            发起人：{users.find(u => u.id === step.help_requested_by_user_id)?.name || '未知'}
                          </span>
                        )}
                      </div>
                      <p className="font-medium text-slate-800 truncate">{step.content}</p>
                      {step.task?.title && (
                        <p className="text-sm text-muted-foreground mt-1 truncate">
                          来自计划：{step.task.title}
                        </p>
                      )}
                      <div className="text-xs text-muted-foreground mt-2 flex items-center gap-2">
                        <Calendar className="h-3 w-3" />
                        {formatDateRange(step.start_date || '', step.end_date || '')}
                      </div>
                    </div>
                    <div className="shrink-0">
                      <StatusBadge status={step.is_completed ? 'green' : 'yellow'} size="sm" text={step.is_completed ? '已完成' : '待协助'} />
                    </div>
                  </div>
                </CardContent>
              </Card>
            ))
          )}
        </TabsContent>

        <TabsContent value="completed" className="space-y-4">
          {completedTasks.length === 0 ? (
            <Card>
              <CardContent className="py-12 text-center">
                <CheckSquare className="h-12 w-12 text-slate-300 mx-auto mb-4" />
                <p className="text-muted-foreground">暂无已完成的计划</p>
              </CardContent>
            </Card>
          ) : (
            completedTasks.map(task => (
              <TaskCard 
                key={task.id} 
                task={task} 
                onStatusChange={handleTaskStatusChange}
                onClick={() => {
                  setEditingTask(task);
                  setIsTaskDialogOpen(true);
                }}
              />
            ))
          )}
        </TabsContent>

        <TabsContent value="all" className="space-y-4">
          {myTasks.length === 0 ? (
            <Card>
              <CardContent className="py-12 text-center">
                <CheckSquare className="h-12 w-12 text-slate-300 mx-auto mb-4" />
                <p className="text-muted-foreground">暂无计划</p>
              </CardContent>
            </Card>
          ) : (
            myTasks.map(task => (
              <TaskCard 
                key={task.id} 
                task={task} 
                onStatusChange={handleTaskStatusChange}
                onClick={() => {
                  setEditingTask(task);
                  setIsTaskDialogOpen(true);
                }}
              />
            ))
          )}
        </TabsContent>
      </Tabs>
      </>
      )}

      <TaskEditDialog 
        open={isTaskDialogOpen} 
        onOpenChange={setIsTaskDialogOpen}
        projectId="" // Global task or we assume user selects project in dialog if we enable it?
        // Wait, TaskEditDialog requires projectId for context. 
        // If we create task from here, it might not belong to a project initially or we need to select one.
        // But the dialog currently assumes projectId is passed for display context "Project: xxx".
        // Let's pass a placeholder or modify dialog to allow selecting project if not provided.
        // For now, let's pass empty string and "个人任务" or similar.
        projectTitle="个人/全局计划"
        task={editingTask}
        onSuccess={fetchTasks}
      />
    </div>
  );
}

function TaskCard({ task, onStatusChange, onClick, variant }: { task: TaskWithRelations; onStatusChange: (id: string, status: string) => void; onClick: () => void; variant?: 'normal' | 'help' }) {
  const { currentUser, users } = useUser();
  const isDone = task.status === 'done';
  const isIncomingHelp = variant === 'help' || (task.help_requested_to_user_id && task.help_requested_to_user_id === currentUser?.id && task.owner_user_id !== currentUser?.id);
  const isOutgoingHelp = task.help_requested_to_user_id && task.owner_user_id === currentUser?.id;
  const requesterName = task.help_requested_by_user_id ? (users.find(u => u.id === task.help_requested_by_user_id)?.name || '未知') : null;
  const helperName = task.help_requested_to_user_id ? (users.find(u => u.id === task.help_requested_to_user_id)?.name || '未知') : null;
  
  return (
    <Card
      className={`hover:shadow-md transition-shadow cursor-pointer ${isDone ? 'opacity-70 bg-slate-50' : ''} ${isIncomingHelp ? 'border-amber-200 bg-amber-50/40' : ''} ${isOutgoingHelp ? 'border-indigo-200 bg-indigo-50/40' : ''}`}
      onClick={onClick}
    >
      <CardContent className="p-4">
        <div className="flex items-start gap-4">
          <div 
            className="mt-1"
            onClick={(e) => {
              e.stopPropagation();
              onStatusChange(task.id, isDone ? 'todo' : 'done');
            }}
          >
            <div className={`w-5 h-5 rounded border flex items-center justify-center transition-colors ${isDone ? 'bg-indigo-600 border-indigo-600' : 'border-slate-300 hover:border-indigo-500'}`}>
              {isDone && <CheckSquare className="h-3.5 w-3.5 text-white" />}
            </div>
          </div>
          
          <div className="flex-1 min-w-0">
            <div className="flex items-center justify-between mb-1">
              <h3 className={`font-medium text-slate-800 truncate ${isDone ? 'line-through text-slate-500' : ''}`}>
                {task.title}
              </h3>
              <StatusBadge 
                status={task.status === 'done' ? 'green' : (task.status === 'in_progress' ? 'yellow' : 'red')} 
                size="sm" 
                text={task.status === 'done' ? '已完成' : (task.status === 'in_progress' ? '进行中' : '待办')} 
              />
            </div>

            {(isIncomingHelp || isOutgoingHelp) && (
              <div className="flex items-center gap-2 mb-2">
                <span className={`text-xs px-2 py-0.5 rounded border ${isIncomingHelp ? 'bg-amber-100 text-amber-800 border-amber-200' : 'bg-indigo-100 text-indigo-800 border-indigo-200'}`}>
                  {isIncomingHelp ? '协助请求' : '已请求协助'}
                </span>
                {isIncomingHelp && requesterName && (
                  <span className="text-xs text-muted-foreground">发起人：{requesterName}</span>
                )}
                {isOutgoingHelp && helperName && (
                  <span className="text-xs text-muted-foreground">协助人：{helperName}</span>
                )}
              </div>
            )}
            
            <div className="flex items-center gap-3 text-sm text-muted-foreground">
              {task.owner && (
                <span className="flex items-center gap-1">
                  <UserIcon className="h-3 w-3" />
                  {task.owner.name}
                </span>
              )}
              <span className="flex items-center gap-1">
                <Calendar className="h-3 w-3" />
                {formatDateRange(task.start_date || '', task.end_date || '')}
              </span>
              {task.steps.length > 0 && (
                <span className="bg-slate-100 px-1.5 rounded text-xs">
                  {task.steps.filter(s => s.is_completed).length}/{task.steps.length} 步骤
                </span>
              )}
            </div>
          </div>
        </div>
      </CardContent>
    </Card>
  );
}