import { useEffect, useMemo, useState } from 'react'
import { NavLink } from 'react-router-dom'
import { listActionTasks } from '../api/tasks.js'
import { actionPath } from '../utils/routes.js'
import { buildTasksByParent, countOpenTasks, MAX_TASK_UI_DEPTH } from '../utils/taskTree.js'
import { getActionExecutionMeta } from '../utils/executionGraph.js'
import { ExecutionFlowBadge } from './ExecutionFlowBadge.jsx'

function actionTasksHref(actionId) {
  return `${actionPath(actionId)}#tasks`
}

function PlanOutlineTaskTree({
  tasksByParent,
  parentId,
  actionId,
  depth,
  expandedTaskIds,
  onToggleTask,
  activeActionId,
}) {
  const nodes = (tasksByParent.get(parentId || '') || []).filter(
    (task) => task.status !== 'done' && task.status !== 'discarded',
  )

  if (nodes.length === 0 || depth > MAX_TASK_UI_DEPTH) {
    return null
  }

  return (
    <ul className="analysis-split__nav-sublist">
      {nodes.map((task) => {
        const childNodes = tasksByParent.get(task.id) || []
        const hasChildren = childNodes.some(
          (child) => child.status !== 'done' && child.status !== 'discarded',
        )
        const canExpand = hasChildren && depth < MAX_TASK_UI_DEPTH
        const isExpanded = expandedTaskIds.has(task.id)

        return (
          <li key={task.id}>
            <div className="analysis-split__nav-row">
              {canExpand && (
                <button
                  type="button"
                  className="analysis-split__nav-toggle"
                  aria-expanded={isExpanded}
                  aria-label={isExpanded ? 'Aufgaben einklappen' : 'Aufgaben ausklappen'}
                  onClick={() => onToggleTask(task.id)}
                >
                  {isExpanded ? '▾' : '▸'}
                </button>
              )}
              <NavLink
                to={actionTasksHref(actionId)}
                className={({ isActive }) =>
                  'analysis-split__nav-link analysis-split__nav-link--nested' +
                  (depth >= 2 ? ' analysis-split__nav-link--depth-2' : '') +
                  (isActive || activeActionId === actionId
                    ? ' analysis-split__nav-link--active'
                    : '')
                }
              >
                {task.title}
              </NavLink>
            </div>
            {canExpand && isExpanded && (
              <PlanOutlineTaskTree
                tasksByParent={tasksByParent}
                parentId={task.id}
                actionId={actionId}
                depth={depth + 1}
                expandedTaskIds={expandedTaskIds}
                onToggleTask={onToggleTask}
                activeActionId={activeActionId}
              />
            )}
          </li>
        )
      })}
    </ul>
  )
}

function PlanOutlineActionNode({ action, tasks, activeActionId, defaultExpanded, executionGraph }) {
  const [actionOpen, setActionOpen] = useState(defaultExpanded)
  const [expandedTaskIds, setExpandedTaskIds] = useState(() => new Set())

  const tasksByParent = useMemo(() => buildTasksByParent(tasks || []), [tasks])
  const openTaskCount = useMemo(() => countOpenTasks(tasks || []), [tasks])
  const hasOpenTasks = openTaskCount > 0

  useEffect(() => {
    setActionOpen(defaultExpanded)
  }, [defaultExpanded])

  function toggleTask(taskId) {
    setExpandedTaskIds((prev) => {
      const next = new Set(prev)
      if (next.has(taskId)) next.delete(taskId)
      else next.add(taskId)
      return next
    })
  }

  const execMeta = getActionExecutionMeta(executionGraph, action.id)

  return (
    <li>
      <div className="analysis-split__nav-row">
        {hasOpenTasks && (
          <button
            type="button"
            className="analysis-split__nav-toggle"
            aria-expanded={actionOpen}
            aria-label={actionOpen ? 'Aufgaben einklappen' : 'Aufgaben ausklappen'}
            onClick={() => setActionOpen((open) => !open)}
          >
            {actionOpen ? '▾' : '▸'}
          </button>
        )}
        <NavLink
          to={actionPath(action.id)}
          className={({ isActive }) =>
            'analysis-split__nav-link analysis-split__nav-link--nested' +
            (isActive || activeActionId === action.id
              ? ' analysis-split__nav-link--active'
              : '')
          }
        >
          {action.title}
          {openTaskCount > 0 && (
            <span className="analysis-split__nav-meta"> ({openTaskCount})</span>
          )}
        </NavLink>
        <ExecutionFlowBadge meta={execMeta} actionStatus={action.status} />
      </div>
      {hasOpenTasks && actionOpen && (
        <PlanOutlineTaskTree
          tasksByParent={tasksByParent}
          parentId=""
          actionId={action.id}
          depth={1}
          expandedTaskIds={expandedTaskIds}
          onToggleTask={toggleTask}
          activeActionId={activeActionId}
        />
      )}
    </li>
  )
}

export function PlanOutlineWorkTree({ openActions, activeActionId, enabled, executionGraph = null }) {
  const [tasksByAction, setTasksByAction] = useState({})
  const actionIdsKey = useMemo(
    () => openActions.map((action) => action.id).join(','),
    [openActions],
  )

  useEffect(() => {
    if (!enabled || openActions.length === 0) {
      setTasksByAction({})
      return undefined
    }
    let cancelled = false
    Promise.all(
      openActions.map((action) =>
        listActionTasks(action.id)
          .then((tasks) => [action.id, Array.isArray(tasks) ? tasks : []])
          .catch(() => [action.id, []]),
      ),
    ).then((entries) => {
      if (!cancelled) setTasksByAction(Object.fromEntries(entries))
    })
    return () => {
      cancelled = true
    }
  }, [enabled, actionIdsKey, openActions])

  return (
    <ul className="analysis-split__nav-sublist">
      {openActions.map((action) => (
        <PlanOutlineActionNode
          key={action.id}
          action={action}
          tasks={tasksByAction[action.id] || []}
          activeActionId={activeActionId}
          defaultExpanded={activeActionId === action.id}
          executionGraph={executionGraph}
        />
      ))}
    </ul>
  )
}