import { useMemo, useState } from 'react'
import { Link } from 'react-router-dom'
import { useQuery } from '@tanstack/react-query'
import { api } from '../api/client'
import type { Overview, Task } from '../api/types'
import { Chip, Empty, EndpointGap, M, PHASES, PhasePath } from '../components/Primitives'
import { Icon } from '../components/Icon'
import './Tasks.css'

type GroupKey = 'attention' | 'running' | 'waiting' | 'completed' | 'failed'

const GROUPS: { key: GroupKey; title: string; icon: string; open: boolean }[] = [
  { key: 'attention', title: 'Needs attention', icon: 'alert', open: true },
  { key: 'running', title: 'Running', icon: 'play', open: true },
  { key: 'waiting', title: 'Waiting / queued', icon: 'queue', open: true },
  { key: 'completed', title: 'Completed', icon: 'check', open: false },
  { key: 'failed', title: 'Failed', icon: 'x', open: false },
]

function groupOf(task: Task): GroupKey {
  switch (task.state) {
    case 'needs_attention':
    case 'blocked':
      return 'attention'
    case 'leased':
      return 'running'
    case 'completed':
      return 'completed'
    case 'failed':
      return 'failed'
    default:
      return 'waiting'
  }
}

/** The harness holding the lease, or the last one that did. Nothing is
 *  invented: a task that never ran reports no worker. */
function harnessOf(task: Task) {
  return task.lease?.harness_id || task.last_harness_id || ''
}

function stateTone(task: Task) {
  if (task.state === 'failed' || task.state === 'blocked') return 'fault' as const
  if (task.state === 'needs_attention') return 'warn' as const
  if (task.state === 'completed') return 'done' as const
  if (task.state === 'leased') return 'accent' as const
  return undefined
}

function ago(at?: string) {
  if (!at) return ''
  const ms = Date.now() - Date.parse(at)
  if (!Number.isFinite(ms)) return ''
  return `${span(ms)} ago`
}

function span(ms: number) {
  const s = Math.max(0, Math.round(ms / 1000))
  if (s < 60) return `${s}s`
  if (s < 3600) return `${Math.round(s / 60)}m`
  if (s < 86400) return `${Math.round(s / 3600)}h`
  return `${Math.round(s / 86400)}d`
}

/** The one time value a task actually carries per state. There is no
 *  per-task updated_at on the overview, so this never claims one. */
function timing(task: Task): { label: string; value: string } | undefined {
  if (task.lease?.until) {
    const left = Date.parse(task.lease.until) - Date.now()
    return left > 0
      ? { label: 'lease', value: `${span(left)} left` }
      : { label: 'lease', value: `expired ${span(-left)} ago` }
  }
  if (task.blocked_at) return { label: 'blocked', value: ago(task.blocked_at) }
  if (task.next_retry_at) {
    const left = Date.parse(task.next_retry_at) - Date.now()
    return { label: 'retry', value: left > 0 ? `in ${span(left)}` : 'due' }
  }
  if (task.due) return { label: 'due', value: task.due.slice(0, 10) }
  return undefined
}

function unique(values: (string | undefined)[]) {
  return [...new Set(values.filter((value): value is string => !!value))].sort()
}

function Select({
  label,
  value,
  options,
  onChange,
}: {
  label: string
  value: string
  options: string[]
  onChange: (next: string) => void
}) {
  return (
    <label className="tasks-filter">
      <span className="label">{label}</span>
      <select value={value} onChange={(event) => onChange(event.target.value)}>
        <option value="">any</option>
        {options.map((option) => (
          <option key={option} value={option}>
            {option}
          </option>
        ))}
      </select>
    </label>
  )
}

function Row({ task, agentStatus }: { task: Task; agentStatus?: string }) {
  const harness = harnessOf(task)
  const when = timing(task)
  return (
    <Link className="row task-row" to={`/tasks/${task.id}`}>
      <span className="task-row-main">
        <span className="row-title">{task.title || task.external_id || 'untitled task'}</span>
        <span className="row-sub">
          {task.project} · <M>{task.external_id || task.id}</M>
        </span>
      </span>

      <span className="task-row-phase tasks-phases">
        <PhasePath current={task.lifecycle_phase} labels={false} />
        <span className="task-row-phase-name mono">{task.lifecycle_phase || '—'}</span>
      </span>

      <span className="task-row-worker">
        {harness ? (
          <>
            <M>{harness}</M>
            {task.last_pane_id && <span className="row-sub mono">{task.last_pane_id}</span>}
          </>
        ) : (
          <span className="row-sub">unassigned</span>
        )}
      </span>

      <span className="task-row-when">
        {when && (
          <>
            <span className="label">{when.label}</span>
            <M>{when.value}</M>
          </>
        )}
      </span>

      <span className="task-row-status">
        {agentStatus && <Chip>{agentStatus}</Chip>}
        <Chip tone={stateTone(task)}>{task.block_reason || task.state}</Chip>
      </span>

      <Icon name="chevron-right" size={16} />
    </Link>
  )
}

function Group({
  title,
  icon,
  open,
  tasks,
  statusFor,
}: {
  title: string
  icon: string
  open: boolean
  tasks: Task[]
  statusFor: (task: Task) => string | undefined
}) {
  return (
    <details className="panel tasks-group" open={open && tasks.length > 0}>
      <summary className="panel-head">
        <Icon name={icon} size={17} />
        <h2>{title}</h2>
        <span className="count">{tasks.length}</span>
        <Icon name="chevron-right" size={16} />
      </summary>
      {tasks.length ? (
        <div className="rows">
          {tasks.map((task) => (
            <Row key={task.id} task={task} agentStatus={statusFor(task)} />
          ))}
        </div>
      ) : (
        <Empty title="Nothing here" />
      )}
    </details>
  )
}

export function Tasks() {
  const { data, isLoading, error } = useQuery<Overview>({
    queryKey: ['overview'],
    queryFn: api.overview,
    refetchInterval: 5000,
  })

  const [project, setProject] = useState('')
  const [phase, setPhase] = useState('')
  const [worker, setWorker] = useState('')
  const [attention, setAttention] = useState('')
  const [group, setGroup] = useState<GroupKey | ''>('')

  const tasks = useMemo(() => data?.tasks ?? [], [data])

  /** Agent status comes from the live session, matched by pane. It is an
   *  agent claim, so it stays a separate chip from orchestra's own state. */
  const statusFor = useMemo(() => {
    const byPane = new Map((data?.sessions ?? []).map((s) => [s.pane_id, s]))
    return (task: Task) =>
      task.state === 'leased' ? byPane.get(task.last_pane_id)?.agent_status : undefined
  }, [data])

  const filtered = tasks.filter((task) => {
    if (project && task.project !== project) return false
    if (phase && task.lifecycle_phase !== phase) return false
    if (worker && harnessOf(task) !== worker) return false
    if (attention === 'needs' && groupOf(task) !== 'attention') return false
    if (attention === 'clear' && groupOf(task) === 'attention') return false
    if (attention && attention !== 'needs' && attention !== 'clear' && task.block_reason !== attention)
      return false
    return true
  })

  const counts = (key: GroupKey) => filtered.filter((task) => groupOf(task) === key).length
  const shown = GROUPS.filter((g) => !group || g.key === group)

  return (
    <main className="page">
      <div className="page-head">
        <h1>Tasks</h1>
        <p>All work under orchestration.</p>
        <span className="count mono">{tasks.length}</span>
      </div>

      <div className="tasks-controls">
        <div className="tasks-tabs" role="tablist">
          <button
            type="button"
            role="tab"
            aria-selected={group === ''}
            className="tasks-tab"
            onClick={() => setGroup('')}
          >
            All <span className="mono">{filtered.length}</span>
          </button>
          {GROUPS.map((g) => (
            <button
              key={g.key}
              type="button"
              role="tab"
              aria-selected={group === g.key}
              className="tasks-tab"
              onClick={() => setGroup(group === g.key ? '' : g.key)}
            >
              {g.title} <span className="mono">{counts(g.key)}</span>
            </button>
          ))}
        </div>
        <div className="tasks-filters">
          <Select
            label="Project"
            value={project}
            options={unique(tasks.map((task) => task.project))}
            onChange={setProject}
          />
          <Select label="Phase" value={phase} options={[...PHASES]} onChange={setPhase} />
          <Select
            label="Worker"
            value={worker}
            options={unique(tasks.map(harnessOf))}
            onChange={setWorker}
          />
          <Select
            label="Attention"
            value={attention}
            options={['needs', 'clear', ...unique(tasks.map((task) => task.block_reason))]}
            onChange={setAttention}
          />
        </div>
      </div>

      {error && (
        <div className="panel panel-body">
          <p className="gap-note">/v1/ui/overview failed: {(error as Error).message}</p>
        </div>
      )}

      {isLoading && !data && (
        <div className="panel panel-body">
          <p className="gap-note">loading /v1/ui/overview…</p>
        </div>
      )}

      {data && !tasks.length && (
        <div className="panel">
          <Empty title="No tasks yet">
            <p>Orchestra has no work on record. Ingest a task to start.</p>
          </Empty>
        </div>
      )}

      {data &&
        tasks.length > 0 &&
        shown.map((g) => (
          <Group
            key={g.key}
            title={g.title}
            icon={g.icon}
            open={g.open || !!group}
            tasks={filtered.filter((task) => groupOf(task) === g.key)}
            statusFor={statusFor}
          />
        ))}

      {data && tasks.length > 0 && (
        <div className="panel">
          <EndpointGap
            path="/v1/ui/overview carries no per-task progress, ETA or context occupancy"
            what="Rows show lease, block and retry times because those are the only per-task clocks orchestra records. Progress bars and context meters are left out rather than estimated."
          />
        </div>
      )}
    </main>
  )
}