import { useStore } from '@nanostores/react'
import { useEffect, useState } from 'react'

import { BrandMark } from '@/components/brand-mark'
import { Button } from '@/components/ui/button'
import { writeClipboardText } from '@/components/ui/copy-button'
import { Dialog, DialogContent, DialogDescription, DialogTitle } from '@/components/ui/dialog'
import { ErrorIcon, ErrorState } from '@/components/ui/error-state'
import { Loader } from '@/components/ui/loader'
import type { DesktopUpdateCommit, DesktopUpdateStage, DesktopUpdateStatus } from '@/global'
import { useI18n } from '@/i18n'
import { buildCommitChangelog, type CommitGroup } from '@/lib/commit-changelog'
import { AlertCircle, Check, CheckCircle2, Copy, Terminal } from '@/lib/icons'
import { cn } from '@/lib/utils'
import { resolveUpdateCopy, type UpdateTarget } from '@/lib/update-copy'
import {
  $backendUpdateApply,
  $backendUpdateChecking,
  $backendUpdateStatus,
  $updateApply,
  $updateChecking,
  $updateOverlayOpen,
  $updateOverlayTarget,
  $updateStatus,
  applyBackendUpdate,
  applyUpdates,
  checkBackendUpdates,
  checkUpdates,
  resetUpdateApplyState,
  setUpdateOverlayOpen,
  type UpdateApplyState
} from '@/store/updates'

function totalItems(groups: readonly CommitGroup[]) {
  return groups.reduce((sum, g) => sum + g.items.length, 0)
}

export function UpdatesOverlay() {
  const open = useStore($updateOverlayOpen)
  const target = useStore($updateOverlayTarget)

  const clientStatus = useStore($updateStatus)
  const clientChecking = useStore($updateChecking)
  const clientApply = useStore($updateApply)
  const backendStatus = useStore($backendUpdateStatus)
  const backendChecking = useStore($backendUpdateChecking)
  const backendApply = useStore($backendUpdateApply)

  const isBackend = target === 'backend'
  const status = isBackend ? backendStatus : clientStatus
  const checking = isBackend ? backendChecking : clientChecking
  const apply = isBackend ? backendApply : clientApply
  const check = isBackend ? checkBackendUpdates : checkUpdates
  const install = isBackend ? applyBackendUpdate : applyUpdates

  useEffect(() => {
    if (open && !status && !checking) {
      void check()
    }
  }, [check, checking, open, status])

  const behind = status?.behind ?? 0

  const phase: 'idle' | 'applying' | 'manual' | 'error' =
    apply.stage === 'manual'
      ? 'manual'
      : apply.applying || apply.stage === 'restart'
        ? 'applying'
        : apply.stage === 'error'
          ? 'error'
          : 'idle'

  const handleClose = (next: boolean) => {
    if (phase === 'applying') {
      return
    }

    setUpdateOverlayOpen(next)

    if (!next && (apply.stage === 'error' || apply.stage === 'restart' || apply.stage === 'manual')) {
      resetUpdateApplyState()
    }
  }

  const handleInstall = () => {
    void install()
  }

  return (
    <Dialog onOpenChange={handleClose} open={open}>
      <DialogContent
        className="max-w-sm overflow-hidden border-border/70 p-0 gap-0"
        showCloseButton={phase !== 'applying'}
      >
        {phase === 'applying' && <ApplyingView apply={apply} isBackend={isBackend} />}

        {phase === 'manual' && (
          <ManualView command={apply.command ?? 'hermes update'} onDone={() => handleClose(false)} />
        )}

        {phase === 'error' && (
          <ErrorView message={apply.message} onDismiss={() => handleClose(false)} onRetry={handleInstall} />
        )}

        {phase === 'idle' && (
          <IdleView
            behind={behind}
            checking={checking}
            commits={status?.commits ?? []}
            onInstall={handleInstall}
            onLater={() => handleClose(false)}
            onRetryCheck={() => void check()}
            status={status}
            target={target}
          />
        )}
      </DialogContent>
    </Dialog>
  )
}

function IdleView({
  behind,
  checking,
  commits,
  onInstall,
  onLater,
  onRetryCheck,
  status,
  target
}: {
  behind: number
  checking: boolean
  commits: readonly DesktopUpdateCommit[]
  onInstall: () => void
  onLater: () => void
  onRetryCheck: () => void
  status: DesktopUpdateStatus | null
  target: UpdateTarget
}) {
  const { t } = useI18n()
  const u = t.updates

  if (!status && checking) {
    return (
      <CenteredStatus icon={<Loader className="size-12" label={u.checking} type="lemniscate-bloom" />} title={u.checking} />
    )
  }

  if (!status) {
    return (
      <CenteredStatus
        action={
          <Button onClick={onRetryCheck} size="sm">
            {u.tryAgain}
          </Button>
        }
        icon={<ErrorIcon />}
        title={u.checkFailedTitle}
      />
    )
  }

  if (!status.supported) {
    return (
      <CenteredStatus
        body={status.message ?? u.unsupportedMessage}
        icon={<AlertCircle className="size-6 text-muted-foreground" />}
        title={u.notAvailableTitle}
      />
    )
  }

  if (status.error) {
    return (
      <CenteredStatus
        action={
          <Button disabled={checking} onClick={onRetryCheck} size="sm">
            {u.tryAgain}
          </Button>
        }
        body={u.connectionRetry}
        icon={<ErrorIcon />}
        title={u.checkFailedTitle}
      />
    )
  }

  if (behind === 0) {
    return (
      <CenteredStatus
        body={target === 'backend' ? u.latestBodyBackend : u.latestBody}
        icon={<CheckCircle2 className="size-7 text-emerald-600 dark:text-emerald-400" />}
        title={u.allSetTitle}
      />
    )
  }

  const groups = buildCommitChangelog(commits)
  const shownItems = totalItems(groups)
  const remaining = Math.max(0, behind - shownItems)

  // Name what's being updated. In remote mode the overlay acts on the connected
  // backend, not the local client — say so. When there are no commit rows to
  // show (e.g. pip/non-git backend), degrade to honest "no release notes" copy
  // instead of generic filler.
  const { title, body } = resolveUpdateCopy({ target, shownItems, copy: u })

  return (
    <div className="grid gap-5 px-6 pb-6 pt-7 pr-8">
      <div className="flex flex-col items-center gap-3 text-center">
        <BrandMark className="size-16" />

        <DialogTitle className="text-center text-xl">{title}</DialogTitle>
        <DialogDescription className="text-center text-sm">
          {body}
        </DialogDescription>
      </div>

      <div className="grid gap-3 rounded-xl border border-border/70 bg-muted/20 px-4 py-3">
        {groups.map(group => (
          <div key={group.id}>
            <p className="text-[0.625rem] font-semibold uppercase tracking-wide text-muted-foreground">{group.label}</p>
            <ul className="mt-1.5 grid gap-1.5 text-xs text-foreground">
              {group.items.map(item => (
                <li className="flex items-start gap-2" key={item}>
                  <span aria-hidden className="mt-1.5 inline-block size-1 shrink-0 rounded-full bg-primary" />
                  <span className="leading-snug">{item}</span>
                </li>
              ))}
            </ul>
          </div>
        ))}
      </div>

      <div className="grid gap-2">
        <Button className="font-semibold" onClick={onInstall} size="lg">
          {u.updateNow}
        </Button>
        <Button className="font-medium" onClick={onLater} type="button" variant="text">
          {u.maybeLater}
        </Button>
      </div>

      {remaining > 0 && (
        <p className="text-center text-xs text-muted-foreground">
          {u.moreChanges(remaining)}
        </p>
      )}
    </div>
  )
}

function ManualView({ command, onDone }: { command: string; onDone: () => void }) {
  const { t } = useI18n()
  const u = t.updates
  const [copied, setCopied] = useState(false)

  const handleCopy = () => {
    void writeClipboardText(command).then(() => {
      setCopied(true)
      window.setTimeout(() => setCopied(false), 1800)
    })
  }

  return (
    <div className="grid gap-5 px-6 pb-6 pt-7 pr-8">
      <div className="flex flex-col items-center gap-3 text-center">
        <Terminal className="size-8 text-primary" />

        <DialogTitle className="text-center text-xl">{u.manualTitle}</DialogTitle>
        <DialogDescription className="text-center text-sm">
          {u.manualBody}
        </DialogDescription>
      </div>

      <button
        className="group flex w-full items-center justify-between gap-3 rounded-xl border border-border/70 bg-muted/30 px-4 py-3 text-left transition-colors hover:border-border hover:bg-muted/50"
        onClick={handleCopy}
        type="button"
      >
        <code className="select-all font-mono text-sm text-foreground">
          <span className="text-muted-foreground">$ </span>
          {command}
        </code>
        <span className="flex shrink-0 items-center gap-1 text-xs font-medium text-muted-foreground transition-colors group-hover:text-foreground">
          {copied ? (
            <>
              <Check className="size-3.5 text-emerald-600 dark:text-emerald-400" />
              {u.copied}
            </>
          ) : (
            <>
              <Copy className="size-3.5" />
              {u.copy}
            </>
          )}
        </span>
      </button>

      <p className="text-center text-xs text-muted-foreground">
        {u.manualPickedUp}
      </p>

      <Button className="font-semibold" onClick={onDone} size="lg" variant="secondary">
        {u.done}
      </Button>
    </div>
  )
}

function ApplyingView({ apply, isBackend }: { apply: UpdateApplyState; isBackend: boolean }) {
  const { t } = useI18n()
  const u = t.updates
  const label = u.stages[apply.stage as DesktopUpdateStage] ?? u.stages.idle
  const body = isBackend ? u.applyingBodyBackend : u.applyingBody

  const percent =
    typeof apply.percent === 'number' && Number.isFinite(apply.percent)
      ? Math.max(2, Math.min(100, Math.round(apply.percent)))
      : null

  return (
    <div className="grid gap-5 px-6 pb-6 pt-7">
      <div className="flex flex-col items-center gap-3 text-center">
        <Loader className="size-16" label={label} type="lemniscate-bloom" />

        <DialogTitle className="text-center text-xl">{label}</DialogTitle>
        <DialogDescription className="text-center text-sm">
          {body}
        </DialogDescription>
      </div>

      <div className="h-2 overflow-hidden rounded-full bg-muted">
        <div
          className={cn(
            'h-full rounded-full bg-primary transition-[width] duration-300 ease-out',
            percent === null && 'w-1/3 animate-pulse'
          )}
          style={percent !== null ? { width: `${percent}%` } : undefined}
        />
      </div>

      <p className="text-center text-xs text-muted-foreground">{u.applyingClose}</p>
    </div>
  )
}

function ErrorView({ message, onDismiss, onRetry }: { message: string; onDismiss: () => void; onRetry: () => void }) {
  const { t } = useI18n()
  const u = t.updates

  return (
    <ErrorState
      className="px-6 pb-6 pt-7 pr-8"
      description={
        <DialogDescription className="max-w-prose text-center text-sm leading-5 text-muted-foreground">
          {message || u.errorBody}
        </DialogDescription>
      }
      title={
        <DialogTitle className="text-center text-xl font-semibold tracking-tight">{u.errorTitle}</DialogTitle>
      }
    >
      <Button className="font-semibold" onClick={onRetry} size="lg">
        {u.tryAgain}
      </Button>
      <Button onClick={onDismiss} variant="text">
        {u.notNow}
      </Button>
    </ErrorState>
  )
}

function CenteredStatus({
  action,
  body,
  icon,
  title
}: {
  action?: React.ReactNode
  body?: string
  icon: React.ReactNode
  title: string
}) {
  return (
    <div className="grid gap-4 px-6 pb-6 pt-8 pr-8">
      <div className="flex flex-col items-center gap-3 text-center">
        {icon}

        <DialogTitle className="text-center text-lg">{title}</DialogTitle>
        {body && <DialogDescription className="text-center text-sm">{body}</DialogDescription>}
      </div>

      {action && <div className="flex justify-center">{action}</div>}
    </div>
  )
}
