/**
 * The controlled file tree behind the files window's tree panel (TreePanel
 * wraps it with the search box): a lazy VSCode-style tree rooted at the
 * session's working directory. Levels load on expansion (one API call per
 * directory), directories sort first, hidden entries render dimmed. The
 * expansion set lives in the per-session state (owned by the caller); the
 * caller also owns the refresh affordance — a `refreshTick` bump wipes the
 * level cache so the visible set reloads.
 *
 * Row actions: hovering a row reveals an @-reference button on the far
 * right (appends `@<relative path>` to the composer draft), and right-click
 * opens a context menu: file rows offer the caller's open escapes
 * (new tab / to the side, only when the callbacks exist) and a download
 * action (the host serves raw bytes, binary-safe); directory rows offer
 * "upload here"; every row can copy the relative or absolute path (with a
 * brief "copied" label replacing the button after a successful write).
 *
 * Uploads start here (drag-drop or the context menu picker) but run in the
 * caller: every request is reported through `onUploadRequest(dir, items)`
 * (VSCode semantics — a drop on a file row targets its parent directory),
 * and `busy` gates new drags while one upload is in flight.
 */
import { useCallback, useEffect, useRef, useState, type DragEvent, type MouseEvent, type ReactNode } from 'react'
import { createPortal } from 'react-dom'
import clsx from 'clsx'
import {
  IconCodeOutline16, IconCopyOutline16, IconDownloadOutline16, IconFolderClose16, IconFolderOpen16,
  IconLinkOutline16, Menu, writeClipboard,
} from '@deepseek-ai/dsh-client-ui-primitives'
import { api, downloadUrl, type FsEntry } from './api.ts'
import { IconUploadOutline16 } from './icons.tsx'
import { relativeTo } from './paths.ts'
import { t } from './locales.ts'
import { uploadItemsFromDrop, uploadItemsFromFiles, type UploadItem } from './upload.ts'
import css from './sidebar.module.css'

interface LevelData {
  entries?: FsEntry[]
  error?: string
}

/** Root label: the last path segment (mirror of the host rootLabel). */
export function baseName(path: string): string {
  const trimmed = path.replace(/[\\/]+$/, '')
  const at = Math.max(trimmed.lastIndexOf('/'), trimmed.lastIndexOf('\\'))
  return at === -1 ? trimmed : trimmed.slice(at + 1)
}

/** The containing directory of an absolute row path (never the root edge here). */
function parentOf(path: string): string {
  const at = Math.max(path.lastIndexOf('/'), path.lastIndexOf('\\'))
  return at <= 0 ? path : path.slice(0, at)
}

/** How long the row's "copied" label stays after a successful write. */
const COPIED_MS = 1200

/**
 * The drop overlay's hero art: an arrow descending into a tray (upload
 * zone) and tilted photo cards (chat zone). Hand-drawn, colored in the
 * palette of DSH's own native drop illustration (#3964FE / #679EFE /
 * #9CE5ED) so the two zones read as one family; the drop overlay is this
 * flow's one brand moment, so it gets color the rest of the UI never does.
 */
const UploadDropIllustration = () => (
  <svg width="64" height="56" viewBox="0 0 64 56" fill="none" aria-hidden="true">
    <path d="M8 36h48v6a10 10 0 0 1-10 10H18A10 10 0 0 1 8 42v-6z" fill="#9CE5ED" />
    <path d="M32 4v26" stroke="#3964FE" strokeWidth="5" strokeLinecap="round" />
    <path d="M19 21l13 13 13-13" stroke="#3964FE" strokeWidth="5" strokeLinecap="round" strokeLinejoin="round" />
  </svg>
)

/** The chat zone's art: a tilted pair of photo cards (sun over mountains). */
const ChatDropIllustration = () => (
  <svg width="92" height="72" viewBox="0 0 92 72" fill="none" aria-hidden="true">
    <rect x="8" y="14" width="34" height="34" rx="9" transform="rotate(-14 8 14)" fill="#9CE5ED" />
    <g transform="rotate(10 42 10)">
      <rect x="42" y="10" width="38" height="42" rx="9" fill="#3964FE" />
      <circle cx="56" cy="24" r="4.5" fill="white" />
      <path d="M47 44l9-11 7 8 5-5 8 10" stroke="white" strokeWidth="3" strokeLinecap="round" strokeLinejoin="round" />
    </g>
  </svg>
)

export function FileTree(props: {
  sessionId: string
  cwd: string | undefined
  expanded: string[]
  onToggle: (path: string) => void
  onOpenFile: (path: string) => void
  /** Context-menu "open in a new tab" (file rows; absent → no entry). */
  onOpenFileNewTab?: (path: string) => void
  /** Context-menu "open to the side" (file rows; absent → no entry). */
  onOpenFileSide?: (path: string) => void
  /** Insert `@<relative path>` into the composer draft. */
  onReferenceFile: (path: string) => void
  /** Bump to wipe the level cache and reload the visible set. */
  refreshTick: number
  /** Upload into `dir` (absolute, inside the workspace); runs in the caller. */
  onUploadRequest: (dir: string, items: UploadItem[]) => void
  /** True while an upload is in flight (drops are ignored). */
  busy: boolean
}) {
  const { sessionId, cwd, expanded, onToggle, onOpenFile, onOpenFileNewTab, onOpenFileSide, onReferenceFile, refreshTick, onUploadRequest, busy } = props
  const [data, setData] = useState<Record<string, LevelData>>({})
  const dataRef = useRef(data)
  /** The row whose path was just copied ("copied" label replaces its button). */
  const [copiedPath, setCopiedPath] = useState<string | null>(null)
  /** Open context menu: the row path (and whether it is a directory) plus the cursor position. */
  const [rowMenu, setRowMenu] = useState<{ path: string; isDir: boolean; x: number; y: number } | null>(null)
  /** Whether a file drag hovers the tree (drives the portaled drop zone). */
  const [dropOver, setDropOver] = useState(false)
  /** The directory a drag is hovering right now (null = body, drop to root). */
  const [dropTarget, setDropTarget] = useState<string | null>(null)
  /**
   * Enter/leave depth under the tree body. dragenter/dragleave fire per
   * element along the drag path (and bubble), so a counter — DSH InputBar's
   * own pattern — is the flicker-free signal; relatedTarget is unreliable
   * across engines for drag events.
   */
  const dropDepth = useRef(0)
  /** Explorer body element; its viewport rect anchors the portaled drop zone. */
  const bodyRef = useRef<HTMLDivElement>(null)
  /** The body's viewport rect captured at drag entry (null = not measured). */
  const [dropRect, setDropRect] = useState<{ top: number; left: number; width: number; height: number } | null>(null)
  /** Context-menu "upload here" target directory. */
  const pendingUploadDir = useRef<string | undefined>(undefined)
  const fileInputRef = useRef<HTMLInputElement>(null)

  /** Reset all drag state (drop landed, the drag left, or a new drag begins). */
  const resetDrop = (): void => {
    dropDepth.current = 0
    setDropOver(false)
    setDropTarget(null)
    setDropRect(null)
  }

  /**
   * Drop handlers: always swallow the event (a dropped file must never open
   * in the browser), then report the target directory to the caller. A drop
   * ends the drag without further leave events, so the depth resets here.
   * The payload collection is async (dropped folders are traversed through
   * their entry handles — captured synchronously inside uploadItemsFromDrop
   * while the dataTransfer is still live), so the request rides a then.
   */
  const reportDrop = (dir: string, data: DataTransfer | undefined): void => {
    if (busy) return
    void uploadItemsFromDrop(data).then((items) => {
      if (items.length > 0) onUploadRequest(dir, items)
    })
  }
  const handleBodyDrop = (event: DragEvent): void => {
    event.preventDefault()
    event.stopPropagation()
    resetDrop()
    if (cwd !== undefined) reportDrop(cwd, event.dataTransfer)
  }
  const handleDirDrop = (event: DragEvent, dir: string): void => {
    event.preventDefault()
    event.stopPropagation()
    resetDrop()
    reportDrop(dir, event.dataTransfer)
  }
  const handleFileDrop = (event: DragEvent, path: string): void => {
    // VSCode semantics: dropping onto a file uploads into its directory.
    handleDirDrop(event, parentOf(path))
  }
  const handleBodyDragEnter = (event: DragEvent): void => {
    event.preventDefault()
    event.stopPropagation()
    dropDepth.current += 1
    if (busy) return
    // First entry: anchor the portaled drop zone to the body's rect.
    if (dropDepth.current === 1) {
      const rect = bodyRef.current?.getBoundingClientRect()
      setDropRect(rect === undefined ? null : { top: rect.top, left: rect.left, width: rect.width, height: rect.height })
    }
    setDropOver(true)
  }
  const handleBodyDragLeave = (): void => {
    dropDepth.current = Math.max(0, dropDepth.current - 1)
    if (dropDepth.current > 0) return
    setDropOver(false)
    setDropTarget(null)
    setDropRect(null)
  }
  const handleBodyDragOver = (event: DragEvent): void => {
    event.preventDefault()
    event.stopPropagation()
    event.dataTransfer.dropEffect = busy ? 'none' : 'copy'
    if (busy) return
    // Rows stop propagation, so this only fires over non-row regions: the
    // drag targets the workspace root. dragover fires continuously, making
    // it the authoritative (flicker-free) place to clear the row target.
    setDropTarget(null)
  }
  const handleRowDragOver = (event: DragEvent, dir: string): void => {
    event.preventDefault()
    event.stopPropagation()
    event.dataTransfer.dropEffect = busy ? 'none' : 'copy'
    if (busy) return
    setDropTarget(dir)
  }

  const storeLevel = useCallback((path: string, level: LevelData) => {
    dataRef.current = { ...dataRef.current, [path]: level }
    setData(dataRef.current)
  }, [])

  const loadDir = useCallback((dir: string) => {
    if (dataRef.current[dir] !== undefined) return
    storeLevel(dir, {})
    api.fsTree({ sessionId, cwd }, dir).then((listing) => {
      storeLevel(dir, { entries: listing.entries })
    }).catch((error: unknown) => {
      storeLevel(dir, { error: error instanceof Error ? error.message : String(error) })
    })
  }, [sessionId, cwd, storeLevel])

  // The caller's refresh tick wipes the cache (declared BEFORE the load
  // effect so the reload below sees the empty cache).
  const lastTick = useRef(refreshTick)
  useEffect(() => {
    if (lastTick.current === refreshTick) return
    lastTick.current = refreshTick
    dataRef.current = {}
    setData({})
  }, [refreshTick])

  useEffect(() => {
    // Load the visible set; already-loaded levels (kept in the cache) are
    // not refetched. Only the refresh tick wipes the cache.
    const root = cwd
    if (root === undefined) return
    loadDir(root)
    for (const dir of expanded) loadDir(dir)
  }, [cwd, expanded, refreshTick, loadDir])

  /** Copy `text`; on success flip the row's copied label for a moment. */
  const copyPath = useCallback((text: string, path: string): void => {
    void writeClipboard(text).then((ok) => {
      if (!ok) return
      setCopiedPath(path)
      window.setTimeout(() => {
        setCopiedPath(current => current === path ? null : current)
      }, COPIED_MS)
    })
  }, [])

  /** The row's trailing actions: the @-reference button, or the copied label. */
  const rowActions = (entry: FsEntry): ReactNode => {
    if (copiedPath === entry.path) {
      return <span className={css.explorerCopied}>{t('copied')}</span>
    }
    return (
      <button
        type="button"
        className={css.explorerRef}
        aria-label={t('referenceFile')}
        title={t('referenceFile')}
        onClick={(event) => {
          event.stopPropagation()
          onReferenceFile(entry.path)
        }}
      >
        {t('referenceFile')}
      </button>
    )
  }

  const openRowMenu = (event: MouseEvent, path: string, isDir: boolean): void => {
    event.preventDefault()
    event.stopPropagation()
    setRowMenu({ path, isDir, x: event.clientX, y: event.clientY })
  }

  /** Download a file through the host route (raw bytes, binary-safe). */
  const downloadFile = (path: string): void => {
    const url = downloadUrl({ sessionId, cwd }, path)
    const anchor = document.createElement('a')
    anchor.href = url
    anchor.style.display = 'none'
    document.body.appendChild(anchor)
    anchor.click()
    anchor.remove()
  }

  const root = cwd

  const renderLevel = (dir: string, depth: number): ReactNode => {
    const level = data[dir]
    if (level === undefined) {
      return <div className={css.explorerRow} style={{ paddingLeft: depth * 22 + 6 }}>{t('loading')}</div>
    }
    if (level.error !== undefined) {
      return (
        <div className={clsx(css.explorerRow, css.explorerError)} style={{ paddingLeft: depth * 22 + 6 }}>
          {level.error}
        </div>
      )
    }
    const entries = level.entries ?? []
    return entries.map(entry => {
      if (entry.isDir) {
        const isOpen = expanded.includes(entry.path)
        return (
          <div key={entry.path}>
            <div
              role="button"
              tabIndex={0}
              className={clsx(
                css.explorerRow, css.explorerDir, entry.hidden && css.explorerHidden,
                dropTarget === entry.path && css.explorerRowDropTarget,
              )}
              style={{ paddingLeft: depth * 22 + 6 }}
              onClick={() => { onToggle(entry.path) }}
              onKeyDown={(event) => {
                if (event.key === 'Enter' || event.key === ' ') {
                  event.preventDefault()
                  onToggle(entry.path)
                }
              }}
              onDragOver={(event) => { handleRowDragOver(event, entry.path) }}
              onDrop={(event) => { handleDirDrop(event, entry.path) }}
              onContextMenu={(event) => { openRowMenu(event, entry.path, true) }}
            >
              {isOpen ? <IconFolderOpen16 size={14} /> : <IconFolderClose16 size={14} />}
              <span className={css.explorerName}>{entry.name}</span>
              {entry.isSymlink && <IconLinkOutline16 size={12} className={css.explorerSymlink} />}
              {rowActions(entry)}
            </div>
            {isOpen && renderLevel(entry.path, depth + 1)}
          </div>
        )
      }
      return (
        <div
          key={entry.path}
          role="button"
          tabIndex={0}
          className={clsx(
            css.explorerRow, entry.hidden && css.explorerHidden, entry.broken && css.explorerBroken,
            dropTarget === parentOf(entry.path) && css.explorerRowDropTarget,
          )}
          style={{ paddingLeft: depth * 22 + 6 }}
          title={entry.broken ? `${entry.path} — ${t('brokenSymlink')}` : entry.path}
          onClick={() => { onOpenFile(entry.path) }}
          onKeyDown={(event) => {
            if (event.key === 'Enter' || event.key === ' ') {
              event.preventDefault()
              onOpenFile(entry.path)
            }
          }}
          onDragOver={(event) => { handleRowDragOver(event, parentOf(entry.path)) }}
          onDrop={(event) => { handleFileDrop(event, entry.path) }}
          onContextMenu={(event) => { openRowMenu(event, entry.path, false) }}
        >
          <IconCodeOutline16 size={14} />
          <span className={css.explorerName}>{entry.name}</span>
          {entry.isSymlink && <IconLinkOutline16 size={12} className={css.explorerSymlink} />}
          {rowActions(entry)}
        </div>
      )
    })
  }

  return (
    <div
      ref={bodyRef}
      className={css.explorerBody}
      onDragEnter={handleBodyDragEnter}
      onDragOver={handleBodyDragOver}
      onDragLeave={handleBodyDragLeave}
      onDrop={handleBodyDrop}
    >
      {root === undefined ? (
        <div className={css.explorerEmpty}>{t('noSession')}</div>
      ) : (
        <>
          <div
            className={clsx(css.explorerRow, dropTarget === root && css.explorerRowDropTarget)}
            style={{ paddingLeft: 6 }}
            onDragOver={(event) => { handleRowDragOver(event, root) }}
            onDrop={(event) => { handleDirDrop(event, root) }}
            onContextMenu={(event) => { openRowMenu(event, root, true) }}
          >
            <IconFolderOpen16 size={14} />
            <span className={css.explorerName}>{baseName(root)}</span>
            {copiedPath === root
              ? <span className={css.explorerCopied}>{t('copied')}</span>
              : (
                <button
                  type="button"
                  className={css.explorerRef}
                  aria-label={t('referenceFile')}
                  title={t('referenceFile')}
                  onClick={(event) => {
                    event.stopPropagation()
                    onReferenceFile(root)
                  }}
                >
                  {t('referenceFile')}
                </button>
              )}
          </div>
          {data[root] !== undefined && renderLevel(root, 1)}
        </>
      )}
      {dropOver && dropRect !== null && createPortal(
        /*
         * The sidebar's drop surface, portaled to document.body at z-1001 —
         * above DSH's own whole-page drop mask (z-1000, see InputBar's
         * document-level intake) so the two never compete. It dims the WHOLE
         * viewport (the giant box-shadow spread on the zone frame is the
         * mask; the zone rect itself stays clear), teaching the zone split:
         * the dimmed conversation column still takes drops into the chat
         * natively (this layer is pointer-inert), while the clear frame
         * marks the tree as the workspace-upload zone. Deliberate exception
         * to the "panel stays below the DSH float stack" rule: transient,
         * and the drop always lands on the element beneath. The hint pill
         * docks at the TOP edge of the zone — right under the search row,
         * the first thing the eye meets — keeping the rows aimable.
         */
        <>
          <div
            className={css.uploadDropZone}
            style={{
              top: dropRect.top + 2,
              left: dropRect.left + 2,
              width: dropRect.width - 4,
              height: dropRect.height - 4,
            }}
          >
            <div className={css.uploadDropHero}>
              <UploadDropIllustration />
              <div className={css.uploadDropZonePill}>
                <IconUploadOutline16 size={14} />
                <span className={css.uploadDropZoneText}>
                  {dropTarget !== null ? t('uploadTo', { dir: dropTarget }) : t('uploadDropHint')}
                </span>
              </div>
            </div>
          </div>
          {/* The left zone's invitation, centered in the space beside the
              tree; skipped when that space is too narrow to hold it. */}
          {dropRect.left >= 200 && (
            <div className={css.uploadDropChatHint} style={{ width: dropRect.left }}>
              <div className={css.uploadDropChatCard}>
                <ChatDropIllustration />
                <span>{t('uploadDropChat')}</span>
              </div>
            </div>
          )}
        </>,
        document.body,
      )}
      {/*
        The one shared context menu, positioned at the right-click cursor
        (portal so the tree's overflow clip cannot crop it).
      */}
      <input
        ref={fileInputRef}
        type="file"
        multiple
        style={{ display: 'none' }}
        onChange={(event) => {
          const dir = pendingUploadDir.current ?? root
          pendingUploadDir.current = undefined
          if (dir !== undefined && !busy) onUploadRequest(dir, uploadItemsFromFiles(event.target.files ?? []))
          event.target.value = ''
        }}
      />
      <Menu
        open={rowMenu !== null}
        onClose={() => { setRowMenu(null) }}
        items={[
          // The open escapes head the FILE menu (dirs only get copy).
          ...(rowMenu?.isDir === false && onOpenFileNewTab !== undefined
            ? [{ id: 'open-new-tab', label: t('openFileNewTab'), icon: <IconCodeOutline16 size={14} /> }]
            : []),
          ...(rowMenu?.isDir === false && onOpenFileSide !== undefined
            ? [{ id: 'open-side', label: t('openFileSide'), icon: <IconFolderOpen16 size={14} /> }]
            : []),
          // Download applies to files only (the host route refuses directories).
          ...(rowMenu?.isDir === false
            ? [{ id: 'download', label: t('download'), icon: <IconDownloadOutline16 size={14} /> }]
            : []),
          // Upload into a directory (incl. the workspace root row).
          ...(rowMenu?.isDir === true
            ? [{ id: 'upload-here', label: t('uploadHere'), icon: <IconUploadOutline16 size={14} /> }]
            : []),
          { id: 'relative', label: t('copyRelative'), icon: <IconCopyOutline16 size={14} /> },
          { id: 'absolute', label: t('copyAbsolute'), icon: <IconCopyOutline16 size={14} /> },
        ]}
        onSelect={(id) => {
          const target = rowMenu
          if (target === null) return
          setRowMenu(null)
          if (id === 'open-new-tab') {
            onOpenFileNewTab?.(target.path)
            return
          }
          if (id === 'open-side') {
            onOpenFileSide?.(target.path)
            return
          }
          if (id === 'download') {
            downloadFile(target.path)
            return
          }
          if (id === 'upload-here') {
            pendingUploadDir.current = target.path
            fileInputRef.current?.click()
            return
          }
          copyPath(
            id === 'relative' ? relativeTo(cwd ?? '', target.path) : target.path,
            target.path,
          )
        }}
        portal
        align="start"
        getAnchorRect={() => (rowMenu === null ? null : new DOMRect(rowMenu.x, rowMenu.y, 0, 0))}
        anchor={<span />}
      />
    </div>
  )
}