/**
 * The changes tab's shared bottom preview pane: one selected target — a git
 * worktree change, a commit patch, or a session file op — rendered through
 * the unified diff stack (the same one the diff tab uses). Git targets load
 * through the shared {@link useGitDiffTarget} hook (refreshable, with the
 * untracked full-addition fallback); op targets are pure snapshots (diff /
 * read view / error text). The pane is resizable by drag (clamped; the
 * height commits to the tab's persisted meta on release) and by keyboard;
 * git targets can expand into a dedicated diff tab via the shell.
 */
import { useEffect, useMemo, useRef, useState, type PointerEvent as ReactPointerEvent } from 'react'
import { IconCloseOutlineRegular, IconRefreshOutlineRegular, IconRightUpOutlineRegular, MarkdownText } from '@deepseek-ai/dsh-client-ui-primitives'
import type { SessionScope } from '../api.ts'
import { htmlUrl } from '../api.ts'
import { t } from '../locales.ts'
import { baseName } from '../paths.ts'
import { resolveSidebarPath } from '../paths.ts'
import { HTML_IFRAME_SANDBOX } from '../html-preview.ts'
import type { SidebarDiffRef, SidebarTab } from '../state.ts'
import { DiffRows, ReadRows } from '../diff/DiffRows.tsx'
import { PdfView } from '../PdfView.tsx'
import { DiffFiles } from '../diff/DiffFiles.tsx'
import { langOfPath } from '../diff/highlight.ts'
import { buildDiffSegments, diffLines, diffStats, parseUnifiedDiff, unifiedSegments, type DiffRow } from '../diff/rows.ts'
import { useGitDiffTarget } from '../diff/use-git-diff.ts'
import { parseReadContent, parseReadLines, type FileOp } from './ops.ts'
import { redactText } from '../redact.ts'
import { rewriteLocalImageUrls } from '../markdown-images.ts'
import { markdownTextProps } from '../markdown-labels.tsx'
import { splitMermaidBlocks } from '../mermaid-blocks.ts'
import { LazyMermaidMarkdown } from '../mermaid-lazy.tsx'
import { createFrameBatcher } from '../frame-batcher.ts'
import { Chip, IconButton, Notice, StatusBadge } from '../ui/index.ts'
import css from './changes.module.css'
import diffCss from '../diff/diff.module.css'

/** Drag handle height clamp (px) and keyboard-resize step. */
const HEIGHT_MIN = 140
const HEIGHT_STEP = 24

/**
 * Clamp one pane height to the pane's own bounds: never below the content
 * minimum, never above 70% of the window. Both the drag handler and the
 * RESTORE path (a height persisted under a taller window) run through this,
 * so a saved value can never open the pane taller than the viewport allows.
 */
export function clampPaneHeight(value: number): number {
  return Math.min(Math.max(value, HEIGHT_MIN), Math.round(window.innerHeight * 0.7))
}

/** The redaction preference, persisted under the repo's sidebar storage
 *  prefix (see state.ts's `dsh-sidebar:v1`). */
const REDACTION_KEY = 'dsh-sidebar:v1:redaction'

/** What the pane is showing right now. */
export type ChangesPreview =
  | { kind: 'git'; ref: SidebarDiffRef }
  | { kind: 'op'; path: string; op: FileOp; prior?: string }

/** Diff material for one op snapshot: an edit reconstructs the full file
 *  from the window's known prior content when possible (hunk-style context);
 *  a write with unknown prior content renders all-added. */
function diffOf(op: FileOp, prior: string | undefined): readonly DiffRow[] {
  if (op.kind === 'read') return []
  if (op.kind === 'edit' && op.edit !== undefined) {
    const { oldString, newString } = op.edit
    if (prior !== undefined && prior.includes(oldString)) {
      const newFile = prior.replace(oldString, newString)
      return diffLines(prior, newFile)
    }
    return diffLines(oldString, newString)
  }
  if (op.kind === 'write') {
    const content = op.content ?? ''
    const old = prior !== undefined && prior !== content ? prior : undefined
    return diffLines(old ?? '', content)
  }
  return []
}

/** The render view of one html op target: the route-src iframe. Extracted
 *  (and exported) so the always-sandboxed contract is pinned directly by the
 *  sandbox spec — this surface has NO no-sandbox escape hatch. */
export function HtmlRenderPreview(props: { src: string; title: string }) {
  return (
    <div className={css.htmlPane}>
      <iframe
        className={css.htmlFrame}
        title={props.title}
        src={props.src}
        sandbox={HTML_IFRAME_SANDBOX}
        referrerPolicy="no-referrer"
        allow=""
      />
    </div>
  )
}

/** One header pill toggle — the redaction / reading / render toggles share the
 *  shape: the global {@link Chip} (its active state is the "on" picture). */
function PaneToggle(props: { on: boolean; label: string; title?: string; onClick: () => void }) {
  return <Chip active={props.on} title={props.title} onClick={props.onClick}>{props.label}</Chip>
}

/** The reading-mode body of one markdown op target: the shared MarkdownText
 *  pass (local image destinations already rewritten to the media route by
 *  the caller). Mermaid fences render through the same chunk-resident
 *  renderer the editor preview uses (one MarkdownText pass with the fences
 *  lifted out); the plain path stays byte-for-byte for documents without
 *  any. */
function MdReadingView(props: { text: string }) {
  const codeLabels = {
    copyLabel: t('copy'),
    copiedLabel: t('copied'),
    codeLabel: t('codeBlockTitle'),
    wrapLabel: t('codeBlockWrap'),
    unwrapLabel: t('codeBlockUnwrap'),
  }
  const hasMermaid = splitMermaidBlocks(props.text).some((block) => block.kind === 'mermaid')
  return (
    <div className={css.paneBody}>
      <div className={css.mdBody}>
        {hasMermaid
          ? <LazyMermaidMarkdown text={props.text} codeLabels={codeLabels} />
          : <MarkdownText {...markdownTextProps(props.text, codeLabels)} />}
      </div>
    </div>
  )
}

/** The diff tab a git preview expands into (the shell owns placement). */
export function diffTabOf(ref: SidebarDiffRef): SidebarTab {
  if (ref.kind === 'worktree') {
    return {
      id: `diff:w:${encodeURIComponent(ref.worktree ?? '')}:${ref.staged ? 's' : 'u'}:${ref.path}`,
      type: 'diff',
      title: baseName(ref.path),
      diff: ref,
    }
  }
  return {
    id: `diff:c:${encodeURIComponent(ref.worktree ?? '')}:${ref.hashFull}`,
    type: 'diff',
    title: `${ref.hash} ${ref.subject}`,
    diff: ref,
  }
}

export interface DiffPaneProps {
  target: ChangesPreview
  scope: SessionScope
  /** The persisted pane height (px); drag commits a new one upwards. */
  height: number
  onHeightCommit: (height: number) => void
  onClose: () => void
  /** Expand the current git target into a dedicated diff tab. */
  onExpand: () => void
}

export function DiffPane({ target, scope, height, onHeightCommit, onClose, onExpand }: DiffPaneProps) {
  // ── Git target loading (the shared loader: staged-side fallback, the
  //    untracked full-addition fallback, refresh by tick, fold cache). ─────
  const gitRef = target.kind === 'git' ? target.ref : null
  const { loading, error, diffText, untracked, refresh, resolveFold } = useGitDiffTarget(gitRef, scope)

  // ── Op target material (pure snapshots; the prior content came with the
  //    target so a running op shows what is already known). ────────────────
  const opRaw = target.kind === 'op' ? target.op : null
  const priorRaw = target.kind === 'op' ? target.prior : undefined
  // Secret redaction: on by default, toggle persists per browser (localStorage).
  // Every op payload consumer below (diff rows, read rows, markdown source,
  // error text) renders from the REDACTED shape, so masked payloads are the
  // only thing that can reach the DOM while the toggle is on. Display-only:
  // session events and the fs layer keep their original bytes.
  const [redactionOn, setRedactionOn] = useState((): boolean => {
    try { return localStorage.getItem(REDACTION_KEY) !== '0' } catch { return true }
  })
  const toggleRedaction = (): void => {
    setRedactionOn((prev) => {
      const next = !prev
      try { localStorage.setItem(REDACTION_KEY, next ? '1' : '0') } catch { /* storage unavailable */ }
      return next
    })
  }
  const { op, prior, redactionHit } = useMemo(() => {
    if (opRaw === null || !redactionOn) return { op: opRaw, prior: priorRaw, redactionHit: false }
    const path = target.kind === 'op' ? target.path : ''
    // One redactText pass per field: the outcome carries both the masked
    // text and whether anything was hit.
    const mask = (text: string | undefined): { masked: string | undefined; hit: boolean } => {
      if (text === undefined) return { masked: undefined, hit: false }
      const outcome = redactText(path, text)
      return { masked: outcome.text, hit: outcome.hit }
    }
    const read = mask(opRaw.read)
    const content = mask(opRaw.content)
    const editOld = mask(opRaw.edit?.oldString)
    const editNew = mask(opRaw.edit?.newString)
    const errorText = mask(opRaw.errorText)
    const priorMasked = mask(priorRaw)
    const hit = read.hit || content.hit || editOld.hit || editNew.hit || errorText.hit || priorMasked.hit
    if (!hit) return { op: opRaw, prior: priorRaw, redactionHit: false }
    const redacted: FileOp = {
      ...opRaw,
      ...(read.masked !== undefined ? { read: read.masked } : {}),
      ...(content.masked !== undefined ? { content: content.masked } : {}),
      ...(opRaw.edit !== undefined
        ? { edit: { oldString: editOld.masked ?? opRaw.edit.oldString, newString: editNew.masked ?? opRaw.edit.newString } }
        : {}),
      ...(errorText.masked !== undefined ? { errorText: errorText.masked } : {}),
    }
    return { op: redacted, prior: priorMasked.masked, redactionHit: true }
  }, [opRaw, priorRaw, target, redactionOn])
  const opLang = useMemo(() => (target.kind === 'op' ? langOfPath(target.path) : undefined), [target])
  const opRows = useMemo(() => (op === null ? [] : diffOf(op, prior)), [op, prior])
  const opSegments = useMemo(() => buildDiffSegments(opRows), [opRows])
  const opStats = useMemo(() => diffStats(opSegments), [opSegments])
  const opReadLines = useMemo(
    () => (op?.kind === 'read' && op.read !== undefined ? parseReadLines(op.read) : []),
    [op],
  )

  // ── Markdown reading mode: .md op targets (read/write/edit, non-error)
  //    toggle between the raw/diff view and the rendered document — the same
  //    shared MarkdownText pass the editor preview uses, with local image
  //    destinations rewritten through the /sidebar/file media route. ──────
  const mdOp = target.kind === 'op' && !target.op.isError && /\.(md|markdown|mdx)$/i.test(target.path)
  const [reading, setReading] = useState(false)
  const readingSrc = useMemo(() => {
    if (!mdOp || op === null) return ''
    if (op.kind === 'read') return parseReadContent(op.read ?? '')
    if (op.kind === 'write') return op.content ?? ''
    if (op.kind === 'edit' && op.edit !== undefined) {
      if (prior !== undefined && prior.includes(op.edit.oldString)) {
        return prior.replace(op.edit.oldString, op.edit.newString)
      }
      return op.edit.newString
    }
    return ''
  }, [mdOp, op, prior])
  const readingText = useMemo(
    () => (mdOp && reading && readingSrc !== '' && target.kind === 'op'
      ? rewriteLocalImageUrls(readingSrc, scope, target.path, window.location.origin)
      : ''),
    [mdOp, reading, readingSrc, scope, target],
  )

  // ── HTML render mode: .html/.htm op targets (the editor html viewer's
  //    ext set) load the SAVED file through the same /sidebar/html route the
  //    editor's html viewer uses — relative assets (./style.css, img/x.png)
  //    resolve inside the route, and a segmented read still renders the
  //    whole document (the route serves the file, not the op snapshot). The
  //    frame is always sandboxed (the attribute plus the route's CSP sandbox
  //    header); the editor tab owns the warned no-sandbox escape hatch. ──
  const htmlOp = target.kind === 'op' && !target.op.isError && /\.(html?)$/i.test(target.path)
  const [rendering, setRendering] = useState(false)
  const htmlRenderSrc = useMemo(() => {
    if (!htmlOp || target.kind !== 'op') return ''
    return htmlUrl(scope, resolveSidebarPath(scope.cwd, target.path))
  }, [htmlOp, scope, target])

  // ── PDF render mode: .pdf op targets (read / write / edit, non-error) reuse
  //    the editor's PdfView verbatim — media-route bytes wrapped into an
  //    explicitly-typed Blob so the browser's native PDF viewer opens (a
  //    direct iframe src can fall back to a download). ──────────────────────
  const pdfOp = target.kind === 'op' && !target.op.isError && /\.pdf$/i.test(target.path)
  const [renderingPdf, setRenderingPdf] = useState(false)
  const pdfRenderPath = useMemo(() => {
    if (!pdfOp || target.kind !== 'op') return ''
    return resolveSidebarPath(scope.cwd, target.path)
  }, [pdfOp, scope, target])

  // Header stats for git targets come off the parsed patch text.
  const gitStats = useMemo(() => {
    if (target.kind !== 'git' || diffText === null || diffText === '') return null
    let added = 0
    let deleted = 0
    for (const file of parseUnifiedDiff(diffText).files) {
      const stats = diffStats(unifiedSegments(file))
      added += stats.added
      deleted += stats.deleted
    }
    return { added, deleted }
  }, [target, diffText])

  // ── Resize: drag the top handle; commit on release (persisted by the
  //    shell). Arrow keys resize by a step for keyboard users. ────────────
  const [dragHeight, setDragHeight] = useState<number | null>(null)
  const paneHeight = dragHeight ?? height
  const clamp = clampPaneHeight
  const dragOrigin = useRef<{ y: number; h: number } | null>(null)
  // Pointer streams fire several times per frame; one setState per event
  // re-rendered the whole pane at event cadence (see frame-batcher).
  const dragBatcher = useRef(createFrameBatcher()).current
  useEffect(() => () => dragBatcher.dispose(), [dragBatcher])
  const onHandleDown = (event: ReactPointerEvent<HTMLDivElement>): void => {
    event.preventDefault()
    dragOrigin.current = { y: event.clientY, h: paneHeight }
    const onMove = (ev: PointerEvent): void => {
      if (dragOrigin.current === null) return
      const next = clamp(dragOrigin.current.h + (dragOrigin.current.y - ev.clientY))
      dragBatcher.schedule(() => { setDragHeight(next) })
    }
    const onUp = (): void => {
      window.removeEventListener('pointermove', onMove)
      window.removeEventListener('pointerup', onUp)
      dragOrigin.current = null
      dragBatcher.flushNow()
      setDragHeight(current => {
        if (current !== null) onHeightCommit(current)
        return null
      })
    }
    window.addEventListener('pointermove', onMove)
    window.addEventListener('pointerup', onUp)
  }

  const title = target.kind === 'op'
    ? target.path
    : target.ref.kind === 'worktree' ? target.ref.path : `${target.ref.hash} ${target.ref.subject}`
  const stats = gitStats ?? (target.kind === 'op' && op !== null && op.kind !== 'read' && !op.isError ? opStats : null)

  return (
    <div className={css.diffPane} style={{ height: paneHeight }}>
      <div
        className={css.dragHandle}
        role="separator"
        aria-orientation="horizontal"
        aria-label={t('changesResizePreview')}
        tabIndex={0}
        onPointerDown={onHandleDown}
        onKeyDown={(event) => {
          if (event.key === 'ArrowUp') { event.preventDefault(); onHeightCommit(clamp(paneHeight + HEIGHT_STEP)) }
          if (event.key === 'ArrowDown') { event.preventDefault(); onHeightCommit(clamp(paneHeight - HEIGHT_STEP)) }
        }}
      />
      <div className={css.diffHead}>
        {target.kind === 'op' && (
          <StatusBadge tone={target.op.kind}>
            {t(target.op.kind === 'read' ? 'changesRead' : target.op.kind === 'write' ? 'changesWrite' : 'changesEdit')}
          </StatusBadge>
        )}
        {target.kind === 'git' && target.ref.kind === 'worktree' && (
          <StatusBadge tone="neutral">{target.ref.staged ? t('staged') : t('unstaged')}</StatusBadge>
        )}
        {target.kind === 'git' && target.ref.kind === 'commit' && (
          <StatusBadge tone="neutral">{target.ref.hash}</StatusBadge>
        )}
        <span className={css.diffPath} title={title}>{title}</span>
        {stats !== null && (stats.added > 0 || stats.deleted > 0) && (
          <span className={css.diffStats}>
            {stats.added > 0 && <span className={diffCss.statAdd}>+{String(stats.added)}</span>}
            {stats.deleted > 0 && <span className={diffCss.statDel}>−{String(stats.deleted)}</span>}
          </span>
        )}
        {target.kind === 'git' && (
          <>
            <IconButton
              size="sm"
              icon={<IconRefreshOutlineRegular size={14} />}
              label={t('refresh')}
              disabled={loading}
              onClick={refresh}
            />
            <IconButton
              size="sm"
              icon={<IconRightUpOutlineRegular size={14} />}
              label={t('changesOpenDiffTab')}
              onClick={onExpand}
            />
          </>
        )}
        {redactionHit && (
          <span className={css.redactBanner} role="status">{t('changesRedactBanner')}</span>
        )}
        {target.kind === 'op' && (
          <PaneToggle
            on={redactionOn}
            label={redactionOn ? t('changesRedactOnLabel') : t('changesRedactOffLabel')}
            title={redactionOn ? t('changesRedactOff') : t('changesRedactOn')}
            onClick={toggleRedaction}
          />
        )}
        {mdOp && (
          <PaneToggle
            on={reading}
            label={t(reading ? 'changesMdRaw' : 'changesMdReading')}
            onClick={() => { setReading(value => !value) }}
          />
        )}
        {htmlOp && (
          <PaneToggle
            on={rendering}
            label={t(rendering ? 'changesHtmlRaw' : 'changesHtmlRender')}
            onClick={() => { setRendering(value => !value) }}
          />
        )}
        {pdfOp && (
          <PaneToggle
            on={renderingPdf}
            label={t(renderingPdf ? 'changesPdfRaw' : 'changesPdfRender')}
            onClick={() => { setRenderingPdf(value => !value) }}
          />
        )}
        <IconButton
          size="sm"
          icon={<IconCloseOutlineRegular size={14} />}
          label={t('changesClosePreview')}
          onClick={onClose}
        />
      </div>
      {target.kind === 'op' && htmlOp && rendering && htmlRenderSrc !== ''
        ? <HtmlRenderPreview src={htmlRenderSrc} title={target.path} />
        : target.kind === 'op' && pdfOp && renderingPdf && pdfRenderPath !== ''
        ? (
          <div className={css.htmlPane}>
            <PdfView scope={scope} path={pdfRenderPath} title={target.path} />
          </div>
        )
        : target.kind === 'op' && mdOp && reading && readingText !== ''
        ? <MdReadingView text={readingText} />
        : target.kind === 'op' && op !== null && op.isError
        ? (
          <div className={css.paneBody}>
            <Notice kind="error" className={css.readError}>
              {op.errorText ?? t('changesError')}
            </Notice>
          </div>
        )
        : target.kind === 'op' && op !== null && op.kind === 'read'
          ? (
            <div className={css.paneBody}>
              <ReadRows lines={opReadLines} lang={opLang} />
            </div>
          )
          : target.kind === 'op'
            ? (
              <div className={css.paneBody}>
                {op !== null && op.kind === 'write'
                  && prior === undefined
                  && <Notice kind="hint" tone="inline">{t('changesPriorUnknown')}</Notice>}
                <DiffRows key={target.op.callId} segments={opSegments} lang={opLang} />
              </div>
            )
            : loading
              ? <div className={css.paneBody}><Notice kind="loading" tone="page">{t('loading')}</Notice></div>
              : error !== null
                ? (
                  <div className={css.paneBody}>
                    <Notice kind="error">{t('diffLoadError')}: {error}</Notice>
                  </div>
                )
                : (
                  <div className={css.paneBody}>
                    {/* The untracked fallback has NO diff text (git diff never
                        lists the file): its content is the whole render. */}
                    {((diffText !== null && diffText !== '') || untracked !== undefined) && (
                      <DiffFiles
                        diff={diffText ?? ''}
                        resolveFold={resolveFold}
                        untrackedPath={untracked !== undefined && target.ref.kind === 'worktree' ? target.ref.path : undefined}
                        untrackedContent={untracked}
                      />
                    )}
                    {diffText === '' && untracked === undefined && (
                      <Notice kind="empty" tone="page">{t('diffEmpty')}</Notice>
                    )}
                  </div>
                )}
    </div>
  )
}