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/**
* `<JsonViewer />` — the React layer over the engine (SPEC.md §4.9).
*
* Everything expensive lives below this file. What happens here is assembly:
* resolve the input, window the rows, keep the scroll anchored across
* expansion changes, run the search off the main thread, and expose the
* whole thing as an ARIA tree.
*/
import {
useCallback,
useEffect,
useId,
useImperativeHandle,
useMemo,
useRef,
useState,
} from "react";
import { useControllableState } from "@usefy/use-controllable-state";
import { useCopyToClipboard } from "@usefy/use-copy-to-clipboard";
import { useDebounceCallback } from "@usefy/use-debounce-callback";
import { useEventCallback } from "@usefy/use-event-callback";
import { useIsomorphicLayoutEffect } from "@usefy/use-isomorphic-layout-effect";
import { useMergedRefs } from "@usefy/use-merged-refs";
import { useResizeObserver } from "@usefy/use-resize-observer";
import { Row } from "./Row";
import { SearchBar } from "./SearchBar";
import { Toolbar } from "./Toolbar";
import { ValueOverlay } from "./ValueOverlay";
import { cx } from "./cx";
import { formatPath, pathToPointer } from "./model/path";
import { serializeSubtree } from "./model/serialize";
import { displayOf } from "./model/value";
import { searchJson } from "./search/scan";
import styles from "./styles/JsonViewer.module.scss";
import { useJsonTree } from "./useJsonTree";
import { useRowWindow } from "./useRowWindow";
import { useTreeKeyboard } from "./useTreeKeyboard";
import type {
ExpandResult,
JsonPath,
JsonRow,
JsonSearchOptions,
JsonSearchProgress,
JsonTreeOptions,
PathFormat,
} from "./types";
/** Imperative handle for consumers that need to drive the viewer. */
export interface JsonViewerController {
expand: (path: JsonPath) => ExpandResult;
collapse: (path: JsonPath) => ExpandResult;
expandAll: (maxDepth?: number) => ExpandResult;
collapseAll: () => ExpandResult;
scrollToPath: (path: JsonPath) => void;
search: (query: string) => void;
getRowCount: () => number;
}
export interface JsonViewerProps
extends JsonTreeOptions,
Omit<React.HTMLAttributes<HTMLDivElement>, "onCopy" | "onError" | "children"> {
/** The value to render. Preferred — it is never parsed, cloned or mutated. */
data?: unknown;
/** Raw JSON text. Parsed per SPEC decision #5; use `data` when you already have a value. */
json?: string;
/**
* Above this many characters of `json`, a "Parsing…" state paints first.
* 40 MB parses in ~400 ms, which is not a bottleneck but *is* long enough to
* read as a frozen tab with no feedback.
* @defaultValue 2_097_152 (2 MB)
*/
parseSyncLimit?: number;
/** Controlled expansion state, as RFC 6901 pointers. */
expanded?: readonly string[];
defaultExpanded?: readonly string[];
onExpandedChange?: (paths: string[]) => void;
query?: string;
defaultQuery?: string;
onQueryChange?: (query: string) => void;
searchOptions?: Omit<JsonSearchOptions, "query" | "signal">;
/** @defaultValue 22 */
rowHeight?: number;
/** @defaultValue 400 */
height?: number | string;
/** @defaultValue "js" */
pathFormat?: PathFormat;
/** @defaultValue true */
showSearch?: boolean;
/** @defaultValue true */
showToolbar?: boolean;
/** @defaultValue false */
showDataTypes?: boolean;
/** @defaultValue false */
quoteKeys?: boolean;
/** @defaultValue "auto" */
theme?: "light" | "dark" | "auto";
renderValue?: (row: JsonRow) => React.ReactNode;
onCopy?: (payload: { kind: "path" | "value"; text: string; row: JsonRow }) => void;
onRowClick?: (row: JsonRow, event: React.MouseEvent) => void;
onError?: (error: Error) => void;
controllerRef?: React.Ref<JsonViewerController>;
}
const DEFAULT_PARSE_SYNC_LIMIT = 2 * 1024 * 1024;
interface Parsed {
value: unknown;
error: string | null;
}
export function JsonViewer({
data,
json,
parseSyncLimit = DEFAULT_PARSE_SYNC_LIMIT,
expanded,
defaultExpanded,
onExpandedChange,
query: queryProp,
defaultQuery,
onQueryChange,
searchOptions,
rowHeight = 22,
height = 400,
pathFormat = "js",
showSearch = true,
showToolbar = true,
showDataTypes = false,
quoteKeys = false,
theme = "auto",
renderValue,
onCopy,
onRowClick,
onError,
controllerRef,
maxValueLength = 120,
sortKeys,
defaultExpandDepth,
maxExpandedRows,
denseThreshold,
className,
style,
"aria-label": ariaLabel,
...rest
}: JsonViewerProps) {
const baseId = useId();
const rootRef = useRef<HTMLDivElement>(null);
const scrollRef = useRef<HTMLDivElement>(null);
const reportError = useEventCallback((error: Error) => onError?.(error));
// ── input ───────────────────────────────────────────────────────────────
const syncParse = useMemo<Parsed | null>(() => {
if (json === undefined || json.length > parseSyncLimit) return null;
try {
return { value: JSON.parse(json), error: null };
} catch (error) {
return { value: undefined, error: (error as Error).message };
}
}, [json, parseSyncLimit]);
const [asyncParse, setAsyncParse] = useState<Parsed | null>(null);
useEffect(() => {
if (json === undefined || json.length <= parseSyncLimit) {
setAsyncParse(null);
return;
}
setAsyncParse(null);
// One frame so the "Parsing…" state actually paints before the main
// thread disappears into JSON.parse.
let cancelled = false;
const schedule =
typeof requestAnimationFrame === "function"
? requestAnimationFrame
: (callback: () => void) => setTimeout(callback, 0) as unknown as number;
const handle = schedule(() => {
Iif (cancelled) return;
try {
setAsyncParse({ value: JSON.parse(json), error: null });
} catch (error) {
setAsyncParse({ value: undefined, error: (error as Error).message });
}
});
return () => {
cancelled = true;
Eif (typeof cancelAnimationFrame === "function") cancelAnimationFrame(handle);
};
}, [json, parseSyncLimit]);
const parsed: Parsed | null = json === undefined ? { value: data, error: null } : (syncParse ?? asyncParse);
const parseError = parsed?.error ?? null;
const value = parsed?.value;
useEffect(() => {
if (parseError) reportError(new SyntaxError(parseError));
}, [parseError, reportError]);
// ── model ───────────────────────────────────────────────────────────────
const tree = useJsonTree({
data: value,
expanded,
defaultExpanded,
onExpandedChange,
maxValueLength,
sortKeys,
defaultExpandDepth,
maxExpandedRows,
denseThreshold,
});
const { model, rowCount } = tree;
const { ref: resizeRef, height: measuredHeight } = useResizeObserver<HTMLDivElement>();
const mergedScrollRef = useMergedRefs<HTMLDivElement>(scrollRef, resizeRef);
const {
window: rowWindow,
anchor,
scrollToRow,
ensureRowVisible,
} = useRowWindow({
scrollRef,
rowHeight,
rowCount,
viewportHeight: measuredHeight,
});
const [announcement, setAnnouncement] = useState("");
const announce = useCallback((message: string) => setAnnouncement(message), []);
/** The row `aria-activedescendant` points at — the tree's one "cursor". */
const [activeRow, setActiveRow] = useState(0);
const applyExpansion = useCallback(
(result: ExpandResult) => {
anchor(result);
if (result.refused?.reason === "row-budget") {
announce(
`Too large to expand fully — stopped at the ${result.refused.budget?.toLocaleString()} row limit`,
);
}
return result;
},
[anchor, announce],
);
const toggle = useCallback(
(path: JsonPath) => applyExpansion(tree.toggle(path)),
[applyExpansion, tree],
);
const expand = useCallback(
(path: JsonPath) => applyExpansion(tree.expand(path)),
[applyExpansion, tree],
);
const collapse = useCallback(
(path: JsonPath) => applyExpansion(tree.collapse(path)),
[applyExpansion, tree],
);
// ── copy ────────────────────────────────────────────────────────────────
const [, copyToClipboard] = useCopyToClipboard();
const copyText = useEventCallback(
(kind: "path" | "value", text: string, row: JsonRow) => {
void copyToClipboard(text).then((ok) => {
announce(ok ? `Copied the ${kind}` : `Could not copy the ${kind}`);
Eif (!ok) reportError(new Error(`json-viewer: copying the ${kind} failed`));
});
onCopy?.({ kind, text, row });
},
);
const copyPath = useEventCallback((row: JsonRow) => {
copyText("path", formatPath(row.path, pathFormat), row);
});
const copyValue = useEventCallback((row: JsonRow) => {
const result = serializeSubtree(row.value);
Iif (result.refused) {
announce(
`That value is too large to copy (over ${Math.round(result.refused.maxBytes / 1024 / 1024)} MB)`,
);
return;
}
copyText("value", result.text, row);
});
// ── the full-value overlay ──────────────────────────────────────────────
const [overlay, setOverlay] = useState<{
text: string;
label: string;
top: number;
left: number;
rowIndex: number;
} | null>(null);
const showFull = useEventCallback((row: JsonRow, anchorElement: HTMLElement) => {
const rootBox = rootRef.current?.getBoundingClientRect();
const anchorBox = anchorElement.getBoundingClientRect();
const text =
typeof row.value === "string"
? row.value
: displayOf(row.value, row.kind, Number.MAX_SAFE_INTEGER).text;
setOverlay({
text,
label: row.label,
top: rootBox ? anchorBox.bottom - rootBox.top + 4 : 0,
left: rootBox ? Math.max(8, anchorBox.left - rootBox.left) : 0,
rowIndex: row.index,
});
});
const closeOverlay = useCallback(() => {
// Focus returns to the tree with the originating row active — the tree is
// the single tab stop, so "the row" is `aria-activedescendant`, not an
// element that can hold focus itself.
setOverlay((current) => {
Eif (current) setActiveRow(current.rowIndex);
return null;
});
scrollRef.current?.focus();
}, []);
// ── search ──────────────────────────────────────────────────────────────
const [query, setQuery] = useControllableState<string>({
value: queryProp,
defaultValue: defaultQuery ?? "",
onChange: onQueryChange,
});
const [matches, setMatches] = useState<JsonPath[]>([]);
const [progress, setProgress] = useState<JsonSearchProgress | null>(null);
const [searchError, setSearchError] = useState<string | null>(null);
const [currentMatch, setCurrentMatch] = useState(0);
/** The query whose scan has finished; anything else means results are stale. */
const [completedQuery, setCompletedQuery] = useState("");
const searchAbort = useRef<AbortController | null>(null);
const runSearch = useEventCallback(() => {
searchAbort.current?.abort();
Iif (!query) {
setMatches([]);
setProgress(null);
setSearchError(null);
setCurrentMatch(0);
setCompletedQuery("");
return;
}
const controller = new AbortController();
searchAbort.current = controller;
let options: JsonSearchOptions;
try {
options = { ...searchOptions, query, signal: controller.signal };
// Fail fast on an invalid pattern rather than throwing inside the scan.
if (options.regex) new RegExp(query);
} catch (error) {
setSearchError((error as Error).message);
setMatches([]);
setProgress(null);
return;
}
setSearchError(null);
// The progress callback needs the same guard as the result: a superseded
// scan runs on until its next yield, and its last report would otherwise
// overwrite the live scan's.
const report = (next: JsonSearchProgress) => {
Eif (!controller.signal.aborted) setProgress(next);
};
void searchJson(value, options, report)
.then((result) => {
Iif (controller.signal.aborted) return;
setMatches(result.paths);
setCurrentMatch(0);
setCompletedQuery(query);
if (result.capped) {
announce(`Showing the first ${result.paths.length.toLocaleString()} matches`);
} else {
announce(
result.paths.length === 0
? "No matches"
: `${result.paths.length.toLocaleString()} matches`,
);
}
})
.catch((error: unknown) => {
if (controller.signal.aborted) return;
setSearchError((error as Error).message);
reportError(error as Error);
});
});
const debouncedSearch = useDebounceCallback(runSearch, 180);
// `searchOptions` is deliberately absent from the dependencies: it is read
// through `runSearch`, which is an event callback and always sees the latest
// props. Including it would restart the 180 ms debounce on every parent
// re-render for the common case of an inline object literal — a parent
// re-rendering faster than that would stop the search ever starting.
useEffect(() => {
debouncedSearch();
return () => debouncedSearch.cancel();
}, [query, value, debouncedSearch]);
useEffect(() => () => searchAbort.current?.abort(), []);
const matchSet = useMemo(() => new Set(matches.map(pathToPointer)), [matches]);
const currentMatchPointer =
matches.length > 0 ? pathToPointer(matches[currentMatch % matches.length]!) : null;
const goToMatch = useCallback(
(index: number) => {
Iif (matches.length === 0) return;
const next = ((index % matches.length) + matches.length) % matches.length;
setCurrentMatch(next);
const path = matches[next]!;
applyExpansion(tree.expandTo(path));
const row = model.rowIndexOf(path);
Eif (row >= 0) {
setActiveRow(row);
scrollToRow(row);
}
announce(`Match ${next + 1} of ${matches.length}`);
},
[matches, applyExpansion, tree, model, scrollToRow, announce],
);
// ── keyboard ────────────────────────────────────────────────────────────
const pageSize = Math.max(1, Math.floor((measuredHeight || 400) / rowHeight) - 1);
const onKeyDown = useTreeKeyboard({
model,
rowCount,
activeRow,
setActiveRow,
toggle,
expand,
collapse,
pageSize,
// Scroll into view, not to view: an arrow key must be able to walk the
// highlight down the rows already on screen.
onMove: ensureRowVisible,
announce,
onCopyValue: copyValue,
onCopyPath: copyPath,
});
// Keep the active row inside the tree even after a collapse removed it.
useIsomorphicLayoutEffect(() => {
Iif (activeRow >= rowCount) setActiveRow(Math.max(0, rowCount - 1));
}, [activeRow, rowCount]);
// ── controller ──────────────────────────────────────────────────────────
useImperativeHandle(
controllerRef,
() => ({
expand,
collapse,
expandAll: (maxDepth?: number) => applyExpansion(tree.expandAll(maxDepth)),
collapseAll: () => applyExpansion(tree.collapseAll()),
scrollToPath: (path: JsonPath) => {
applyExpansion(tree.expandTo(path));
const row = model.rowIndexOf(path);
if (row >= 0) {
setActiveRow(row);
scrollToRow(row);
}
},
search: setQuery,
getRowCount: () => model.rowCount(),
}),
[expand, collapse, applyExpansion, tree, model, scrollToRow, setQuery],
);
// ── render ──────────────────────────────────────────────────────────────
const rows: JsonRow[] = [];
for (let index = rowWindow.start; index < rowWindow.end; index++) {
rows.push(model.rowAt(index));
}
const activeVisible = activeRow >= rowWindow.start && activeRow < rowWindow.end;
const parsing = parsed === null;
return (
<div
{...rest}
ref={rootRef}
data-usefy-theme={theme === "auto" ? undefined : theme}
className={cx(styles.root, className)}
style={{
...style,
height,
["--usefy-json-row-height" as string]: `${rowHeight}px`,
}}
>
{showToolbar ? (
<Toolbar
rowCount={rowCount}
onExpandAll={() => applyExpansion(tree.expandAll())}
onCollapseAll={() => applyExpansion(tree.collapseAll())}
onCopyAll={() => copyValue(model.rowAt(0))}
/>
) : null}
{showSearch ? (
<SearchBar
query={query}
onQueryChange={setQuery}
matchCount={matches.length}
currentMatch={currentMatch}
progress={progress}
scanning={query !== "" && completedQuery !== query && searchError === null}
error={searchError}
onPrevious={() => goToMatch(currentMatch - 1)}
onNext={() => goToMatch(currentMatch + 1)}
/>
) : null}
{parseError ? (
<div className={styles.error} role="alert">
{`Could not parse the JSON: ${parseError}`}
</div>
) : parsing ? (
<div className={styles.parsing}>Parsing…</div>
) : (
<div
ref={mergedScrollRef}
className={styles.scroll}
role="tree"
tabIndex={0}
aria-label={ariaLabel ?? "JSON tree"}
aria-activedescendant={
activeVisible ? `${baseId}-row-${activeRow}` : undefined
}
onKeyDown={onKeyDown}
data-testid="json-scroll"
>
<div
className={styles.sizer}
style={{ height: rowWindow.contentHeight }}
role="none"
>
<div
className={styles.rows}
style={{ transform: `translateY(${rowWindow.offset}px)` }}
role="none"
>
{rows.map((row) => (
<Row
key={row.index}
id={`${baseId}-row-${row.index}`}
row={row}
active={row.index === activeRow}
matched={matchSet.has(pathToPointer(row.path)) && !row.closing}
currentMatch={
!row.closing && currentMatchPointer === pathToPointer(row.path)
}
showDataTypes={showDataTypes}
quoteKeys={quoteKeys}
onToggle={toggle}
onActivate={setActiveRow}
onCopyPath={copyPath}
onCopyValue={copyValue}
onShowFull={showFull}
onRowClick={onRowClick}
renderValue={renderValue}
/>
))}
</div>
</div>
</div>
)}
{overlay ? (
<ValueOverlay
text={overlay.text}
label={overlay.label}
top={overlay.top}
left={overlay.left}
onCopy={() => {
void copyToClipboard(overlay.text).then((ok) =>
announce(ok ? "Copied the value" : "Could not copy the value"),
);
}}
onClose={closeOverlay}
/>
) : null}
<div className={styles.status} role="status" aria-live="polite">
{announcement}
</div>
</div>
);
}
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