paseo/packages/app/src/assistant-file-links/link.tsx

import { useMemo, useState, type CSSProperties, type MouseEvent, type ReactNode } from "react";
import {
  Pressable,
  Text,
  View,
  type StyleProp,
  type TextStyle,
  type ViewStyle,
} from "react-native";
import { StyleSheet } from "react-native-unistyles";
import { isNative, isWeb } from "@/constants/platform";
import { MarkdownTextSpan } from "@/components/markdown-text";
import { Shortcut } from "@/components/ui/shortcut";
import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip";
import { useStableEvent } from "@/hooks/use-stable-event";
import { CODE_SURFACE_DATASET } from "@/styles/code-surface";
import { useAssistantFileLinkResolverContext } from "./provider";
import type { AssistantFileLinkSource } from "./resolver";
import { useFileLink } from "./use-file-link";

interface AssistantMarkdownLinkProps {
  source: AssistantFileLinkSource;
  style: StyleProp<TextStyle>;
  monoSurface?: boolean;
  children: ReactNode;
}

export function AssistantMarkdownLink({
  source,
  style,
  monoSurface,
  children,
}: AssistantMarkdownLinkProps) {
  const [hovered, setHovered] = useState(false);
  const { target, onHoverIn, onPress, onAuxPress } = useFileLink(source);
  const { configRef } = useAssistantFileLinkResolverContext();
  const workspaceRoot = configRef.current.workspaceRoot;
  const tooltipPath = useMemo(
    () => (target ? formatInlinePathTargetForTooltip(target, workspaceRoot) : null),
    [target, workspaceRoot],
  );
  const handleAnchorClickCapture = useStableEvent((event: MouseEvent<HTMLAnchorElement>) => {
    event.preventDefault();
    if (!isModifiedOpenEvent(event)) {
      return;
    }
    event.stopPropagation();
    onAuxPress();
  });
  const handleHoverIn = useStableEvent(() => {
    setHovered(true);
    onHoverIn();
  });
  const handleHoverOut = useStableEvent(() => setHovered(false));
  const hoveredTextStyle = useMemo<StyleProp<TextStyle>>(
    () => [style, hovered && { textDecorationLine: "underline" as const }],
    [style, hovered],
  );

  if (isNative) {
    // Must be a MarkdownTextSpan, not a plain <Text>: on iOS the link renders
    // inside the paragraph's native UITextView, and a plain <Text> nested there
    // is not hoisted into a UITextViewChild, so its text is silently dropped
    // (the link disappears). The span composes correctly and stays selectable;
    // onPress is forwarded (reliable tap-to-open on iOS is tracked by #21).
    return (
      <FileLinkHoverTooltip filePath={tooltipPath}>
        <MarkdownTextSpan
          accessibilityRole="link"
          monoSurface={monoSurface}
          onPress={onPress}
          style={style}
        >
          {children}
        </MarkdownTextSpan>
      </FileLinkHoverTooltip>
    );
  }

  const anchor = (
    <a
      href={source.href}
      onClickCapture={handleAnchorClickCapture}
      onAuxClickCapture={preventAnchorNavigation}
      style={LINK_ANCHOR_STYLE}
    >
      <Pressable
        accessibilityRole="link"
        onPress={onPress}
        onHoverIn={handleHoverIn}
        onHoverOut={handleHoverOut}
      >
        <Text dataSet={monoSurface ? CODE_SURFACE_DATASET : undefined} style={hoveredTextStyle}>
          {children}
        </Text>
      </Pressable>
    </a>
  );

  return <FileLinkHoverTooltip filePath={tooltipPath}>{anchor}</FileLinkHoverTooltip>;
}

interface AssistantMarkdownCodeLinkProps {
  source: AssistantFileLinkSource;
  inheritedStyles: TextStyle;
  codeInlineStyle: TextStyle;
  linkStyle: TextStyle;
  children: ReactNode;
}

export function AssistantMarkdownCodeLink({
  source,
  inheritedStyles,
  codeInlineStyle,
  linkStyle,
  children,
}: AssistantMarkdownCodeLinkProps) {
  const style = useMemo(
    () => [inheritedStyles, codeInlineStyle, linkStyle],
    [inheritedStyles, codeInlineStyle, linkStyle],
  );
  return (
    <AssistantMarkdownLink source={source} style={style} monoSurface>
      {children}
    </AssistantMarkdownLink>
  );
}

function formatInlinePathTargetForTooltip(
  target: { path: string; lineStart?: number; lineEnd?: number },
  workspaceRoot: string | undefined,
): string {
  let result = relativizePathToWorkspace(target.path, workspaceRoot);
  if (target.lineStart) {
    result += `:${target.lineStart}`;
    if (target.lineEnd && target.lineEnd !== target.lineStart) {
      result += `-${target.lineEnd}`;
    }
  }
  return result;
}

function relativizePathToWorkspace(filePath: string, workspaceRoot: string | undefined): string {
  if (!workspaceRoot) {
    return filePath;
  }
  const root = workspaceRoot.replace(/\/+$/, "");
  if (!root) {
    return filePath;
  }
  if (filePath === root) {
    return ".";
  }
  const prefix = `${root}/`;
  if (filePath.startsWith(prefix)) {
    return filePath.slice(prefix.length);
  }
  return filePath;
}

interface AssistantInlineCodePathLinkProps {
  content: string;
  inheritedStyles: TextStyle;
  codeInlineStyle: TextStyle;
  linkStyle: TextStyle;
}

export function AssistantInlineCodePathLink({
  content,
  inheritedStyles,
  codeInlineStyle,
  linkStyle,
}: AssistantInlineCodePathLinkProps) {
  const source = useMemo<AssistantFileLinkSource>(
    () => ({
      href: content,
      text: content,
      sourceType: "inline-code",
    }),
    [content],
  );

  return (
    <AssistantMarkdownCodeLink
      source={source}
      inheritedStyles={inheritedStyles}
      codeInlineStyle={codeInlineStyle}
      linkStyle={linkStyle}
    >
      {content}
    </AssistantMarkdownCodeLink>
  );
}

const FILE_LINK_TOOLTIP_TRIGGER_STYLE: ViewStyle = {
  // RN doesn't type "inline-flex" but RN-web honors it at runtime, which keeps
  // the tooltip wrapper from breaking inline link flow.
  display: "inline-flex" as ViewStyle["display"],
};

const FILE_LINK_TOOLTIP_MOD_KEYS = ["mod"];

function FileLinkHoverTooltip({
  filePath,
  children,
}: {
  filePath: string | null;
  children: ReactNode;
}) {
  if (!isWeb) {
    return children;
  }
  return (
    <Tooltip delayDuration={400}>
      <TooltipTrigger asChild>
        <View style={FILE_LINK_TOOLTIP_TRIGGER_STYLE}>{children}</View>
      </TooltipTrigger>
      {filePath ? (
        <TooltipContent side="top" align="start" maxWidth={520}>
          <View style={styles.tooltipBody}>
            <Text selectable={false} style={styles.tooltipPath}>
              {filePath}
            </Text>
            <View style={styles.tooltipHintRow}>
              <Shortcut keys={FILE_LINK_TOOLTIP_MOD_KEYS} />
              <Text selectable={false} style={styles.tooltipHintText}>
                click for side pane
              </Text>
            </View>
          </View>
        </TooltipContent>
      ) : null}
    </Tooltip>
  );
}

const LINK_ANCHOR_STYLE: CSSProperties = {
  display: "contents",
  color: "inherit",
  textDecoration: "none",
};

function preventAnchorNavigation(event: MouseEvent<HTMLAnchorElement>): void {
  event.preventDefault();
}

function isModifiedOpenEvent(event: MouseEvent<HTMLElement>): boolean {
  return event.metaKey || event.ctrlKey;
}

const styles = StyleSheet.create((theme) => ({
  tooltipBody: {
    gap: theme.spacing[1],
  },
  tooltipPath: {
    color: theme.colors.foreground,
    fontSize: theme.fontSize.xs,
    fontWeight: theme.fontWeight.normal,
  },
  tooltipHintRow: {
    flexDirection: "row",
    alignItems: "center",
    gap: theme.spacing[1],
  },
  tooltipHintText: {
    color: theme.colors.foregroundMuted,
    fontSize: theme.fontSize.xs,
    fontWeight: theme.fontWeight.normal,
  },
}));