codegraph/src/resolution/callback-synthesizer.ts

/**
 * Callback / observer edge synthesis — Phase 1 + 2.
 *
 * Closes dynamic-dispatch holes where a dispatcher invokes callbacks registered
 * elsewhere. Two channel shapes:
 *
 *  (1) Field-backed observer (Phase 1):
 *      onUpdate(cb) { this.callbacks.add(cb); }            // registrar
 *      triggerUpdate() { for (cb of this.callbacks) cb(); } // dispatcher
 *      scene.onUpdate(this.triggerRender)                  // registration
 *      → synthesize triggerUpdate → triggerRender
 *
 *  (2) String-keyed EventEmitter (Phase 2):
 *      this.on('mount', function onmount(){...})           // registration
 *      fn.emit('mount', this)                              // dispatch
 *      → synthesize (method containing emit('mount')) → onmount
 *
 * Whole-graph pass after base resolution. High-precision/low-recall by design:
 * named callbacks only; field channels paired by file+field; EventEmitter
 * channels capped by event fan-out (generic names like 'error' skipped — they
 * need receiver-type matching, deferred to Phase 3). All synthesized edges are
 * tagged `provenance:'heuristic'`. See docs/design/callback-edge-synthesis.md.
 */
import type { Edge, Node } from '../types';
import type { QueryBuilder } from '../db/queries';
import type { ResolutionContext } from './types';
import { isGeneratedFile } from '../extraction/generated-detection';

const REGISTRAR_NAME = /^(on[A-Z]\w*|subscribe|addListener|addEventListener|register|watch|listen|addCallback)$/;
const DISPATCHER_NAME = /(emit|trigger|notify|dispatch|fire|publish|flush)/i;
const MAX_CALLBACKS_PER_CHANNEL = 40;
const EVENT_FANOUT_CAP = 6; // skip events with more handlers/dispatchers than this (too generic without type info)

const ON_RE = /\.(?:on|once|addListener)\(\s*['"]([^'"]+)['"]\s*,\s*(?:function\s+(\w+)|(?:this\.)?(\w+))/g;
const EMIT_RE = /\.(?:emit|fire|dispatchEvent)\(\s*['"]([^'"]+)['"]/g;
const SETSTATE_RE = /this\.setState\s*\(/;
const FLUTTER_SETSTATE_RE = /\bsetState\s*\(/; // Flutter: setState((){…}) / this.setState
const JSX_TAG_RE = /<([A-Z][A-Za-z0-9_]*)[\s/>]/g;
const MAX_JSX_CHILDREN = 30;
// Vue SFC templates: kebab-case child components (<el-button> → ElButton) and
// event bindings (@click="fn" / v-on:click="fn"). PascalCase children (<VPNav/>)
// are already caught by JSX_TAG_RE via the SFC component node.
const VUE_KEBAB_RE = /<([a-z][a-z0-9]*(?:-[a-z0-9]+)+)[\s/>]/g;
const VUE_HANDLER_RE = /(?:@|v-on:)([a-zA-Z][\w-]*)(?:\.[\w]+)*\s*=\s*"([^"]+)"/g;
// Composable/hook destructure: `const { close: closeSidebar } = useSidebarControl()`.
// Captures the destructure body + the called composable; only `use*` calls qualify.
const VUE_DESTRUCTURE_RE = /(?:const|let|var)\s*\{([^}]+)\}\s*=\s*(\w+)\s*\(/g;

function kebabToPascal(s: string): string {
  return s.split('-').map((p) => p.charAt(0).toUpperCase() + p.slice(1)).join('');
}

function sliceLines(content: string, startLine?: number, endLine?: number): string | null {
  if (!startLine || !endLine) return null;
  return content.split('\n').slice(startLine - 1, endLine).join('\n');
}

function registrarField(src: string): string | null {
  const m = src.match(/this\.(\w+)\.(?:add|push|set)\(/);
  return m ? m[1]! : null;
}

function dispatcherField(src: string): string | null {
  const forOf = src.match(/\bof\s+(?:Array\.from\(\s*)?this\.(\w+)/);
  if (forOf && /\b\w+\s*\(/.test(src)) return forOf[1]!;
  const forEach = src.match(/this\.(\w+)\.forEach\(/);
  if (forEach) return forEach[1]!;
  return null;
}

const FN_KINDS = new Set(['method', 'function', 'component']);

/** Innermost function/method node whose line range contains `line`. */
function enclosingFn(nodesInFile: Node[], line: number): Node | null {
  let best: Node | null = null;
  for (const n of nodesInFile) {
    if (!FN_KINDS.has(n.kind)) continue;
    const end = n.endLine ?? n.startLine;
    if (n.startLine <= line && end >= line) {
      if (!best || n.startLine >= best.startLine) best = n; // prefer the tightest (latest-starting) encloser
    }
  }
  return best;
}

/** Phase 1: field-backed observer channels (registrar/dispatcher share a store). */
function fieldChannelEdges(queries: QueryBuilder, ctx: ResolutionContext): Edge[] {
  const candidates = [...queries.getNodesByKind('method'), ...queries.getNodesByKind('function')];
  const registrars: Array<{ node: Node; field: string }> = [];
  const dispatchers: Array<{ node: Node; field: string }> = [];

  for (const m of candidates) {
    const isReg = REGISTRAR_NAME.test(m.name);
    const isDisp = DISPATCHER_NAME.test(m.name);
    if (!isReg && !isDisp) continue;
    const content = ctx.readFile(m.filePath);
    const src = content && sliceLines(content, m.startLine, m.endLine);
    if (!src) continue;
    if (isReg) { const f = registrarField(src); if (f) registrars.push({ node: m, field: f }); }
    if (isDisp) { const f = dispatcherField(src); if (f) dispatchers.push({ node: m, field: f }); }
  }

  const edges: Edge[] = [];
  const seen = new Set<string>();
  for (const reg of registrars) {
    const chDispatchers = dispatchers.filter(
      (d) => d.node.filePath === reg.node.filePath && d.field === reg.field
    );
    if (chDispatchers.length === 0) continue;
    const argRe = new RegExp(`${reg.node.name}\\s*\\(\\s*(?:this\\.)?(\\w+)`);
    let added = 0;
    for (const e of queries.getIncomingEdges(reg.node.id, ['calls'])) {
      if (added >= MAX_CALLBACKS_PER_CHANNEL) break;
      if (!e.line) continue;
      const caller = queries.getNodeById(e.source);
      if (!caller) continue;
      const line = ctx.readFile(caller.filePath)?.split('\n')[e.line - 1];
      const am = line?.match(argRe);
      if (!am) continue;
      const fn = ctx.getNodesByName(am[1]!).find((n) => n.kind === 'method' || n.kind === 'function');
      if (!fn) continue;
      for (const disp of chDispatchers) {
        if (disp.node.id === fn.id) continue;
        const key = `${disp.node.id}>${fn.id}`;
        if (seen.has(key)) continue;
        seen.add(key);
        edges.push({
          source: disp.node.id, target: fn.id, kind: 'calls', line: disp.node.startLine,
          provenance: 'heuristic',
          metadata: {
            synthesizedBy: 'callback', via: reg.node.name, field: reg.field,
            // Where the callback was wired up (`scene.onUpdate(this.triggerRender)`).
            // This is the #1 thing an agent reads/greps to explain the flow — surface
            // it so node/trace/context can show it without a callers() + Read round-trip.
            registeredAt: `${caller.filePath}:${e.line}`,
          },
        });
        added++;
      }
    }
  }
  return edges;
}

/** Phase 2: string-keyed EventEmitter channels (on('e', fn) ↔ emit('e')). */
function eventEmitterEdges(ctx: ResolutionContext): Edge[] {
  const emitsByEvent = new Map<string, Set<string>>();          // event → dispatcher node ids
  const handlersByEvent = new Map<string, Map<string, string>>(); // event → handler id → registration site (file:line)

  for (const file of ctx.getAllFiles()) {
    const content = ctx.readFile(file);
    if (!content) continue;
    const hasEmit = content.includes('.emit(') || content.includes('.fire(') || content.includes('.dispatchEvent(');
    const hasOn = content.includes('.on(') || content.includes('.once(') || content.includes('.addListener(');
    if (!hasEmit && !hasOn) continue;
    const nodesInFile = ctx.getNodesInFile(file);
    const lineOf = (idx: number) => content.slice(0, idx).split('\n').length;

    if (hasEmit) {
      EMIT_RE.lastIndex = 0;
      let m: RegExpExecArray | null;
      while ((m = EMIT_RE.exec(content))) {
        const disp = enclosingFn(nodesInFile, lineOf(m.index));
        if (!disp) continue;
        const set = emitsByEvent.get(m[1]!) ?? new Set<string>();
        set.add(disp.id); emitsByEvent.set(m[1]!, set);
      }
    }
    if (hasOn) {
      ON_RE.lastIndex = 0;
      let m: RegExpExecArray | null;
      while ((m = ON_RE.exec(content))) {
        const handlerName = m[2] || m[3];
        if (!handlerName) continue;
        const handler = ctx.getNodesByName(handlerName).find((n) => n.kind === 'function' || n.kind === 'method');
        if (!handler) continue;
        const map = handlersByEvent.get(m[1]!) ?? new Map<string, string>();
        map.set(handler.id, `${file}:${lineOf(m.index)}`); handlersByEvent.set(m[1]!, map);
      }
    }
  }

  const edges: Edge[] = [];
  const seen = new Set<string>();
  for (const [event, dispatchers] of emitsByEvent) {
    const handlers = handlersByEvent.get(event);
    if (!handlers) continue;
    // Precision guard: a generic event name with many handlers/dispatchers can't
    // be matched without receiver-type info (Phase 3) — skip rather than over-link.
    if (dispatchers.size > EVENT_FANOUT_CAP || handlers.size > EVENT_FANOUT_CAP) continue;
    for (const d of dispatchers) for (const [h, registeredAt] of handlers) {
      if (d === h) continue;
      const key = `${d}>${h}`;
      if (seen.has(key)) continue;
      seen.add(key);
      edges.push({ source: d, target: h, kind: 'calls', provenance: 'heuristic', metadata: { synthesizedBy: 'event-emitter', event, registeredAt } });
    }
  }
  return edges;
}

/**
 * Phase 4: React class-component re-render. `this.setState(...)` re-runs the
 * component's `render()`, but that hop is React-internal — no static edge — so a
 * flow like "mutation → setState → canvas repaint" dead-ends at setState even
 * though `render → getRenderableElements → …` is fully call-connected after it.
 * Bridge it: for each class that has a `render` method, link every sibling method
 * whose body calls `this.setState(` → `render`. The setState gate keeps this to
 * React class components (a non-React class with a `render` method won't call
 * `this.setState`). Over-approximation (all setState methods reach render) is
 * accepted — it's reachability-correct, like the callback channels.
 */
function reactRenderEdges(queries: QueryBuilder, ctx: ResolutionContext): Edge[] {
  const edges: Edge[] = [];
  const seen = new Set<string>();
  for (const cls of queries.getNodesByKind('class')) {
    const children = queries.getOutgoingEdges(cls.id, ['contains'])
      .map((e) => queries.getNodeById(e.target))
      .filter((n): n is Node => !!n && n.kind === 'method');
    const render = children.find((n) => n.name === 'render');
    if (!render) continue;
    let added = 0;
    for (const m of children) {
      if (added >= MAX_CALLBACKS_PER_CHANNEL) break;
      if (m.id === render.id) continue;
      const content = ctx.readFile(m.filePath);
      const src = content && sliceLines(content, m.startLine, m.endLine);
      if (!src || !SETSTATE_RE.test(src)) continue;
      const key = `${m.id}>${render.id}`;
      if (seen.has(key)) continue;
      seen.add(key);
      edges.push({
        source: m.id, target: render.id, kind: 'calls', line: m.startLine,
        provenance: 'heuristic',
        metadata: { synthesizedBy: 'react-render', via: 'setState', registeredAt: `${render.filePath}:${render.startLine}` },
      });
      added++;
    }
  }
  return edges;
}

/**
 * Phase 4b: Flutter setState → build (the Dart analog of react-render). In a
 * StatefulWidget's State class, `setState(() {…})` re-runs `build(context)`, but
 * that hop is framework-internal (Flutter calls build), so a flow like
 * "onPressed → _increment → setState → rebuilt UI" dead-ends at setState. Bridge
 * it: for each Dart class with a `build` method, link every sibling method whose
 * body calls `setState(` → `build`. The setState gate + `.dart` file keep this to
 * Flutter State classes. Over-approximation accepted (reachability-correct).
 */
function flutterBuildEdges(queries: QueryBuilder, ctx: ResolutionContext): Edge[] {
  const edges: Edge[] = [];
  const seen = new Set<string>();
  for (const cls of queries.getNodesByKind('class')) {
    const children = queries.getOutgoingEdges(cls.id, ['contains'])
      .map((e) => queries.getNodeById(e.target))
      .filter((n): n is Node => !!n && n.kind === 'method');
    const build = children.find((n) => n.name === 'build');
    if (!build || !build.filePath.endsWith('.dart')) continue;
    let added = 0;
    for (const m of children) {
      if (added >= MAX_CALLBACKS_PER_CHANNEL) break;
      if (m.id === build.id) continue;
      const content = ctx.readFile(m.filePath);
      const src = content && sliceLines(content, m.startLine, m.endLine);
      if (!src || !FLUTTER_SETSTATE_RE.test(src)) continue;
      const key = `${m.id}>${build.id}`;
      if (seen.has(key)) continue;
      seen.add(key);
      edges.push({
        source: m.id, target: build.id, kind: 'calls', line: m.startLine,
        provenance: 'heuristic',
        metadata: { synthesizedBy: 'flutter-build', via: 'setState', registeredAt: `${build.filePath}:${build.startLine}` },
      });
      added++;
    }
  }
  return edges;
}

/**
 * Phase 4c: C++ virtual override. A call through a base/interface pointer
 * (`db->Get(...)`, `iter->Next()`) dispatches at runtime to a subclass override,
 * but that hop is a vtable indirection — no static call edge — so a flow stops at
 * the abstract base method. Bridge it like react-render: for each C++ class that
 * `extends` a base, link each base method → the subclass method of the same name
 * (the override), so trace/callees from the interface method reach the
 * implementation(s). Over-approximation accepted (reachability-correct); capped
 * per class and gated to C++ to avoid touching other languages' dispatch.
 */
function cppOverrideEdges(queries: QueryBuilder): Edge[] {
  const edges: Edge[] = [];
  const seen = new Set<string>();
  const methodsOf = (classId: string): Node[] =>
    queries
      .getOutgoingEdges(classId, ['contains'])
      .map((e) => queries.getNodeById(e.target))
      .filter((n): n is Node => !!n && n.kind === 'method');
  for (const cls of queries.getNodesByKind('class')) {
    const subMethods = methodsOf(cls.id).filter((n) => n.language === 'cpp');
    if (subMethods.length === 0) continue;
    for (const ext of queries.getOutgoingEdges(cls.id, ['extends'])) {
      const base = queries.getNodeById(ext.target);
      if (!base || base.language !== 'cpp' || base.id === cls.id) continue;
      const baseMethods = new Map(methodsOf(base.id).map((m) => [m.name, m]));
      let added = 0;
      for (const m of subMethods) {
        if (added >= MAX_CALLBACKS_PER_CHANNEL) break;
        const bm = baseMethods.get(m.name);
        if (!bm || bm.id === m.id) continue;
        const key = `${bm.id}>${m.id}`;
        if (seen.has(key)) continue;
        seen.add(key);
        edges.push({
          source: bm.id,
          target: m.id,
          kind: 'calls',
          line: bm.startLine,
          provenance: 'heuristic',
          metadata: { synthesizedBy: 'cpp-override', via: m.name, registeredAt: `${m.filePath}:${m.startLine}` },
        });
        added++;
      }
    }
  }
  return edges;
}

/**
 * Phase 5.5: interface / abstract dispatch (Java, Kotlin). A call through an
 * injected interface (`@Autowired FooService svc; svc.list()`) or an abstract
 * base dispatches at runtime to the implementing class's override — a vtable
 * indirection with no static call edge — so a request→service flow stops at the
 * interface method. Bridge it like cpp-override: for each class that
 * `implements` an interface (or `extends` an abstract base), link each
 * base/interface method → the class's same-name method (the override) so
 * trace/callees reach the implementation. Over-approximation accepted
 * (reachability-correct); capped per class, gated to JVM languages.
 */
const IFACE_OVERRIDE_LANGS = new Set(['java', 'kotlin']);
function interfaceOverrideEdges(queries: QueryBuilder): Edge[] {
  const edges: Edge[] = [];
  const seen = new Set<string>();
  const methodsOf = (classId: string): Node[] =>
    queries
      .getOutgoingEdges(classId, ['contains'])
      .map((e) => queries.getNodeById(e.target))
      .filter((n): n is Node => !!n && n.kind === 'method');
  for (const cls of queries.getNodesByKind('class')) {
    const implMethods = methodsOf(cls.id).filter((n) => IFACE_OVERRIDE_LANGS.has(n.language));
    if (implMethods.length === 0) continue;
    for (const sup of queries.getOutgoingEdges(cls.id, ['implements', 'extends'])) {
      const base = queries.getNodeById(sup.target);
      if (!base || !IFACE_OVERRIDE_LANGS.has(base.language) || base.id === cls.id) continue;
      // Group impl methods by name to handle OVERLOADS: an interface `list()` and
      // `list(params)` are distinct nodes and a call may resolve to either, so
      // link every base overload → every same-name impl overload (keying by name
      // alone would drop all but one and miss the resolved overload).
      const implByName = new Map<string, Node[]>();
      for (const m of implMethods) {
        const arr = implByName.get(m.name);
        if (arr) arr.push(m); else implByName.set(m.name, [m]);
      }
      let added = 0;
      for (const bm of methodsOf(base.id)) {
        if (added >= MAX_CALLBACKS_PER_CHANNEL) break;
        for (const m of implByName.get(bm.name) ?? []) {
          if (added >= MAX_CALLBACKS_PER_CHANNEL) break;
          if (bm.id === m.id) continue;
          const key = `${bm.id}>${m.id}`;
          if (seen.has(key)) continue;
          seen.add(key);
          edges.push({
            source: bm.id,
            target: m.id,
            kind: 'calls',
            line: bm.startLine,
            provenance: 'heuristic',
            metadata: { synthesizedBy: 'interface-impl', via: m.name, registeredAt: `${m.filePath}:${m.startLine}` },
          });
          added++;
        }
      }
    }
  }
  return edges;
}

/**
 * Go gRPC stub → impl bridge. The protoc-gen-go-grpc codegen emits an
 * `UnimplementedXxxServer` struct in `*_grpc.pb.go` carrying one method
 * per service RPC; the real handler is a hand-written struct in another
 * file (`x/bank/keeper/msg_server.go::msgServer.Send` in cosmos-sdk).
 * Go's structural typing means no `implements` edge exists for our
 * resolver to follow, so `trace("Send","SendCoins")` lands on the
 * empty stub and reports "no path" (validated empirically — the cosmos
 * Q1 r1 trace failure that drove this work).
 *
 * Bridge: for each `UnimplementedXxxServer` whose RPC-method names are
 * a SUBSET of some other Go struct's method names, emit `calls` edges
 * `stub.method → impl.method` (paired by name). Excludes the gRPC
 * internal markers `mustEmbedUnimplementedXxxServer` and
 * `testEmbeddedByValue`, and skips candidate impls that themselves
 * live in a generated file (their `xxxClient` / sibling stubs would
 * otherwise look like impls).
 *
 * Multiple candidates is allowed and capped at MAX_CALLBACKS_PER_CHANNEL —
 * a service often has both a production impl and one or more test
 * mocks; linking to all preserves trace utility without false-favoring.
 *
 * Provenance: `heuristic`, `synthesizedBy: 'go-grpc-stub-impl'`. The
 * stub's source line is the wiring site shown in the trace trail.
 */
function goGrpcStubImplEdges(queries: QueryBuilder): Edge[] {
  const edges: Edge[] = [];
  const seen = new Set<string>();

  const STUB_RE = /^Unimplemented.*Server$/;
  // gRPC internal-helper methods that appear on every Unimplemented*Server;
  // not part of the service contract, so exclude when computing the RPC-method
  // signature used to match impls.
  const isInternalMarker = (n: string) => n.startsWith('mustEmbed') || n === 'testEmbeddedByValue';

  // Methods directly contained by each Go struct, name-only. Built once.
  const methodNamesByStruct = new Map<string, Set<string>>();
  const methodNodesByStruct = new Map<string, Node[]>();
  const goStructs: Node[] = [];
  for (const s of queries.getNodesByKind('struct')) {
    if (s.language !== 'go') continue;
    goStructs.push(s);
    const ms = queries
      .getOutgoingEdges(s.id, ['contains'])
      .map((e) => queries.getNodeById(e.target))
      .filter((n): n is Node => !!n && n.kind === 'method');
    methodNodesByStruct.set(s.id, ms);
    methodNamesByStruct.set(s.id, new Set(ms.map((m) => m.name)));
  }

  for (const stub of goStructs) {
    if (!STUB_RE.test(stub.name)) continue;
    // The stub MUST live in a generated file — that's what tells us this is
    // a protoc-emitted scaffold rather than someone naming a struct
    // `UnimplementedXxxServer` by hand. Without this gate we'd also bridge
    // such hand-written structs and create misleading edges.
    if (!isGeneratedFile(stub.filePath)) continue;

    const stubMethods = (methodNodesByStruct.get(stub.id) ?? []).filter(
      (m) => !isInternalMarker(m.name),
    );
    if (stubMethods.length === 0) continue;
    const stubMethodNames = stubMethods.map((m) => m.name);

    for (const cand of goStructs) {
      if (cand.id === stub.id) continue;
      // Skip generated-file candidates — they're siblings (msgClient,
      // UnsafeMsgServer, …) whose method sets coincidentally match.
      if (isGeneratedFile(cand.filePath)) continue;

      const candNames = methodNamesByStruct.get(cand.id);
      if (!candNames) continue;
      // Subset: every RPC method must exist on the candidate by name.
      // Signature-level match would tighten this further, but name-match
      // alone already gives one-to-one pairing in real codebases because
      // gRPC method-name sets are highly distinctive (Send + MultiSend +
      // UpdateParams + SetSendEnabled is unique to bank's MsgServer).
      if (!stubMethodNames.every((n) => candNames.has(n))) continue;

      const candMethods = methodNodesByStruct.get(cand.id) ?? [];
      let added = 0;
      for (const sm of stubMethods) {
        if (added >= MAX_CALLBACKS_PER_CHANNEL) break;
        for (const cm of candMethods) {
          if (added >= MAX_CALLBACKS_PER_CHANNEL) break;
          if (cm.name !== sm.name) continue;
          const key = `${sm.id}>${cm.id}`;
          if (seen.has(key)) continue;
          seen.add(key);
          edges.push({
            source: sm.id,
            target: cm.id,
            kind: 'calls',
            line: sm.startLine,
            provenance: 'heuristic',
            metadata: {
              synthesizedBy: 'go-grpc-stub-impl',
              via: cm.name,
              registeredAt: `${cm.filePath}:${cm.startLine}`,
            },
          });
          added++;
        }
      }
    }
  }
  return edges;
}

/**
 * Phase 5: React JSX child rendering. A component that returns `<Child .../>`
 * mounts Child — React calls it — but JSX instantiation isn't a static call edge,
 * so a render tree (App.render → StaticCanvas → renderStaticScene) breaks at the
 * JSX hop. Link parent → each capitalized JSX child it renders. File-oriented
 * (read each JSX file once). Precision gate: the child name must resolve to a
 * component/function/class node — TS generics like `Array<Foo>` resolve to a type
 * (or nothing) and are dropped.
 */
function reactJsxChildEdges(ctx: ResolutionContext): Edge[] {
  const edges: Edge[] = [];
  const seen = new Set<string>();
  const PARENT_KINDS = new Set(['method', 'function', 'component']);
  for (const file of ctx.getAllFiles()) {
    const content = ctx.readFile(file);
    if (!content || (!content.includes('</') && !content.includes('/>'))) continue; // JSX-file gate
    const parents = ctx.getNodesInFile(file).filter((n) => PARENT_KINDS.has(n.kind));
    for (const parent of parents) {
      const src = sliceLines(content, parent.startLine, parent.endLine);
      if (!src || (!src.includes('</') && !src.includes('/>'))) continue;
      const names = new Set<string>();
      JSX_TAG_RE.lastIndex = 0;
      let m: RegExpExecArray | null;
      while ((m = JSX_TAG_RE.exec(src))) names.add(m[1]!);
      let added = 0;
      for (const name of names) {
        if (added >= MAX_JSX_CHILDREN) break;
        const child = ctx.getNodesByName(name).find(
          (n) => n.kind === 'component' || n.kind === 'function' || n.kind === 'class'
        );
        if (!child || child.id === parent.id) continue;
        const key = `${parent.id}>${child.id}`;
        if (seen.has(key)) continue;
        seen.add(key);
        edges.push({
          source: parent.id, target: child.id, kind: 'calls', line: parent.startLine,
          provenance: 'heuristic',
          metadata: { synthesizedBy: 'jsx-render', via: name },
        });
        added++;
      }
    }
  }
  return edges;
}

/**
 * Phase 6: Vue SFC templates. The `.vue` extractor only parses `<script>`, so
 * template usage is invisible — child components and event handlers used ONLY in
 * the template have no edge to them. PascalCase children (`<VPNav/>`) are already
 * caught by reactJsxChildEdges (which scans the SFC component node), so this adds
 * the two Vue-specific shapes:
 *   - kebab-case children: `<el-button>` → `ElButton` component (renders).
 *   - event bindings: `@click="onClick"` / `v-on:submit="save"` → handler method.
 * Scoped to the `<template>` block of `.vue` files; resolution gate (kebab→
 * component, handler→function/method) keeps precision; inline arrows / `$emit`
 * skipped.
 */
function vueTemplateEdges(ctx: ResolutionContext): Edge[] {
  const edges: Edge[] = [];
  const seen = new Set<string>();
  const COMPONENT_KINDS = new Set(['component', 'function', 'class']);
  const HANDLER_KINDS = new Set(['method', 'function']);
  // A composable's returned member may be a fn (`function close(){}`) or an
  // arrow assigned to a const (`const close = () => {}`).
  const RETURN_KINDS = new Set(['method', 'function', 'variable', 'constant']);
  for (const file of ctx.getAllFiles()) {
    if (!file.endsWith('.vue')) continue;
    const content = ctx.readFile(file);
    const tpl = content && content.match(/<template[^>]*>([\s\S]*)<\/template>/i)?.[1];
    if (!tpl) continue;
    const comp = ctx.getNodesInFile(file).find((n) => n.kind === 'component');
    if (!comp) continue;

    // Composable-destructure map: alias → { composable, key }. Lets us resolve a
    // template handler that isn't a local function but a destructured composable
    // return (`@click="closeSidebar"` ← `const { close: closeSidebar } = useSidebarControl()`).
    const script = content.match(/<script[^>]*>([\s\S]*?)<\/script>/i)?.[1] ?? '';
    const destructured = new Map<string, { composable: string; key: string }>();
    VUE_DESTRUCTURE_RE.lastIndex = 0;
    let dm: RegExpExecArray | null;
    while ((dm = VUE_DESTRUCTURE_RE.exec(script))) {
      if (!/^use[A-Z]/.test(dm[2]!)) continue; // composables / hooks only
      for (const part of dm[1]!.split(',')) {
        const pm = part.trim().match(/^(\w+)\s*(?::\s*(\w+))?$/); // key | key: alias
        if (pm) destructured.set(pm[2] || pm[1]!, { composable: dm[2]!, key: pm[1]! });
      }
    }

    let added = 0;
    const addEdge = (target: Node | undefined, meta: Record<string, unknown>) => {
      if (added >= MAX_JSX_CHILDREN || !target || target.id === comp.id) return;
      const k = `${comp.id}>${target.id}>${meta.synthesizedBy}`;
      if (seen.has(k)) return;
      seen.add(k);
      edges.push({ source: comp.id, target: target.id, kind: 'calls', line: comp.startLine, provenance: 'heuristic', metadata: meta });
      added++;
    };
    // Prefer a target in THIS SFC (handlers live in the same file's script) —
    // avoids cross-file mis-match when a name repeats across a monorepo.
    const resolve = (name: string, kinds: Set<string>): Node | undefined => {
      const matches = ctx.getNodesByName(name).filter((n) => kinds.has(n.kind));
      return matches.find((n) => n.filePath === file) ?? matches[0];
    };

    let m: RegExpExecArray | null;
    VUE_KEBAB_RE.lastIndex = 0;
    while ((m = VUE_KEBAB_RE.exec(tpl))) addEdge(resolve(kebabToPascal(m[1]!), COMPONENT_KINDS), { synthesizedBy: 'jsx-render', via: m[1] });
    VUE_HANDLER_RE.lastIndex = 0;
    while ((m = VUE_HANDLER_RE.exec(tpl))) {
      const event = m[1]!;
      const expr = m[2]!.trim();
      if (expr.includes('=>') || expr.startsWith('$')) continue; // inline arrow / $emit
      const name = expr.match(/^([A-Za-z_]\w*)/)?.[1];
      if (!name) continue;
      const direct = resolve(name, HANDLER_KINDS);
      if (direct) { addEdge(direct, { synthesizedBy: 'vue-handler', event }); continue; }
      // Composable-destructure handler → resolve to the composable's returned fn.
      const d = destructured.get(name);
      if (!d) continue;
      const composable = resolve(d.composable, HANDLER_KINDS);
      // Resolve to the SPECIFIC returned member (e.g. `close`) defined in the
      // composable's file. No fallback to the composable itself — the component
      // already has a static `useX()` call edge, so that would just be redundant
      // and less precise.
      const keyFn = composable
        ? ctx.getNodesByName(d.key).find((n) => RETURN_KINDS.has(n.kind) && n.filePath === composable.filePath)
        : undefined;
      if (keyFn) addEdge(keyFn, { synthesizedBy: 'vue-handler', event, via: d.composable });
    }
  }
  return edges;
}

/**
 * React Native cross-language event channel (Phase 3 of the mixed-iOS/RN
 * bridging effort). Same shape as `eventEmitterEdges` but cross-language:
 *
 *   Native (ObjC, on RCTEventEmitter subclass):
 *     [self sendEventWithName:@"locationUpdate" body:@{...}];
 *
 *   Native (Java/Kotlin, via the JS module dispatcher):
 *     emitter.emit("locationUpdate", body);
 *     reactContext.getJSModule(RCTDeviceEventEmitter.class).emit("locationUpdate", body);
 *
 *   JS (subscriber):
 *     new NativeEventEmitter(NativeModules.Geo).addListener("locationUpdate", handler);
 *     DeviceEventEmitter.addListener("locationUpdate", handler);
 *
 * Synthesize: native dispatch site → JS handler, keyed by the literal
 * event name. Only matches NAMED handlers (the existing `ON_RE` named-
 * capture form). Inline arrow handlers like `addListener('x', d => …)`
 * aren't named at extraction time and would need link-through-body
 * support; matches the deliberate scope of the in-language synthesizer.
 *
 * Provenance `'heuristic'`, synthesizedBy `'rn-event-channel'`.
 */
// ObjC's `[self sendEventWithName:@"X" body:...]` shape (bracket syntax,
// `@` string literals).
const RN_OBJC_SEND_RE = /\bsendEventWithName\s*:\s*@"([^"]+)"/g;
// Swift's `sendEvent(withName: "X", body: ...)` shape — same RCTEventEmitter
// method, different call syntax. Both Objective-C and Swift subclass
// RCTEventEmitter so this catches the Swift-side equivalent emission sites
// (e.g. RNFusedLocation.swift's `sendEvent(withName: "geolocationDidChange",
// body: locationData)`).
const RN_SWIFT_SEND_RE = /\bsendEvent\s*\(\s*withName\s*:\s*"([^"]+)"/g;
// JVM-side emitter calls: `emitter.emit("X", body)`. Matches both Java
// and Kotlin syntax because the call form is identical. Restricted to
// JVM source files in the consumer so we don't re-process JS emits
// (which `eventEmitterEdges` already handles).
const RN_JVM_EMIT_RE = /\.emit\s*\(\s*"([^"]+)"\s*,/g;

function rnEventEdges(ctx: ResolutionContext): Edge[] {
  // Native dispatchers (source = the native method whose body sends the
  // event) and JS handlers (target = the function/method registered as
  // the listener) keyed by event name.
  const nativeDispatchersByEvent = new Map<string, Set<string>>();
  const jsHandlersByEvent = new Map<string, Map<string, string>>();

  for (const file of ctx.getAllFiles()) {
    const content = ctx.readFile(file);
    if (!content) continue;

    const nodesInFile = ctx.getNodesInFile(file);
    const lineOf = (idx: number) => content.slice(0, idx).split('\n').length;
    const addDispatcher = (event: string, line: number) => {
      const disp = enclosingFn(nodesInFile, line);
      if (!disp) return;
      const set = nativeDispatchersByEvent.get(event) ?? new Set<string>();
      set.add(disp.id);
      nativeDispatchersByEvent.set(event, set);
    };

    // ObjC side: `sendEventWithName:@"X"` only fires inside `.m`/`.mm`
    // files (RCTEventEmitter subclasses).
    if (file.endsWith('.m') || file.endsWith('.mm')) {
      RN_OBJC_SEND_RE.lastIndex = 0;
      let m: RegExpExecArray | null;
      while ((m = RN_OBJC_SEND_RE.exec(content))) {
        if (m[1]) addDispatcher(m[1], lineOf(m.index));
      }
    }

    // Swift side: same RCTEventEmitter method, parens/named-args syntax.
    if (file.endsWith('.swift')) {
      RN_SWIFT_SEND_RE.lastIndex = 0;
      let m: RegExpExecArray | null;
      while ((m = RN_SWIFT_SEND_RE.exec(content))) {
        if (m[1]) addDispatcher(m[1], lineOf(m.index));
      }
    }

    // JVM side: `.emit("X", …)` in Java/Kotlin. (We pattern-match
    // anywhere in the file; the JS in-language path uses a separate
    // emitter object pattern and is already handled by eventEmitterEdges.)
    if (file.endsWith('.java') || file.endsWith('.kt')) {
      RN_JVM_EMIT_RE.lastIndex = 0;
      let m: RegExpExecArray | null;
      while ((m = RN_JVM_EMIT_RE.exec(content))) {
        if (m[1]) addDispatcher(m[1], lineOf(m.index));
      }
    }

    // JS subscribers (.addListener("X", handler)). Restrict to JS-family
    // files so a native file's `addListener:` (the ObjC method) doesn't
    // get mistaken for a JS subscription — they're entirely different
    // things despite sharing a name.
    if (
      file.endsWith('.js') ||
      file.endsWith('.jsx') ||
      file.endsWith('.ts') ||
      file.endsWith('.tsx') ||
      file.endsWith('.mjs') ||
      file.endsWith('.cjs')
    ) {
      // Match BOTH the named-handler form (`.addListener('x', fn)`) and
      // an unnamed-handler form (`.addListener('x', listener)` where
      // `listener` is a parameter — common in RN wrapper APIs like
      // RNFirebase's `messaging().onMessageReceived(listener)`). For the
      // unnamed case we attribute the subscription to the ENCLOSING JS
      // function (the abstraction layer), giving a reachability-correct
      // hop even when the actual user-side handler lives one call up.
      const ADDLISTENER_ANY = /\.(?:on|once|addListener)\(\s*['"]([^'"]+)['"]\s*,\s*([A-Za-z_][\w.]*)/g;
      ADDLISTENER_ANY.lastIndex = 0;
      let m: RegExpExecArray | null;
      while ((m = ADDLISTENER_ANY.exec(content))) {
        const event = m[1];
        const arg = m[2];
        if (!event || !arg) continue;
        const bareName = arg.includes('.') ? arg.slice(arg.lastIndexOf('.') + 1) : arg;
        // Try a named-symbol match first (matches the in-language semantic).
        const namedHandler = ctx
          .getNodesByName(bareName)
          .find((n) => n.kind === 'function' || n.kind === 'method');
        let targetId: string | null = namedHandler?.id ?? null;
        if (!targetId) {
          // Fall back to the enclosing function — the subscribe-wrapper
          // pattern means the event fires THROUGH this function on its
          // way to user code. Reachability-correct attribution.
          const enclosing = enclosingFn(nodesInFile, lineOf(m.index));
          targetId = enclosing?.id ?? null;
        }
        if (!targetId) {
          // Broader fallback for JS object-literal API shape
          // (`const Foo = { watchX(...) { … addListener(...) … } }`):
          // method shorthand inside an object literal isn't extracted
          // as a method node, so enclosingFn returns null. Attribute to
          // the smallest enclosing `constant` / `variable` node — that's
          // the API surface a downstream caller would `import` and
          // invoke. Reachability-correct.
          const line = lineOf(m.index);
          let smallest: typeof nodesInFile[number] | null = null;
          for (const n of nodesInFile) {
            if (n.kind !== 'constant' && n.kind !== 'variable') continue;
            const end = n.endLine ?? n.startLine;
            if (n.startLine <= line && end >= line) {
              if (!smallest || n.startLine >= smallest.startLine) smallest = n;
            }
          }
          targetId = smallest?.id ?? null;
        }
        if (!targetId) continue;
        const map = jsHandlersByEvent.get(event) ?? new Map<string, string>();
        map.set(targetId, `${file}:${lineOf(m.index)}`);
        jsHandlersByEvent.set(event, map);
      }
    }
  }

  const edges: Edge[] = [];
  const seen = new Set<string>();
  for (const [event, dispatchers] of nativeDispatchersByEvent) {
    const handlers = jsHandlersByEvent.get(event);
    if (!handlers) continue;
    // Same fan-out guard as the in-language channel: generic event names
    // (e.g. 'change', 'error', 'data') with many handlers/dispatchers
    // can't be matched precisely without receiver-type info.
    if (dispatchers.size > EVENT_FANOUT_CAP || handlers.size > EVENT_FANOUT_CAP) continue;
    for (const d of dispatchers) {
      for (const [h, registeredAt] of handlers) {
        if (d === h) continue;
        const key = `${d}>${h}`;
        if (seen.has(key)) continue;
        seen.add(key);
        edges.push({
          source: d,
          target: h,
          kind: 'calls',
          provenance: 'heuristic',
          metadata: { synthesizedBy: 'rn-event-channel', event, registeredAt },
        });
      }
    }
  }
  return edges;
}

/**
 * Phase 6 — React Native Fabric/Codegen view component bridge.
 *
 * The Fabric framework extractor (`frameworks/fabric.ts`) emits
 * `component` nodes named after the JS-visible component (e.g.
 * `RNSScreenStack`) from each `codegenNativeComponent<Props>('Name')`
 * spec declaration. The native implementation lives in an ObjC++/.mm or
 * Kotlin/Java class whose name follows one of RN's conventions:
 *
 *   - Exact: `RNSScreenStack`
 *   - With suffix: `RNSScreenStackView`, `RNSScreenStackViewManager`,
 *     `RNSScreenStackComponentView`, `RNSScreenStackManager`
 *
 * This synthesizer walks every Fabric component node and looks for a
 * native class matching one of those names; when found, emits a
 * `calls` edge `component → native class` (provenance `'heuristic'`,
 * `synthesizedBy:'fabric-native-impl'`) so trace from JSX usage of the
 * component continues into native.
 *
 * The convention-based suffix lookup is precise: there's no name
 * collision in RN view-manager codebases by design (Codegen output would
 * conflict otherwise).
 */
const FABRIC_NATIVE_SUFFIXES = ['', 'View', 'ViewManager', 'ComponentView', 'Manager'];

function fabricNativeImplEdges(ctx: ResolutionContext): Edge[] {
  const edges: Edge[] = [];
  const seen = new Set<string>();

  // The Fabric extractor IDs are prefixed `fabric-component:` so we can
  // filter to just those without iterating all `component` nodes.
  const components = ctx.getNodesByKind('component').filter((n) => n.id.startsWith('fabric-component:'));
  if (components.length === 0) return edges;

  // Pre-index native classes by name for O(1) lookup.
  const nativeClassesByName = new Map<string, Node[]>();
  for (const n of ctx.getNodesByKind('class')) {
    if (n.language !== 'objc' && n.language !== 'kotlin' && n.language !== 'java' && n.language !== 'cpp') continue;
    const arr = nativeClassesByName.get(n.name);
    if (arr) arr.push(n);
    else nativeClassesByName.set(n.name, [n]);
  }

  for (const component of components) {
    for (const suffix of FABRIC_NATIVE_SUFFIXES) {
      const candidate = component.name + suffix;
      const matches = nativeClassesByName.get(candidate);
      if (!matches || matches.length === 0) continue;
      // Link the component node to every matching native class (iOS +
      // Android each have one).
      for (const native of matches) {
        const key = `${component.id}>${native.id}`;
        if (seen.has(key)) continue;
        seen.add(key);
        edges.push({
          source: component.id,
          target: native.id,
          kind: 'calls',
          provenance: 'heuristic',
          metadata: {
            synthesizedBy: 'fabric-native-impl',
            viaSuffix: suffix || '(exact)',
            componentName: component.name,
          },
        });
      }
    }
  }

  return edges;
}

/**
 * MyBatis: link a Java mapper interface method to the XML statement that holds
 * its SQL. The XML extractor (`src/extraction/mybatis-extractor.ts`) qualifies
 * each `<select|insert|update|delete|sql id="X">` as `<namespace>::<id>` where
 * `<namespace>` is the Java FQN of the mapper interface. A Java method's
 * qualifiedName ends with `<ClassName>::<methodName>`, so we suffix-match the
 * last two segments of the XML qualified name to find a unique Java method by
 * `<ClassName>::<methodName>` (`ClassName` = last dotted segment of the XML
 * namespace). Cross-mapper `<include refid="other.X">` references go through
 * the normal qualified-name resolver — only the Java↔XML bridge is synthetic.
 *
 * Precision over recall: ambiguous mappers (multiple Java classes with the
 * same simple name) are dropped. We need-not bridge by package because Java
 * mapper interfaces are typically uniquely named within a project.
 */
function mybatisJavaXmlEdges(queries: QueryBuilder): Edge[] {
  const edges: Edge[] = [];
  const seen = new Set<string>();
  // Index Java methods by `<ClassName>::<methodName>` for O(1) lookup.
  const javaIndex = new Map<string, Node[]>();
  for (const m of queries.getNodesByKind('method')) {
    if (m.language !== 'java' && m.language !== 'kotlin') continue;
    const parts = m.qualifiedName.split('::');
    const last = parts[parts.length - 1];
    const cls = parts[parts.length - 2];
    if (!last || !cls) continue;
    const key = `${cls}::${last}`;
    const arr = javaIndex.get(key);
    if (arr) arr.push(m); else javaIndex.set(key, [m]);
  }

  for (const xml of queries.getNodesByKind('method')) {
    if (xml.language !== 'xml') continue;
    // Qualified name: `<namespace>::<id>`. Extract the simple class name.
    const colonIdx = xml.qualifiedName.lastIndexOf('::');
    if (colonIdx < 0) continue;
    const namespace = xml.qualifiedName.slice(0, colonIdx);
    const id = xml.qualifiedName.slice(colonIdx + 2);
    if (!namespace || !id) continue;
    const dotIdx = namespace.lastIndexOf('.');
    const className = dotIdx >= 0 ? namespace.slice(dotIdx + 1) : namespace;
    const candidates = javaIndex.get(`${className}::${id}`);
    if (!candidates || candidates.length === 0) continue;
    // Drop ambiguous matches (multiple same-name classes); the user can
    // disambiguate by adding the package-suffix match in a future enhancement.
    if (candidates.length > 1) continue;
    const java = candidates[0]!;
    const key = `${java.id}>${xml.id}`;
    if (seen.has(key)) continue;
    seen.add(key);
    edges.push({
      source: java.id,
      target: xml.id,
      kind: 'calls',
      line: java.startLine,
      provenance: 'heuristic',
      metadata: {
        synthesizedBy: 'mybatis-java-xml',
        via: `${className}.${id}`,
        registeredAt: `${xml.filePath}:${xml.startLine}`,
      },
    });
  }
  return edges;
}

/**
 * Synthesize dispatcher→callback edges (field observers + EventEmitters +
 * React re-render + JSX children + Vue templates + RN event channel +
 * Fabric native-impl + MyBatis Java↔XML). Returns the count added. Never
 * throws into indexing — callers wrap in try/catch.
 */
export function synthesizeCallbackEdges(queries: QueryBuilder, ctx: ResolutionContext): number {
  const fieldEdges = fieldChannelEdges(queries, ctx);
  const emitterEdges = eventEmitterEdges(ctx);
  const renderEdges = reactRenderEdges(queries, ctx);
  const jsxEdges = reactJsxChildEdges(ctx);
  const vueEdges = vueTemplateEdges(ctx);
  const flutterEdges = flutterBuildEdges(queries, ctx);
  const cppEdges = cppOverrideEdges(queries);
  const ifaceEdges = interfaceOverrideEdges(queries);
  const goGrpcEdges = goGrpcStubImplEdges(queries);
  const rnEventEdgesList = rnEventEdges(ctx);
  const fabricNativeEdges = fabricNativeImplEdges(ctx);
  const mybatisEdges = mybatisJavaXmlEdges(queries);

  const merged: Edge[] = [];
  const seen = new Set<string>();
  for (const e of [
    ...fieldEdges,
    ...emitterEdges,
    ...renderEdges,
    ...jsxEdges,
    ...vueEdges,
    ...flutterEdges,
    ...cppEdges,
    ...ifaceEdges,
    ...goGrpcEdges,
    ...rnEventEdgesList,
    ...fabricNativeEdges,
    ...mybatisEdges,
  ]) {
    const key = `${e.source}>${e.target}`;
    if (seen.has(key)) continue;
    seen.add(key);
    merged.push(e);
  }
  if (merged.length > 0) queries.insertEdges(merged);
  return merged.length;
}