// genCall generates constraints for call instruction instr.
func (a *analysis) genCall(caller *cgnode, instr ssa.CallInstruction) {
	call := instr.Common()

	// Intrinsic implementations of built-in functions.
	if _, ok := call.Value.(*ssa.Builtin); ok {
		a.genBuiltinCall(instr, caller)
		return
	}

	var result nodeid
	if v := instr.Value(); v != nil {
		result = a.valueNode(v)
	}

	site := &callsite{instr: instr}
	if call.StaticCallee() != nil {
		a.genStaticCall(caller, site, call, result)
	} else if call.IsInvoke() {
		a.genInvoke(caller, site, call, result)
	} else {
		a.genDynamicCall(caller, site, call, result)
	}

	caller.sites = append(caller.sites, site)

	if a.log != nil {
		// TODO(adonovan): debug: improve log message.
		fmt.Fprintf(a.log, "\t%s to targets %s from %s\n", site, site.targets, caller)
	}
}

// addEdge adds the specified call graph edge, and marks it reachable.
// addrTaken indicates whether to mark the callee as "address-taken".
func (r *rta) addEdge(site ssa.CallInstruction, callee *ssa.Function, addrTaken bool) {
	r.addReachable(callee, addrTaken)

	if g := r.result.CallGraph; g != nil {
		if site.Parent() == nil {
			panic(site)
		}
		from := g.CreateNode(site.Parent())
		to := g.CreateNode(callee)
		callgraph.AddEdge(from, site, to)
	}
}

// visitInvoke is called each time the algorithm encounters an "invoke"-mode call.
func (r *rta) visitInvoke(site ssa.CallInstruction) {
	I := site.Common().Value.Type().Underlying().(*types.Interface)

	// Record the invoke site.
	sites, _ := r.invokeSites.At(I).([]ssa.CallInstruction)
	r.invokeSites.Set(I, append(sites, site))

	// Add callgraph edge for each existing
	// address-taken concrete type implementing I.
	for _, C := range r.implementations(I) {
		r.addInvokeEdge(site, C)
	}
}

// visitDynCall is called each time we encounter a dynamic "call"-mode call.
func (r *rta) visitDynCall(site ssa.CallInstruction) {
	S := site.Common().Signature()

	// Record the call site.
	sites, _ := r.dynCallSites.At(S).([]ssa.CallInstruction)
	r.dynCallSites.Set(S, append(sites, site))

	// For each function of signature S that we know is address-taken,
	// mark it reachable.  We'll add the callgraph edges later.
	funcs, _ := r.addrTakenFuncsBySig.At(S).(map[*ssa.Function]bool)
	for g := range funcs {
		r.addEdge(site, g, true)
	}
}

// addCallees adds client data and links for the facts that site calls fns.
func (a *analysis) addCallees(site ssa.CallInstruction, fns []*ssa.Function) {
	v := calleesJSON{
		Descr:   site.Common().Description(),
		Callees: []anchorJSON{}, // (JS wants non-nil)
	}
	var this *types.Package // for relativizing names
	if p := site.Parent().Package(); p != nil {
		this = p.Object
	}

	for _, fn := range fns {
		v.Callees = append(v.Callees, anchorJSON{
			Text: prettyFunc(this, fn),
			Href: a.posURL(funcToken(fn), len("func")),
		})
	}

	fi, offset := a.fileAndOffset(site.Common().Pos())
	fi.addLink(aLink{
		start:   offset,
		end:     offset + len("("),
		title:   fmt.Sprintf("%d callees", len(v.Callees)),
		onclick: fmt.Sprintf("onClickCallees(%d)", fi.addData(v)),
	})
}

// genBuiltinCall generates contraints for a call to a built-in.
func (a *analysis) genBuiltinCall(instr ssa.CallInstruction, cgn *cgnode) {
	call := instr.Common()
	switch call.Value.(*ssa.Builtin).Name() {
	case "append":
		// Safe cast: append cannot appear in a go or defer statement.
		a.genAppend(instr.(*ssa.Call), cgn)

	case "copy":
		tElem := call.Args[0].Type().Underlying().(*types.Slice).Elem()
		a.copyElems(cgn, tElem, call.Args[0], call.Args[1])

	case "panic":
		a.copy(a.panicNode, a.valueNode(call.Args[0]), 1)

	case "recover":
		if v := instr.Value(); v != nil {
			a.copy(a.valueNode(v), a.panicNode, 1)
		}

	case "print":
		// In the tests, the probe might be the sole reference
		// to its arg, so make sure we create nodes for it.
		if len(call.Args) > 0 {
			a.valueNode(call.Args[0])
		}

	case "ssa:wrapnilchk":
		a.copy(a.valueNode(instr.Value()), a.valueNode(call.Args[0]), 1)

	default:
		// No-ops: close len cap real imag complex print println delete.
	}
}

func findCallees(o *Oracle, site ssa.CallInstruction) ([]*ssa.Function, error) {
	// Avoid running the pointer analysis for static calls.
	if callee := site.Common().StaticCallee(); callee != nil {
		switch callee.String() {
		case "runtime.SetFinalizer", "(reflect.Value).Call":
			// The PTA treats calls to these intrinsics as dynamic.
			// TODO(adonovan): avoid reliance on PTA internals.

		default:
			return []*ssa.Function{callee}, nil // singleton
		}
	}

	// Dynamic call: use pointer analysis.
	o.ptaConfig.BuildCallGraph = true
	cg := ptrAnalysis(o).CallGraph
	cg.DeleteSyntheticNodes()

	// Find all call edges from the site.
	n := cg.Nodes[site.Parent()]
	if n == nil {
		return nil, fmt.Errorf("this call site is unreachable in this analysis")
	}
	calleesMap := make(map[*ssa.Function]bool)
	for _, edge := range n.Out {
		if edge.Site == site {
			calleesMap[edge.Callee.Func] = true
		}
	}

	// De-duplicate and sort.
	funcs := make([]*ssa.Function, 0, len(calleesMap))
	for f := range calleesMap {
		funcs = append(funcs, f)
	}
	sort.Sort(byFuncPos(funcs))
	return funcs, nil
}

// addInvokeEdge is called for each new pair (site, C) in the matrix.
func (r *rta) addInvokeEdge(site ssa.CallInstruction, C types.Type) {
	// Ascertain the concrete method of C to be called.
	imethod := site.Common().Method
	cmethod := r.prog.Method(r.prog.MethodSets.MethodSet(C).Lookup(imethod.Pkg(), imethod.Name()))
	r.addEdge(site, cmethod, true)
}