From a34c84482f9231c11fdf8f2b1164b72d0f08ec1a Mon Sep 17 00:00:00 2001
From: James Harris <contact@jamesharris.id.au>
Date: Sat, 2 Nov 2024 20:18:55 +1000
Subject: [PATCH] WIP [ci skip]

---
 .../staticconfig/{varargs.go => _varargs.go}  |  4 +-
 config/staticconfig/internal/ssax/value.go    | 89 +++++++++++++++++++
 config/staticconfig/route.go                  | 17 +++-
 3 files changed, 105 insertions(+), 5 deletions(-)
 rename config/staticconfig/{varargs.go => _varargs.go} (96%)

diff --git a/config/staticconfig/varargs.go b/config/staticconfig/_varargs.go
similarity index 96%
rename from config/staticconfig/varargs.go
rename to config/staticconfig/_varargs.go
index 0bf7a55..ad95121 100644
--- a/config/staticconfig/varargs.go
+++ b/config/staticconfig/_varargs.go
@@ -48,7 +48,7 @@ func resolveVariadic[
 	E any,
 	B configbuilder.EntityBuilder[T, E],
 ](
-	b B,
+	builderXXXXXXXXXXX B,
 	inst ssa.CallInstruction,
 ) iter.Seq[ssa.Value] {
 	return func(yield func(ssa.Value) bool) {
@@ -61,7 +61,7 @@ func resolveVariadic[
 
 		array, ok := findAllocation(variadics)
 		if !ok {
-			b.Partial()
+			builderXXXXXXXXXXX.Partial()
 			return
 		}
 
diff --git a/config/staticconfig/internal/ssax/value.go b/config/staticconfig/internal/ssax/value.go
index 6cdf4cd..2a38f19 100644
--- a/config/staticconfig/internal/ssax/value.go
+++ b/config/staticconfig/internal/ssax/value.go
@@ -31,6 +31,80 @@ func StaticValue(v ssa.Value) optional.Optional[ssa.Value] {
 	return optional.None[ssa.Value]()
 }
 
+// StaticValuesFromArguments returns the static value(s) used as arguments in
+// the given function call.
+func StaticValuesFromArguments(
+	inst ssa.CallInstruction,
+) (
+	args []optional.Optional[ssa.Value],
+	varargs []SliceElem,
+	exhaustive bool,
+) {
+	call := inst.Common()
+	sig := call.Signature()
+
+	n := sig.Params().Len()
+	if sig.Variadic() {
+		n--
+	}
+
+	args = make([]optional.Optional[ssa.Value], n)
+
+	for i, arg := range call.Args[:n] {
+		args[i] = StaticValue(arg)
+	}
+
+	if !sig.Variadic() {
+		return args, varargs, true
+	}
+
+	varargs, exhaustive = StaticValuesFromSlice(call.Args[n])
+	return args, varargs, exhaustive
+}
+
+// SliceElem represents an element within a slice.
+type SliceElem struct {
+	Index optional.Optional[int]
+	Value optional.Optional[ssa.Value]
+}
+
+// StaticValuesFromSlice returns the static value(s) contained within a slice.
+func StaticValuesFromSlice(
+	v ssa.Value,
+) (elems []SliceElem, exhaustive bool) {
+	array, ok := findUnderlyingArrayAllocation(v)
+	if !ok {
+		return nil, false
+	}
+
+	vinst := v.(ssa.Instruction)
+
+	for b := range WalkBlock(array.Block()) {
+		if vinst != nil && !PathExists(b, vinst.Block()) {
+			continue
+		}
+
+		for inst := range InstructionsBefore(b, vinst) {
+			switch inst := inst.(type) {
+			case *ssa.Store:
+				if addr, ok := inst.Addr.(*ssa.IndexAddr); ok {
+					if addr.X == array {
+						elems = append(
+							elems,
+							SliceElem{
+								Index: AsInt(addr.Index),
+								Value: StaticValue(inst.Val),
+							},
+						)
+					}
+				}
+			}
+		}
+	}
+
+	return elems, true
+}
+
 // staticValuesFromInstruction returns the static value(s) that result from
 // evaluating the given instruction.
 //
@@ -135,3 +209,18 @@ func equal(a, b ssa.Value) bool {
 
 	return false
 }
+
+// findUnderlyingArrayAllocation returns the underlying array allocation of a
+// slice.
+func findUnderlyingArrayAllocation(v ssa.Value) (*ssa.Alloc, bool) {
+	switch v := v.(type) {
+	case *ssa.Alloc:
+		return v, true
+
+	case *ssa.Slice:
+		return findUnderlyingArrayAllocation(v.X)
+
+	default:
+		return nil, false
+	}
+}
diff --git a/config/staticconfig/route.go b/config/staticconfig/route.go
index 54d0688..1cca71a 100644
--- a/config/staticconfig/route.go
+++ b/config/staticconfig/route.go
@@ -3,6 +3,7 @@ package staticconfig
 import (
 	"github.com/dogmatiq/enginekit/config"
 	"github.com/dogmatiq/enginekit/config/internal/configbuilder"
+	"github.com/dogmatiq/enginekit/config/staticconfig/internal/ssax"
 	"github.com/dogmatiq/enginekit/internal/typename"
 	"golang.org/x/tools/go/ssa"
 )
@@ -14,12 +15,22 @@ func analyzeRoutes[
 ](
 	ctx *configurerCallContext[T, H, B],
 ) {
-	for r := range resolveVariadic(ctx.Builder, ctx.Instruction) {
+	_, varargs, exhaustive := ssax.StaticValuesFromArguments(ctx.Instruction)
+	if !exhaustive {
+		ctx.Builder.Partial()
+	}
+
+	for _, elem := range varargs {
 		ctx.Builder.Route(func(b *configbuilder.RouteBuilder) {
-			if ctx.IsSpeculative {
+			if ctx.IsSpeculative || !elem.Index.IsPresent() {
 				b.Speculative() // TODO: is this correct?
 			}
-			analyzeRoute(ctx.context, b, r)
+
+			if r, ok := elem.Value.TryGet(); ok {
+				analyzeRoute(ctx.context, b, r)
+			} else {
+				b.Partial()
+			}
 		})
 	}
 }