From 39e6c4bfb1f3fb96bba47e3eec8e6451038a3d22 Mon Sep 17 00:00:00 2001
From: nsfisis <nsfisis@gmail.com>
Date: Sat, 21 Feb 2026 23:22:25 +0900
Subject: feat: implement validation phase

---
 src/WebAssembly/Validation/ValidationStack.php | 154 +++++++++++++++++++++++++
 1 file changed, 154 insertions(+)
 create mode 100644 src/WebAssembly/Validation/ValidationStack.php

(limited to 'src/WebAssembly/Validation/ValidationStack.php')

diff --git a/src/WebAssembly/Validation/ValidationStack.php b/src/WebAssembly/Validation/ValidationStack.php
new file mode 100644
index 0000000..53b47a7
--- /dev/null
+++ b/src/WebAssembly/Validation/ValidationStack.php
@@ -0,0 +1,154 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Nsfisis\Waddiwasi\WebAssembly\Validation;
+
+use Nsfisis\Waddiwasi\WebAssembly\Structure\Instructions\Instrs;
+use Nsfisis\Waddiwasi\WebAssembly\Structure\Types\ValType;
+use function array_pop;
+use function array_reverse;
+use function array_slice;
+use function assert;
+use function count;
+
+final class ValidationStack
+{
+    /**
+     * @var list<?ValType>
+     */
+    private array $values = [];
+
+    /**
+     * @var list<ControlFrame>
+     */
+    private array $controls = [];
+
+    public function __construct(
+    ) {
+    }
+
+    public function pushVal(?ValType $type): void
+    {
+        $this->values[] = $type;
+    }
+
+    /**
+     * @param list<?ValType> $types
+     */
+    public function pushVals(array $types): void
+    {
+        foreach ($types as $type) {
+            $this->pushVal($type);
+        }
+    }
+
+    public function popVal(): ?ValType
+    {
+        // Check stack underflow.
+        $currentCtrl = $this->getCurrentControl();
+        if (count($this->values) === $currentCtrl->height) {
+            // If the current control frame is marked as unreachable, the stack behaves polymorphically.
+            if ($currentCtrl->unreachable) {
+                return null;
+            }
+            throw new ValidationFailureException('Value stack underflow');
+        }
+
+        return array_pop($this->values);
+    }
+
+    public function popValOf(?ValType $expect): ?ValType
+    {
+        $actual = $this->popVal();
+        if ($actual !== $expect && $actual !== null && $expect !== null) {
+            throw new ValidationFailureException('Type mismatch');
+        }
+        return $actual;
+    }
+
+    /**
+     * @param list<ValType> $types
+     * @return list<?ValType>
+     */
+    public function popVals(array $types): array
+    {
+        $popped = [];
+        foreach (array_reverse($types) as $type) {
+            $popped[] = $this->popValOf($type);
+        }
+        return array_reverse($popped);
+    }
+
+    /**
+     * @param class-string $opcode
+     * @param list<ValType> $in
+     * @param list<ValType> $out
+     */
+    public function pushCtrl(string $opcode, array $in, array $out): void
+    {
+        $ctrl = new ControlFrame($opcode, $in, $out, count($this->values), false);
+        $this->controls[] = $ctrl;
+        $this->pushVals($in);
+    }
+
+    public function popCtrl(): ControlFrame
+    {
+        if ($this->controlDepth() === 0) {
+            throw new ValidationFailureException('Control stack underflow');
+        }
+        $ctrl = $this->getCurrentControl();
+        $this->popVals($ctrl->endTypes);
+        if (count($this->values) !== $ctrl->height) {
+            throw new ValidationFailureException('Invalid stack height');
+        }
+        array_pop($this->controls);
+        return $ctrl;
+    }
+
+    /**
+     * @return list<ValType>
+     */
+    public function labelTypes(ControlFrame $ctrl): array
+    {
+        return $ctrl->opcode === Instrs\Control\Loop::class ? $ctrl->startTypes : $ctrl->endTypes;
+    }
+
+    public function unreachable(): void
+    {
+        $currentCtrl = $this->getCurrentControl();
+        $this->values = array_slice($this->values, 0, $currentCtrl->height);
+        assert(count($this->controls) !== 0);
+        array_pop($this->controls);
+        $this->controls[] = new ControlFrame(
+            $currentCtrl->opcode,
+            $currentCtrl->startTypes,
+            $currentCtrl->endTypes,
+            $currentCtrl->height,
+            true,
+        );
+    }
+
+    public function controlDepth(): int
+    {
+        return count($this->controls);
+    }
+
+    public function getControl(int $index): ?ControlFrame
+    {
+        $absIndex = count($this->controls) - 1 - $index;
+        if ($absIndex < 0) {
+            return null;
+        }
+        return $this->controls[$absIndex] ?? null;
+    }
+
+    public function getCurrentControl(): ControlFrame
+    {
+        if ($this->controlDepth() === 0) {
+            throw new ValidationFailureException('No control frame available');
+        }
+        assert(count($this->controls) !== 0);
+        return $this->controls[array_key_last($this->controls)];
+    }
+}
-- 
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