Add case when syntax

src/Language/CaseGroup.php

@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tpetry\QueryExpressions\Language;
+
+use Illuminate\Contracts\Database\Query\Expression;
+use Illuminate\Database\Grammar;
+use Tpetry\QueryExpressions\Concerns\IdentifiesDriver;
+use Tpetry\QueryExpressions\Concerns\StringizeExpression;
+
+class CaseGroup implements Expression
+{
+    use IdentifiesDriver;
+    use StringizeExpression;
+
+    /**
+     * @param  non-empty-array<int, CaseRule>  $when
+     */
+    public function __construct(
+        private readonly array $when,
+        private readonly string|Expression|null $else = null,
+    ) {
+    }
+
+    public function getValue(Grammar $grammar): string
+    {
+        $conditions = array_map(
+            callback: fn ($expression) => $this->stringize($grammar, $expression),
+            array: $this->when,
+        );
+        $conditions = implode(' ', $conditions);
+
+        return match ($this->else) {
+            null => "(case {$conditions} end)",
+            default => "(case {$conditions} else {$this->stringize($grammar, $this->else)} end)",
+        };
+    }
+}

src/Language/CaseRule.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tpetry\QueryExpressions\Language;
+
+use Illuminate\Contracts\Database\Query\ConditionExpression;
+use Illuminate\Contracts\Database\Query\Expression;
+use Illuminate\Database\Grammar;
+use Tpetry\QueryExpressions\Concerns\StringizeExpression;
+
+class CaseRule implements Expression
+{
+    use StringizeExpression;
+
+    public function __construct(
+        private readonly string|Expression $result,
+        private readonly ConditionExpression $condition,
+    ) {
+    }
+
+    public function getValue(Grammar $grammar): string
+    {
+        $condition = $this->stringize($grammar, $this->condition);
+        $result = $this->stringize($grammar, $this->result);
+
+        return "when {$condition} then {$result}";
+    }
+}

tests/ConditionExpression.php

@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tpetry\QueryExpressions\Tests;
+
+use Illuminate\Contracts\Database\Query\ConditionExpression as ConditionExpressionContract;
+use Illuminate\Database\Query\Expression;
+
+class ConditionExpression extends Expression implements ConditionExpressionContract
+{
+}

tests/Language/CaseTest.php

@@ -0,0 +1,66 @@
+<?php
+
+declare(strict_types=1);
+
+use Illuminate\Database\Query\Expression;
+use Illuminate\Database\Schema\Blueprint;
+use Tpetry\QueryExpressions\Language\CaseGroup;
+use Tpetry\QueryExpressions\Language\CaseRule;
+use Tpetry\QueryExpressions\Tests\ConditionExpression;
+
+it('can create create a case-expression with a single branch')
+    ->expect(
+        new CaseGroup([
+            new CaseRule(new Expression(2), new ConditionExpression('1 = 1')),
+        ])
+    )
+    ->toBeExecutable()
+    ->toBeMysql('(case when 1 = 1 then 2 end)')
+    ->toBePgsql('(case when 1 = 1 then 2 end)')
+    ->toBeSqlite('(case when 1 = 1 then 2 end)')
+    ->toBeSqlsrv('(case when 1 = 1 then 2 end)');
+
+it('can create create a case-expression with multiple branches')
+    ->expect(new CaseGroup([
+        new CaseRule(new Expression(2), new ConditionExpression('1 = 1')),
+        new CaseRule('val', new ConditionExpression('2 = 2')),
+    ]))
+    ->toBeExecutable(function (Blueprint $table) {
+        $table->integer('val');
+    })
+    ->toBeMysql('(case when 1 = 1 then 2 when 2 = 2 then `val` end)')
+    ->toBePgsql('(case when 1 = 1 then 2 when 2 = 2 then "val" end)')
+    ->toBeSqlite('(case when 1 = 1 then 2 when 2 = 2 then "val" end)')
+    ->toBeSqlsrv('(case when 1 = 1 then 2 when 2 = 2 then [val] end)');
+
+it('can create create a case-expression with multiple branches and expression default')
+    ->expect(new CaseGroup(
+        [
+            new CaseRule(new Expression(2), new ConditionExpression('1 = 1')),
+            new CaseRule('val', new ConditionExpression('2 = 2')),
+        ],
+        new Expression('4'),
+    ))
+    ->toBeExecutable(function (Blueprint $table) {
+        $table->integer('val');
+    })
+    ->toBeMysql('(case when 1 = 1 then 2 when 2 = 2 then `val` else 4 end)')
+    ->toBePgsql('(case when 1 = 1 then 2 when 2 = 2 then "val" else 4 end)')
+    ->toBeSqlite('(case when 1 = 1 then 2 when 2 = 2 then "val" else 4 end)')
+    ->toBeSqlsrv('(case when 1 = 1 then 2 when 2 = 2 then [val] else 4 end)');
+
+it('can create create a case-expression with multiple branches and column default')
+    ->expect(new CaseGroup(
+        [
+            new CaseRule(new Expression(2), new ConditionExpression('1 = 1')),
+            new CaseRule('val', new ConditionExpression('2 = 2')),
+        ],
+        'val',
+    ))
+    ->toBeExecutable(function (Blueprint $table) {
+        $table->integer('val');
+    })
+    ->toBeMysql('(case when 1 = 1 then 2 when 2 = 2 then `val` else `val` end)')
+    ->toBePgsql('(case when 1 = 1 then 2 when 2 = 2 then "val" else "val" end)')
+    ->toBeSqlite('(case when 1 = 1 then 2 when 2 = 2 then "val" else "val" end)')
+    ->toBeSqlsrv('(case when 1 = 1 then 2 when 2 = 2 then [val] else [val] end)');