feat: string concatenation (tpetry#4)

Co-authored-by: tpetry <[email protected]>

Author: elcapo

README.md

@@ -255,8 +255,11 @@ BlogArticle::select([
 
 #### String
 ```php
-use Tpetry\QueryExpressions\Function\String\Uuid4;
+use Tpetry\QueryExpressions\Function\String\{
+    Concat, Uuid4
+};
 
+new Concat(array $expressions);
 new Uuid4();
 
 Schema::table('users', function (Blueprint $table): void {

src/Function/String/Concat.php

@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tpetry\QueryExpressions\Function\String;
+
+use Illuminate\Database\Grammar;
+use Tpetry\QueryExpressions\Concerns\IdentifiesDriver;
+use Tpetry\QueryExpressions\Function\Conditional\ManyArgumentsExpression;
+
+class Concat extends ManyArgumentsExpression
+{
+    use IdentifiesDriver;
+
+    public function getValue(Grammar $grammar): string
+    {
+        $expressions = $this->getExpressions($grammar);
+
+        return match ($this->identify($grammar)) {
+            'mysql', 'sqlsrv' => sprintf('(concat(%s))', implode(',', $expressions)),
+            'pgsql', 'sqlite' => sprintf('(%s)', implode('||', $expressions)),
+        };
+    }
+}

tests/Function/String/ConcatTest.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+use Illuminate\Database\Query\Expression;
+use Tpetry\QueryExpressions\Function\String\Concat;
+
+it('can concat multiple columns')
+    ->expect(new Concat(['val1', 'val2', 'val3']))
+    ->toBeExecutable(['val1 varchar(255)', 'val2 varchar(255)', 'val3 varchar(255)'])
+    ->toBeMysql('(concat(`val1`,`val2`,`val3`))')
+    ->toBePgsql('("val1"||"val2"||"val3")')
+    ->toBeSqlite('("val1"||"val2"||"val3")')
+    ->toBeSqlsrv('(concat([val1],[val2],[val3]))');
+
+it('can concat multiple expressions')
+    ->expect(new Concat([new Expression("'a'"), new Expression("'b'"), new Expression("'c'")]))
+    ->toBeExecutable()
+    ->toBeMysql("(concat('a','b','c'))")
+    ->toBePgsql("('a'||'b'||'c')")
+    ->toBeSqlite("('a'||'b'||'c')")
+    ->toBeSqlsrv("(concat('a','b','c'))");
+
+it('can concat multiple columns and expressions')
+    ->expect(new Concat(['val1', 'val2', new Expression("'c'")]))
+    ->toBeExecutable(['val1 varchar(255)', 'val2 varchar(255)'])
+    ->toBeMysql("(concat(`val1`,`val2`,'c'))")
+    ->toBePgsql('("val1"||"val2"||\'c\')')
+    ->toBeSqlite('("val1"||"val2"||\'c\')')
+    ->toBeSqlsrv("(concat([val1],[val2],'c'))");