Adding Statement::select method

CHANGELOG.md

@@ -2,6 +2,24 @@
 
 All Notable changes to `Csv` will be documented in this file
 
+## [Next](https://github.com/thephpleague/csv/compare/9.14.0...master) - TBD
+
+### Added
+
+- `Statement::select`
+
+### Deprecated
+
+- None
+
+### Fixed
+
+- `Reader::select` and `ResultSet::select` now internally use `Statement::select`
+
+### Removed
+
+- None
+
 ## [9.14.0](https://github.com/thephpleague/csv/compare/9.13.0...9.14.0) - 2023-12-29
 
 ### Added

src/Reader.php

@@ -395,7 +395,7 @@ public function matchingFirstOrFail(string $expression): TabularDataReader
 
     public function select(string|int ...$columns): TabularDataReader
     {
-        return ResultSet::createFromTabularDataReader($this)->select(...$columns);
+        return Statement::create()->select(...$columns)->process($this);
     }
 
     /**

src/ResultSet.php

@@ -177,35 +177,7 @@ public function sorted(Closure $orderBy): TabularDataReader
 
     public function select(string|int ...$columns): TabularDataReader
     {
-        $header = [];
-        $documentHeader = $this->getHeader();
-        $hasNoHeader = [] === $documentHeader;
-        foreach ($columns as $field) {
-            if (is_string($field)) {
-                if ($hasNoHeader) {
-                    throw new InvalidArgument(__METHOD__.' can only use named column if the tabular data has a non-empty header.');
-                }
-
-                $index = array_search($field, $this->header, true);
-                if (false === $index) {
-                    throw InvalidArgument::dueToInvalidColumnIndex($field, 'offset', __METHOD__);
-                }
-
-                $header[$index] = $field;
-                continue;
-            }
-
-            if (!$hasNoHeader && !array_key_exists($field, $documentHeader)) {
-                throw InvalidArgument::dueToInvalidColumnIndex($field, 'offset', __METHOD__);
-            }
-
-            $header[$field] = $documentHeader[$field] ?? $field;
-        }
-
-        /** @var array<int, string> $finalHeader */
-        $finalHeader = $hasNoHeader ? [] : $header;
-
-        return new self($this->combineHeader($header), $finalHeader);
+        return Statement::create()->select(...$columns)->process($this);
     }
 
     public function matching(string $expression): iterable

src/Serializer/CastToEnum.php

@@ -86,7 +86,7 @@ private function cast(string $value): BackedEnum|UnitEnum
                 return $enum->getCase($value)->getValue();
             }
 
-            $backedValue = 'int' === $enum->getBackingType()?->getName() ? filter_var($value, Type::Int->filterFlag()) : $value;
+            $backedValue = 'int' === $enum->getBackingType()->getName() ? filter_var($value, Type::Int->filterFlag()) : $value;
 
             return $this->class::from($backedValue); /* @phpstan-ignore-line */
         } catch (Throwable $exception) {

src/Statement.php

@@ -35,6 +35,8 @@ class Statement
     protected int $offset = 0;
     /** iterator maximum length. */
     protected int $limit = -1;
+    /** @var array<string|int> */
+    protected array $select = [];
 
     /**
      * @throws Exception
@@ -136,7 +138,7 @@ public function process(TabularDataReader $tabular_data, array $header = []): Ta
         /** @var Iterator<array-key, array<array-key, string|null>> $iterator */
         $iterator = new LimitIterator($iterator, $this->offset, $this->limit);
 
-        return new ResultSet($iterator, $header);
+        return $this->applySelect(new ResultSet($iterator, $header));
     }
 
     /**
@@ -172,4 +174,63 @@ protected function buildOrderBy(Iterator $iterator): Iterator
 
         return $it;
     }
+
+    public function select(string|int ...$columns): self
+    {
+        if ($columns === $this->select) {
+            return $this;
+        }
+
+        $clone = clone $this;
+        $clone->select = $columns;
+
+        return $clone;
+    }
+
+    protected function applySelect(TabularDataReader $tabularDataReader): TabularDataReader
+    {
+        if ([] === $this->select) {
+            return $tabularDataReader;
+        }
+
+        $header = [];
+        $documentHeader = $tabularDataReader->getHeader();
+        $hasNoHeader = [] === $documentHeader;
+        foreach ($this->select as $field) {
+            if (is_string($field)) {
+                if ($hasNoHeader) {
+                    throw new InvalidArgument(__METHOD__.' can only use named column if the tabular data has a non-empty header.');
+                }
+
+                $index = array_search($field, $documentHeader, true);
+                if (false === $index) {
+                    throw InvalidArgument::dueToInvalidColumnIndex($field, 'offset', __METHOD__);
+                }
+
+                $header[$index] = $field;
+                continue;
+            }
+
+            if (!$hasNoHeader && !array_key_exists($field, $documentHeader)) {
+                throw InvalidArgument::dueToInvalidColumnIndex($field, 'offset', __METHOD__);
+            }
+
+            $header[$field] = $documentHeader[$field] ?? $field;
+        }
+
+        $records = new MapIterator($tabularDataReader, function (array $record) use ($header): array {
+            $assocRecord = [];
+            $row = array_values($record);
+            foreach ($header as $offset => $headerName) {
+                $assocRecord[$headerName] = $row[$offset] ?? null;
+            }
+
+            return $assocRecord;
+        });
+
+        /** @var array<string>. $finalHeader */
+        $finalHeader = $hasNoHeader ? [] : $header;
+
+        return new ResultSet($records, $finalHeader);
+    }
 }