<?php
/**
 * Collection of unique file references
 *
 * @method Loco_fs_File[] getArrayCopy
 */
class Loco_fs_FileList extends ArrayIterator implements Loco_fs_FileListInterface {

    /**
     * Hash map for ensuring files only added once
     * @var array
     */
    private $unique = [];
    
    /**
     * Construct with initial list if files
     * @param Loco_fs_File[] $a
     */
    public function __construct( $a = [] ){
        parent::__construct();
        foreach( $a as $file ){
            $this->add( $file );
        }
    }


    /**
     * Use instead of clone because that does weird things to ArrayIterator instances.
     * Note that this does NOT clone individual file members.
     */
    public function copy():self {
        return new Loco_fs_FileList( $this->getArrayCopy() );
    }
    

    /**
     * Like getArrayCopy, but exports string paths
     * @return string[]
     */
    public function export():array {
        $a = [];
        foreach( $this as $file ){
            $a[] = (string) $file;
        }
        return $a;
    }


    /**
     * @internal
     */
    public function __toString():string {
        return implode( "\n", $this->getArrayCopy() );
    }


    /**
     * Generate a unique key for file
     */
    private function hash( Loco_fs_File $file ):string {
        return $file->getRealPath() ?: $file->normalize();
    }


    /**
     * {@inheritDoc}
     */
    #[ReturnTypeWillChange]
    public function offsetSet( $key, $value ){
        throw new Exception('Use Loco_fs_FileList::add');
    }


    /**
     * {@inheritDoc}
     */
    public function add( Loco_fs_File $file ):bool {
        $hash = $this->hash( $file );
        if( isset($this->unique[$hash]) ){
            return false;
        }
        $this->unique[$hash] = true;
        parent::offsetSet( null, $file );
        return true;
    }


    /**
     * Check if given file is already in list
     */
    public function has( Loco_fs_File $file ):bool {
        $hash = $this->hash( $file );
        return isset($this->unique[$hash]);
    }


    /**
     * Get a copy of list with only files not contained in passed list
     */
    public function diff( Loco_fs_FileList $not_in ):self {
        $list = new Loco_fs_FileList;
        foreach( $this as $file ){
            $not_in->has($file) || $list->add( $file );
        }
        return $list;
    }


    /**
     * Merge another list of the SAME TYPE uniquely on top of current one
     */
    public function augment( loco_fs_FileList $list ):self {
        foreach( $list as $file ){
            $this->add( $file );
        }
        return $this;
    }

}