<?php

namespace NoccyLabs\Dataset\Readers;

use NoccyLabs\Dataset\ReaderInterface;

class JsonReader implements ReaderInterface
{
    private array $files = [];

    private array $options = [];

    private int $currentFile = 0;

    private ?int $loadedFile = null;

    private array $data = [];

    private int $currentIndex = 0;

    private int $counter = 0;

    public function __construct(string $filename, array $options)
    {
        $this->files = glob($filename);
        $this->options = $options;
    }

    private function checkLoadedSlice()
    {
        // If the current file is the loaded file, we're already set
        if ($this->currentFile === $this->loadedFile) return;

        if ($this->currentFile >= count($this->files)) {
            //printf("Reached end of set at slice=%d\n", $this->currentFile);
            return;
        }

        $flags = ($this->options['bigintAsString']??false)?JSON_BIGINT_AS_STRING:0;
        $file = $this->files[$this->currentFile]; 
        $json = @json_decode(@file_get_contents($file), true, flags:$flags);

        $this->loadData($json);
        $this->loadedFile = $this->currentFile;
        //printf("loaded slice %d: %s\n", $this->currentFile, $file);
    }

    private function loadData(array $data)
    {
        // FIXME parse data according to directives if present
        $this->data = $data;
        $this->currentIndex = 0;
    }

    public function rewind(): void
    {
        $this->currentFile = 0;
        $this->currentIndex = 0;
        $this->counter = 0;
        //printf("Rewinding to slice=%d index=%d\n", $this->currentFile, $this->currentIndex);
        $this->checkLoadedSlice();
    }

    public function key(): mixed
    {
        //$this->checkLoadedSlice();
        return $this->counter;
    }

    public function current(): mixed
    {
        //$this->checkLoadedSlice();   
        return $this->data[$this->currentIndex];
    }

    public function next(): void
    {
        $this->counter++;        
        $this->currentIndex++;
        
        if ($this->currentIndex >= count($this->data)) {
            $this->currentFile++;
            $this->currentIndex = 0;
            //printf("Rolling over to slice=%d index=%d counter=%d\n", $this->currentFile, $this->currentIndex, $this->counter);
        }

        //$this->checkLoadedSlice();   
    }

    public function valid(): bool
    {
        $this->checkLoadedSlice();
        return ($this->currentFile < count($this->files) && ($this->currentIndex < count($this->data)));
        
    }
}