<?php

namespace TablePress\PhpOffice\PhpSpreadsheet\Reader\Csv;

class Delimiter
{
	protected const POTENTIAL_DELIMETERS = [',', ';', "\t", '|', ':', ' ', '~'];

	/** @var resource */
	protected $fileHandle;

	protected string $escapeCharacter;

	protected string $enclosure;

	/** @var array<string, int[]> */
	protected array $counts = [];

	protected int $numberLines = 0;

	protected ?string $delimiter = null;

	/**
	 * @param resource $fileHandle
	 */
	public function __construct($fileHandle, string $escapeCharacter, string $enclosure)
	{
		$this->fileHandle = $fileHandle;
		$this->escapeCharacter = $escapeCharacter;
		$this->enclosure = $enclosure;

		$this->countPotentialDelimiters();
	}

	public function getDefaultDelimiter(): string
	{
		return self::POTENTIAL_DELIMETERS[0];
	}

	public function linesCounted(): int
	{
		return $this->numberLines;
	}

	protected function countPotentialDelimiters(): void
	{
		$this->counts = array_fill_keys(self::POTENTIAL_DELIMETERS, []);
		$delimiterKeys = array_flip(self::POTENTIAL_DELIMETERS);

		// Count how many times each of the potential delimiters appears in each line
		$this->numberLines = 0;
		while (($line = $this->getNextLine()) !== false && (++$this->numberLines < 1000)) {
			$this->countDelimiterValues($line, $delimiterKeys);
		}
	}

	/** @param array<string, int> $delimiterKeys */
	protected function countDelimiterValues(string $line, array $delimiterKeys): void
	{
		$splitString = mb_str_split($line, 1, 'UTF-8');
		$distribution = array_count_values($splitString);
		$countLine = array_intersect_key($distribution, $delimiterKeys);

		foreach (self::POTENTIAL_DELIMETERS as $delimiter) {
			$this->counts[$delimiter][] = $countLine[$delimiter] ?? 0;
		}
	}

	public function infer(): ?string
	{
		// Calculate the mean square deviations for each delimiter
		//     (ignoring delimiters that haven't been found consistently)
		$meanSquareDeviations = [];
		$middleIdx = (int) floor(($this->numberLines - 1) / 2);

		foreach (self::POTENTIAL_DELIMETERS as $delimiter) {
			$series = $this->counts[$delimiter];
			sort($series);

			$median = ($this->numberLines % 2)
				? $series[$middleIdx]
				: ($series[$middleIdx] + $series[$middleIdx + 1]) / 2;

			if ($median === 0) {
				continue;
			}

			$meanSquareDeviations[$delimiter] = array_reduce(
				$series,
				fn ($sum, $value) => $sum + ($value - $median) ** 2
			) / count($series);
		}

		// ... and pick the delimiter with the smallest mean square deviation
		//         (in case of ties, the order in potentialDelimiters is respected)
		$min = INF;
		foreach (self::POTENTIAL_DELIMETERS as $delimiter) {
			if (!isset($meanSquareDeviations[$delimiter])) {
				continue;
			}

			if ($meanSquareDeviations[$delimiter] < $min) {
				$min = $meanSquareDeviations[$delimiter];
				$this->delimiter = $delimiter;
			}
		}

		return $this->delimiter;
	}

	/**
	 * Get the next full line from the file.
	 *
	 * @return false|string
	 */
	public function getNextLine()
	{
		$line = '';
		$enclosure = ($this->escapeCharacter === '' ? ''
				: ('(?<!' . preg_quote($this->escapeCharacter, '/') . ')'))
			. preg_quote($this->enclosure, '/');

		do {
			// Get the next line in the file
			$newLine = fgets($this->fileHandle);

			// Return false if there is no next line
			if ($newLine === false) {
				return false;
			}

			// Add the new line to the line passed in
			$line = $line . $newLine;

			// Drop everything that is enclosed to avoid counting false positives in enclosures
			$line = (string) preg_replace('/(' . $enclosure . '.*' . $enclosure . ')/Us', '', $line);

			// See if we have any enclosures left in the line
			// if we still have an enclosure then we need to read the next line as well
		} while (preg_match('/(' . $enclosure . ')/', $line) > 0);

		return ($line !== '') ? $line : false;
	}
}
