<?php

namespace UbsCsvTransformer;

/**
 * Reads and parses CSV files
 *
 * Reads CSV files with a configurable delimiter and separates
 * metadata lines from the actual data rows.
 */
class CsvReader
{
    private string $filePath;
    private string $delimiter;
    private int $headerLine;
    private bool $hasBom;

    /**
     * @param string $filePath Path to the CSV file
     * @param array $csvStructure CSV structure from configuration
     */
    public function __construct(string $filePath, array $csvStructure)
    {
        $this->filePath = $filePath;
        $this->delimiter = $csvStructure['inputDelimiter'] ?? ';';
        $this->headerLine = $csvStructure['headerLine'] ?? 1;
        $this->hasBom = $csvStructure['hasBom'] ?? false;
    }

    /**
     * Reads all lines from the file
     *
     * @param int $maxLines Maximum number of lines (0 = all)
     * @return array Array of lines (without newlines)
     * @throws \RuntimeException if file cannot be read
     */
    public function readLines(int $maxLines = 0): array
    {
        if (!file_exists($this->filePath) || !is_readable($this->filePath)) {
            throw new \RuntimeException("Could not read file: {$this->filePath}");
        }

        $lines = file($this->filePath, FILE_IGNORE_NEW_LINES);

        if ($lines === false) {
            throw new \RuntimeException("Could not read file: {$this->filePath}");
        }

        // Remove BOM if present
        if ($this->hasBom && !empty($lines)) {
            $lines[0] = $this->removeBom($lines[0]);
        }

        if ($maxLines > 0 && count($lines) > $maxLines) {
            $lines = array_slice($lines, 0, $maxLines);
        }

        return $lines;
    }

    /**
     * Reads the metadata lines (before the header line)
     *
     * @return array Array of metadata lines
     */
    public function readMetadataLines(): array
    {
        $lines = $this->readLines();

        if ($this->headerLine <= 1) {
            return [];
        }

        return array_slice($lines, 0, $this->headerLine - 1);
    }

    /**
     * Reads CSV data with headers
     *
     * @param int $maxDataRows Maximum number of data rows (0 = all)
     * @return array Array of associative arrays (with column names as keys)
     * @throws \RuntimeException if header line is not found
     */
    public function readCsvData(int $maxDataRows = 0): array
    {
        $lines = $this->readLines();

        if ($this->headerLine > count($lines)) {
            throw new \RuntimeException("Header line {$this->headerLine} not found in file with " . count($lines) . " lines");
        }

        // Parse header
        $headerLineContent = $lines[$this->headerLine - 1];
        $headers = str_getcsv($headerLineContent, $this->delimiter, '"', '\\');
        $headers = array_map(static fn(?string $v): string => trim($v ?? ''), $headers);

        // Parse data rows
        $data = [];
        $dataStartLine = $this->headerLine; // 0-based
        $lineCount = 0;

        for ($i = $dataStartLine; $i < count($lines); $i++) {
            if ($maxDataRows > 0 && $lineCount >= $maxDataRows) {
                break;
            }

            $lineContent = $lines[$i];

            // Skip empty lines
            if (trim($lineContent) === '') {
                continue;
            }

            $row = str_getcsv($lineContent, $this->delimiter, '"', '\\');
            $row = array_map(static fn(?string $v): string => trim($v ?? ''), $row);

            // Combine row with header keys
            $rowData = [];
            foreach ($headers as $index => $header) {
                $rowData[$header] = $row[$index] ?? '';
            }

            $data[] = $rowData;
            $lineCount++;
        }

        return $data;
    }

    /**
     * Returns the column headers
     *
     * @return array Array of column names
     * @throws \RuntimeException if header line is not found
     */
    public function getHeaders(): array
    {
        $lines = $this->readLines();

        if ($this->headerLine > count($lines)) {
            throw new \RuntimeException("Header line {$this->headerLine} not found");
        }

        $headerLineContent = $lines[$this->headerLine - 1];
        $headers = str_getcsv($headerLineContent, $this->delimiter, '"', '\\');

        return array_map(static fn(?string $v): string => trim($v ?? ''), $headers);
    }

    /**
     * Removes UTF-8 BOM (Byte Order Mark) from string
     *
     * @param string $text String with potential BOM
     * @return string String without BOM
     */
    private function removeBom(string $text): string
    {
        if (str_starts_with($text, "\xEF\xBB\xBF")) {
            return substr($text, 3);
        }
        return $text;
    }

    /**
     * Returns the total number of lines in the file
     *
     * @return int Number of lines
     */
    public function countLines(): int
    {
        return count($this->readLines());
    }

    /**
     * Returns the number of data rows (excluding header and metadata)
     *
     * @return int Number of data rows
     */
    public function countDataRows(): int
    {
        return count($this->readCsvData());
    }
}