<?php
/**
 * NY 问卷考试系统数据平台 - 零依赖 XLSX 生成
 *
 * 仅用 PHP 内置函数生成最小可用的 .xlsx 文件：
 *  - 有 zip 扩展时走 ZipArchive；无 zip 扩展时回退到"手写 ZIP(stored)"实现，保证任何环境都能导出
 *  - 单元格统一按「共享字符串 + 文本格式(numFmtId=49)」写入，学号/账号等长数字不会被转成科学计数法
 *  - 第一行固定为表头（加粗 + 居中）
 */
declare(strict_types=1);

final class XlsxWriter
{
    /** @var array<string,int> 共享字符串 => 索引 */
    private array $strIndex = [];
    /** @var array<int,string> 索引 => 共享字符串 */
    private array $strings = [];
    /** @var array<int,int> 索引 => 出现次数（sst 的 count 用，区别于 uniqueCount） */
    private array $strCount = [];
    /** @var array<int,array{name:string,rows:array,widths:array}> 工作表（按输出顺序） */
    private array $sheets = [];

    // 样式索引（见 stylesXml）
    private const S_DEFAULT = 0; // 常规
    private const S_HEADER  = 1; // 表头：加粗 + 居中
    private const S_TEXT    = 2; // 文本格式（numFmtId=49）

    /**
     * 生成单表 xlsx 二进制内容（兼容旧调用）
     *
     * @param array $rows   二维表，第一行视为表头；每个元素会被强制转成字符串
     * @param array $opts   ['widths' => [列宽,...], 'title' => 工作表名]
     * @return string xlsx 文件二进制
     */
    public static function render(array $rows, array $opts = []): string
    {
        return self::renderMulti([[
            'name'   => (string)($opts['title'] ?? 'Sheet1'),
            'rows'   => $rows,
            'widths' => array_values((array)($opts['widths'] ?? [])),
        ]]);
    }

    /**
     * 生成多工作表 xlsx
     *
     * 说明：所有单元格都写成「共享字符串 + 文本格式(numFmtId=49)」，
     * 因此既不会出现长学号被转成科学计数法，也不会把以 = + - @ 开头的内容
     * 当成公式执行（天然规避 CSV 公式注入问题）。
     *
     * @param array $sheets 每个元素：['name'=>工作表名, 'rows'=>二维表, 'widths'=>[列宽...]]
     * @return string xlsx 文件二进制
     */
    public static function renderMulti(array $sheets): string
    {
        $w = new self();
        foreach ($sheets as $sh) {
            if (!is_array($sh)) {
                continue;
            }
            $rows = array_values((array)($sh['rows'] ?? []));
            if ($rows === []) {
                continue; // 空表不输出，避免 Excel 提示修复
            }
            $w->sheets[] = [
                'name'   => self::safeSheetName((string)($sh['name'] ?? ''), count($w->sheets) + 1, $w->sheets),
                'rows'   => $rows,
                'widths' => array_values((array)($sh['widths'] ?? [])),
            ];
        }
        if ($w->sheets === []) {
            // 保底：至少输出一张空表
            $w->sheets[] = ['name' => 'Sheet1', 'rows' => [['']], 'widths' => []];
        }
        return $w->build();
    }

    /* ---------------- 内部：构建 ---------------- */

    private function build(): string
    {
        $files = [
            '[Content_Types].xml' => '', // 占位，下面按表数量生成
        ];
        $sheetXmls = [];
        $names     = [];

        foreach ($this->sheets as $i => $sh) {
            $n = $i + 1;

            $maxCol = 1;
            foreach ($sh['rows'] as $r) {
                $maxCol = max($maxCol, count((array)$r));
            }
            $maxRow = max(1, count($sh['rows']));

            // 登记共享字符串并生成单元格索引
            $cells = [];
            foreach (array_values($sh['rows']) as $ri => $row) {
                $r = (int)$ri + 1;
                foreach (array_values((array)$row) as $ci => $val) {
                    $c = (int)$ci + 1;
                    $cells[$r][$c] = $this->intern((string)($val ?? ''));
                }
            }
            $sheetXmls['xl/worksheets/sheet' . $n . '.xml'] = $this->sheetXml($cells, $maxRow, $maxCol, $sh['widths']);
            $names[] = $sh['name'];
        }

        $count = count($this->sheets);
        $files = [
            '[Content_Types].xml'        => $this->contentTypesXml($count),
            '_rels/.rels'                => $this->rootRelsXml(),
            'docProps/app.xml'           => $this->appXml(),
            'docProps/core.xml'          => $this->coreXml($names[0] ?? 'Sheet1'),
            'xl/workbook.xml'            => $this->workbookXml($names),
            'xl/_rels/workbook.xml.rels' => $this->workbookRelsXml($count),
            'xl/styles.xml'              => $this->stylesXml(),
            'xl/sharedStrings.xml'       => $this->sharedStringsXml(),
        ] + $sheetXmls;

        return $this->zip($files);
    }

    /**
     * 工作表名安全化：Excel 限制 31 字符、禁止 []:*?/\、不可重复、不可为空
     */
    private static function safeSheetName(string $name, int $seq, array $existing): string
    {
        $bad = ['\\', '/', '?', '*', '[', ']', ':'];
        $n = trim(str_replace($bad, '_', $name));
        if ($n === '') {
            $n = 'Sheet' . $seq;
        }
        if (function_exists('mb_substr')) {
            $n = mb_substr($n, 0, 31, 'UTF-8');
        } else {
            $n = substr($n, 0, 31);
        }
        // 去重
        $base = $n;
        $i = 2;
        $taken = [];
        foreach ($existing as $e) {
            $taken[strtolower($e['name'])] = true;
        }
        while (isset($taken[strtolower($n)])) {
            $suffix = '(' . $i . ')';
            $n = (function_exists('mb_substr') ? mb_substr($base, 0, 31 - strlen($suffix), 'UTF-8') : substr($base, 0, 31 - strlen($suffix))) . $suffix;
            $i++;
        }
        return $n;
    }

    private function intern(string $s): int
    {
        if (!array_key_exists($s, $this->strIndex)) {
            $i = count($this->strings);
            $this->strIndex[$s] = $i;
            $this->strings[$i] = $s;
            $this->strCount[$i] = 0;
        }
        $i = $this->strIndex[$s];
        $this->strCount[$i] = ($this->strCount[$i] ?? 0) + 1;
        return $i;
    }

    private function sheetXml(array $cells, int $maxRow, int $maxCol, array $widths = []): string
    {
        $dim = 'A1:' . self::colName($maxCol) . $maxRow;

        $cols = '';
        for ($c = 1; $c <= $maxCol; $c++) {
            $w = $widths[$c - 1] ?? 16;
            $cols .= '<col min="' . $c . '" max="' . $c . '" width="' . $w . '" customWidth="1"/>';
        }

        $data = '';
        for ($r = 1; $r <= $maxRow; $r++) {
            $line = '';
            $has = false;
            for ($c = 1; $c <= $maxCol; $c++) {
                if (!isset($cells[$r][$c])) {
                    continue;
                }
                $has = true;
                $s = $r === 1 ? self::S_HEADER : self::S_TEXT;
                $line .= '<c r="' . self::colName($c) . $r . '" s="' . $s . '" t="s"><v>' .
                    $cells[$r][$c] . '</v></c>';
            }
            if (!$has) {
                continue;
            }
            $data .= '<row r="' . $r . '" spans="1:' . $maxCol . '">' . $line . '</row>';
        }

        return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n" .
            '<worksheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">' .
            '<dimension ref="' . $dim . '"/>' .
            '<sheetViews><sheetView workbookViewId="0"/></sheetViews>' .
            '<sheetFormatPr defaultRowHeight="13.5"/>' .
            ($cols !== '' ? '<cols>' . $cols . '</cols>' : '') .
            '<sheetData>' . $data . '</sheetData>' .
            '</worksheet>';
    }

    private function contentTypesXml(int $sheetCount): string
    {
        $overrides = '';
        for ($i = 1; $i <= max(1, $sheetCount); $i++) {
            $overrides .= '<Override PartName="/xl/worksheets/sheet' . $i . '.xml" ' .
                'ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml"/>';
        }
        return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n" .
            '<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">' .
            '<Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>' .
            '<Default Extension="xml" ContentType="application/xml"/>' .
            '<Override PartName="/xl/workbook.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"/>' .
            $overrides .
            '<Override PartName="/xl/styles.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml"/>' .
            '<Override PartName="/xl/sharedStrings.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sharedStrings+xml"/>' .
            '<Override PartName="/docProps/core.xml" ContentType="application/vnd.openxmlformats-package.core-properties+xml"/>' .
            '<Override PartName="/docProps/app.xml" ContentType="application/vnd.openxmlformats-officedocument.extended-properties+xml"/>' .
            '</Types>';
    }

    private function rootRelsXml(): string
    {
        return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n" .
            '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">' .
            '<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="xl/workbook.xml"/>' .
            '<Relationship Id="rId2" Type="http://schemas.openxmlformats.org/package/2006/relationships/metadata/core-properties" Target="docProps/core.xml"/>' .
            '<Relationship Id="rId3" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/extended-properties" Target="docProps/app.xml"/>' .
            '</Relationships>';
    }

    /** @param array<int,string> $names 工作表名（已安全化） */
    private function workbookXml(array $names): string
    {
        $sheets = '';
        foreach (array_values($names) as $i => $nm) {
            $n = (int)$i + 1;
            $sheets .= '<sheet name="' . self::xml((string)$nm) . '" sheetId="' . $n . '" r:id="rId' . $n . '"/>';
        }
        return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n" .
            '<workbook xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" ' .
            'xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">' .
            '<sheets>' . $sheets . '</sheets>' .
            '</workbook>';
    }

    private function workbookRelsXml(int $sheetCount): string
    {
        $rels = '';
        for ($i = 1; $i <= max(1, $sheetCount); $i++) {
            $rels .= '<Relationship Id="rId' . $i . '" ' .
                'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet" ' .
                'Target="worksheets/sheet' . $i . '.xml"/>';
        }
        $stylesId = max(1, $sheetCount) + 1;
        $sstId    = max(1, $sheetCount) + 2;
        return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n" .
            '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">' .
            $rels .
            '<Relationship Id="rId' . $stylesId . '" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles" Target="styles.xml"/>' .
            '<Relationship Id="rId' . $sstId . '" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/sharedStrings" Target="sharedStrings.xml"/>' .
            '</Relationships>';
    }

    private function stylesXml(): string
    {
        return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n" .
            '<styleSheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">' .
            // numFmts: 49 = @（文本）
            '<numFmts count="1"><numFmt numFmtId="49" formatCode="@"/></numFmts>' .
            '<fonts count="2">' .
            '<font><sz val="11"/><color theme="1"/><name val="宋体"/><charset val="134"/></font>' .
            '<font><b/><sz val="11"/><color theme="1"/><name val="宋体"/><charset val="134"/></font>' .
            '</fonts>' .
            '<fills count="2"><fill><patternFill patternType="none"/></fill>' .
            '<fill><patternFill patternType="gray125"/></fill></fills>' .
            '<borders count="1"><border><left/><right/><top/><bottom/><diagonal/></border></borders>' .
            '<cellStyleXfs count="1"><xf numFmtId="0" fontId="0" fillId="0" borderId="0"/></cellStyleXfs>' .
            '<cellXfs count="3">' .
            '<xf numFmtId="0" fontId="0" fillId="0" borderId="0" xfId="0"/>' .                                          // 0 常规
            '<xf numFmtId="0" fontId="1" fillId="0" borderId="0" xfId="0" applyFont="1"><alignment horizontal="center" vertical="center"/></xf>' . // 1 表头
            '<xf numFmtId="49" fontId="0" fillId="0" borderId="0" xfId="0" applyNumberFormat="1"><alignment vertical="center"/></xf>' .             // 2 文本
            '</cellXfs>' .
            '<cellStyles count="1"><cellStyle name="常规" xfId="0" builtinId="0"/></cellStyles>' .
            '</styleSheet>';
    }

    private function sharedStringsXml(): string
    {
        $unique = count($this->strings);
        $total  = array_sum($this->strCount);
        $body = '';
        foreach ($this->strings as $s) {
            $body .= '<si><t xml:space="preserve">' . self::xml((string)$s) . '</t></si>';
        }
        return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n" .
            '<sst xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" count="' . $total .
            '" uniqueCount="' . $unique . '">' . $body . '</sst>';
    }

    private function coreXml(string $title): string
    {
        return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n" .
            '<cp:coreProperties xmlns:cp="http://schemas.openxmlformats.org/package/2006/metadata/core-properties" ' .
            'xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" ' .
            'xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">' .
            '<dc:title>' . self::xml($title) . '</dc:title>' .
            '<dc:creator>NY问卷考试系统数据平台</dc:creator>' .
            '<cp:lastModifiedBy>NY问卷考试系统数据平台</cp:lastModifiedBy>' .
            '<dcterms:created xsi:type="dcterms:W3CDTF">' . gmdate('Y-m-d\TH:i:s\Z') . '</dcterms:created>' .
            '<dcterms:modified xsi:type="dcterms:W3CDTF">' . gmdate('Y-m-d\TH:i:s\Z') . '</dcterms:modified>' .
            '</cp:coreProperties>';
    }

    private function appXml(): string
    {
        return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n" .
            '<Properties xmlns="http://schemas.openxmlformats.org/officeDocument/2006/extended-properties" ' .
            'xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes">' .
            '<Application>NY Exam Platform</Application></Properties>';
    }

    /* ---------------- 内部：打包 ---------------- */

    /** @param array<string,string> $files 相对路径 => 内容 */
    private function zip(array $files): string
    {
        if (class_exists('ZipArchive')) {
            $tmp = tempnam(sys_get_temp_dir(), 'nyx');
            if ($tmp !== false) {
                $zip = new ZipArchive();
                if ($zip->open($tmp, ZipArchive::OVERWRITE) === true) {
                    foreach ($files as $name => $content) {
                        $zip->addFromString($name, $content);
                    }
                    $zip->close();
                    $bin = (string)@file_get_contents($tmp);
                    @unlink($tmp);
                    if ($bin !== '') {
                        return $bin;
                    }
                }
                @unlink($tmp);
            }
        }
        return self::packManual($files);
    }

    /**
     * 无 zip 扩展时的手写打包（stored，不压缩）
     * 单独公开，便于在没有 ZipArchive 的环境下自检
     *
     * @param array<string,string> $files 相对路径 => 内容
     */
    public static function packManual(array $files): string
    {
        $local = '';
        $central = '';
        $offset = 0;
        $time = self::dosTime();
        $date = self::dosDate();

        foreach ($files as $name => $content) {
            $nameBin = (string)$name;
            $data = (string)$content;
            $crc = crc32($data);
            $len = strlen($data);

            $local .= "\x50\x4b\x03\x04" . pack('vvvvvVVVvv', 20, 0x0800, 0, $time, $date, $crc, $len, $len, strlen($nameBin), 0) . $nameBin . $data;
            $central .= "\x50\x4b\x01\x02" . pack('vvvvvvVVVvvvvvVV', 20, 20, 0x0800, 0, $time, $date, $crc, $len, $len, strlen($nameBin), 0, 0, 0, 0, 0, $offset) . $nameBin;
            $offset += 30 + strlen($nameBin) + $len;
        }

        return $local . $central .
            "\x50\x4b\x05\x06" . pack('vvvvVVv', 0, 0, count($files), count($files), strlen($central), $offset, 0);
    }

    private static function dosTime(): int
    {
        $t = getdate();
        return ($t['hours'] << 11) | ($t['minutes'] << 5) | (intdiv($t['seconds'], 2) & 0x1f);
    }

    private static function dosDate(): int
    {
        $t = getdate();
        return (($t['year'] - 1980) << 9) | ($t['mon'] << 5) | $t['mday'];
    }

    /* ---------------- 工具 ---------------- */

    private static function xml(string $s): string
    {
        return htmlspecialchars($s, ENT_XML1 | ENT_COMPAT, 'UTF-8');
    }

    /** 列序号(1基) => A / B / ... / AA */
    private static function colName(int $n): string
    {
        $s = '';
        while ($n > 0) {
            $m = ($n - 1) % 26;
            $s = chr(65 + $m) . $s;
            $n = intdiv($n - 1, 26);
        }
        return $s ?: 'A';
    }
}