<?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
 *  - 表头行（默认第 1 行，可用 header_rows 指定多行）加粗 + 居中 + 边框
 *  - 支持合并单元格（merges），被合并的非首格写「空值 + 同样的样式」，保证合并区域四周边框完整
 *  - 支持单元格级样式（cell_styles）：按 [行,列] 指定「红字 / 绿底」等标记，
 *    用于"每场最高分标红、合格次数达标标绿"
 */
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,merges: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（无边框）
    private const S_HEADER  = 1; // 表头：加粗 + 居中 + 细边框
    private const S_TEXT    = 2; // 数据：文本格式（numFmtId=49）+ 细边框
    private const S_RED     = 3; // 数据 + 红字（最高分标记）
    private const S_GREEN   = 4; // 数据 + 绿底（合格次数达标标记）
    private const S_HEADER_GREEN = 5; // 表头样式 + 绿底（合格次数行的表头格）

    /**
     * 语义化标记 => 样式索引。调用方只管语义（'red' / 'green' / 'header_green'），
     * 具体配色编号由本类统一维护，避免外部硬编码样式下标。
     */
    private const MARK_STYLES = [
        'red'          => self::S_RED,
        'green'        => self::S_GREEN,
        'header_green' => self::S_HEADER_GREEN,
    ];

    /**
     * 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...], 'merges'=>[[r1,c1,r2,c2],...], 'header_rows'=>int,
     *                                   'cell_styles'=>['r,c'=>'red'|'green'|'header_green', ...]]
     *                      merges 为 1-based 闭区间（含表头行），如 [[2,1,4,1]] = A2:A4 纵向合并
     *                      header_rows 表头行数（默认 1；两行表头的交叉表用 2）
     *                      cell_styles 的键为 1-based 的 "行,列"，值为语义标记名（未知标记静默忽略）
     * @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'] ?? [])),
                'merges'      => self::normalizeMerges((array)($sh['merges'] ?? []), count($rows), self::maxCols($rows)),
                'header_rows' => max(1, (int)($sh['header_rows'] ?? 1)),
                'cell_styles' => self::normalizeCellStyles((array)($sh['cell_styles'] ?? [])),
            ];
        }
        if ($w->sheets === []) {
            // 保底：至少输出一张空表
            $w->sheets[] = ['name' => 'Sheet1', 'rows' => [['']], 'widths' => [], 'merges' => [], 'header_rows' => 1, 'cell_styles' => []];
        }
        return $w->build();
    }

    /**
     * 归一化单元格样式表：键 "行,列"（1-based）=> 样式索引；未知标记直接丢弃。
     *
     * @param array $raw ['3,5' => 'red', [4,5] => 'green', ...]（两种写法都接受）
     * @return array<string,int>
     */
    private static function normalizeCellStyles(array $raw): array
    {
        $out = [];
        foreach ($raw as $k => $mark) {
            if (is_array($k) && count($k) >= 2) {
                $key = ((int)$k[0]) . ',' . ((int)$k[1]);
            } else {
                $key = (string)$k;
                if (!preg_match('/^\s*(\d+)\s*,\s*(\d+)\s*$/', $key, $m)) {
                    continue;
                }
                $key = ((int)$m[1]) . ',' . ((int)$m[2]);
            }
            $idx = self::MARK_STYLES[(string)$mark] ?? null;
            if ($idx === null) {
                continue; // 未知标记：不写样式，不报错
            }
            [$r, $c] = array_map('intval', explode(',', $key));
            if ($r < 1 || $c < 1) {
                continue;
            }
            $out[$key] = $idx;
        }
        return $out;
    }

    /** 二维表最大列数（至少 1） */
    private static function maxCols(array $rows): int
    {
        $max = 1;
        foreach ($rows as $r) {
            $max = max($max, count((array)$r));
        }
        return $max;
    }

    /**
     * 归一化合并区间：过滤非法 / 退化（单格）区间，并按行列排序，保证 Excel 不报修复提示。
     *
     * @param array $raw  [[r1,c1,r2,c2], ...] 1-based
     * @return array<int,array{0:int,1:int,2:int,3:int}>
     */
    private static function normalizeMerges(array $raw, int $maxRow, int $maxCol): array
    {
        $out = [];
        foreach ($raw as $m) {
            if (!is_array($m) || count($m) < 4) {
                continue;
            }
            $r1 = (int)$m[0]; $c1 = (int)$m[1]; $r2 = (int)$m[2]; $c2 = (int)$m[3];
            if ($r1 > $r2) { [$r1, $r2] = [$r2, $r1]; }
            if ($c1 > $c2) { [$c1, $c2] = [$c2, $c1]; }
            if ($r1 < 1 || $c1 < 1 || $r2 > $maxRow || $c2 > $maxCol) {
                continue; // 越界丢弃
            }
            if ($r1 === $r2 && $c1 === $c2) {
                continue; // 单格无需合并
            }
            $out[] = [$r1, $c1, $r2, $c2];
        }
        usort($out, static function (array $a, array $b): int {
            return [$a[0], $a[1], $a[2], $a[3]] <=> [$b[0], $b[1], $b[2], $b[3]];
        });
        return $out;
    }

    /* ---------------- 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'],
                $sh['merges'] ?? [],
                (int)($sh['header_rows'] ?? 1),
                (array)($sh['cell_styles'] ?? [])
            );
            $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 = [], array $merges = [], int $headerRows = 1, array $cellStyles = []): 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"/>';
        }

        // 合并区域的非首格不能带值（否则 Excel 打开会提示"修复"），
        // 但仍要写成「空值 + 带样式的格子」，否则合并区域的边框会在 Excel 里缺边。
        $swallowed = [];
        foreach ($merges as $m) {
            for ($r = $m[0]; $r <= $m[2]; $r++) {
                for ($c = $m[1]; $c <= $m[3]; $c++) {
                    if ($r === $m[0] && $c === $m[1]) {
                        continue;
                    }
                    $swallowed[$r][$c] = true;
                }
            }
        }

        $data = '';
        for ($r = 1; $r <= $maxRow; $r++) {
            $baseStyle = $r <= $headerRows ? self::S_HEADER : self::S_TEXT;
            $line = '';
            $has = false;
            for ($c = 1; $c <= $maxCol; $c++) {
                $sw = isset($swallowed[$r][$c]);
                if (!isset($cells[$r][$c]) && !$sw) {
                    continue;
                }
                $has = true;
                $ref = self::colName($c) . $r;
                // 单元格级标记（红字 / 绿底）优先；合并区间跟随左上角首格的样式，
                // 否则"合并成一格但只有左边半截有底色"会很难看。
                $mark = $cellStyles[$r . ',' . $c] ?? null;
                if ($mark === null && $sw) {
                    foreach ($merges as $m) {
                        if ($r >= $m[0] && $r <= $m[2] && $c >= $m[1] && $c <= $m[3]) {
                            $mark = $cellStyles[$m[0] . ',' . $m[1]] ?? null;
                            break;
                        }
                    }
                }
                $style = ($mark !== null) ? (int)$mark : $baseStyle;
                if ($sw) {
                    $line .= '<c r="' . $ref . '" s="' . $style . '"/>';
                } else {
                    $line .= '<c r="' . $ref . '" s="' . $style . '" t="s"><v>' . $cells[$r][$c] . '</v></c>';
                }
            }
            if (!$has) {
                continue;
            }
            $data .= '<row r="' . $r . '" spans="1:' . $maxCol . '">' . $line . '</row>';
        }

        $mergeXml = '';
        if ($merges !== []) {
            $mergeXml = '<mergeCells count="' . count($merges) . '">';
            foreach ($merges as $m) {
                $mergeXml .= '<mergeCell ref="' . self::colName($m[1]) . $m[0] . ':' . self::colName($m[3]) . $m[2] . '"/>';
            }
            $mergeXml .= '</mergeCells>';
        }

        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>' .
            $mergeXml .
            '</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>' .
            // 字体：0 常规 / 1 加粗（表头）/ 2 红色（最高分）/ 3 加粗绿字
            '<fonts count="3">' .
            '<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>' .
            '<font><sz val="11"/><color rgb="FFD0021B"/><name val="宋体"/><charset val="134"/></font>' .
            '</fonts>' .
            // 填充：0 none / 1 gray125（Excel 约定占位）/ 2 合格绿底 / 3 表头绿底
            // 绿色沿用导出截图里的浅绿 (#63C384 系)：既醒目又不至于盖住黑色文字
            '<fills count="4">' .
            '<fill><patternFill patternType="none"/></fill>' .
            '<fill><patternFill patternType="gray125"/></fill>' .
            '<fill><patternFill patternType="solid"><fgColor rgb="FF63C384"/><bgColor indexed="64"/></patternFill></fill>' .
            '<fill><patternFill patternType="solid"><fgColor rgb="FF63C384"/><bgColor indexed="64"/></patternFill></fill>' .
            '</fills>' .
            // 0 = 无边框，1 = 细灰边框（表格统一描边，打印/截图都清晰）
            '<borders count="2">' .
            '<border><left/><right/><top/><bottom/><diagonal/></border>' .
            '<border>' .
            '<left style="thin"><color rgb="FF808080"/></left>' .
            '<right style="thin"><color rgb="FF808080"/></right>' .
            '<top style="thin"><color rgb="FF808080"/></top>' .
            '<bottom style="thin"><color rgb="FF808080"/></bottom>' .
            '<diagonal/></border>' .
            '</borders>' .
            '<cellStyleXfs count="1"><xf numFmtId="0" fontId="0" fillId="0" borderId="0"/></cellStyleXfs>' .
            '<cellXfs count="6">' .
            '<xf numFmtId="0" fontId="0" fillId="0" borderId="0" xfId="0"/>' .                                          // 0 常规
            '<xf numFmtId="0" fontId="1" fillId="0" borderId="1" xfId="0" applyFont="1" applyBorder="1"><alignment horizontal="center" vertical="center"/></xf>' . // 1 表头
            '<xf numFmtId="49" fontId="0" fillId="0" borderId="1" xfId="0" applyNumberFormat="1" applyBorder="1"><alignment vertical="center"/></xf>' .             // 2 文本
            '<xf numFmtId="49" fontId="2" fillId="0" borderId="1" xfId="0" applyNumberFormat="1" applyFont="1" applyBorder="1"><alignment horizontal="center" vertical="center"/></xf>' . // 3 红字（最高分）
            '<xf numFmtId="49" fontId="0" fillId="2" borderId="1" xfId="0" applyNumberFormat="1" applyFill="1" applyBorder="1"><alignment horizontal="center" vertical="center"/></xf>' . // 4 绿底（合格次数达标）
            '<xf numFmtId="0" fontId="1" fillId="3" borderId="1" xfId="0" applyFont="1" applyFill="1" applyBorder="1"><alignment horizontal="center" vertical="center"/></xf>' .          // 5 表头绿底
            '</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';
    }
}