// export.js — CSV download of the current table view.
//
// Exports what the user sees: filter + sort applied, columns in the
// order declared by the spec. Values pass through util.formatCell so
// date / number / boolean cells match their on-screen rendering.
// RFC 4180 quoting (double-quote any cell with a comma, newline, or
// quote; escape inner quotes by doubling). UTF-8 BOM prepended so
// Excel detects the encoding without a manual import-wizard step.

(function (app) {
    'use strict';

    function csvEscape(value) {
        if (value == null) return '';
        const str = String(value);
        if (/[",\r\n]/.test(str)) {
            return '"' + str.replace(/"/g, '""') + '"';
        }
        return str;
    }

    function buildCsv(rows, columns, util) {
        const lines = [];
        lines.push(columns.map(function (c) {
            return csvEscape(c.title || c.field || '');
        }).join(','));
        for (let i = 0; i < rows.length; i++) {
            const row = rows[i];
            const cells = columns.map(function (c) {
                const raw = util.resolveField(row.data, c.field);
                return csvEscape(util.formatCell(raw, c.format));
            });
            lines.push(cells.join(','));
        }
        return lines.join('\r\n') + '\r\n';
    }

    function suggestFilename() {
        const titleEl = document.getElementById('table-title');
        const raw = (titleEl && titleEl.textContent) ? titleEl.textContent : 'table';
        const base = raw.toLowerCase()
            .replace(/[^a-z0-9]+/g, '-')
            .replace(/^-+|-+$/g, '') || 'table';
        const stamp = new Date().toISOString().slice(0, 10);
        return base + '-' + stamp + '.csv';
    }

    function download(csv, filename) {
        const blob = new Blob(['' + csv], { type: 'text/csv;charset=utf-8' });
        const url = URL.createObjectURL(blob);
        const a = document.createElement('a');
        a.href = url;
        a.download = filename;
        document.body.appendChild(a);
        a.click();
        document.body.removeChild(a);
        setTimeout(function () { URL.revokeObjectURL(url); }, 1000);
    }

    function invoke() {
        const ctx = app.context || {};
        const columns = Array.isArray(ctx.columns) ? ctx.columns : [];
        if (columns.length === 0) {
            return;
        }
        const state = app.state;
        const util = app.modules.util;
        const filtered = app.modules.filters.apply(state.rows, columns, state.filter, util.resolveField);
        const sorted = app.modules.sort.apply(filtered, state.sort, columns, util);
        const csv = buildCsv(sorted, columns, util);
        download(csv, suggestFilename());
    }

    app.modules.exportCsv = {
        invoke: invoke,
        buildCsv: buildCsv,
        csvEscape: csvEscape
    };
})(window.tablesApp);