Lesstime/frontend/modules/reporting/composables/useCsvExport.ts

export type CsvColumn<T> = {
    header: string
    value: (row: T) => string | number
}

/** Escapes a single CSV cell (quotes wrapping + doubled inner quotes). */
function escapeCell(value: string | number): string {
    const str = String(value ?? '')
    if (/[",\n;]/.test(str)) {
        return `"${str.replace(/"/g, '""')}"`
    }
    return str
}

export function useCsvExport() {
    /** Builds a CSV string from rows + column definitions (semicolon separator, FR-friendly). */
    function toCsv<T>(rows: T[], columns: CsvColumn<T>[]): string {
        const header = columns.map(c => escapeCell(c.header)).join(';')
        const lines = rows.map(row =>
            columns.map(c => escapeCell(c.value(row))).join(';'),
        )
        return [header, ...lines].join('\n')
    }

    /** Triggers a browser download of the given CSV content. */
    function downloadCsv<T>(filename: string, rows: T[], columns: CsvColumn<T>[]): void {
        if (typeof window === 'undefined') {
            return
        }
        const csv = toCsv(rows, columns)
        // Prepend BOM so Excel detects UTF-8.
        const blob = new Blob([`${csv}`], { type: 'text/csv;charset=utf-8;' })
        const url = URL.createObjectURL(blob)
        const link = document.createElement('a')
        link.href = url
        link.download = filename.endsWith('.csv') ? filename : `${filename}.csv`
        document.body.appendChild(link)
        link.click()
        document.body.removeChild(link)
        URL.revokeObjectURL(url)
    }

    return { toCsv, downloadCsv }
}