import * as XLSX from "xlsx";
import { replicateTranslateBatch } from "../replicate-translate";

export type SheetColumnInfo = {
    sheetName: string;
    columns: string[]; // header names or A, B, C...
};

export type ColumnSelection = {
    sheetName: string;
    columnIndices: number[]; // 0-based column indices to translate
};

/**
 * Parse an Excel/CSV buffer and return sheet/column metadata for column selection UI.
 */
export function getExcelColumns(buffer: Buffer, filename: string): SheetColumnInfo[] {
    const wb = XLSX.read(buffer, { type: "buffer" });
    return wb.SheetNames.map(sheetName => {
        const ws = wb.Sheets[sheetName];
        const range = XLSX.utils.decode_range(ws["!ref"] ?? "A1");
        const columns: string[] = [];
        for (let c = range.s.c; c <= range.e.c; c++) {
            // Try to get header from first row
            const cellAddr = XLSX.utils.encode_cell({ r: 0, c });
            const cell = ws[cellAddr];
            const header = cell && cell.v != null ? String(cell.v) : XLSX.utils.encode_col(c);
            columns.push(header);
        }
        return { sheetName, columns };
    });
}

/**
 * Translate selected columns in an Excel buffer. Returns translated buffer.
 * columnSelections: array of {sheetName, columnIndices}
 * If columnSelections is empty, all text columns are translated.
 */
export async function translateExcel(
    buffer: Buffer,
    targetLanguage: string,
    columnSelections: ColumnSelection[]
): Promise<Buffer> {
    const wb = XLSX.read(buffer, { type: "buffer", cellStyles: true, cellNF: true });

    for (const sheet of wb.SheetNames) {
        const ws = wb.Sheets[sheet];
        if (!ws["!ref"]) continue;

        const range = XLSX.utils.decode_range(ws["!ref"]);
        const selection = columnSelections.find(s => s.sheetName === sheet);
        const columnsToTranslate = selection
            ? selection.columnIndices
            : Array.from({ length: range.e.c - range.s.c + 1 }, (_, i) => i + range.s.c);

        // Collect all text cells for batch translation
        type CellRef = { addr: string; text: string };
        const cellRefs: CellRef[] = [];

        for (const colIdx of columnsToTranslate) {
            // Start from row 1 to skip headers (row 0)
            for (let r = range.s.r + 1; r <= range.e.r; r++) {
                const addr = XLSX.utils.encode_cell({ r, c: colIdx });
                const cell = ws[addr];
                if (cell && cell.t === "s" && typeof cell.v === "string" && cell.v.trim()) {
                    cellRefs.push({ addr, text: cell.v });
                }
            }
        }

        if (cellRefs.length === 0) continue;

        // Translate in batches of 50
        const BATCH_SIZE = 50;
        for (let i = 0; i < cellRefs.length; i += BATCH_SIZE) {
            const batch = cellRefs.slice(i, i + BATCH_SIZE);
            const translations = await replicateTranslateBatch(
                batch.map(c => c.text),
                targetLanguage
            );
            batch.forEach((cellRef, idx) => {
                const cell = ws[cellRef.addr];
                if (cell) {
                    cell.v = translations[idx];
                    if (cell.h) cell.h = translations[idx];
                    if (cell.r) cell.r = undefined;
                    if (cell.w) cell.w = translations[idx];
                }
            });
        }
    }

    const out = XLSX.write(wb, { type: "buffer", bookType: "xlsx" });
    return Buffer.from(out);
}