LingvAI/pages/api/translate/document.ts

import { NextApiHandler } from "next";
import formidable, { File, Fields, Files } from "formidable";
import fs from "fs";
import path from "path";
import { translateExcel, getExcelColumns, ColumnSelection } from "@utils/document-processors/excel";
import { translateDocx } from "@utils/document-processors/docx";
import { translatePdf } from "@utils/document-processors/pdf";
import { readSettings } from "@utils/settings-store";

export const config = {
    api: {
        bodyParser: false,
        responseLimit: "50mb"
    }
};

type ParsedForm = {
    fields: Fields;
    files: Files;
};

function parseForm(req: Parameters<NextApiHandler>[0]): Promise<ParsedForm> {
    const form = formidable({ maxFileSize: 50 * 1024 * 1024 }); // 50 MB
    return new Promise((resolve, reject) => {
        form.parse(req, (err, fields, files) => {
            if (err) reject(err);
            else resolve({ fields, files });
        });
    });
}

function getFileBuffer(file: File): Buffer {
    return fs.readFileSync(file.filepath);
}

function getField(fields: Fields, key: string): string | undefined {
    const val = fields[key];
    return Array.isArray(val) ? val[0] : (val as string | undefined);
}

const handler: NextApiHandler = async (req, res) => {
    if (req.method !== "POST") {
        res.setHeader("Allow", ["POST"]);
        return res.status(405).json({ error: "Method Not Allowed" });
    }

    const settings = readSettings();
    if (!settings.replicateEnabled) {
        return res.status(503).json({ error: "Replicate translation is not enabled. Configure it in the admin panel." });
    }

    let parsed: ParsedForm;
    try {
        parsed = await parseForm(req);
    } catch (err) {
        return res.status(400).json({ error: "Failed to parse upload" });
    }

    const { fields, files } = parsed;
    const fileEntry = files["file"];
    const file = Array.isArray(fileEntry) ? fileEntry[0] : fileEntry;

    if (!file) {
        return res.status(400).json({ error: "No file uploaded" });
    }

    const targetLanguage = getField(fields, "targetLanguage") ?? "en";
    const sourceLanguage = getField(fields, "sourceLanguage");
    const action = getField(fields, "action") ?? "translate";
    const columnSelectionsRaw = getField(fields, "columnSelections");

    const filename = file.originalFilename ?? file.newFilename ?? "file";
    const ext = path.extname(filename).toLowerCase();
    const buffer = getFileBuffer(file);

    try {
        // Action: getColumns - return column info for Excel files
        if (action === "getColumns") {
            if (![".xlsx", ".xls", ".csv"].includes(ext)) {
                return res.status(400).json({ error: "Column selection only supported for Excel/CSV files" });
            }
            const columns = getExcelColumns(buffer, filename);
            return res.status(200).json({ columns });
        }

        // Action: translate
        let outBuffer: Buffer;
        let outMime: string;
        let outFilename: string;

        if ([".xlsx", ".xls"].includes(ext)) {
            let columnSelections: ColumnSelection[] = [];
            if (columnSelectionsRaw) {
                try {
                    columnSelections = JSON.parse(columnSelectionsRaw);
                } catch { /* use empty = translate all */ }
            }
            outBuffer = await translateExcel(buffer, targetLanguage, columnSelections);
            outMime = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            outFilename = filename.replace(ext, `_${targetLanguage}${ext}`);
        } else if (ext === ".csv") {
            // Treat CSV as Excel
            let columnSelections: ColumnSelection[] = [];
            if (columnSelectionsRaw) {
                try {
                    columnSelections = JSON.parse(columnSelectionsRaw);
                } catch { /* use empty = translate all */ }
            }
            outBuffer = await translateExcel(buffer, targetLanguage, columnSelections);
            outMime = "text/csv";
            outFilename = filename.replace(ext, `_${targetLanguage}${ext}`);
        } else if (ext === ".docx") {
            outBuffer = await translateDocx(buffer, targetLanguage);
            outMime = "application/vnd.openxmlformats-officedocument.wordprocessingml.document";
            outFilename = filename.replace(ext, `_${targetLanguage}${ext}`);
        } else if (ext === ".pdf") {
            outBuffer = await translatePdf(buffer, targetLanguage, sourceLanguage);
            outMime = "application/pdf";
            outFilename = filename.replace(ext, `_${targetLanguage}${ext}`);
        } else {
            return res.status(400).json({
                error: `Unsupported file type: ${ext}. Supported: .pdf, .docx, .xlsx, .xls, .csv`
            });
        }

        res.setHeader("Content-Type", outMime);
        res.setHeader("Content-Disposition", `attachment; filename="${outFilename}"`);
        res.setHeader("Content-Length", outBuffer.length);
        return res.status(200).send(outBuffer);
    } catch (err) {
        const msg = err instanceof Error ? err.message : "Translation failed";
        return res.status(500).json({ error: msg });
    }
};

export default handler;