docs.sheetjs.com/docz/static/duk/main.zig

const std = @import("std");
const duktape = @cImport({
    @cInclude("duktape.h");
});
// SheetJS scripts embedded at comptime
const shim = @embedFile("shim.min.js");
const xlsx = @embedFile("xlsx.full.min.js");

pub fn main() !void {
    // initialize duktape
    const ctx = duktape.duk_create_heap(null, null, null, null, null);
    defer _ = duktape.duk_destroy_heap(ctx);

    // load SheetJS scripts
    _ = duktape.duk_peval_string(ctx, shim);
    _ = duktape.duk_peval_string(ctx, xlsx);

    // display version number
    _ = duktape.duk_peval_string(ctx, "XLSX.version");
    const sum = duktape.duk_get_string(ctx, -1);
    std.debug.print("SheetJS Version {s}\n", .{sum});
    duktape.duk_pop(ctx);

    // create allocator
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    var alloc = gpa.allocator();

    // determine file to read
    var args = try std.process.argsWithAllocator(alloc);
    defer args.deinit();
    _ = args.next();
    const path = args.next();
    if (path == null) {
        std.debug.print("Must specify a filename!", .{});
        return;
    }
    std.debug.print("Reading from {s}\n", .{path.?});

    // read file
    const file = try std.fs.cwd().readFileAlloc(alloc, path.?, std.math.maxInt(usize));
    defer alloc.free(file);
    std.debug.print("Size: {} bytes\n", .{file.len});

    // load into duktape
    _ = duktape.duk_push_buffer_raw(ctx, 0, duktape.DUK_BUF_FLAG_DYNAMIC | duktape.DUK_BUF_FLAG_EXTERNAL);
    duktape.duk_config_buffer(ctx, -1, file.ptr, file.len);
    _ = duktape.duk_put_global_string(ctx, "buf");
    _ = duktape.duk_eval_raw(ctx, "workbook = XLSX.read(buf.slice(0, buf.length), {type:'buffer'});", 0, duktape.DUK_COMPILE_EVAL | duktape.DUK_COMPILE_NOSOURCE | duktape.DUK_COMPILE_STRLEN | duktape.DUK_COMPILE_NORESULT | duktape.DUK_COMPILE_NOFILENAME);

    // display CSV of first worksheet
    _ = duktape.duk_peval_string(ctx, "XLSX.utils.sheet_to_csv(workbook.Sheets[workbook.SheetNames[0]])");
    const csv = duktape.duk_get_string(ctx, -1);
    std.debug.print("{s}\n", .{csv});
    duktape.duk_pop(ctx);

    // convert to XLSX
    _ = duktape.duk_eval_raw(ctx, "XLSX.write(workbook, {type:'array', bookType:'xlsx'})", 0, duktape.DUK_COMPILE_EVAL | duktape.DUK_COMPILE_NOSOURCE | duktape.DUK_COMPILE_STRLEN | duktape.DUK_COMPILE_NOFILENAME);
    var sz: usize = 0;
    const c_ptr: *anyopaque = duktape.duk_get_buffer_data(ctx, -1, &sz).?;

    // generate zig slice from C pointer + length
    const slc: []u8 = @as([*]u8, @ptrCast(c_ptr))[0..sz];

    // write to file
    _ = try std.fs.cwd().writeFile(.{ .sub_path = "sheetjs.zig.xlsx", .data = slc });
}