//! system/services/fat/fat-test — a client that proves the FAT mount end to end:
//! it waits for the fat server to mount the USB volume at /mnt/usb, lists the
//! root directory through the VFS (which routes /mnt/usb to the fat backend), and
//! reads a known file off it. Shipped in the initial_ramdisk; the `fat-mount`
//! kernel test spawns it alongside init.

const std = @import("std");
const runtime = @import("runtime");
const fs = runtime.fs;

fn writeLine(comptime fmt: []const u8, arguments: anytype) void {
    var line: [128]u8 = undefined;
    _ = runtime.system.write(std.fmt.bufPrint(&line, fmt, arguments) catch return);
}

pub fn main(init: runtime.process.Init) void {
    _ = init;

    // Wait for /mnt/usb to be mounted — the fat server races us at boot (it must
    // bring up the whole USB storage chain first).
    var opened: ?fs.Directory = null;
    var tries: u32 = 0;
    while (opened == null and tries < 1400) : (tries += 1) {
        opened = fs.openDirectory("/mnt/usb");
        if (opened == null) runtime.system.sleep(50);
    }
    var dir = opened orelse {
        _ = runtime.system.write("fat-test: /mnt/usb never became available\n");
        return;
    };

    var count: u32 = 0;
    var entry: fs.Entry = .{};
    while (dir.next(&entry)) {
        writeLine("fat-test: entry '{s}' kind={d} size={d}\n", .{ entry.name(), @intFromEnum(entry.kind), entry.size });
        count += 1;
        if (count > 32) break;
    }
    dir.close();
    writeLine("fat-test: listed {d} entries\n", .{count});

    // Read a known file off the boot volume through the mount (best effort): the
    // kernel image is an ELF, so its first bytes are the ELF magic.
    if (fs.open("/mnt/usb/system/kernel", .{})) |opened_file| {
        var file = opened_file;
        var magic: [4]u8 = undefined;
        const n = file.read(&magic) orelse 0;
        file.close();
        if (n == 4 and magic[0] == 0x7F and magic[1] == 'E' and magic[2] == 'L' and magic[3] == 'F') {
            _ = runtime.system.write("fat-test: read /mnt/usb/system/kernel ELF magic ok\n");
        } else {
            writeLine("fat-test: /mnt/usb/system/kernel read {d} bytes (not ELF magic)\n", .{n});
        }
    }

    if (count > 0) {
        while (true) {
            _ = runtime.system.write("fat-test: ok\n");
            runtime.system.sleep(1000);
        }
    }
    _ = runtime.system.write("fat-test: root listing was empty\n");
}

pub const panic = runtime.panic;
comptime {
    _ = &runtime.start._start;
}