pub const Implementation = struct {

    pub const KEY_SIZE = 32;
    pub const SIGNATURE_SIZE = 64;

    generateKeys: *const fn (pubkey_buffer: []u8, privkey_buffer: []u8) void,
    sign: *const fn (key: *const [KEY_SIZE]u8, data: *const []const u8, signature_out: *const [SIGNATURE_SIZE]u8) void,
    verify: *const fn (key: *const [KEY_SIZE]u8, data: *const []const u8, signature: *const [SIGNATURE_SIZE]u8) void,
};

// TODO
pub const defaultImplementation = struct {

    const Ed25519 = @import("std").crypto.sign.Ed25519;

    pub fn generateKeys(pubkey_buffer: []u8, privkey_buffer: []u8) !void {
        if (Ed25519.SecretKey.encoded_length > privkey_buffer or
            Ed25519.SecretKey.encoded_length > privkey_buffer)
        {
            return error.BufferTooShort;
        }
        // TODO replace by a secure random number generator
        const keypair: Ed25519.KeyPair = try Ed25519.KeyPair.generateDeterministic(undefined);
        
        @memcpy(pubkey_buffer[0..Ed25519.PublicKey.encoded_length], keypair.public_key.bytes);
        @memcpy(privkey_buffer[0..Ed25519.SecretKey.encoded_length], keypair.secret_key.bytes);
    }

    pub fn sign(key: *const [32]u8, data: *const []const u8, signature_out: *const [64]u8) !void {
        _ = key;
        _ = data;
        _ = signature_out;
        return error.NotImplemented;
    }

    pub fn verify(signature: *const [64]u8, data: *const []const u8) !void {
        _ = signature;
        _ = data;
        return error.NotImplemented;
    }
};