// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

// The wire level benchmarks: the server handler and the client library
// over a loopback connection, so one operation carries the whole stack,
// RPC and XDR and sessions included, on top of the backend.
package nfs4server_test

import (
	"context"
	"net"
	"os"
	"path/filepath"
	"testing"

	"sourcedock.dev/petrbalvin/nfs/internal/nfs4"
	"sourcedock.dev/petrbalvin/nfs/internal/nfs4server"
	"sourcedock.dev/petrbalvin/nfs/internal/nfsclient"
	"sourcedock.dev/petrbalvin/nfs/internal/nfsfs"
	"sourcedock.dev/petrbalvin/nfs/internal/server"
	"sourcedock.dev/petrbalvin/nfs/internal/xdr"
)

const wireChunk = 64 << 10

// benchWire serves one export over loopback, dials the client library at
// it and returns the client and the handle of one regular file of the
// given size. Setup runs once, outside the measured region.
func benchWire(b *testing.B, fileSize int) (*nfsclient.Client, []byte) {
	b.Helper()
	root := b.TempDir()
	backend, err := nfsfs.NewLocal(root)
	if err != nil {
		b.Fatalf("NewLocal: %v", err)
	}
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		b.Fatalf("Listen: %v", err)
	}
	ctx, stop := context.WithCancel(context.Background())
	srv := &server.Server{Handle: (&nfs4server.Handler{FS: backend}).HandleConn}
	go func() { _ = srv.Serve(ctx, ln) }()
	b.Cleanup(stop)

	name := "benchfile"
	if fileSize > 0 {
		p := filepath.Join(root, name)
		buf := make([]byte, 1<<20)
		for i := range buf {
			buf[i] = byte(i)
		}
		f, err := os.Create(p)
		if err != nil {
			b.Fatalf("Create: %v", err)
		}
		for written := 0; written < fileSize; written += len(buf) {
			if _, err := f.Write(buf); err != nil {
				b.Fatalf("Write: %v", err)
			}
		}
		if err := f.Close(); err != nil {
			b.Fatalf("Close: %v", err)
		}
	}
	cl, err := nfsclient.Dial(ln.Addr().String())
	if err != nil {
		b.Fatalf("Dial: %v", err)
	}
	b.Cleanup(func() { _ = cl.Close() })
	if err := cl.Establish("bench"); err != nil {
		b.Fatalf("Establish: %v", err)
	}
	res, bodies, err := cl.Compound("bench-lookup", [][]byte{
		nfs4.AppendPutRootfh(nil),
		nfs4.AppendLookup(nil, name),
		nfs4.AppendGetfh(nil),
	})
	if err != nil {
		b.Fatalf("Compound: %v", err)
	}
	if res.Status != nfs4.ErrOK {
		b.Fatalf("lookup status %d", res.Status)
	}
	fh, err := xdr.NewDecoder(bodies[len(bodies)-1]).VarOpaque()
	if err != nil {
		b.Fatalf("decode fh: %v", err)
	}
	return cl, fh
}

// compound runs one COMPOUND and requires NFS4ERR_SUCCESS of it.
func compound(b *testing.B, cl *nfsclient.Client, tag string, ops [][]byte) [][]byte {
	b.Helper()
	res, bodies, err := cl.Compound(tag, ops)
	if err != nil {
		b.Fatalf("%s: %v", tag, err)
	}
	if res.Status != nfs4.ErrOK {
		b.Fatalf("%s: nfs status %d", tag, res.Status)
	}
	return bodies
}

// BenchmarkWireRead64K reads 64 KiB per COMPOUND from a 64 MiB file over
// the loopback connection, cycling through the offsets.
func BenchmarkWireRead64K(b *testing.B) {
	cl, fh := benchWire(b, 64<<20)
	off := uint64(0)
	b.SetBytes(wireChunk)
	b.ResetTimer()
	for b.Loop() {
		bodies := compound(b, cl, "bench-read", [][]byte{
			nfs4.AppendPutfh(nil, fh),
			nfs4.AppendReadArgs(nil, nfs4.Stateid{}, off, wireChunk),
		})
		d := xdr.NewDecoder(bodies[len(bodies)-1])
		if _, err := d.Bool(); err != nil {
			b.Fatalf("decode eof: %v", err)
		}
		if _, err := d.VarOpaque(); err != nil {
			b.Fatalf("decode data: %v", err)
		}
		off += wireChunk
		if off > 64<<20-wireChunk {
			off = 0
		}
	}
}

// BenchmarkWireWrite64K writes 64 KiB per COMPOUND to a preallocated
// 64 MiB file, cycling through the offsets, one open around the run.
func BenchmarkWireWrite64K(b *testing.B) {
	cl, _ := benchWire(b, 64<<20)
	bodies := compound(b, cl, "bench-open", [][]byte{
		nfs4.AppendPutRootfh(nil),
		nfs4.AppendOpenArgs(nil, 0, []byte("bench"), nfs4.ShareAccessBoth, 0,
			true, 0o644, "benchfile"),
		nfs4.AppendGetfh(nil),
	})
	fh, err := xdr.NewDecoder(bodies[len(bodies)-1]).VarOpaque()
	if err != nil {
		b.Fatalf("decode fh: %v", err)
	}
	var st nfs4.Stateid
	stateBody := bodies[len(bodies)-2]
	if len(stateBody) < len(st) {
		b.Fatalf("open result carries %d bytes of stateid", len(stateBody))
	}
	copy(st[:], stateBody)
	buf := make([]byte, wireChunk)
	off := uint64(0)
	b.SetBytes(wireChunk)
	b.ResetTimer()
	for b.Loop() {
		compound(b, cl, "bench-write", [][]byte{
			nfs4.AppendPutfh(nil, fh),
			nfs4.AppendWriteArgs(nil, st, off, nfs4.StableFileSync, buf),
		})
		off += wireChunk
		if off > 64<<20-wireChunk {
			off = 0
		}
	}
	b.StopTimer()
	compound(b, cl, "bench-close", [][]byte{
		nfs4.AppendPutfh(nil, fh),
		nfs4.AppendCloseArgs(nil, st),
	})
}

// BenchmarkWireGetattr asks the attributes of one file per COMPOUND.
func BenchmarkWireGetattr(b *testing.B) {
	cl, fh := benchWire(b, 1<<20)
	request := nfs4.OfBits(nfs4.AttrType, nfs4.AttrSize, nfs4.AttrMode)
	b.ResetTimer()
	for b.Loop() {
		bodies := compound(b, cl, "bench-getattr", [][]byte{
			nfs4.AppendPutfh(nil, fh),
			nfs4.AppendGetattr(nil, request),
		})
		d := xdr.NewDecoder(bodies[len(bodies)-1])
		if _, err := nfs4.ReadBitmap(d); err != nil {
			b.Fatalf("decode bitmap: %v", err)
		}
		if _, err := d.VarOpaque(); err != nil {
			b.Fatalf("decode attrs: %v", err)
		}
	}
}

// BenchmarkWireLookup resolves one name under the root per COMPOUND.
func BenchmarkWireLookup(b *testing.B) {
	cl, _ := benchWire(b, 1<<20)
	b.ResetTimer()
	for b.Loop() {
		compound(b, cl, "bench-lookup", [][]byte{
			nfs4.AppendPutRootfh(nil),
			nfs4.AppendLookup(nil, "benchfile"),
			nfs4.AppendGetfh(nil),
		})
	}
}