// Copyright 2024 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package sync

import (
	"testing"

	"github.com/ethereum/go-ethereum/beacon/light/request"
	"github.com/ethereum/go-ethereum/beacon/types"
)

func TestCheckpointInit(t *testing.T) {
	chain := &TestCommitteeChain{}
	checkpoint := &types.BootstrapData{Header: types.Header{Slot: 0x2000*4 + 0x1000}} // period 4
	checkpointHash := checkpoint.Header.Hash()
	chkInit := NewCheckpointInit(chain, checkpointHash)
	ts := NewTestScheduler(t, chkInit)
	// add 2 servers
	ts.AddServer(testServer1, 1)
	ts.AddServer(testServer2, 1)

	// expect bootstrap request to server 1
	ts.Run(1, testServer1, ReqCheckpointData(checkpointHash))

	// server 1 times out; expect request to server 2
	ts.RequestEvent(request.EvTimeout, ts.Request(1, 1), nil)
	ts.Run(2, testServer2, ReqCheckpointData(checkpointHash))

	// invalid response from server 2; expect init state to still be false
	ts.RequestEvent(request.EvResponse, ts.Request(2, 1), &types.BootstrapData{Header: types.Header{Slot: 123456}})
	ts.ExpFail(testServer2)
	ts.Run(3)
	chain.ExpInit(t, false)

	// server 1 fails (hard timeout)
	ts.RequestEvent(request.EvFail, ts.Request(1, 1), nil)
	ts.Run(4)
	chain.ExpInit(t, false)

	// server 3 is registered; expect bootstrap request to server 3
	ts.AddServer(testServer3, 1)
	ts.Run(5, testServer3, ReqCheckpointData(checkpointHash))

	// valid response from server 3; expect chain to be initialized
	ts.RequestEvent(request.EvResponse, ts.Request(5, 1), checkpoint)
	ts.Run(6)
	chain.ExpInit(t, true)
}

func TestUpdateSyncParallel(t *testing.T) {
	chain := &TestCommitteeChain{}
	chain.SetNextSyncPeriod(0)
	updateSync := NewForwardUpdateSync(chain)
	ts := NewTestScheduler(t, updateSync)
	// add 2 servers, head at period 100; allow 3-3 parallel requests for each
	ts.AddServer(testServer1, 3)
	ts.ServerEvent(EvNewSignedHead, testServer1, types.SignedHeader{SignatureSlot: 0x2000*100 + 0x1000})
	ts.AddServer(testServer2, 3)
	ts.ServerEvent(EvNewSignedHead, testServer2, types.SignedHeader{SignatureSlot: 0x2000*100 + 0x1000})

	// expect 6 requests to be sent
	ts.Run(1,
		testServer1, ReqUpdates{FirstPeriod: 0, Count: 8},
		testServer1, ReqUpdates{FirstPeriod: 8, Count: 8},
		testServer1, ReqUpdates{FirstPeriod: 16, Count: 8},
		testServer2, ReqUpdates{FirstPeriod: 24, Count: 8},
		testServer2, ReqUpdates{FirstPeriod: 32, Count: 8},
		testServer2, ReqUpdates{FirstPeriod: 40, Count: 8})

	// valid response to request 1; expect 8 periods synced and a new request started
	ts.RequestEvent(request.EvResponse, ts.Request(1, 1), testRespUpdate(ts.Request(1, 1)))
	ts.AddAllowance(testServer1, 1)
	ts.Run(2, testServer1, ReqUpdates{FirstPeriod: 48, Count: 8})
	chain.ExpNextSyncPeriod(t, 8)

	// valid response to requests 4 and 5
	ts.RequestEvent(request.EvResponse, ts.Request(1, 4), testRespUpdate(ts.Request(1, 4)))
	ts.RequestEvent(request.EvResponse, ts.Request(1, 5), testRespUpdate(ts.Request(1, 5)))
	ts.AddAllowance(testServer2, 2)
	// expect 2 more requests but no sync progress (responses 4 and 5 cannot be added before 2 and 3)
	ts.Run(3,
		testServer2, ReqUpdates{FirstPeriod: 56, Count: 8},
		testServer2, ReqUpdates{FirstPeriod: 64, Count: 8})
	chain.ExpNextSyncPeriod(t, 8)

	// soft timeout for requests 2 and 3 (server 1 is overloaded)
	ts.RequestEvent(request.EvTimeout, ts.Request(1, 2), nil)
	ts.RequestEvent(request.EvTimeout, ts.Request(1, 3), nil)
	// no allowance, no more requests
	ts.Run(4)

	// valid response to requests 6 and 8 and 9
	ts.RequestEvent(request.EvResponse, ts.Request(1, 6), testRespUpdate(ts.Request(1, 6)))
	ts.RequestEvent(request.EvResponse, ts.Request(3, 1), testRespUpdate(ts.Request(3, 1)))
	ts.RequestEvent(request.EvResponse, ts.Request(3, 2), testRespUpdate(ts.Request(3, 2)))
	ts.AddAllowance(testServer2, 3)
	// server 2 can now resend requests 2 and 3 (timed out by server 1) and also send a new one
	ts.Run(5,
		testServer2, ReqUpdates{FirstPeriod: 8, Count: 8},
		testServer2, ReqUpdates{FirstPeriod: 16, Count: 8},
		testServer2, ReqUpdates{FirstPeriod: 72, Count: 8})

	// server 1 finally answers timed out request 2
	ts.RequestEvent(request.EvResponse, ts.Request(1, 2), testRespUpdate(ts.Request(1, 2)))
	ts.AddAllowance(testServer1, 1)
	// expect sync progress and one new request
	ts.Run(6, testServer1, ReqUpdates{FirstPeriod: 80, Count: 8})
	chain.ExpNextSyncPeriod(t, 16)

	// server 2 answers requests 11 and 12 (resends of requests 2 and 3)
	ts.RequestEvent(request.EvResponse, ts.Request(5, 1), testRespUpdate(ts.Request(5, 1)))
	ts.RequestEvent(request.EvResponse, ts.Request(5, 2), testRespUpdate(ts.Request(5, 2)))
	ts.AddAllowance(testServer2, 2)
	ts.Run(7,
		testServer2, ReqUpdates{FirstPeriod: 88, Count: 8},
		testServer2, ReqUpdates{FirstPeriod: 96, Count: 4})
	// finally the gap is filled, update can process responses up to req6
	chain.ExpNextSyncPeriod(t, 48)

	// all remaining requests are answered
	ts.RequestEvent(request.EvResponse, ts.Request(1, 3), testRespUpdate(ts.Request(1, 3)))
	ts.RequestEvent(request.EvResponse, ts.Request(2, 1), testRespUpdate(ts.Request(2, 1)))
	ts.RequestEvent(request.EvResponse, ts.Request(5, 3), testRespUpdate(ts.Request(5, 3)))
	ts.RequestEvent(request.EvResponse, ts.Request(6, 1), testRespUpdate(ts.Request(6, 1)))
	ts.RequestEvent(request.EvResponse, ts.Request(7, 1), testRespUpdate(ts.Request(7, 1)))
	ts.RequestEvent(request.EvResponse, ts.Request(7, 2), testRespUpdate(ts.Request(7, 2)))
	ts.Run(8)
	// expect chain to be fully synced
	chain.ExpNextSyncPeriod(t, 100)
}

func TestUpdateSyncDifferentHeads(t *testing.T) {
	chain := &TestCommitteeChain{}
	chain.SetNextSyncPeriod(10)
	updateSync := NewForwardUpdateSync(chain)
	ts := NewTestScheduler(t, updateSync)
	// add 3 servers with different announced head periods
	ts.AddServer(testServer1, 1)
	ts.ServerEvent(EvNewSignedHead, testServer1, types.SignedHeader{SignatureSlot: 0x2000*15 + 0x1000})
	ts.AddServer(testServer2, 1)
	ts.ServerEvent(EvNewSignedHead, testServer2, types.SignedHeader{SignatureSlot: 0x2000*16 + 0x1000})
	ts.AddServer(testServer3, 1)
	ts.ServerEvent(EvNewSignedHead, testServer3, types.SignedHeader{SignatureSlot: 0x2000*17 + 0x1000})

	// expect request to the best announced head
	ts.Run(1, testServer3, ReqUpdates{FirstPeriod: 10, Count: 7})

	// request times out, expect request to the next best head
	ts.RequestEvent(request.EvTimeout, ts.Request(1, 1), nil)
	ts.Run(2, testServer2, ReqUpdates{FirstPeriod: 10, Count: 6})

	// request times out, expect request to the last available server
	ts.RequestEvent(request.EvTimeout, ts.Request(2, 1), nil)
	ts.Run(3, testServer1, ReqUpdates{FirstPeriod: 10, Count: 5})

	// valid response to request 3, expect chain synced to period 15
	ts.RequestEvent(request.EvResponse, ts.Request(3, 1), testRespUpdate(ts.Request(3, 1)))
	ts.AddAllowance(testServer1, 1)
	ts.Run(4)
	chain.ExpNextSyncPeriod(t, 15)

	// invalid response to request 1, server can only deliver updates up to period 15 despite announced head
	truncated := ts.Request(1, 1)
	truncated.request = ReqUpdates{FirstPeriod: 10, Count: 5}
	ts.RequestEvent(request.EvResponse, ts.Request(1, 1), testRespUpdate(truncated))
	ts.ExpFail(testServer3)
	ts.Run(5)
	// expect no progress of chain head
	chain.ExpNextSyncPeriod(t, 15)

	// valid response to request 2, expect chain synced to period 16
	ts.RequestEvent(request.EvResponse, ts.Request(2, 1), testRespUpdate(ts.Request(2, 1)))
	ts.AddAllowance(testServer2, 1)
	ts.Run(6)
	chain.ExpNextSyncPeriod(t, 16)

	// a new server is registered with announced head period 17
	ts.AddServer(testServer4, 1)
	ts.ServerEvent(EvNewSignedHead, testServer4, types.SignedHeader{SignatureSlot: 0x2000*17 + 0x1000})
	// expect request to sync one more period
	ts.Run(7, testServer4, ReqUpdates{FirstPeriod: 16, Count: 1})

	// valid response, expect chain synced to period 17
	ts.RequestEvent(request.EvResponse, ts.Request(7, 1), testRespUpdate(ts.Request(7, 1)))
	ts.AddAllowance(testServer4, 1)
	ts.Run(8)
	chain.ExpNextSyncPeriod(t, 17)
}

func testRespUpdate(request requestWithID) request.Response {
	var resp RespUpdates
	if request.request == nil {
		return resp
	}
	req := request.request.(ReqUpdates)
	resp.Updates = make([]*types.LightClientUpdate, int(req.Count))
	resp.Committees = make([]*types.SerializedSyncCommittee, int(req.Count))
	period := req.FirstPeriod
	for i := range resp.Updates {
		resp.Updates[i] = &types.LightClientUpdate{AttestedHeader: types.SignedHeader{Header: types.Header{Slot: 0x2000*period + 0x1000}}}
		resp.Committees[i] = new(types.SerializedSyncCommittee)
		period++
	}
	return resp
}