// Copyright 2020 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 core

import (
    "errors"
    "fmt"
    "math/big"
    "testing"
    "time"

    "github.com/autonity/autonity/consensus"
    "github.com/autonity/autonity/consensus/ethash"
    "github.com/autonity/autonity/core/rawdb"
    "github.com/autonity/autonity/core/types"
    "github.com/autonity/autonity/log"
    "github.com/autonity/autonity/params"
)

func verifyUnbrokenCanonchain(hc *HeaderChain) error {
    h := hc.CurrentHeader()
    for {
        canonHash := rawdb.ReadCanonicalHash(hc.chainDb, h.Number.Uint64())
        if exp := h.Hash(); canonHash != exp {
            return fmt.Errorf("Canon hash chain broken, block %d got %x, expected %x",
                h.Number, canonHash[:8], exp[:8])
        }
        // Verify that we have the TD
        if td := rawdb.ReadTd(hc.chainDb, canonHash, h.Number.Uint64()); td == nil {
            return fmt.Errorf("Canon TD missing at block %d", h.Number)
        }
        if h.Number.Uint64() == 0 {
            break
        }
        h = hc.GetHeader(h.ParentHash, h.Number.Uint64()-1)
    }
    return nil
}

func testInsert(t *testing.T, hc *HeaderChain, chain []*types.Header, wantStatus WriteStatus, wantErr error, forker *ForkChoice) {
    t.Helper()

    status, err := hc.InsertHeaderChain(chain, time.Now(), forker)
    if status != wantStatus {
        t.Errorf("wrong write status from InsertHeaderChain: got %v, want %v", status, wantStatus)
    }
    // Always verify that the header chain is unbroken
    if err := verifyUnbrokenCanonchain(hc); err != nil {
        t.Fatal(err)
    }
    if !errors.Is(err, wantErr) {
        t.Fatalf("unexpected error from InsertHeaderChain: %v", err)
    }
}

// This test checks status reporting of InsertHeaderChain.
func TestHeaderInsertion(t *testing.T) {
    var (
        db      = rawdb.NewMemoryDatabase()
        genesis = (&Genesis{BaseFee: big.NewInt(params.InitialBaseFee)}).MustCommit(db)
    )

    hc, err := NewHeaderChain(db, params.AllEthashProtocolChanges, ethash.NewFaker(), func() bool { return false })
    if err != nil {
        t.Fatal(err)
    }
    // chain A: G->A1->A2...A128
    chainA := makeHeaderChain(genesis.Header(), 128, ethash.NewFaker(), db, 10)
    // chain B: G->A1->B1...B128
    chainB := makeHeaderChain(chainA[0], 128, ethash.NewFaker(), db, 10)
    log.Root().SetHandler(log.StdoutHandler)

    forker := NewForkChoice(hc, nil)
    // Inserting 64 headers on an empty chain, expecting
    // 1 callbacks, 1 canon-status, 0 sidestatus,
    testInsert(t, hc, chainA[:64], CanonStatTy, nil, forker)

    // Inserting 64 identical headers, expecting
    // 0 callbacks, 0 canon-status, 0 sidestatus,
    testInsert(t, hc, chainA[:64], NonStatTy, nil, forker)

    // Inserting the same some old, some new headers
    // 1 callbacks, 1 canon, 0 side
    testInsert(t, hc, chainA[32:96], CanonStatTy, nil, forker)

    // Inserting side blocks, but not overtaking the canon chain
    testInsert(t, hc, chainB[0:32], SideStatTy, nil, forker)

    // Inserting more side blocks, but we don't have the parent
    testInsert(t, hc, chainB[34:36], NonStatTy, consensus.ErrUnknownAncestor, forker)

    // Inserting more sideblocks, overtaking the canon chain
    testInsert(t, hc, chainB[32:97], CanonStatTy, nil, forker)

    // Inserting more A-headers, taking back the canonicality
    testInsert(t, hc, chainA[90:100], CanonStatTy, nil, forker)

    // And B becomes canon again
    testInsert(t, hc, chainB[97:107], CanonStatTy, nil, forker)

    // And B becomes even longer
    testInsert(t, hc, chainB[107:128], CanonStatTy, nil, forker)
}
