// Copyright 2015 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 (
    "runtime"
    "testing"
    "time"

    "github.com/ethereum/go-ethereum/consensus/ethash"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/core/vm"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/params"
)

// Tests that simple header verification works, for both good and bad blocks.
func TestHeaderVerification(t *testing.T) {
    // Create a simple chain to verify
    var (
        testdb    = ethdb.NewMemDatabase()
        gspec     = &Genesis{Config: params.TestChainConfig}
        genesis   = gspec.MustCommit(testdb)
        blocks, _ = GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), testdb, 8, nil)
    )
    headers := make([]*types.Header, len(blocks))
    for i, block := range blocks {
        headers[i] = block.Header()
    }
    // Run the header checker for blocks one-by-one, checking for both valid and invalid nonces
    chain, _ := NewBlockChain(testdb, nil, params.TestChainConfig, ethash.NewFaker(), vm.Config{}, nil)
    defer chain.Stop()

    for i := 0; i < len(blocks); i++ {
        for j, valid := range []bool{true, false} {
            var results <-chan error

            if valid {
                engine := ethash.NewFaker()
                _, results = engine.VerifyHeaders(chain, []*types.Header{headers[i]}, []bool{true})
            } else {
                engine := ethash.NewFakeFailer(headers[i].Number.Uint64())
                _, results = engine.VerifyHeaders(chain, []*types.Header{headers[i]}, []bool{true})
            }
            // Wait for the verification result
            select {
            case result := <-results:
                if (result == nil) != valid {
                    t.Errorf("test %d.%d: validity mismatch: have %v, want %v", i, j, result, valid)
                }
            case <-time.After(time.Second):
                t.Fatalf("test %d.%d: verification timeout", i, j)
            }
            // Make sure no more data is returned
            select {
            case result := <-results:
                t.Fatalf("test %d.%d: unexpected result returned: %v", i, j, result)
            case <-time.After(25 * time.Millisecond):
            }
        }
        chain.InsertChain(blocks[i : i+1])
    }
}

// Tests that concurrent header verification works, for both good and bad blocks.
func TestHeaderConcurrentVerification2(t *testing.T)  { testHeaderConcurrentVerification(t, 2) }
func TestHeaderConcurrentVerification8(t *testing.T)  { testHeaderConcurrentVerification(t, 8) }
func TestHeaderConcurrentVerification32(t *testing.T) { testHeaderConcurrentVerification(t, 32) }

func testHeaderConcurrentVerification(t *testing.T, threads int) {
    // Create a simple chain to verify
    var (
        testdb    = ethdb.NewMemDatabase()
        gspec     = &Genesis{Config: params.TestChainConfig}
        genesis   = gspec.MustCommit(testdb)
        blocks, _ = GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), testdb, 8, nil)
    )
    headers := make([]*types.Header, len(blocks))
    seals := make([]bool, len(blocks))

    for i, block := range blocks {
        headers[i] = block.Header()
        seals[i] = true
    }
    // Set the number of threads to verify on
    old := runtime.GOMAXPROCS(threads)
    defer runtime.GOMAXPROCS(old)

    // Run the header checker for the entire block chain at once both for a valid and
    // also an invalid chain (enough if one arbitrary block is invalid).
    for i, valid := range []bool{true, false} {
        var results <-chan error

        if valid {
            chain, _ := NewBlockChain(testdb, nil, params.TestChainConfig, ethash.NewFaker(), vm.Config{}, nil)
            _, results = chain.engine.VerifyHeaders(chain, headers, seals)
            chain.Stop()
        } else {
            chain, _ := NewBlockChain(testdb, nil, params.TestChainConfig, ethash.NewFakeFailer(uint64(len(headers)-1)), vm.Config{}, nil)
            _, results = chain.engine.VerifyHeaders(chain, headers, seals)
            chain.Stop()
        }
        // Wait for all the verification results
        checks := make(map[int]error)
        for j := 0; j < len(blocks); j++ {
            select {
            case result := <-results:
                checks[j] = result

            case <-time.After(time.Second):
                t.Fatalf("test %d.%d: verification timeout", i, j)
            }
        }
        // Check nonce check validity
        for j := 0; j < len(blocks); j++ {
            want := valid || (j < len(blocks)-2) // We chose the last-but-one nonce in the chain to fail
            if (checks[j] == nil) != want {
                t.Errorf("test %d.%d: validity mismatch: have %v, want %v", i, j, checks[j], want)
            }
            if !want {
                // A few blocks after the first error may pass verification due to concurrent
                // workers. We don't care about those in this test, just that the correct block
                // errors out.
                break
            }
        }
        // Make sure no more data is returned
        select {
        case result := <-results:
            t.Fatalf("test %d: unexpected result returned: %v", i, result)
        case <-time.After(25 * time.Millisecond):
        }
    }
}

// Tests that aborting a header validation indeed prevents further checks from being
// run, as well as checks that no left-over goroutines are leaked.
func TestHeaderConcurrentAbortion2(t *testing.T)  { testHeaderConcurrentAbortion(t, 2) }
func TestHeaderConcurrentAbortion8(t *testing.T)  { testHeaderConcurrentAbortion(t, 8) }
func TestHeaderConcurrentAbortion32(t *testing.T) { testHeaderConcurrentAbortion(t, 32) }

func testHeaderConcurrentAbortion(t *testing.T, threads int) {
    // Create a simple chain to verify
    var (
        testdb    = ethdb.NewMemDatabase()
        gspec     = &Genesis{Config: params.TestChainConfig}
        genesis   = gspec.MustCommit(testdb)
        blocks, _ = GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), testdb, 1024, nil)
    )
    headers := make([]*types.Header, len(blocks))
    seals := make([]bool, len(blocks))

    for i, block := range blocks {
        headers[i] = block.Header()
        seals[i] = true
    }
    // Set the number of threads to verify on
    old := runtime.GOMAXPROCS(threads)
    defer runtime.GOMAXPROCS(old)

    // Start the verifications and immediately abort
    chain, _ := NewBlockChain(testdb, nil, params.TestChainConfig, ethash.NewFakeDelayer(time.Millisecond), vm.Config{}, nil)
    defer chain.Stop()

    abort, results := chain.engine.VerifyHeaders(chain, headers, seals)
    close(abort)

    // Deplete the results channel
    verified := 0
    for depleted := false; !depleted; {
        select {
        case result := <-results:
            if result != nil {
                t.Errorf("header %d: validation failed: %v", verified, result)
            }
            verified++
        case <-time.After(50 * time.Millisecond):
            depleted = true
        }
    }
    // Check that abortion was honored by not processing too many POWs
    if verified > 2*threads {
        t.Errorf("verification count too large: have %d, want below %d", verified, 2*threads)
    }
}