package stmgr

import (
	"context"
	"fmt"
	"sync"

	"github.com/ipfs/go-cid"
	cbor "github.com/ipfs/go-ipld-cbor"
	logging "github.com/ipfs/go-log/v2"
	"golang.org/x/xerrors"

	"github.com/filecoin-project/go-address"
	"github.com/filecoin-project/go-state-types/abi"
	"github.com/filecoin-project/go-state-types/network"

	// Used for genesis.
	msig0 "github.com/filecoin-project/specs-actors/actors/builtin/multisig"
	"github.com/filecoin-project/specs-actors/v3/actors/migration/nv10"

	"github.com/filecoin-project/lotus/api"
	"github.com/filecoin-project/lotus/build"
	"github.com/filecoin-project/lotus/chain/actors/builtin/paych"
	"github.com/filecoin-project/lotus/chain/actors/policy"
	"github.com/filecoin-project/lotus/chain/state"
	"github.com/filecoin-project/lotus/chain/store"
	"github.com/filecoin-project/lotus/chain/types"
	"github.com/filecoin-project/lotus/chain/vm"
)

const LookbackNoLimit = api.LookbackNoLimit
const ReceiptAmtBitwidth = 3

var log = logging.Logger("statemgr")

type StateManagerAPI interface {
	Call(ctx context.Context, msg *types.Message, ts *types.TipSet) (*api.InvocResult, error)
	GetPaychState(ctx context.Context, addr address.Address, ts *types.TipSet) (*types.Actor, paych.State, error)
	LoadActorTsk(ctx context.Context, addr address.Address, tsk types.TipSetKey) (*types.Actor, error)
	LookupID(ctx context.Context, addr address.Address, ts *types.TipSet) (address.Address, error)
	ResolveToKeyAddress(ctx context.Context, addr address.Address, ts *types.TipSet) (address.Address, error)
}

type versionSpec struct {
	networkVersion network.Version
	atOrBelow      abi.ChainEpoch
}

type migration struct {
	upgrade       MigrationFunc
	preMigrations []PreMigration
	cache         *nv10.MemMigrationCache
}

type StateManager struct {
	cs *store.ChainStore

	cancel   context.CancelFunc
	shutdown chan struct{}

	// Determines the network version at any given epoch.
	networkVersions []versionSpec
	latestVersion   network.Version

	// Maps chain epochs to migrations.
	stateMigrations map[abi.ChainEpoch]*migration
	// A set of potentially expensive/time consuming upgrades. Explicit
	// calls for, e.g., gas estimation fail against this epoch with
	// ErrExpensiveFork.
	expensiveUpgrades map[abi.ChainEpoch]struct{}

	stCache             map[string][]cid.Cid
	tCache              treeCache
	compWait            map[string]chan struct{}
	stlk                sync.Mutex
	genesisMsigLk       sync.Mutex
	newVM               func(context.Context, *vm.VMOpts) (*vm.VM, error)
	syscalls            vm.SyscallBuilder
	preIgnitionVesting  []msig0.State
	postIgnitionVesting []msig0.State
	postCalicoVesting   []msig0.State

	genesisPledge      abi.TokenAmount
	genesisMarketFunds abi.TokenAmount

	tsExecMonitor ExecMonitor
}

// Caches a single state tree
type treeCache struct {
	root cid.Cid
	tree *state.StateTree
}

func NewStateManager(cs *store.ChainStore, sys vm.SyscallBuilder) *StateManager {
	sm, err := NewStateManagerWithUpgradeSchedule(cs, sys, DefaultUpgradeSchedule())
	if err != nil {
		panic(fmt.Sprintf("default upgrade schedule is invalid: %s", err))
	}
	return sm
}

func NewStateManagerWithUpgradeSchedule(cs *store.ChainStore, sys vm.SyscallBuilder, us UpgradeSchedule) (*StateManager, error) {
	// If we have upgrades, make sure they're in-order and make sense.
	if err := us.Validate(); err != nil {
		return nil, err
	}

	stateMigrations := make(map[abi.ChainEpoch]*migration, len(us))
	expensiveUpgrades := make(map[abi.ChainEpoch]struct{}, len(us))
	var networkVersions []versionSpec
	lastVersion := network.Version0
	if len(us) > 0 {
		// If we have any upgrades, process them and create a version
		// schedule.
		for _, upgrade := range us {
			if upgrade.Migration != nil || upgrade.PreMigrations != nil {
				migration := &migration{
					upgrade:       upgrade.Migration,
					preMigrations: upgrade.PreMigrations,
					cache:         nv10.NewMemMigrationCache(),
				}
				stateMigrations[upgrade.Height] = migration
			}
			if upgrade.Expensive {
				expensiveUpgrades[upgrade.Height] = struct{}{}
			}
			networkVersions = append(networkVersions, versionSpec{
				networkVersion: lastVersion,
				atOrBelow:      upgrade.Height,
			})
			lastVersion = upgrade.Network
		}
	} else {
		// Otherwise, go directly to the latest version.
		lastVersion = build.NewestNetworkVersion
	}

	return &StateManager{
		networkVersions:   networkVersions,
		latestVersion:     lastVersion,
		stateMigrations:   stateMigrations,
		expensiveUpgrades: expensiveUpgrades,
		newVM:             vm.NewVM,
		syscalls:          sys,
		cs:                cs,
		stCache:           make(map[string][]cid.Cid),
		tCache: treeCache{
			root: cid.Undef,
			tree: nil,
		},
		compWait: make(map[string]chan struct{}),
	}, nil
}

func NewStateManagerWithUpgradeScheduleAndMonitor(cs *store.ChainStore, sys vm.SyscallBuilder, us UpgradeSchedule, em ExecMonitor) (*StateManager, error) {
	sm, err := NewStateManagerWithUpgradeSchedule(cs, sys, us)
	if err != nil {
		return nil, err
	}
	sm.tsExecMonitor = em
	return sm, nil
}

func cidsToKey(cids []cid.Cid) string {
	var out string
	for _, c := range cids {
		out += c.KeyString()
	}
	return out
}

// Start starts the state manager's optional background processes. At the moment, this schedules
// pre-migration functions to run ahead of network upgrades.
//
// This method is not safe to invoke from multiple threads or concurrently with Stop.
func (sm *StateManager) Start(context.Context) error {
	var ctx context.Context
	ctx, sm.cancel = context.WithCancel(context.Background())
	sm.shutdown = make(chan struct{})
	go sm.preMigrationWorker(ctx)
	return nil
}

// Stop starts the state manager's background processes.
//
// This method is not safe to invoke concurrently with Start.
func (sm *StateManager) Stop(ctx context.Context) error {
	if sm.cancel != nil {
		sm.cancel()
		select {
		case <-sm.shutdown:
		case <-ctx.Done():
			return ctx.Err()
		}
	}
	return nil
}

func (sm *StateManager) ChainStore() *store.ChainStore {
	return sm.cs
}

// ResolveToKeyAddress is similar to `vm.ResolveToKeyAddr` but does not allow `Actor` type of addresses.
// Uses the `TipSet` `ts` to generate the VM state.
func (sm *StateManager) ResolveToKeyAddress(ctx context.Context, addr address.Address, ts *types.TipSet) (address.Address, error) {
	switch addr.Protocol() {
	case address.BLS, address.SECP256K1:
		return addr, nil
	case address.Actor:
		return address.Undef, xerrors.New("cannot resolve actor address to key address")
	default:
	}

	if ts == nil {
		ts = sm.cs.GetHeaviestTipSet()
	}

	cst := cbor.NewCborStore(sm.cs.StateBlockstore())

	// First try to resolve the actor in the parent state, so we don't have to compute anything.
	tree, err := state.LoadStateTree(cst, ts.ParentState())
	if err != nil {
		return address.Undef, xerrors.Errorf("failed to load parent state tree: %w", err)
	}

	resolved, err := vm.ResolveToKeyAddr(tree, cst, addr)
	if err == nil {
		return resolved, nil
	}

	// If that fails, compute the tip-set and try again.
	st, _, err := sm.TipSetState(ctx, ts)
	if err != nil {
		return address.Undef, xerrors.Errorf("resolve address failed to get tipset state: %w", err)
	}

	tree, err = state.LoadStateTree(cst, st)
	if err != nil {
		return address.Undef, xerrors.Errorf("failed to load state tree")
	}

	return vm.ResolveToKeyAddr(tree, cst, addr)
}

// ResolveToKeyAddressAtFinality is similar to stmgr.ResolveToKeyAddress but fails if the ID address being resolved isn't reorg-stable yet.
// It should not be used for consensus-critical subsystems.
func (sm *StateManager) ResolveToKeyAddressAtFinality(ctx context.Context, addr address.Address, ts *types.TipSet) (address.Address, error) {
	switch addr.Protocol() {
	case address.BLS, address.SECP256K1:
		return addr, nil
	case address.Actor:
		return address.Undef, xerrors.New("cannot resolve actor address to key address")
	default:
	}

	if ts == nil {
		ts = sm.cs.GetHeaviestTipSet()
	}

	var err error
	if ts.Height() > policy.ChainFinality {
		ts, err = sm.ChainStore().GetTipsetByHeight(ctx, ts.Height()-policy.ChainFinality, ts, true)
		if err != nil {
			return address.Undef, xerrors.Errorf("failed to load lookback tipset: %w", err)
		}
	}

	cst := cbor.NewCborStore(sm.cs.StateBlockstore())
	tree := sm.tCache.tree

	if tree == nil || sm.tCache.root != ts.ParentState() {
		tree, err = state.LoadStateTree(cst, ts.ParentState())
		if err != nil {
			return address.Undef, xerrors.Errorf("failed to load parent state tree: %w", err)
		}

		sm.tCache = treeCache{
			root: ts.ParentState(),
			tree: tree,
		}
	}

	resolved, err := vm.ResolveToKeyAddr(tree, cst, addr)
	if err == nil {
		return resolved, nil
	}

	return address.Undef, xerrors.New("ID address not found in lookback state")
}

func (sm *StateManager) GetBlsPublicKey(ctx context.Context, addr address.Address, ts *types.TipSet) (pubk []byte, err error) {
	kaddr, err := sm.ResolveToKeyAddress(ctx, addr, ts)
	if err != nil {
		return pubk, xerrors.Errorf("failed to resolve address to key address: %w", err)
	}

	if kaddr.Protocol() != address.BLS {
		return pubk, xerrors.Errorf("address must be BLS address to load bls public key")
	}

	return kaddr.Payload(), nil
}

func (sm *StateManager) LookupID(ctx context.Context, addr address.Address, ts *types.TipSet) (address.Address, error) {
	cst := cbor.NewCborStore(sm.cs.StateBlockstore())
	state, err := state.LoadStateTree(cst, sm.parentState(ts))
	if err != nil {
		return address.Undef, xerrors.Errorf("load state tree: %w", err)
	}
	return state.LookupID(addr)
}

func (sm *StateManager) ValidateChain(ctx context.Context, ts *types.TipSet) error {
	tschain := []*types.TipSet{ts}
	for ts.Height() != 0 {
		next, err := sm.cs.LoadTipSet(ts.Parents())
		if err != nil {
			return err
		}

		tschain = append(tschain, next)
		ts = next
	}

	lastState := tschain[len(tschain)-1].ParentState()
	for i := len(tschain) - 1; i >= 0; i-- {
		cur := tschain[i]
		log.Infof("computing state (height: %d, ts=%s)", cur.Height(), cur.Cids())
		if cur.ParentState() != lastState {
			return xerrors.Errorf("tipset chain had state mismatch at height %d", cur.Height())
		}
		st, _, err := sm.TipSetState(ctx, cur)
		if err != nil {
			return err
		}
		lastState = st
	}

	return nil
}

func (sm *StateManager) SetVMConstructor(nvm func(context.Context, *vm.VMOpts) (*vm.VM, error)) {
	sm.newVM = nvm
}

func (sm *StateManager) GetNtwkVersion(ctx context.Context, height abi.ChainEpoch) network.Version {
	// The epochs here are the _last_ epoch for every version, or -1 if the
	// version is disabled.
	for _, spec := range sm.networkVersions {
		if height <= spec.atOrBelow {
			return spec.networkVersion
		}
	}
	return sm.latestVersion
}

func (sm *StateManager) VMSys() vm.SyscallBuilder {
	return sm.syscalls
}