package clientdb

import (
	"bytes"
	"fmt"
	"io"
	"time"

	"github.com/lightninglabs/pool/auctioneerrpc"
	"github.com/lightninglabs/pool/codec"
	"github.com/lightninglabs/pool/event"
	"github.com/lightninglabs/pool/order"
	"github.com/lightninglabs/pool/poolrpc"
	"go.etcd.io/bbolt"
)

// OrderEvent is the main interface for order specific events.
type OrderEvent interface {
	event.Event

	// Nonce returns the nonce of the order this event refers to.
	Nonce() order.Nonce
}

// CreatedEvent is an event implementation that tracks the creation of an order.
// This is distinct from the order state change to allow us to efficiently
// filter all events by their type to get the creation timestamps of all orders.
type CreatedEvent struct {
	// timestamp is the unique timestamp the event was created/recorded at.
	timestamp time.Time

	// Nonce of the order this event refers to.
	nonce order.Nonce
}

// NewCreatedEvent creates a new CreatedEvent from an order with the current
// system time as the timestamp.
func NewCreatedEvent(o order.Order) *CreatedEvent {
	return &CreatedEvent{
		timestamp: time.Now(),
		nonce:     o.Nonce(),
	}
}

// Type returns the type of the event.
//
// NOTE: This is part of the event.Event interface.
func (e *CreatedEvent) Type() event.Type {
	return event.TypeOrderCreated
}

// Timestamp is the time the event happened. This will be made unique once it is
// stored. To avoid collisions, the timestamp is adjusted on the nanosecond
// scale to reach uniqueness.
//
// NOTE: This is part of the event.Event interface.
func (e *CreatedEvent) Timestamp() time.Time {
	return e.timestamp
}

// SetTimestamp updates the timestamp of the event. This is needed to adjust
// timestamps in case they collide to ensure the global uniqueness of all event
// timestamps.
//
// NOTE: This is part of the event.Event interface.
func (e *CreatedEvent) SetTimestamp(ts time.Time) {
	e.timestamp = ts
}

// String returns a human readable representation of the event.
//
// NOTE: This is part of the event.Event interface.
func (e *CreatedEvent) String() string {
	return "OrderCreated"
}

// Serialize writes the event data to a binary storage format. This does not
// serialize the event type as that's handled generically to allow for easy
// filtering.
//
// NOTE: This is part of the event.Event interface.
func (e *CreatedEvent) Serialize(w *bytes.Buffer) error {
	return codec.WriteElements(w, e.nonce[:])
}

// Deserialize reads the event data from a binary storage format. This does not
// deserialize the event type as that's handled generically to allow for easy
// filtering.
//
// NOTE: This is part of the event.Event interface.
func (e *CreatedEvent) Deserialize(r io.Reader) error {
	return ReadElements(r, &e.nonce)
}

// Nonce returns the nonce of the order this event refers to.
//
// NOTE: This is part of the order.OrderEvent interface.
func (e *CreatedEvent) Nonce() order.Nonce {
	return e.nonce
}

// A compile time assertion to make sure CreatedEvent implements both the
// event.Event and order.OrderEvent interface.
var _ event.Event = (*CreatedEvent)(nil)
var _ OrderEvent = (*CreatedEvent)(nil)

// UpdatedEvent is an event implementation that tracks the updates of an order.
// This event is only meant for updates that we also persist in the database.
// Temporary state changes and other updates that occur during match making are
// tracked by MatchEvent.
type UpdatedEvent struct {
	// timestamp is the unique timestamp the event was created/recorded at.
	timestamp time.Time

	// Nonce of the order this event refers to.
	nonce order.Nonce

	// PrevState is the state the order had previous to the state change.
	PrevState order.State

	// NewState is the state the order had after the state change.
	NewState order.State

	// UnitsFilled is the number of units that was filled at the moment of
	// the update.
	UnitsFilled order.SupplyUnit
}

// NewUpdatedEvent creates a new UpdatedEvent from an order and its previous
// state with the current system time as the timestamp.
func NewUpdatedEvent(prevState order.State,
	o order.Order) *UpdatedEvent {

	return &UpdatedEvent{
		timestamp:   time.Now(),
		nonce:       o.Nonce(),
		PrevState:   prevState,
		NewState:    o.Details().State,
		UnitsFilled: o.Details().Units - o.Details().UnitsUnfulfilled,
	}
}

// Type returns the type of the event.
//
// NOTE: This is part of the event.Event interface.
func (e *UpdatedEvent) Type() event.Type {
	return event.TypeOrderStateChange
}

// Timestamp is the time the event happened. This will be made unique once it is
// stored. To avoid collisions, the timestamp is adjusted on the nanosecond
// scale to reach uniqueness.
//
// NOTE: This is part of the event.Event interface.
func (e *UpdatedEvent) Timestamp() time.Time {
	return e.timestamp
}

// SetTimestamp updates the timestamp of the event. This is needed to adjust
// timestamps in case they collide to ensure the global uniqueness of all event
// timestamps.
//
// NOTE: This is part of the event.Event interface.
func (e *UpdatedEvent) SetTimestamp(ts time.Time) {
	e.timestamp = ts
}

// String returns a human readable representation of the event.
//
// NOTE: This is part of the event.Event interface.
func (e *UpdatedEvent) String() string {
	return fmt.Sprintf("OrderUpdate(%v)", e.NewState)
}

// Serialize writes the event data to a binary storage format. This does not
// serialize the event type as that's handled generically to allow for easy
// filtering.
//
// NOTE: This is part of the event.Event interface.
func (e *UpdatedEvent) Serialize(w *bytes.Buffer) error {
	return codec.WriteElements(
		w, e.nonce[:], uint8(e.PrevState), uint8(e.NewState),
		uint64(e.UnitsFilled),
	)
}

// Deserialize reads the event data from a binary storage format. This does not
// deserialize the event type as that's handled generically to allow for easy
// filtering.
//
// NOTE: This is part of the event.Event interface.
func (e *UpdatedEvent) Deserialize(r io.Reader) error {
	return ReadElements(
		r, &e.nonce, &e.PrevState, &e.NewState, &e.UnitsFilled,
	)
}

// Nonce returns the nonce of the order this event refers to.
//
// NOTE: This is part of the order.OrderEvent interface.
func (e *UpdatedEvent) Nonce() order.Nonce {
	return e.nonce
}

// A compile time assertion to make sure UpdatedEvent implements both the
// event.Event and order.OrderEvent interface.
var _ event.Event = (*UpdatedEvent)(nil)
var _ OrderEvent = (*UpdatedEvent)(nil)

// MatchEvent is an event implementation that tracks the match making process of
// an order.
type MatchEvent struct {
	// timestamp is the unique timestamp the event was created/recorded at.
	timestamp time.Time

	// Nonce of the order this event refers to.
	nonce order.Nonce

	// MatchState is the state of the order matching process the event was
	// created in.
	MatchState order.MatchState

	// UnitsFilled is the number of units that was or would have been filled
	// for the current match attempt the order was in when this event was
	// created.
	UnitsFilled order.SupplyUnit

	// MatchedOrder is the order counterpart that our order was matched to
	// in the current match attempt this event was created for.
	MatchedOrder order.Nonce

	// RejectReason is set to the reason we rejected the match in case the
	// MatchState is set to MatchStateRejected.
	RejectReason uint32
}

// NewMatchEvent creates a new MatchEvent from an order and its matched
// counterpart with the given time as the timestamp.
func NewMatchEvent(ts time.Time, nonce order.Nonce, state order.MatchState,
	unitsFilled order.SupplyUnit, matchedOrder order.Nonce,
	rejectReason uint32) *MatchEvent {

	return &MatchEvent{
		timestamp:    ts,
		nonce:        nonce,
		MatchState:   state,
		UnitsFilled:  unitsFilled,
		MatchedOrder: matchedOrder,
		RejectReason: rejectReason,
	}
}

// Type returns the type of the event.
//
// NOTE: This is part of the event.Event interface.
func (e *MatchEvent) Type() event.Type {
	return event.TypeOrderMatch
}

// Timestamp is the time the event happened. This will be made unique once it is
// stored. To avoid collisions, the timestamp is adjusted on the nanosecond
// scale to reach uniqueness.
//
// NOTE: This is part of the event.Event interface.
func (e *MatchEvent) Timestamp() time.Time {
	return e.timestamp
}

// SetTimestamp updates the timestamp of the event. This is needed to adjust
// timestamps in case they collide to ensure the global uniqueness of all event
// timestamps.
//
// NOTE: This is part of the event.Event interface.
func (e *MatchEvent) SetTimestamp(ts time.Time) {
	e.timestamp = ts
}

// String returns a human readable representation of the event.
//
// NOTE: This is part of the event.Event interface.
func (e *MatchEvent) String() string {
	return fmt.Sprintf("OrderMatch(%v)", e.MatchState)
}

// Serialize writes the event data to a binary storage format. This does not
// serialize the event type as that's handled generically to allow for easy
// filtering.
//
// NOTE: This is part of the event.Event interface.
func (e *MatchEvent) Serialize(w *bytes.Buffer) error {
	return codec.WriteElements(
		w, e.nonce[:], uint8(e.MatchState), uint64(e.UnitsFilled),
		e.MatchedOrder[:], e.RejectReason,
	)
}

// Deserialize reads the event data from a binary storage format. This does not
// deserialize the event type as that's handled generically to allow for easy
// filtering.
//
// NOTE: This is part of the event.Event interface.
func (e *MatchEvent) Deserialize(r io.Reader) error {
	return ReadElements(
		r, &e.nonce, &e.MatchState, &e.UnitsFilled, &e.MatchedOrder,
		&e.RejectReason,
	)
}

// Nonce returns the nonce of the order this event refers to.
//
// NOTE: This is part of the order.OrderEvent interface.
func (e *MatchEvent) Nonce() order.Nonce {
	return e.nonce
}

// A compile time assertion to make sure MatchEvent implements both the
// event.Event and order.OrderEvent interface.
var _ event.Event = (*MatchEvent)(nil)
var _ OrderEvent = (*MatchEvent)(nil)

// GetOrderEvents returns all events of an order by looking up the event
// reference keys in the order bucket.
func (db *DB) GetOrderEvents(o order.Nonce) ([]event.Event, error) {
	var events []event.Event
	err := db.View(func(tx *bbolt.Tx) error {
		ordersBucket, err := getBucket(tx, ordersBucketKey)
		if err != nil {
			return err
		}

		orderBucket := ordersBucket.Bucket(o[:])
		if orderBucket == nil {
			return ErrNoOrder
		}

		eventSubBucket := orderBucket.Bucket(eventRefSubBucket)
		if eventSubBucket == nil {
			return fmt.Errorf("order event sub bucket not found")
		}

		// We first need to collect all timestamps from the order
		// bucket.
		eventTimestampMap := make(map[time.Time]struct{})
		err = eventSubBucket.ForEach(func(k, v []byte) error {
			// Only look at keys with correct length.
			if len(k) != event.TimestampLength {
				return nil
			}

			// Assert there are no corrupt values, in the reference
			// key we only store the event's type, not the value
			// itself.
			if len(v) != 1 {
				return fmt.Errorf("unexpected timestamp "+
					"value length: %d", len(v))
			}

			ts := time.Unix(0, int64(byteOrder.Uint64(k)))
			eventTimestampMap[ts] = struct{}{}

			return nil
		})
		if err != nil {
			return err
		}

		// Now get the events themselves and return them. This is always
		// sorted by the events' timestamps.
		predicate := func(ts time.Time, _ event.Type) bool {
			_, ok := eventTimestampMap[ts]
			return ok
		}
		events, err = getEventsTX(tx, predicate)
		return err
	})
	if err != nil {
		return nil, err
	}

	return events, nil
}

// StoreOrderEvents stores a list of individual order events in a single
// database transaction. The events' timestamps are adjusted on the nanosecond
// scale to ensure they're unique.
func (db *DB) StoreOrderEvents(events []OrderEvent) error {
	// Pre-adjust the timestamps so we get as few collisions later as
	// possible. We need to convert the type because slices of interfaces
	// aren't compatible by default.
	baseEvents := make([]event.Event, len(events))
	for idx, evt := range events {
		baseEvents[idx] = evt
	}
	event.MakeUniqueTimestamps(baseEvents)

	return db.Update(func(tx *bbolt.Tx) error {
		ordersBucket, err := getBucket(tx, ordersBucketKey)
		if err != nil {
			return err
		}

		// Each event could be for a different order so we have to look
		// up the individual order bucket in each iteration.
		for _, evt := range events {
			nonce := evt.Nonce()
			orderBucket := ordersBucket.Bucket(nonce[:])
			if orderBucket == nil {
				return ErrNoOrder
			}

			if err := storeEventTX(orderBucket, evt); err != nil {
				return err
			}
		}

		return nil
	})
}

// StoreBatchEvents creates a match event of the given match state for each of
// our orders involved in a batch and stores it to the main event store. In case
// of a batch reject the RPC reason enum value can optionally be specified.
func (db *DB) StoreBatchEvents(batch *order.Batch, state order.MatchState,
	rejectReason poolrpc.MatchRejectReason) error {

	ts := time.Now()
	events := make([]OrderEvent, 0, len(batch.MatchedOrders))
	for nonce, matchedOrders := range batch.MatchedOrders {
		for _, matchedOrder := range matchedOrders {
			events = append(events, NewMatchEvent(
				ts, nonce, state, matchedOrder.UnitsFilled,
				matchedOrder.Order.Nonce(),
				uint32(rejectReason),
			))
		}
	}

	if err := db.StoreOrderEvents(events); err != nil {
		return fmt.Errorf("error storing match events: %w", err)
	}

	return nil
}

// StoreBatchPartialRejectEvents creates a reject match event for each of our
// orders involved in a batch and stores it to the main event store, including
// the reason for the reject.
func (db *DB) StoreBatchPartialRejectEvents(batch *order.Batch,
	partialRejects map[order.Nonce]*auctioneerrpc.OrderReject) error {

	// In case an order itself wasn't rejected but was just in the same
	// batch as a reject, we mark it in the event as such. If it was, this
	// default value will be overwritten accordingly.
	const defaultRejectReason = uint32(
		poolrpc.MatchRejectReason_PARTIAL_REJECT_COLLATERAL,
	)

	// The RPC names are so long, we create more shortcuts here to increase
	// readability.
	const reasonFundingFailed = uint32(
		poolrpc.MatchRejectReason_PARTIAL_REJECT_CHANNEL_FUNDING_FAILED,
	)
	const reasonDuplicatePeer = uint32(
		poolrpc.MatchRejectReason_PARTIAL_REJECT_DUPLICATE_PEER,
	)

	ts := time.Now()
	events := make([]OrderEvent, 0, len(batch.MatchedOrders))
	for nonce, matchedOrders := range batch.MatchedOrders {
		for _, matchedOrder := range matchedOrders {
			otherNonce := matchedOrder.Order.Nonce()
			evt := NewMatchEvent(
				ts, nonce, order.MatchStateRejected,
				matchedOrder.UnitsFilled, otherNonce,
				defaultRejectReason,
			)

			reject, ok := partialRejects[otherNonce]
			if ok {
				switch reject.ReasonCode {
				case auctioneerrpc.OrderReject_CHANNEL_FUNDING_FAILED:
					evt.RejectReason = reasonFundingFailed

				case auctioneerrpc.OrderReject_DUPLICATE_PEER:
					evt.RejectReason = reasonDuplicatePeer
				}
			}

			events = append(events, evt)
		}
	}

	if err := db.StoreOrderEvents(events); err != nil {
		return fmt.Errorf("error storing match events: %w", err)
	}

	return nil
}