package channeldb

import (
	"bytes"
	"fmt"

	"github.com/coreos/bbolt"
)

// migrateNodeAndEdgeUpdateIndex is a migration function that will update the
// database from version 0 to version 1. In version 1, we add two new indexes
// (one for nodes and one for edges) to keep track of the last time a node or
// edge was updated on the network. These new indexes allow us to implement the
// new graph sync protocol added.
func migrateNodeAndEdgeUpdateIndex(tx *bolt.Tx) error {
	// First, we'll populating the node portion of the new index. Before we
	// can add new values to the index, we'll first create the new bucket
	// where these items will be housed.
	nodes, err := tx.CreateBucketIfNotExists(nodeBucket)
	if err != nil {
		return fmt.Errorf("unable to create node bucket: %v", err)
	}
	nodeUpdateIndex, err := nodes.CreateBucketIfNotExists(
		nodeUpdateIndexBucket,
	)
	if err != nil {
		return fmt.Errorf("unable to create node update index: %v", err)
	}

	log.Infof("Populating new node update index bucket")

	// Now that we know the bucket has been created, we'll iterate over the
	// entire node bucket so we can add the (updateTime || nodePub) key
	// into the node update index.
	err = nodes.ForEach(func(nodePub, nodeInfo []byte) error {
		if len(nodePub) != 33 {
			return nil
		}

		log.Tracef("Adding %x to node update index", nodePub)

		// The first 8 bytes of a node's serialize data is the update
		// time, so we can extract that without decoding the entire
		// structure.
		updateTime := nodeInfo[:8]

		// Now that we have the update time, we can construct the key
		// to insert into the index.
		var indexKey [8 + 33]byte
		copy(indexKey[:8], updateTime)
		copy(indexKey[8:], nodePub)

		return nodeUpdateIndex.Put(indexKey[:], nil)
	})
	if err != nil {
		return fmt.Errorf("unable to update node indexes: %v", err)
	}

	log.Infof("Populating new edge update index bucket")

	// With the set of nodes updated, we'll now update all edges to have a
	// corresponding entry in the edge update index.
	edges, err := tx.CreateBucketIfNotExists(edgeBucket)
	if err != nil {
		return fmt.Errorf("unable to create edge bucket: %v", err)
	}
	edgeUpdateIndex, err := edges.CreateBucketIfNotExists(
		edgeUpdateIndexBucket,
	)
	if err != nil {
		return fmt.Errorf("unable to create edge update index: %v", err)
	}

	// We'll now run through each edge policy in the database, and update
	// the index to ensure each edge has the proper record.
	err = edges.ForEach(func(edgeKey, edgePolicyBytes []byte) error {
		if len(edgeKey) != 41 {
			return nil
		}

		// Now that we know this is the proper record, we'll grab the
		// channel ID (last 8 bytes of the key), and then decode the
		// edge policy so we can access the update time.
		chanID := edgeKey[33:]
		edgePolicyReader := bytes.NewReader(edgePolicyBytes)

		edgePolicy, err := deserializeChanEdgePolicy(
			edgePolicyReader, nodes,
		)
		if err != nil {
			return err
		}

		log.Tracef("Adding chan_id=%v to edge update index",
			edgePolicy.ChannelID)

		// We'll now construct the index key using the channel ID, and
		// the last time it was updated: (updateTime || chanID).
		var indexKey [8 + 8]byte
		byteOrder.PutUint64(
			indexKey[:], uint64(edgePolicy.LastUpdate.Unix()),
		)
		copy(indexKey[8:], chanID)

		return edgeUpdateIndex.Put(indexKey[:], nil)
	})
	if err != nil {
		return fmt.Errorf("unable to update edge indexes: %v", err)
	}

	log.Infof("Migration to node and edge update indexes complete!")

	return nil
}