From 887b72ff111aedcf1acd79d476242a30ff6ce02f Mon Sep 17 00:00:00 2001
From: Raul Jordan <rauljordan@college.harvard.edu>
Date: Thu, 3 May 2018 10:22:28 -0500
Subject: [PATCH] sharding: beginning receiver methods for shard type

Former-commit-id: fc39828fa985074ec20fd3ec1a99c612630b8b1f [formerly 89a47cea8d6d4c2ab1aa77d1d713680394dc823e]
Former-commit-id: 44edff25e19c39aeefbf08f260373c0976248f74
---
 sharding/collation.go | 32 ++++--------------
 sharding/db.go        | 21 ++++++++++++
 sharding/shard.go     | 77 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 104 insertions(+), 26 deletions(-)
 create mode 100644 sharding/db.go

diff --git a/sharding/collation.go b/sharding/collation.go
index f3e8a81de..10fea6e40 100644
--- a/sharding/collation.go
+++ b/sharding/collation.go
@@ -1,16 +1,14 @@
 package sharding
 
 import (
-	"math"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/types"
 )
 
 type Collation struct {
-	header       *CollationHeader
-	transactions []*types.Transaction
+	header *CollationHeader
+	body   []byte
 }
 
 type CollationHeader struct {
@@ -21,27 +19,9 @@ type CollationHeader struct {
 	proposerSignature []byte          //the proposer's signature for calculating collation hash
 }
 
-func (c *Collation) Header() *CollationHeader           { return c.header }
-func (c *Collation) Transactions() []*types.Transaction { return c.transactions }
-func (c *Collation) ShardID() *big.Int                  { return c.header.shardID }
-func (c *Collation) Period() *big.Int                   { return c.header.period }
-func (c *Collation) ProposerAddress() *common.Address   { return c.header.proposerAddress }
+func (c *Collation) Header() *CollationHeader         { return c.header }
+func (c *Collation) ShardID() *big.Int                { return c.header.shardID }
+func (c *Collation) Period() *big.Int                 { return c.header.period }
+func (c *Collation) ProposerAddress() *common.Address { return c.header.proposerAddress }
 
 func (c *Collation) SetHeader(h *CollationHeader) { c.header = h }
-
-func (c *Collation) AddTransaction(tx *types.Transaction) {
-	// TODO: Check transaction does not exceed gas limit
-	c.transactions = append(c.transactions, tx)
-}
-
-func (c *Collation) GasUsed() *big.Int {
-	g := uint64(0)
-	for _, tx := range c.transactions {
-		if g > math.MaxUint64-(g+tx.Gas()) {
-			g = math.MaxUint64
-			break
-		}
-		g += tx.Gas()
-	}
-	return big.NewInt(0).SetUint64(g)
-}
diff --git a/sharding/db.go b/sharding/db.go
new file mode 100644
index 000000000..22519b44c
--- /dev/null
+++ b/sharding/db.go
@@ -0,0 +1,21 @@
+package sharding
+
+import "github.com/ethereum/go-ethereum/common"
+
+type shardBackend struct {
+	kv map[*common.Hash][]byte
+}
+
+func (sb *shardBackend) Get(k *common.Hash) []byte {
+	return sb.kv[k]
+}
+
+func (sb *shardBackend) Put(k *common.Hash, v []byte) {
+	sb.kv[k] = v
+	return
+}
+
+func (sb *shardBackend) Delete(k *common.Hash) {
+	delete(sb.kv, k)
+	return
+}
diff --git a/sharding/shard.go b/sharding/shard.go
index ec576df7c..886315baf 100644
--- a/sharding/shard.go
+++ b/sharding/shard.go
@@ -1 +1,78 @@
 package sharding
+
+import (
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+// Shard base struct.
+type Shard struct {
+	shardDB *shardBackend
+	shardID *big.Int
+}
+
+// ValidateShardID checks if header belongs to shard.
+func (s *Shard) ValidateShardID(h *CollationHeader) error {
+	if s.shardID.Cmp(h.shardID) != 0 {
+		return fmt.Errorf("Error: Collation Does Not Belong to Shard %d but Instead Has ShardID %d", h.shardID, s.shardID)
+	}
+	return nil
+}
+
+// GetHeaderByHash of collation.
+func (s *Shard) GetHeaderByHash(hash *common.Hash) (*CollationHeader, error) {
+	encoded := s.shardDB.Get(hash)
+	var header CollationHeader
+	if err := rlp.DecodeBytes(encoded, &header); err != nil {
+		return nil, fmt.Errorf("Error Decoding Header: %v", err)
+	}
+	return &header, nil
+}
+
+// GetHeaderByPeriod the header was added.
+func (s *Shard) GetHeaderByPeriod(period *big.Int) *CollationHeader {
+	return nil
+}
+
+// GetCollationByHash fetches full collation.
+func (s *Shard) GetCollationByHash(hash *common.Hash) (*Collation, error) {
+	header, err := s.GetHeaderByHash(hash)
+	if err != nil {
+		return nil, err
+	}
+	body, err := s.GetBodyByChunkRoot(header.chunkRoot)
+	if err != nil {
+		return nil, err
+	}
+	return &Collation{header: header, body: body}, nil
+}
+
+// GetBodyByChunkRoot fetches a collation body
+func (s *Shard) GetBodyByChunkRoot(chunkRoot *common.Hash) ([]byte, error) {
+	body := s.shardDB.Get(chunkRoot)
+	if body == nil {
+		return nil, fmt.Errorf("Error: No Corresponding Body With Chunk Root Found")
+	}
+	return body, nil
+}
+
+// CheckAvailability is used by notaries to confirm a header's data availability.
+func (s *Shard) CheckAvailability(header *CollationHeader) bool {
+	return true
+}
+
+// SetUnavailable ensures to set a collation as unavailable in the shardDB.
+func (s *Shard) SetUnavailable(header *CollationHeader) error {
+	return nil
+}
+
+// SetCanonical is called after >= 2/3 notaries vote on header and period ends.
+func (s *Shard) SetCanonical(header *CollationHeader) error {
+	return nil
+}
+
+// Set Header and Set Body Methods
+// TODO: error in Get from the kv store