package blockchain

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"

	"github.com/tendermint/tendermint/binary"
	. "github.com/tendermint/tendermint/common"
	dbm "github.com/tendermint/tendermint/db"
	"github.com/tendermint/tendermint/types"
)

/*
Simple low level store for blocks.

There are three types of information stored:
 - BlockMeta:   Meta information about each block
 - Block part:  Parts of each block, aggregated w/ PartSet
 - Validation:  The Validation part of each block, for gossiping precommit votes

Currently the precommit signatures are duplicated in the Block parts as
well as the Validation.  In the future this may change, perhaps by moving
the Validation data outside the Block.

Panics indicate probable corruption in the data
*/
type BlockStore struct {
	height int
	db     dbm.DB
}

func NewBlockStore(db dbm.DB) *BlockStore {
	bsjson := LoadBlockStoreStateJSON(db)
	return &BlockStore{
		height: bsjson.Height,
		db:     db,
	}
}

// Height() returns the last known contiguous block height.
func (bs *BlockStore) Height() int {
	return bs.height
}

func (bs *BlockStore) GetReader(key []byte) io.Reader {
	bytez := bs.db.Get(key)
	if bytez == nil {
		return nil
	}
	return bytes.NewReader(bytez)
}

func (bs *BlockStore) LoadBlock(height int) *types.Block {
	var n int64
	var err error
	r := bs.GetReader(calcBlockMetaKey(height))
	if r == nil {
		return nil
	}
	meta := binary.ReadBinary(&types.BlockMeta{}, r, &n, &err).(*types.BlockMeta)
	if err != nil {
		// SOMETHING HAS GONE HORRIBLY WRONG
		panic(Fmt("Error reading block meta: %v", err))
	}
	bytez := []byte{}
	for i := 0; i < meta.PartsHeader.Total; i++ {
		part := bs.LoadBlockPart(height, i)
		bytez = append(bytez, part.Bytes...)
	}
	block := binary.ReadBinary(&types.Block{}, bytes.NewReader(bytez), &n, &err).(*types.Block)
	if err != nil {
		// SOMETHING HAS GONE HORRIBLY WRONG
		panic(Fmt("Error reading block: %v", err))
	}
	return block
}

func (bs *BlockStore) LoadBlockPart(height int, index int) *types.Part {
	var n int64
	var err error
	r := bs.GetReader(calcBlockPartKey(height, index))
	if r == nil {
		return nil
	}
	part := binary.ReadBinary(&types.Part{}, r, &n, &err).(*types.Part)
	if err != nil {
		// SOMETHING HAS GONE HORRIBLY WRONG
		panic(Fmt("Error reading block part: %v", err))
	}
	return part
}

func (bs *BlockStore) LoadBlockMeta(height int) *types.BlockMeta {
	var n int64
	var err error
	r := bs.GetReader(calcBlockMetaKey(height))
	if r == nil {
		return nil
	}
	meta := binary.ReadBinary(&types.BlockMeta{}, r, &n, &err).(*types.BlockMeta)
	if err != nil {
		// SOMETHING HAS GONE HORRIBLY WRONG
		panic(Fmt("Error reading block meta: %v", err))
	}
	return meta
}

// The +2/3 and other Precommit-votes for block at `height`.
// This Validation comes from block.LastValidation for `height+1`.
func (bs *BlockStore) LoadBlockValidation(height int) *types.Validation {
	var n int64
	var err error
	r := bs.GetReader(calcBlockValidationKey(height))
	if r == nil {
		return nil
	}
	validation := binary.ReadBinary(&types.Validation{}, r, &n, &err).(*types.Validation)
	if err != nil {
		// SOMETHING HAS GONE HORRIBLY WRONG
		panic(Fmt("Error reading validation: %v", err))
	}
	return validation
}

// NOTE: the Precommit-vote heights are for the block at `height`
func (bs *BlockStore) LoadSeenValidation(height int) *types.Validation {
	var n int64
	var err error
	r := bs.GetReader(calcSeenValidationKey(height))
	if r == nil {
		return nil
	}
	validation := binary.ReadBinary(&types.Validation{}, r, &n, &err).(*types.Validation)
	if err != nil {
		// SOMETHING HAS GONE HORRIBLY WRONG
		panic(Fmt("Error reading validation: %v", err))
	}
	return validation
}

// blockParts:     Must be parts of the block
// seenValidation: The +2/3 precommits that were seen which committed at height.
//                 If all the nodes restart after committing a block,
//                 we need this to reload the precommits to catch-up nodes to the
//                 most recent height.  Otherwise they'd stall at H-1.
func (bs *BlockStore) SaveBlock(block *types.Block, blockParts *types.PartSet, seenValidation *types.Validation) {
	height := block.Height
	if height != bs.height+1 {
		// SANITY CHECK
		panic(Fmt("BlockStore can only save contiguous blocks. Wanted %v, got %v", bs.height+1, height))
	}
	if !blockParts.IsComplete() {
		// SANITY CHECK
		panic(Fmt("BlockStore can only save complete block part sets"))
	}

	// Save block meta
	meta := types.NewBlockMeta(block, blockParts)
	metaBytes := binary.BinaryBytes(meta)
	bs.db.Set(calcBlockMetaKey(height), metaBytes)

	// Save block parts
	for i := 0; i < blockParts.Total(); i++ {
		bs.saveBlockPart(height, i, blockParts.GetPart(i))
	}

	// Save block validation (duplicate and separate from the Block)
	blockValidationBytes := binary.BinaryBytes(block.LastValidation)
	bs.db.Set(calcBlockValidationKey(height-1), blockValidationBytes)

	// Save seen validation (seen +2/3 precommits for block)
	seenValidationBytes := binary.BinaryBytes(seenValidation)
	bs.db.Set(calcSeenValidationKey(height), seenValidationBytes)

	// Save new BlockStoreStateJSON descriptor
	BlockStoreStateJSON{Height: height}.Save(bs.db)

	// Done!
	bs.height = height
}

func (bs *BlockStore) saveBlockPart(height int, index int, part *types.Part) {
	// SANITY CHECK
	if height != bs.height+1 {
		panic(Fmt("BlockStore can only save contiguous blocks. Wanted %v, got %v", bs.height+1, height))
	}
	// SANITY CHECK END
	partBytes := binary.BinaryBytes(part)
	bs.db.Set(calcBlockPartKey(height, index), partBytes)
}

//-----------------------------------------------------------------------------

func calcBlockMetaKey(height int) []byte {
	return []byte(fmt.Sprintf("H:%v", height))
}

func calcBlockPartKey(height int, partIndex int) []byte {
	return []byte(fmt.Sprintf("P:%v:%v", height, partIndex))
}

func calcBlockValidationKey(height int) []byte {
	return []byte(fmt.Sprintf("V:%v", height))
}

func calcSeenValidationKey(height int) []byte {
	return []byte(fmt.Sprintf("SV:%v", height))
}

//-----------------------------------------------------------------------------

var blockStoreKey = []byte("blockStore")

type BlockStoreStateJSON struct {
	Height int
}

func (bsj BlockStoreStateJSON) Save(db dbm.DB) {
	bytes, err := json.Marshal(bsj)
	if err != nil {
		// SANITY CHECK
		panic(Fmt("Could not marshal state bytes: %v", err))
	}
	db.Set(blockStoreKey, bytes)
}

func LoadBlockStoreStateJSON(db dbm.DB) BlockStoreStateJSON {
	bytes := db.Get(blockStoreKey)
	if bytes == nil {
		return BlockStoreStateJSON{
			Height: 0,
		}
	}
	bsj := BlockStoreStateJSON{}
	err := json.Unmarshal(bytes, &bsj)
	if err != nil {
		// SOMETHING HAS GONE HORRIBLY WRONG
		panic(Fmt("Could not unmarshal bytes: %X", bytes))
	}
	return bsj
}