package core

import (
	"context"
	"errors"
	"github.com/matchsystems/werr"
	"mic-wallet/common"
	"time"
)

var ErrOutOfDateBlockId = errors.New("")
var ErrBlockIdDoesntExist = errors.New("")

type IBlocksCreator interface {
	Run(ctx context.Context) error
	WriteTx(opts *common.NewTxOpts) error
	// GetTx Searches for tx in every block
	GetTx(block int64, hash string) *common.NewTxOpts
	GetTxs() []*common.NewTxOpts
}

// BlocksCreator creates and rotates new Blocks and pushed them to the commiter
type BlocksCreator struct {
	blocks        map[int64]*Block
	txsLeftOver   map[string]*common.NewTxOpts
	commiter      IBlocksCommiter
	prevBlockHash []byte
}

func NewBlocksCreator(commiter IBlocksCommiter) *BlocksCreator {
	return &BlocksCreator{
		blocks:      make(map[int64]*Block),
		txsLeftOver: make(map[string]*common.NewTxOpts),
		commiter:    commiter,
	}
}

func (bc *BlocksCreator) Run(ctx context.Context) (err error) {
	var blockID int64
	var prevLeftOver map[string]*common.NewTxOpts
	for {
		blockID = common.GetBlockId(time.Now())
		if oldBlock, ok := bc.blocks[blockID-common.BlockSecsDiff]; ok { // Commit and delete old block
			// we need to know previous hash for new block.
			// new transactions while oldBlock.Finish is executing will
			// end up in leftOver so they will be parts of the next block
			if bc.prevBlockHash, err = oldBlock.Finish(); err != nil {
				return nil
			}
			go bc.commiter.CommitBlock(ctx, oldBlock) // may take a while
			delete(bc.blocks, blockID-common.BlockSecsDiff)
		}
		// prevLeftOver becomes new block's transactions
		// so there is no "lost" transactions
		prevLeftOver = bc.txsLeftOver
		// and also now we need to make new leftOver
		bc.txsLeftOver = make(map[string]*common.NewTxOpts)
		bc.blocks[blockID] = NewBlock(blockID, bc.prevBlockHash, prevLeftOver, bc.txsLeftOver)
		// Waiting for the next block
		time.Sleep(time.Until(time.Unix(blockID+common.BlockSecsDiff, 0)))
	}
}

// WriteTx validates transaction and writes it into the current block
// if transaction is valid
func (bc *BlocksCreator) WriteTx(opts *common.NewTxOpts) error {
	// validating may take some time, so to don't write into
	if err := opts.Validate(); err != nil {
		return werr.Wrapf(err,
			"error validating transaction %s", opts.HashString())
	}
	currentBlockID := common.GetBlockId(time.Now())
	if currentBlockID < opts.BlockId {
		return werr.Wrapf(common.ErrEntityNotFound, "block id %d does not exist", currentBlockID)
	} else if currentBlockID > opts.BlockId {
		return werr.Wrapf(common.ErrEntityOutdated, "block id %d is out of date", currentBlockID)
	}
	block, ok := bc.blocks[currentBlockID]
	if !ok {
		return werr.Wrapf(common.ErrEntityNotFound, "block id %d does not exist", currentBlockID)
	}
	if err := block.AddTx(opts); err != nil {
		return werr.Wrapf(err,
			"error adding transaction to block %d", currentBlockID)
	}
	return nil
}