package cmd

import (
	"fmt"
	"strings"

	"github.com/spf13/cobra"

	dbm "github.com/cometbft/cometbft-db"

	"github.com/cosmos/cosmos-sdk/client"
	"github.com/cosmos/cosmos-sdk/client/flags"
	"github.com/cosmos/cosmos-sdk/server"
	pruningtypes "github.com/cosmos/cosmos-sdk/store/pruning/types"
	"github.com/cosmos/cosmos-sdk/store/rootmulti"

	tmconfig "github.com/cometbft/cometbft/config"
	"github.com/cometbft/cometbft/node"
	tmstate "github.com/cometbft/cometbft/state"
	"github.com/cometbft/cometbft/store"

	ethermintserver "github.com/evmos/ethermint/server"
)

const (
	flagShardStartBlock   = "start"
	flagShardEndBlock     = "end"
	flagShardOnlyAppState = "only-app-state"
	// TODO: --preserve flag for creating & operating on a copy?

	// allow using -1 to mean "latest" (perform no rollbacks)
	shardEndBlockLatest = -1
)

func newShardCmd(opts ethermintserver.StartOptions) *cobra.Command {
	cmd := &cobra.Command{
		Use:   "shard --home <path-to-home-dir> --start <start-block> --end <end-block> [--only-app-state]",
		Short: "Strip all blocks from the database outside of a given range",
		Long: `shard opens a local kava home directory's databases and removes all blocks outside a range defined by --start and --end. The range is inclusive of the end block.

It works by first rolling back the latest state to the block before the end block, and then by pruning all state before the start block.

Setting the end block to -1 signals to keep the latest block (no rollbacks).

The --only-app-state flag can be used to skip the pruning of the blockstore and cometbft state. This matches the functionality of the cosmos-sdk's "prune" command. Note that rolled back blocks will still affect all stores.

WARNING: this is a destructive action.`,
		Example: `Create a 1M block data shard (keeps blocks kava 1,000,000 to 2,000,000)
$ kava shard --home path/to/.kava --start 1000000 --end 2000000

Prune all blocks up to 5,000,000:
$ kava shard --home path/to/.kava --start 5000000 --end -1

Prune first 1M blocks _without_ affecting blockstore or cometBFT state:
$ kava shard --home path/to/.kava --start 1000000 --end -1 --only-app-state`,
		RunE: func(cmd *cobra.Command, args []string) error {
			// read & validate flags
			startBlock, err := cmd.Flags().GetInt64(flagShardStartBlock)
			if err != nil {
				return err
			}
			endBlock, err := cmd.Flags().GetInt64(flagShardEndBlock)
			if err != nil {
				return err
			}
			if (endBlock == 0 || endBlock < startBlock) && endBlock != shardEndBlockLatest {
				return fmt.Errorf("end block (%d) must be greater than start block (%d)", endBlock, startBlock)
			}
			onlyAppState, err := cmd.Flags().GetBool(flagShardOnlyAppState)
			if err != nil {
				return err
			}

			clientCtx := client.GetClientContextFromCmd(cmd)

			ctx := server.GetServerContextFromCmd(cmd)
			ctx.Config.SetRoot(clientCtx.HomeDir)

			//////////////////////////////
			// Rollback state to endBlock
			//////////////////////////////

			// connect to database
			db, err := opts.DBOpener(ctx.Viper, clientCtx.HomeDir, server.GetAppDBBackend(ctx.Viper))
			if err != nil {
				return err
			}

			// close db connection when done
			defer func() {
				if err := db.Close(); err != nil {
					ctx.Logger.Error("error closing db", "error", err.Error())
				}
			}()

			// get the multistore
			app := opts.AppCreator(ctx.Logger, db, nil, ctx.Viper)
			cms := app.CommitMultiStore()
			multistore, ok := cms.(*rootmulti.Store)
			if !ok {
				return fmt.Errorf("only sharding of rootmulti.Store type is supported")
			}

			// handle desired endblock being latest
			latest := multistore.LatestVersion()
			fmt.Printf("latest height: %d\n", latest)
			if endBlock == shardEndBlockLatest {
				endBlock = latest
			}
			shardSize := endBlock - startBlock + 1

			// error if requesting block range the database does not have
			if endBlock > latest {
				return fmt.Errorf("data does not contain end block (%d): latest version is %d", endBlock, latest)
			}

			fmt.Printf("pruning data in %s down to heights %d - %d (%d blocks)\n", clientCtx.HomeDir, startBlock, endBlock, shardSize)

			// set pruning options to prevent no-ops from `PruneStores`
			multistore.SetPruning(pruningtypes.PruningOptions{KeepRecent: uint64(shardSize), Interval: 0})

			// rollback application state
			if err = multistore.RollbackToVersion(endBlock); err != nil {
				return fmt.Errorf("failed to rollback application state: %s", err)
			}

			// open block store & cometbft state
			blockStore, stateStore, err := openCometBftDbs(ctx.Config)
			if err != nil {
				return fmt.Errorf("failed to open cometbft dbs: %s", err)
			}

			// prep for outputting progress repeatedly to same line
			needsRollback := endBlock < latest
			progress := "rolling back blockstore & cometbft state to height %d"
			numChars := len(fmt.Sprintf(progress, latest))
			clearLine := fmt.Sprintf("\r%s\r", strings.Repeat(" ", numChars))
			printRollbackProgress := func(h int64) {
				fmt.Print(clearLine)
				fmt.Printf(progress, h)
			}

			// rollback tendermint db
			height := latest
			for height > endBlock {
				printRollbackProgress(height - 1)
				height, _, err = tmstate.Rollback(blockStore, stateStore, true)
				if err != nil {
					return fmt.Errorf("failed to rollback tendermint state: %w", err)
				}
			}

			if needsRollback {
				fmt.Println()
			} else {
				fmt.Printf("latest store height is already %d\n", latest)
			}

			//////////////////////////////
			// Prune blocks to startBlock
			//////////////////////////////

			// enumerate all heights to prune
			pruneHeights := make([]int64, 0, latest-shardSize)
			for i := int64(1); i < startBlock; i++ {
				pruneHeights = append(pruneHeights, i)
			}

			if len(pruneHeights) > 0 {
				// prune application state
				fmt.Printf("pruning application state to height %d\n", startBlock)
				if err := multistore.PruneStores(true, pruneHeights); err != nil {
					return fmt.Errorf("failed to prune application state: %s", err)
				}
			}

			// get starting block of block store
			baseBlock := blockStore.Base()

			// only prune if data exists, otherwise blockStore.PruneBlocks will panic
			if !onlyAppState && baseBlock < startBlock {
				// prune block store
				fmt.Printf("pruning block store from %d - %d\n", baseBlock, startBlock)
				if _, err := blockStore.PruneBlocks(startBlock); err != nil {
					return fmt.Errorf("failed to prune block store (retainHeight=%d): %s", startBlock, err)
				}

				// prune cometbft state
				fmt.Printf("pruning cometbft state from %d - %d\n", baseBlock, startBlock)
				if err := stateStore.PruneStates(baseBlock, startBlock); err != nil {
					return fmt.Errorf("failed to prune cometbft state store (%d - %d): %s", baseBlock, startBlock, err)
				}
			} else {
				fmt.Printf("blockstore and cometbft state begins at block %d\n", baseBlock)
			}

			// TODO: db compaction

			return nil
		},
	}

	cmd.Flags().String(flags.FlagHome, opts.DefaultNodeHome, "The application home directory")
	cmd.Flags().Int64(flagShardStartBlock, 1, "Start block of data shard (inclusive)")
	cmd.Flags().Int64(flagShardEndBlock, 0, "End block of data shard (inclusive)")
	cmd.Flags().Bool(flagShardOnlyAppState, false, "Skip pruning of blockstore & cometbft state")

	return cmd
}

// inspired by https://github.com/Kava-Labs/cometbft/blob/277b0853db3f67865a55aa1c54f59790b5f591be/node/node.go#L234
func openCometBftDbs(config *tmconfig.Config) (blockStore *store.BlockStore, stateStore tmstate.Store, err error) {
	dbProvider := node.DefaultDBProvider

	var blockStoreDB dbm.DB
	blockStoreDB, err = dbProvider(&node.DBContext{ID: "blockstore", Config: config})
	if err != nil {
		return
	}
	blockStore = store.NewBlockStore(blockStoreDB)

	stateDB, err := dbProvider(&node.DBContext{ID: "state", Config: config})
	if err != nil {
		return
	}

	stateStore = tmstate.NewStore(stateDB, tmstate.StoreOptions{
		DiscardABCIResponses: config.Storage.DiscardABCIResponses,
	})

	return
}