package core

import (
	"fmt"

	cmn "github.com/tendermint/tendermint/libs/common"
	ctypes "github.com/tendermint/tendermint/rpc/core/types"
	rpctypes "github.com/tendermint/tendermint/rpc/lib/types"
	sm "github.com/tendermint/tendermint/state"
	"github.com/tendermint/tendermint/types"
)

// BlockchainInfo gets block headers for minHeight <= height <= maxHeight.
// Block headers are returned in descending order (highest first).
// More: https://tendermint.com/rpc/#/Info/blockchain
func BlockchainInfo(ctx *rpctypes.Context, minHeight, maxHeight int64) (*ctypes.ResultBlockchainInfo, error) {

	// maximum 20 block metas
	const limit int64 = 20
	var err error
	minHeight, maxHeight, err = filterMinMax(blockStore.Height(), minHeight, maxHeight, limit)
	if err != nil {
		return nil, err
	}
	logger.Debug("BlockchainInfoHandler", "maxHeight", maxHeight, "minHeight", minHeight)

	blockMetas := []*types.BlockMeta{}
	for height := maxHeight; height >= minHeight; height-- {
		blockMeta := blockStore.LoadBlockMeta(height)
		blockMetas = append(blockMetas, blockMeta)
	}

	return &ctypes.ResultBlockchainInfo{
		LastHeight: blockStore.Height(),
		BlockMetas: blockMetas}, nil
}

// error if either min or max are negative or min < max
// if 0, use 1 for min, latest block height for max
// enforce limit.
// error if min > max
func filterMinMax(height, min, max, limit int64) (int64, int64, error) {
	// filter negatives
	if min < 0 || max < 0 {
		return min, max, fmt.Errorf("heights must be non-negative")
	}

	// adjust for default values
	if min == 0 {
		min = 1
	}
	if max == 0 {
		max = height
	}

	// limit max to the height
	max = cmn.MinInt64(height, max)

	// limit min to within `limit` of max
	// so the total number of blocks returned will be `limit`
	min = cmn.MaxInt64(min, max-limit+1)

	if min > max {
		return min, max, fmt.Errorf("min height %d can't be greater than max height %d", min, max)
	}
	return min, max, nil
}

// Block gets block at a given height.
// If no height is provided, it will fetch the latest block.
// More: https://tendermint.com/rpc/#/Info/block
func Block(ctx *rpctypes.Context, heightPtr *int64) (*ctypes.ResultBlock, error) {
	storeHeight := blockStore.Height()
	height, err := getHeight(storeHeight, heightPtr)
	if err != nil {
		return nil, err
	}

	blockMeta := blockStore.LoadBlockMeta(height)
	block := blockStore.LoadBlock(height)
	return &ctypes.ResultBlock{BlockMeta: blockMeta, Block: block}, nil
}

// Commit gets block commit at a given height.
// If no height is provided, it will fetch the commit for the latest block.
// More: https://tendermint.com/rpc/#/Info/commit
func Commit(ctx *rpctypes.Context, heightPtr *int64) (*ctypes.ResultCommit, error) {
	storeHeight := blockStore.Height()
	height, err := getHeight(storeHeight, heightPtr)
	if err != nil {
		return nil, err
	}

	header := blockStore.LoadBlockMeta(height).Header

	// If the next block has not been committed yet,
	// use a non-canonical commit
	if height == storeHeight {
		commit := blockStore.LoadSeenCommit(height)
		return ctypes.NewResultCommit(&header, commit, false), nil
	}

	// Return the canonical commit (comes from the block at height+1)
	commit := blockStore.LoadBlockCommit(height)
	return ctypes.NewResultCommit(&header, commit, true), nil
}

// BlockResults gets ABCIResults at a given height.
// If no height is provided, it will fetch results for the latest block.
//
// Results are for the height of the block containing the txs.
// Thus response.results.deliver_tx[5] is the results of executing
// getBlock(h).Txs[5]
// More: https://tendermint.com/rpc/#/Info/block_results
func BlockResults(ctx *rpctypes.Context, heightPtr *int64) (*ctypes.ResultBlockResults, error) {
	storeHeight := blockStore.Height()
	height, err := getHeight(storeHeight, heightPtr)
	if err != nil {
		return nil, err
	}

	results, err := sm.LoadABCIResponses(stateDB, height)
	if err != nil {
		return nil, err
	}

	res := &ctypes.ResultBlockResults{
		Height:  height,
		Results: results,
	}
	return res, nil
}

func getHeight(currentHeight int64, heightPtr *int64) (int64, error) {
	if heightPtr != nil {
		height := *heightPtr
		if height <= 0 {
			return 0, fmt.Errorf("Height must be greater than 0")
		}
		if height > currentHeight {
			return 0, fmt.Errorf("Height must be less than or equal to the current blockchain height")
		}
		return height, nil
	}
	return currentHeight, nil
}