// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package merlion

import (
	"fmt"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/consensus"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/rpc"
)

// API is a user facing RPC API to allow controlling the validator and voting
// mechanisms of the proof-of-authority scheme.
type API struct {
	chain   consensus.ChainHeaderReader
	merlion *Merlion
}

// GetSnapshot retrieves the state snapshot at a given block.
func (api *API) GetSnapshot(number *rpc.BlockNumber) (*Snapshot, error) {
	// Retrieve the requested block number (or current if none requested)
	var header *types.Header
	if number == nil || *number == rpc.LatestBlockNumber {
		header = api.chain.CurrentHeader()
	} else {
		header = api.chain.GetHeaderByNumber(uint64(number.Int64()))
	}
	// Ensure we have an actually valid block and return its snapshot
	if header == nil {
		return nil, errUnknownBlock
	}
	return api.merlion.snapshot(api.chain, header.Number.Uint64(), header.Hash(), nil)
}

// GetSnapshotAtHash retrieves the state snapshot at a given block.
func (api *API) GetSnapshotAtHash(hash common.Hash) (*Snapshot, error) {
	header := api.chain.GetHeaderByHash(hash)
	if header == nil {
		return nil, errUnknownBlock
	}
	return api.merlion.snapshot(api.chain, header.Number.Uint64(), header.Hash(), nil)
}

// GetValidators retrieves the list of authorized validators at the specified block.
func (api *API) GetValidators(number *rpc.BlockNumber) ([]common.Address, error) {
	// Retrieve the requested block number (or current if none requested)
	var header *types.Header
	if number == nil || *number == rpc.LatestBlockNumber {
		header = api.chain.CurrentHeader()
	} else {
		header = api.chain.GetHeaderByNumber(uint64(number.Int64()))
	}
	// Ensure we have an actually valid block and return the validators from its snapshot
	if header == nil {
		return nil, errUnknownBlock
	}
	snap, err := api.merlion.snapshot(api.chain, header.Number.Uint64(), header.Hash(), nil)
	if err != nil {
		return nil, err
	}
	return snap.validators(), nil
}

// GetValidatorsAtHash retrieves the list of authorized validators at the specified block.
func (api *API) GetValidatorsAtHash(hash common.Hash) ([]common.Address, error) {
	header := api.chain.GetHeaderByHash(hash)
	if header == nil {
		return nil, errUnknownBlock
	}
	snap, err := api.merlion.snapshot(api.chain, header.Number.Uint64(), header.Hash(), nil)
	if err != nil {
		return nil, err
	}
	return snap.validators(), nil
}

type status struct {
	InturnPercent float64                `json:"inturnPercent"`
	SigningStatus map[common.Address]int `json:"sealerActivity"`
	NumBlocks     uint64                 `json:"numBlocks"`
}

// Status returns the status of the last N blocks,
// - the number of active validators,
// - the number of validators,
// - the percentage of in-turn blocks
func (api *API) Status() (*status, error) {
	var (
		numBlocks = uint64(64)
		header    = api.chain.CurrentHeader()
		// diff      = uint64(0)
		optimals = 0
	)
	snap, err := api.merlion.snapshot(api.chain, header.Number.Uint64(), header.Hash(), nil)
	if err != nil {
		return nil, err
	}
	var (
		validators = snap.validators()
		end        = header.Number.Uint64()
		start      = end - numBlocks
	)
	if numBlocks > end {
		start = 1
		numBlocks = end - start
	}
	signStatus := make(map[common.Address]int)
	for _, s := range validators {
		signStatus[s] = 0
	}
	for n := start; n < end; n++ {
		h := api.chain.GetHeaderByNumber(n)
		if h == nil {
			return nil, fmt.Errorf("missing block %d", n)
		}
		if h.Difficulty.Cmp(diffInTurn) == 0 {
			optimals++
		}
		// diff += h.Difficulty.Uint64()
		sealer, err := api.merlion.Author(h)
		if err != nil {
			return nil, err
		}
		signStatus[sealer]++
	}
	return &status{
		InturnPercent: float64(100*optimals) / float64(numBlocks),
		SigningStatus: signStatus,
		NumBlocks:     numBlocks,
	}, nil
}
