// Package coingecko implements a Service which returns price info on cryptocurrencies from coingecko
package coingecko

import (
	"encoding/json"
	"fmt"
	"net/http"
	"strings"

	"github.com/matrix-org/go-neb/types"
	mevt "maunium.net/go/mautrix/event"
	"maunium.net/go/mautrix/id"
)

// ServiceType of the coingecko service
const ServiceType = "coingecko"

// Service represents the coingecko service. It has no Config fields.
type Service struct {
	types.DefaultService
}

type CoinList struct {
	Id     string `json:"id"`
	Symbol string `json:"symbol"`
	Name   string `json:"name"`
}

type MarketChart struct {
	Prices       [][]float32 `json:"prices"`
	MarketCaps   [][]float32 `json:"market_caps"`
	TotalVolumes [][]float32 `json:"total_volumes"`
}

func getId(query string) string {
	req, _ := http.NewRequest("GET", "https://api.coingecko.com/api/v3/coins/list", nil)
	req.Header.Set("Accept", "application/json")
	client := &http.Client{}
	resp, _ := client.Do(req)
	defer resp.Body.Close()

	var coinList *[]CoinList
	json.NewDecoder(resp.Body).Decode(&coinList)
	for _, coin := range *coinList {
		// get the coingecko id for the requested coin
		if coin.Symbol == query {
			return coin.Id
		}
	}
	// fallback to bitcoin
	return "bitcoin"
}

func getData(query string) string {
	url := fmt.Sprintf("https://api.coingecko.com/api/v3/coins/%s/market_chart?vs_currency=usd&days=1", query)
	req, _ := http.NewRequest("GET", url, nil)
	req.Header.Set("Accept", "application/json")
	client := &http.Client{}
	resp, _ := client.Do(req)
	defer resp.Body.Close()

	var coin *MarketChart
	json.NewDecoder(resp.Body).Decode(&coin)

	latestPrice := coin.Prices[len(coin.Prices)-1][1]
	marketCap := coin.MarketCaps[len(coin.MarketCaps)-1][1]
	totalVol := coin.TotalVolumes[len(coin.TotalVolumes)-1][1]
	return fmt.Sprintf("%s -- Price: $%f, Market Cap: $%.0f, 24hr Volume: $%.0f", query, latestPrice, marketCap, totalVol)
}

// Commands supported:
//    !coingecko SYMBOL
// Responds with price data on the currency
func (e *Service) Commands(cli types.MatrixClient) []types.Command {
	return []types.Command{
		{
			Path: []string{"cc"},
			Command: func(roomID id.RoomID, userID id.UserID, args []string) (interface{}, error) {
				coinId := getId(strings.Join(args, ""))
				output := getData(coinId)
				return &mevt.MessageEventContent{
					MsgType: mevt.MsgNotice,
					Body:    output,
				}, nil
			},
		},
	}
}

func init() {
	types.RegisterService(func(serviceID string, serviceUserID id.UserID, webhookEndpointURL string) types.Service {
		return &Service{
			DefaultService: types.NewDefaultService(serviceID, serviceUserID, ServiceType),
		}
	})
}