package services

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"math"
	"net"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	beego "github.com/beego/beego/v2/server/web"
)

type KlineItem struct {
	OpenTime         int64  `json:"open_time"`
	Open             string `json:"open"`
	High             string `json:"high"`
	Low              string `json:"low"`
	Close            string `json:"close"`
	Volume           string `json:"volume"`
	CloseTime        int64  `json:"close_time"`
	QuoteAssetVolume string `json:"quote_asset_volume"`
	NumberOfTrades   int64  `json:"number_of_trades"`
	TakerBuyBase     string `json:"taker_buy_base"`
	TakerBuyQuote    string `json:"taker_buy_quote"`
}

type KlineService struct{}

func getIntConfig(key string, fallback int) int {
	raw, err := beego.AppConfig.String(key)
	if err != nil || strings.TrimSpace(raw) == "" {
		return fallback
	}
	v, err := strconv.Atoi(raw)
	if err != nil || v <= 0 {
		return fallback
	}
	return v
}

func getStringConfig(key, fallback string) string {
	v, err := beego.AppConfig.String(key)
	if err != nil || strings.TrimSpace(v) == "" {
		return fallback
	}
	return strings.TrimSpace(v)
}

func getBaseURLs() []string {
	// comma separated base urls, example:
	// https://api.binance.com,https://api1.binance.com,https://api2.binance.com
	raw := getStringConfig(
		"kline_api_base_urls",
		"https://api.binance.com,https://api1.binance.com,https://api2.binance.com,https://api3.binance.com",
	)
	parts := strings.Split(raw, ",")
	out := make([]string, 0, len(parts))
	for _, p := range parts {
		p = strings.TrimSpace(strings.TrimRight(p, "/"))
		if p != "" {
			out = append(out, p)
		}
	}
	if len(out) == 0 {
		return []string{"https://api.binance.com"}
	}
	return out
}

func getBoolConfig(key string, fallback bool) bool {
	raw, err := beego.AppConfig.String(key)
	if err != nil || strings.TrimSpace(raw) == "" {
		return fallback
	}
	v, err := strconv.ParseBool(strings.TrimSpace(raw))
	if err != nil {
		return fallback
	}
	return v
}

func newKlineHTTPClient(timeoutMS int) *http.Client {
	dialer := &net.Dialer{
		Timeout:   time.Duration(timeoutMS) * time.Millisecond,
		KeepAlive: 30 * time.Second,
	}

	useSystemProxy := getBoolConfig("kline_use_system_proxy", false)
	var proxyFn func(*http.Request) (*url.URL, error)
	if useSystemProxy {
		proxyFn = http.ProxyFromEnvironment
	}

	transport := &http.Transport{
		Proxy: proxyFn,
		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
			return dialer.DialContext(ctx, "tcp4", addr)
		},
		TLSHandshakeTimeout: time.Duration(timeoutMS) * time.Millisecond,
		IdleConnTimeout:     60 * time.Second,
	}
	return &http.Client{
		Timeout:   time.Duration(timeoutMS) * time.Millisecond,
		Transport: transport,
	}
}

func normalizeKlineInterval(interval string) (string, error) {
	s := strings.TrimSpace(strings.ToLower(interval))
	switch s {
	case "hour", "h", "1h", "hourly":
		return "1h", nil
	case "day", "d", "1d", "daily":
		return "1d", nil
	case "week", "w", "1w", "weekly":
		return "1w", nil
	case "month", "m", "1m", "1mo", "1mon", "1month", "monthly":
		return "1M", nil
	default:
		return "", errors.New("interval must be one of: hour/day/week/month")
	}
}

func asString(v interface{}) string {
	s, ok := v.(string)
	if ok {
		return s
	}
	return fmt.Sprint(v)
}

func asInt64(v interface{}) int64 {
	switch vv := v.(type) {
	case int64:
		return vv
	case int:
		return int64(vv)
	case float64:
		// json.Unmarshal decodes numbers as float64 by default.
		return int64(math.Round(vv))
	case json.Number:
		n, _ := vv.Int64()
		return n
	case string:
		n, _ := strconv.ParseInt(strings.TrimSpace(vv), 10, 64)
		return n
	default:
		s := strings.TrimSpace(fmt.Sprint(v))
		if strings.ContainsAny(s, ".eE") {
			f, _ := strconv.ParseFloat(s, 64)
			return int64(math.Round(f))
		}
		n, _ := strconv.ParseInt(s, 10, 64)
		return n
	}
}

func (s *KlineService) FetchKlines(symbol, interval string, limit int, startTime, endTime int64) ([]KlineItem, error) {
	if strings.TrimSpace(symbol) == "" {
		symbol = "BTCUSDT"
	}
	symbol = strings.ToUpper(strings.TrimSpace(symbol))

	apiInterval, err := normalizeKlineInterval(interval)
	if err != nil {
		return nil, err
	}

	if limit <= 0 {
		limit = 200
	}
	if limit > 1000 {
		limit = 1000
	}

	timeoutMS := getIntConfig("kline_http_timeout_ms", 12000)
	retries := getIntConfig("kline_http_retries", 2)
	if retries < 1 {
		retries = 1
	}

	client := newKlineHTTPClient(timeoutMS)
	baseURLs := getBaseURLs()
	var body []byte
	var lastErr error

	for _, base := range baseURLs {
		for i := 0; i < retries; i++ {
			u, _ := url.Parse(base + "/api/v3/klines")
			q := u.Query()
			q.Set("symbol", symbol)
			q.Set("interval", apiInterval)
			q.Set("limit", strconv.Itoa(limit))
			if startTime > 0 {
				q.Set("startTime", strconv.FormatInt(startTime, 10))
			}
			if endTime > 0 {
				q.Set("endTime", strconv.FormatInt(endTime, 10))
			}
			u.RawQuery = q.Encode()

			req, err := http.NewRequest(http.MethodGet, u.String(), nil)
			if err != nil {
				lastErr = err
				continue
			}
			req.Header.Set("Accept", "application/json")
			req.Header.Set("User-Agent", "think-go-kline/1.0")

			resp, err := client.Do(req)
			if err != nil {
				lastErr = fmt.Errorf("request %s failed: %w", base, err)
				continue
			}

			body, err = io.ReadAll(resp.Body)
			resp.Body.Close()
			if err != nil {
				lastErr = fmt.Errorf("read %s response failed: %w", base, err)
				continue
			}
			if resp.StatusCode != http.StatusOK {
				lastErr = fmt.Errorf("kline api %s error: status=%d body=%s", base, resp.StatusCode, string(body))
				continue
			}

			lastErr = nil
			break
		}
		if lastErr == nil {
			break
		}
	}

	if lastErr != nil {
		return nil, fmt.Errorf("all kline endpoints failed: %w", lastErr)
	}

	var raw [][]interface{}
	if err := json.Unmarshal(body, &raw); err != nil {
		return nil, err
	}

	out := make([]KlineItem, 0, len(raw))
	for _, row := range raw {
		if len(row) < 11 {
			continue
		}
		out = append(out, KlineItem{
			OpenTime:         asInt64(row[0]),
			Open:             asString(row[1]),
			High:             asString(row[2]),
			Low:              asString(row[3]),
			Close:            asString(row[4]),
			Volume:           asString(row[5]),
			CloseTime:        asInt64(row[6]),
			QuoteAssetVolume: asString(row[7]),
			NumberOfTrades:   asInt64(row[8]),
			TakerBuyBase:     asString(row[9]),
			TakerBuyQuote:    asString(row[10]),
		})
	}

	return out, nil
}