package telegram

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strconv"
	"time"

	"laodingbot/internal/logger"
)

type Bot struct {
	token       string
	baseURL     string
	http        *http.Client
	pollTimeout int
	log         *logger.Logger
}

type IncomingMessage struct {
	ChatID string
	UserID string
	Text   string
}

func NewBot(token string, pollTimeout int, log *logger.Logger) (*Bot, error) {
	if token == "" {
		return nil, fmt.Errorf("empty telegram token")
	}
	if pollTimeout <= 0 {
		pollTimeout = 30
	}
	return &Bot{
		token:       token,
		baseURL:     "https://api.telegram.org/bot" + token,
		http:        &http.Client{Timeout: 70 * time.Second},
		pollTimeout: pollTimeout,
		log:         log,
	}, nil
}

func (b *Bot) Run(ctx context.Context, handler func(context.Context, IncomingMessage) (string, error)) error {
	if b.log != nil {
		b.log.Infof("telegram polling started timeout=%ds", b.pollTimeout)
	}
	offset := 0
	for {
		select {
		case <-ctx.Done():
			if b.log != nil {
				b.log.Infof("telegram polling stopped: %v", ctx.Err())
			}
			return ctx.Err()
		default:
		}

		updates, err := b.getUpdates(ctx, offset)
		if err != nil {
			if b.log != nil {
				b.log.Errorf("telegram getUpdates failed err=%v", err)
			}
			return err
		}
		if b.log != nil && len(updates) > 0 {
			b.log.Debugf("telegram updates received count=%d offset=%d", len(updates), offset)
		}

		for _, u := range updates {
			offset = u.UpdateID + 1
			if u.Message.Text == "" {
				continue
			}
			in := IncomingMessage{
				ChatID: strconv.FormatInt(u.Message.Chat.ID, 10),
				UserID: strconv.FormatInt(u.Message.From.ID, 10),
				Text:   u.Message.Text,
			}
			if b.log != nil {
				b.log.Infof("telegram message received chat_id=%s user_id=%s text_len=%d", in.ChatID, in.UserID, len(in.Text))
			}
			resp, err := handler(ctx, in)
			if err != nil {
				if b.log != nil {
					b.log.Errorf("telegram handler failed chat_id=%s err=%v", in.ChatID, err)
				}
				resp = "处理失败: " + err.Error()
			}
			if err := b.sendMessage(ctx, in.ChatID, resp); err != nil {
				if b.log != nil {
					b.log.Errorf("telegram sendMessage failed chat_id=%s err=%v", in.ChatID, err)
				}
				return err
			}
			if b.log != nil {
				b.log.Debugf("telegram message sent chat_id=%s text_len=%d", in.ChatID, len(resp))
			}
		}
	}
}

type updatesResponse struct {
	OK     bool     `json:"ok"`
	Result []update `json:"result"`
}

type update struct {
	UpdateID int `json:"update_id"`
	Message  struct {
		Text string `json:"text"`
		Chat struct {
			ID int64 `json:"id"`
		} `json:"chat"`
		From struct {
			ID int64 `json:"id"`
		} `json:"from"`
	} `json:"message"`
}

func (b *Bot) getUpdates(ctx context.Context, offset int) ([]update, error) {
	url := fmt.Sprintf("%s/getUpdates?timeout=%d&offset=%d", b.baseURL, b.pollTimeout, offset)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return nil, err
	}
	resp, err := b.http.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	raw, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}
	var out updatesResponse
	if err := json.Unmarshal(raw, &out); err != nil {
		if b.log != nil {
			b.log.Errorf("telegram parse getUpdates response failed err=%v", err)
		}
		return nil, err
	}
	if !out.OK {
		if b.log != nil {
			b.log.Warnf("telegram getUpdates not ok")
		}
		return nil, fmt.Errorf("telegram getUpdates failed")
	}
	return out.Result, nil
}

func (b *Bot) sendMessage(ctx context.Context, chatID, text string) error {
	payload := map[string]string{
		"chat_id": chatID,
		"text":    text,
	}
	bts, err := json.Marshal(payload)
	if err != nil {
		return err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, b.baseURL+"/sendMessage", bytes.NewReader(bts))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	resp, err := b.http.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		if b.log != nil {
			b.log.Warnf("telegram sendMessage bad status=%d chat_id=%s", resp.StatusCode, chatID)
		}
		return fmt.Errorf("telegram sendMessage status: %d", resp.StatusCode)
	}
	return nil
}