package adapter

import (
	"bytes"
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// 钉钉自定义机器人 webhook 前缀固定，配置时只需提供 access_token
const dingtalkWebhookPrefix = "https://oapi.dingtalk.com/robot/send?access_token="

type dingtalkConfig struct {
	AccessToken string `json:"access_token"`
	Secret      string `json:"secret,omitempty"`
	// WebhookURL 兼容旧配置；新配置优先使用 AccessToken
	WebhookURL string `json:"webhook_url,omitempty"`
}

func (c *dingtalkConfig) webhookURL() string {
	if c.AccessToken != "" {
		return dingtalkWebhookPrefix + c.AccessToken
	}
	return c.WebhookURL
}

type dingtalkMessage struct {
	MsgType  string      `json:"msgtype"`
	Markdown *dingtalkMD `json:"markdown"`
}

type dingtalkMD struct {
	Title string `json:"title"`
	Text  string `json:"text"`
}

type DingTalkSender struct {
	limiter *DingTalkLimiter
}

func (s *DingTalkSender) Type() string { return "dingtalk" }

func (s *DingTalkSender) Send(title, content string, config json.RawMessage) error {
	var cfg dingtalkConfig
	if err := json.Unmarshal(config, &cfg); err != nil {
		return fmt.Errorf("parse dingtalk config: %w", err)
	}

	if s.limiter != nil {
		if err := s.limiter.Acquire(context.Background(), DingTalkLimitKey(cfg.webhookURL())); err != nil {
			return fmt.Errorf("dingtalk rate limit: %w", err)
		}
	}

	reqURL := cfg.webhookURL()
	if cfg.Secret != "" {
		timestamp := time.Now().UnixMilli()
		sign := dingtalkSign(timestamp, cfg.Secret)
		reqURL = fmt.Sprintf("%s&timestamp=%d&sign=%s", reqURL, timestamp, sign)
	}

	msg := dingtalkMessage{
		MsgType: "markdown",
		Markdown: &dingtalkMD{
			Title: dingtalkTitle(title, content),
			Text:  dingtalkMarkdownText(content),
		},
	}

	body, _ := json.Marshal(msg)
	resp, err := http.Post(reqURL, "application/json", bytes.NewReader(body))
	if err != nil {
		return fmt.Errorf("dingtalk send: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		return fmt.Errorf("dingtalk returned status %d", resp.StatusCode)
	}
	return nil
}

// dingtalkTitle is the markdown.Title shown on DingTalk PC as the card header
// and in the session-list preview. Prefer the first content line (e.g. 空单开仓)
// over the internal "source: event" title.
func dingtalkTitle(fallback, content string) string {
	content = strings.ReplaceAll(content, "\r\n", "\n")
	content = strings.ReplaceAll(content, "\r", "\n")
	line, _, _ := strings.Cut(content, "\n")
	line = strings.TrimSpace(line)
	if line != "" {
		return line
	}
	if strings.TrimSpace(fallback) != "" {
		return fallback
	}
	return "通知"
}

// dingtalkMarkdownText turns template newlines into DingTalk markdown paragraph
// breaks. A single \n is collapsed to a space by DingTalk markdown, so each
// logical line must be separated by \n\n.
func dingtalkMarkdownText(content string) string {
	content = strings.ReplaceAll(content, "\r\n", "\n")
	content = strings.ReplaceAll(content, "\r", "\n")
	for strings.Contains(content, "\n\n") {
		content = strings.ReplaceAll(content, "\n\n", "\n")
	}
	return strings.ReplaceAll(content, "\n", "\n\n")
}

func dingtalkSign(timestamp int64, secret string) string {
	mac := hmac.New(sha256.New, []byte(secret))
	fmt.Fprintf(mac, "%d\n%s", timestamp, secret)
	signData := mac.Sum(nil)
	return url.QueryEscape(base64.StdEncoding.EncodeToString(signData))
}