package gzev

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"regexp"
	"strings"
	"time"
)

type ServerChan struct {
	SendKey, SessionPath, UploadURL string
	HTTP                            *http.Client
}

func ServerChanFromEnv() ServerChan {
	path := os.Getenv("GZEV_SESSION_FILE")
	if path == "" {
		path = "/var/lib/lingniu-gzev/session.json"
	}
	return ServerChan{SendKey: strings.TrimSpace(os.Getenv("SERVERCHAN_SENDKEY")), SessionPath: path, UploadURL: os.Getenv("GZEV_SESSION_UPLOAD_URL"), HTTP: &http.Client{Timeout: 20 * time.Second, CheckRedirect: func(_ *http.Request, _ []*http.Request) error { return http.ErrUseLastResponse }}}
}
func (s ServerChan) Send(ctx context.Context) error     { return s.send(ctx, false) }
func (s ServerChan) SendTest(ctx context.Context) error { return s.send(ctx, true) }
func (s ServerChan) send(ctx context.Context, test bool) error {
	if !regexp.MustCompile(`^SCT[A-Za-z0-9]{8,253}$`).MatchString(s.SendKey) {
		return errors.New("ServerChan SendKey missing or invalid")
	}
	if s.UploadURL != "https://vehicle.d.lnoneos.com/gzev/session/" {
		return errors.New("unsupported recovery URL")
	}
	code, err := EnsureRecoveryCode(s.SessionPath + ".recovery.json")
	if err != nil {
		return errors.New("cannot create recovery code")
	}
	title := "广州里程采集登录失效"
	intro := "定时采集前验证未通过，当前采集已暂停。请登录广州平台并提交新的登录状态。"
	if test {
		title = "广州里程采集推送测试"
		intro = "这是 Server酱推送渠道连通性测试，不表示登录状态已失效。以后采集前发现登录失效，将通过此渠道通知。"
	}
	body := fmt.Sprintf("%s\n\n[打开登录状态上传页面](%s)\n\n通知恢复码：\n\n`%s`\n\n恢复码有效期 48 小时，成功上传后失效。上传页面支持粘贴 token 或上传会话 JSON；验证通过后，下次定时采集自动继续。请勿转发恢复码。", intro, s.UploadURL, code)
	return s.SendMessage(ctx, title, body)
}

// SendMessage uses the existing configured channel without creating a recovery ticket.
func (s ServerChan) SendMessage(ctx context.Context, title, body string) error {
	if !regexp.MustCompile(`^SCT[A-Za-z0-9]{8,253}$`).MatchString(s.SendKey) {
		return errors.New("ServerChan SendKey missing or invalid")
	}
	form := url.Values{"title": {title}, "desp": {body}}
	req, err := http.NewRequestWithContext(ctx, "POST", "https://sctapi.ftqq.com/"+s.SendKey+".send", strings.NewReader(form.Encode()))
	if err != nil {
		return errors.New("cannot create push request")
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	resp, err := s.HTTP.Do(req)
	if err != nil {
		return errors.New("ServerChan transport failure; delivery status may be unknown")
	}
	defer resp.Body.Close()
	var result struct {
		Code *int `json:"code"`
		Data struct {
			Errno *int `json:"errno"`
		} `json:"data"`
	}
	if json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&result) != nil || resp.StatusCode != 200 || result.Code == nil {
		return errors.New("ServerChan did not confirm acceptance")
	}
	if *result.Code != 0 {
		return fmt.Errorf("ServerChan rejected push (code=%d)", *result.Code)
	}
	if result.Data.Errno != nil && *result.Data.Errno != 0 {
		return fmt.Errorf("ServerChan channel error (errno=%d)", *result.Data.Errno)
	}
	return nil
}