feat(emby): support multiple connection lines for remote mount (#9)

Add account-level multi-line configuration for emby_remote mounts.
Lines are stored in strm_accounts.config as a urls JSON array with
backward compatibility for the legacy single url field. The backend
automatically fails over to the next line on connection errors and
persists the working active_line index.

Frontend: multi-line editor on Emby mount page and STRM account dialog
with add/remove/reorder, line names, and URL validation.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: truewhile <truewhile@users.noreply.github.com>

internal/service/emby_remote_lines.go

@@ -0,0 +1,185 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"github.com/ShukeBta/MMTL/internal/model"
+)
+
+// EmbyRemoteLine 表示同一 Emby 服务器的一条接入线路（内网/外网/CDN 等）。
+type EmbyRemoteLine struct {
+	Name string `json:"name"`
+	URL  string `json:"url"`
+}
+
+func normalizeEmbyRemoteURL(raw string) string {
+	u := strings.TrimRight(strings.TrimSpace(raw), "/")
+	if u == "" {
+		return ""
+	}
+	if !strings.HasPrefix(u, "http://") && !strings.HasPrefix(u, "https://") {
+		return ""
+	}
+	return u
+}
+
+// NormalizeEmbyRemoteLines 去掉空 URL，并规范每条线路地址。
+func NormalizeEmbyRemoteLines(lines []EmbyRemoteLine) []EmbyRemoteLine {
+	out := make([]EmbyRemoteLine, 0, len(lines))
+	for _, line := range lines {
+		u := normalizeEmbyRemoteURL(line.URL)
+		if u == "" {
+			continue
+		}
+		out = append(out, EmbyRemoteLine{
+			Name: strings.TrimSpace(line.Name),
+			URL:  u,
+		})
+	}
+	return out
+}
+
+// ParseEmbyRemoteLines 从账号配置 JSON 中解析线路列表。
+// 兼容旧版单字段 url；urls 为 JSON 数组字符串。
+func ParseEmbyRemoteLines(raw map[string]string) ([]EmbyRemoteLine, int, error) {
+	active := 0
+	if v := strings.TrimSpace(raw["active_line"]); v != "" {
+		if n, err := strconv.Atoi(v); err == nil && n >= 0 {
+			active = n
+		}
+	}
+	if urlsJSON := strings.TrimSpace(raw["urls"]); urlsJSON != "" {
+		var lines []EmbyRemoteLine
+		if err := json.Unmarshal([]byte(urlsJSON), &lines); err != nil {
+			return nil, 0, fmt.Errorf("解析 Emby 线路列表: %w", err)
+		}
+		lines = NormalizeEmbyRemoteLines(lines)
+		if len(lines) == 0 {
+			return nil, 0, errors.New("至少配置一条 Emby 线路")
+		}
+		if active >= len(lines) {
+			active = 0
+		}
+		return lines, active, nil
+	}
+	if u := normalizeEmbyRemoteURL(raw["url"]); u != "" {
+		return []EmbyRemoteLine{{URL: u}}, 0, nil
+	}
+	return nil, 0, errors.New("缺少 Emby 地址")
+}
+
+// EncodeEmbyRemoteLines 序列化线路列表，并返回兼容旧版的 primary URL。
+func EncodeEmbyRemoteLines(lines []EmbyRemoteLine) (urlsJSON string, primaryURL string, err error) {
+	lines = NormalizeEmbyRemoteLines(lines)
+	if len(lines) == 0 {
+		return "", "", errors.New("至少配置一条 Emby 线路")
+	}
+	data, err := json.Marshal(lines)
+	if err != nil {
+		return "", "", err
+	}
+	return string(data), lines[0].URL, nil
+}
+
+func (r *EmbyRemoteService) withLine(cfg *EmbyRemoteConfig, index int) *EmbyRemoteConfig {
+	if cfg == nil {
+		return nil
+	}
+	copy := *cfg
+	if index >= 0 && index < len(cfg.Lines) {
+		copy.BaseURL = normalizeEmbyRemoteURL(cfg.Lines[index].URL)
+		copy.ActiveLine = index
+	}
+	return &copy
+}
+
+func (r *EmbyRemoteService) lineOrder(cfg *EmbyRemoteConfig) []int {
+	if cfg == nil || len(cfg.Lines) == 0 {
+		return []int{0}
+	}
+	if len(cfg.Lines) == 1 {
+		return []int{0}
+	}
+	active := cfg.ActiveLine
+	if active < 0 || active >= len(cfg.Lines) {
+		active = 0
+	}
+	order := []int{active}
+	for i := range cfg.Lines {
+		if i != active {
+			order = append(order, i)
+		}
+	}
+	return order
+}
+
+func isEmbyLineFailoverError(err error) bool {
+	if err == nil {
+		return false
+	}
+	msg := strings.ToLower(err.Error())
+	if strings.Contains(msg, "登录失败") ||
+		strings.Contains(msg, "未返回 accesstoken") ||
+		strings.Contains(msg, "缺少 emby 凭据") ||
+		strings.Contains(msg, "认证重试失败") {
+		return false
+	}
+	var urlErr *url.Error
+	if errors.As(err, &urlErr) {
+		return true
+	}
+	return strings.Contains(msg, "连接远程 emby") ||
+		strings.Contains(msg, "请求远程 emby 失败") ||
+		strings.Contains(msg, "dial tcp") ||
+		strings.Contains(msg, "connection refused") ||
+		strings.Contains(msg, "no such host") ||
+		strings.Contains(msg, "timeout") ||
+		strings.Contains(msg, "i/o timeout")
+}
+
+func (r *EmbyRemoteService) persistActiveLine(ctx context.Context, acct *model.StrmAccount, cfg *EmbyRemoteConfig, lineIndex int) error {
+	if acct == nil || cfg == nil || lineIndex < 0 || lineIndex >= len(cfg.Lines) {
+		return nil
+	}
+	raw := map[string]string{}
+	if strings.TrimSpace(acct.Config) != "" {
+		_ = json.Unmarshal([]byte(acct.Config), &raw)
+	}
+	raw["active_line"] = strconv.Itoa(lineIndex)
+	raw["url"] = cfg.Lines[lineIndex].URL
+	data, err := json.Marshal(raw)
+	if err != nil {
+		return err
+	}
+	acct.Config = string(data)
+	cfg.ActiveLine = lineIndex
+	cfg.BaseURL = normalizeEmbyRemoteURL(cfg.Lines[lineIndex].URL)
+	return r.repo.StrmAccount.Update(ctx, acct)
+}
+
+func (r *EmbyRemoteService) adoptWorkingLine(ctx context.Context, acct *model.StrmAccount, cfg *EmbyRemoteConfig, lineIndex int) {
+	if cfg == nil || lineIndex < 0 || lineIndex >= len(cfg.Lines) {
+		return
+	}
+	if lineIndex == cfg.ActiveLine {
+		return
+	}
+	_ = r.persistActiveLine(ctx, acct, cfg, lineIndex)
+}
+
+// LinesOf 返回账号已配置的线路（供管理界面回显，不含敏感信息）。
+func (r *EmbyRemoteService) LinesOf(acct *model.StrmAccount) ([]EmbyRemoteLine, int, error) {
+	raw := map[string]string{}
+	if acct != nil && strings.TrimSpace(acct.Config) != "" {
+		if err := json.Unmarshal([]byte(acct.Config), &raw); err != nil {
+			return nil, 0, err
+		}
+	}
+	return ParseEmbyRemoteLines(raw)
+}