refactor: split playback proxy logic into separate handler files

internal/playback/handler/proxy_subtitle.go

@@ -0,0 +1,74 @@
+package handler
+
+import (
+	"context"
+	"errors"
+	"io"
+	"mal/internal/observability"
+	netutil "mal/pkg/net"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+func (h *PlaybackHandler) HandleProxySubtitle(c *gin.Context) {
+	targetURL, referer, ok := h.resolveProxyRequestTarget(c, "subtitle")
+	if !ok {
+		return
+	}
+
+	if data, contentType, ok := h.subtitleCache.Get(targetURL, time.Now()); ok {
+		c.Data(http.StatusOK, contentType, data)
+		return
+	}
+
+	req, err := newProxyRequest(c.Request.Context(), targetURL, referer)
+	if err != nil {
+		c.Status(http.StatusBadGateway)
+		return
+	}
+
+	resp, err := h.proxyClient.Do(req)
+	if err != nil {
+		if !errors.Is(err, context.Canceled) {
+			observability.ErrorContext(c.Request.Context(), "proxy_subtitle_upstream_failed", "playback", "", map[string]any{"target_url": targetURL}, err)
+			_ = c.Error(err).SetType(gin.ErrorTypePrivate)
+		}
+		c.Status(http.StatusBadGateway)
+		return
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	body, err := io.ReadAll(io.LimitReader(resp.Body, netutil.MiB2))
+	if err != nil {
+		observability.ErrorContext(c.Request.Context(), "proxy_subtitle_read_failed", "playback", "", map[string]any{"target_url": targetURL}, err)
+		_ = c.Error(err).SetType(gin.ErrorTypePrivate)
+		c.Status(http.StatusBadGateway)
+		return
+	}
+
+	contentType := resp.Header.Get("Content-Type")
+	if contentType == "" {
+		contentType = detectSubtitleType(targetURL)
+	}
+
+	h.subtitleCache.Set(targetURL, body, contentType, time.Now())
+
+	c.Data(http.StatusOK, contentType, body)
+}
+
+func detectSubtitleType(url string) string {
+	lower := strings.ToLower(url)
+	switch {
+	case strings.Contains(lower, ".vtt"):
+		return "text/vtt"
+	case strings.Contains(lower, ".srt"):
+		return "text/plain; charset=utf-8"
+	case strings.Contains(lower, ".ass") || strings.Contains(lower, ".ssa"):
+		return "text/plain; charset=utf-8"
+	default:
+		return "text/plain; charset=utf-8"
+	}
+}