feat(backend): cover/file/pages endpoints — immutable URLs, Range, disk+redis caches

backend/internal/api/content.go

@@ -0,0 +1,184 @@
+package api
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/gin-gonic/gin"
+
+	"booklib/internal/bookfile"
+	"booklib/internal/store"
+)
+
+const defaultCover = `<svg xmlns="http://www.w3.org/2000/svg" width="120" height="170"><rect width="120" height="170" rx="6" fill="#2a2a33"/><path d="M30 25h60v120H30z" fill="#3a3a45"/><path d="M30 25h60M60 25v120" stroke="#555" stroke-width="2"/></svg>`
+
+func (a *api) bookRoot(c *gin.Context, b store.Book) (string, bool) {
+	lib, ok := a.getLibRow(c, b.LibraryID)
+	if !ok {
+		return "", false
+	}
+	return a.libRoot(c, lib)
+}
+
+func (a *api) immutable(c *gin.Context) {
+	c.Header("Cache-Control", "public, max-age=31536000, immutable")
+}
+
+func (a *api) serveCover(c *gin.Context) {
+	b, ok := a.bookFromParam(c)
+	if !ok {
+		return
+	}
+	a.immutable(c)
+	dir := bookfile.CoverDir(a.cfg.CacheDir, bookfile.DirKey(b.ID, bookfile.Hash(b.FileSize, b.ModTS)))
+	if entries, err := os.ReadDir(dir); err == nil && len(entries) > 0 {
+		http.ServeFile(c.Writer, c.Request, filepath.Join(dir, entries[0].Name()))
+		return
+	}
+	c.Data(http.StatusOK, "image/svg+xml", []byte(defaultCover))
+}
+
+func (a *api) serveFile(c *gin.Context) {
+	b, ok := a.bookFromParam(c)
+	if !ok {
+		return
+	}
+	root, ok := a.bookRoot(c, b)
+	if !ok {
+		return
+	}
+	abs, perr := absBookPath(root, b)
+	if perr != nil {
+		err(c, http.StatusForbidden, "forbidden", "unsafe path")
+		return
+	}
+	c.Header("ETag", `"`+bookfile.Hash(b.FileSize, b.ModTS)+`"`)
+	c.Header("Cache-Control", "private, must-revalidate")
+	http.ServeFile(c.Writer, c.Request, abs)
+}
+
+func (a *api) openBook(c *gin.Context, b store.Book, root string) (*os.File, int64, bool) {
+	abs, perr := absBookPath(root, b)
+	if perr != nil {
+		err(c, http.StatusForbidden, "forbidden", "unsafe path")
+		return nil, 0, false
+	}
+	f, perr := os.Open(abs)
+	if perr != nil {
+		err(c, http.StatusNotFound, "not_found", "file missing on disk")
+		return nil, 0, false
+	}
+	st, perr := f.Stat()
+	if perr != nil {
+		f.Close()
+		err(c, http.StatusInternalServerError, "internal", "stat")
+		return nil, 0, false
+	}
+	return f, st.Size(), true
+}
+
+func (a *api) pageIndex(c *gin.Context, b store.Book, root string) ([]string, error) {
+	hash := bookfile.Hash(b.FileSize, b.ModTS)
+	key := fmt.Sprintf("pagesidx:%d:%s", b.ID, hash)
+	if v, ok := a.rdb.Get(c, key); ok {
+		return strings.Split(v, "\n"), nil
+	}
+	f, size, ok := a.openBook(c, b, root)
+	if !ok {
+		return nil, os.ErrNotExist
+	}
+	defer f.Close()
+	idx, e := bookfile.PageIndex(f, size)
+	if e != nil {
+		return nil, e
+	}
+	a.rdb.Set(c, key, strings.Join(idx, "\n"), 7*24*time.Hour)
+	return idx, nil
+}
+
+func (a *api) pagesCount(c *gin.Context) {
+	b, ok := a.bookFromParam(c)
+	if !ok {
+		return
+	}
+	if b.Format != "cbz" {
+		err(c, http.StatusBadRequest, "bad_request", "pages only for cbz")
+		return
+	}
+	root, ok := a.bookRoot(c, b)
+	if !ok {
+		return
+	}
+	idx, e := a.pageIndex(c, b, root)
+	if e != nil {
+		err(c, http.StatusUnprocessableEntity, "broken", e.Error())
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"count": len(idx)})
+}
+
+func (a *api) page(c *gin.Context) {
+	b, ok := a.bookFromParam(c)
+	if !ok {
+		return
+	}
+	if b.Format != "cbz" {
+		err(c, http.StatusBadRequest, "bad_request", "pages only for cbz")
+		return
+	}
+	n, e := strconv.Atoi(c.Param("n"))
+	if e != nil || n < 0 {
+		err(c, http.StatusBadRequest, "bad_request", "bad page number")
+		return
+	}
+	root, ok := a.bookRoot(c, b)
+	if !ok {
+		return
+	}
+	idx, e := a.pageIndex(c, b, root)
+	if e != nil {
+		err(c, http.StatusUnprocessableEntity, "broken", e.Error())
+		return
+	}
+	if n >= len(idx) {
+		err(c, http.StatusNotFound, "not_found", "no such page")
+		return
+	}
+	ext := strings.ToLower(filepath.Ext(idx[n]))
+	dir := bookfile.PagesDir(a.cfg.CacheDir, bookfile.DirKey(b.ID, bookfile.Hash(b.FileSize, b.ModTS)))
+	dst := filepath.Join(dir, strconv.Itoa(n)+ext)
+	if _, e := os.Stat(dst); e != nil { // miss → 解压落盘(并发重做同页幂等,唯一 tmp 名 + rename 原子)
+		f, size, ok := a.openBook(c, b, root)
+		if !ok {
+			return
+		}
+		defer f.Close()
+		data, e := bookfile.ReadEntry(f, size, idx[n])
+		if e != nil {
+			err(c, http.StatusInternalServerError, "internal", "extract page")
+			return
+		}
+		if e := os.MkdirAll(dir, 0o755); e != nil {
+			err(c, http.StatusInternalServerError, "internal", "cache dir")
+			return
+		}
+		tmp := fmt.Sprintf("%s.tmp-%d", dst, time.Now().UnixNano())
+		if e := os.WriteFile(tmp, data, 0o644); e != nil {
+			os.Remove(tmp)
+			err(c, http.StatusInternalServerError, "internal", "write cache")
+			return
+		}
+		if e := os.Rename(tmp, dst); e != nil {
+			os.Remove(tmp)
+			err(c, http.StatusInternalServerError, "internal", "rename cache")
+			return
+		}
+	}
+	a.immutable(c)
+	http.ServeFile(c.Writer, c.Request, dst)
+}