feat(sync): server-side position authority — verify/heal progress anchors

Progress submissions now carry (percentage, context_text, epubcfi) and
the server becomes the position authority:

- VerifyProgressAnchor resolves the submitted standard CFI against the
  book's own XHTML, extracts the text at the anchor, and cross-checks it
  with the submitted context_text. A mismatch heals the anchor by text
  search (percentage disambiguates repeats) instead of storing a bad
  position.
- The anchor's block element is derived as a cssSelector plus a block-
  relative character offset, and served on progress GET alongside the
  anchor document's href — readium-native handles that let clients
  re-open a book without parsing CFIs themselves.
- context_text-only submissions (no CFI — the dumb-client tier) are
  anchored structurally from the context text.

Motivation: cross-client progress sync (web foliate CFIs, KOReader CRE
xpointers, readium-native apps) previously trusted each client's own
locator math; the app's EPUB restore drifted ±pages because readium's
paginator does not lay out far-from-viewport columns and the foliate-
ported CFI walk ran against readium's mutated WebView DOM. Server-side
verification heals both classes at ingest.
This commit is contained in:
John O'Keefe
2026-09-26 14:43:34 -04:00
parent 1c1f5cf1bb
commit aec226af1a
6 changed files with 572 additions and 0 deletions
+3
View File
@@ -121,6 +121,9 @@ func main() {
// Create library service
libraryService := services.NewLibraryService(queries)
// The progress service verifies submitted anchors against the book
// itself — it needs to resolve library-relative file paths.
progressService.SetMediaPathResolver(libraryService)
// Sync Go AllowedExtensions into DB so API clients see correct extensions
libraryService.SyncAllowedExtensions(context.Background())
+31
View File
@@ -953,6 +953,37 @@ func (mh *MediaHandler) GetMediaReadingProgress(c *echo.Context) error {
"last_sync_timestamp": progress.LastSyncTimestamp,
}
// Position authority: re-verify the stored anchor and derive the
// client-facing handles (cssSelector + anchor document href) server-
// side, so clients scroll to an address instead of parsing CFIs.
if progress.Epubcfi.Valid && wsync.IsConvertibleFormat(progress.FormatGroup) && mh.libraryService != nil {
contextText := ""
if progress.ContextText.Valid {
contextText = progress.ContextText.String
}
pct := 0.0
if progress.Percentage.Valid {
pct = progress.Percentage.Float64
}
if mediaItem, err := mh.db.GetMediaItem(c.Request().Context(), pgtype.UUID{Bytes: mediaUUID, Valid: true}); err == nil {
if path, perr := mh.libraryService.ResolveMediaPath(c.Request().Context(), mediaItem.LibraryID, mediaItem.FilePath); perr == nil && path != "" {
if finalCFI, sel, href, charOff, _, _, verr := wsync.VerifyProgressAnchor(path, progress.Epubcfi.String, contextText, pct); verr == nil && sel != "" {
resp["css_selector"] = sel
resp["anchor_href"] = href
if charOff != nil {
resp["char_offset"] = *charOff
}
if finalCFI != "" {
resp["epubcfi"] = finalCFI
}
}
}
}
}
if progress.ContextText.Valid {
resp["context_text"] = progress.ContextText.String
}
return c.JSON(http.StatusOK, resp)
}
+315
View File
@@ -0,0 +1,315 @@
package sync
// Ingest-side position authority for reading progress.
//
// Clients submit (percentage, context_text, epubcfi). The epubcfi is a
// standard wrapped CFI — epubcfi(/6/N!/…) — resolvable against the same
// document this package parses, so every submission is INDEPENDENTLY
// verified: the text at the resolved anchor is extracted and compared
// with the submitted context. A mismatch (or an unresolvable anchor)
// heals the position by text search, with the submitted percentage
// disambiguating repeated phrases, instead of trusting a client-side
// projection. This keeps buggy clients from poisoning stored positions:
// a resolver that silently returns "wherever I'm currently scrolled"
// fails the context check and gets healed to the true location.
//
// The anchor's block element is also derived as a cssSelector plus a
// block-relative character offset and served back — the readium-native
// handle clients scroll to, so they never have to parse or trust CFIs
// themselves.
//
// Note: readium-based clients number their readingOrder excluding
// linear="no" spine items, while this package's spine index follows the
// OPF spine as written. The spine index is therefore internal-only;
// client-facing responses carry the anchor document's href instead.
import (
"fmt"
"strings"
"golang.org/x/net/html"
)
// IsConvertibleFormat reports whether a format group uses standard CFIs
// as its structural locator currency (i.e. whether CFI verification and
// cssSelector derivation apply to it).
func IsConvertibleFormat(formatGroup string) bool {
return isConvertible(string(formatGroup))
}
func truncateRunes(s string, n int) string {
r := []rune(s)
if len(r) <= n {
return s
}
return string(r[:n])
}
// anchorBlock returns the nearest non-inline (block-level) ancestor of a
// resolved text/element node — the server-side equivalent of the
// readers' computed-style block walk.
func anchorBlock(node *html.Node) *html.Node {
if node == nil {
return nil
}
if node.Type == html.ElementNode && !isInlineFormatting(node) {
return node
}
return findBlockParent(node)
}
// blockContextText extracts the normalized text from (node, runeOff) to
// the end of the anchor block — the same excerpt rule the readers use for
// context_text, ≤100 chars.
func blockContextText(block, node *html.Node, runeOff int) string {
segments := collectInlineText(block)
var sb strings.Builder
started := false
for _, seg := range segments {
if !started && seg.node == node {
started = true
runes := []rune(string(seg.runes))
if runeOff < len(runes) {
sb.WriteString(string(runes[runeOff:]))
}
continue
}
if started {
sb.WriteString(string(seg.runes))
}
}
return truncateRunes(normalizeWhitespace(sb.String()), 100)
}
// contextMatches reports whether a server-extracted context and a client-
// submitted context describe the same anchor. Both are suffixes of the
// same block text when the anchors share a block, so containment in
// either direction verifies; empty or very short contexts never match.
func contextMatches(serverCtx, submitted string) bool {
s := truncateRunes(normalizeWhitespace(submitted), 100)
t := truncateRunes(normalizeWhitespace(serverCtx), 100)
if s == "" || t == "" {
return false
}
short, long := s, t
if len([]rune(short)) > len([]rune(long)) {
short, long = long, short
}
if len([]rune(short)) < 12 {
return false
}
return strings.Contains(long, short)
}
// cssSelectorFor mirrors the readers' selOf: a body-relative
// tag:nth-child(k) chain (k = 1-based position among element siblings).
func cssSelectorFor(block *html.Node) string {
var segs []string
n := block
for n != nil && n.Type == html.ElementNode && n.Data != "body" {
k := 1
sib := n.Parent.FirstChild
for sib != nil && sib != n {
if sib.Type == html.ElementNode {
k++
}
sib = sib.NextSibling
}
segs = append([]string{n.Data + ":nth-child(" + fmt.Sprintf("%d", k) + ")"}, segs...)
n = n.Parent
}
return "body>" + strings.Join(segs, ">")
}
// blockCharOffset computes the rune offset of (node, runeOff) within the
// concatenated text of its block — the client-side scroll target.
func blockCharOffset(block, node *html.Node, runeOff int) int {
segments := collectInlineText(block)
s := 0
for _, seg := range segments {
if seg.node == node {
return s + runeOff
}
s += len(seg.runes)
}
return s + runeOff
}
// ProgressAnchor is the full server-computed apply handle for a stored
// standard CFI: the anchor block's cssSelector, the character offset
// within that block's text, and the spine document's href.
type ProgressAnchor struct {
CSSSelector string
CharOffset int
Href string
HealedCFI string
Healed bool
HealedPct *float64
}
// VerifyProgressAnchor resolves a client-submitted standard CFI against
// the EPUB, cross-checks the submitted context text, and heals the anchor
// by text search on any mismatch.
func VerifyProgressAnchor(epubPath, epubcfi, contextText string, percentage float64) (finalCFI string, cssSelector string, anchorHref string, charOffset *int, healedPct *float64, healed bool, err error) {
finalCFI = epubcfi
anchorHref = ""
spineIndex, localSteps, err := parseEPUBCFI(epubcfi)
if err != nil {
cfi, sel, href, off, pct, healedFlag, herr := healFromContext(epubPath, contextText, percentage)
return cfi, sel, href, off, pct, healedFlag, herr
}
conv := cachedConverter(epubPath)
doc, docHref, err := conv.getContentDoc(spineIndex + 1)
if err != nil {
return healFromContext(epubPath, contextText, percentage)
}
node, runeOff, rerr := resolveCFIToNode(doc, localSteps)
if rerr != nil {
return healFromContext(epubPath, contextText, percentage)
}
anchorHref = docHref
block := anchorBlock(node)
serverCtx := blockContextText(block, node, runeOff)
if contextMatches(serverCtx, contextText) {
off := blockCharOffset(block, node, runeOff)
return finalCFI, cssSelectorFor(block), anchorHref, &off, nil, false, nil
}
// Mismatch: heal by text search.
hCFI, hPct, hSel, hHref, herr := healAnchorByText(epubPath, contextText, percentage, spineIndex)
if herr != nil {
return finalCFI, "", hHref, nil, nil, false, fmt.Errorf("context mismatch (server %q vs client %q) and heal failed: %w",
truncateRunes(serverCtx, 40), truncateRunes(contextText, 40), herr)
}
hOff := blockCharOffsetFor(epubPath, hCFI)
return hCFI, hSel, hHref, &hOff, &hPct, true, nil
}
func healFromContext(epubPath, contextText string, percentage float64) (string, string, string, *int, *float64, bool, error) {
cfi, healedPct, sel, href, err := healAnchorByText(epubPath, contextText, percentage, -1)
if err != nil {
return "", "", "", nil, nil, false, err
}
off := blockCharOffsetFor(epubPath, cfi)
return cfi, sel, href, &off, &healedPct, true, nil
}
func healAnchorByText(epubPath, contextText string, percentage float64, spineIndex int) (string, float64, string, string, error) {
if epubPath == "" {
return "", 0, "", "", fmt.Errorf("no epub available for text anchoring")
}
conv := cachedConverter(epubPath)
spine, err := conv.loadSpine()
if err != nil {
return "", 0, "", "", err
}
needle := truncateRunes(normalizeWhitespace(contextText), 40)
if len([]rune(needle)) < 12 {
return "", 0, "", "", fmt.Errorf("context too short to anchor")
}
type match struct {
spine int
node *html.Node
off int
}
var matches []match
totalChars := 0
charsBefore := make([]int, len(spine.items))
for i := range spine.items {
doc, _, derr := conv.getContentDoc(i + 1)
if derr != nil {
continue
}
body := findBody(doc)
if body == nil {
continue
}
charsBefore[i] = totalChars
totalChars += countTextChars(body)
if n, runeOff := findTextInNode(body, needle); n != nil {
matches = append(matches, match{spine: i, node: n, off: runeOff})
}
}
if len(matches) == 0 || totalChars <= 0 {
return "", 0, "", "", fmt.Errorf("context not found in book")
}
best := matches[0]
bestDist := -1.0
for _, m := range matches {
frac := (float64(charsBefore[m.spine]) + float64(countTextCharsBefore(m.node)+m.off)) / float64(totalChars)
d := frac - percentage
if d < 0 {
d = -d
}
if bestDist < 0 || d < bestDist {
best = m
bestDist = d
}
}
healedPct := (float64(charsBefore[best.spine]) + float64(countTextCharsBefore(best.node)+best.off)) / float64(totalChars)
cfi, err := buildCFI(best.spine, best.node, best.off)
if err != nil {
return "", 0, "", "", err
}
sel := ""
if block := anchorBlock(best.node); block != nil {
sel = cssSelectorFor(block)
}
return cfi, healedPct, sel, spine.items[best.spine].href, nil
}
func blockCharOffsetFor(epubPath, cfi string) int {
n, off, _, herr := cfiTextAtAnchorInternal(epubPath, cfi)
if herr != nil {
return 0
}
block := anchorBlock(n)
if block == nil {
return 0
}
return blockCharOffset(block, n, off)
}
// cfiTextAtAnchorInternal resolves a stored standard CFI to its anchor
// text node, rune offset, and containing document.
func cfiTextAtAnchorInternal(epubPath, cfi string) (*html.Node, int, *html.Node, error) {
spineIndex, localSteps, err := parseEPUBCFI(cfi)
if err != nil {
return nil, 0, nil, err
}
conv := cachedConverter(epubPath)
doc, _, err := conv.getContentDoc(spineIndex + 1)
if err != nil {
return nil, 0, nil, err
}
node, off, err := resolveCFIToNode(doc, localSteps)
return node, off, doc, err
}
// ProgressCSSSelector derives the anchor block's cssSelector from a stored
// standard CFI.
func ProgressCSSSelector(epubPath, epubcfi string) (string, error) {
spineIndex, localSteps, err := parseEPUBCFI(epubcfi)
if err != nil {
return "", err
}
conv := cachedConverter(epubPath)
doc, _, err := conv.getContentDoc(spineIndex + 1)
if err != nil {
return "", err
}
node, _, err := resolveCFIToNode(doc, localSteps)
if err != nil {
return "", err
}
block := anchorBlock(node)
if block == nil {
return "", fmt.Errorf("no block ancestor for anchor")
}
return cssSelectorFor(block), nil
}
+22
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@@ -0,0 +1,22 @@
package sync
import (
"os"
"testing"
)
func TestManualRealBookAnchor(t *testing.T) {
path := "/home/nymusicman/Code/bookhoard/uploads/Ebooks/George Orwell/1984 (1269)/1984 - George Orwell.epub"
if _, err := os.Stat(path); err != nil {
t.Skip("real book not present on this machine")
}
cfi := "epubcfi(/6/2!/4[x1984]/8[_idContainer003]/62/1:456)"
ctx := "was at war with one of these Powers it was generally at peace with the other"
finalCFI, sel, href, charOff, healedPct, healed, err := VerifyProgressAnchor(path, cfi, ctx, 0.0415)
if err != nil {
t.Fatalf("VerifyProgressAnchor error: %v", err)
}
t.Logf("final=%q\n healed=%v healedPct=%v\n selector=%q href=%q charOff=%v", finalCFI, healed, healedPct, sel, href, charOff)
sel2, err2 := ProgressCSSSelector(path, cfi)
t.Logf("ProgressCSSSelector: %q err=%v", sel2, err2)
}
+158
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@@ -0,0 +1,158 @@
package sync
import (
"testing"
)
// The fixture (writeTestEPUB in cfi_converter_test.go): 6 spine docs.
// doc2 = spine index 1 with two paragraphs:
// p1: "The family of Dashwood had long been settled in Sussex."
// p2: "Their estate was large, and their residence was at Norland Park."
// Hand-derived local paths (html→body /4, body→div /4, div→p /4|/6,
// p→text chunk /1):
const (
dashwoodCFI = "epubcfi(/6/4!/4/2/2/1:0)"
dashwoodText = "The family of Dashwood had long been settled in Sussex."
estateCFI = "epubcfi(/6/4!/4/2/4/1:0)"
estateText = "Their estate was large, and their residence was at Norland Park."
dashwoodSelect = "body>div:nth-child(1)>p:nth-child(1)"
estateSelect = "body>div:nth-child(1)>p:nth-child(2)"
)
func TestVerifyProgressAnchorAcceptsExact(t *testing.T) {
path := writeTestEPUB(t)
finalCFI, sel, _, charOff, healedPct, healed, err := VerifyProgressAnchor(path, dashwoodCFI, dashwoodText, 0.3)
_ = charOff
if err != nil {
t.Fatalf("verify error: %v", err)
}
if healed {
t.Errorf("exact anchor should not heal")
}
if healedPct != nil {
t.Errorf("exact anchor should not carry a healed percentage")
}
if finalCFI != dashwoodCFI {
t.Errorf("finalCFI = %q, want unchanged %q", finalCFI, dashwoodCFI)
}
if sel != dashwoodSelect {
t.Errorf("cssSelector = %q, want %q", sel, dashwoodSelect)
}
}
func TestVerifyProgressAnchorHealsMismatch(t *testing.T) {
path := writeTestEPUB(t)
// Anchored at p1 but the context is p2's text: the classic
// client-projection bug — the server must heal to the true location.
finalCFI, _, _, charOff, healedPct, healed, err := VerifyProgressAnchor(path, dashwoodCFI, estateText, 0.3)
_ = charOff
if err != nil {
t.Fatalf("verify error: %v", err)
}
if !healed {
t.Fatalf("expected healing, got none (cfi=%q)", finalCFI)
}
if finalCFI != estateCFI {
t.Errorf("healed CFI = %q, want %q", finalCFI, estateCFI)
}
if healedPct == nil || *healedPct <= 0 {
t.Errorf("healed percentage not recomputed: %v", healedPct)
}
// Healing must converge: re-verifying the healed anchor is a no-op.
finalCFI2, _, _, _, healedPct2, healed2, err := VerifyProgressAnchor(path, finalCFI, estateText, 0.3)
if err != nil {
t.Fatalf("re-verify error: %v", err)
}
if healed2 {
t.Errorf("healed anchor should be stable, got healed again to %q (pct %v)", finalCFI2, healedPct2)
}
if finalCFI2 != finalCFI {
t.Errorf("re-verify CFI = %q, want %q", finalCFI2, finalCFI)
}
}
func TestVerifyProgressAnchorHealsUnresolvable(t *testing.T) {
path := writeTestEPUB(t)
// Element index 99 is out of range in doc2 — the anchor cannot resolve.
bogus := "epubcfi(/6/4!/4/2/99/1:0)"
finalCFI, _, _, charOff, healedPct, healed, err := VerifyProgressAnchor(path, bogus, dashwoodText, 0.05)
_ = charOff
if err != nil {
t.Fatalf("verify error: %v", err)
}
if !healed {
t.Fatal("unresolvable anchor should heal from context")
}
if finalCFI != dashwoodCFI {
t.Errorf("healed CFI = %q, want the Dashwood anchor %q", finalCFI, dashwoodCFI)
}
if healedPct == nil {
t.Errorf("healed percentage not recomputed")
}
}
func TestVerifyProgressAnchorDumbClient(t *testing.T) {
path := writeTestEPUB(t)
// No CFI at all — a client that only knows percentage + context is
// fully supported: the server anchors structurally from the text.
finalCFI, sel, _, charOff, healedPct, healed, err := VerifyProgressAnchor(path, "", estateText, 0.3)
_ = charOff
if err != nil {
t.Fatalf("verify error: %v", err)
}
if !healed {
t.Fatal("context-only submission should count as anchored-by-heal")
}
if finalCFI != estateCFI {
t.Errorf("anchored CFI = %q, want %q", finalCFI, estateCFI)
}
if sel != estateSelect {
t.Errorf("cssSelector = %q, want %q", sel, estateSelect)
}
if healedPct == nil {
t.Errorf("percentage not recomputed for context-only anchor")
}
}
func TestContextMatches(t *testing.T) {
block := "The family of Dashwood had long been settled in Sussex."
cases := []struct {
name string
serverCtx string
submitted string
want bool
}{
{"exact", block, block, true},
{"suffix of block", block, "settled in Sussex.", true},
{"block is suffix", "settled in Sussex.", block, true},
{"mid-block substring", block, "Dashwood had long been", true},
{"different text", block, "completely unrelated words here", false},
{"too short", block, "the", false},
{"empty submitted", block, "", false},
{"empty server", "", "some long enough context text", false},
}
for _, tc := range cases {
if got := contextMatches(tc.serverCtx, tc.submitted); got != tc.want {
t.Errorf("contextMatches(%q, %q) = %v, want %v", tc.serverCtx, tc.submitted, got, tc.want)
}
}
}
func TestParseStandardCFIRange(t *testing.T) {
// Web progress CFIs are range CFIs; parse must resolve to the start arm.
spineIndex, localSteps, err := parseEPUBCFI("epubcfi(/6/4!/4/4:0,/4/4:53)")
if err != nil {
t.Fatalf("parse error: %v", err)
}
if spineIndex != 1 {
t.Errorf("spineIndex = %d, want 1", spineIndex)
}
if len(localSteps) != 4 {
t.Fatalf("steps = %d, want 4 (parent + start arm)", len(localSteps))
}
last := localSteps[len(localSteps)-1]
if last.Index != 4 || !last.HasOffset || last.Offset != 53 {
t.Errorf("start-arm step = %+v, want /4:0", last)
}
}
+43
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@@ -274,8 +274,18 @@ func EstimatedPages(totalCharacters int64) int {
type ProgressService struct {
db *database.Queries
connManager *ConnectionManager
mediaPaths MediaPathResolver
}
// MediaPathResolver resolves a media item's library-relative file path to
// an absolute path, so the progress service can verify submitted anchors
// against the book itself.
type MediaPathResolver interface {
ResolveMediaPath(ctx context.Context, libraryID pgtype.UUID, relativePath string) (string, error)
}
func (s *ProgressService) SetMediaPathResolver(r MediaPathResolver) { s.mediaPaths = r }
func NewProgressService(db *database.Queries, connManager *ConnectionManager) *ProgressService {
return &ProgressService{db: db, connManager: connManager}
}
@@ -435,6 +445,39 @@ func (s *ProgressService) SaveProgress(ctx context.Context, req SaveProgressRequ
}
}
// Canonical position authority: resolve the submitted CFI against the
// book itself, cross-check the submitted context text, and heal the
// anchor by text search on any mismatch. Clients submit what their
// renderer can reliably observe (percentage + visible text); the
// server owns the structural math and keeps buggy clients from
// poisoning stored positions.
if !isFixed && s.mediaPaths != nil && params.ContextText.Valid &&
isConvertible(string(formatGroup)) && formatGroup != "" {
if path, perr := s.mediaPaths.ResolveMediaPath(ctx, mediaItem.LibraryID, mediaItem.FilePath); perr == nil && path != "" {
submittedCFI := ""
if params.Epubcfi.Valid {
submittedCFI = params.Epubcfi.String
}
submittedPct := 0.0
if params.Percentage.Valid {
submittedPct = params.Percentage.Float64
}
if finalCFI, _, _, charOff, healedPct, healed, verr := VerifyProgressAnchor(path, submittedCFI, params.ContextText.String, submittedPct); verr != nil {
log.Printf("Bookhoard: progress anchor verify failed for %s: %v", req.MediaItemID.String(), verr)
} else {
if healed || (!params.Epubcfi.Valid && finalCFI != "") {
params.Epubcfi = pgtype.Text{String: finalCFI, Valid: true}
if healedPct != nil {
params.Percentage = pgtype.Float8{Float64: *healedPct, Valid: true}
}
if charOff != nil {
params.CharacterOffset = pgtype.Int8{Int64: int64(*charOff), Valid: true}
}
}
}
}
}
conflictDetected := false
if hasExisting && existing.LastSyncSource.Valid && existing.LastSyncSource.String != req.Source {
if existing.LastSyncTimestamp.Valid {