From 4410a692079920376fb7215c7cd4c7debd8c7a15 Mon Sep 17 00:00:00 2001
From: "Simen A. W. Olsen" <hello@simenandre.no>
Date: Fri, 29 May 2026 00:16:48 +0200
Subject: feat: flatten TOC and add kindlegen validation

---
 src/html.zig | 71 ++++++++++++++++++++++++++++++++----------------------------
 1 file changed, 38 insertions(+), 33 deletions(-)

(limited to 'src')

diff --git a/src/html.zig b/src/html.zig
index fe7f287..8ec8564 100644
--- a/src/html.zig
+++ b/src/html.zig
@@ -8,7 +8,8 @@
 //!   4. normalizes HTML named entities (e.g. `&mdash;`) to numeric references,
 //!      since XML predefines only `&amp; &lt; &gt; &quot; &apos;`,
 //!   5. removes invalid control characters,
-//!   6. extracts the in-page table of contents for use as the EPUB navigation,
+//!   6. extracts the in-page table of contents (flattened to one level, since
+//!      Amazon's kindlegen rejects nested nav TOCs) for the EPUB navigation,
 //!   7. removes the `#navigation` sidebar (it is `position: fixed`, so it bleeds
 //!      onto every page, and the version-switcher dropdown is dead in an EPUB),
 //!   8. self-closes void elements (`<meta>` -> `<meta/>`, etc.).
@@ -94,48 +95,52 @@ fn extractToc(allocator: std.mem.Allocator, html: []const u8) !?[]u8 {
     const m = std.mem.indexOf(u8, html, marker) orelse return null;
     const ul_open = findTagOpen(html, m, "ul") orelse return null;
     const ul_end = matchingClose(html, ul_open, "ul") orelse return null;
-    return try rewriteToc(allocator, html[ul_open..ul_end]);
+    return try flattenToc(allocator, html[ul_open..ul_end]);
 }
 
-/// Rewrite an extracted TOC list: `<ul>` → `<ol>` (EPUB nav requires ordered
-/// lists) and `href="#X"` → `href="index.xhtml#X"`. Caller owns the result.
-fn rewriteToc(allocator: std.mem.Allocator, list: []const u8) ![]u8 {
+/// Build a single-level `<ol>` from the (possibly nested) TOC region: collect
+/// every `<a>...</a>` link, rewrite `href="#X"` → `href="index.xhtml#X"`, and
+/// wrap each in its own `<li>`. The list is flattened on purpose — Amazon's
+/// kindlegen rejects nested navigation TOCs (error E24011), which is what breaks
+/// "Send to Kindle". Returns null if the region has no links. Caller owns it.
+fn flattenToc(allocator: std.mem.Allocator, region: []const u8) !?[]u8 {
     var out: std.Io.Writer.Allocating = .init(allocator);
     defer out.deinit();
+    try out.writer.writeAll("<ol>\n");
 
     var i: usize = 0;
-    while (i < list.len) {
-        const lt = std.mem.indexOfScalarPos(u8, list, i, '<') orelse {
-            try out.writer.writeAll(list[i..]);
-            break;
-        };
-        try out.writer.writeAll(list[i..lt]);
-        const gt = tagEnd(list, lt) orelse return error.MalformedToc;
-        const tag = list[lt .. gt + 1];
-        try writeTocTag(&out.writer, tag);
-        i = gt + 1;
+    var count: usize = 0;
+    while (std.mem.indexOfPos(u8, region, i, "<a")) |a_lt| {
+        // Confirm this is an <a> element start (delimiter after the name).
+        const after = a_lt + 2;
+        if (after >= region.len or (region[after] != ' ' and region[after] != '>' and
+            region[after] != '\t' and region[after] != '\n'))
+        {
+            i = after;
+            continue;
+        }
+        const close = std.mem.indexOfPos(u8, region, a_lt, "</a>") orelse break;
+        try out.writer.writeAll("<li>");
+        try writeAnchor(&out.writer, region[a_lt .. close + 4]);
+        try out.writer.writeAll("</li>\n");
+        i = close + 4;
+        count += 1;
     }
-    return out.toOwnedSlice();
-}
 
-fn writeTocTag(w: *std.Io.Writer, tag: []const u8) !void {
-    const closing = tag[1] == '/';
-    const name = tagName(tag);
+    try out.writer.writeAll("</ol>\n");
+    if (count == 0) return null;
+    return try out.toOwnedSlice();
+}
 
-    if (std.ascii.eqlIgnoreCase(name, "ul")) {
-        try w.writeAll(if (closing) "</ol" else "<ol");
-        try w.writeAll(tag[1 + @as(usize, if (closing) 1 else 0) + name.len ..]);
-        return;
+/// Write an `<a>...</a>`, rewriting a leading `href="#"` to target the content.
+fn writeAnchor(w: *std.Io.Writer, anchor: []const u8) !void {
+    if (std.mem.indexOf(u8, anchor, "href=\"#")) |p| {
+        try w.writeAll(anchor[0 .. p + 6]); // through the opening quote
+        try w.writeAll(content_href);
+        try w.writeAll(anchor[p + 6 ..]); // from '#' onward
+    } else {
+        try w.writeAll(anchor);
     }
-    if (!closing and std.ascii.eqlIgnoreCase(name, "a")) {
-        if (std.mem.indexOf(u8, tag, "href=\"#")) |p| {
-            try w.writeAll(tag[0 .. p + 6]); // through the opening quote
-            try w.writeAll(content_href);
-            try w.writeAll(tag[p + 6 ..]); // from '#' onward
-            return;
-        }
-    }
-    try w.writeAll(tag);
 }
 
 /// Remove the `<div id="navigation">…</div>` sidebar. If absent, returns an
-- 
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