Unified language handling and introduced a tool route registrar so prefixed locales no longer double-redirect.

Date: 2026-01-11 15:30 Summary: Unified language handling and introduced a tool route registrar so prefixed locales no longer double-redirect.

[question]

访问 http://localhost:8787/ja/ 下点击 http://localhost:8787/ja/tools/website-headers 会被重定向到 http://localhost:8787/zh/ja/tools/website-headers 并出现 404。
http://localhost:8787/ja/tools/website-headers 页面显示为英文而非日语。
markdown to html 工具没有支持目前的 10 国语言切换功能。
是否可以将目前两个工具的语言控制合并，以便统一语言管理并便于后续扩展所有工具？
要求实现“工具路由注册器”，把现有工具改用统一注册方式。

[try to solve] Root cause: Accept-Language negotiation treated a path as non-explicit when the first segment was a supported language but not in SITE_LANGS. The middleware then prepended the negotiated language, producing paths like /zh/ja/... and 404s.

Fixes and refactor:

Explicit language prefix detection — Updated getExplicitLangFromPath in src/index.ts so it only checks isSupportedLang(seg) (no longer requires the segment to be in SITE_LANGS). Explicit URLs such as /ja/... are no longer wrongly redirected to /zh/ja/....
Render language from the path — When the path has a supported language prefix, tool routes render in that language even if it is not listed in SITE_LANGS.
Shared language helpers — Extracted negotiation/helpers into src/site/lang.ts (DEFAULT_LANGS, getEnabledLangs, getFallbackLang, getDefaultLang, parseAcceptLanguage, pickLang, getExplicitLangFromPath, withLangPrefix, getLangFromPath, stripLangPrefix, langAlternatesForPath).
Markdown tool language switcher — Updated src/pages/markdownToHtmlPage.ts so the language dropdown and alternate links use full supportedLangs (all 10 locales).
Tool route registrar — Added src/site/toolRegistrar.ts exporting registerToolPage(app, toolName, renderFn), which registers /tools/<name> and /:lang/tools/<name> with shared language logic. Migrated website-headers and markdown-to-html to this registrar.

Local verification:

npm run dev
# or
wrangler dev

http://localhost:8787/ja/tools/website-headers should render in Japanese when src/site/i18n/ja.ts has entries.
http://localhost:8787/tools/website-headers may redirect based on Accept-Language.
http://localhost:8787/tools/markdown-to-html should show all 10 languages in the header switcher.

Files touched: src/index.ts, src/site/lang.ts, src/site/toolRegistrar.ts, src/pages/markdownToHtmlPage.ts, and related note in dev-logs/2026-01-11-fix-lang-redirect.md.

[actions]

Updated: src/index.ts
Added: src/site/lang.ts
Added: src/site/toolRegistrar.ts
Updated: src/pages/markdownToHtmlPage.ts
Related: dev-logs/2026-01-11-fix-lang-redirect.md

Unified language handling and introduced a tool route registrar so prefixed locales no longer double-redirect. | Dev Logs