# Localization Pages are served in the visitor's language based on a `?lang=` query parameter or the `Accept-Language` header. - **Phase 1 (implemented):** negotiation, URL scheme, caching, rendering plumbing. Translations are consumed through a stub interface; the database still holds only the original language. - **Phase 2 (final plan):** gettext-style fragment storage in the database — machine-translated chunks plus user override patches, assembled at render time. Storage details in `docs/migrate.md`. ## Phase 1: negotiation and URLs ### Language selection Deliberately simple — **q-values are ignored**: - All known `Accept-Language` implementations send the header **in order of preference**, so we parse it as an ordered list and never reorder. - Selection rule (`select_language` in `pagerite/i18n.py`): 1. If `?lang=` is present, use it (if a translation exists; otherwise fall through to header logic). 2. If the article's original language appears anywhere in the header list, use the **original**. Rationale: an AI translation is strictly worse than the original for anyone who has that language configured at all (e.g. `fi-FI, fi, en-US, en` gets English, not machine-translated Finnish). 3. Otherwise walk the header list in order and use the first language for which a translation exists. 4. Fall back to the original. Region tags normalize to their base subtag (`fi-FI` → `fi`). ### URLs: pretty for users, indexable for search engines - Canonical URLs stay pretty (`/some-page`). Each language version is addressable as `/some-page?lang=fi` so search engines can index them. - `` points to the page **itself including the query** (each language version is its own canonical). - `` entries point to every other language version (with `?lang=`), plus `x-default` for the plain URL. - On page load, pagerite.js removes the `?lang=` query via `history.replaceState` (restoring the pretty URL) but remembers the language in a JS variable. All fetch-navigation and preloads it performs afterwards send that language in the `Accept-Language` header, so the chosen language sticks for the session of clicks. - A full page refresh or a shared link resets to automatic selection (header only). This gives a clean one-time override without cookies. ### Response correctness - Content responses carry `Vary: accept-language` (added to the existing `accept-encoding` vary). - `_cached_body` and the page ETag include the **selected language** (not the raw header, which would blow up the cache key space). - `` reflects the served language. ### Rendering - The translated Markdown goes through the same `markdown.render` pipeline. - Navigation/sidebar titles come from the translation's title map, with per-node fallback to the original title (a partially translated tree must still render). - Fixed UI strings ("Not Found" etc.) and the editor UI stay English for now. - The markdown typographer (SmartyPants) is English-centric; per-language typographer options are a possible follow-up, not blocking. ## Phase 2: fragment-based translation storage (draft) Phase 1 assumed whole-page translated Markdown delivered from outside. The refined model is gettext-style: an article has **one primary version** (its `content`, in its own language) plus, per target language, **machine fragments** (translated chunks of Markdown) and **user patches** (minimal editor overrides). Both are stored in the database and assembled into the served Markdown at render time. ### The scenario this must handle 1. Article written in English. 2. Machine-translated into Spanish → fragments stored. 3. Editor fixes one Spanish paragraph and changes a link elsewhere to point at a Spanish resource → user patch hunks stored. 4. English article edited → the edited chunk's key changes; its Spanish fragment no longer matches. 5. Page requested before the machine translation refreshes → served as a **hybrid**: old fragments for unchanged chunks, plain English for the edited chunk. User patches are attempted against this hybrid, best effort, each hunk independently: the text fix is stale (its search text no longer exists) and silently skipped; the link change still applies even though the link sits in the now-English paragraph. 6. Machine translation refreshes → full Spanish again, with both patch hunks applying. ### Chunks `chunk_markdown(markdown)` splits the source into block-level chunks — blank-line-separated blocks: headings, paragraphs, code fences (kept whole), list blocks, tables, HTML blocks. A chunk's identity is its **source text**, gettext-msgid style: ```python chunk_key = blake3(normalize(chunk_text), digest_size=16).hex() ``` (`normalize`: strip trailing whitespace per line, collapse surrounding blank lines — so whitespace-only source edits don't invalidate translations.) Consequences: - Editing the English source invalidates exactly the edited chunks; all other fragments keep applying. Stale fragments are simply never referenced again and can be garbage-collected lazily (or left; they are tiny). - No explicit "source version" bookkeeping is needed — staleness falls out of the keys. ### User patches Editors always edit **full Markdown** in the existing editor UX — never fragments. When editing a translated view (`?lang=es`), the editor is loaded with the *current hybrid Markdown*; on save, the server computes a minimal diff against that hybrid and stores it as a patch: ```python class Patch(msgspec.Struct, omit_defaults=True): """One editing session's overrides, applied independently per hunk.""" hunks: list[tuple[str, str]] = [] # (search, replace) on hybrid Markdown ``` Hunks are produced from `difflib.SequenceMatcher` on the hybrid vs. the edited text at block granularity: each `replace`/`delete`/`insert` opcode becomes one `(search, replace)` pair, with the preceding block's tail as left context for `insert` (pure inserts have empty search context otherwise). Application is dead simple: ```python def apply_patch(hybrid: str, patch: Patch) -> str: for search, replace in patch.hunks: if search and search in hybrid: hybrid = hybrid.replace(search, replace, 1) # missing search text = stale hunk -> silently skipped return hybrid ``` Per-hunk independence is the robustness property from the scenario: a stale text fix does not block a still-valid link change. Patches are stored as an ordered list and applied in order. ### Storage Full storage design and the `migrate_v3` restructuring live in `docs/migrate.md`. The short version, as it concerns this document: - Originals **and** translations are content-addressed text chunks in flat stores: `Data.chunks: dict[hash, str]` and `Data.trans: dict[f"{chunk_hash}:{lang}", str]` — path-independent, so repeated paragraphs and menu titles are translated once and article moves touch nothing. `Node.chunks: list[hash]` gives each article its order. - `Node` gains **`language: str = ""`**, inherited down the tree like `banner` (empty = nearest ancestor, front page last, site default `en` final). `select_language` and `` use the resolved value instead of the global `ORIGINAL_LANGUAGE` constant. - **Known weakness:** changing a page's (or subtree's) `language` after translations exist mis-keys everything — translations are keyed by *source* chunks, so old entries silently stop matching and user patches (searching for old-hybrid text) mostly go stale. That is acceptable: the orphaned data is harmless and translations regenerate. We do not migrate translations across a language change. - Article paths are stored and keyed **without leading slashes** (`"docs/setup"`, front page `""`); slashes are added only in hrefs. ### Render pipeline (replaces the phase-1 `get_translation` stub) ```python def get_translation(path, lang, data) -> Translation | None: if lang not in node.langs: return None hybrid = "\n\n".join( chunks[h] if h in node.no_trans else trans.get(f"{h}:{lang}", chunks[h]) for h in node.chunks ) for patch in data.patches.get(f"{path}:{lang}", []): hybrid = apply_patch(hybrid, patch) return Translation(markdown=hybrid, titles=title_map(data, lang)) ``` - Availability is an article-level index: `node.langs: dict[lang, True]`, maintained by the translation writers (translator job, patch saves) in the same transaction as their data writes — rendering, language selection and hreflang never probe the `trans` store chunk by chunk. A stale key is benign (the "translation" just renders as the original). - `titles` for nav/sidebar/cards: each node's translated title is `trans.get(f"{hash(node.title)}:{lang}")` with per-node fallback — one dict lookup per nav item at render time. - Cache invalidation: writes to `chunks` / `trans` / `patches` (translator, editor saves) call `_invalidate_pages()`, same as content writes. ### Editor flow - `GET` of page Markdown for editing with a `lang` parameter returns the hybrid (not the raw original) when the article has that language. - `PUT`/WS save with `lang` does **not** touch `node.chunks`; it diffs against the hybrid that was served and appends a `Patch`. (Serve a hybrid generation token with the editor payload so a save based on a stale hybrid can be rebased or rejected — simplest: recompute the diff against the *current* hybrid and accept best-effort, matching the patch philosophy.) - Saving the primary-language version re-chunks the submitted Markdown and updates `Data.chunks` / `node.chunks` — only genuinely new text lands in the kanta change diff (see docs/migrate.md). ### Explicitly out of scope for phase 2 - The machine translation itself: chunking output goes in, translated chunks come back. A background job writes `trans` entries; this doc only defines the storage key (`chunk_hash:lang`) and the merge semantics. - Garbage collection of orphaned chunks/translations (see docs/migrate.md). - sitemap.xml per-language entries; translated UI chrome; per-language typographer options; multi-locale date/number formatting.