thor/AGENTS.md

Thor — Odin Static Site Generator

Thor is a static site generator written in Odin, replacing Hugo for the sbrow.github.io blog. It lives at ./thor/ as a git subtree with its own flake.nix.

Architecture

thor.json          ← site config (title, base_url, author, params, sectionate)
content/           ← markdown and HTML content files
layouts/           ← Mustache templates + partials (including icons)
assets/            ← CSS (Tufte-based, no build step) and JS
public/            ← build output (generated)

Source files

File	Responsibility
main.odin	Entry point. Sets context.logger, calls init_site, walk_content, render_site
site.odin	Site struct (config + arena), init_site, load_site_config, site_merge, site_allocator, destroy_site
frontmatter.odin	JSON frontmatter parser ({ } delimited)
content.odin	Page struct, content walker, page loader, cmark integration, full markdown pipeline
footnotes.odin	Note definition stripping (pre-cmark) + sidenote/marginnote injection (post-cmark)
alerts.odin	GitHub alert post-processor (> [!CAUTION] → styled blockquote)
emoji.odin	Emoji shortcode expander (:shrug: → ¯\_(ツ)_/¯)
highlight.odin	Post-cmark Tree-sitter syntax highlighter; loads grammars/queries from Helix, caches loaded grammars, reports syntax errors with file/line
tree_sitter.odin	C FFI bindings for Tree-sitter (TSParser, TSQuery, TSQueryCursor, node traversal, dlopen/dlsym)
sectionate.odin	wrap_sections proc — splits HTML at <h2 into <section> wrappers
render.odin	Mustache template rendering, all page types, RSS, sitemap, robots.txt, load_partials recursive scan
feed.odin	RSS feed + sitemap XML generation
mustache/	Vendored odin-mustache library

Icon SVGs live as HTML partials in layouts/partials/icons/ (home, github, rss, chevron_up, star).

Data flow

thor.json → init_site → Site (config + Dynamic_Arena)
                            ↓
content/ → walk_content → []Page (with body_html from pipeline)
                            ↓
layouts/*.html → render_site (Mustache render_in_layout) → public/

Config system

Site has params: json.Value for arbitrary user-defined data from thor.json. Social links and other template-only data live under "params". sectionate: bool controls automatic <section> wrapping at <h2> boundaries.

{
  "title": "...",
  "base_url": "...",
  "author": "...",
  "sectionate": true,
  "params": {
    "social": [
      { "name": "github", "url": "...", "icon": "icons/github" }
    ]
  }
}

Templates access params via dotted keys: {{#params.social}}, {{>* icon}}.

Config precedence: CLI flags > thor.json values > hardcoded defaults.

Markdown pipeline (in content.odin load_page)

raw markdown
  → expand_emoji          (pre-cmark: :shortcode: → unicode)
  → strip_definitions     (pre-cmark: extract [^id]: definitions)
  → cmark markdown_to_html (Unsafe mode for HTML passthrough)
  → inject_sidenotes      (post-cmark: [^id] → <label><input><span> markup)
  → inject_alerts         (post-cmark: [!TYPE] blockquotes → styled alerts)
  → highlight_code        (post-cmark: tree-sitter per code block, with error reporting)
  → wrap_sections         (post-cmark: if site.sectionate, wraps content in <section> at <h2>)

.html content files skip cmark entirely — body is used as-is.

Syntax highlighting

Build-time highlighting via Tree-sitter C FFI. No client-side JavaScript.

• Grammars loaded via dlopen from Helix's compiled .so files
• Highlight queries (.scm) loaded from Helix's runtime directory
• Paths hardcoded in tree_sitter.odin (Nix store paths, Helix-version-dependent)
• Capture names mapped to CSS classes: keyword → .hl-keyword, constant.numeric.integer → .hl-constant-numeric-integer, etc.
• Atom-one-dark color theme in main.css
• Failed grammar loads are cached (no retries) and logged via log.warnf
• Syntax errors detected via ts_node_has_error, reported with file path and line number relative to code block

Memory management

• Site owns a mem.Dynamic_Arena
• init_site calls mem.dynamic_arena_init(&site.arena, alignment = 64) — the 64-byte alignment is required by Odin's map runtime (MAP_CACHE_LINE_SIZE)
• Config loading (flags + JSON) uses the arena allocator explicitly
• site_allocator(site) returns the arena allocator for callers
• destroy_site frees the arena
• main.odin sets context.logger = log.create_console_logger() — without this, all log.* calls are silently dropped
• Not yet wired: context.allocator is not set to the arena in main.odin, so rendering and content processing still use the heap allocator

Building

Local development

nix develop
# From blog root:
odin run ./thor -- -drafts
cp assets/css/main.css public/css/main.css
cp assets/js/main.js public/js/main.js
caddy run  # serves public/ on blog.localhost

No CSS build step — main.css is static Tufte-based CSS, no preprocessor or compiler needed.

Production build

nix build  # runs thor + copies CSS/JS, outputs to ./result/

Tests

cd thor
odin test .           # site + mustache smoke tests
odin test mustache    # mustache spec + targeted tests (37 total)

Vendored mustache patches

Four modifications to mustache/mustache.odin:

1. any unwrapping in map_get and data_type — when values come from map[string]any, the inner any wrapper is unwrapped so type detection works correctly for nested maps and lists.

2. Layout partials — layout_template.partials = tmpl.partials added so partials ({{> nav}}, {{> footer}}) work inside the base layout template.

3. Inline partial rendering — replaced template_insert_partial (which injected tokens into the main token list, breaking section iteration) with template_render_partial (which lexes the partial, temporarily swaps tmpl.lexer, and recursively processes via template_process_tokens). Fixes partials inside sections. Standalone indentation applied to partial source before lexing.

4. Dynamic Names — {{>*key}} support. When a partial token value starts with *, the remaining key is resolved from the data context stack, and the resolved string is used as the partial name. Enables per-item partial selection inside sections (e.g., {{>* icon}} resolves icon from each social link).

Extracted template_process_tokens from template_eat_tokens to separate ROOT initialization + skip pass from the core token loop, allowing partials to reuse the loop.

Known limitations

• cmark allocates via C malloc, not the arena. HTML output leaks until process exit.
• CSS/JS cache busting uses manual ?v=N query params instead of content hashing.
• The shrug emoji has a backslash that may not display correctly.
• json.Value params require 64-byte aligned arena (workaround for dynamic_arena_allocator_proc ignoring per-allocation alignment).
• Tree-sitter grammar/query paths hardcoded in tree_sitter.odin (Nix store hashes, Helix-version-dependent).
• TSQueryCapture needs explicit _padding: u32 field for C ABI compatibility (40-byte sizeof).
• {{&content}} in layout template must have no leading whitespace — template_insert_content_into_layout indents all lines by preceding whitespace, which corrupts <pre> blocks.
• highlight.js removed; syntax highlighting is build-time only (no fallback if Tree-sitter fails).

Design decisions

See HUGO.md for analysis of why thor doesn't need Hugo's shortcode context isolation.

TODO

See TODOS.md for the full list.