# SCHEMA — song source files

Source-file contract for the songs pipeline. Files in `mikkeli/ncmr-songs` must follow this contract to be picked up by the auto-publisher.

The schema lives entirely in the YAML frontmatter block at the top of each `.md` file. The body below the frontmatter is plain markdown, rendered to MediaWiki wikitext by Pandoc — no special body conventions are enforced beyond the standard markdown grammar.

## File layout

```markdown
---
title: pulse under latent semantic envelopes
album: Shirakaba Express Service
wiki:
  publish: true
release_date: 2026-06-09
---

# pulse under latent semantic envelopes

... body markdown ...
```

The renderer parses the frontmatter, validates required fields, then hands the body (with the first `# Heading` line removed) to Pandoc.

## Fields

### Required

#### `title` (string)

The MediaWiki page name that the bot writes or updates. MediaWiki capitalises the first letter automatically; lowercase input is fine.

Example: `title: pulse under latent semantic envelopes` → wiki page `Pulse under latent semantic envelopes` at URL `/wiki/Pulse_under_latent_semantic_envelopes`.

The body should contain a matching `# Title` first-line heading for human readability when viewing the source file directly (in an editor, on Gitea's blob view, etc.). The renderer strips this first-line heading during conversion — the wiki page already supplies its own title.

#### `album` (string)

The full album name. Drives `[[Category:<album name>]]` injection at the bottom of the rendered wiki page. MediaWiki auto-creates the category page when at least one page references it.

The pipeline **does not** create or update a dedicated album info/index page. Album landing pages are the wiki's category pages, which you write freeform yourself.

Example: `album: Shirakaba Express Service` → category tag `[[Category:Shirakaba Express Service]]`.

For files where no album applies (placeholders, songs without an assigned album), use a sensible literal like `(unassigned)` and accept that they'll get a `[[Category:(unassigned)]]` tag. The field is required to keep the schema's contract simple.

#### `wiki.publish` (boolean)

Publishing gate. `true` means the pipeline writes this file to the wiki. `false` means the file is ignored.

The `wiki` key is a mapping rather than a flat field so future toggles (`wiki.protected`, `wiki.summary_template`, etc.) can be added without restructuring. None are defined yet.

Files under `wip/` are also skipped, regardless of `wiki.publish`.

### Optional

#### `release_date` (ISO 8601 date)

The song's release date in `YYYY-MM-DD` format. Skipped if absent. Currently informational; may drive sort order on future auto-generated indexes.

#### `lrc` (string, relative path)

Pointer to a companion LRC file, relative to the `.md` file's location.

Example: in `ses/tunnels.md`, `lrc: tunnels.lrc` declares that `ses/tunnels.lrc` is the companion synced-lyrics file.

**Deferred for v1**: the field is permitted by the schema but the renderer doesn't yet read or embed LRC contents.

#### `siblings` (mapping of placeholder → relative path)

Placeholder-to-file mapping for inter-page wikilinks.

```yaml
siblings:
  PULSE_DEV: pulse_dev.md
```

In the body markdown, write `[[PULSE_DEV]]` for a wikilink that displays the target's title, or `[[PULSE_DEV|custom display]]` for an aliased display. Resolution uses the target file's `title:` frontmatter as the wiki page name.

**Deferred for v1**: the field is permitted by the schema but placeholders pass through untouched.

## Body

Plain markdown. The renderer applies a single transformation before handing the body to Pandoc: the first-line `# Heading`, if present, is stripped.

Do not embed wikitext-specific syntax (`{{Template}}`, raw `[[Wikilink]]` not declared via `siblings`, etc.) in the body. Use markdown idioms only; the renderer adds the metadata-derived bits (banner, categories, sibling resolution) around Pandoc's output.

## Renderer behaviour

For each `.md` with `wiki.publish: true` and not under `wip/`:

1. Parse and validate frontmatter.
2. Strip the leading `# Heading` from the body if present.
3. Replace `[[PLACEHOLDER]]` markers with safe tokens. *(Deferred v1; no-op until siblings are implemented.)*
4. Pipe the body through `pandoc -f markdown -t mediawiki`.
5. Re-substitute sibling tokens with resolved `[[Page|Display]]` wikilinks. *(Deferred v1.)*
6. Prepend the auto-generated banner: `{{Auto-generated|source=<source URL>|generated_at=<ISO timestamp>}}`.
7. Append the album category: `[[Category:<album>]]`.
8. Read the current wiki page content via the MediaWiki API; if identical to the generated output, skip the write (idempotency — keeps the wiki history clean).
9. Otherwise, write the page with an edit summary referencing the source commit.

## v1 scope

**Implemented:**
- Frontmatter parsing and validation for `title`, `album`, `wiki.publish`, `release_date`
- Markdown body → wikitext via Pandoc
- First-line h1 stripping
- Banner template injection (requires `Template:Auto-generated` to exist on the wiki — see the pipeline `README.md` for the one-off setup)
- Album category injection
- Idempotent writes (no-op skip)

**Deferred:**
- `lrc` field consumption
- `siblings` placeholder resolution
- Multi-page aggregation (no album index pages generated; each file → its own wiki page)
- Language-aware rendering (the body conveys what languages exist; the renderer doesn't introspect)

## Examples

### A released song

```yaml
---
title: pulse under latent semantic envelopes
album: Shirakaba Express Service
wiki:
  publish: true
release_date: 2026-06-09
---
```

### A dev sister file (not published)

```yaml
---
title: pulse under latent semantic envelopes — personal dev notes
album: Shirakaba Express Service
wiki:
  publish: false
---
```

### A placeholder file (no real song yet)

```yaml
---
title: (placeholder)
album: kairo
wiki:
  publish: false
---
```

### A WIP file (in `wip/`, schema still applies but the file is skipped regardless)

```yaml
---
title: 海淀
album: (unassigned)
wiki:
  publish: false
---
```

## Validation errors the renderer must produce

The pipeline fails fast and loud on the following:

- Missing or unparseable frontmatter block
- Missing required field (`title`, `album`, `wiki.publish`)
- `title` is empty or whitespace-only
- `wiki.publish` is not a boolean
- `release_date` (if present) does not parse as YYYY-MM-DD
- `siblings` (if present) references a file that doesn't exist
- Two source files declare the same `title` (page-name collision)

Validation runs before any wiki API calls. A failed validation aborts the run with a non-zero exit and leaves the wiki untouched.