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bDS2/specs/preview.allium

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-- allium: 1
-- bDS Local Preview Server
-- Scope: core (Wave 4)
-- Distilled from: src/main/engine/PreviewServer.ts, PageRenderer.ts
use "./template.allium" as template
use "./generation.allium" as generation
entity PreviewServer {
host: String -- 127.0.0.1
port: Integer -- 4123
is_running: Boolean
}
config {
preview_host: String = "127.0.0.1"
preview_port: Integer = 4123
}
surface PreviewControlSurface {
facing _: PreviewOperator
provides:
StartPreviewRequested(project)
StopPreviewRequested(server)
}
surface PreviewHttpSurface {
facing _: PreviewClient
provides:
PreviewRequest(path)
PreviewDraftRequest(path, post_id)
}
rule StartPreview {
when: StartPreviewRequested(project)
ensures: PreviewServer.created(
host: config.preview_host,
port: config.preview_port,
is_running: true
)
}
rule StopPreview {
when: StopPreviewRequested(server)
-- Graceful shutdown with inflight request tracking
ensures: server.is_running = false
}
-- Route resolution
-- Preview renders all posts (published + draft) on-demand via Liquid templates.
-- Content priority: DB content (draft edits) over published .md file content.
-- See invariant PreviewDraftOverlay below.
rule ServePostPreview {
when: PreviewRequest(path)
requires: is_post_path(path)
-- path matches "/{yyyy}/{mm}/{dd}/{slug}"
-- Finds post by slug+date regardless of status (published or draft).
-- Content resolved via editor_body: DB content if present, else .md file.
-- Renders via Liquid template with full PageRenderer context.
ensures: PreviewResponse(rendered_html)
}
rule ServeDraftPreview {
when: PreviewDraftRequest(path, post_id)
-- Explicit draft preview by post_id (used by editor preview pane).
-- Renders draft content (from DB, not filesystem).
ensures: PreviewResponse(rendered_html)
}
rule ServeArchivePreview {
when: PreviewRequest(path)
requires: is_archive_path(path)
-- Category, tag, date archives with pagination
-- Includes both published and draft posts in listings.
ensures: PreviewResponse(rendered_html)
}
rule ServeMediaFile {
when: PreviewRequest(path)
requires: is_media_path(path)
-- Path-traversal protection: validates path stays within media directory
ensures: PreviewResponse(media_file)
}
rule ServeAssets {
when: PreviewRequest(path)
requires: is_asset_path(path)
ensures: PreviewResponse(asset_file)
}
rule ServeLanguagePrefixedRoute {
when: PreviewRequest(path)
requires: is_language_prefixed(path)
-- Detects language prefix from supported languages
-- Renders with translation overlay for that language
ensures: PreviewResponse(translated_html)
}
invariant PreviewDraftOverlay {
-- Preview is the draft workspace: it shows what the blog *will* look like,
-- not what it currently looks like on the published site.
--
-- Post universe: all posts with status in {published, draft}.
-- Archived posts are excluded.
--
-- Content priority (per post):
-- 1. DB content field (draft edits not yet published) → used when non-nil
-- 2. Published .md file (last-published snapshot) → used when DB content is nil
-- 3. Empty string → fallback if neither exists
--
-- This means:
-- - A purely draft post (never published) renders from DB content.
-- - A published-then-edited post renders from DB content (the draft edits).
-- - A published post with no pending edits renders from its .md file.
--
-- Contrast with generation (see generation.allium GenerationPublishedOnly):
-- Generation uses *only* published .md file content, never DB draft content,
-- and excludes posts that have never been published.
}
invariant ThemeSwitching {
-- Preview supports live theme/mode switching via query params
-- ?theme=amber&mode=dark etc.
-- Uses Pico CSS with configurable themes
}
invariant PreviewServerBinding {
for server in PreviewServers where server.is_running:
server.host = config.preview_host and server.port = config.preview_port
}
invariant LocalhostOnly {
-- Preview server binds to 127.0.0.1 only, never 0.0.0.0
}