-- allium: 1
-- bDS Static Site Generation
-- Scope: core (Wave 4)
-- Distilled from: src/main/engine/BlogGenerationEngine.ts,
--   PageRenderer.ts, GenerationWorkerPool, RoutePageGenerationService

use "./post.allium" as post
use "./template.allium" as template
use "./metadata.allium" as meta
use "./menu.allium" as menu
use "./translation.allium" as translation

surface GenerationControlSurface {
    facing _: GenerationOperator

    provides:
        GenerateSiteRequested(generation)
        ValidateSiteRequested(project)
        ApplyValidationRequested(project_id, sections)
}

surface GenerationRuntimeSurface {
    facing _: GenerationRuntime

    provides:
        PageRenderRequested(template, context)
        GenerateSiteCompleted(generation)
}

value GenerationSection {
    kind: core | single | category | tag | date
}

value GeneratedFile {
    relative_path: String
    content_hash: String
}

entity SiteGeneration {
    project_id: String
    base_url: String
    language: String                    -- main language
    blog_languages: Set<String>
    max_posts_per_page: Integer
    pico_theme: String?
    sections: Set<GenerationSection>

    -- Output tracking
    generated_files: GeneratedFile with project_id = this.project_id
}

surface GenerationStatusSurface {
    context generation: SiteGeneration

    exposes:
        generation.project_id
        generation.base_url
        generation.language
        generation.blog_languages
        generation.max_posts_per_page
        generation.pico_theme
        generation.sections
        generation.generated_files.count
}

invariant IncrementalByContentHash {
    -- Files are only written when content_hash changes
    -- generatedFileHashes table tracks (projectId, relativePath, contentHash)
    -- A file with unchanged hash is skipped on regeneration
}

invariant MultiLanguageRoutes {
    -- Main language: flat routes (/{yyyy}/{mm}/{dd}/{slug})
    -- Additional languages: prefixed (/{lang}/{yyyy}/{mm}/{dd}/{slug})
    -- Each language subtree gets its own feeds and archives
}

invariant CanonicalBaseUrlConfigured {
    for generation in SiteGenerations:
        generation.base_url != ""
}

invariant NamedPicoTheme {
    for generation in SiteGenerations where generation.pico_theme != null:
        generation.pico_theme != ""
}

invariant GeneratedFilesTracked {
    for generation in SiteGenerations:
        generation.generated_files.count >= 0
}

-- Core section: root pages, sitemap, RSS, Atom, calendar.json

rule GenerateCoreSectionPages {
    when: GenerateSiteRequested(generation)
    requires: core in generation.sections
    ensures: FileGenerated("index.html")
    ensures: FileGenerated("sitemap.xml")
        -- Multi-language sitemap with hreflang alternates
    ensures: FileGenerated("feed.xml")
        -- RSS 2.0 feed
    ensures: FileGenerated("atom.xml")
        -- Atom feed
    ensures: FileGenerated("calendar.json")
        -- Post dates for calendar widget
    for lang in generation.blog_languages - {generation.language}:
        ensures: FileGenerated(format("{lang}/index.html", lang: lang))
        ensures: FileGenerated(format("{lang}/feed.xml", lang: lang))
        ensures: FileGenerated(format("{lang}/atom.xml", lang: lang))
}

-- Single section: one HTML page per published post

rule GenerateSinglePostPages {
    when: GenerateSiteRequested(generation)
    requires: single in generation.sections
    for p in Posts where status = published:
        let url = post_canonical_url(p)
        ensures: FileGenerated(format("{url}/index.html", url: url))
        for lang in generation.blog_languages - {generation.language}:
            if p.translations.any(t => t.language.code = lang):
                ensures: FileGenerated(format("{lang}/{url}/index.html",
                    lang: lang, url: url))
}

-- Category section: paginated archive per category

rule GenerateCategoryPages {
    when: GenerateSiteRequested(generation)
    requires: category in generation.sections
    for cat in generation.categories:
        let page_count = ceil(posts_in_category(cat).count / generation.max_posts_per_page)
        ensures: FileGenerated(format("category/{cat}/index.html", cat: cat))
        for page in page_range(2, page_count):
            ensures: FileGenerated(format("category/{cat}/page/{page}/index.html",
                cat: cat, page: page))
}

-- Tag section: paginated archive per tag

rule GenerateTagPages {
    when: GenerateSiteRequested(generation)
    requires: tag in generation.sections
    for t in Tags where post_count > 0:
        ensures: FileGenerated(format("tag/{slug}/index.html", slug: slugify(t.name)))
}

-- Date section: year and month archives

rule GenerateDateArchivePages {
    when: GenerateSiteRequested(generation)
    requires: date in generation.sections
    for year in distinct_years(Posts):
        ensures: FileGenerated(format("{year}/index.html", year: year))
        for month in distinct_months(Posts, year):
            ensures: FileGenerated(format("{year}/{month}/index.html",
                year: year, month: month))
}

-- Template rendering context

rule RenderPage {
    when: PageRenderRequested(template, context)
    -- Template rendering with full context:
    --   posts, pagination, menus, tags, categories,
    --   project metadata, i18n translations, theme settings
    -- Macro expansion: [[slug param1=value1 ...]] in post content
    -- HTML rewriting for canonical post/media paths
    ensures: RenderedHtml(template, context, output)
}

-- Validation

rule ValidateSite {
    when: ValidateSiteRequested(project)
    -- Compares sitemap URLs to HTML files on disk
    -- Detects: missing pages, extra (stale) pages, sitemap/file mismatches
    ensures: ValidationReport(missing_pages, extra_pages, stale_pages)
}

rule ApplyValidation {
    when: ApplyValidationRequested(project_id, sections)
    -- Targeted re-rendering for affected sections only
    ensures: GenerateSiteRequested(plan_generation(project_id, sections))
}

-- Day-block grouping for archives
invariant ArchiveDayBlocks {
    -- Archive/list pages group posts by day
    -- Each day block has a date header and the posts for that day
}

-- ============================================================================
-- SEARCH INDEX: PAGEFIND
-- ============================================================================

-- Pagefind builds a client-side full-text search index from generated HTML.
-- Uses an embedded Pagefind library integration rather than a CLI subprocess.
-- Runs as the final step of the generation pipeline, after all HTML is written.

rule BuildSearchIndex {
    when: GenerateSiteCompleted(generation)
    -- Only runs if any pages were rendered or deleted in this generation pass.
    -- Separate index per language:
    --   Main language: source = {html}/, output = {html}/pagefind/
    --   Each additional language: source = {html}/{lang}/, output = {html}/{lang}/pagefind/
    -- Each index built with force_language set to that language code.
    for lang in {generation.language} + (generation.blog_languages - {generation.language}):
        ensures: PagefindIndexBuilt(lang)
}

invariant PagefindHtmlMarking {
    -- Single-post templates must include data-pagefind-body attribute
    -- on the <article> element to scope indexing to post content only.
    -- Pagefind ignores elements without this attribute.
}

invariant PagefindAssets {
    -- Generated output includes Pagefind UI assets per language:
    --   {prefix}/pagefind/pagefind-ui.css
    --   {prefix}/pagefind/pagefind-ui.js
    -- where prefix is "" for main language, "{lang}" for additional languages.
    -- Frontend templates reference these via language_prefix variable.
    -- Assets are bundled locally — no external CDN references.
}

config {
    pagefind_threshold: Integer = 0
    -- Minimum pages to trigger indexing (0 = always if any rendered/deleted)
}