-- allium: 1
-- bDS Tag System
-- Scope: core (Wave 1)
-- Distilled from: src/main/engine/TagEngine.ts, schema.ts

use "./project.allium" as project
use "./post.allium" as post

surface TagControlSurface {
    facing _: TagOperator

    provides:
        CreateTagRequested(project, name, color)
        UpdateTagRequested(tag, changes)
        DeleteTagRequested(tag)
        RenameTagRequested(tag, new_name)
        MergeTagsRequested(sources, target)
        SyncTagsFromPostsRequested(project)
}

entity Tag {
    project: project/Project
    name: String
    color: String?              -- hex color code
    post_template_slug: String?
    created_at: Timestamp
    updated_at: Timestamp

    -- Derived
    posts: post/Post with this.name in tags
    post_count: posts.count
}

surface TagSurface {
    context tag: Tag

    exposes:
        tag.project
        tag.name
        tag.color when tag.color != null
        tag.post_template_slug when tag.post_template_slug != null
        tag.created_at
        tag.updated_at
        tag.posts.count
        tag.post_count
}

invariant UniqueTagNamePerProject {
    -- Case-insensitive uniqueness
    for a in Tags:
        for b in Tags:
            (a != b and a.project = b.project)
                implies lowercase(a.name) != lowercase(b.name)
}

invariant TagsPersistToFilesystem {
    -- meta/tags.json is the portable format (no internal IDs)
    -- Must stay in sync with DB tag table
    parse_json(read_file("meta/tags.json")) = serialize_portable(Tags)
}

rule CreateTag {
    when: CreateTagRequested(project, name, color)
    let existing_tags = Tags where project = project
    requires: not existing_tags.any(t => lowercase(t.name) = lowercase(name))
        -- Case-insensitive duplicate check
    ensures: Tag.created(
        project: project,
        name: name,
        color: color
    )
    ensures: TagsFileWritten(project)
}

rule UpdateTag {
    when: UpdateTagRequested(tag, changes)
    ensures: TagFieldsUpdated(tag, changes)
    ensures: tag.updated_at = now
    ensures: TagsFileWritten(tag.project)
}

rule DeleteTag {
    when: DeleteTagRequested(tag)
    -- Runs as background task, removes tag from all posts
    for p in tag.posts:
        ensures: p.tags = p.tags - {tag.name}
    ensures: not exists tag
    ensures: TagsFileWritten(tag.project)
}

rule RenameTag {
    when: RenameTagRequested(tag, new_name)
    -- Runs as background task
    let old_name = tag.name
    for p in tag.posts:
        ensures: p.tags = (p.tags - {old_name}) + {new_name}
    ensures: tag.name = new_name
    ensures: TagsFileWritten(tag.project)
}

rule MergeTags {
    when: MergeTagsRequested(sources, target)
    -- Runs as background task
    -- Merges multiple source tags into a single target
    requires: sources.count >= 1
    for source in sources:
        for p in source.posts:
            ensures: p.tags = (p.tags - {source.name}) + {target.name}
        ensures: not exists source
    ensures: TagsFileWritten(target.project)
}

rule SyncTagsFromPosts {
    when: SyncTagsFromPostsRequested(project)
    -- Discovers tags used in posts that are not in the tags table
    for post in project.posts:
        for tag_name in post.tags:
            if not exists Tag{project: project, name: tag_name}:
                ensures: Tag.created(project: project, name: tag_name)
    ensures: TagsFileWritten(project)
}