zenith-tool 0.0.3

//! Pack format, embedded preset table, and the project/preset resolver.
//!
//! A library "pack" is a `.zen` file whose IDENTITY is declared by a single
//! `library` SELF-entry in its own `libraries` block. This module owns the pack
//! METADATA model ([`LibraryPack`], [`PackItem`], [`PackSource`], [`ItemKind`]),
//! the [`EMBEDDED_PACKS`] preset table, parsing a pack's identity/items
//! ([`parse_pack`]), and resolving project packs against embedded presets
//! ([`resolve_packs`]).

use std::path::{Path, PathBuf};

use zenith_core::{KdlAdapter, KdlSource, TokenType};

/// Embedded preset packs, as `(pack_id, pack_source)` pairs.
///
/// Each `pack_source` is the verbatim `.zen` text of a shipped preset library,
/// bundled into the binary via [`include_str!`] (mirroring how the default
/// fonts are bundled in `zenith-core`). The `pack_id` is the expected package
/// id and is used only for diagnostics/lookup convenience; the authoritative id
/// is parsed from the pack's own `library` self-entry.
pub const EMBEDDED_PACKS: &[(&str, &str)] = &[
    (
        "@zenith/flowchart",
        include_str!("../../assets/libraries/zenith-flowchart.zen"),
    ),
    (
        "@zenith/filters",
        include_str!("../../assets/libraries/zenith-filters.zen"),
    ),
    (
        "@zenith/masks",
        include_str!("../../assets/libraries/zenith-masks.zen"),
    ),
    (
        "@zenith/brand-kit",
        include_str!("../../assets/libraries/zenith-brand-kit.zen"),
    ),
];

/// Where a [`LibraryPack`] was loaded from.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum PackSource {
    /// A preset pack embedded in the binary.
    Preset,
    /// A project pack read from the given `.zen` file path.
    Project(PathBuf),
}

impl PackSource {
    /// A short, stable label for human/JSON output: `"preset"` or `"project"`.
    pub fn label(&self) -> &'static str {
        match self {
            PackSource::Preset => "preset",
            PackSource::Project(_) => "project",
        }
    }
}

/// What kind of thing a pack item is.
///
/// A pack exports COMPONENT items (materialized as an instance on a page),
/// TOKEN items (filter tokens, copied into the target's tokens block with their
/// color-token dependencies — no instance, no page required), and ACTION items
/// (addressed as `<pkg>#<action-id>`).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ItemKind {
    /// A component item, addressed `<pkg>#<component-id>`.
    Component,
    /// A filter-token item, addressed `<pkg>#<token-id>`.
    Token,
    /// An action item, addressed `<pkg>#<action-id>`.
    Action,
}

impl ItemKind {
    /// A short, stable label for human/JSON output: `"component"`, `"token"`, or `"action"`.
    pub fn label(&self) -> &'static str {
        match self {
            ItemKind::Component => "component",
            ItemKind::Token => "token",
            ItemKind::Action => "action",
        }
    }
}

/// A single exported item of a [`LibraryPack`]: its id plus its kind.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PackItem {
    /// The item id (a component id, a filter-token id, or an action id).
    pub id: String,
    /// Whether the item is a component, a filter token, or an action.
    pub kind: ItemKind,
}

/// A loaded library pack: its identity plus the items it provides.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct LibraryPack {
    /// The package id, parsed from the pack's `library` self-entry.
    pub id: String,
    /// The pack version, parsed from the pack's `library` self-entry.
    pub version: Option<String>,
    /// Where the pack came from.
    pub source: PackSource,
    /// The items the pack provides: component ids first (in source order),
    /// then exportable token ids (in source order), then action ids (in source
    /// order).
    pub items: Vec<PackItem>,
}

/// Whether a token type is an EXPORTABLE library item (addressable as
/// `<pkg>#<token-id>` and copied by `materialize_token`).
///
/// Effect tokens — `filter` and `mask` — are self-contained, applyable units
/// that other documents reference by id, so they are exported items. Color /
/// dimension / gradient / shadow tokens are dependencies pulled in transitively
/// when an exported token (or component) needs them, not standalone items.
pub(super) fn is_exportable_token(ty: &TokenType) -> bool {
    matches!(ty, TokenType::Filter | TokenType::Mask)
}

/// An error produced while parsing a pack.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PackError {
    /// Human-readable message describing the failure.
    pub message: String,
}

impl PackError {
    fn new(message: impl Into<String>) -> Self {
        Self {
            message: message.into(),
        }
    }
}

impl std::fmt::Display for PackError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.message)
    }
}

impl std::error::Error for PackError {}

/// Parse a `.zen` pack `source` into a [`LibraryPack`] tagged with `source_kind`.
///
/// Pack identity is derived from the document's `libraries` block: the library
/// entry whose `id` matches the document's `project` id is the SELF-entry; if no
/// entry matches the project id but there is exactly one library entry, that
/// sole entry is used. A pack with no identifying library self-entry is an error
/// (a pack MUST declare its identity).
///
/// Items are the document's component ids in source order, followed by its
/// FILTER token ids in source order. (Only filter tokens are exported items;
/// color/dimension tokens are dependencies, not items.)
///
/// # Errors
///
/// Returns [`PackError`] when the source fails to parse, or when no library
/// self-entry can be determined.
pub fn parse_pack(source: &str, source_kind: PackSource) -> Result<LibraryPack, PackError> {
    let doc = KdlAdapter
        .parse(source.as_bytes())
        .map_err(|e| PackError::new(format!("parse error: {}", e)))?;

    let project_id = doc.project.as_ref().map(|p| p.id.as_str());

    // Prefer the library entry whose id matches the project id; otherwise fall
    // back to the sole library entry when there is exactly one.
    let self_entry = project_id
        .and_then(|pid| doc.libraries.iter().find(|lib| lib.id == pid))
        .or(match doc.libraries.as_slice() {
            [only] => Some(only),
            _ => None,
        });

    let self_entry = self_entry.ok_or_else(|| {
        PackError::new(
            "pack has no identifying library self-entry (declare \
             `libraries { library id=\"…\" version=\"…\" }`)",
        )
    })?;

    // Component items first (source order), then filter-token items (source
    // order). A token is an exported item only when it is a filter token.
    let mut items: Vec<PackItem> = doc
        .components
        .iter()
        .map(|c| PackItem {
            id: c.id.clone(),
            kind: ItemKind::Component,
        })
        .collect();
    items.extend(
        doc.tokens
            .tokens
            .iter()
            .filter(|t| is_exportable_token(&t.token_type))
            .map(|t| PackItem {
                id: t.id.clone(),
                kind: ItemKind::Token,
            }),
    );
    items.extend(doc.actions.iter().map(|a| PackItem {
        id: a.id.clone(),
        kind: ItemKind::Action,
    }));

    Ok(LibraryPack {
        id: self_entry.id.clone(),
        version: self_entry.version.clone(),
        source: source_kind,
        items,
    })
}

/// Parse every entry in [`EMBEDDED_PACKS`] into a [`LibraryPack`].
///
/// An embedded pack that fails to parse is skipped (embedded content is shipped
/// and tested, so this should not happen in practice); the returned vector
/// contains only the packs that parsed successfully.
pub fn load_embedded_packs() -> Vec<LibraryPack> {
    EMBEDDED_PACKS
        .iter()
        .filter_map(|(_, src)| parse_pack(src, PackSource::Preset).ok())
        .collect()
}

/// Scan `project_dir/libraries/*.zen` and parse each file into a [`LibraryPack`].
///
/// A missing `libraries/` directory (or a `project_dir` without one) yields an
/// empty vector. Files that fail to read or parse are skipped — a note is
/// written to stderr — so one bad pack never aborts the whole listing.
pub fn load_project_packs(project_dir: &Path) -> Vec<LibraryPack> {
    let libraries_dir = project_dir.join("libraries");
    let entries = match std::fs::read_dir(&libraries_dir) {
        Ok(entries) => entries,
        // Missing directory (or any read error) → no project packs.
        Err(_) => return Vec::new(),
    };

    let mut packs = Vec::new();
    for entry in entries.flatten() {
        let path = entry.path();
        if path.extension().and_then(|e| e.to_str()) != Some("zen") {
            continue;
        }
        let source = match std::fs::read_to_string(&path) {
            Ok(s) => s,
            Err(e) => {
                eprintln!("note: skipping '{}': {}", path.display(), e);
                continue;
            }
        };
        match parse_pack(&source, PackSource::Project(path.clone())) {
            Ok(pack) => packs.push(pack),
            Err(e) => eprintln!("note: skipping '{}': {}", path.display(), e),
        }
    }
    packs
}

/// Resolve all available packs: project packs first, then embedded presets.
///
/// Project packs take precedence over embedded packs of the same id (a project
/// pack SHADOWS an embedded preset). Both are returned, each tagged with its
/// [`PackSource`], so callers that LIST can show every pack; callers that
/// MATERIALIZE should prefer the first pack for a given id. The result is sorted
/// by id for deterministic output (project before embedded on ties).
pub fn resolve_packs(project_dir: Option<&Path>) -> Vec<LibraryPack> {
    let mut packs = Vec::new();
    if let Some(dir) = project_dir {
        packs.extend(load_project_packs(dir));
    }
    packs.extend(load_embedded_packs());

    // Stable, deterministic order: by id, with project packs ahead of embedded
    // on ties (so the shadowing winner sorts first).
    packs.sort_by(|a, b| {
        a.id.cmp(&b.id)
            .then_with(|| source_rank(&a.source).cmp(&source_rank(&b.source)))
    });
    packs
}

/// Sort rank giving project packs precedence over embedded presets.
fn source_rank(source: &PackSource) -> u8 {
    match source {
        PackSource::Project(_) => 0,
        PackSource::Preset => 1,
    }
}