indicatrix-cut 0.7.1

//! Discovers which files a import request should read: walking a folder for
//! `.asc`, `.gem`, `.gcs` and stand-alone `.indicatrix` candidates (with an optional,
//! guarded recursive descent) and finding the file that sits beside a design: its
//! `.indicatrix` design file, or the older sidecar of a `.asc`.

use super::foreign::ForeignFormat;
use indicatrix_formats::native::design::{DESIGN_EXTENSION, FileKind, detect_kind, is_design_path};
use std::{
    collections::HashSet,
    path::{Path, PathBuf},
};
use tracing::warn;

/// Backstop against a pathological filesystem when [`super::wiring::setup_import_callback`]'s
/// optional subfolder recursion is enabled -- a symlink/junction loop is already caught by
/// [`collect_design_files_recursive`]'s `visited` set regardless of depth, so this only
/// guards an absurdly deep (but non-cyclic) real tree.
pub(super) const MAX_RECURSE_DEPTH: usize = 32;

/// The file kinds a `.indicatrix` design file attaches to when one sits beside it (same
/// folder and stem), in the order the library reads them: `.asc` first, then `.gem`,
/// then `.gcs`. Both letter cases are tried so the match also works on a
/// case-sensitive file system.
const SCHEDULE_EXTENSIONS: [&str; 6] = ["asc", "ASC", "gem", "GEM", "gcs", "GCS"];

/// The `.asc`/`.gem`/`.gcs` file beside the design file at `design_path` (same folder
/// and stem), if one exists. A design file with such a sibling is imported attached to
/// it, not as a design of its own.
#[must_use]
fn schedule_sibling(design_path: &Path) -> Option<PathBuf> {
    SCHEDULE_EXTENSIONS
        .iter()
        .map(|extension| design_path.with_extension(extension))
        .find(|candidate| candidate.is_file())
}

/// `true` for a file Import reads as a design of its own: `.asc` cutting instructions, a
/// `GemCAD` `.gem` save file, a Gem Cut Studio `.gcs` file (extension compared
/// case-insensitively), or a stand-alone `.indicatrix` design file. The `.gem`/`.gcs`
/// are converted to `.asc` on import -- see [`super::foreign`]. A `.indicatrix` file
/// with one of those beside it is not stand-alone: it is attached to that design
/// ([`find_design_file_beside`]) and so is not a candidate itself.
#[must_use]
fn is_importable_design(path: &Path) -> bool {
    if is_design_path(path) {
        return schedule_sibling(path).is_none();
    }
    path.extension()
        .is_some_and(|e| e.eq_ignore_ascii_case("asc"))
        || ForeignFormat::from_path(path).is_some()
}

/// Walks one directory for importable design files ([`is_importable_design`]),
/// descending into subdirectories when `recurse` is true. `visited` records the
/// canonicalized (symlink-resolved) path of every directory already entered this
/// call tree -- a symlink or junction looping back to an ancestor canonicalizes to
/// a path already in that set, so the second visit is skipped rather than
/// recursing forever (comparing raw paths wouldn't catch this, since a symlink's
/// own path text never repeats even though its target does). `depth` is capped at
/// [`MAX_RECURSE_DEPTH`] as a second, independent backstop. Both guards fail open
/// (skip and log via `warn!`) -- one bad subfolder shouldn't stop design files
/// elsewhere in the tree from being found.
pub(super) fn collect_design_files_recursive(
    dir: &Path,
    recurse: bool,
    depth: usize,
    max_depth: usize,
    visited: &mut HashSet<PathBuf>,
    out: &mut Vec<PathBuf>,
) {
    if depth > max_depth {
        warn!(
            "Import: not descending into '{}' -- exceeded max recursion depth ({max_depth})",
            dir.display()
        );
        return;
    }
    let canon = std::fs::canonicalize(dir).unwrap_or_else(|_| dir.to_path_buf());
    if !visited.insert(canon) {
        warn!(
            "Import: skipping '{}' -- already visited (symlink loop?)",
            dir.display()
        );
        return;
    }

    let Ok(entries) = std::fs::read_dir(dir) else {
        return;
    };
    for entry in entries.flatten() {
        let p = entry.path();
        if p.is_file() && is_importable_design(&p) {
            out.push(p);
        } else if recurse && p.is_dir() {
            collect_design_files_recursive(&p, recurse, depth + 1, max_depth, visited, out);
        }
    }
}

/// Resolves what [`super::pipeline::import_path`] should actually import: the single
/// file `path` names, or every `.asc`/`.gem`/`.gcs`/stand-alone `.indicatrix` file
/// directly inside it (plus, when `recurse`, its subfolders; see
/// [`collect_design_files_recursive`] for the symlink-loop/depth guards).
///
/// A directly picked `.indicatrix` file with a `.asc`/`.gem`/`.gcs` beside it stands
/// for that design (the `.indicatrix` is attached to it); without one it is imported
/// as a design of its own.
///
/// `Err` carries the user-facing message `import_path` returns verbatim -- an
/// unreadable folder, a path that is neither file nor folder, a directly picked
/// older sidecar, or a folder with no design file in it. Split out purely so
/// `import_path` stays under clippy's `too_many_lines` limit.
pub(super) fn collect_import_candidates(
    path: &Path,
    recurse: bool,
) -> Result<Vec<PathBuf>, String> {
    let mut candidates: Vec<PathBuf> = Vec::new();
    if path.is_dir() {
        match std::fs::read_dir(path) {
            Ok(entries) => {
                // The top-level folder the user picked isn't itself loop-guarded (it
                // can't be reached via a symlink pointing back to itself before this
                // point) -- only directories walked below it are, via `visited`.
                let mut visited: HashSet<PathBuf> = HashSet::new();
                for entry in entries.flatten() {
                    let p = entry.path();
                    if p.is_file() && is_importable_design(&p) {
                        candidates.push(p);
                    } else if recurse && p.is_dir() {
                        collect_design_files_recursive(
                            &p,
                            recurse,
                            1,
                            MAX_RECURSE_DEPTH,
                            &mut visited,
                            &mut candidates,
                        );
                    }
                }
            }
            Err(e) => return Err(format!("Could not read folder '{}': {e}", path.display())),
        }
    } else if path.is_file() {
        // A directly picked older Indicatrix sidecar (current
        // `.indicatrix.toml` or legacy `.gemcut.toml`) is not a design file this
        // import path can do anything useful with -- reaching `local::import_asc`
        // with it would come back as an opaque "parse error", with nothing pointing
        // the cutter at the button that actually opens this kind of file. Detected
        // via `indicatrix_cut_core::native::asc_path_for_native`'s own suffix check
        // (a naming guess, not a parse -- see that function's own doc comment)
        // since no file has been read yet at this point.
        if indicatrix_cut_core::native::asc_path_for_native(path).is_some() {
            return Err(format!(
                "'{}' is an older Indicatrix sidecar, not a .asc -- open it with \"Open\" \
                 in the Edit tab instead of Import, or import the .asc beside it.",
                path.display()
            ));
        }
        if is_design_path(path) {
            candidates.push(schedule_sibling(path).unwrap_or_else(|| path.to_path_buf()));
        } else {
            candidates.push(path.to_path_buf());
        }
    } else {
        return Err(format!("'{}' is not a file or folder.", path.display()));
    }

    if candidates.is_empty() {
        return Err(format!(
            "No .asc, .gem, .gcs or .indicatrix files found at '{}'.",
            path.display()
        ));
    }
    Ok(candidates)
}

/// Reads `path` as a file to attach: its bare name and bytes.
fn read_attachment(path: &Path) -> Option<(String, Vec<u8>)> {
    let bytes = std::fs::read(path).ok()?;
    let name = path.file_name()?.to_string_lossy().into_owned();
    Some((name, bytes))
}

/// Looks for the self-contained `<stem>.indicatrix` design file sitting beside `path`
/// (a `.asc`, `.gem` or `.gcs`) and reads it when it is one. `None` when there is no
/// such file, or the file of that name is not a design file (an older sidecar that
/// was renamed, say) -- attaching something the editor cannot open as a design would
/// only hide the `.asc` behind it.
///
/// The editor prefers this file over the schedule it is attached to: it carries the
/// whole design, including everything the `.asc` has no field for.
pub(super) fn find_design_file_beside(path: &Path) -> Option<(String, Vec<u8>)> {
    let candidate = path.with_extension(DESIGN_EXTENSION);
    let (name, bytes) = read_attachment(&candidate)?;
    (detect_kind(&bytes) == FileKind::Design).then_some((name, bytes))
}

/// Looks for the design file or older sidecar sitting beside `asc_path` that carries more than the bare
/// `.asc`: the self-contained `<stem>.indicatrix` design file first
/// ([`find_design_file_beside`]), then the older sidecar -- the current
/// `<stem>.indicatrix.toml` suffix, falling back to the legacy `<stem>.gemcut.toml`
/// suffix -- and reads its bytes. `None` when none of them is present, which is the
/// ordinary case for a bare `.asc` with no Indicatrix-authored history.
///
/// `Path::set_extension` is used the same way
/// `indicatrix_formats::native::path::native_path_for_asc` builds the current-suffix
/// path (a multi-segment extension like `"indicatrix.toml"` replaces everything
/// after the LAST dot in the file name, giving `stem.indicatrix.toml`, not
/// `stem.asc.indicatrix.toml`).
pub(super) fn find_native_sidecar(asc_path: &Path) -> Option<(String, Vec<u8>)> {
    if let Some(design) = find_design_file_beside(asc_path) {
        return Some(design);
    }
    let mut current = asc_path.to_path_buf();
    current.set_extension(indicatrix_cut_core::native::NATIVE_EXTENSION_SUFFIX);
    let mut legacy = asc_path.to_path_buf();
    legacy.set_extension(indicatrix_cut_core::native::LEGACY_NATIVE_EXTENSION_SUFFIX);

    [current, legacy]
        .into_iter()
        .find_map(|candidate| read_attachment(&candidate))
}