refactor: merge workspace (core/ + ui/) into a single flat binary crate

integrate CLI into main.rs, no lib.rs by design (YAGNI)

src/document/loader.rs

@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// src/document/loader.rs
+//
+// Document loading: format detection, format dispatch, and directory scanning.
+
+use crate::document::model::{PortableModel, RasterModel, VectorModel};
+use crate::document::session::data::{SessionData, SessionItem};
+use crate::document::types::PageLayout;
+use crate::document::DocumentContent;
+use crate::error::{Error, Result};
+use std::path::Path;
+
+/// The three document formats Noctua understands.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum DocumentFormat {
+    /// Raster images – anything the image crate can decode.
+    Raster,
+    /// Vector graphics (SVG).
+    Vector,
+    /// Portable documents (PDF).
+    Portable,
+}
+
+/// Detects the document format from the file extension.
+///
+/// Returns `None` for unknown extensions so directory scans can skip
+/// unsupported files early. At load time the underlying library
+/// (`ImageReader`, `usvg`, `pdfium`) is the final authority.
+fn detect_format(path: &Path) -> Option<DocumentFormat> {
+    match path
+        .extension()
+        .and_then(|e| e.to_str())
+        .map(str::to_lowercase)
+        .as_deref()
+    {
+        Some("pdf") => Some(DocumentFormat::Portable),
+        Some("svg") => Some(DocumentFormat::Vector),
+        Some("png" | "jpg" | "jpeg" | "webp" | "gif" | "bmp" | "tiff" | "tif") => {
+            Some(DocumentFormat::Raster)
+        }
+        _ => None,
+    }
+}
+
+/// Loads a document from a path and returns its content.
+///
+/// # Errors
+///
+/// Returns [`Error::NotFound`] if the path does not exist.
+/// Returns [`Error::Unsupported`] if the file extension is not recognised.
+pub(crate) fn load_document(path: &Path) -> Result<DocumentContent> {
+    if !path.exists() {
+        return Err(Error::NotFound(format!("{}", path.display())));
+    }
+
+    match detect_format(path) {
+        Some(DocumentFormat::Portable) => {
+            // TODO: Replace with actual pdfium-render loading.
+            Ok(DocumentContent::Portable(PortableModel {
+                path: path.to_path_buf(),
+                page_count: 3,
+                layout: PageLayout::new(vec![(595.0, 842.0); 3], 10.0),
+            }))
+        }
+        Some(DocumentFormat::Vector) => {
+            // TODO: Replace with actual usvg parsing.
+            Ok(DocumentContent::Vector(VectorModel {
+                path: path.to_path_buf(),
+                view_box: None,
+            }))
+        }
+        Some(DocumentFormat::Raster) => {
+            // TODO: Replace with actual image-crate loading.
+            Ok(DocumentContent::Raster(RasterModel {
+                path: path.to_path_buf(),
+                dimensions: (1920, 1080),
+            }))
+        }
+        None => Err(Error::Unsupported(format!(
+            "extension: {}",
+            path.extension()
+                .and_then(|e| e.to_str())
+                .unwrap_or("(none)")
+        ))),
+    }
+}
+
+/// Scans a directory for supported files and populates the session.
+pub(crate) fn scan_directory_into(session: &mut SessionData, dir: &Path) {
+    if let Ok(entries) = std::fs::read_dir(dir) {
+        let mut paths: Vec<_> = entries
+            .filter_map(std::result::Result::ok)
+            .map(|e| e.path())
+            .filter(|p| p.is_file() && detect_format(p).is_some())
+            .collect();
+
+        paths.sort();
+
+        session.items = paths.into_iter().map(|p| SessionItem::new(p, 0)).collect();
+    }
+}