// 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();
    }
}