// Copyright (c) 2022-2024 Sophie Herold
// Copyright (c) 2022-2023 Christopher Davis
// Copyright (c) 2023 Julian Hofer
// Copyright (c) 2023 Gage Berz
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
//
// SPDX-License-Identifier: GPL-3.0-or-later

use std::cell::{OnceCell, RefCell};

use anyhow::Context;
use gio::prelude::*;
use gio::subclass::prelude::*;
use glib::subclass::Signal;
use glib::GString;
use indexmap::IndexMap;
use once_cell::sync::Lazy;

use crate::deps::*;
use crate::util;
use crate::util::gettext::*;

mod imp {
    use super::*;

    #[derive(Debug, Default)]
    pub struct LpFileModel {
        /// Use and IndexMap such that we can put the elements into an arbitrary
        /// order while still having fast hash access via file URI.
        pub(super) files: RefCell<IndexMap<GString, gio::File>>,
        pub(super) directory: OnceCell<gio::File>,
        /// Track file changes.
        pub(super) monitor: OnceCell<gio::FileMonitor>,
    }

    #[glib::object_subclass]
    impl ObjectSubclass for LpFileModel {
        const NAME: &'static str = "LpFileModel";
        type Type = super::LpFileModel;
    }

    impl ObjectImpl for LpFileModel {
        fn signals() -> &'static [Signal] {
            static SIGNALS: Lazy<Vec<Signal>> =
                Lazy::new(|| vec![Signal::builder("changed").build()]);
            SIGNALS.as_ref()
        }
    }
}

glib::wrapper! {
    pub struct LpFileModel(ObjectSubclass<imp::LpFileModel>);
}

impl Default for LpFileModel {
    fn default() -> Self {
        glib::Object::new()
    }
}

impl LpFileModel {
    /// Create with a single element
    pub fn from_file(file: gio::File) -> Self {
        Self::from_files(vec![file])
    }

    pub fn from_files(files: Vec<gio::File>) -> Self {
        let model = Self::default();

        {
            let mut vec = model.imp().files.borrow_mut();
            for file in files {
                vec.insert(file.uri(), file);
            }
        }

        model
    }

    /// Load all file from the given directory
    ///
    /// This can be used if there are already files present
    pub async fn load_directory(&self, directory: gio::File) -> anyhow::Result<()> {
        self.imp().directory.set(directory.clone()).unwrap();

        let monitor =
            directory.monitor_directory(gio::FileMonitorFlags::WATCH_MOVES, gio::Cancellable::NONE);
        match monitor {
            Ok(monitor) => {
                monitor.connect_changed(
                    glib::clone!(@weak self as obj => move |_monitor, file_a, file_b, event| {
                        obj.file_monitor_cb(event, file_a, file_b);
                    }),
                );
                self.imp().monitor.set(monitor).unwrap();
            }
            Err(err) => {
                log::info!("Cannot monitor directory: {err}");
            }
        }

        let new_files_result = gio::spawn_blocking(move || {
            let mut files = IndexMap::new();

            let enumerator = directory
                .enumerate_children(
                    &format!(
                        "{},{},{},{}",
                        gio::FILE_ATTRIBUTE_STANDARD_NAME,
                        gio::FILE_ATTRIBUTE_STANDARD_CONTENT_TYPE,
                        gio::FILE_ATTRIBUTE_STANDARD_FAST_CONTENT_TYPE,
                        gio::FILE_ATTRIBUTE_STANDARD_IS_HIDDEN,
                    ),
                    gio::FileQueryInfoFlags::NONE,
                    gio::Cancellable::NONE,
                )
                .context(gettext("Could not list other files in directory."))?;

            enumerator.for_each(|info| {
                if let Ok(info) = info {
                    // GVfs smb does not provide a CONTENT_TYPE if the content type is ambiguous.
                    // This happens for png/apng. Since we only need to know if something is
                    // probably an image, we can use the FAST_CONTENT_TYPE in these cases.
                    let content_type =
                        if info.has_attribute(gio::FILE_ATTRIBUTE_STANDARD_CONTENT_TYPE) {
                            info.content_type()
                        } else {
                            info.attribute_string(gio::FILE_ATTRIBUTE_STANDARD_FAST_CONTENT_TYPE)
                        };

                    if let Some(content_type) =
                        content_type.and_then(|x| gio::content_type_get_mime_type(&x))
                    {
                        // Filter out non-images types. The final decision if images are
                        // supported/kept will later be done by glycin when starting to load the
                        // images. Usually by inspecting the magic bytes.
                        if content_type.starts_with("image/") && !info.is_hidden() {
                            let file = directory.child(info.name());
                            files.insert(file.uri(), file);
                        }
                    }
                }
            });

            Ok::<_, anyhow::Error>(files)
        })
        .await;

        let Ok(new_files) = new_files_result else {
            log::debug!("Thread listing directory canceled.");
            return Ok(());
        };

        let mut new_files = new_files?;

        {
            // Here we use a nested scope so that the mutable borrow only lasts as long as
            // we need it

            let mut files = self.imp().files.borrow_mut();
            for (uri, file) in files.iter() {
                new_files.insert(uri.clone(), file.clone());
            }
            *files = new_files;
            // Then sort by name.
            Self::sort(&mut files);
        }

        Ok(())
    }

    pub fn directory(&self) -> Option<gio::File> {
        self.imp().directory.get().cloned()
    }

    pub fn index_of(&self, file: &gio::File) -> Option<usize> {
        self.imp().files.borrow().get_index_of(&file.uri())
    }

    pub fn n_files(&self) -> usize {
        self.imp().files.borrow().len()
    }

    pub fn contains(&self, file: &gio::File) -> bool {
        self.imp().files.borrow().contains_key(&file.uri())
    }

    pub fn before(&self, file: &gio::File) -> Option<gio::File> {
        let index = self.index_of(file)?;

        self.imp()
            .files
            .borrow()
            .get_index(index.checked_sub(1)?)
            .map(|x| x.1)
            .cloned()
    }

    pub fn after(&self, file: &gio::File) -> Option<gio::File> {
        let index = self.index_of(file)?;

        self.imp()
            .files
            .borrow()
            .get_index(index.checked_add(1)?)
            .map(|x| x.1)
            .cloned()
    }

    /// Returns `n` elements before and after given file
    pub fn files_around(&self, file: &gio::File, n: usize) -> IndexMap<GString, gio::File> {
        let Some(index) = self.index_of(file) else {
            log::error!("URI not in model: {}", file.uri());
            return IndexMap::new();
        };

        let reduce = if index < n { n - index } else { 0 };

        self.imp()
            .files
            .borrow()
            .iter()
            .skip(index.saturating_sub(n))
            .take(2 * n + 1 - reduce)
            .map(|(k, v)| (k.clone(), v.clone()))
            .collect()
    }

    /// Return first file
    pub fn first(&self) -> Option<gio::File> {
        self.imp().files.borrow().first().map(|x| x.1).cloned()
    }

    /// Returns last file
    pub fn last(&self) -> Option<gio::File> {
        self.imp().files.borrow().last().map(|x| x.1).cloned()
    }

    pub fn remove(&self, file: &gio::File) -> Option<gio::File> {
        self.imp().files.borrow_mut().shift_remove(&file.uri())
    }

    /// Currently sorts by name
    fn sort(files: &mut IndexMap<GString, gio::File>) {
        files.sort_by(|_, x, _, y| util::compare_by_name(&x.uri(), &y.uri()));
    }

    /// Determines if a file is added
    fn is_image(info: &gio::FileInfo) -> bool {
        info.content_type()
            .map(|t| t.to_string())
            .filter(|t| t.starts_with("image/"))
            .is_some()
    }

    fn is_image_file(file: &gio::File) -> bool {
        let Ok(info) =
            util::query_attributes(file, vec![gio::FILE_ATTRIBUTE_STANDARD_CONTENT_TYPE])
        else {
            log::warn!("Could not query file info: {}", file.uri());
            return false;
        };

        Self::is_image(&info)
    }

    /// Signal that notifies about added/removed files
    pub fn connect_changed(&self, f: impl Fn() + 'static) {
        self.connect_local("changed", false, move |_| {
            f();
            None
        });
    }

    fn file_monitor_cb(
        &self,
        event: gio::FileMonitorEvent,
        file_a: &gio::File,
        file_b: Option<&gio::File>,
    ) {
        let changed = match event {
            gio::FileMonitorEvent::Created
            | gio::FileMonitorEvent::MovedIn
            // Changing file content could theoretically make it an image
            // by adding a magic byte
            | gio::FileMonitorEvent::ChangesDoneHint
                if Self::is_image_file(file_a) =>
            {
                let mut files = self.imp().files.borrow_mut();
                let changed = files.insert(file_a.uri(),file_a.clone()).is_none();
                if changed {
                    Self::sort(&mut files);
                }
                changed
            }
            gio::FileMonitorEvent::Deleted | gio::FileMonitorEvent::MovedOut | gio::FileMonitorEvent::Unmounted => {
                let mut files = self.imp().files.borrow_mut();
                files.shift_remove(&file_a.uri()).is_some()
            }
            gio::FileMonitorEvent::Renamed => {
                if let Some(file_b) = file_b {
                    let mut changed = false;
                    {
                        let mut files = self.imp().files.borrow_mut();
                        changed |= files.shift_remove(&file_a.uri()).is_some();
                        if Self::is_image_file(file_b) {
                            changed |= files.insert(file_b.uri(), file_b.clone()).is_none();
                            if changed {
                                Self::sort(&mut files);
                            }
                        }
                    }
                    changed
                } else {
                    false
                }
            }
            _ => false,
        };

        if changed {
            self.emit_by_name::<()>("changed", &[]);
        }
    }
}