use std::io;
use std::sync::atomic::{self, AtomicBool};
use std::sync::Arc;
use std::time::SystemTime;

use helix_core::file_watcher::{EventType, FileSystemDidChange};
use helix_event::register_hook;
use helix_view::editor::Config;
use helix_view::events::ConfigDidChange;

use crate::job;

struct AutoReload {
    enable: AtomicBool,
    prompt_if_modified: AtomicBool,
}

impl AutoReload {
    pub fn refresh_config(&self, config: &Config) {
        self.enable
            .store(config.file_watcher.enable, atomic::Ordering::Relaxed);
        self.prompt_if_modified
            .store(config.file_watcher.enable, atomic::Ordering::Relaxed);
    }

    fn on_file_did_change(&self, event: &mut FileSystemDidChange) {
        if !self.enable.load(atomic::Ordering::Relaxed) {
            return;
        }
        let fs_events = event.fs_events.clone();
        if !fs_events
            .iter()
            .any(|event| event.ty == EventType::Modified)
        {
            return;
        }
        job::dispatch_blocking(move |editor, _| {
            let config = editor.config();
            let mut vcs_reload = false;
            for fs_event in &*fs_events {
                if fs_event.ty != EventType::Modified {
                    continue;
                }
                vcs_reload |= editor.diff_providers.needs_reload(fs_event);
                let Some(doc_id) = editor.document_id_by_path(fs_event.path.as_std_path()) else {
                    return;
                };
                let doc = doc_mut!(editor, &doc_id);
                let mtime = match doc.path().unwrap().metadata() {
                    Ok(meta) => meta.modified().unwrap_or(SystemTime::now()),
                    Err(err) if err.kind() == io::ErrorKind::NotFound => continue,
                    Err(_) => SystemTime::now(),
                };
                if mtime == doc.last_saved_time {
                    continue;
                }
                if doc.is_modified() {
                    let msg = format!(
                        "{} auto-reload failed due to unsaved changes, use :reload to refresh",
                        doc.relative_path().unwrap().display()
                    );
                    editor.set_warning(msg);
                } else {
                    let scrolloff = config.scrolloff;
                    let view = view_mut!(editor);
                    match doc.reload(view, &editor.diff_providers) {
                        Ok(_) => {
                            view.ensure_cursor_in_view(doc, scrolloff);
                            let msg = format!(
                                "{} auto-reload external changes",
                                doc.relative_path().unwrap().display()
                            );
                            editor.set_status(msg);
                        }
                        Err(err) => {
                            let doc = doc!(editor, &doc_id);
                            let msg = format!(
                                "{} auto-reload failed: {err}",
                                doc.relative_path().unwrap().display()
                            );
                            editor.set_error(msg);
                        }
                    }
                }
            }
            if vcs_reload {
                for doc in editor.documents.values_mut() {
                    let Some(path) = doc.path() else {
                        continue;
                    };
                    match editor.diff_providers.get_diff_base(path) {
                        Some(diff_base) => doc.set_diff_base(diff_base),
                        None => doc.diff_handle = None,
                    }
                }
            }
        });
    }
}

pub(super) fn register_hooks(config: &Config) {
    let handler = Arc::new(AutoReload {
        enable: config.auto_reload.enable.into(),
        prompt_if_modified: config.auto_reload.prompt_if_modified.into(),
    });
    let handler_ = handler.clone();
    register_hook!(move |event: &mut ConfigDidChange<'_>| {
        // when a document is initially opened, request colors for it
        handler_.refresh_config(event.new);
        Ok(())
    });
    register_hook!(move |event: &mut FileSystemDidChange| {
        // when a document is initially opened, request colors for it
        handler.on_file_did_change(event);
        Ok(())
    });
}