Triple-C/app/src-tauri/src/file_viewer/registry.rs

//! Which viewer window is looking at what.
//!
//! Managed with `app.manage(ViewerRegistry::default())` rather than as a field on
//! `AppState`, like the browser view keeps its own state. A label is reserved *before*
//! the window is built so two concurrent clicks cannot both pass the cap check.

use std::collections::HashMap;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Mutex;

use serde::{Deserialize, Serialize};

use super::{MAX_VIEWER_WINDOWS, VIEWER_LABEL_PREFIX};

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq, Default)]
pub struct Location {
    pub line: Option<u32>,
    pub col: Option<u32>,
    pub end_line: Option<u32>,
}

#[derive(Clone, Debug, Serialize, PartialEq, Eq)]
#[serde(tag = "kind", rename_all = "snake_case")]
pub enum ViewerTargetState {
    Resolved { container_path: String },
    Choose { candidates: Vec<String> },
    NotFound { tried: Vec<String> },
}

#[derive(Clone, Debug, Serialize, PartialEq, Eq)]
pub struct ViewerTarget {
    pub project_id: String,
    pub project_name: String,
    pub raw_path: String,
    pub state: ViewerTargetState,
    pub initial: Location,
}

#[derive(Default)]
pub struct ViewerRegistry {
    entries: Mutex<HashMap<String, ViewerTarget>>,
    next: AtomicU64,
}

impl ViewerRegistry {
    fn lock(&self) -> std::sync::MutexGuard<'_, HashMap<String, ViewerTarget>> {
        self.entries.lock().unwrap_or_else(|e| e.into_inner())
    }

    pub fn reserve(&self, target: ViewerTarget) -> Result<String, String> {
        let mut entries = self.lock();
        if entries.len() >= MAX_VIEWER_WINDOWS {
            return Err(format!(
                "{} file windows are already open — close one before opening another.",
                MAX_VIEWER_WINDOWS
            ));
        }
        let n = self.next.fetch_add(1, Ordering::SeqCst) + 1;
        let label = format!("{}{}", VIEWER_LABEL_PREFIX, n);
        entries.insert(label.clone(), target);
        Ok(label)
    }

    pub fn get(&self, label: &str) -> Option<ViewerTarget> {
        self.lock().get(label).cloned()
    }

    pub fn set_state(&self, label: &str, state: ViewerTargetState) -> Result<ViewerTarget, String> {
        let mut entries = self.lock();
        let entry = entries
            .get_mut(label)
            .ok_or_else(|| "This file window is no longer registered.".to_string())?;
        entry.state = state;
        Ok(entry.clone())
    }

    pub fn remove(&self, label: &str) {
        self.lock().remove(label);
    }

    pub fn find_open(&self, project_id: &str, container_path: &str) -> Option<String> {
        self.lock()
            .iter()
            .find(|(_, t)| {
                t.project_id == project_id
                    && matches!(&t.state, ViewerTargetState::Resolved { container_path: p } if p == container_path)
            })
            .map(|(label, _)| label.clone())
    }

    pub fn len(&self) -> usize {
        self.lock().len()
    }

    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn target(project: &str, path: &str) -> ViewerTarget {
        ViewerTarget {
            project_id: project.into(),
            project_name: "Demo".into(),
            raw_path: path.into(),
            state: ViewerTargetState::Resolved { container_path: path.into() },
            initial: Location { line: Some(3), col: None, end_line: None },
        }
    }

    #[test]
    fn labels_are_sequential_and_never_reused() {
        let r = ViewerRegistry::default();
        let a = r.reserve(target("p", "/workspace/a")).unwrap();
        let b = r.reserve(target("p", "/workspace/b")).unwrap();
        assert_eq!(a, "file-viewer-1");
        assert_eq!(b, "file-viewer-2");
        r.remove(&a);
        let c = r.reserve(target("p", "/workspace/c")).unwrap();
        assert_eq!(c, "file-viewer-3");
        assert_eq!(r.len(), 2);
    }

    #[test]
    fn the_cap_refuses_the_twenty_first_window() {
        let r = ViewerRegistry::default();
        for i in 0..MAX_VIEWER_WINDOWS {
            r.reserve(target("p", &format!("/workspace/{}", i))).unwrap();
        }
        let err = r.reserve(target("p", "/workspace/one-more")).unwrap_err();
        assert!(err.contains("20"), "{}", err);
        assert_eq!(r.len(), MAX_VIEWER_WINDOWS);
    }

    #[test]
    fn an_open_resolved_file_is_found_by_project_and_path() {
        let r = ViewerRegistry::default();
        let label = r.reserve(target("p", "/workspace/a")).unwrap();
        assert_eq!(r.find_open("p", "/workspace/a"), Some(label.clone()));
        assert_eq!(r.find_open("other", "/workspace/a"), None);
        // A window still choosing is not "open on" any path.
        r.set_state(&label, ViewerTargetState::Choose { candidates: vec!["/workspace/a".into()] }).unwrap();
        assert_eq!(r.find_open("p", "/workspace/a"), None);
        r.remove(&label);
        assert_eq!(r.get(&label), None);
    }

    #[test]
    fn set_state_on_an_unknown_label_is_an_error() {
        let r = ViewerRegistry::default();
        assert!(r.set_state("file-viewer-9", ViewerTargetState::NotFound { tried: vec![] }).is_err());
    }

    #[test]
    fn target_state_serialises_with_a_kind_tag() {
        let s = serde_json::to_string(&ViewerTargetState::NotFound { tried: vec!["/x".into()] }).unwrap();
        assert_eq!(s, r#"{"kind":"not_found","tried":["/x"]}"#);
    }
}