//! Reset all data: wipe everything the app owns, then start blank (the first-run wizard shows again).
//!
//! The running app holds `voiced.db` open (WAL) and serves files out of `assets/`, `archive/` and `fonts/`,
//! so deleting them live is unsafe. Like a restore, a reset has two phases:
//!
//! 1. `reset_all_data` (`stage_wipe_impl`) writes `<data>/pending_wipe.json` and touches nothing else.
//! 2. `apply_pending_wipe` runs in `init_state` BEFORE a staged restore is applied and before the database is
//!    opened. It deletes exactly the names in `OWNED_DB_FILES` and `OWNED_DIRS`, never anything else in the
//!    data directories (on Linux both roots are the same folder and may hold unrelated files), and removes the
//!    marker last, so a failed wipe is retried on the next start. The frontend restarts the app after staging.
//!
//! This also deletes the backups (`<data>/backups`, including pre-restore safety copies and pre-migration
//! copies); that is the point of a reset.
use super::backup::{DataDirs, DB_ENTRY, LAST_RESTORE_NAME, MARKER_NAME, ROOTS, STAGING_NAME};
use super::raw::write_atomic;
use crate::AppState;
use std::fs;
use std::path::Path;
use tauri::State;

const WIPE_MARKER_NAME: &str = "pending_wipe.json";
/// The database and its SQLite sidecars, in the data dir.
const OWNED_DB_FILES: [&str; 4] = [
    DB_ENTRY,
    "voiced.db-wal",
    "voiced.db-shm",
    "voiced.db-journal",
];
/// Marker files of the restore mechanism, in the data dir.
const OWNED_MARKERS: [&str; 2] = [MARKER_NAME, LAST_RESTORE_NAME];

#[derive(Debug, PartialEq, Eq)]
pub enum WipeOutcome {
    NothingPending,
    Wiped,
    /// Something could not be deleted; the marker is kept so the next start retries.
    Failed {
        message: String,
    },
}

fn marker(dirs: &DataDirs) -> std::path::PathBuf {
    dirs.data.join(WIPE_MARKER_NAME)
}

/// Remove a file or directory tree if it exists. A symlink is unlinked, never followed.
fn remove_if_exists(path: &Path) -> Result<(), String> {
    let meta = match fs::symlink_metadata(path) {
        Ok(m) => m,
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(()),
        Err(e) => return Err(format!("Could not delete {}: {e}", path.display())),
    };
    let result = if meta.is_dir() {
        fs::remove_dir_all(path)
    } else {
        fs::remove_file(path)
    };
    result.map_err(|e| format!("Could not delete {}: {e}", path.display()))
}

/// Record that the next start must wipe everything. The live data is not touched.
pub fn stage_wipe_impl(dirs: &DataDirs) -> Result<(), String> {
    write_atomic(&marker(dirs), b"{}")
}

/// Call after the data directories exist and before anything else (restore, database) uses them.
pub fn apply_pending_wipe(dirs: &DataDirs) -> WipeOutcome {
    if fs::symlink_metadata(marker(dirs)).is_err() {
        return WipeOutcome::NothingPending;
    }
    let mut targets = Vec::new();
    // Order matters: the database goes first so a half-finished wipe never leaves data with no settings row.
    for name in OWNED_DB_FILES {
        targets.push(dirs.data.join(name));
    }
    targets.push(dirs.backups());
    for root in ROOTS {
        targets.push(dirs.root_dir(root));
    }
    for name in OWNED_MARKERS {
        targets.push(dirs.data.join(name));
    }
    targets.push(dirs.data.join(STAGING_NAME));
    targets.push(dirs.local.join(STAGING_NAME));

    let errors: Vec<String> = targets
        .iter()
        .filter_map(|p| remove_if_exists(p).err())
        .collect();
    if !errors.is_empty() {
        return WipeOutcome::Failed {
            message: errors.join("; "),
        };
    }
    match remove_if_exists(&marker(dirs)) {
        Ok(()) => WipeOutcome::Wiped,
        Err(message) => WipeOutcome::Failed { message },
    }
}

/// Phase one of a reset: stage the wipe. The app must be restarted to carry it out.
#[tauri::command]
pub fn reset_all_data(state: State<AppState>) -> Result<(), String> {
    stage_wipe_impl(&DataDirs::new(&state.data_dir, &state.local_data_dir))
}

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

    fn populate(dirs: &DataDirs) {
        for name in OWNED_DB_FILES.iter().chain(OWNED_MARKERS.iter()) {
            fs::write(dirs.data.join(name), b"x").unwrap();
        }
        fs::create_dir_all(dirs.backups().join("auto")).unwrap();
        fs::write(
            dirs.backups().join("auto").join("voiced-auto-20260101.zip"),
            b"x",
        )
        .unwrap();
        for root in ROOTS {
            fs::create_dir_all(dirs.root_dir(root)).unwrap();
            fs::write(dirs.root_dir(root).join("f.bin"), b"x").unwrap();
        }
        for staging in [dirs.data.join(STAGING_NAME), dirs.local.join(STAGING_NAME)] {
            fs::create_dir_all(&staging).unwrap();
            fs::write(staging.join("manifest.json"), b"x").unwrap();
        }
        fs::write(dirs.data.join("unrelated.txt"), b"keep").unwrap();
        fs::create_dir_all(dirs.data.join("other")).unwrap();
        fs::write(dirs.data.join("other").join("keep.txt"), b"keep").unwrap();
    }

    fn assert_wiped(dirs: &DataDirs) {
        for name in OWNED_DB_FILES.iter().chain(OWNED_MARKERS.iter()) {
            assert!(!dirs.data.join(name).exists(), "{name}");
        }
        assert!(!dirs.backups().exists());
        for root in ROOTS {
            assert!(!dirs.root_dir(root).exists(), "{root}");
        }
        assert!(!dirs.data.join(STAGING_NAME).exists());
        assert!(!dirs.local.join(STAGING_NAME).exists());
        assert!(!marker(dirs).exists());
    }

    fn assert_unrelated_kept(dirs: &DataDirs) {
        assert_eq!(fs::read(dirs.data.join("unrelated.txt")).unwrap(), b"keep");
        assert!(dirs.data.join("other").join("keep.txt").exists());
    }

    #[test]
    fn nothing_staged_means_nothing_is_deleted() {
        let tmp = tempdir().unwrap();
        let dirs = DataDirs::new(tmp.path(), tmp.path());
        populate(&dirs);
        assert_eq!(apply_pending_wipe(&dirs), WipeOutcome::NothingPending);
        assert!(dirs.db().exists());
        assert!(dirs.backups().exists());
    }

    #[test]
    fn staging_alone_does_not_touch_live_data() {
        let tmp = tempdir().unwrap();
        let dirs = DataDirs::new(tmp.path(), tmp.path());
        populate(&dirs);
        stage_wipe_impl(&dirs).unwrap();
        assert!(marker(&dirs).exists());
        assert!(dirs.db().exists());
        assert!(dirs.root_dir("archive").join("f.bin").exists());
    }

    #[test]
    fn wipe_removes_owned_data_and_keeps_unrelated_files() {
        let tmp = tempdir().unwrap();
        let dirs = DataDirs::new(tmp.path(), tmp.path());
        populate(&dirs);
        stage_wipe_impl(&dirs).unwrap();
        assert_eq!(apply_pending_wipe(&dirs), WipeOutcome::Wiped);
        assert_wiped(&dirs);
        assert_unrelated_kept(&dirs);
        assert!(dirs.data.exists());
    }

    #[test]
    fn wipe_handles_separate_data_and_local_roots() {
        let tmp = tempdir().unwrap();
        let data = tmp.path().join("roaming");
        let local = tmp.path().join("local");
        fs::create_dir_all(&data).unwrap();
        fs::create_dir_all(&local).unwrap();
        let dirs = DataDirs::new(&data, &local);
        populate(&dirs);
        fs::write(local.join("unrelated-local.txt"), b"keep").unwrap();
        stage_wipe_impl(&dirs).unwrap();
        assert_eq!(apply_pending_wipe(&dirs), WipeOutcome::Wiped);
        assert_wiped(&dirs);
        assert_unrelated_kept(&dirs);
        assert!(local.join("unrelated-local.txt").exists());
    }

    #[test]
    fn wipe_is_idempotent_when_things_are_missing() {
        let tmp = tempdir().unwrap();
        let dirs = DataDirs::new(tmp.path(), tmp.path());
        stage_wipe_impl(&dirs).unwrap();
        assert_eq!(apply_pending_wipe(&dirs), WipeOutcome::Wiped);
        assert_eq!(apply_pending_wipe(&dirs), WipeOutcome::NothingPending);
        populate(&dirs);
        stage_wipe_impl(&dirs).unwrap();
        assert_eq!(apply_pending_wipe(&dirs), WipeOutcome::Wiped);
        stage_wipe_impl(&dirs).unwrap();
        assert_eq!(apply_pending_wipe(&dirs), WipeOutcome::Wiped);
        assert_wiped(&dirs);
    }

    #[cfg(unix)]
    #[test]
    fn a_symlinked_root_is_unlinked_not_followed() {
        let tmp = tempdir().unwrap();
        let outside = tempdir().unwrap();
        fs::write(outside.path().join("precious.txt"), b"keep").unwrap();
        let dirs = DataDirs::new(tmp.path(), tmp.path());
        std::os::unix::fs::symlink(outside.path(), dirs.root_dir("archive")).unwrap();
        stage_wipe_impl(&dirs).unwrap();
        assert_eq!(apply_pending_wipe(&dirs), WipeOutcome::Wiped);
        assert!(!dirs.root_dir("archive").exists());
        assert!(outside.path().join("precious.txt").exists());
    }
}