//! OS-conventional paths for client-side storage.

use std::path::PathBuf;

use directories::ProjectDirs;
use thiserror::Error;

#[derive(Debug, Error)]
pub enum PathError {
    #[error("cannot determine OS data directory (is $HOME set?)")]
    NoDataDir,
}

/// Directory where recordings wait for upload. Persists across app
/// restarts and crashes.
///   Linux:   `~/.local/share/doctate/pending/`
///   Windows: `%LOCALAPPDATA%\doctate\pending\`
///   macOS:   `~/Library/Application Support/doctate/pending/`
pub fn pending_dir() -> Result<PathBuf, PathError> {
    ProjectDirs::from("", "", "doctate")
        .map(|dirs| dirs.data_local_dir().join("pending"))
        .ok_or(PathError::NoDataDir)
}

/// Directory holding one JSON marker per known case (locally created
/// and/or server-synced). Persists across app restarts.
///   Linux:   `~/.local/share/doctate/cases/`
pub fn cases_dir() -> Result<PathBuf, PathError> {
    ProjectDirs::from("", "", "doctate")
        .map(|dirs| dirs.data_local_dir().join("cases"))
        .ok_or(PathError::NoDataDir)
}

/// File path for the last-successful `/api/oneliners` response. Feeds
/// the UI at cold start before the first live poll completes.
pub fn snapshot_cache_path() -> Result<PathBuf, PathError> {
    ProjectDirs::from("", "", "doctate")
        .map(|dirs| dirs.data_local_dir().join("oneliners_cache.json"))
        .ok_or(PathError::NoDataDir)
}

/// File path for the single-instance advisory lock. Held by the running
/// process for its entire lifetime; a second launch attempting to lock
/// the same file gets `WouldBlock` and exits cleanly.
pub fn lock_file_path() -> Result<PathBuf, PathError> {
    ProjectDirs::from("", "", "doctate")
        .map(|dirs| dirs.data_local_dir().join("client.lock"))
        .ok_or(PathError::NoDataDir)
}